Sero-prevalence of peste des petits ruminants virus-specific antibodies in Sudanese sheep and goats before and after vaccination

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Animals were kept healthy under field conditions, in four states; Blue Nile (n = 250), North Kordofan (n = 189), South Darfur (n = 225) and the Northern State (n = 191). Before vaccination, sero-prevalence of PPRV antibodies was 54.6% (53.2%-56% 95% CI); high (64.8%-76.4% 95% CI) in South Eastern Sudan (Blue Nile), medium (50.5%-61.9% 95% CI) in Western Sudan (North Kordofan and South Darfur) and low (28.6%-35.2% 95% C.I) in Northern Sudan (Northern State). In high-risk areas (high sero-prevalence), Blue Nile (70.4%) and North Kordofan (57.7%), middle age groups (7–12 and 13–18 months) were identified as high-risk age. Middle age groups showed lower sero-prevalence than preceding (3–6 months) and subsequent (> 18 months) age groups while the risk of exposure increased with age. Current and previous findings suggested a transmission pathway of PPRV involving the South Eastern border (Blue Nile) and neighbouring Central Sudan to North Kordofan. One month after vaccination 88.4% (343/388) of sero-negative animals were sero-converted suggesting the efficacy of the locally produced Nigeria 75/1 vaccine. Had only the high- risk age group (7–18 months) was vaccinated, the overall population immunity (OPI) in high-risk areas (Blue Nile and North Kordofan) would have surpassed the threshold of 70% indicated for blocking PPRV transmission. However, lower vaccination coverage is expected in wider vaccination programme. findings justified targeting PPR control in Sudan, primarily, by vaccination of high-risk age groups in high-risk areas. ELISA PPR Sero-conversion Sero-prevalence Small ruminants Vaccine Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Peste des petits ruminants (PPR) is an important transboundary viral disease of small ruminants [ 1 ]. It primarily affects sheep and goats, the main target species, and occasionally some other artiodactyls including camels [ 2 , 3 ] and small ruminant wildlife [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Cattle and buffalo are considered susceptible, particularly to subclinical infection [ 1 ]. Clinical PPR in sheep and goats is usually acute; generally, more severe in the latter (goat plaque); characterized by pyrexia, oculo-nasal discharge, stomatitis, diarrhoea, pneumonia and very high morbidity (100%) and mortality (50%-80%) in naive population [ 1 , 8 , 12 13 , 14 ]. It is caused by a member of the genus Morbillivirus in the family Paramyxoviridae [ 15 ], presently known as Small Ruminant Morbillivirus (SRMV) [ 1 ]. It is a single stranded (-) sense RNA virus. The viral genome encodes six structural proteins: the nucleocapsid (N), phosphoprotein (P), matrix (M), fusion (F), hemagglutinin (H) and polymerase (L) proteins and two non-structural proteins, C and V (16). Based on the partial nucleotide sequence data of the N [ 17 ] and F [ 18 ] genes, PPR virus (PPRV) isolates can be classified into four genetically distinct lineages: I, II, III and IV. Geographic specificity of these four lineages has been described what, consequently, founded the emergence of molecular epidemiology of PPRV [ 19 , 20 , 21 , 22 , 23 ]. The family Paramyxoviridae is known for two members that cause two of the most economically significant diseases; rinderpest virus (RPV) and Newcastle disease virus (NDV). Similarly, PPRV produces a global cost of US $ 2.1 billion and troubles the livelihoods of some 900 million poor and low-income people [ 24 , 25 ] in developing countries in Africa (apart from most of South Africa), Middle East and West and South Asia [ 19 ]. Moreover, PPRV poses threats to wildlife conservation [ 10 ] and has the capability to spread well beyond its historical range into East Asia and the European part of Turkey [ 19 ] to threaten the European Union (EU). To alleviate poverty in many developing countries and to eliminate risks associated with PPRV circulation, the FAO and WOAH, based on the successful eradication of the related RPV, targeted PPRV eradication by 2030 [ 24 ]. Like RPV, PPRV is monotypic; available vaccines can induce immunity against all known genotypes i.e., it is of one serotype, and ensuing immunity, following vaccination or infection, is lifelong. Additionally, like RP, the virus does not persist in the environment, and infection primarily requires contact and, moreover, results in no carrier state [ 25 ]. However, since sheep and goats compared to cattle are more numerous, reproduce more rapidly and having less value per head, the vaccination strategy for PPR is likely to pose more challenges and to be more expensive than that against RP [ 25 ]. Therefore, to develop an appropriate vaccination strategy, the PPR Global Eradication Programme (PPR GER) requires countries to gain clear insight into PPR epidemiology and update the field situation annually to identify hot spots, transmission pathways and populations critical for virus maintenance [ 24 ]. Sudan is a vast country in the upper western corner of East Africa that harbors more than seventy million sheep and goats. Peste des petits ruminants were identified in Sudan since 1972, when were misdiagnosed as RP [ 26 ]. Subsequently, it was reported in the country in many instances and in different animal species [ 3 , 11 , 27 , 28 , 29 , 30 ]. Early Sudanese isolates of PPRV were of lineage III, and later isolates reflected a predominance of lineage IV [ 11 , 23 , 28 , 30 ] while the main target species for infection in Sudan have remained sheep and goats. Consistently, the sero-prevalence of PPR antibodies was higher (mostly in the approximate range of 50%-70%) in sheep and goats than in other ruminant species [ 31 , 27 , 32 ]. Sheep and goat populations from, almost, all investigated Sudanese states have shown serological evidence (approximately 30%-75%) of infection [ 27 , 33 , 34 , 35 ]. The heterologous RP vaccine and, subsequently, the homologous PPR vaccine have been used to control infections in sheep and goats in Sudan. Saeed et al.2010 [ 27 ] and Shuaib et al.2014 [ 34 ] observed that despite the lack of so-called Differentiation of Infected and Vaccinated Animals (DIVA) capability, the numbers of vaccinated sheep and goats were too small to affect interpretations of serological surveillance. Local production of a homologous live attenuated vaccine (Nigeria 75/1) against PPR [ 36 ] was established in Sudan in 2004 [ 37 ]. However, a well-organized vaccination programme against PPR has not yet been developed. The objective of the present work is to enhance the latter endeavor. Given the large number of sheep and goats in Sudan, it meant to identify geographical areas in Sudan and age groups within sheep and goat populations that are crucial for PPRV circulation and maintenance. Prioritization of the vaccination programme based on such information is expected to enhance control. Second, the study aimed to assess sero-conversion following the application of the locally produced PPR vaccine (Nigeria 75/1) under field conditions. Materials and Methods Study area: The study area included four states: the Blue Nile, North Kordofan, South Darfur and the Northern State (Fig. 1 ). The first three states are breeding areas, while the Northern State is an important part of a projected disease-free zone. The latter state represents the geographical cluster of northern Sudan, which falls exclusively in the desert ecological zone. The remaining 3 states represent two important geographical clusters [ 38 ]: the Western cluster (North Kordofan and South Darfur) and the South Eastern cluster (the Blue Nile state). The Western cluster is the main pastoral area in the country and falls for the most part in the low-rainfall savannah, addition to small strips of desert and semidesert in the North. The south-eastern cluster includes the Nile valley from the South and South-east up to Khartoum state and falls exclusively, apart from Khartoum, in the low-rainfall savannah. The South Eastern cluster is distinguished by large urban centres along the Blue and White Nile and consequent excessive animal movement related to national trade. Three of the surveyed states (Blue Nile, the Northern State and South Darfur) are border areas, while North Kordofan is a central state (Fig. 1 ). North Kordofan State constitutes the western flank of the southeastern cluster, with an area of 185,302 km2 at the centre of Sudan and with populations of 2.7 million goats and 4.2 million sheep [ 39 ]. The Blue Nile State has the highest animal density in the country, with populations of 480718 goats and 4.1 million sheep and an area of 45,844 km2 bordering Ethiopia and South Sudan [ 39 ]. South Darfur is situated far from the Nile valley, bordering the Central African Republic (CAR) and South Sudan, with an area of 81,000 km2 and 1.7 million goats and 2.2 million sheep [ 39 ]. The Northern State has a large area of 348,765 km² and relatively low estimates of animal population of 1.2 million goats and one million sheep [ 39 ]. It contains border areas with Egypt and Libya. Serum samples: Sera were collected from unvaccinated small ruminant flocks (sheep and goats) in the four states in February 2022. The selected animals were more than three months old and apparently healthy. Bled animals, including 653 sheep and 172 goats, were ear-tagged, vaccinated with a locally produced PPR vaccine (Nigeria 75/1), and bled again one month later. During the study period, the animals were inspected for PPR-like clinical signs. In the first round of sample collection, simple random sampling (SRS) was used to select animals from an available sampling frame of 12 geographical districts or localities (sampling units), 3 in each state (Table 1 ). The approximate sample size required to estimate the prevalence in an infinite population (large) in each sampling unit was calculated using the following formula [ 40 ]: Where n = the required sample size; P exp = expected prevalence; d = desired absolute precision; 1.645 = appropriate multiplier for the required level of confidence According to previous studies, an expected prevalence (P) of 70% was used. The desired absolute precision of 10% was applied at a level of confidence of 90%. Accordingly, a sample size of 58 sera in each sampling unit was targeted. Only in two sampling units that have not been achieved, while in South Darfur and Blue Nile states, where a larger population size and more dense distribution prevail, a larger sample size was achieved (Table 1 ). In each sampling unit, at least eight to ten sampling epi-units (herds or collection sites) were visited to achieve a minimum of 25 epi-units in each surveyed state to stick to statistical theory regarding unbiased parameter estimates [ 41 ]. Table 1 Sample frame and sample size State District (sampling unit) No. of samples Total no. of samples Blue Nile Damazin 84 250 Rosayris 67 Tadamon 99 South Darfur Baleel 58 225 Kass 99 Kateela 68 North Kordofan Bara 29 189 El-Rahd and Um Rwaba 101 Shaekan 59 Northern state Dongla 92 191 Elburgeeg 55 Marawi 44 ELISA method Sera were tested using a commercial competitive ELISA (cELISA) kit (ID screen PPR competition, IDvet Genetics, Grabels, France) according to the manufacturer’s instructions. The employed ELISA is a monoclonal antibody-based cELISA directed against the N protein of PPRV [ 42 ]. Sera from different states of different age and sex groups were tested simultaneously. The optical density (OD) was read using an ELEX808 microplate photometer at a wavelength of 450 nm. The results are expressed as the sample positivity percentage (S/N %). Samples were considered positive if the S/N % were ≤ 50%, negative if ≥ 60% or doubtful if it was between 50 and 60%. Statistical analysis: Before and after vaccination, the sero-prevalence of PPR-specific antibodies in each population or sub-population was calculated by dividing the number of positive reactors identified by the cELISA by the number of sera tested in that population or sub-population, and then multiplying the result by 100. Negative and doubtful reactors in pre-vaccination sera (before vaccination) in each population or sub-population were identified and used to calculate the sero-conversion rate by the vaccine. The conversion rate was calculated by dividing the number of positive reactors identified by the cELISA one month after vaccination by the number of negative and doubtful reactors in pre-vaccination sera in that population or sub-population, then multiplying the result by 100. Prevalence and conversion rates in different populations or sub-populations were compared by determining the 95% confidence intervals (CIs) from a simple random sample based on the normal approximation to the binomial distribution using the formula: P ± 1.96√p(1-p ) /n [ 40 ]. Where P is the estimated