Molecular Detection and Epidemiology of Equine Herpesvirus 2 and 5 in Working Equids in Central Ethiopia

Background: Equine respiratory illness is a common problem that impacts the performance of the working capacity of equids. In Ethiopia, respiratory disease is the most common presenting complaint at veterinary clinics and a priority concern for equid owners and veterinary practitioners. Although studies had been conducted in EHV-2 and EHV-5 elsewhere in the world, many unknowns remained. Thus, a detailed study is needed to understand more about the epidemiology of the viruses. This study aimed to detect EHV-2 and EHV-5 from working equids in central Ethiopia. Methods: Nasopharyngeal swabs were collected from 58 horses and donkeys to detect EHV-2 and EHV-5 using PCR. Viral DNA was extracted and PCR amplification was performed using virus-specific primers targeting the conserved region of glycoprotein B (gB) genes. Results: From 58 equids, EHV-5 and EHV-2 were detected in 20 (34.5%) and 19 (32.8%) equids, respectively. Concurrent infection with EHV-2 and EHV-5 was found in 6 (10.3%) diseased equids. EHV-2 was detected in a significantly higher proportion (P = 0.002) in horses (54.5%; n = 18) than donkeys (4%; n = 1). In contrast, a significantly higher (P = 0.004) proportion of EHV-5 was detected in donkeys (56%; n =14) than horses (18.2%; n = 6). EHV-2 was detected in a significantly higher (P = 0.006) proportion in equids displaying signs of respiratory disease (16/33; 48.5%) compared to those without disease (3/25; 12%). EHV-2 positive equids were seven times more likely to display clinical signs of respiratory disease than EHV-2-negative equids (OR = 6.9; 95% CI: 1.72-27.60). For EHV-5, the observed difference was not statistically significant (P = 0.832). A significantly higher (P = 0.041) proportion of EHV-2 was detected in equids living in midland (52.9%; n = 9) compared with highland (24.4%; n = 10). Equids residing in the midland were four times more likely to be exposed to EHV-2 than highland equids (OR = 3.97; 95% CI: 1.05 - 14.89). Conclusion: EHV-2 and EHV-5 are highly prevalent both in horses and donkeys residing in central Ethiopia. Species-specific susceptibility differences in EHV-2 and EHV-5 infection are observed. The observed causal association between EHV-2-test-positive and the appearance of clinical signs of respiratory disorders should be further investigated.