Thaller et al.
Natural tick-borne encephalitis in 2 Huacaya alpacas (Vicugna pacos). Vet Pathol. 2025. Published online August 19, 2025. doi:10.1177/03009858251362432.
In recent years, South American camelids, including alpacas, have gained popularity in Europe and are increasingly exposed to pathogens outside their natural habitat. Two cases of natural tick-borne encephalitis virus (TBEV) infection in Huacaya alpacas were reported in Austria in 2022, representing the first such cases documented in this species.
Case 1 (Styria)
In spring 2022, an 8-month-old female alpaca developed colic-like signs, bruxism, and ventral recumbency. Despite symptomatic therapy, the animal deteriorated and was euthanized. Histologic examination revealed severe lymphohistiocytic encephalomyelitis in the hippocampus, brainstem, and spinal cord. Immunohistochemistry demonstrated intraneuronal TBEV antigen in numerous neurons, and RNAscope in situ hybridization confirmed viral RNA. RT-qPCR detected TBEV RNA, and sequencing showed >99% identity with European TBEV strains, most closely related to isolates from Switzerland and the Czech Republic. Phylogenetic analysis confirmed infection with the Western subtype of TBEV.
Case 2 (Carinthia)
In early summer 2022, an 8-year-old male alpaca presented with weakness, reduced feed intake, and muscle trembling, progressing to seizures, paresis, and blindness. Postmortem examination showed moderate lymphohistiocytic meningoencephalomyelitis, primarily affecting the brainstem and cervical spinal cord, along with incidental findings of jejunitis and mild parasitic infestation. Immunohistochemistry for TBEV was negative, but RNAscope revealed viral RNA in neuronal cell bodies. RT-qPCR and sequencing confirmed TBEV infection, with genomic sequences closely related to Western subtype strains from Italy, Finland, Belgium, and Germany. Phylogenetic trees indicated that the strains in both alpacas were related but represented distinct reassortants of European TBEV.
Conclusion
These cases demonstrate that TBEV can naturally infect alpacas in endemic regions of Europe, producing progressive neurologic disease. Tick-borne encephalitis should therefore be considered in the differential diagnosis of South American camelids presenting with neurologic signs in such areas.