prevalence, n is the number of samples tested and 1.96 is the appropriate multiplier for the selected level of confidence. When CI values did not overlap, results were statistically significantly different [ 43 ]. For overlapping CI, p-values were calculated using the chi-square test available at the Statistical Packages for Social Sciences (SPSS) at www.sociostatistics.com (44); the results were significantly different if p < 0.05. Results Sero-prevalence of PPRV-specific antibodies in sheep and goats before vaccination The prevalence’s of PPRV-specific antibodies was 54.6% in the whole test group (n = 855), 53.9% in sheep (n = 683), and 57.6% in goats (n = 172). The results were statistically similar (P = .3864) for sheep (50.2%-57.6% 95% CI) and goats (50.2%-65% 95% CI) but were dissimilar in different states. In different states, three statistically distinct levels were detected: highest in the Blue Nile, the medium in North Kordofan and South Darfur and the lowest in the Northern State (Table 2 ). In the Blue Nile and North Kordofan (n = 6), where higher sero-prevalence’s rate prevailed, districts consistently had higher sero-prevalence rates than in districts in South Darfur and the northern state (n = 6); apart from one district, Kateela, in South Darfur (Fig. 2 ). In 3 states (Blue Nile, North Kordofan and the Northern State), detected sero-prevalence’s in districts (Fig. 2 ) were proportional to the estimated general sero-prevalence in the respective state (Table 2 ). In the 4th state (South Darfur), two districts showed similar sero-prevalence’s to those in districts in the Northern state (lower level), while the third district showed the highest sero-prevalence detected in this work before vaccination (85.3%). Table 2 Sero-prevalence of PPRV-specific antibodies in unvaccinated Sudanese sheep and goats in different states. State No. tested No. positive Estimated sero-prevalence 95% CI* Blue Nile 250 176 70.4% 64.76%-76.4% North Kordofan* 189 109 57.7% 54.11%-61.92% South Darfur* 225 121 53.8% 50.48%-57.12% Northern State 191 61 31.9% 28.58%-35.22% Total 855 467 54.6% 53.19%-56.01% *p value = .427 Before vaccination, sero-prevalence’s of PPRV-specific antibodies were found to be generally higher in old age groups (> 12 months) and females than in young age groups (˂ 12 months) and males (Tables 3 and 6 ). Differences in sero-prevalence’s between the old and young age groups were statistically significant at the high levels of sero-prevalence in the Blue Nile and North Kordofan states but were not at the lower levels of sero-prevalence in South Darfur and the Northern State (Table 4 ). Apart from South Darfur state, sero-prevalence in the oldest age group (> 18 month) in all states was higher than that in other age groups (Table 5 ). In South Darfur, sero-prevalence in the oldest age group (> 18 months) was lower than that in the 7–12 months and that in the 13–18 months groups (Table 5 ). Interestingly, in the whole test group (Table 3 ), sero-prevalence in the youngest age group (3–6 months) was slightly higher than that in the 7–12 age group and statistically similar (P value = .05059) to that in the oldest age group (> 18 months). Table 3 Sero-prevalence of PPRV antibodies in different age groups of unvaccinated Sudanese sheep and goats Age group ˂ 12 month > 12 month 3–6 month 7–12 moth Whole group 13–18 month > 18 month Whole group Estimated sero-prevalence (28/61) 45.9% (79/189) 41.8% (107/250) 42.8 (44/68) 64.7% (316/536) 59% (360/604) 59.6% 95% CI 33.58%-58.22% 34.82%-48.78% 36.7%-48.9% 51.11%-75.49% 54.86%-63.14% 55.74%-63.46% Sero-prevalence’s in the old age groups did not overlap with those of the young age groups apart from that of the youngest age group (3–6 month) which was statistically similar (P value = .05059) to that of the oldest age group (> 18 month). Table 4 Comparison of sero-prevalence of PPRV antibodies between young (3–12 month) and old (> 12 month) unvaccinated sheep and goats in different states (dissimilar levels of infection) Age groups State 3–12 month > 12 month Blue Nile [95% CI] 50.7% (37/73) [39.24%-62.16%] 78.5% (139/177) [72.47%-84.53%] North Kordofan [95% CI] 28.9% (15/52) [16.59%-41.21%] 68.6% (94/137) [60.84%-76.36%] South Darfur [95% CI] 51.8% (44/85) [41.2%-62.4%] 55% (77/140) [46.75%-63.25%] Northern State [95% CI] 27.5% (11/40) [13.68%-41.32%] 33.3% (50/150) [25.75%-40.85%] Table 5 Comparison of sero-prevalence of PPRV antibodies between different age groups of unvaccinated sheep and goats in different states (dissimilar levels of infection) Age groups State 3–12 month > 12 month 3–6 month 7–12 month 13–18 month > 18 month Blue Nile (5/9) 55.6% (32/64) 50% (29/39) 74.4% (110/138) 79.7% North Kordofan (3/7) 42.9% (12/45) 26.7% (8/14) 57.1% (86/123) 69.9% South Darfur (20/44) 45.5% (24/41) 58.5% (6/8) 75% (71/132) 53.8% Northern State (0/1) 0.0% (11/39) 28.2% (1/7) 14.3% (49/143) 34.3% Table 6 Sero-prevalence of PPRV-specific antibodies in male and female groups of Sudanese sheep and goats before vaccination Sex Male Female Estimated sero-prevalence (90/202) 44.6% (377/653) 57.7% 95% CI 37.8%-51.4% 53.9%-61.5% Performance of the PPR vaccine: The vaccine was found to be capable of converting 88.4% of negative (and doubtful) sera to positive (Table 7 ). The conversion rate of negative sera was around 90% or above in all states except in the Northern State; it was 76% (Table 7 ). It was 100% in 2/12 districts, 90% or above in 8/12 districts, above 85% in 11/12 districts and merely in one district (Elburgeeg) in the Northern state it decreased to 58% (Fig. 3 ). At Elburgeeg, the conversion rate of negative sera [58% (29/50)] was significantly lower (p = .00001) than that at other districts [92.9% (314/338)]. Detected sero-prevalence’s of PPRV-specific antibodies in different states after vaccination followed the detected conversion rates; it was above 90% in three states (Blue Nile, North Kordofan and South Darfur) and 84.3% in the Northern state (Fig. 4 ). In the whole test group, it reached (795/855) 93% (91.3%-94.7% 95% CI). In the second round of ELISA after vaccination, 15/467 sera (3.2%) did not reproduce the positive result and delivered a doubtful or negative result. Accordingly, the range of differences between states (Table 2 ) has been largely diminished; from 31.9%-70.4% (Table 2 ) to 84.3%-98.4% (Fig. 4 ) while differences between age groups have completely disappeared, showing overlapping 95% CI. and > 0.05 P values (Table 8 ). The youngest age group (3–6 months), unlike before vaccination, showed, among the different age groups, the least sero-prevalence. Sero-prevalence in male and female groups remained significantly different after vaccination (Table 9 ). Had vaccination against PPRV been limited to the 7–18 months old animals, post-vaccination sero-prevalence would have reached 87.2%, 75.5%, 62.2% and 44.5% in Blue Nile, North Kordofan, South Darfur and the Northern State (Fig. 4 ). Neither were PPR-like clinical signs observed nor reported during the study period. No discrepancy was detected following the serological testing. Table 7 Sero-conversion of negative (and doubtful) sheep and goats’ sera one month following PPR vaccination: State No. -ve No. +ve Detected sero-conversion Blue Nile* 74 73 (73/74) 98.6% North Kordofan 80 71 (71/80) 88.8% South Darfur** 104 99 (99/104) 95.2% Northern State 130 100 (100/130) 76.9% Total 388 343 (343/388) 88.4% Table 8 Sero-prevalence of PPRV-specific antibodies in different age groups of Sudanese sheep and goats one month after PPR vaccination Age group Less than 12 month More than 12 month 3–6 month 7–12 moth Whole group 13–18 month > 18 month Whole group Estimated sero-prevalence (53/61) 86.9% (174/189) 92.1% (227/250) 90.8% 66/68 97.1% 500/536 93.3% 566/604 93.7% 95% CI 78.4-%95.4% 88.3%-95.9% 87.2%-94.4% 93.1%-100% 91.1%-95.5% 91.7%-95.7% P-value .1437 N. B. Two + ve animals of unidentified age Table 9 Sero-prevalence of PPRV-specific antibodies in male and female groups of Sudanese sheep and goats one month after PPR vaccination Sex Male Female Estimated sero-prevalence (173/202) 85.6% (622/653) 95.3% 95% CI 80.8%-90.4% 93.7%-96.9% N.B. Discrepancy between sero-prevalence values after vaccination and detected conversion rates (Table 7 ) was due to that some + ve sera before vaccination failed to reproduce + ve values (scored –ve or doubtful values). Discussion The present work meant to investigate the field performance of the locally produced PPR vaccine; and to update and gain clearer insight in PPR epidemiology in Sudan. In the latter contest, it is crucial to survey apparently healthy, unvaccinated flocks. Previous reports, Saeed et al 2010, Shuaib et al.2014 [ 27 , 34 ] expected that numbers of sheep and goats vaccinated against PPR in Sudan were too small to affect interpretations of serological surveillance. Serological data obtained in this work largely approved these suggestions. Old age groups (> 12 months and > 18 months) in test animals generally showed higher sero-prevalence than young age groups (˂ 12 months) suggesting an increase in the risk of exposure to natural infection with higher age (Table 3 ). The differences were found to be more significant (statistically) where sero-prevalence was high (Table 4 ). It was associated with high exposure of young and old animals to PPRV rather than merely the old (Table 4 ). The latter finding challenged the probability of old animals receiving vaccination once during a lifetime in endemic areas, as suggested by some workers [ 45 ]. Differences in sero-prevalence between old and young animals have completely disappeared after vaccination (Table 8 ) or had been remarkably low in South Darfur (Tables 4 and 5 ). In South Darfur, recent exposure to infection was likely in one district (Kateela) that showed an exceptionally high sero-prevalence (85.3%) similar to that reported (88.9%, 90.7% and 88.6%) in sheep and goats following PPR outbreak [ 46 ] or following PPR vaccination in this work (Fig. 4 ). Recent circulation of PPRV in 1/12 of surveyed districts was not unlikely under the endemic situations probably prevailing in Sudan. These results promised the reliability of outcomes of this work. Serological data on PPR infection in Sudan were not meager; frequently competitive ELISAs [ 27 , 32 , 33 , 34 , 46 , 47 ] and rarely other tests like counter- immuno-electrophoresis (CIEP) [ 33 ] were employed. Previous work determined the extent of PPR infection in different ruminants’ species and pin-point sheep and goats as the main target species of the disease in the country. It has confirmed the wide geographical distribution of PPR infection in Sudan; yet, serological data remained largely tentative and sometimes contradictory regarding high-risk areas. In this work, surveillance was carried out in four Sudanese states, three representing the main pastoral and animal breeding areas in the country in South Eastern (Blue Nile) and Western Sudan (North Kordofan and South Darfur). The 4th state (the Northern State) represents a distinct ecology, the desert ecosystem, where limited animal breeding and pastoralism are practiced. Detected sero-prevalences in sheep (50.2%-57.6% 95% CI.) and goats (50.2%-65% 95% CI), in this work, were statistically similar. Previous reports from Sudan [27; 48; 49] and elsewhere Singh et al.2004 [ 50 ] have generally shown slightly higher sero-prevalence in sheep than in goats. In this work, wide divergence in numbers of tested sheep (683) and goats (172) and in their origin from different geographical regions (data not shown) with different levels of infection could result in such a slight disagreement. In the present work, in different geographical regions, distinct levels of indices of PPR infection were detected: high (64.8%-76.4% 95% CI) in South Eastern Sudan (the Blue Nile state), medium (50.5%-61.9% 95% CI.) in Western Sudan (North Kordofan and South Darfur), and low (28.6%-35.2% 95% C.I) in Northern Sudan (Northern state). Uniformly, districts (n = 6) in Blue Nile and North Kordofan (higher sero-prevalence) showed higher indices of PPR infection than districts (n = 6) in South Darfur (excluding Kateela) and Northern State (lower sero-prevalence) (Fig. 2 ). The lowest sero-prevalence in the Northern State was consistent with the known low density [ 39 ] and animals movement in the desert ecosystem in North Sudan. On the other hand, the Blue Nile state shows the highest animal density in the country [ 39 ] and uniquely constitutes the South-eastern border of Sudan; the nearest point to East Africa (Fig. 1 ). The Blue Nile state encompasses border areas with South Sudan, like South Darfur, and in addition border areas with southern Ethiopia. Molecular data indicated that earlier Sudanese isolates of PPRV were of Lineage III of PPRV which is known to be circulating in East Africa including Ethiopia [19. 