Epidemiological Survey and Risk Factor Analysis of Bovine Viral Diarrhea in Tibetan Yaks

Epidemiological Survey and Risk Factor Analysis of Bovine Viral Diarrhea in Tibetan Yaks | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Epidemiological Survey and Risk Factor Analysis of Bovine Viral Diarrhea in Tibetan Yaks Zhenjie Yuan, Ma Zhuo, Yan Wang, Hongcai Ma, Jiangyong Zeng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7581982/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Bovine viral diarrhea virus (BVDV) poses a significant threat to the cattle industry. To ascertain the prevalence of BVDV in Tibetan yaks, we used a commercial ELISA kit to test 920 yak serum samples collected from eight counties in three Tibetan regions.. The results revealed an overall seroprevalence of 5.11% (95% CI: 3.78% − 6.74%). The odds ratio (OR) for infection in young cattle ( 3 years). The findings suggest that BVDV is relatively prevalent in yaks in Nagqu, Lhasa, and Shigatse, with young animals showing increased susceptibility. We recommend prioritizing the protection of young yaks in future control strategies. Yak Bovine viral diarrhea virus Epidemiological Survey Figures Figure 1 Introduction Bovine viral diarrhea (BVD) is an infectious disease caused by bovine viral diarrhea virus (BVDV) that exerts a significant impact on the global cattle industry(de Oliveira Luís Guilherme et al. 2020). BVD is an acute, highly contagious disease with characterized by rapid spread and substantial economic burdens worldwide༈Kuca Thibaud, et al. 2020༉. Yuan et al. reported that the expansion of intensive farming in China has driven a year-on-year increase in BVD incidence, severely impeding sustainable industry growth(Yuan et al.2024). Clinically, BVDV-infected cattle typically presen fever, diarrhea, and gastrointestinal mucosal erosions. In pregnant cows, infection can lead to abortion or the birth of weak or malformed calves (Liu et al.2023). Currently, BVD prevention and control efforts are impeded by several challenges. First, the high genetic variability of BVDV and continual emergence of novel subtypes complicate control strategies(Wang et al.2023). Second, existing vaccines confer immunity only to homologous strains and lack cross-protection across subgenotypes, thus limiting vaccine efficacy and innovation(Yuan et al.2022). Globally, BVDV epidemiology is highly diverse, exhibiting region-specific subtype distributions. Chen et al. identified BVDV-1b as the predominant genotype worldwide, whereas subtypes 1t and 1n remain relatively rare(Chen et al.2022 ).In China, a meta-analysis by Zhu et al. estimated an overall BVDV prevalence of 9.8% in cattle herds, including an antigen detection rate of 3.1% and an RNA positivity rate of 19.5% (Zhu et al.2023). In high-altitude ecosystems such as the Qinghai-Tibet Plateau, BVD burden in yaks is particularly severe. Luo et al. reported a seroprevalence of 59.82% for BVDV antibodies among plateau yaks, an antigen detection rate of 4.42%, with 1.55% of animals classified as persistently infected (PI) (Luo et al.2023). Additionally, Zhang et al. determined a true prevalence of 82.30% in Qinghai yaks, with male animals exhibiting a higher seroprevalence (90.01%) than females(Zhang et al.2022). Recently, the intensification of yak husbandry in Tibet has coincided with increasing BVD incidence on the plateau, manifesting as elevated calf mortality and reproductive failures. This trend has undermined industry sustainability and inflicted substantial economic losses. Nevertheless, epidemiological data on BVD in Tibetan yaks remain limited and poorly defined.Accordingly, comprehensive epidemiological investigations in this population are imperative. Materials and methods Study Area and Sample Size From May 2023 to May 2025, 920 yak serum samples were collected from eight counties in the Tibet Autonomous Region: Nyainrong, Biru, and Lhari in Nagqu City; Nyimo and Damxung in Lhasa City; and Yadong,Nyima and Saga in Shigatse City. Samples were collected fromtwo rearing systems: intensive farms and free-range herds. The intensive farms were operated under local government supervision by full-time managers and qualified veterinarians experienced in disease prevention and control. Free-range herds grazed on open pasture. The sampling points were categorized based on elevation, with two altitude strata: >4,400 m and ≤ 4,400 m (Fig. 1). The sample size was calculated using an expected prevalence of 20%, a 95% confidence level, and a 5% margin of error (Saville et al., 2004). Samples were distributed as follows: 137 from Yadong County, 63 from Gyalshar County, 78 from Nyemo County, 67 from Nima County, 217 from Dangxiong County, 35 from Biru County, and 323 from Nyemo County, for a grand total of 920 samples (Fig. 1). Serological analysis Whole blood samples (5 mL) were aseptically collected from bovine jugular veins using standard venipuncture techniques. Following collection, samples were allowed to clot at ambient temperature for 2–3 h. Clotted samples were centrifuged at 3,000 rpm for 10 min (Eppendorf 5810R, Germany) to separate serum. Serum was transferred to sterile 2 mL cryovials (Corning, USA) and stored at − 20 ℃ until analysis. Prior to assay, samples were thawed at 4 ℃ and tested for BVDV antigen using a commercial ELISA kit (BVD.K006/5; Qingdao Realvit Biotechnology Co., Ltd., China), following the manufacturer’s instructions. Statistical analysis All serological testing data were entered into Microsoft Excel and analyzed with R (v. 4.2.2, R Core Team 2022). Associations between BVDV seropositivity and epidemiological factors (breed, age, sex, altitude, sampling year, and management system) were assessed by chi-square tests, and p < 0.05 was considered statistically significant. Variables with p ≤ 0.20 in univariate analyses were entered into a multivariable logistic regression.A backward stepwise elimination was applied to address confounding and examine interactions; variables with p < 0.05 were retained in the final model. Model selection was based on minimization of the Akaike Information Criterion (AIC) (Boukary