Experimental studies to determine the susceptibility to infection with St. Louis encephalitis virus of five species of Panamanian mosquitoes.

The susceptibility to infection with a Panamanian isolate of St. Louis encephalitis (SLE) virus was evaluated in Culex quinquefasciatus, Haemagogus equinus, Mansonia dyari, Sabethes cyaneus and Deinocerites pseudes. When fed on blood-virus suspensions using the hanging drop or pledget technique, the median infective dose (ID50) of SLE virus for colonized strains of Cx. quinquefasciatus and Hg. equinus was 10(2.8) plaque forming units (PFU)/2 microliters and 10(3.5) PFU/2 microliters, respectively. The susceptibility of F1 and F2 Cx. quinquefasciatus females was similar to the colonized strain by the same technique. When fed on viremic chicks, the ID50 for both Cx. quinquefasciatus and Hg. equinus was 10(0.5) PFU/2 microliters. These results and successful transmission trials indicate that both of these species have the potential to serve as vectors of SLE virus in Panama. Because of their poor feeding response, complete susceptibility profiles were not obtained for the other 3 species tested. They appear to be less susceptible than Cx. quinquefasciatus and Hg. equinus, although Ma. dyari was readily infected after engorging on a blood-virus suspension with a titer of 10(3.0) PFU/2 microliters.

[Current situation of the Aedes aegypti mosquito in the metropolitan area of Panama city]. / Situación actual del mósquito Aedes aegypti en el área metropolitana de la ciudad de Panamá.

Ae. aegypti was reintroduced into Panama in 1985; control was unsuccessful and by 1988 Ae. aegypti larvae were detected in every borough of Panama Metropolitan Area. Only 3% of the Panama City population has dengue antibody (against DEN 2) and virtually no one is immune to other serotypes. The relative risk of the introduction of Dengue virus into Panama is discussed.

Transovarial transmission of Gamboa virus in a tropical mosquito, Aedeomyia squamipennis.

We report transovarial transmission of Gamboa virus (Bunyavirus) in Aedeomyia squamipennis, a tropical mosquito which is active and bloodfeeding throughout the year. Gamboa virus was isolated during each of the 28 months of the study from every mosquito stage, including eggs, demonstrating that vertical transmission is a maintenance mechanism of this virus. The overall minimum infection rate was 5.1/1,000 mosquitoes. Identification of the 567 isolates by neutralization indicated that greater than or equal to 2 serotypes or subtypes of Gamboa virus circulate at the study site.