Monitoring of Lutzomyia longipalpis Lutz & Neiva, 1912 in an area of intense transmission of visceral leishmaniasis in Rio Grande do Norte, Northeast Brazil

Abstract

Urban increase of visceral leishmaniasis (VL) in Brazil is associated with the adaptation of its vector, Lutzomyia longipalpis, to environments modified by humans. The present study reports the results of an entomological monitoring of L. longipalpis and the effect of environmental variables on its population density. Sandflies were captured in the municipality of Mossoró, State of Rio Grande do Norte, Northeastern Brazil, from January 2005 to December 2006. Two CDC light traps were placed monthly for four consecutive nights in the peridomicile of selected households. Data analysis was based on the chi-square test and linear regression. A total of 2,087 sandflies were captured, 99.86% of which were L. longipalpis. A higher proportion of females were captured (p < 0.05). Monthly analysis of the variables temperature, relative humidity and rainfall did not show a significant influence on population density. However, there were seasonal differences: approximately 70% of sand flies were captured during the rainy season (p < 0.05). The predominant species, L. longipalpis, is present in substantial number, representing a public health risk. Therefore, because of higher prevalence during the rainy season, we recommend intensified VL control measures before and during this season to reduce the risk of disease transmission.Keywords: Lutzomyia longipalpis, seasonality, epidemiology, vector control, visceral leishmaniasis. ResumoNo Brasil, o crescimento urbano da leishmaniose visceral (LV) está associado com a adaptação do seu vetor, Lutzomyia longipalpis, aos ambientes modificados pelo homem. Este estudo relata a vigilância entomológica de L. longipalpis e os efeitos das variáveis ambientais sobre a sua densidade populacional. Os flebotomíneos foram capturados no município de Mossoró, Rio Grande do Norte, no Nordeste do Brasil, a partir de janeiro de 2005 a dezembro de 2006. Duas armadilhas tipo CDC foram colocadas mensalmente durante quatro noites consecutivas no peridomicílio das casas escolhidas. A análise dos dados foi baseada no teste Qui-quadrado e regressão linear. Um total de 2.087 flebotomíneos foram capturados, dos quais 99,86% foram L. longipalpis. Mais fêmeas do que machos foram capturados (p < 0,05). Na análise mensal das variáveis ambientais a temperatura, umidade relativa e a chuva não tiveram impacto significativo sobre a densidade populacional de L. longipalpis. No entanto, houve diferenças sazonais: aproximadamente 70% dos flebotomíneos foram capturados durante a estação chuvosa (p < 0,05). Assim, L. longipalpis, a espécie predominante, representa um risco à saúde pública. Portanto, devido à maior prevalência no período chuvoso, recomendamos intensificar as medidas de controle da LV antes e durante este período para reduzir o risco de transmissão da doença.Palavras-chave: Lutzomyia longipalpis, sazonalidade, epidemiologia, controle vetorial, leishmaniose visceral.

Sandflies (Psychodidae: Phlebotominae) survey in an urban transmission area of visceral leishmaniasis, Northeastern Brazil

“…These conditions are known to favor the presence of L. longipalpis (MICHALSKY et al, 2009), the predominant phlebotomine species in the city. Similar results were found in a previous monitoring survey by the same research group (AMÓRA et al, 2010).…”

“…The significantly higher proportion of sand flies in the peridomicile was also reported in other municipalities in Rio Grande do Norte (XIMENES et al, 2000(XIMENES et al, , 2007, in the city of Mossoró, as mentioned earlier (AMÓRA et al, 2010), and in Montes Claros, state of Minas Gerais, southeastern Brazil, where sand flies were captured near domestic animals (MONTEIRO et al, 2005). These findings can be explained by the devastation of large wild areas for economic exploration, bringing the disease to the periphery of urban centers.…”

“…The same was seen in 30 other municipalities in the State of Rio Grande do Norte, where L. longipalpis remains prevalent (XIMENES et al 1999(XIMENES et al , 2000QUEIROZ et al, 2009;AMÓRA et al, 2010). This finding maybe related to male predominance in L. evandroi populations and/or that this species is still in process of adaptation with flies preferably feeding on wild animals (XIMENES et al, 1999;QUEIROZ et al, 2009).…”

Spatial and seasonal distribution of Lutzomyia longipalpis in Dracena, a city in the western region of the State of São Paulo, Brazil, that is endemic with visceral leishmaniasis

“…Moreover, in northeastern Brazil, where temperatures vary little throughout the year, the greater abundance of the vector occurs during the rainy season, which ranges from June to August 10,11,31 . In other studies performed in the cities of Porteirinha 23 and Montes Claros 25 , both of which are located in Minas Gerais in southeastern Brazil, the rainfall and the temperature were considered to be predictors of vector abundance.…”

Awareness of visceral leishmaniasis and its relationship to canine infection in riverside endemic areas in Northeastern Brazil

“…Previous studies have demonstrated the relationship between environmental variables and the density of vectors 7,8 ; in particular, areas that fl ood during the rainy season due to their proximity to rivers are more vulnerable to VL because they have a higher insect density, particularly around homes 9 .…”