et al., 2013 ).Model fit was evaluated by likelihood ratio tests for nested models and the Hosmer–Lemeshow goodness-of-fit test.Regression diagnostics were conducted using the “rms” and “ResourceSelection” packages in R. Results and Analysis Serum Sample Detection Results In this study, Of 920 yak serum samples analyzed by ELISA for BVDV antibodies, 84 tested positive, yielding a seroprevalence of 5.11% (95% CI: 3.78%–6.74%). Samples were subsequently stratified by age, sex, altitude, and management system for further statistical evaluation. Univariate Analysis Chi-square tests (Table 1 ) were conducted in R to assess the association between seropositivity and each variable. The results indicated that, Age was significantly associated with seropositivity: animals < 3 years exhibited a rate of 6.34% (42/662) versus 2.97% (10/336) in those ≥ 3 years (χ², p = 0.03).Regarding gender, No significant difference was observed between sexes: females 4.29% (23/536) vs. males 6.25% (24/384) (χ², p = 0.18). In terms of altitude, Altitude strata showed seroprevalences of 3.59% (10/279) at ≤ 4,400 m and 5.77% (37/641) at > 4,400 m, with no statistical significance (χ², p = 0.17). Regarding farming practices, Management system was not associated with serostatus: free-range 5.42% (9/166) vs. intensive 5.18% (38/733) (χ², p = 0.84). Multivariate Analysis A multivariable logistic regression in R was used to evaluate the simultaneous effects of age and altitude on BVDV seropositivity.The results showed that(Table 2 ), Age < 3 years remained a significant risk factor (OR = 2.36; 95% CI: 1.20–5.08; p = 0.02), indicating that younger animals were 2.36 times more likely to be seropositive compared with those ≥ 3 years.Lower altitude (< 4,400 m) yielded a non-significant increase in odds (OR = 1.82; 95% CI: 0.92–3.94; p = 0.10). Discussion Currently, no specific antiviral therapy exists for bovine viral diarrhea (BVD); control depends on vaccination and stringent biosecurity. Owing to BVDV’s genetic diversity, some strains can cause mortality rates up to 30%(Liu,et al., 2023). Transmission occurs primarily via direct contact, with contaminated feed and water as secondary routes. Infected cattle typically present with fever, diarrhea, respiratory signs, and reduced milk yield; in pregnant cows, severe infection may lead to abortion or the birth of malformed calves(Yang,et al., 2023) . In this study, we screened 920 yak sera from Lhasa, Shigatse, and Nagqu by ELISA and observed a seroprevalence of 9.13% (95% CI: 7.3–11.2%). By comparison, Luo et al. reported 59.82% antibody and 4.42% antigen positivity on the Qinghai-Tibet Plateau(Luo,et al., 2023), while Zhang et al. documented an 82.30% true prevalence in Qinghai yaks(Zhang,et al., 2022).Several factors may underlie the observed prevalence differences: (1) High-altitude stressors (hypoxia, intense UV radiation) can compromise yak immunity and enhance susceptibility. (2) Extensive grazing systems coupled with suboptimal vaccination coverage in pastoral regions limit herd immunity and facilitate virus spread (Zhang,et al., 2020). (3) Heterogeneity in herd management and biosecurity-as documented by Liu et al., with seroprevalence up to 62.5% in Xinjiang-similarly explains regional variability within Tibet(Liu,et al., 2023). Effective BVDV control in high-altitude yak systems demands an integrated approach that addresses environmental stressors (e.g., hypoxia, UV radiation), optimized husbandry, and robust farm management. Our data corroborate previous reports and highlight the substantial infection burden in Tibetan yaks, offering critical epidemiological insights to guide tailored interventions. Sustained surveillance, coupled with adaptive, evidence-based measures, will be essential to lower BVDV prevalence and protect the health, productivity, and sustainability of plateau yak herds. BVDV seroprevalence and clinical impact vary markedly with host age. Li et al. examined 2,831 samples from 98 large-scale dairy farms and reported peak infection rates in calves 12 months (Li,et al., 2021 ), with lower rates in intermediate ages. Wang et al. similarly described an age-dependent distribution and urged age-specific control measures (Wang,et al., 2022). In our yak cohort, animals ≥ 3 years showed 10 positives among 336 (2.97%), whereas those < 3 years had 37 positives of 584 (6.34%) (χ², p = 0.026). Multivariable logistic regression identified age < 3 years as an independent risk factor (OR = 2.35; 95% CI: 1.19–5.08; p = 0.02), reinforcing the heightened vulnerability of young yaks to BVDV infection. Several interrelated factors contribute to the increased BVDV susceptibility in young yaks: (1) Immune immaturity: Calves and juveniles (< 3 years) possess underdeveloped innate and adaptive responses, limiting their ability to clear BVDV (Gaituojia,et al., 2023,). (2) Persistent infection (PI): In utero exposure induces immunotolerance and lifelong viral shedding, amplifying herd viral load (Liu,et al., 2023). (3) Waning maternal immunity: Colostral antibodies provide early protection but decline within months, creating a window of vulnerability (Yuan,et al., 2022). (4) Husbandry and biosecurity gaps: Suboptimal age-specific care, incomplete vaccination schedules, and delayed isolation of infected animals—particularly in intensive systems—increase transmission risk (Li,et al., 2021 ). The interplay of these immunological and management factors underlies the higher BVDV incidence observed in younger cattle. Given Tibet’s high-altitude stressors and harsh climate, BVDV control must be customized to local needs. Based on our results and current literature, we propose the following integrated strategies to mitigate BVDV transmission in Tibetan yak herds: (1) Enhance Vaccination Programs.Implement age-specific immunization schedules, with priority on calves < 3 years, to establish robust herd immunity (Wang,et al., 2023).Luo et al. demonstrated that plateau vaccination elevates antibody titers and extends seropositivity duration compared to lowland areas(Luo,et al., 2023). (2) Enforce Quarantine and Biosecurity.Strict Quarantine