Causes of Death and Detection of Antibodies Against Japanese Encephalitis Virus in Misaki Feral Horses (Equus caballus) in Southern Japan, 2015-17.

The study involved investigating the causes of death and incidence of Japanese encephalitis virus (JEV) antibodies in different animal species, including Misaki feral horses, Japanese wild boars, domestic pigs, and wild Japanese macaques in southern Japan from 2015 to 2017. It was found that a high percentage of these animals have antibodies against JEV, implying that the virus is endemic in the region and these animals can serve as sources of infection.

Postmortem Examinations and Health Conditions

• The researchers carried out postmortem examinations on seven Misaki feral horses and found certain health conditions common in all the animals. These included severe arterial lesions, hemomelasma ilei (blood pigmentation within the small intestine), and poor body condition.
• They also identified occurrences of intestinal ulcers and perihepatitis filamentosa (a disease affecting the liver) which were frequently observed in the horses.
• In addition to these conditions, degenerative arthropathy in the metacarpophalangeal joints was recorded in two cases, while one horse had a rib fracture coupled with a diaphragmatic rupture.

Antibody Detection and JEV Endemicity

• The study involved testing for JEV antibodies using the hemagglutination inhibition (HI) assay, which is a method detecting antibodies against viruses in samples. The presence of these antibodies indicates prior infection with the virus.
• The results revealed that a significant proportion of the tested animals were seropositive for JEV. Specifically, 73% of the horses, 74% of the wild boars, 67% of the domestic pigs, and 29% of the wild monkeys had antibodies against JEV.
• These findings suggest that JEV is endemic in the region, meaning that it is regularly found among the particular animal population in this area of southern Japan.

Infectious Risk Posed By Animals to Humans

• Despite being a danger to animals, the Japanese Encephalitis virus poses a significant risk to humans as well, as they can be infected by consuming infected meat or through the bites of infected mosquitoes. In this study, wild boars and pigs were highlighted as strong amplifiers and sources of the infection, increasing potential risk to humans.
• Consequently, this piece of research underscores the importance of disease surveillance and control measures in animal populations to prevent possible epidemics among humans.