Urban Populations of Aedes aegypti (Diptera: Culicidae) From Central Argentina: Dispersal Patterns Assessed by Bayesian and Multivariate Methods.

Aedes aegypti (L.), the main vector of dengue and other arboviruses, was declared eradicated from Argentina in 1964; however, in 1987, it was detected again and nowadays it occurs in most of the country territory. To understand the transmission of vector-borne diseases, knowledge of the dispersal of vector populations is essential to evaluate the risk of pathogen transmission. We conducted a population genetic analysis of Ae. aegypti in 20 neighborhoods from Córdoba, the second largest city in Argentina, using 10 microsatellite loci. High genetic differentiation and the absence of an isolation by distance pattern was found using Weir and Cockerham's θ. Bayesian and multivariate clustering analyses showed that the studied sites included individuals with high membership coefficients (Q) in their populations, individuals with membership in another cluster, and admixed individuals. Individuals with high Q in clusters different from the population in which they were collected strongly suggests that passive transport is important in shaping the Ae. aegypti dispersal pattern in Córdoba city. Knowing the genetic structure of Ae. aegypti populations and their dispersal patterns would contribute to the implementation of vector control programs.

Isolation of yellow fever virus from mosquitoes in Misiones province, Argentina.

Yellow fever (YF) is a viral hemorrhagic fever endemic to tropical regions of South America and Africa. From 2007 to 2009 an important epidemic/epizootic of YF was detected in different populations of howler monkeys (Alouatta species) in Misiones, a northeastern Argentinian province. Yellow fever virus (YFV) infection was researched and documented by laboratory tests in humans and in dead Alouatta carayá. The objective of that research was to investigate the circulation of YFV in mosquitoes, which could be implicated in the sylvatic transmission of YF in Argentina. The above-mentioned mosquitoes were captured in the same geographical region where the epizootic took place. A YFV strain was isolated in cell culture from pools of Sabethes albiprivus. This study is not only the first isolation of YFV from mosquitoes in Argentina, but it is also the first YFV isolation reported in the species Sabethes albiprivus, suggesting that this species might be playing a key role in sylvatic YF in Argentina.

Phylogeography of Aedes aegypti in Argentina: long-distance colonization and rapid restoration of fragmented relicts after a continental control campaign.

Aedes (Stegomyia) aegypti, the main vector of Dengue and Yellow Fever viruses, is present in all the northern and central provinces of Argentina. During 2009, a Dengue outbreak spread broadly throughout the country, causing 27,752 infections in 13 provinces. In Argentina, little is known about the demographic history of this vector, which suffered a drastic decrease in abundance and distribution during a major control campaign performed in the Americas between 1950 and 1960. With the aim of uncovering the past and present events that determined the present distribution of the genetic variability in Ae. aegypti populations, we analyzed the distribution and abundance of mitochondrial haplotypes obtained by sequencing a 450-bp fragment of the ND5 gene. We detected 14 haplotypes among the sequences of 197 individuals from 22 populations that cover most of the distribution of the species in Argentina; one population from Bolivia and one from Paraguay were also included. A high heterogeneity in the geographical distribution of the genetic polymorphism was observed, with a pattern of isolation by distance in the north-west of Argentina. Haplotypes nested in three haplogroups, representing different colonization events and evolutionary histories in distant geographical areas. North-western and north-eastern populations correspond to independent introduced stocks for which a past fragmentation and rapid restoration from highly polymorphic relicts were inferred. By contrast, a unique genetic variant was detected in the east, probably as the result of a recent re-colonization event after the major control campaign; in this area, the mosquito would have been practically eradicated as a consequence of the continental control campaign.