and Isolation Measures. Implementing strict quarantine standards is essential. New cattle should be isolated and tested to prevent BVDV-positive animals from entering healthy herds (Wang,et al., 2021). Establish on-farm surveillance with rapid detection and immediate segregation of suspect cases to curb spread (Li,et al., 2020). (3) Optimize Husbandry and Farm Management.Maintain optimal stocking densities, minimize environmental stress, and enforce routine cleaning and disinfection of animal housing.Provide balanced rations tailored to altitude-specific nutritional demands to bolster immune competence (Fang,et al., 2020). (4) Implement Surveillance and Data Systems. Deploy real-time health surveillance platforms to monitor serostatus and clinical events across herds.Leverage digital databases and analytics to inform adaptive, evidence-based intervention plans (Chen,et al., 2023). (5) Strengthen Outreach and Capacity Building.Deliver targeted training programs for veterinarians and herders on BVDV epidemiology, vaccination, and biosecurity.Develop practical, region-specific toolkits to support on-farm decision-making and compliance (Su,et al., 2022).By integrating these measures, BVDV incidence in Tibetan yaks can be markedly reduced, safeguarding animal welfare and advancing the sustainable development of plateau yak agriculture. Conclusion This investigation demonstrates significant BVDV seroprevalence in yak herds from Nagqu, Lhasa, and Shigatse, offering critical epidemiological data to inform targeted control measures.Findings confirm that yaks younger than three years are at markedly higher risk of infection.While focused on three Tibetan regions, our study establishes a robust framework for expanded surveillance and comparative analyses across broader pastoral areas.Prevention efforts should prioritize juvenile immunization, strengthen vaccine coverage, and bolster overall herd immunity.Moreover, control programs must be tailored to local husbandry systems and environmental conditions to maximize efficacy.Future studies should elucidate key epidemiological drivers and refine eradication protocols, thereby mitigating BVDV’s detrimental effects on yak production and pastoral livelihoods. Declarations Acknowledgements This work was supported by the XiZang Agriculture and Animal Husbandry Science and Technology Innovation Work Project (XZNKY-2025-CXGC-T20). We also thank the staff of the veterinary epidemic prevention stations in the counties of Nagqu, Lhasa, and Shigatse, XiZang Autonomous Region, for their invaluable assistance during sample collection. Author contribution ZJY and JYZ conceived, designed, and coordinated the study. MZ and YW contributed critical revisions and improvements. ZJY carried out the experiments and performed data analysis. All authors participated in data interpretation and manuscript drafting. All authors read and approved the final version of the manuscript. Funding This work was supported by the XiZang Agriculture and Animal Husbandry Science and Technology Innovation Work Project (XZNKY-2025-CXGC-T20). Data availability All data generated or analyzed during this study are included in this published article. The datasets analyzed during the current study are available from the corresponding author upon rea sonable request. Ethics approval Animal care and experiments were carried out in accordance with the criteria set by the Chinese Guidelines for the Care and Use of Laboratory Animals, and all methodologies were supervised and authorized by the Tibet Academy of Agriculture and Animal Husbandry Sciences’s Institutional Review Board. Consent for publication Not applicable. Conflict of interest The authors declare no competing interests. References De Oliveira Luís Guilherme,Mechler-Dreibi Marina L,Almeida Henrique M S,et al: Bovine Viral Diarrhea Virus: Recent Findings about Its Occurrence in Pigs. 2020 Kuca Thibaud,Passler Thomas,Newcomer Benjamin W,et al: Changes Introduced in the Open Reading Frame of Bovine Viral Diarrhea Virus During Serial Infection of Pregnant Swine. FRONTIERS IN MICROBIOLOGY 2020 Yuan Suya, Tan Qian, Gao Xing. 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Li Xinyu, Ye Feng, Zhong Qi, et al. Detection of bovine viral diarrhea, infectious bovine rhinotracheitis, and brucellosis in Angus cattle introduced to two cattle farms in Xinjiang . China Animal Quarantine, 2020, 37(08):17-20. Zhang Shengke. Epidemiological characteristics and prevention and treatment of yak bovine viral diarrhea. China Livestock and Poultry Breeding, 2020, 16(03):81-82. Tables Table 1: The univariate analysis of risk factors associated with seropositivity in yaks. Risk factors Categorization Prevalence% (95% CI) OR (95% CI) p value Age >3 2.98（1.44，5.41） 0.45（0.22，0.92） 0.03 ≤3 6.34（4.50，8.63） 1 Sex female 4.29（2.74,6.37） 0.67(0.37,1.21) 0.18 Male 6.25(4.05,9.16) 1 Altitude (ASL) ≤4400 m 3.58(1.73,6.49) 0.61(0.30,1.24) 0.17 >4400 m 5.77(4.10,7.87) 1 Management type Intensive farming 5.42(2.51,10.04) 1.05(0.50,2.21) 0.84 free-range farming 5.18(3.69,7.05) 1 Table 2: Multivariable logistic regression analysis of risk factors related to BVDV seropositivity in yaks. Risk factors categories estimate SE（b） OR 95% CI p value Constant -3.97 0.45 Age（years） ≤3 0.86 0.37 2.35 1.19,5.08 0.02 >3 1.00 Alitude(ASL) ≤4400 m 0.60 0.37 1.00 0.10 >4400 m 1.82 0.92,3.94 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 12 Oct, 2025 Reviewers invited by journal 11 Oct, 2025 Editor assigned by journal 12 Sep, 2025 First submitted to journal 11 Sep, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7581982","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":528147475,"identity":"644a1571-c266-4b51-9c4d-cae71df538b3","order_by":0,"name":"Zhenjie 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1","display":"","copyAsset":false,"role":"figure","size":318796,"visible":true,"origin":"","legend":"\u003cp\u003eSpatial distribution of selected sampling counties in the Tibet Autonomous Region, China.