Natural tick-borne encephalitis in 2 Huacaya alpacas (Vicugna pacos)

Although rare, tick-borne encephalitis (TBE) is one of the most important and commonly fatal viral diseases affecting the central nervous system (CNS). This arboviral disease is transmitted by ticks and prevalent in widespread parts of Eurasia. Besides humans, several domestic animals such as dogs, horses, and ruminants can also be infected. To our knowledge, there have been no reports of TBE in South American camelids, so far. Here, we present 2 cases of Huacaya alpacas with progressive, therapy-resistant neurologic signs, which were euthanized and submitted for necropsy. Histologic examination of the CNS revealed a moderate lymphohistiocytic meningoencephalomyelitis characterized by perivascular cuffing, glial cell proliferation, neuronal degeneration, and neuronophagia. Tick-borne encephalitis virus (TBEV) infection was confirmed by polymerase chain reaction (PCR), sequencing, immunohistochemistry, and RNAscope in situ hybridization. TBEV should be included as a differential diagnosis in alpacas from endemic regions presenting with neurologic signs.