23]. In Central and West African countries, closer to Western and South Western Sudan, different lineages, lineage I and II had been prevailing [19. 23]. The emergence of the Asian lineage of PPRV (lineage IV) in Sudan [ 28 ] and other African countries was an illustration of the transboundary nature of PPRV. Network analysis of unique sequences (haplotype) from the 101 N-gene and the 103 F-gene of lineage IV revealed the presence of multiple clusters in isolates from Sudan [ 22 ]. Some of these Sudanese clusters showed closer association with isolates from other countries than with other Sudanese clusters, indicating the likely multiple waves of introduction of PPRV from neighbouring countries [ 22 ]. Accordingly, molecular data highlighted epidemiological links between PPR outbreaks in Sudan and neighbouring countries, mainly in East Africa, which add particular significance to the high indices of PPR infection in the Blue Nile state. Other North-eastern border areas in the country are next to northern areas in neighbouring countries where, like Sudan, less circulation of PPRV is expected. The medium indices of PPR infection detected in Western Sudan were lower (50.5%-57.12% 95% CI) in South Darfur at the South Western border than in North Kordofan (54.1%-61.9% 95% CI) in Central Sudan. Sero-prevalence’s detected in districts in South Darfur was not uniform; it was very high in one district and low in two districts which signalled once more the relatively low sero-prevalence in South Darfur compared to North Kordofan (Fig. 2 ). South Darfur is bordering South Sudan and CAR, while North Kordofan is a central state comprising most of the western flank of the Nile valley (Fig. 1 ). In another instance, Abdalla et al., 2012 [ 48 ], North Kordofan also showed high sero-prevalence [68.4% (n = 215)] similar to the Blue Nile [69.3% (n = 280)] and significantly higher than Al Qadarif [28.6% (n = 105)], a border state in Eastern Sudan. Saeed et al. 2017 [ 32 ] reported high sero-prevalence’s of PPR-specific antibodies in sheep from central (White Nile, Al Gazeera and Blue Nile) states [70.7% (n = 1674)], Darfur (North and South Darfur) states [68.1% (n = 4062)] and Kordofan (North and West Kordofan) states [58.3% (n = 585)]. Obviously, constantly significant indices of PPR infection were detected in Central states including North Kordofan; higher in some instance than border areas in Eastern and Western Sudan. A working hypothesis of PPR circulation in Sudan involves intense circulation of the infection in the breeding and border area of the Blue Nile state and in adjacent Central Sudan, where main animal markets and animal trade exist, is worthy of further investigation. Under field conditions and in absence of any PPR-like clinical signs, vaccination with the locally produced PPR vaccine (Nigeria 75/1) produced an antibody response in 88.4% (343/388) of negative sheep and goats, as detected by cELISA (IDvet, Grabels, France). The commercially available cELISA is indicated by the WOAH 2022 [ 1 ] to assess antibody responses following PPR vaccination or infection and is among the most commonly used tests for this purpose [ 51 ]. A 100% sero-conversion in experimental animals (mainly goats) vaccinated with the Nigeria 75/1 vaccine was reported in laboratory studies [51; 52; 53]. After a vaccination campaign in entire Somalia with the Nigeria 75/1 vaccine, individual animal sero-prevalence increased from 62% before the vaccination campaign to 76% [ 54 ]. The N-specific antibodies detected by the employed cELISA are not neutralizing antibodies. Nonetheless, they are considered indicators of an ongoing T-cell mediated immune response [ 53 ]. Evaluation of antibody responses following PPR vaccination using virus neutralization test (VNT), H-antigen-specific antibodies cELISA which are neutralizing antibodies [ 55 ] or N-antigen-specific antibodies cELISA and challenge studies reported no discrepancy between sero-conversion and protection [51; 52; 53]. On the other hand, Saravanan et al. 2010 [ 56 ] reported 6/6 protection against challenge in goats vaccinated with a PPR vaccine but 4/6 sero-conversion by VNT and cELISA. The Nigeria 75/1 is one of two commonly used PPR vaccines that their universal efficacy has been greatly established against the four known genetic lineages of PPRV [ 51 , 57 , 58 ]. The presented findings, besides suggesting the efficacy of the locally produced Nigeria 75/1 vaccine, it backs its universal efficacy, particularly in sub-Saharan Africa, where poor veterinary infrastructure generally prevails. Sero-conversion rates were around 90% in three states and 76.9% in the fourth state (the Northern State). It was consistently around 90% in 11/12 surveyed districts, apart from one district, Elburgeeg, in Northern State where it was 58% (29/50). Two out of three districts in the Blue Nile state have shown 100% sero-conversion (Fig. 3 ) which was also consistent with the comparatively lower numbers of sero-negative animals in the Blue Nile (74) and the high sero-conversion rate (88.4%) reported in this work. Alternatively, sero-conversion at Elburgeeg was statistically significantly different from that at other districts (p = 0.00001). The Nigeria 75/1 vaccine is thermolabile [ 36 ] and maintenance of the cold chain in the field is necessary to achieve acceptable vaccine performance and efficacy. After reconstitution of the vaccinal material, it is preferred to be administered within 30 minutes [ 24 ]. The vaccine delivery mechanism, including the cold chain, seemed to be functioning efficiently in 11/12 of the vaccinated districts. A low post-vaccination sero-conversion rate (61.13%) in Ethiopia, Faris et al. 2012 [ 59 ], similar to that observed in Elburgeeg, was attributed to the inadequacy of the cold chain. It is to be expected that at areas like Elburgeeg where little acquaintance with the disease has been made (low sero-prevalence), observation of vaccine delivery mechanisms and cold chain recommendations would be less strict. Sero-prevalence of PPRV-specific antibodies in tested animals increased from 54.6% (467/855) before vaccination to 93% (795/855) one month after vaccination. Accordingly, the range of differences between states (Table 2 ) has largely diminished (Fig. 4 ) and differences between age groups have disappeared (overlapping 95% CI) (Table 8 ). It is interesting to observe that after vaccination, the youngest age group (3–6 month), unlike in unvaccinated animals, showed, among the different age groups, the least sero-prevalence (Table 8 ) suggesting a degree of interference between maternal immunity and vaccination. Ata et al. 1989 [ 60 ] and Bedjeh et al. 1999 [ 61 ] indicated that maternal antibodies remain detected up to 6 month of age and maintain protective levels up to 3.5 and 4.5 months in lambs and kids respectively. Significantly higher sero-prevalence persisted in females compared to males before and after vaccination, coinciding to some degree with higher sero-prevalence in old animals than in young animals (3–6 months) before and after vaccination.Acharya et al. 2018 [ 62 ] explained differences in sero-prevalence between females and males by their different proportions in old and young groups in herds. Females are usually kept for longer periods in herds for reproduction, while males are sold for meat production. Several other studies also reported higher sero-prevalence in females than males [ 48 , 49 , 63 ]. Sero-prevalence’s of PPRV-specific antibodies detected in the course of this work after vaccination were precisely measures of response to vaccination. They represented vaccinated population immunity (VPI). The quality of the vaccination programme depends on vaccine coverage in addition to VPI, while the best indicator of breaking virus transmission is the overall population immunity (OPI). Results presented in Fig. (4) showed herd immunity after vaccination of all animals or had only middle age group (7–18 months) animals were vaccinated. The former was strictly VPI while the latter was OPI of the experimental herd had only middle age group was vaccinated. However, in both cases vaccination coverage was 100% which is unachievable in a wide vaccination programme. The middle age groups (7–12 and 13–18 months) were selected for this demonstration for two reasons. First, it showed, particularly in Blue Nile and North Kordofan, lower sero-prevalence than preceding and subsequent age groups (Table 5 ) while the risk of exposure to PPR infection increased with age (Table 3 ) i.e. high risk age. Secondly, before vaccination, it demonstrated in South Darfur, when recent circulation of PPRV was suspected, a higher sero-prevalence than those in the higher and lower age groups (Table 5 ). It was evident that VPI values were high; above 90% in three states and decreased to 84% in the Northern State. On the other hand, values of OPI (had only middle age groups were vaccinated) have a range as low as 44.5% (Northern State). It reached75.5% in North Kordofan and 87.2% in Blue Nile; well above the threshold of 70% indicated by some workers [ 64 , 65 ] for breaking of effective transmission of PPRV. In a state-wide vaccination programme, lower vaccination coverage than the one applied in this work (100%) is expected, yet the achieved herd immunity in these two states is unlikely to fall considerably below 70% since pre-vaccination sero-prevalence’s were already high. These findings suggested targeting control efforts of PPR in Sudan by vaccination of high-risk age groups in high-risk areas such as Blue Nile and North Kordofan. Declarations Acknowledgements We would like to thank the veterinary staff located in the 12 localities of the study area Ethics declarations Ethics approval This study adheres meticulously to institutional, national, and international guidelines, including the Basel Declaration. Every aspect of our research, from the initial design to sample collection, analysis, and dissemination, has been conducted with strict adherence to the principles outlined in these guidelines. We are deeply committed to upholding ethical standards, ensuring animal welfare, and promoting scientific integrity throughout our research endeavors. Approval for the study was obtained from the Central Veterinary Research Laboratory/academic committee under No. 021/092-8004365. The collection of samples was conducted with owner permission by well-trained veterinarians, prioritizing animal welfare regulations. The vaccination process was carried out by authorized personnel from state veterinary authorities using a vaccine certified by CVRL, having successfully passed all quality control tests. We hereby confirm that this study has been conducted in accordance with the ARRIVE (Animal Research: Reporting of In Vivo Experiments) guidelines. All efforts have been made to ensure transparency, rigor, and reproducibility in the design, conduct, and reporting of animal experiments. The manuscript submitted for publication includes relevant details as per the ARRIVE guidelines to facilitate critical evaluation and replication of the study findings." Conflicts of interest The authors declare no conflicts of interest. Data availability The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. Funding This research was financially supported by Food and Agriculture Organization (FAO), Sudan under project No. 021/092-8004365. Contributions Conceptualization: (Omer A. Algezoli, Selma Kamal Ahmed, Tajeldin AM Nour, Mohamed A Abdalla); Methodology: (Omer A. Algezoli, Yazeed A. Raouf, Muzdalifa A. Alamin, Ali H Hiba ); Sampling, vaccination and monitoring of animals: Mohamed Ahmed Aljameel, Sulieman Ibrahim Ahmed, Ibtesam Fadul Elsied Adam, Sir Elkhatim Mohamed Salih,; Analysis (Omer A. Algezoli, Yazeed A. Raouf, Selma Kamal Ahmed) Writing and editing: (Omer A. Algezoli, yazeed A Raouf, Mohamed A Abdalla); Supervision: (Tajeldin AM Nour, Mohamed A Abdalla). All the authors read and approved the final manuscript. Consent to participate All the authors participated voluntarily in the research. 