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7581982/v1/395598786ef71b7c9944e9f6.png"},{"id":94364366,"identity":"11c2a8c8-aa97-4991-a57f-6f41efc0e62f","added_by":"auto","created_at":"2025-10-27 13:06:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":681245,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7581982/v1/7a6d660a-41e0-4a76-95df-21ed1392d6e0.pdf"}],"financialInterests":"","formattedTitle":"Epidemiological Survey and Risk Factor Analysis of Bovine Viral Diarrhea in Tibetan Yaks","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBovine viral diarrhea (BVD) is an infectious disease caused by bovine viral diarrhea virus (BVDV) that exerts a significant impact on the global cattle industry(de Oliveira Lu\u0026iacute;s Guilherme et al. 2020). BVD is an acute, highly contagious disease with characterized by rapid spread and substantial economic burdens worldwide༈Kuca Thibaud, et al. 2020༉. Yuan et al. reported that the expansion of intensive farming in China has driven a year-on-year increase in BVD incidence, severely impeding sustainable industry growth(Yuan et al.2024). Clinically, BVDV-infected cattle typically presen fever, diarrhea, and gastrointestinal mucosal erosions. In pregnant cows, infection can lead to abortion or the birth of weak or malformed calves (Liu et al.2023).\u003c/p\u003e\u003cp\u003eCurrently, BVD prevention and control efforts are impeded by several challenges. First, the high genetic variability of BVDV and continual emergence of novel subtypes complicate control strategies(Wang et al.2023). Second, existing vaccines confer immunity only to homologous strains and lack cross-protection across subgenotypes, thus limiting vaccine efficacy and innovation(Yuan et al.2022).\u003c/p\u003e\u003cp\u003eGlobally, BVDV epidemiology is highly diverse, exhibiting region-specific subtype distributions. Chen et al. identified BVDV-1b as the predominant genotype worldwide, whereas subtypes 1t and 1n remain relatively rare(Chen et al.2022 ).In China, a meta-analysis by Zhu et al. estimated an overall BVDV prevalence of 9.8% in cattle herds, including an antigen detection rate of 3.1% and an RNA positivity rate of 19.5% (Zhu et al.2023).\u003c/p\u003e\u003cp\u003eIn high-altitude ecosystems such as the Qinghai-Tibet Plateau, BVD burden in yaks is particularly severe. Luo et al. reported a seroprevalence of 59.82% for BVDV antibodies among plateau yaks, an antigen detection rate of 4.42%, with 1.55% of animals classified as persistently infected (PI) (Luo et al.2023). Additionally, Zhang et al. determined a true prevalence of 82.30% in Qinghai yaks, with male animals exhibiting a higher seroprevalence (90.01%) than females(Zhang et al.2022).\u003c/p\u003e\u003cp\u003eRecently, the intensification of yak husbandry in Tibet has coincided with increasing BVD incidence on the plateau, manifesting as elevated calf mortality and reproductive failures. This trend has undermined industry sustainability and inflicted substantial economic losses. Nevertheless, epidemiological data on BVD in Tibetan yaks remain limited and poorly defined.Accordingly, comprehensive epidemiological investigations in this population are imperative.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy Area and Sample Size\u003c/h2\u003e\u003cp\u003eFrom May 2023 to May 2025, 920 yak serum samples were collected from eight counties in the Tibet Autonomous Region: Nyainrong, Biru, and Lhari in Nagqu City; Nyimo and Damxung in Lhasa City; and Yadong,Nyima and Saga in Shigatse City. Samples were collected fromtwo rearing systems: intensive farms and free-range herds. The intensive farms were operated under local government supervision by full-time managers and qualified veterinarians experienced in disease prevention and control. Free-range herds grazed on open pasture.\u003c/p\u003e\u003cp\u003eThe sampling points were categorized based on elevation, with two altitude strata: \u0026gt;4,400 m and \u0026le;\u0026thinsp;4,400 m (Fig.\u0026nbsp;1). The sample size was calculated using an expected prevalence of 20%, a 95% confidence level, and a 5% margin of error (Saville et al., 2004). Samples were distributed as follows: 137 from Yadong County, 63 from Gyalshar County, 78 from Nyemo County, 67 from Nima County, 217 from Dangxiong County, 35 from Biru County, and 323 from Nyemo County, for a grand total of 920 samples (Fig.\u0026nbsp;1).\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eSerological analysis\u003c/h3\u003e\n\u003cp\u003eWhole blood samples (5 mL) were aseptically collected from bovine jugular veins using standard venipuncture techniques. Following collection, samples were allowed to clot at ambient temperature for 2\u0026ndash;3 h. Clotted samples were centrifuged at 3,000 rpm for 10 min (Eppendorf 5810R, Germany) to separate serum. Serum was transferred to sterile 2 mL cryovials (Corning, USA) and stored at \u0026minus;\u0026thinsp;20 ℃ until analysis. Prior to assay, samples were thawed at 4 ℃ and tested for BVDV antigen using a commercial ELISA kit (BVD.K006/5; Qingdao Realvit Biotechnology Co., Ltd., China), following the manufacturer\u0026rsquo;s instructions.\u003c/p\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eAll serological testing data were entered into Microsoft Excel and analyzed with R (v. 4.2.2, R Core Team 2022). Associations between BVDV seropositivity and epidemiological factors (breed, age, sex, altitude, sampling year, and management system) were assessed by chi-square tests, and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e\u003cp\u003eVariables with p\u0026thinsp;\u0026le;\u0026thinsp;0.20 in univariate analyses were entered into a multivariable logistic regression.A backward stepwise elimination was applied to address confounding and examine interactions; variables with p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 were retained in the final model.\u003c/p\u003e\u003cp\u003eModel selection was based on minimization of the Akaike Information Criterion (AIC) (Boukary et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).Model fit was evaluated by likelihood ratio tests for nested models and the Hosmer\u0026ndash;Lemeshow goodness-of-fit test.Regression diagnostics were conducted using the \u0026ldquo;rms\u0026rdquo; and \u0026ldquo;ResourceSelection\u0026rdquo; packages in R.