Confirmed case of encephalitis caused by Murray Valley encephalitis virus infection in a horse.

The research details a confirmed case of encephalitis in a horse caused by the Murray Valley encephalitis virus, observed in Queensland, Australia. The horse exhibited neurological symptoms and was consequently euthanized, with brain and spinal examinations revealing subacute, nonsuppurative encephalomyelitis.

Encephalitis in Horse

• The study focuses on a 5-year-old Australian stock horse from Monto, Queensland that manifested neurological signs of illness. The horse was euthanized after six days of illness.
• Upon examination, histological findings from the horse’s brain and spinal cord indicated moderate to severe subacute, nonsuppurative encephalomyelitis, a condition characterized by inflammation caused by non-draining (nonsuppurative) nervous system infection.

Flavivirus Identification

• Using immunohistochemistry with a flavivirus-specific monoclonal antibody, sections of the horse’s spinal cord rendered positive results.
• A Reverse transcription polymerase chain reaction (RT-PCR) assay, specifically targeting the envelope gene of flavivirus, also yielded positive results. RT-PCR testing was conducted on the horse’s brain, spinal cord, cerebrospinal fluid, and facial nerve.
• Isolation of a flavivirus came from the horse’s cerebrum and spinal cord. Once isolated, the virus was compared to those in database GenBank using its nucleotide sequences.

Murray Valley Encephalitis Virus Identification

• In comparison to those in GenBank, the nucleotide sequences deduced from the virus shared identity of 96-98% with the Murray Valley encephalitis virus, confirming the identification of the virus.
• Additionally, the research found the partial envelope gene sequence of the viral isolate belonged to genotype 1, showing closest relation with a previous isolate from Queensland. This further verifies the identity of the virus and shows possible genetic similarity or evolutionary relation with other instances of the virus in the region.

Conclusion

• The study concludes with a significant discovery of Murray Valley encephalitis virus infecting a horse, which was made through careful examination of the horse’s brain and spinal cord, coupled with advanced genetic examination techniques. This contributes to existing knowledge about the types of hosts and geographical distribution of this virus.