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Algezoli","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8ElEQVRIiWNgGAWjYNCCAhDB3HDgA5BiYydKiwGIYGw4OAOkhZkULcw8YNsIKOYXO3zsww+DWjn59sbGwza/tsnzMTMwfviYg1uL5Oy05Jk9BseNGXsONhzO7btt2MbMwCw5cxseJ93OMWbgMTiW2CyRCNTSc5sRqIWNmRevlvzPjH8MjtW3gbRY9ty2J0JLDjMzj0FNAg9IC8OP24kEtQD9YswsY3DAcAbPwYaDvQ23k9uYGZvx+oVfOvkx45uKOnn59ubDH378uW07v7354IePeLRAwWEIxdgGJhsIqgeCOij9hxjFo2AUjIJRMNIAAGs0UVlxw5QGAAAAAElFTkSuQmCC","orcid":"","institution":"Central Veterinary Research Laboratory","correspondingAuthor":true,"prefix":"","firstName":"Omer","middleName":"","lastName":"Algezoli","suffix":""},{"id":271782954,"identity":"5ef38470-8067-42d8-8611-ab158593b51b","order_by":1,"name":"Selma Kamal","email":"","orcid":"","institution":"Central Veterinary Research 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Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Hiba","middleName":"","lastName":"Ali","suffix":""},{"id":271782958,"identity":"e0899a47-4284-41aa-ae65-6a2f709a0708","order_by":5,"name":"Mohamed Aljameel","email":"","orcid":"","institution":"Nyala veterinary Research Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Mohamed","middleName":"","lastName":"Aljameel","suffix":""},{"id":271782959,"identity":"90a52ca3-760b-4fb5-9766-22eedc2ea237","order_by":6,"name":"Sulieman Ahmed","email":"","orcid":"","institution":"Al Obeid Veterinary Research Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Sulieman","middleName":"","lastName":"Ahmed","suffix":""},{"id":271782960,"identity":"66d6fdc8-57c3-4298-ae4d-365009eda223","order_by":7,"name":"Sir Elkhatim Mohamed","email":"","orcid":"","institution":"Damazine Veterinary Research Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Sir","middleName":"Elkhatim","lastName":"Mohamed","suffix":""},{"id":271782961,"identity":"d8fc0ac4-d147-462d-b6ef-17c80d7c5735","order_by":8,"name":"Ibtesam Fadul Elsied","email":"","orcid":"","institution":"Al Obeid Veterinary Research Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Ibtesam","middleName":"Fadul","lastName":"Elsied","suffix":""},{"id":271782962,"identity":"8399a18e-4b46-4c3f-9e25-fa08f8932e01","order_by":9,"name":"Tajeldin Nour","email":"","orcid":"","institution":"Central Veterinary Research Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Tajeldin","middleName":"","lastName":"Nour","suffix":""},{"id":271782963,"identity":"fca9a165-b405-410c-b0c7-881d7e764cc7","order_by":10,"name":"Mohamed Abdalla","email":"","orcid":"","institution":"Sudan University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Mohamed","middleName":"","lastName":"Abdalla","suffix":""}],"badges":[],"createdAt":"2024-01-07 18:29:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3843259/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3843259/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":50923105,"identity":"765c2ea5-2ffb-43db-aa93-db1e74170c38","added_by":"auto","created_at":"2024-02-09 16:40:18","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":462690,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMap of Sudan showing the study area\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3843259/v1/bdffdad7f05177bb27ba9d2e.jpeg"},{"id":50923104,"identity":"00a92c79-caff-4968-bc45-10837e1a203a","added_by":"auto","created_at":"2024-02-09 16:40:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":100575,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSero-prevalence of PPRV antibodies in sheep and goats in different districts before vaccination\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3843259/v1/db228e0e1c47838f7e9b1a3b.png"},{"id":50923106,"identity":"509d98f6-d179-4566-a00f-5890ac67669e","added_by":"auto","created_at":"2024-02-09 16:40:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":52357,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConversion rate of negative sheep and goat sera (and doubtful) in different districts to positive following vaccination against PPRV\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3843259/v1/df08e390a4a12f97a506ac23.png"},{"id":50923107,"identity":"be326f9b-3bd6-4056-b42d-56ef49e4bbbb","added_by":"auto","created_at":"2024-02-09 16:40:18","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":34508,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eComparison of Sero-prevalence of PPRV-specific antibodies before and after vaccination of Sudanese sheep and goats in different states.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3843259/v1/a54e7f42331346d1ddb88ffc.png"},{"id":54956067,"identity":"2c8f3e97-1ad5-4ec1-9026-b166c2c850f3","added_by":"auto","created_at":"2024-04-19 07:15:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1608798,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3843259/v1/762f2b96-e638-4111-962b-f80ca959f4fd.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Sero-prevalence of peste des petits ruminants virus-specific antibodies in Sudanese sheep and goats before and after vaccination","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePeste des petits ruminants (PPR) is an important transboundary viral disease of small ruminants [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. It primarily affects sheep and goats, the main target species, and occasionally some other artiodactyls including camels [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] and small ruminant wildlife [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Cattle and buffalo are considered susceptible, particularly to subclinical infection [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Clinical PPR in sheep and goats is usually acute; generally, more severe in the latter (goat plaque); characterized by pyrexia, oculo-nasal discharge, stomatitis, diarrhoea, pneumonia and very high morbidity (100%) and mortality (50%-80%) in naive population [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. It is caused by a member of the genus Morbillivirus in the family \u003cem\u003eParamyxoviridae\u003c/em\u003e [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], presently known as Small Ruminant Morbillivirus (SRMV) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. It is a single stranded (-) sense RNA virus. The viral genome encodes six structural proteins: the nucleocapsid (N), phosphoprotein (P), matrix (M), fusion (F), hemagglutinin (H) and polymerase (L) proteins and two non-structural proteins, C and V (16). Based on the partial nucleotide sequence data of the N [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] and F [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] genes, PPR virus (PPRV) isolates can be classified into four genetically distinct lineages: I, II, III and IV. Geographic specificity of these four lineages has been described what, consequently, founded the emergence of molecular epidemiology of PPRV [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe family \u003cem\u003eParamyxoviridae\u003c/em\u003e is known for two members that cause two of the most economically significant diseases; rinderpest virus (RPV) and Newcastle disease virus (NDV). Similarly, PPRV produces a global cost of US\u003cspan\u003e$\u003c/span\u003e2.1\u0026nbsp;billion and troubles the livelihoods of some 900\u0026nbsp;million poor and low-income people [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] in developing countries in Africa (apart from most of South Africa), Middle East and West and South Asia [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Moreover, PPRV poses threats to wildlife conservation [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and has the capability to spread well beyond its historical range into East Asia and the European part of Turkey [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] to threaten the European Union (EU). To alleviate poverty in many developing countries and to eliminate risks associated with PPRV circulation, the FAO and WOAH, based on the successful eradication of the related RPV, targeted PPRV eradication by 2030 [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Like RPV, PPRV is monotypic; available vaccines can induce immunity against all known genotypes i.e., it is of one serotype, and ensuing immunity, following vaccination or infection, is lifelong. Additionally, like RP, the virus does not persist in the environment, and infection primarily requires contact and, moreover, results in no carrier state [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. However, since sheep and goats compared to cattle are more numerous, reproduce more rapidly and having less value per head, the vaccination strategy for PPR is likely to pose more challenges and to be more expensive than that against RP [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Therefore, to develop an appropriate vaccination strategy, the PPR Global Eradication Programme (PPR GER) requires countries to gain clear insight into PPR epidemiology and update the field situation annually to identify hot spots, transmission pathways and populations critical for virus maintenance [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSudan is a vast country in the upper western corner of East Africa that harbors more than seventy million sheep and goats. Peste des petits ruminants were identified in Sudan since 1972, when were misdiagnosed as RP [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Subsequently, it was reported in the country in many instances and in different animal species [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Early Sudanese isolates of PPRV were of lineage III, and later isolates reflected a predominance of lineage IV [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] while the main target species for infection in Sudan have remained sheep and goats. Consistently, the sero-prevalence of PPR antibodies was higher (mostly in the approximate range of 50%-70%) in sheep and goats than in other ruminant species [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Sheep and goat populations from, almost, all investigated Sudanese states have shown serological evidence (approximately 30%-75%) of infection [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The heterologous RP vaccine and, subsequently, the homologous PPR vaccine have been used to control infections in sheep and goats in Sudan. Saeed et al.2010 [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] and Shuaib et al.2014 [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] observed that despite the lack of so-called Differentiation of Infected and Vaccinated Animals (DIVA) capability, the numbers of vaccinated sheep and goats were too small to affect interpretations of serological surveillance.\u003c/p\u003e \u003cp\u003eLocal production of a homologous live attenuated vaccine (Nigeria 75/1) against PPR [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] was established in Sudan in 2004 [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. However, a well-organized vaccination programme against PPR has not yet been developed. The objective of the present work is to enhance the latter endeavor. Given the large number of sheep and goats in Sudan, it meant to identify geographical areas in Sudan and age groups within sheep and goat populations that are crucial for PPRV circulation and maintenance. Prioritization of the vaccination programme based on such information is expected to enhance control. Second, the study aimed to assess sero-conversion following the application of the locally produced PPR vaccine (Nigeria 75/1) under field conditions.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eStudy area:\u003c/h2\u003e\n \u003cp\u003eThe study area included four states: the Blue Nile, North Kordofan, South Darfur and the Northern State (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The first three states are breeding areas, while the Northern State is an important part of a projected disease-free zone. The latter state represents the geographical cluster of northern Sudan, which falls exclusively in the desert ecological zone. The remaining 3 states represent two important geographical clusters [\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]: the Western cluster (North Kordofan and South Darfur) and the South Eastern cluster (the Blue Nile state). The Western cluster is the main pastoral area in the country and falls for the most part in the low-rainfall savannah, addition to small strips of desert and semidesert in the North. The south-eastern cluster includes the Nile valley from the South and South-east up to Khartoum state and falls exclusively, apart from Khartoum, in the low-rainfall savannah. The South Eastern cluster is distinguished by large urban centres along the Blue and White Nile and consequent excessive animal movement related to national trade. Three of the surveyed states (Blue Nile, the Northern State and South Darfur) are border areas, while North Kordofan is a central state (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eNorth Kordofan State constitutes the western flank of the southeastern cluster, with an area of 185,302 km2 at the centre of Sudan and with populations of 2.7\u0026nbsp;million goats and 4.2\u0026nbsp;million sheep [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. The Blue Nile State has the highest animal density in the country, with populations of 480718 goats and 4.1\u0026nbsp;million sheep and an area of 45,844 km2 bordering Ethiopia and South Sudan [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. South Darfur is situated far from the Nile valley, bordering the Central African Republic (CAR) and South Sudan, with an area of 81,000 km2 and 1.7\u0026nbsp;million goats and 2.2\u0026nbsp;million sheep [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. The Northern State has a large area of 348,765 km² and relatively low estimates of animal population of 1.2\u0026nbsp;million goats and one million sheep [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. It contains border areas with Egypt and Libya.