[Study of the vectorial competence of Lutzomyia intermedia (Lutz & Neiva, 1912) for Leishmania (Viannia) braziliensis, Vianna, 1911]

Updating Ecological and Behavioral Aspects of the Sandfly Fauna in the Vale do Ribeira Region, São Paulo State, Brazil

Simple Summary

Analyzing the biological and ecological characteristics of arthropods constitutes the basis for the entomological surveillance of vector-borne diseases. This is accomplished in order to implement vector surveillance and control programs. Thus, with the objective to update the distribution of sandflies in the main transmission region of cutaneous leishmaniasis in the state of São Paulo, we carried out a study of fauna in a modified environment, considering its environmental characteristics and climatic variables. Ecological indices such as richness, abundance, diversity, and equitability of the sandfly fauna in the region are presented.

Abstract

Some ecological parameters and the distribution of vectors in the municipality of Eldorado, Vale do Ribeira Region, São Paulo, were studied. Entomological surveys were carried out from September 2019 to March 2021. It was observed that a few ecological parameters, including richness, abundance, diversity, and equitability, were typical of a modified environment, where artificial ecotopes maintain the presence of sandflies throughout the year. A total of 11,668 sandflies were captured. The presence of five taxa were observed in Eldorado, with low diversity and high dominance of Nyssomyia intermedia next to Ny. neivai, which are sympatric species. The results presented reinforce the importance of these species in anthropized areas in the transmission of cutaneous leishmaniasis (CL) agents and the need for entomological monitoring. Psathyromyia pascalei was encountered for the first time in the municipality, expanding the known area of distribution of this species in a modified environment.

Occurrence of Phlebotominae (Diptera: Psychodidae) in Urban Leishmaniasis Transmission Foci in North-Eastern Brazil

In this study, we analyzed species composition, richness, and monthly and seasonal abundance of sand flies in an urban area, municipality Caxias, state Maranhão, endemic for American visceral and tegumentary leishmaniasis. Sand flies were caught using Center for Disease Control (CDC) light traps in peridomicile (animal shelter) and extradomicile (forest) environments twice a month for 1 yr. A total of 16,332 specimens belonging to 20 species were captured. The predominant species identified in this study were Lutzomyia longipalpis (Diptera: Psychodidae) (Lutz and Neiva 1912) (43.08%) and Lutzomyia whitmani (Diptera: Psychodidae) (Antunes and Coutinho 1939) (43.02%), which occurred throughout the year (every month). The highest abundance of phlebotomine was recorded during the dry season (53.75%) and in the urban peridomicile environment (59.1%), wherein 17 species were found. In the study area, L. longipalpis and L. whitmani are reported to be effective visceral or tegumentary leishmaniasis vectors, respectively, due to their abundance throughout the year.

Molecular detection of the blood meal source of sand flies (Diptera: Psychodidae) in a transmission area of American cutaneous leishmaniasis, Paraná State, Brazil

The feeding behavior of sand flies provides valuable information about the vector/host interactions and elucidates the epidemiological patterns of American cutaneous leishmaniasis (ACL) transmission. The aim of this study was to identify the blood meal sources of sand flies in endemic areas of leishmaniasis in Paraná State through polymerase chain reaction (PCR) amplification of a prepronociceptin (PNOC) gene fragment and its subsequent DNA sequencing. Moreover, molecular assays were conducted to evaluate the sensitivity and reproducibility of the PNOC gene amplification. Besides that, a time-course digestion test of the blood using sand flies that fed artificially on BALB/c mice was performed. Of 1263 female sand flies collected in the field, 93 (3.6%) specimens were engorged and 27 allowed efficient amplification of the PNOC gene. These flies had fed on equine (Equus caballus), porcine (Sus scrofa) and canine (Canis lupus familiaris) species. The results also showed that the identification of the blood meal sources of the sand flies using the molecular method was directly linked to the level of digestion of the blood (time-course) and not to the amount of blood that had been ingested or to the presence of inhibitors in the blood.

Host-biting rate and susceptibility of some suspected vectors to Leishmania braziliensis

BACKGROUND

American tegumentary leishmaniasis is a serious Brazilian public health problem. This diseases is attributed to seven species of Leishmania, however, the majority of cases are associated with Leishmania braziliensis. Some phlebotomine species have been implicated in the transmission of this parasite, nonetheless only Psychodopygus wellcomei has had its vectorial competence demonstrated. Thus this study sought to assess some parameters related to the vectorial capacity of anthropophilic species of sand fly occurring in São Paulo state: Pintomyia fischeri, Migonemyia migonei Nyssomyia intermedia, Nyssomyia whitmani, Expapillata firmatoi and Psychodopygus ayrozai, under laboratory conditions. These parameters were the duration of the gonotrophic cycle, proportion of females which feed on hamster, the rate of infection by L. braziliensis and the duration of the extrinsic incubation period.

METHODS

The sandflies were collected in three regions of the São Paulo state: Greater São Paulo and the Mogi Guaçu and Iporanga municipalities. To assess the proportion of engorged females the insects were fed on hamsters to estimate the duration of the gonotrophic cycle. To estimate the susceptibility to infection of each species, their females were fed on hamsters infected with Leishmania braziliensis and dissected to ascertain the localization of the flagellates and estimate the extrinsic incubation period.

RESULTS

Low hamster attractiveness to Ps. ayrozai was observed. A high proportion of engorged females was observed when the hamster had its whole body exposed. The gonotrophic cycle ranged between three and eight days. Mg. migonei, Pi. fischeri, Ny. neivai, Ny. intermedia, Ny. whitmani and Ex.firmatoi presented susceptibility to infection by L. braziliensis. The highest infection rate (34.4%) was observed for Ny. whitmani and the lowest for Ny. intermedia (6.6%). Mg. migonei presented late-stage infection forms on the fifth day after feeding, but in the other species these forms were observed as from the fourth day.

