Equine Encephalomyelitis: Its Relationship to Man in California.

The research article discusses an investigation of equine encephalomyelitis or horse brain inflammation and its potential, though rare, transmission to humans in California during the early 20th century.

Background and Context

• The paper starts by referring to a disease outbreak that occurred in horses in California’s San Joaquin Valley during the summer of 1930. The disease, identified as an acute infection of the central nervous system, resulted in the deaths of approximately 47 per cent of the 6,000 affected horses between 1930 and 1932.
• The disease was caused by a virus, which was recovered and identified by the researchers. Despite the large scale of the epidemic among horses, the human cases were very few. Only three cases were reported, of which one was fatal and two managed to recover.
• The human victims were all close to the infected horses; they included veterinarians or people closely interacting with the sick animals. Despite this association, no virus was identified in the human victims.

Endemic Disease and Declining Numbers

• Further, the article mentions that the equine disease appears to be endemic, or frequently found in, both the Sacramento and the San Joaquin valleys. Nevertheless, the number of affected animals seemed to have decreased considerably in recent years.
• Despite the decline in reported cases among animals, the disease was not initially suspected when an outbreak of acute encephalitis (inflammation of the brain) was reported in humans during the summer and autumn of 1937. The epidemic was particularly high in Fresno County with a morbidity rate of 42.8 per cent; about 102 cases of acute encephalitis among humans were reported statewide.

Implication and Conclusion

• This implies that there might be a link between equine encephalomyelitis and human encephalitis cases, particularly among those who may have had close contact with sick horses. However, without identifying the virus in human victims, it remains difficult for the researchers to conclusively establish this
• In final analysis, the research posits a potential (albeit infrequent) zoonotic transmission of equine encephalomyelitis to humans, albeit with high mortality rates. The research underscores the need for further exploration of the causal relationship between equine encephalomyelitis and human cases of acute encephalitis, and the development of effective strategies to prevent such transmissions.