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003eSerum samples:\u003c/h2\u003e\n \u003cp\u003eSera were collected from unvaccinated small ruminant flocks (sheep and goats) in the four states in February 2022. The selected animals were more than three months old and apparently healthy. Bled animals, including 653 sheep and 172 goats, were ear-tagged, vaccinated with a locally produced PPR vaccine (Nigeria 75/1), and bled again one month later. During the study period, the animals were inspected for PPR-like clinical signs.\u003c/p\u003e\n \u003cp\u003eIn the first round of sample collection, simple random sampling (SRS) was used to select animals from an available sampling frame of 12 geographical districts or localities (sampling units), 3 in each state (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The approximate sample size required to estimate the prevalence in an infinite population (large) in each sampling unit was calculated using the following formula [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]:\u003c/p\u003e\n \u003cp\u003e\u003cimg src=\"data:image/png;base64,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\"\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003eWhere n = the required sample size;\u003c/p\u003e\n \u003cp\u003eP\u003csub\u003eexp\u003c/sub\u003e = expected prevalence;\u003c/p\u003e\n \u003cp\u003ed = desired absolute precision;\u003c/p\u003e\n \u003cp\u003e1.645 = appropriate multiplier for the required level of confidence\u003c/p\u003e\n \u003cp\u003eAccording to previous studies, an expected prevalence (P) of 70% was used. The desired absolute precision of 10% was applied at a level of confidence of 90%. Accordingly, a sample size of 58 sera in each sampling unit was targeted. Only in two sampling units that have not been achieved, while in South Darfur and Blue Nile states, where a larger population size and more dense distribution prevail, a larger sample size was achieved (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). In each sampling unit, at least eight to ten sampling epi-units (herds or collection sites) were visited to achieve a minimum of 25 epi-units in each surveyed state to stick to statistical theory regarding unbiased parameter estimates [\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e\n \u003ctable border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cp\u003eTable 1\u003c/p\u003e\n \u003cp\u003eSample frame and sample size\u003c/p\u003e\n \u003c/caption\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eState\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eDistrict (sampling unit)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eNo. of samples\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eTotal no. of samples\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eBlue Nile\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eDamazin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eRosayris\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eTadamon\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e99\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eSouth Darfur\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eBaleel\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e225\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eKass\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e99\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eKateela\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e68\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eNorth Kordofan\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eBara\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e189\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eEl-Rahd and Um Rwaba\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eShaekan\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e59\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eNorthern state\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eDongla\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" width=\"25%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e191\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eElburgeeg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e55\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eMarawi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003eELISA method\u003c/h2\u003e\n \u003cp\u003eSera were tested using a commercial competitive ELISA (cELISA) kit (ID screen PPR competition, IDvet Genetics, Grabels, France) according to the manufacturer’s instructions. The employed ELISA is a monoclonal antibody-based cELISA directed against the N protein of PPRV [\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e]. Sera from different states of different age and sex groups were tested simultaneously. The optical density (OD) was read using an ELEX808 microplate photometer at a wavelength of 450 nm. The results are expressed as the sample positivity percentage (S/N %). Samples were considered positive if the S/N % were ≤ 50%, negative if ≥ 60% or doubtful if it was between 50 and 60%.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003eStatistical analysis:\u003c/h2\u003e\n \u003cp\u003eBefore and after vaccination, the sero-prevalence of PPR-specific antibodies in each population or sub-population was calculated by dividing the number of positive reactors identified by the cELISA by the number of sera tested in that population or sub-population, and then multiplying the result by 100.\u003c/p\u003e\n \u003cp\u003eNegative and doubtful reactors in pre-vaccination sera (before vaccination) in each population or sub-population were identified and used to calculate the sero-conversion rate by the vaccine. The conversion rate was calculated by dividing the number of positive reactors identified by the cELISA one month after vaccination by the number of negative and doubtful reactors in pre-vaccination sera in that population or sub-population, then multiplying the result by 100.\u003c/p\u003e\n \u003cp\u003ePrevalence and conversion rates in different populations or sub-populations were compared by determining the 95% confidence intervals (CIs) from a simple random sample based on the normal approximation to the binomial distribution using the formula: P ± 1.96√p(1-p\u003cspan class=\"Underline\"\u003e)\u003c/span\u003e/n [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]. Where P is the estimated prevalence, n is the number of samples tested and 1.96 is the appropriate multiplier for the selected level of confidence. When CI values did not overlap, results were statistically significantly different [\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]. For overlapping CI, p-values were calculated using the chi-square test available at the Statistical Packages for Social Sciences (SPSS) at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e\u003ca href=\"http://www.sociostatistics.com\" target=\"_blank\"\u003ewww.sociostatistics.com\u003c/a\u003e\u003c/span\u003e\u003c/span\u003e (44); the results were significantly different if p \u0026lt; 0.05.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n\u003ch2\u003eSero-prevalence of PPRV-specific antibodies in sheep and goats before vaccination\u003c/h2\u003e\n\u003cp\u003eThe prevalence\u0026rsquo;s of PPRV-specific antibodies was 54.6% in the whole test group (n\u0026thinsp;=\u0026thinsp;855), 53.9% in sheep (n\u0026thinsp;=\u0026thinsp;683), and 57.6% in goats (n\u0026thinsp;=\u0026thinsp;172). The results were statistically similar (P\u0026thinsp;=\u0026thinsp;.3864) for sheep (50.2%-57.6% 95% CI) and goats (50.2%-65% 95% CI) but were dissimilar in different states. In different states, three statistically distinct levels were detected: highest in the Blue Nile, the medium in North Kordofan and South Darfur and the lowest in the Northern State (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). In the Blue Nile and North Kordofan (n\u0026thinsp;=\u0026thinsp;6), where higher sero-prevalence\u0026rsquo;s rate prevailed, districts consistently had higher sero-prevalence rates than in districts in South Darfur and the northern state (n\u0026thinsp;=\u0026thinsp;6); apart from one district, Kateela, in South Darfur (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). In 3 states (Blue Nile, North Kordofan and the Northern State), detected sero-prevalence\u0026rsquo;s in districts (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) were proportional to the estimated general sero-prevalence in the respective state (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). In the 4th state (South Darfur), two districts showed similar sero-prevalence\u0026rsquo;s to those in districts in the Northern state (lower level), while the third district showed the highest sero-prevalence detected in this work before vaccination (85.3%).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSero-prevalence of PPRV-specific antibodies in unvaccinated Sudanese sheep and goats in different states.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eState\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNo. tested\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNo. positive\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eEstimated sero-prevalence\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e95% CI*\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eBlue Nile\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e250\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e176\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e70.4%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e64.76%-76.4%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNorth Kordofan*\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e189\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e109\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e57.7%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e54.11%-61.92%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSouth Darfur*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e225\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e121\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e53.8%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e50.48%-57.12%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNorthern State\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e191\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e61\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e31.9%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e28.58%-35.22%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTotal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e855\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e467\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e54.6%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e53.19%-56.01%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"5\"\u003e*p value\u0026thinsp;=\u0026thinsp;.427\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eBefore vaccination, sero-prevalence\u0026rsquo;s of PPRV-specific antibodies were found to be generally higher in old age groups (\u0026gt;\u0026thinsp;12 months) and females than in young age groups (˂ 12 months) and males (Tables\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e). Differences in sero-prevalence\u0026rsquo;s between the old and young age groups were statistically significant at the high levels of sero-prevalence in the Blue Nile and North Kordofan states but were not at the lower levels of sero-prevalence in South Darfur and the Northern State (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Apart from South Darfur state, sero-prevalence in the oldest age group (\u0026gt;\u0026thinsp;18 month) in all states was higher than that in other age groups (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e). In South Darfur, sero-prevalence in the oldest age group (\u0026gt;\u0026thinsp;18 months) was lower than that in the 7\u0026ndash;12 months and that in the 13\u0026ndash;18 months groups (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e). Interestingly, in the whole test group (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e), sero-prevalence in the youngest age group (3\u0026ndash;6 months) was slightly higher than that in the 7\u0026ndash;12 age group and statistically similar (P value\u0026thinsp;=\u0026thinsp;.05059) to that in the oldest age group (\u0026gt;\u0026thinsp;18 months).