Isoenzyme differentiation of Aedes aegypti populations in French Guiana.

Population genetics of peri-domestic Aedes aegypti (Diptera: Culicidae), vector of dengue and yellow fever, were investigated by gel electrophoresis of 10 enzyme loci in 14 samples of mosquito larvae collected in 1997-1998 from localities separated by distances of 3-275 km in French Guiana. Genetic differentiation between geographical populations was generally high (mean FST = +0.111, P < 10(-5)) even among seven sites <30 km apart (FST = +0.137, P < 0.05), but not positively correlated with distance. Thus, Ae. aegypti comprises a mosaic of genetically differentiated populations in French Guiana. This may be attributed to reinvasion from diverse origins through repeated founder events after this vector species was eliminated during the 1940s to 1960s.

Aedes aegypti in French Guiana: susceptibility to a dengue virus.

Twenty-seven samples of Aedes aegypti (F1 generation) from French Guiana were tested for their susceptibility to dengue serotype 2 virus. Very high infection rates were observed by indirect fluorescent antibody (IFA) test. Ae. aegypti samples were pooled according to two groups: the first group (N=10) represented mosquitoes from the urbanized area of Cayenne and surroundings, and the second group (N=17) corresponded to mosquitoes collected in the countryside. Infection rates were found to be similar in these two cases. These findings are discussed in relation with the history of Ae. aegypti in this part of the world.

[Paul-Louis Simond and yellow fever]. / Paul-Louis Simond et la fièvre jaune.

P.L. Simond participated in the Pasteur Institute mission sent to Rio de Janeiro from 1901 to 1905 to investigate yellow fever and was to make an important contribution to the knowledge of the disease. At that time, the aetiologic agent of yellow fever was still unknown, and its transmission by mosquitoes was controversial. Several authors had observed apparent differences in the susceptibility to the illness between African and European populations. Otherwise, the soundness of epidemic control measures then being administered was often called into question. As such, many points needed to be definitely clarified. During the four years they spent in Brazil, the Pasteur Institute scientists--and particularly Simond--achieved important results. They confirmed the viral aetiology of yellow fever, were able to define several pathological aspects of the disease and conduct various serotherapeutic tests. The role of Aedes aegypti (known at the time as Stegomyia fasciata) was also confirmed and the bionomics of the mosquito began to be studied. This research laid the ground for classical measures of controlling the vector and preventing outbreaks of the disease. Furthermore, Marchoux and Simond observed the vertical transmission of yellow fever virus in Ae. aegypti; this phenomenon of major epidemiological importance remained controversial until it was confirmed in the field as recently as 1997. The French scientists were also able to specify many aspects of the epidemiology of yellow fever, particularly its apparent low pathogenicity in young children--a possible explanation for the fact that local residents of endemic zones often had a certain level of immunity as a result of benign infection contracted in childhood. P.L. Simond later spent several months in Martinique where he set up a successful yellow fever vector control programme. Clearly Simond, who had already acquired much expertise in the epidemiology of vector-borne diseases, played a key role in the success of the mission sent by Institute Pasteur to Brazil, and, more generally, in the scientific advances of yellow fever prevention.

[Comparative study of dengue 2 virus replication and isoenzymes in two strains of Aedes aegypti]. / Etude comparée de la réplication du virus de la dengue 2 et des isoenzymes chez deux souches d'Aedes aegypti.

This study, dealing with two strains of Aedes aegypti from Vietnam and French Guiana, shows the variability of the genes coding for 11 isoenzymatic systems and the replication of the dengue 2 virus in parenterally infected mosquitoes. Slight differences are observed in the characteristics of viral replication. No clear correlation is shown with enzymatic patterns which appear widely different from one strain to the other with four of the enzymes studied.