Arbovirus isolations from mosquitoes collected during and after the 1982-1983 epizootic of western equine encephalitis in Argentina.

This research paper examines the number of arboviruses, specifically the Western equine encephalitis virus, isolated from mosquitoes in Argentina during the 1982-1983 epidemic and afterwards. Researchers were also interested in the vector relationships of each virus isolated.

Study Setting and Data Collection

• The study involved collecting mosquitoes in two provinces of Argentina, Santa Fe and Rio Negro, in 1982-1983 during an outbreak of Western equine encephalitis (WEE) and also in the spring and summer of 1983-1984 subsequent to the outbreak.
• According to the records, a total of 153,084 mosquitoes were collected from Santa Fe Province and 484 from Rio Negro Province during the outbreak. While after the outbreak, the collection figures were 49,707 mosquitoes from Santa Fe, 15,961 from Rio Negro, and 2,019 from Chubut provinces.
• The collected mosquitoes were then grouped into 2,351 pools and tested for the presence of the virus.

Findings of the Study

• During the epidemic, seventeen virus strains were isolated, all of which were found in the mosquito samples from Santa Fe. The strains included 4 WEE, 6 Venezuelan equine encephalitis, 1 St. Louis encephalitis, 2 Antequera, 1 Maguari, 1 Melao, 1 new vesiculovirus (Calchaqui), and 1 Gamboa.
• The WEE virus strains were specifically found in the Aedes albifasciatus, Anopheles albitarsis, Mansonia species, and Psorophora pallescens types of mosquitoes.
• After the epidemic, 22 more virus strains were detected, with all being found in mosquitoes from Santa Fe. The detected strains were 3 St. Louis Encephalitis (SLE) virus and 19 Turlock (TUR) virus strains.
• An interesting fact that emerged from the study was that except for one, all of the TUR virus isolates seem to have come from mosquitoes that had fed on a viremic chicken before getting caught in the bait trap.

Discussion

• Vector relationships for each of these viruses relative to the initial epizootic were analysed and discussed. The term ‘vector relationship’ refers to the relationship of the virus with the mosquitoes that carry them and transmit them to other organisms. Understanding these relationships is crucial for disease control and prevention.