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSero-prevalence of PPRV antibodies in different age groups of unvaccinated Sudanese sheep and goats\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eAge group\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e˂ 12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e\u0026gt;\u0026thinsp;12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e3\u0026ndash;6 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e7\u0026ndash;12 moth\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eWhole group\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e13\u0026ndash;18 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u0026gt;\u0026thinsp;18 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eWhole group\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eEstimated sero-prevalence\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(28/61)\u003c/p\u003e\n\u003cp\u003e45.9%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(79/189)\u003c/p\u003e\n\u003cp\u003e41.8%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(107/250)\u003c/p\u003e\n\u003cp\u003e42.8\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(44/68)\u003c/p\u003e\n\u003cp\u003e64.7%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(316/536)\u003c/p\u003e\n\u003cp\u003e59%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(360/604)\u003c/p\u003e\n\u003cp\u003e59.6%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e95% CI\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e33.58%-58.22%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e34.82%-48.78%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e36.7%-48.9%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e51.11%-75.49%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e54.86%-63.14%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\"\u0026minus;\"\u003e\n\u003cp\u003e55.74%-63.46%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eSero-prevalence\u0026rsquo;s in the old age groups did not overlap with those of the young age groups apart from that of the youngest age group (3\u0026ndash;6 month) which was statistically similar (P value\u0026thinsp;=\u0026thinsp;.05059) to that of the oldest age group (\u0026gt;\u0026thinsp;18 month).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eComparison of sero-prevalence of PPRV antibodies between young (3\u0026ndash;12 month) and old (\u0026gt;\u0026thinsp;12 month) unvaccinated sheep and goats in different states (dissimilar levels of infection)\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAge groups\u003c/p\u003e\n\u003cp\u003eState\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e3\u0026ndash;12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u0026gt;\u0026thinsp;12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eBlue Nile\u003c/p\u003e\n\u003cp\u003e[95% CI]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e50.7% (37/73)\u003c/p\u003e\n\u003cp\u003e[39.24%-62.16%]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e78.5% (139/177)\u003c/p\u003e\n\u003cp\u003e[72.47%-84.53%]\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNorth Kordofan\u003c/p\u003e\n\u003cp\u003e[95% CI]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e28.9% (15/52)\u003c/p\u003e\n\u003cp\u003e[16.59%-41.21%]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e68.6% (94/137)\u003c/p\u003e\n\u003cp\u003e[60.84%-76.36%]\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSouth Darfur\u003c/p\u003e\n\u003cp\u003e[95% CI]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e51.8% (44/85)\u003c/p\u003e\n\u003cp\u003e[41.2%-62.4%]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e55% (77/140)\u003c/p\u003e\n\u003cp\u003e[46.75%-63.25%]\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNorthern State\u003c/p\u003e\n\u003cp\u003e[95% CI]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e27.5% (11/40)\u003c/p\u003e\n\u003cp\u003e[13.68%-41.32%]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e33.3% (50/150)\u003c/p\u003e\n\u003cp\u003e[25.75%-40.85%]\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab5\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eComparison of sero-prevalence of PPRV antibodies between different age groups of unvaccinated sheep and goats in different states (dissimilar levels of infection)\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eAge groups\u003c/p\u003e\n\u003cp\u003eState\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e3\u0026ndash;12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e\u0026gt;\u0026thinsp;12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e3\u0026ndash;6 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e7\u0026ndash;12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e13\u0026ndash;18 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u0026gt;\u0026thinsp;18 month\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eBlue Nile\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(5/9)\u003c/p\u003e\n\u003cp\u003e55.6%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e(32/64)\u003c/p\u003e\n\u003cp\u003e50%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(29/39)\u003c/p\u003e\n\u003cp\u003e74.4%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(110/138)\u003c/p\u003e\n\u003cp\u003e79.7%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNorth Kordofan\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(3/7)\u003c/p\u003e\n\u003cp\u003e42.9%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e(12/45)\u003c/p\u003e\n\u003cp\u003e26.7%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(8/14)\u003c/p\u003e\n\u003cp\u003e57.1%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(86/123)\u003c/p\u003e\n\u003cp\u003e69.9%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSouth Darfur\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(20/44)\u003c/p\u003e\n\u003cp\u003e45.5%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e(24/41)\u003c/p\u003e\n\u003cp\u003e58.5%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(6/8)\u003c/p\u003e\n\u003cp\u003e75%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(71/132)\u003c/p\u003e\n\u003cp\u003e53.8%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNorthern State\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(0/1)\u003c/p\u003e\n\u003cp\u003e0.0%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e(11/39)\u003c/p\u003e\n\u003cp\u003e28.2%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(1/7)\u003c/p\u003e\n\u003cp\u003e14.3%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(49/143)\u003c/p\u003e\n\u003cp\u003e34.3%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab6\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSero-prevalence of PPRV-specific antibodies in male and female groups of Sudanese sheep and goats before vaccination\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSex\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMale\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFemale\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eEstimated sero-prevalence\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(90/202) 44.6%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(377/653) 57.7%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e95% CI\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e37.8%-51.4%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e53.9%-61.5%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n\u003ch2\u003ePerformance of the PPR vaccine:\u003c/h2\u003e\n\u003cp\u003eThe vaccine was found to be capable of converting 88.4% of negative (and doubtful) sera to positive (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e). The conversion rate of negative sera was around 90% or above in all states except in the Northern State; it was 76% (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e). It was 100% in 2/12 districts, 90% or above in 8/12 districts, above 85% in 11/12 districts and merely in one district (Elburgeeg) in the Northern state it decreased to 58% (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). At Elburgeeg, the conversion rate of negative sera [58% (29/50)] was significantly lower (p\u0026thinsp;=\u0026thinsp;.00001) than that at other districts [92.9% (314/338)]. Detected sero-prevalence\u0026rsquo;s of PPRV-specific antibodies in different states after vaccination followed the detected conversion rates; it was above 90% in three states (Blue Nile, North Kordofan and South Darfur) and 84.3% in the Northern state (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). In the whole test group, it reached (795/855) 93% (91.3%-94.7% 95% CI). In the second round of ELISA after vaccination, 15/467 sera (3.2%) did not reproduce the positive result and delivered a doubtful or negative result. Accordingly, the range of differences between states (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) has been largely diminished; from 31.9%-70.4% (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) to 84.3%-98.4% (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) while differences between age groups have completely disappeared, showing overlapping 95% CI. and \u0026gt;\u0026thinsp;0.05 P values (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e). The youngest age group (3\u0026ndash;6 months), unlike before vaccination, showed, among the different age groups, the least sero-prevalence. Sero-prevalence in male and female groups remained significantly different after vaccination (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e). Had vaccination against PPRV been limited to the 7\u0026ndash;18 months old animals, post-vaccination sero-prevalence would have reached 87.2%, 75.5%, 62.2% and 44.5% in Blue Nile, North Kordofan, South Darfur and the Northern State (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eNeither were PPR-like clinical signs observed nor reported during the study period. No discrepancy was detected following the serological testing.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab7\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSero-conversion of negative (and doubtful) sheep and goats\u0026rsquo; sera one month following PPR vaccination:\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eState\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNo. -ve\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNo. +ve\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eDetected sero-conversion\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eBlue Nile*\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e74\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e73\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(73/74) 98.6%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNorth Kordofan\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e80\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e71\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(71/80) 88.8%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSouth Darfur**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e104\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e99\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(99/104) 95.2%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNorthern State\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e130\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(100/130) 76.9%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTotal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e388\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e343\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(343/388) 88.4%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab8\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSero-prevalence of PPRV-specific antibodies in different age groups of Sudanese sheep and goats one month after PPR vaccination\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eAge group\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003eLess than 12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003eMore than 12 month\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e3\u0026ndash;6 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e7\u0026ndash;12 moth\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eWhole group\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e13\u0026ndash;18 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u0026gt;\u0026thinsp;18 month\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eWhole group\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eEstimated