Seroprevalence, distribution, and risk factors of infectious bovine rhinotracheitis in eastern and southern Algeria.

Infectious bovine rhinotracheitis (IBR), caused by Bovine Herpesvirus-1 (BoHV-1), represents a significant economic burden on the global dairy industry through reduced productivity, reproductive disorders, and abortion. This cross-sectional study estimated the seroprevalence of IBR and identified associated risk factors among cattle in Eastern and Southern Algeria. Between September and December 2023, blood samples were collected from 380 cattle across 45 unvaccinated dairy farms in thirteen provinces. Sera were tested for BoHV-1 antibodies using a competitive enzyme-linked immunosorbent assay (cELISA), and seropositive samples underwent DIVA testing (Differentiating Infected from Vaccinated Animals) to detect glycoprotein E (gE) antibodies. Multivariable logistic regression analysis assessed risk factor associations with seropositivity. The overall seroprevalence was 38.95% (148/380), with a 100% herd-level prevalence. Among seropositive animals, 66.89% (99/148) were gE-positive, indicating natural infection, while 33.11% (49/148) were gE-negative, suggesting prior vaccination or vaccination exposure. Multivariable analysis identified four significant risk factors (p < 0.05): exotic origin (aOR = 5.33), large herd size (aOR = 2.12), age >3 years (aOR = 1.77), and breed, with crossbreeds showing lower susceptibility (aOR = 0.15) compared to Prim'Holstein cattle. These findings demonstrate widespread circulation of IBR in Algerian cattle, predominantly through natural infection rather than vaccination. The implementation of comprehensive control strategies, including official vaccination programmes utilizing DIVA-compatible vaccines and enhanced biosecurity measures, is crucial to mitigate economic losses in Algeria's dairy sector.