Two outbreaks of Varicellovirus bovine alpha (herpesvirus)-5 meningoencephalitis in Argentinian calves.

Varicellovirus bovinealpha-5 (BoAHV-5) is a neurotropic virus that causes necrotizing meningoencephalitis in calves. This report describes two outbreaks of BoAHV-5-associated meningoencephalitis in beef cattle. The incidence was 6.2% and 12.93% for each outbreak, respectively. Lethality was 100% in both outbreaks. Neurological signs included dullness, ataxia, and circling. The main gross finding was focal malacia in the parietal and frontal cerebral cortex of five calves autopsied. Microscopically, severe necrotizing meningoencephalitis with intranuclear eosinophilic to amphophilic inclusion bodies within astrocytes was observed in the five animals. BoAHV-5 was detected by PCR in the central nervous system of two animals (one from each outbreak). Although this disease has been reported before in South America, the most recent reports date back to the 1980s. The findings of this study suggest that BoAHV-5 should be considered a differential diagnosis for neurological disease in calves.