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results and Analysis","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003eSerum Sample Detection Results\u003c/h2\u003e\n \u003cp\u003eIn this study, Of 920 yak serum samples analyzed by ELISA for BVDV antibodies, 84 tested positive, yielding a seroprevalence of 5.11% (95% CI: 3.78%\u0026ndash;6.74%). Samples were subsequently stratified by age, sex, altitude, and management system for further statistical evaluation.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eUnivariate Analysis\u003c/h2\u003e\n \u003cp\u003eChi-square tests (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) were conducted in R to assess the association between seropositivity and each variable. The results indicated that, Age was significantly associated with seropositivity: animals\u0026thinsp;\u0026lt;\u0026thinsp;3 years exhibited a rate of 6.34% (42/662) versus 2.97% (10/336) in those\u0026thinsp;\u0026ge;\u0026thinsp;3 years (\u0026chi;\u0026sup2;, p\u0026thinsp;=\u0026thinsp;0.03).Regarding gender, No significant difference was observed between sexes: females 4.29% (23/536) vs. males 6.25% (24/384) (\u0026chi;\u0026sup2;, p\u0026thinsp;=\u0026thinsp;0.18). In terms of altitude, Altitude strata showed seroprevalences of 3.59% (10/279) at \u0026le;\u0026thinsp;4,400 m and 5.77% (37/641) at \u0026gt;\u0026thinsp;4,400 m, with no statistical significance (\u0026chi;\u0026sup2;, p\u0026thinsp;=\u0026thinsp;0.17). Regarding farming practices, Management system was not associated with serostatus: free-range 5.42% (9/166) vs. intensive 5.18% (38/733) (\u0026chi;\u0026sup2;, p\u0026thinsp;=\u0026thinsp;0.84).\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eMultivariate Analysis\u003c/h3\u003e\n\u003cp\u003eA multivariable logistic regression in R was used to evaluate the simultaneous effects of age and altitude on BVDV seropositivity.The results showed that(Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e), Age\u0026thinsp;\u0026lt;\u0026thinsp;3 years remained a significant risk factor (OR\u0026thinsp;=\u0026thinsp;2.36; 95% CI: 1.20\u0026ndash;5.08; p\u0026thinsp;=\u0026thinsp;0.02), indicating that younger animals were 2.36 times more likely to be seropositive compared with those\u0026thinsp;\u0026ge;\u0026thinsp;3 years.Lower altitude (\u0026lt;\u0026thinsp;4,400 m) yielded a non-significant increase in odds (OR\u0026thinsp;=\u0026thinsp;1.82; 95% CI: 0.92\u0026ndash;3.94; p\u0026thinsp;=\u0026thinsp;0.10).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eCurrently, no specific antiviral therapy exists for bovine viral diarrhea (BVD); control depends on vaccination and stringent biosecurity. Owing to BVDV\u0026rsquo;s genetic diversity, some strains can cause mortality rates up to 30%(Liu,et al., 2023). Transmission occurs primarily via direct contact, with contaminated feed and water as secondary routes. Infected cattle typically present with fever, diarrhea, respiratory signs, and reduced milk yield; in pregnant cows, severe infection may lead to abortion or the birth of malformed calves(Yang,et al., 2023) .\u003c/p\u003e\u003cp\u003eIn this study, we screened 920 yak sera from Lhasa, Shigatse, and Nagqu by ELISA and observed a seroprevalence of 9.13% (95% CI: 7.3\u0026ndash;11.2%). By comparison, Luo et al. reported 59.82% antibody and 4.42% antigen positivity on the Qinghai-Tibet Plateau(Luo,et al., 2023), while Zhang et al. documented an 82.30% true prevalence in Qinghai yaks(Zhang,et al., 2022).Several factors may underlie the observed prevalence differences: (1) High-altitude stressors (hypoxia, intense UV radiation) can compromise yak immunity and enhance susceptibility. (2) Extensive grazing systems coupled with suboptimal vaccination coverage in pastoral regions limit herd immunity and facilitate virus spread (Zhang,et al., 2020). (3) Heterogeneity in herd management and biosecurity-as documented by Liu et al., with seroprevalence up to 62.5% in Xinjiang-similarly explains regional variability within Tibet(Liu,et al., 2023). Effective BVDV control in high-altitude yak systems demands an integrated approach that addresses environmental stressors (e.g., hypoxia, UV radiation), optimized husbandry, and robust farm management. Our data corroborate previous reports and highlight the substantial infection burden in Tibetan yaks, offering critical epidemiological insights to guide tailored interventions. Sustained surveillance, coupled with adaptive, evidence-based measures, will be essential to lower BVDV prevalence and protect the health, productivity, and sustainability of plateau yak herds.\u003c/p\u003e\u003cp\u003eBVDV seroprevalence and clinical impact vary markedly with host age. Li et al. examined 2,831 samples from 98 large-scale dairy farms and reported peak infection rates in calves\u0026thinsp;\u0026lt;\u0026thinsp;3 months and cattle\u0026thinsp;\u0026gt;\u0026thinsp;12 months (Li,et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), with lower rates in intermediate ages. Wang et al. similarly described an age-dependent distribution and urged age-specific control measures (Wang,et al., 2022). In our yak cohort, animals\u0026thinsp;\u0026ge;\u0026thinsp;3 years showed 10 positives among 336 (2.97%), whereas those\u0026thinsp;\u0026lt;\u0026thinsp;3 years had 37 positives of 584 (6.34%) (χ\u0026sup2;, p\u0026thinsp;=\u0026thinsp;0.026). Multivariable logistic regression identified age\u0026thinsp;\u0026lt;\u0026thinsp;3 years as an independent risk factor (OR\u0026thinsp;=\u0026thinsp;2.35; 95% CI: 1.19\u0026ndash;5.08; p\u0026thinsp;=\u0026thinsp;0.02), reinforcing the heightened vulnerability of young yaks to BVDV infection. Several interrelated factors contribute to the increased BVDV susceptibility in young yaks: (1) Immune immaturity: Calves and juveniles (\u0026lt;\u0026thinsp;3 years) possess underdeveloped innate and adaptive responses, limiting their ability to clear BVDV (Gaituojia,et al., 2023,). (2) Persistent infection (PI): In utero exposure induces immunotolerance and lifelong viral shedding, amplifying herd viral load (Liu,et al., 2023). (3) Waning maternal immunity: Colostral antibodies provide early protection but decline within months, creating a window of vulnerability (Yuan,et al., 2022). (4) Husbandry and biosecurity gaps: Suboptimal age-specific care, incomplete vaccination schedules, and delayed isolation of infected animals\u0026mdash;particularly in intensive systems\u0026mdash;increase transmission risk (Li,et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The interplay of these immunological and management factors underlies the higher BVDV incidence observed in younger cattle.