Genetic evidence of expansion by passive transport of Aedes (Stegomyia) aegypti in Eastern Argentina

Abstract

Aedes (Stegomyia) aegypti (Linnaeus) (Diptera: Culicidae) is the principal vector of the Yellow Fever virus, the Dengue virus serotypes, Chikungunya virus and several types of Encephalitis. The behavior of this species is strictly synanthropic and anthropophilic, and it is the culicid most closely associated with human populations. In March 2011 and 2012 our group reported a new biogeographical record of A. aegypti in the southeast of Argentina. In order to determine the origin of the A. aegypti population?s distribution present in this new expansion area, we analyzed the mitochondrial lineages of these mosquito populations and compared their haplotypes with the haplotypes previously determined by Albrieu Llinás and Gardenal (2012) in Argentina and neighboring countries. The sampling stations were cemeteries and used tires located in towns next to the Provincial Route No 2 and in Buenos Aires city, La Plata (both at 400 km north from Mar del Plata) and San Clemente del Tuyú, a small town located on the Atlantic coast at 328 km south from Buenos Aires city, where this mosquito species was found for the first time. A 450 bp fragment of the ND5 gene was amplified by the polymerase chain reaction from a DNA extraction of each single larva. DNA sequences were identified and the haplotype frequencies for each population were calculated. In this work we report the presence of only two haplotypes in the new distribution area. H1 haplotype was detected in all localities analyzed, while H2 was only in two localities. According to our results only passive migration through human transport may explain the observed patterns, demonstrating once again the urgent need to implement serious campaigns to control vector mosquitoes and consequently the development of responsible control campaigns of the mosquito-borne diseases.