[Post-epizootic activity of Western equine encephalitis virus in Argentina].

This research focuses on exploring the post-epizootic activity of the Western equine encephalitis virus (WEE) in Argentina during the period between 1983 and 1986. The observation was conducted via a surveillance system and the detection of the disease in horses and humans was noted.

Research Methodology and Findings

• The researchers employed a combination of two methods for their surveillance system: the reporting of equine cases and the deployment of sentinel animals. Their surveillance covered the provinces of Córdoba and Santa Fe between September 1983 and September 1985.
• Of the 16 horses that fell ill within the study period, five were confirmed to have the WEE virus as identified via a hemagglutination inhibition test, which is a serological test designed to identify viruses and bacteria. These five cases constituted the thirteen equine focuses that were reported throughout the timeframe.
• The researchers also evaluated 28 human cases that were reported within the same timeframe, but the WEE virus was not confirmed in any of these cases.
• Antibodies against the WEE virus, otherwise known as neutralizing antibodies (Ac NT), were prevalent among the sentinel horses in both provinces. However, their prevalence in Córdoba Province (4%) was lower than that in Santa Fe Province (13%) in April 1984.
• In Santa Fe Province, the Ac NT disappeared within a year in 40% of the horses observed.
• A number of seroconversions in both provinces were recorded over the study period. Specifically, there were two seroconversions in Córdoba from December 1983 to April 1986, and nine in Santa Fe from February 1984 to July 1986. These seroconversions indicate transitions from being antibody-negative to antibody-positive, which is typically interpreted as the individual’s immune system producing an immune response to a specific infection.

Conclusions and Implications

• Despite the known cross-antigenicity between the WEE virus and another virus labeled as WEE AG 80-646, the presence of antibodies in one of the sentinel horses from Córdoba Province was attributed to the WEE virus.
• No presence of the WEE virus was detected in domestic birds within the study period.
• With these findings, the researchers managed to observe and document one full cycle of the WEE virus, from its pre-epizootic phase (1977-1980), through its epizootic phase (1982-1983), and finally to its post-epizootic phase including residual focus and inapparent infections (1983-1986).