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A densidade e a variação sazonal de flebótomos (Diptera, Psychodidae), vetores de Leishmania, em área urbana da região de Lisboa: repercussões na transmissão vetorial
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Portugal é um país endémico de leishmaniose humana (visceral e cutânea) e canina. As espécies flebotomínicas comprovadamente vetoras de Leishmania infantum são Phlebotomus perniciosus e P. ariasi, e o principal reservatório é o cão. Embora sejam conhecidos vários focos desta zoonose, existem regiões onde nunca se efetuaram estudos referentes aos vetores, ou foram prospetadas há várias décadas.
Sendo Lisboa uma região endémica de leishmaniose, e tendo em conta que a fauna flebotomínica foi estudada pelo Professor Fraga de Azevedo há mais de 70 anos, este trabalho teve como principal objetivo determinar a atual composição flebotomínica, numa Estação em Alcântara, representativa de uma área urbana, com boas condições socioeconómicas, mas com características bioecológicas favoráveis à presença de diferentes espécies flebotomínicas.
De maio a novembro de 2015, durante 3 a 4 noites consecutivas, por semana, capturaram-se, por armadilha luminosa CDC, em biótopos domésticos e peridomésticos, 459 flebótomos, de ambos os sexos, pertencentes a dois géneros e a quato espécies, das cinco assinaladas no País.
Os exemplares capturados foram identificados morfologicamente e a abundância relativa das espécies foi: P. perniciosus 52,1% (239/459), P. ariasi 32,9 % (151/459), P. sergenti 14,6% (67/459) e Sergentomyia minuta 0,4% (2/459). Determinou-se a razão dos sexos, o número de fêmeas grávidas e ingurgitadas, a percentagem de flebotomíneos machos com a genitália externa parcial ou totalmente não rodada, a taxa de infestação por ectoparasitas, a taxa de infeção por endoparasitas não Leishmania e a relação tipo e variedades de biótopos e espécies flebotomínicas presentes.
Quanto à densidade flebotomínica (nº de flebótomos capturados por armadilha, noite), por espécie e por meses de captura, verificou-se uma tendência bifásica, em que as densidades flebotomínicas totais foram mais elevadas em junho (1º pico) e em setembro (2º pico). Em relação à influência das fases lunares nas densidades, o mês de agosto foi o que apresentou maior diferença na fase de Lua Nova.
Da análise de 94 amostras de ADN de flebótomos fêmeas, não se obteve amplificação de ADN de Leishmania com nenhum dos pares de primers utilizados. A identificação da fonte de alimentação sanguínea, por PCR, foi realizada em 17 fêmeas ingurgitadas, das quais 4 alimentaram-se em seres humanos, 8 em galinha, 4 em gato e 1 em coelho.
A presença de P. perniciosus e P. ariasi com maiores abundâncias relativas e densidades, nesta área urbana, mostra que existe não só risco de transmissão vetorial de L. infantum, como também este poderá ser elevado em junho e setembro, uma vez que se verificaram dois picos de eclosão de imagos. Também, neste trabalho, a grande plasticidade trófica do maior vetor, em Portugal, foi demonstrada.
A monitorização desta área, e de outras, deveria ser efetuada, pois verificou-se, que mesmo em áreas urbanas com excelentes condições socioeconómicas, os flebótomos vetores estão presentes e basta haver um cão infetado para que, eventualmente, se desenvolva um microfoco de Leishmaniose, ou mesmo um foco de dimensões mais abrangentes.