\u003c/p\u003e\u003cp\u003eGiven Tibet\u0026rsquo;s high-altitude stressors and harsh climate, BVDV control must be customized to local needs. Based on our results and current literature, we propose the following integrated strategies to mitigate BVDV transmission in Tibetan yak herds: (1) Enhance Vaccination Programs.Implement age-specific immunization schedules, with priority on calves\u0026thinsp;\u0026lt;\u0026thinsp;3 years, to establish robust herd immunity (Wang,et al., 2023).Luo et al. demonstrated that plateau vaccination elevates antibody titers and extends seropositivity duration compared to lowland areas(Luo,et al., 2023). (2) Enforce Quarantine and Biosecurity.Strict Quarantine and Isolation Measures. Implementing strict quarantine standards is essential. New cattle should be isolated and tested to prevent BVDV-positive animals from entering healthy herds (Wang,et al., 2021). Establish on-farm surveillance with rapid detection and immediate segregation of suspect cases to curb spread (Li,et al., 2020). (3) Optimize Husbandry and Farm Management.Maintain optimal stocking densities, minimize environmental stress, and enforce routine cleaning and disinfection of animal housing.Provide balanced rations tailored to altitude-specific nutritional demands to bolster immune competence (Fang,et al., 2020). (4) Implement Surveillance and Data Systems. Deploy real-time health surveillance platforms to monitor serostatus and clinical events across herds.Leverage digital databases and analytics to inform adaptive, evidence-based intervention plans (Chen,et al., 2023). (5) Strengthen Outreach and Capacity Building.Deliver targeted training programs for veterinarians and herders on BVDV epidemiology, vaccination, and biosecurity.Develop practical, region-specific toolkits to support on-farm decision-making and compliance (Su,et al., 2022).By integrating these measures, BVDV incidence in Tibetan yaks can be markedly reduced, safeguarding animal welfare and advancing the sustainable development of plateau yak agriculture.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis investigation demonstrates significant BVDV seroprevalence in yak herds from Nagqu, Lhasa, and Shigatse, offering critical epidemiological data to inform targeted control measures.Findings confirm that yaks younger than three years are at markedly higher risk of infection.While focused on three Tibetan regions, our study establishes a robust framework for expanded surveillance and comparative analyses across broader pastoral areas.Prevention efforts should prioritize juvenile immunization, strengthen vaccine coverage, and bolster overall herd immunity.Moreover, control programs must be tailored to local husbandry systems and environmental conditions to maximize efficacy.Future studies should elucidate key epidemiological drivers and refine eradication protocols, thereby mitigating BVDV\u0026rsquo;s detrimental effects on yak production and pastoral livelihoods.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the XiZang Agriculture and Animal Husbandry Science and Technology Innovation Work Project (XZNKY-2025-CXGC-T20). We also thank the staff of the veterinary epidemic prevention stations in the counties of Nagqu, Lhasa, and Shigatse, XiZang Autonomous Region, for their invaluable assistance during sample collection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eZJY and JYZ conceived, designed, and coordinated the study. MZ and YW contributed critical revisions and improvements. ZJY carried out the experiments and performed data analysis. All authors participated in data interpretation and manuscript drafting. All authors read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the XiZang Agriculture and Animal Husbandry Science and Technology Innovation Work Project (XZNKY-2025-CXGC-T20).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article. The datasets analyzed during the current study are available from the corresponding author upon rea sonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAnimal care and experiments were carried out in accordance with the criteria set by the Chinese Guidelines for the Care and Use of Laboratory Animals, and all methodologies were supervised and authorized by the Tibet Academy of Agriculture and Animal Husbandry Sciences\u0026rsquo;s Institutional Review Board.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDe Oliveira Lu\u0026iacute;s Guilherme,Mechler-Dreibi Marina L,Almeida Henrique M S,et al: Bovine Viral Diarrhea Virus: Recent Findings about Its Occurrence in Pigs. 2020\u003c/li\u003e\n\u003cli\u003eKuca Thibaud,Passler Thomas,Newcomer Benjamin W,et al: Changes Introduced in the Open Reading Frame of Bovine Viral Diarrhea Virus During Serial Infection of Pregnant Swine. 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Animal Husbandry and Veterinary Medicine, 2023, 55(08):79-85.\u003c/li\u003e\n\u003cli\u003eLiu Qiuli. The harm and prevention of bovine viral diarrhea. Northern Animal Husbandry, 2023, (14):34+36.\u003c/li\u003e\n\u003cli\u003eLiu Dong, Li Xiaohan, Guo Yubin, et al. Etiological monitoring results and epidemiological characteristic analysis of viral diarrhea in Heze City from 2018 to 2021. Medical Animal Control, 2023, 39(07):625-628.\u003c/li\u003e\n\u003cli\u003eLiu Jianhui, Ma Siwen, Zhang Yongming, et al. Study on the epidemiological characteristics and diagnosis and prevention measures of bovine viral diarrhea virus. Feed Industry, 2023, 44(19):108-112. DOI:10.13302/j.cnki.fi.2023.19.018.