RESUMO
El municipio Sifontes, ubicado en el noreste del estado Bolívar, constituye el principal foco de malaria de Venezuela. Durante el quinquenio 2010-2014, se registró en el municipio un aumento considerable de la morbilidad con una fuerte tendencia al incremento, cerrando 2014 con la cifra record de 51.603 casos, 58% de la malaria del país en el año. Con el objeto de estudiar la distribución espacial de las larvas de anofelinos en los hábitats acuáticos y su relación con las variables ambientales, se hicieron colectas mensuales de larvas en hábitats representativos de los diferentes tipos existentes en la zona, entre septiembre 2002 y diciembre 2003. El Análisis de Correspondencia Canónica (CANOCO) indica que a nivel de hábitat (humedal), la presencia de las especies de Anopheles está determinada por el tipo y la dinámica hídrica del hábitat, mientras que a nivel de microhábitat (cucharonazo) las especies se ubican a lo largo de un gradiente dominado por el tipo de vegetación, y en menor grado por la luz solar y el color aparente del agua. Esto permitió establecer grupos de especies a priori, tales como las del subgénero Nyssorhynchus, asociadas a la luz solar y a ciertas plantas acuáticas, o las de los subgéneros Anopheles y Stethomyia, An. (Lophopodomyia) squamifemur y Chagasia bonneae asociadas a ambientes sombreados y carentes de vegetación. Los resultados ayudan a comprender mejor la relación de las especies de anofelinos con el medio ambiente y resaltan la importancia de variables como la dinámica hídrica, luz solar, vegetación y color aparente del agua para determinar su ocurrencia en el hábitat acuático.
The Municipality of Sifontes, located in the northeast of Bolivar State, is the main malaria foci in Venezuela. A considerable increase in malaria morbidity was recorded in the Municipality during the decade 2010-2014, with a record figure of 51.603 cases for 2014, 58% of the malaria for the country. In order to study the spatial distribution of anopheline inmature stages in the larval habitats and its relation to environmental variables, monthly collections were carried out in larval habitats representatives of the different types present in the area between September 2002 and December 2003. The Canonic Correspondance Analysis (CANOCO) showed that at the larval habitat level the Anopheles species is determined by the type and dynamics of the habitat, while at the microhabitat level (dip) the species are located along a gradient dominated by the type of vegetation, and in a lesser degree by the exposure to sun light and apparent water color. These allowed to established group of species a priori, such as those of the subgenus Nyssorhynchus associated to sun light and certain aquatic plants, or the subgenus Anopheles and Sthetomyia, An. squamifemur and Chagasia bonneae associated to shaded environments and lack of vegetation. The results help to understand the relationship of anopheline species with the environment and the importance of variables such s water dynamics, sun light, vegetation and water apparent color to determine its occurrence in the larval habitat.
RESUMO
El Municipio Sifontes, ubicado en el noreste del estado Bolívar, Venezuela, constituye uno de los principales focos de malaria del país debido a causas naturales y antrópicas.Durante el decenio 2004-2013, se registró en este municipio un aumento considerable del número de casos, cerrando 2013 con 42.981 casos, 56% de la malaria del país. Con el objeto de describir la dinámica poblacional de las principales especies de anofelinos, en fase pre-adulta, entre septiembre 2002 y diciembre 2003, se hicieron colectas mensuales en cuerpos de agua representativos de los diferentes tipos existentes en el municipio. Anopheles triannulatus Neiva & Pinto sensu lato fue la especie más abundante y ubicua en toda el área de estudio, seguida de An. albitarsis Lynch Arribalzaga s.l., mientras que An. darlingi Root fue encontrada principalmente en lagunas y ríos. La variabilidad estacional en la abundancia larval estuvo condicionada principalmente por la especie de anofelino y el tipo de hábitat que ésta coloniza, de tal forma que el efecto de la lluvia sobre la abundancia de las especies depende de la dinámica hídrica del hábitat larval, si bien en general, la abundancia de larvas tiende a ser mayor durante el periodo de transición lluvia-sequía y sequía. Los resultados de este estudio contribuyen a dilucidar la relación de la dinámica poblacional de los anofelinos con el patrón de lluvias en la región estudiada.
Sifontes Municipality in the north-east of Bolivar State is one of the main malaria foci in Venezuela due to both natural and anthropic factors. Between 2004 and 2013 a significant increase in the number of cases were reported for this region: at the close of 2013, 42.981 cases had been registered representing 56% of the total number of cases reported in the country. Between September 2002 and December 2003 anopheline larvae were collected monthly to study population fluctuations in different habitats representative of the study area. Anopheles triannulatus Neiva & Pinto sensu lato was the most abundant species collected followed by An. albitarsis Lynch Arribalzaga s.l., while An. darlingi Root was mainly found in lagoons and rivers. Seasonal variations in larval abundance were mainly determined by anopheline species and the type of larval habitat exploited by each one. Anopheline species are thus differentially influenced by rainfall according to the water dynamics of their larval habitats, but in general abundance is higher during the transitions between rainfall-drought and the dry season. These results help us to understand the relationships between anopheline population dynamics and rainfall patterns in this region. In addition, they contribute to our basic knowledge of the bio-ecology of anopheline vectors important for the epidemiology, surveillance and control of malaria in Sifontes Municipality.
RESUMO
Anopheles triannulatus s.l. is a malaria vector with a wide geographic distribution, ranging from Argentina-Nicaragua and Trinidad. Here we analysed sequences of two genes, timeless and cpr, to assess the genetic variability and divergence among three sympatric cryptic species of this complex from Salobra, central-western Brazil. The timeless gene sequences did not conclusively differentiate Anopheles halophylus and An. triannulatus species "C". However, a partial separation has been observed between these species and An. triannulatus s.s. Importantly, the analysis of the cpr gene sequences revealed fixed differences, no shared polymorphisms and considerable genetic differentiation among the three species of the An. triannulatus complex. The results confirm that An. triannulatus s.s., An. halophylus and An. triannulatus species C are distinct taxa, with the latter two likely representing a more recent speciation event.
Assuntos
Animais , Feminino , Anopheles , Genes de Insetos , Variação Genética , Insetos Vetores , Análise de Sequência de DNA , Anopheles , Insetos Vetores , Reação em Cadeia da Polimerase , Especificidade da EspécieRESUMO
The Triannulatus Complex of Anopheles (Nyssorhynchus) consists of at least three sibling species, namely Anopheles triannulatus s.s., Anopheles halophylus and a third undescribed member herein referred to as An. triannulatus "C". Sympatric anophelines belonging to species complexes, even though closely related, may exploit different environments such as larval habitats. In this paper we hypothesize that rainfall and seasonal flooding would distinctly influence the availability of larval habitats and consequently the seasonal population dynamics of sympatric members of the Triannulatus Complex. A reflection of this is distinct seasonal biting frequencies exhibited by three members of the Triannulatus Complex at a site in Central Brazil. Population dynamics seem to be influenced by the water level in the local rivers, although biting frequency of all three species was negatively influenced by rainfall. An. triannulatus s.s. was more abundant following the end of the rainy season, but notably 30 to 60 days after flooding. On the other hand, An. halophylus and An. triannulatus C peaked during the middle of the dry season, when water impoundments have no inflow, are somewhat reduced in size and the water becomes brackish. Differences in population dynamics were greater between An. triannulatus s.s. and An. halophylus and An. triannulatus C than between An. halophylus and An. triannulatus C. This might reflect differences in larval habitat exploitation and therefore spatial segregation among these members of the complex.