Abstract
BACKGROUND AND AIM: Malignant catarrhal fever (MCF) is a highly fatal disease caused by ovine herpesvirus-2 (OvHV-2), with sheep acting as asymptomatic reservoir hosts. In Indonesia, MCF remains underdiagnosed due to its predominantly subclinical presentation, particularly in regions where mixed ruminant farming is practiced. Riau Province has a large population of Bali cattle, and sheep production is increasing, raising concerns regarding OvHV-2 spillover. This study aimed to determine the molecular prevalence of OvHV-2 infection in cattle and identify individual- and herd-level risk factors associated with the occurrence of MCF in Riau Province, Indonesia. MATERIALS AND METHOD: A cross-sectional study was conducted between August and December 2024 involving 274 beef cattle from 76 farms across five districts of Riau Province. Buffy coat DNA extracted from ethylenediaminetetraacetic acid-anticoagulated blood samples was examined for OvHV-2 using nested polymerase chain reaction (PCR). Epidemiological data were collected through structured questionnaires administered to farmers. The associations between potential risk factors and OvHV-2 positivity were evaluated using chi-square tests and multivariate logistic regression analysis. RESULT: OvHV-2 DNA was detected in 33 of 274 cattle, yielding an individual-level prevalence of 12.0% (95%CI: 8.0-16.0%). At the farm-level, 21 of 76 farms (27.6%; 95% confidence interval [CI]: 17.0%-38.0%) had at least one PCR-positive animal. Most infected cattle (n = 32/33) were clinically asymptomatic, emphasizing the silent nature of infection. The multivariable analysis identified cattle aged 2-5 years as having a significantly lower risk of infection (adjusted odds ratio [aOR] = 0.239; p = 0.004). In contrast, farms that practiced mixed rearing of cattle and sheep showed a markedly increased risk of MCF (aOR = 8.218; p = 0.015), as did farms located within 100 m of sheep holdings (aOR = 4.083; p = 0.027). CONCLUSIO: OvHV-2 infection is endemic but largely subclinical in cattle in Riau Province. Close proximity to sheep and co-rearing practices are the primary drivers of MCF risk. These findings underscore the importance of molecular surveillance and the implementation of biosecurity measures, particularly spatial separation between cattle and sheep, to prevent OvHV-2 transmission and reduce economic losses in susceptible cattle populations.