\u003c/li\u003e\n\u003cli\u003eYang Dexin, Shen Puxiu, Yu Jingcheng, et al. Epidemiological survey of bovine viral diarrhea in large-scale dairy farms in Henan Province,Chinese Veterinary Obstetrics Branch of Chinese Association of Animal Science and Veterinary Medicine. Proceedings of the 16th Academic Seminar of the Chinese Veterinary Obstetrics Branch. 2023:1. DOI:10.26914/c.cnkihy.2023.096949.\u003c/li\u003e\n\u003cli\u003eWang Bao, Zhang Xingxing, Zhang Baogang, et al. Serological survey of bovine viral diarrhea in a beef cattle farm in the Yili area. Xinjiang Agricultural Reclamation Science and Technology, 2023, 46(01):44-46. DOI:10.16437/j.cnki.1007-5038.2022.03.017.\u003c/li\u003e\n\u003cli\u003eSu Sai Sangzhuoma. Epidemiological characteristics and prevention and treatment of yak bovine viral diarrhea. Animal Husbandry and Veterinary Science (Electronic Edition), 2022, (22):112-114.\u003c/li\u003e\n\u003cli\u003eSaville W J, Wittum T E. 2004. Veterinary Epidemiology. Equine Internal Medicine (Second Edition), 6: 1513-1528.\u003c/li\u003e\n\u003cli\u003eBoukary A R, Saegerman C, Abatih E, Fretin D, Alambedji B R, De Deken R, Harouna H A, Yenikoye A, Thys E. 2013. Seropreva lence and potential risk factors for Brucella spp. infection in traditional cattle, sheep and goats reared in urban, periurban and rural areas of Niger. PLoS One, 8(12): e83175.\u003c/li\u003e\n\u003cli\u003eChen Jie, Zuo Zhicai, Cai Dongjie, et al. Global genotypes and subtypes of bovine viral diarrhea virus. Acta Agriculturae Zhejiangensis, 2022, 34(12):2622-2628.\u003c/li\u003e\n\u003cli\u003eSu Sai Sangzhuoma. Epidemiological characteristics and diagnosis and treatment of yak bovine viral diarrhea. Animal Husbandry and Veterinary Science (Electronic Edition), 2022, (21):81-83.\u003c/li\u003e\n\u003cli\u003eZhu Jie, Yang Caijun, Qi Mingpu, et al. Meta-analysis of the prevalence of bovine viral diarrhea virus in cattle herds in China. Journal of Huazhong Agricultural University, 2023, 42(02):48-62. DOI:10.13300/j.cnki.hnlkxb.2023.02.007.\u003c/li\u003e\n\u003cli\u003eFang Hui, Zhang Hongmei, Xu Zhiyin, et al. Epidemiological characteristics of viral diarrhea in Minhang District, Shanghai from 2014 to 2020. Journal of Tropical Medicine, 2022, 22(08):1163-1166.\u003c/li\u003e\n\u003cli\u003eYuan Ye. Molecular epidemiological investigation of bovine viral diarrhea virus and expression of truncated E2 protein. Yunnan Agricultural University, 2022. DOI:10.27458/d.cnki.gynyu.2022.000190.\u003c/li\u003e\n\u003cli\u003eDong Kun. Epidemiological survey of bovine viral diarrhea and purification of cattle farms . Jilin University, 2022. DOI:10.27162/d.cnki.gjlin.2022.003063.\u003c/li\u003e\n\u003cli\u003eZhang Zhonghui, Gao Shandian, Chu Yuefeng, et al. Serological analysis of bovine viral diarrhea in yaks in four counties of Qinghai Province. Progress in Veterinary Medicine, 2022, 43(03):28-32. DOI:10.16437/j.cnki.1007-5038.2022.03.017.\u003c/li\u003e\n\u003cli\u003eYang Xianchao, Yang Dequan, Tao Tiangu Shen, et al. Research progress on bovine viral diarrhea-mucosal disease. China Dairy Cattle, 2022, (01):17-20. DOI:10.19305/j.cnki.11-3009/s.2022.01.005.\u003c/li\u003e\n\u003cli\u003eLi Tianzeng, Huang Huiwen, Shi Xinchuan, et al. Epidemiological survey and analysis of bovine viral diarrhea in China. China Dairy Cattle, 2021, (09):36-39. DOI:10.19305/j.cnki.11-3009/s.2021.09.009.\u003c/li\u003e\n\u003cli\u003eWang Chenyu, Song Jie, Cao Mengyuan, et al. Investigation and prevention and control measures of bovine viral diarrhea disease in some large-scale dairy farms in Xinjiang. China Dairy, 2021, (08):96-100.\u003c/li\u003e\n\u003cli\u003eWei Qi, Qu Yonggang, Chang Junshuai, et al. Epidemiological survey of bovine viral diarrhea in some areas of Xinjiang [J]. Animal Husbandry and Veterinary Medicine, 2020, 52(12):105-109.\u003c/li\u003e\n\u003cli\u003eZhang Wenxiu. Epidemiological characteristics and prevention and treatment of yak bovine viral diarrhea. China Livestock and Poultry Breeding, 2020, 16(08):141.\u003c/li\u003e\n\u003cli\u003eLi Xinyu, Ye Feng, Zhong Qi, et al. Detection of bovine viral diarrhea, infectious bovine rhinotracheitis, and brucellosis in Angus cattle introduced to two cattle farms in Xinjiang . China Animal Quarantine, 2020, 37(08):17-20.\u003c/li\u003e\n\u003cli\u003eZhang Shengke. Epidemiological characteristics and prevention and treatment of yak bovine viral diarrhea. China Livestock and Poultry Breeding, 2020, 16(03):81-82.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cdiv\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"594\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 594px;\"\u003e\n \u003cp\u003eTable 1: The univariate analysis of risk factors associated with seropositivity in yaks.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003eRisk factors\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003eCategorization\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003ePrevalence% (95% CI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003eOR (95% CI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 66px;\"\u003e\n \u003cp\u003ep value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 116px;\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003e\u0026gt;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e2.98（1.44，5.41）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e0.45（0.22，0.92）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003e\u0026le;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e6.34（4.50，8.63）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 116px;\"\u003e\n \u003cp\u003eSex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003efemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e4.29（2.74,6.37）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e0.67(0.37,1.21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e6.25(4.05,9.16)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 116px;\"\u003e\n \u003cp\u003eAltitude (ASL)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003e\u0026le;4400 m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e3.58(1.73,6.