Japanese encephalitis in a 114-month-old cow: pathological investigation of the affected cow and genetic characterization of Japanese encephalitis virus isolate.
Authors: Kako Naomi, Suzuki Seiji, Sugie Norie, Kato Tomoko, Yanase Tohru, Yamakawa Makoto, Shirafuji Hiroaki
Journal: BMC veterinary research
Summary
Japanese encephalitis virus (JEV), a flavivirus transmitted by mosquitoes, predominantly affects humans and horses but rarely cattle; this case report documents the first confirmed JE infection in a bovine over two years of age, a 114-month-old cow presenting with neurological symptoms in Japan during September 2010. The research team employed virological isolation, complete genome sequencing, phylogenetic analysis, haemagglutination inhibition testing, and histopathological examination to confirm diagnosis and characterise the viral strain, designated JEV/Bo/Aichi/1/2010. The isolated virus belonged to genotype 1 and shared genetic markers—specifically a distinctive deletion in the 3' untranslated region—with JEV strains circulating in nearby Toyama Prefecture between 2007 and 2009, whilst histology revealed nonsuppurative encephalomyelitis with detectable viral antigen in brain tissue. For equine and livestock practitioners in endemic regions, this case extends recognised JE risk across adult cattle populations previously thought relatively resistant to clinical disease, warranting heightened surveillance for neurological presentations in older stock and consideration of JEV in differential diagnoses, particularly during peak mosquito seasons in areas with documented viral circulation.
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Practical Takeaways
- •Japanese encephalitis should be considered in the differential diagnosis of neurological disease in adult cattle, not just young stock, particularly in endemic regions
- •JEV infection can present with nonsuppurative encephalomyelitis; diagnostic confirmation requires virus isolation, antigen detection, and serological testing together
- •Geographic surveillance of JEV strains is important as related genotypes have been identified in specific prefectures over multiple years
Key Findings
- •Japanese encephalitis virus (JEV) genotype 1 was isolated from the cerebrum of a 114-month-old cow with neurological symptoms
- •Histopathological examination revealed nonsuppurative encephalomyelitis with JEV antigen detected in the cerebrum
- •This is the first reported case of Japanese encephalitis in a bovine over 24 months old
- •The isolated JEV strain (JEV/Bo/Aichi/1/2010) was most closely related to JEV G1 isolates from Toyama Prefecture, Japan in 2007-2009