Seasonal dynamics of Aedes aegypti (Diptera: Culicidae) in the northernmost state of Brazil: a likely port-of-entry for dengue virus 4

Abstract

The highest infestation rates occurred during the peak of the rainy seasons, but a large presence was also observed during the early dry season (although with more variation among years). Spatial distribution of positive houses changed from a sparse and local pattern to a very dense pattern during the dry-wet season transition. These results suggest that the risk of dengue transmission and the potential for the new serotype invasions are high for most of the year.Key words: Aedes aegypti -dengue fever -ovitraps -seasonality -Amazon Separated from the rest of country by the Amazonian Forest, Roraima (RR) is the most isolated state in Brazil. Boa Vista, its capital, is a medium-sized city (249,853 inhabitants) (IBGE 2008a) located in the middle of a sparsely populated savannah. A highway is the only paved interstate route, connecting Boa Vista to the city of Manaus 805 km to the south and the Venezuelan border 220 km to the north. Despite its isolation, Boa Vista (and RR as a whole) has received -and continues to receive -a large inflow of visitors and migrants from Venezuela, Guyana and the Caribbean countries, as well as migrants from other regions of Brazil. As a consequence, RR's population increased from 79,400 inhabitants in 1980 to 395,725 inhabitants in 2008, a 5-fold increase in fewer than 30 years. Today, 53.7% of RR's population are immigrants, the highest proportion observed in Brazil (IBGEb 2008).The first dengue fever epidemic in Brazil after the re-invasion by Aedes aegypti occurred in Boa Vista in 1981-1982 with 11,000 reported cases (Osanai et al. 1983, Travassos-da-Rosa et al. 1998. DENV-1 and DENV-4 were isolated. For four years prior to this, DENV-1 was spreading throughout the Caribbean Islands, Central America and Northern South America (Moros et al. 2003, Uzcategui et al. 2003. The year 1981 also marked the arrival of DENV-4 in the Americas (Lanciotti et al. 1997). In Boa Vista, this first invasion was interrupted through vector control programs and the country was spared any new dengue invasions until 1986, when DENV-1 arrived in Rio de Janeiro, triggering nationwide epidemics (Nogueira et al. 2007). Dengue fever has become an endemic disease in Brazil, with the cocirculation of DENV-1, DENV-2 and DENV-3 in most of the 27 Brazilian states. DENV-4 did not persist in Brazil after RR's 1981-1982 outbreak (Nogueira et al. 2007). For several years now, RR has consistently had one of the highest dengue incidence rates among Brazilian states. In 2007, RR registered an incidence rate of 594.8 cases per 10,000 inhabitants. This was the highest rate after Amapá (877.7), Tocantins (TO) (1415.3) and Mato Grosso do Sul (MS) (3213). In 2006, the incidence rate in RR was 657.8, highest after MS (688.3) and TO (665.7) (MS 2007).Ae. aegypti in Boa Vista, RR • Cláudia Torres Codeço et al. 615Its proximity to Venezuela, where all four dengue serotypes are found, and appropriate vector and climate conditions for dengue transmission, make Boa Vista a strategic point for dengue surveillance in Brazil. Despite th...

Genetic Diversity of Brazilian Aedes aegypti: Patterns following an Eradication Program

“…The first genetic group identified suggests that mosquitoes from Venezuela and possibly the USA have contributed to the northern Brazilian population. Venezuela seems to be an important source of mosquitoes as well as dengue virus serotypes into Brazil [56]–[58]. Indeed, Silva et al [59], also using the mitochondrial ND4 gene, have found that populations from the Northern states in Brazil seemed to be similar to those from Venezuela and Peru.…”

Gene flow networks among American Aedes aegypti populations

“…2004; Figueiredo et al. 2008; Codeço et al. 2009), and river connection between Peru and the Brazilian Amazon is supported by pupae surveys on boats (Morrison et al.…”

A ocorrência da dengue e variações meteorológicas no Brasil: revisão sistemática

“…Many studies that employed entomological surveys 22,23,26,29,[37][38][39] have shown higher values of infestation of eggs, larvae and vectors in the rainy period; however, the positive breeding sites persist in the drought period, a fact that is favored by the mosquito's facility to adapt to the human environment, through natural and/or artificial reservoirs 31,34,40,41 . The rainfall data referring to the months of highest number of notification of cases showed a slight relationship among one another.…”