Abstract
The transmission cycle of western equine encephalitis (WEE) virus in South America is unknown. A WEE virus strain was isolated from Aedes albifasciatus in Argentina during the WEE epizootic of 1982-83. Also, Culex pipiens from Argentina was reported to be able to transmit WEE virus experimentally, but other results indicate that Cx. pipiens from the USA is refractory to this virus. We determined the susceptibility of Argentina strains of Ae. albifasciatus and Culex pipiens complex mosquitos to infection by WEE virus by the oral route. Adult females were fed on chicks infected with a WEE virus strain isolated in Cordoba Province, Argentina, or were fed on a blood/virus suspension. Each mosquito ingested between 10(1.6) to 10(6.4) vero cell plaque-forming units of virus. Each of 28 Ae. albifasciatus was positive for virus from the fourth day postfeeding, and there was evidence for virus replication. In contrast, 0/44 Cx. p. quinquefasciatus and only 1/15 Cx. p. pipiens was positive. Aedes albifasciatus is susceptible to infection by WEE virus and should be considered a potential vector of this virus in Argentina. Both subspecies of Cx. pipiens are refractory to peroral infection by WEE virus and probably do not play a role in the WEE virus cycle in Argentina.
Highlights
Western equine encephalitis (WEE) virus causes epidemics and epizootics in North and South America
Culex pipiens from Argentina was reported to be able to transmit WEE virus experimentally, but other results indicate that Cx. pipiens from the USA is refractory to this virus
One hundred and forty-nine thousand mosquitoes collected in Santa Fe Province during the large WEE epizootic of 1982-83, yielded four WEE virus strains from Ae. albifasciatus, Anopheles albitarsis, Mansonia species and Psorophora pallescens[13]
Summary
Western equine encephalitis (WEE) virus causes epidemics and epizootics in North and South America. In South America, severe aperiodic equine epizootics have been recognized since 1908 in the temperate zone of Argentina and Uruguay, limited outbreaks in humans have been reported only in Southern Argentina[16]. In these areas the natural transmission cycle is unknown. One hundred and forty-nine thousand mosquitoes collected in Santa Fe Province during the large WEE epizootic of 1982-83, yielded four WEE virus strains from Ae. albifasciatus, Anopheles albitarsis, Mansonia species and Psorophora pallescens[13]. In the south, where human cases had occurred, 474 mosquitoes (70% Ae. albifasciatus and 30% Cx. species) were tested for virus with negative results
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