sero-prevalence\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(53/61)\u003c/p\u003e\n\u003cp\u003e86.9%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(174/189)\u003c/p\u003e\n\u003cp\u003e92.1%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e(227/250)\u003c/p\u003e\n\u003cp\u003e90.8%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e66/68\u003c/p\u003e\n\u003cp\u003e97.1%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e500/536\u003c/p\u003e\n\u003cp\u003e93.3%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e566/604\u003c/p\u003e\n\u003cp\u003e93.7%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e95% CI\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e78.4-%95.4%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e88.3%-95.9%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e87.2%-94.4%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e93.1%-100%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e91.1%-95.5%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e91.7%-95.7%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eP-value\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"6\" align=\"left\"\u003e\n\u003cp\u003e.1437\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"7\"\u003eN. B. Two\u0026thinsp;+\u0026thinsp;ve animals of unidentified age\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab9\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSero-prevalence of PPRV-specific antibodies in male and female groups of Sudanese sheep and goats one month after PPR vaccination\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSex\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMale\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFemale\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eEstimated sero-prevalence\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(173/202) 85.6%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e(622/653) 95.3%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e95% CI\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e80.8%-90.4%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e93.7%-96.9%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eN.B. Discrepancy between sero-prevalence values after vaccination and detected conversion rates (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e) was due to that some\u0026thinsp;+\u0026thinsp;ve sera before vaccination failed to reproduce\u0026thinsp;+\u0026thinsp;ve values (scored \u0026ndash;ve or doubtful values).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present work meant to investigate the field performance of the locally produced PPR vaccine; and to update and gain clearer insight in PPR epidemiology in Sudan. In the latter contest, it is crucial to survey apparently healthy, unvaccinated flocks. Previous reports, Saeed et al 2010, Shuaib et al.2014 [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] expected that numbers of sheep and goats vaccinated against PPR in Sudan were too small to affect interpretations of serological surveillance. Serological data obtained in this work largely approved these suggestions. Old age groups (\u0026gt;\u0026thinsp;12 months and \u0026gt;\u0026thinsp;18 months) in test animals generally showed higher sero-prevalence than young age groups (˂ 12 months) suggesting an increase in the risk of exposure to natural infection with higher age (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The differences were found to be more significant (statistically) where sero-prevalence was high (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). It was associated with high exposure of young and old animals to PPRV rather than merely the old (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The latter finding challenged the probability of old animals receiving vaccination once during a lifetime in endemic areas, as suggested by some workers [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Differences in sero-prevalence between old and young animals have completely disappeared after vaccination (Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e) or had been remarkably low in South Darfur (Tables\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and \u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). In South Darfur, recent exposure to infection was likely in one district (Kateela) that showed an exceptionally high sero-prevalence (85.3%) similar to that reported (88.9%, 90.7% and 88.6%) in sheep and goats following PPR outbreak [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e] or following PPR vaccination in this work (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Recent circulation of PPRV in 1/12 of surveyed districts was not unlikely under the endemic situations probably prevailing in Sudan. These results promised the reliability of outcomes of this work.\u003c/p\u003e \u003cp\u003eSerological data on PPR infection in Sudan were not meager; frequently competitive ELISAs [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e] and rarely other tests like counter- immuno-electrophoresis (CIEP) [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] were employed. Previous work determined the extent of PPR infection in different ruminants\u0026rsquo; species and pin-point sheep and goats as the main target species of the disease in the country. It has confirmed the wide geographical distribution of PPR infection in Sudan; yet, serological data remained largely tentative and sometimes contradictory regarding high-risk areas. In this work, surveillance was carried out in four Sudanese states, three representing the main pastoral and animal breeding areas in the country in South Eastern (Blue Nile) and Western Sudan (North Kordofan and South Darfur). The 4th state (the Northern State) represents a distinct ecology, the desert ecosystem, where limited animal breeding and pastoralism are practiced. Detected sero-prevalences in sheep (50.2%-57.6% 95% CI.) and goats (50.2%-65% 95% CI), in this work, were statistically similar. Previous reports from Sudan [27; 48; 49] and elsewhere Singh et al.2004 [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e] have generally shown slightly higher sero-prevalence in sheep than in goats. In this work, wide divergence in numbers of tested sheep (683) and goats (172) and in their origin from different geographical regions (data not shown) with different levels of infection could result in such a slight disagreement. In the present work, in different geographical regions, distinct levels of indices of PPR infection were detected: high (64.8%-76.4% 95% CI) in South Eastern Sudan (the Blue Nile state), medium (50.5%-61.9% 95% CI.) in Western Sudan (North Kordofan and South Darfur), and low (28.6%-35.2% 95% C.I) in Northern Sudan (Northern state). Uniformly, districts (n\u0026thinsp;=\u0026thinsp;6) in Blue Nile and North Kordofan (higher sero-prevalence) showed higher indices of PPR infection than districts (n\u0026thinsp;=\u0026thinsp;6) in South Darfur (excluding Kateela) and Northern State (lower sero-prevalence) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The lowest sero-prevalence in the Northern State was consistent with the known low density [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] and animals movement in the desert ecosystem in North Sudan. On the other hand, the Blue Nile state shows the highest animal density in the country [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] and uniquely constitutes the South-eastern border of Sudan; the nearest point to East Africa (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The Blue Nile state encompasses border areas with South Sudan, like South Darfur, and in addition border areas with southern Ethiopia. Molecular data indicated that earlier Sudanese isolates of PPRV were of Lineage III of PPRV which is known to be circulating in East Africa including Ethiopia [19. 23]. In Central and West African countries, closer to Western and South Western Sudan, different lineages, lineage I and II had been prevailing [19. 23]. The emergence of the Asian lineage of PPRV (lineage IV) in Sudan [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] and other African countries was an illustration of the transboundary nature of PPRV. Network analysis of unique sequences (haplotype) from the 101 N-gene and the 103 F-gene of lineage IV revealed the presence of multiple clusters in isolates from Sudan [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Some of these Sudanese clusters showed closer association with isolates from other countries than with other Sudanese clusters, indicating the likely multiple waves of introduction of PPRV from neighbouring countries [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Accordingly, molecular data highlighted epidemiological links between PPR outbreaks in Sudan and neighbouring countries, mainly in East Africa, which add particular significance to the high indices of PPR infection in the Blue Nile state. Other North-eastern border areas in the country are next to northern areas in neighbouring countries where, like Sudan, less circulation of PPRV is expected.\u003c/p\u003e \u003cp\u003eThe medium indices of PPR infection detected in Western Sudan were lower (50.5%-57.12% 95% CI) in South Darfur at the South Western border than in North Kordofan (54.1%-61.9% 95% CI) in Central Sudan. Sero-prevalence\u0026rsquo;s detected in districts in South Darfur was not uniform; it was very high in one district and low in two districts which signalled once more the relatively low sero-prevalence in South Darfur compared to North Kordofan (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). South Darfur is bordering South Sudan and CAR, while North Kordofan is a central state comprising most of the western flank of the Nile valley (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In another instance, Abdalla et al., 2012 [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e], North Kordofan also showed high sero-prevalence [68.4% (n\u0026thinsp;=\u0026thinsp;215)] similar to the Blue Nile [69.3% (n\u0026thinsp;=\u0026thinsp;280)] and significantly higher than Al Qadarif [28.6% (n\u0026thinsp;=\u0026thinsp;105)], a border state in Eastern Sudan. Saeed et al. 2017 [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] reported high sero-prevalence\u0026rsquo;s of PPR-specific antibodies in sheep from central (White Nile, Al Gazeera and Blue Nile) states [70.7% (n\u0026thinsp;=\u0026thinsp;1674)], Darfur (North and South Darfur) states [68.1% (n\u0026thinsp;=\u0026thinsp;4062)] and Kordofan (North and West Kordofan) states [58.3% (n\u0026thinsp;=\u0026thinsp;585)]. Obviously, constantly significant indices of PPR infection were detected in Central states including North Kordofan; higher in some instance than border areas in Eastern and Western Sudan. A working hypothesis of PPR circulation in Sudan involves intense circulation of the infection in the breeding and border area of the Blue Nile state and in adjacent Central Sudan, where main animal markets and animal trade exist, is worthy of further investigation.\u003c/p\u003e \u003cp\u003eUnder field conditions and in absence of any PPR-like clinical signs, vaccination with the locally produced PPR vaccine (Nigeria 75/1) produced an antibody response in 88.4% (343/388) of negative sheep and goats, as detected by cELISA (IDvet, Grabels, France). The commercially available cELISA is indicated by the WOAH 2022 [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] to assess antibody responses following PPR vaccination or infection and is among the most commonly used tests for this purpose [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. A 100% sero-conversion in experimental animals (mainly goats) vaccinated with the Nigeria 75/1 vaccine was reported in laboratory studies [51; 52; 53]. After a vaccination campaign in entire Somalia with the Nigeria 75/1 vaccine, individual animal sero-prevalence increased from 62% before the vaccination campaign to 76% [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. The N-specific antibodies detected by the employed cELISA are not neutralizing antibodies. Nonetheless, they are considered indicators of an ongoing T-cell mediated immune response [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]. Evaluation of antibody responses following PPR vaccination using virus neutralization test (VNT), H-antigen-specific antibodies cELISA which are neutralizing antibodies [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e] or N-antigen-specific antibodies cELISA and challenge studies reported no discrepancy between sero-conversion and protection [51; 52; 53]. On the other hand, Saravanan et al. 2010 [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e] reported 6/6 protection against challenge in goats vaccinated with a PPR vaccine but 4/6 sero-conversion by VNT and cELISA. The Nigeria 75/1 is one of two commonly used PPR vaccines that their universal efficacy has been greatly established against the four known genetic lineages of PPRV [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. The presented findings, besides suggesting the efficacy of the locally produced Nigeria 75/1 vaccine, it backs its universal efficacy, particularly in sub-Saharan Africa, where poor veterinary infrastructure generally prevails.