Eastern equine encephalomyelitis in upstate New York: studies of a 1976 epizootic by a modified serologic technique, hemagglutination reduction, for rapid detection of virus infections.

This research discusses an extensive study, conducted during an eastern equine encephalomyelitis (EEE) outbreak in upstate New York during 1976, on how the virus is transmitted and detected. The study highlights a new diagnostic technique that can identify EEE infections in less than 24 hours.

Outbreak and Detection of EEE

• The study was conducted during a large EEE outbreak in upstate New York in the summer of 1976. In total, 37 cases of EEE were confirmed in horses, primarily by virus isolation and serologic examination.
• Apart from horses, other specimens were also collected from the affected area. These collections resulted in 16 additional virus isolates: 9 from mosquito pools, 5 from various bird tissues, and 2 from sentinel pheasants that showed serologic conversions.
• Aside from isolation, the antibodies of EEE were also detected in 81 out of 499 tested wild birds, further expanding the understanding of the spread of this disease.

Implications for Virus Transmission

• The study presents data that implicates three specific bird types – sparrows, cowbirds, and catbirds – as significant contributors to the amplification of the EEE virus. Essentially, these bird species appear to host the virus, facilitating its reproduction and thereby increasing the overall levels of the virus within the surrounding ecosystem.
• Additionally, the data also highlight Culiseta melanura mosquitoes as vectors, or carriers, of the virus among avian populations. This shows the role of these mosquitoes in the transmission process of the EEE virus within bird populations.

Introduction of a New Diagnostic Technique

• An essential contribution of the study is the introduction and successful application of a new serologic technique. This modified technique uses hemagluttination reduction for the rapid detection of virus infections.
• Importantly, this approach proved to be highly reliable in diagnosing EEE, providing results as fast as within 24 hours after the receipt of the field specimens. This level of immediacy in detection is significantly more efficient than prior methods and could prove invaluable in identifying and responding to future outbreaks of EEE.