Peroral susceptibility of Aedes alblifasciatus and Culex pipiens complex mosquitoes (Diptera: Culicidae) from Argentina to western equine encephalitis virus

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 mosquitoes 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 cicle in Argentina

Vector competence experiments with Rocio virus and three mosquito species from the epidemic zone in Brazil

Em condiçöes de laboratório procedeu-se a ensaios visando testar a capacidade vetora para o vírus Rocio, da primeira geraçäo de Psorophora ferox, Aedes scapularis e Aedes serratus obtida a partir de especimens coletados na regiäo epidêmica do Estado de Säo Paulo, Brasil. Psorophora ferox e Aedes scapularis revelaram-se suscetíveis à infecçäo por via oral e capazes de transmitir o vírus mediante a picada após período adequado de incubaçäo. Para as duas espécies, as ID50 orais näo diferiram significativamente. Em Ae. serratus as taxas de infecçäo nunca ultrapassaram os 36,0% o que impossibilitou o cálculo da ID50 para essa espécie. É impossível que Ae. serratus seja vetor epidemiologicamente importante do vírus Rocio. Discute-se a utilidade da técnica de alimentaçäo "in vitro" para demonstrar a transmissäo por mosquitos infectados, e também as dificuldades encontradas ao trabalhar com geraçöes näo colonizadas originárias de especimens coletados no campo