\u003c/p\u003e \u003cp\u003eSero-conversion rates were around 90% in three states and 76.9% in the fourth state (the Northern State). It was consistently around 90% in 11/12 surveyed districts, apart from one district, Elburgeeg, in Northern State where it was 58% (29/50). Two out of three districts in the Blue Nile state have shown 100% sero-conversion (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) which was also consistent with the comparatively lower numbers of sero-negative animals in the Blue Nile (74) and the high sero-conversion rate (88.4%) reported in this work. Alternatively, sero-conversion at Elburgeeg was statistically significantly different from that at other districts (p\u0026thinsp;=\u0026thinsp;0.00001). The Nigeria 75/1 vaccine is thermolabile [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] and maintenance of the cold chain in the field is necessary to achieve acceptable vaccine performance and efficacy. After reconstitution of the vaccinal material, it is preferred to be administered within 30 minutes [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The vaccine delivery mechanism, including the cold chain, seemed to be functioning efficiently in 11/12 of the vaccinated districts. A low post-vaccination sero-conversion rate (61.13%) in Ethiopia, Faris et al. 2012 [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e], similar to that observed in Elburgeeg, was attributed to the inadequacy of the cold chain. It is to be expected that at areas like Elburgeeg where little acquaintance with the disease has been made (low sero-prevalence), observation of vaccine delivery mechanisms and cold chain recommendations would be less strict.\u003c/p\u003e \u003cp\u003eSero-prevalence of PPRV-specific antibodies in tested animals increased from 54.6% (467/855) before vaccination to 93% (795/855) one month after vaccination. Accordingly, the range of differences between states (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) has largely diminished (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) and differences between age groups have disappeared (overlapping 95% CI) (Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). It is interesting to observe that after vaccination, the youngest age group (3\u0026ndash;6 month), unlike in unvaccinated animals, showed, among the different age groups, the least sero-prevalence (Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e) suggesting a degree of interference between maternal immunity and vaccination. Ata et al. 1989 [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e] and Bedjeh et al. 1999 [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e] indicated that maternal antibodies remain detected up to 6 month of age and maintain protective levels up to 3.5 and 4.5 months in lambs and kids respectively. Significantly higher sero-prevalence persisted in females compared to males before and after vaccination, coinciding to some degree with higher sero-prevalence in old animals than in young animals (3\u0026ndash;6 months) before and after vaccination.Acharya et al. 2018 [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e] explained differences in sero-prevalence between females and males by their different proportions in old and young groups in herds. Females are usually kept for longer periods in herds for reproduction, while males are sold for meat production. Several other studies also reported higher sero-prevalence in females than males [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e, \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSero-prevalence\u0026rsquo;s of PPRV-specific antibodies detected in the course of this work after vaccination were precisely measures of response to vaccination. They represented vaccinated population immunity (VPI). The quality of the vaccination programme depends on vaccine coverage in addition to VPI, while the best indicator of breaking virus transmission is the overall population immunity (OPI). Results presented in Fig.\u0026nbsp;(4) showed herd immunity after vaccination of all animals or had only middle age group (7\u0026ndash;18 months) animals were vaccinated. The former was strictly VPI while the latter was OPI of the experimental herd had only middle age group was vaccinated. However, in both cases vaccination coverage was 100% which is unachievable in a wide vaccination programme. The middle age groups (7\u0026ndash;12 and 13\u0026ndash;18 months) were selected for this demonstration for two reasons. First, it showed, particularly in Blue Nile and North Kordofan, lower sero-prevalence than preceding and subsequent age groups (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) while the risk of exposure to PPR infection increased with age (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) i.e. high risk age. Secondly, before vaccination, it demonstrated in South Darfur, when recent circulation of PPRV was suspected, a higher sero-prevalence than those in the higher and lower age groups (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). It was evident that VPI values were high; above 90% in three states and decreased to 84% in the Northern State. On the other hand, values of OPI (had only middle age groups were vaccinated) have a range as low as 44.5% (Northern State). It reached75.5% in North Kordofan and 87.2% in Blue Nile; well above the threshold of 70% indicated by some workers [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e, \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e] for breaking of effective transmission of PPRV. In a state-wide vaccination programme, lower vaccination coverage than the one applied in this work (100%) is expected, yet the achieved herd immunity in these two states is unlikely to fall considerably below 70% since pre-vaccination sero-prevalence\u0026rsquo;s were already high. These findings suggested targeting control efforts of PPR in Sudan by vaccination of high-risk age groups in high-risk areas such as Blue Nile and North Kordofan.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank the veterinary staff located in the 12 localities of the study area\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study adheres meticulously to institutional, national, and international guidelines, including the Basel Declaration. Every aspect of our research, from the initial design to sample collection, analysis, and dissemination, has been conducted with strict adherence to the principles outlined in these guidelines. We are deeply committed to upholding ethical standards, ensuring animal welfare, and promoting scientific integrity throughout our research endeavors. Approval for the study was obtained from the Central Veterinary Research Laboratory/academic committee under No. 021/092-8004365. The collection of samples was conducted with owner permission by well-trained veterinarians, prioritizing animal welfare regulations. The vaccination process was carried out by authorized personnel from state veterinary authorities using a vaccine certified by CVRL, having successfully passed all quality control tests. We hereby confirm that this study has been conducted in accordance with the ARRIVE (Animal Research: Reporting of In Vivo Experiments) guidelines. All efforts have been made to ensure transparency, rigor, and reproducibility in the design, conduct, and reporting of animal experiments. The manuscript submitted for publication includes relevant details as per the ARRIVE guidelines to facilitate critical evaluation and replication of the study findings.\u0026quot;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was financially supported by Food and Agriculture Organization (FAO), Sudan under project No. 021/092-8004365.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eContributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: (Omer A. Algezoli, Selma Kamal Ahmed, Tajeldin AM Nour, Mohamed A Abdalla); Methodology: (Omer A. Algezoli, Yazeed A. Raouf, Muzdalifa A. Alamin, Ali H Hiba ); Sampling, vaccination and monitoring of animals: Mohamed Ahmed Aljameel, Sulieman Ibrahim Ahmed, Ibtesam Fadul Elsied Adam, Sir Elkhatim Mohamed Salih,; Analysis (Omer A. Algezoli, Yazeed A. Raouf, Selma Kamal Ahmed) Writing and editing: (Omer A. Algezoli, yazeed A Raouf, Mohamed A Abdalla); Supervision: (Tajeldin AM Nour, Mohamed A Abdalla). All the authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors participated voluntarily in the research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col start=\"1\" type=\"1\"\u003e\n \u003cli\u003e\u003cstrong\u003eWOAH (2022) World Organization for Animal Health (WOAH) (2022)\u003c/strong\u003e Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. Chapter 2.7.11: Peste des Petits Ruminants\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eRoger F, Diallo A, Yigezu LM, Hurard C, Libeau G, Mebratu GY, Faye B. (2000\u003c/strong\u003e) Investigation of a new pathological condition of camels in EthiopiaJ. Camel Pract. 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Jun;29(2):173-179. https://doi.org/10.1007/s13337-018-0449-1.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eKihu SM, Gachohi JM, Ndungu EK. et al. (2015)\u003c/strong\u003e Sero-epidemiology of Peste des petits ruminants virus infection in Turkana County, Kenya. BMC Vet Res 11, 87. https://doi.org/10.1186/s12917-015-0401-1 .\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eSingh RP. (2011)\u003c/strong\u003e Control strategies for peste des petits ruminants in small ruminants of India. Rev Sci Tech. 30(3):879-887. https://doi.org/10.20506/rst.30.3.2079.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eBalamurugan V, Hemadri D, Gajendragad MR, Singh RK, Rahman H. (2014)\u003c/strong\u003e. Diagnosis and control of peste des petits ruminants: A comprehensive review. Virusdisease 25 (1): 39\u0026ndash;56. https://doi.org/10.1007/s13337-013-0188-2.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"ELISA, PPR, Sero-conversion, Sero-prevalence, Small ruminants, Vaccine","lastPublishedDoi":"10.21203/rs.3.rs-3843259/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3843259/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePeste des petits ruminants virus (PPRV) antibodies were studied in Sudanese sheep and goats (n\u0026thinsp;=\u0026thinsp;855) before and after vaccination with a locally produced Nigeria 75/1 vaccine using a commercial competitive ELISA (cELISA) kit (IDvet Grabels). Animals were kept healthy under field conditions, in four states; Blue Nile (n\u0026thinsp;=\u0026thinsp;250), North Kordofan (n\u0026thinsp;=\u0026thinsp;189), South Darfur (n\u0026thinsp;=\u0026thinsp;225) and the Northern State (n\u0026thinsp;=\u0026thinsp;191). Before vaccination, sero-prevalence of PPRV antibodies was 54.6% (53.2%-56% 95% CI); high (64.8%-76.4% 95% CI) in South Eastern Sudan (Blue Nile), medium (50.5%-61.9% 95% CI) in Western Sudan (North Kordofan and South Darfur) and low (28.6%-35.2% 95% C.I) in Northern Sudan (Northern State). In high-risk areas (high sero-prevalence), Blue Nile (70.4%) and North Kordofan (57.7%), middle age groups (7\u0026ndash;12 and 13\u0026ndash;18 months) were identified as high-risk age. Middle age groups showed lower sero-prevalence than preceding (3\u0026ndash;6 months) and subsequent (\u0026gt;\u0026thinsp;18 months) age groups while the risk of exposure increased with age. Current and previous findings suggested a transmission pathway of PPRV involving the South Eastern border (Blue Nile) and neighbouring Central Sudan to North Kordofan.\u003c/p\u003e \u003cp\u003e One month after vaccination 88.4% (343/388) of sero-negative animals were sero-converted suggesting the efficacy of the locally produced Nigeria 75/1 vaccine. Had only the high- risk age group (7\u0026ndash;18 months) was vaccinated, the overall population immunity (OPI) in high-risk areas (Blue Nile and North Kordofan) would have surpassed the threshold of 70% indicated for blocking PPRV transmission. However, lower vaccination coverage is expected in wider vaccination programme. findings justified targeting PPR control in Sudan, primarily, by vaccination of high-risk age groups in high-risk areas.\u003c/p\u003e","manuscriptTitle":"Sero-prevalence of peste des petits ruminants virus-specific antibodies in Sudanese sheep and goats before and after vaccination","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-09 16:40:13","doi":"10.21203/rs.3.rs-3843259/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cd6cd7a5-ce72-4bc4-bdab-29017967b6dc","owner":[],"postedDate":"February 9th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-04-19T07:07:51+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-09 16:40:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3843259","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3843259","identity":"rs-3843259","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}