Seroprevalence and risk factors associated with bovine herpesvirus 1 (BoHV-1) infection in dairy cattle in Northwest Ethiopia

Bovine herpesvirus 1 (BoHV-1) causes significant economic losses in Ethiopia. The infection may occur in a subclinical form or manifest as severe clinical disease. A cross-sectional study was carried out between December 2022 and December 2023 to estimate the animal- and herd-level seroprevalence of BoHV-1 antibodies and to identify potential risk factors associated with the infection in dairy cattle in Northwest Ethiopia. A total of 957 serum samples were randomly collected from 221 dairy cattle herds across seven different locations and tested for antibodies against BoHV-1 glycoprotein gB. Samples were collected from animals over six months old and were tested for BoHV-1 antibodies using a competitive Enzyme-Linked Immunosorbent Assay (c-ELISA). Univariable and multivariable mixed-effects logistic regression analyses with a random herd effect were used to identify potential risk factors associated with BoHV-1 seropositivity. The results showed that the overall seroprevalence of BoHV-1 was 48.1% (95% CI: 44.9%–51.2%) at the animal level and 72.4% (95% CI: 66.5%–78.3%) at the herd level. Old animals over five years of age had a significantly higher odds of BoHV-1 seropositivity of BoHV-1 compared to their younger counterparts (Adjusted Odds Ratio [AOR] = 3.36; 95% CI: 1.73–6.52; P = 0.001). Cattle on farms that used only bulls for breeding had a higher odds of BoHV-1 seropositivity of BoHV-1 compared to farms using artificial insemination (AI) (AOR = 2.96; 95% CI: 1.66–5.27; P = 0.001). This study demonstrates that BoHV-1 infection is highly prevalent among dairy cattle in Northwest Ethiopia at both the individual animal and herd levels. Targeted disease prevention measures, and integrated surveillance strategies are strongly suggested to reduce the transmission and spread of the virus across the region.