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e0.61(0.30,1.24)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003e\u0026gt;4400 m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e5.77(4.10,7.87)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 116px;\"\u003e\n \u003cp\u003eManagement type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003eIntensive farming\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e5.42(2.51,10.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e1.05(0.50,2.21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 134px;\"\u003e\n \u003cp\u003efree-range farming\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e5.18(3.69,7.05)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e1\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\u003e\u003cbr\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"512\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\" style=\"width: 512px;\"\u003e\n \u003cp\u003eTable 2: Multivariable logistic regression analysis of risk factors related to BVDV seropositivity in yaks.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eRisk factors\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003ecategories\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003eestimate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003eSE（b）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 48px;\"\u003e\n \u003cp\u003eOR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 97px;\"\u003e\n \u003cp\u003e95% CI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 57px;\"\u003e\n \u003cp\u003ep value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eConstant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e-3.97\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.45\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 57px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eAge（years）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e\u0026le;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e0.86\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.37\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 48px;\"\u003e\n \u003cp\u003e2.35\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 97px;\"\u003e\n \u003cp\u003e1.19,5.08\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e\u0026gt;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 48px;\"\u003e\n \u003cp\u003e1.00\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eAlitude(ASL)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e\u0026le;4400 m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e0.60\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.37\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 48px;\"\u003e\n \u003cp\u003e1.00\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 97px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0.10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e\u0026gt;4400 m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 75px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 48px;\"\u003e\n \u003cp\u003e1.82\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 97px;\"\u003e\n \u003cp\u003e0.92,3.94\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"tropical-animal-health-and-production","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"trop","sideBox":"Learn more about [Tropical Animal Health and Production](https://www.springer.com/journal/11250)","snPcode":"11250","submissionUrl":"https://submission.nature.com/new-submission/11250/3","title":"Tropical Animal Health and Production","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Yak, Bovine viral diarrhea virus, Epidemiological Survey","lastPublishedDoi":"10.21203/rs.3.rs-7581982/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7581982/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBovine viral diarrhea virus (BVDV) poses a significant threat to the cattle industry. To ascertain the prevalence of BVDV in Tibetan yaks, we used a commercial ELISA kit to test 920 yak serum samples collected from eight counties in three Tibetan regions.. The results revealed an overall seroprevalence of 5.11% (95% CI: 3.78% \u0026minus;\u0026thinsp;6.74%). The odds ratio (OR) for infection in young cattle (\u0026lt;\u0026thinsp;3 years) was 2.36 (95% CI: 1.20\u0026ndash;5.08, p-value\u0026thinsp;=\u0026thinsp;0.02), indicating that young animals have a 2.36-fold higher risk of infection compared with older cattle (\u0026gt;\u0026thinsp;3 years). The findings suggest that BVDV is relatively prevalent in yaks in Nagqu, Lhasa, and Shigatse, with young animals showing increased susceptibility. We recommend prioritizing the protection of young yaks in future control strategies.\u003c/p\u003e","manuscriptTitle":"Epidemiological Survey and Risk Factor Analysis of Bovine Viral Diarrhea in Tibetan Yaks","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-24 09:26:00","doi":"10.21203/rs.3.rs-7581982/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-10-12T05:38:09+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-11T17:00:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-12T11:17:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"Tropical Animal Health and Production","date":"2025-09-11T05:42:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"tropical-animal-health-and-production","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"trop","sideBox":"Learn more about [Tropical Animal Health and Production](https://www.springer.com/journal/11250)","snPcode":"11250","submissionUrl":"https://submission.nature.com/new-submission/11250/3","title":"Tropical Animal Health and Production","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"79240065-2b7d-4911-9776-492e1511c3a5","owner":[],"postedDate":"October 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-17T04:14:54+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-24 09:26:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7581982","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7581982","identity":"rs-7581982","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}