Portugal is an endemic country of human and canine leishmaniasis. Phlebotomus perniciosus and P. ariasi are the proven vectors of Leishmania infantum, and the main reservoir is the dog. Although several foci of this zoonosis are known, there are regions where phlebotomine sand flies have never been studied, or were only prospected several decades ago. Lisbon is an endemic area of leishmaniasis, but the last study regarding the sand fly vectors was carried out by Professor Fraga de Azevedo, 70 years ago. The main objective of the present study was to determine the sand fly species fauna, in an urban area of Lisbon city, in a Phlebotomine Station of Alcântara parish. This Station is representative of an urban area with good socio-economic conditions but also with bioecological characteristics favorable to the presence of different phlebotomine species. From May to November 2015, during three to four consecutive nights per week, 459 sand flies, of both gender, belonging to two genera and to four species of the five reported in Portugal, were captured by CDC light traps in domestic and peridomestic biotopes. The captured specimens were identified morphologically and the relative abundance of the species was: P. perniciosus 52.1% (239/459), P. ariasi 32.9 % (151/459), P. sergenti 14.6% (67/459) and Sergentomyia minuta 0.4% (2/459). It was determined the ratio of the sexes, the number of pregnant and engorged females, the percentage of male sand flies with the external genitalia partially or totally not rotated, the infestation rate by ectoparasites, the infection rate by endoparasites other than Leishmania and the relation between the type and variety of biotopes and the phlebotomine species. Regarding the phebotomine densities (number of sand flies captured per trap, per night), by species and by months, there was a biphasic tendency, in which the total density was higher in June (1st peak) and in September (2nd peak). As for the influence of the lunar phases in the total phlebotomine density, August presented the major difference in the new moon phase. Leishmania DNA was not detected by PCR in any of the 94 females. The identification of the blood-meal sources, by PCR, was conducted in 17 engorged females, of which four fed on humans, eight on chicken, four on cats and one on a rabbit. The presence of P. perniciosus and P. ariasi, with higher relative abundances and densities, in this urban area of Lisbon city, shows that there is not only the risk of vectorial transmission of L. infantum, but also that this risk can be higher in June and September, since it was observed two peaks of emerged adults. The results also demonstrated the great trophic plasticity of P. perniciosus. The monitoring of this and other areas should be performed, as it was found that even in an urban area with excellent socio-economic conditions, sand flies vectors can be present and just an infected dog, eventually, is sufficient to develop Leishmania microfocus, or even a focus with broader dimensions.
Portugal is an endemic country of human and canine leishmaniasis. Phlebotomus perniciosus and P. ariasi are the proven vectors of Leishmania infantum, and the main reservoir is the dog. Although several foci of this zoonosis are known, there are regions where phlebotomine sand flies have never been studied, or were only prospected several decades ago. Lisbon is an endemic area of leishmaniasis, but the last study regarding the sand fly vectors was carried out by Professor Fraga de Azevedo, 70 years ago. The main objective of the present study was to determine the sand fly species fauna, in an urban area of Lisbon city, in a Phlebotomine Station of Alcântara parish. This Station is representative of an urban area with good socio-economic conditions but also with bioecological characteristics favorable to the presence of different phlebotomine species. From May to November 2015, during three to four consecutive nights per week, 459 sand flies, of both gender, belonging to two genera and to four species of the five reported in Portugal, were captured by CDC light traps in domestic and peridomestic biotopes. The captured specimens were identified morphologically and the relative abundance of the species was: P. perniciosus 52.1% (239/459), P. ariasi 32.9 % (151/459), P. sergenti 14.6% (67/459) and Sergentomyia minuta 0.4% (2/459). It was determined the ratio of the sexes, the number of pregnant and engorged females, the percentage of male sand flies with the external genitalia partially or totally not rotated, the infestation rate by ectoparasites, the infection rate by endoparasites other than Leishmania and the relation between the type and variety of biotopes and the phlebotomine species. Regarding the phebotomine densities (number of sand flies captured per trap, per night), by species and by months, there was a biphasic tendency, in which the total density was higher in June (1st peak) and in September (2nd peak). As for the influence of the lunar phases in the total phlebotomine density, August presented the major difference in the new moon phase. Leishmania DNA was not detected by PCR in any of the 94 females. The identification of the blood-meal sources, by PCR, was conducted in 17 engorged females, of which four fed on humans, eight on chicken, four on cats and one on a rabbit. The presence of P. perniciosus and P. ariasi, with higher relative abundances and densities, in this urban area of Lisbon city, shows that there is not only the risk of vectorial transmission of L. infantum, but also that this risk can be higher in June and September, since it was observed two peaks of emerged adults. The results also demonstrated the great trophic plasticity of P. perniciosus. The monitoring of this and other areas should be performed, as it was found that even in an urban area with excellent socio-economic conditions, sand flies vectors can be present and just an infected dog, eventually, is sufficient to develop Leishmania microfocus, or even a focus with broader dimensions.
Descrição
Palavras-chave
Flebotomíneos Leishmania Densidades Refeições sanguíneas Lisboa Parasitologia médica
Contexto Educativo
Citação
Editora
Instituto de Higiene e Medicina Tropical