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West Nile Virus Infection in Sheep
G Rimoldi1, A Mete2, J M Adaska1
11 California Animal Health and Food Safety Laboratory System, University of California-Davis, Tulare, CA, USA.
Veterinary Pathology
|June 18, 2016
Summary
West Nile virus (WNV) caused neurological disease and encephalitis in 6 sheep in California. This study highlights WNV as a significant cause of viral encephalitis in sheep, with neurological signs and brain lesions confirmed.
Area of Science:
- Veterinary Neurology
- Infectious Diseases
- Arbovirology
Background:
- West Nile virus (WNV) is known to infect various animals, but its impact on small ruminants remains under-documented.
- Neurological signs in sheep can stem from diverse etiologies, necessitating accurate diagnosis.
Purpose of the Study:
- To investigate and confirm West Nile virus as a cause of neurological disease in sheep.
- To characterize the pathological findings and molecular epidemiology of WNV in affected sheep.
Main Methods:
- Diagnostic analysis of sheep with neurological signs between 2002 and 2014.
- Histopathological examination of brain and spinal cord tissues.
- Polymerase chain reaction (PCR) and immunohistochemistry (IHC) for WNV detection.
- WNV RNA sequencing and phylogenetic analysis.
Main Results:
- West Nile virus was diagnosed in 6 sheep exhibiting neurological signs and encephalitis.
- All affected sheep displayed severe lymphoplasmacytic meningoencephalitis; myelitis was noted in 2 cases.
- WNV was confirmed in brain tissue via PCR (6/6) and IHC (5/6).
- Viral antigen was absent in extraneural tissues, and sequenced WNV strains clustered with local mosquito isolates.
Conclusions:
- West Nile virus is a significant cause of viral encephalitis in sheep, presenting with neurological symptoms.
- Neuropathological findings include severe lymphoplasmacytic meningoencephalitis.
- WNV diagnosis in sheep is supported by PCR and IHC on brain tissue, with sequencing aiding in epidemiological linkage.