CONCLUSIONS

Our results, together with other parameters of their behavior under natural conditions, suggest the potential role of Ex. firmatoi as vector of this parasite and reinforce that of Mg. migonei, Pi. fischeri, Ny. neivai, Ny. intermedia and Ny. whitmani in the areas in which they occur.

Avaliação de medidas de controle de flebotomíneos

Realizou-se coletas de flebotomíneos de maio de 2005 a abril de 2006. Os resultados foram comparados com os das coletas realizadas entre abril de 2001 e setembro de 2002, para avaliar as medidas empregadas para diminuir a densidade destes insetos, no Recanto Marista, município de Doutor Camargo, Estado do Paraná. As coletas foram feitas com armadilhas de Falcão, em domicílios e galinheiros, das 22 às 2 horas, semanalmente, quatro vezes ao mês. Em 2005 e 2006, coletaram-se 213.195 flebotomíneos, 1.113,8 em média por hora (MH) e em 2001 e 2002, 199.821 (MH=1.653,5). Nyssomyia neivai prevaleceu (75,4%) em todos os ecótopos que, juntamente com Nyssomyia whitmani (23,4%), Migonemyia migonei (0,8%) e Pintomyia fischeri (0,4%), representaram 99,7% do total coletado. Nos ecótopos representados por galinheiros foram coletados 88,7% dos flebotomíneos. Constatou-se que houve queda na densidade de flebotomíneos no período de coletas 2005 e 2006 em relação à de 2001 e 2002, especialmente no domicílio.

Pesquisa de infecção natural de flebotomíneos por Leishmania, no Estado do Paraná

A leishmaniose tegumentar americana tem sido notificada em todos os estados do Brasil e no Paraná essa doença é endêmica. O objetivo deste trabalho foi detectar a infecção natural de flebotomíneos para verificar a competência vetorial destes insetos e a identificação da espécie parasitária. Os flebotomíneos foram coletados com armadilhas de Falcão e Shannon, nos municípios de Doutor Camargo, Fênix e Mandaguari, de novembro de 2005 a agosto de 2006. Coletaram-se 12.930 flebotomíneos, dos quais 2.487 fêmeas foram dissecadas e destes 1.230 fêmeas foram submetidas à reação em cadeia da polimerase. Pelo método da dissecação, foi detectada uma fêmea de Nyssomyia whitmani com infecção natural por flagelados e pela reação em cadeia da polimerase não se detectou a presença de DNA de Leishmania em nenhuma das fêmeas. Apesar de não ter sido detectada a infecção natural de Nyssomyia neivai nas localidades em apreço e ainda que os requisitos de incriminação vetorial não tenham sido atendidos, não se deve negligenciar o potencial vetorial desta espécie.

Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) (Diptera: Psychodidae: Phlebotominae) geographical distribution and epidemiological importance

Nyssomyia intermedia (Lutz & Neiva 1912) and N. neivai (Pinto 1926) are possible vectors of tegumentary leishmaniasis in some regions of Brazil. Further, the latter was until recently, considered a junior synonym of the former. This study has the purpose of updating our knowledge of the geographical distribution of these species, based on specimens deposited at the collection of the Centro de Pesquisas René Rachou-Fiocruz, Faculdade de Saúde Pública-Universidade de São Paulo, and on data presented by literature as also to associate this distribution with the cutaneous leishmaniasis cases reported. It has been reported that N. intermedia occurs in the states of the Northeastern Region, in Rio de Janeiro, Espírito Santo, on the northern coast of São Paulo, in eastern Minas Gerais, Mato Grosso do Sul, and Goiás, close to the border with Minas Gerais and Bahia. N. neivai occurs in the Southern Region, southern coast and in western São Paulo, southern and western Minas Gerais, southern Goiás, and southern Pará, beyond Argentina, Bolivia, and Paraguay. It is important to highlight that N. intermedia and N. neivai occur in sympatry in Minas Gerais and São Paulo. N. intermedia or N. neivai are predominant or are captured abundantly in several cutaneous leishmaniasis foci in the Southeastern and Southern regions of Brazil.

Padronização de condições para detecção de DNA de Leishmania spp. em flebotomíneos (Diptera, Psychodidae) pela reação em cadeia da polimerase

A correta identificação dos agentes etiológicos em insetos vetores é de crucial importância aos estudos epidemiológicos. A pesquisa de flagelado nesses vetores, pela dissecção de seu trato digestivo, observação microscópica do seu conteúdo ou por isolamento dos parasitas provenientes de insetos em meios de cultura, tem-se mostrado operacionalmente inadequada e com baixa especificidade do diagnóstico, pois fêmeas de flebotomíneos também podem albergar outros flagelados como Trypanosoma e Endotrypanum. Acreditamos que por sua eficiência e especificidade, a amplificação de seqüências-alvo do DNA da Leishmania, por meio da reação em cadeia de polimerase, pode ser aplicada na investigação de sua presença em flebotomíneos, desde que estes estejam devidamente acondicionados e o DNA do parasita extraído a partir de metodologia adequada. Este trabalho descreve metodologias utilizadas na padronização da conservação dos espécimes de flebotomíneos e extração do DNA da Leishmania como uma alternativa mais prática que os métodos tradicionais.

Avaliação de medidas de controle de flebotomíneos no Município de Lobato, Estado do Paraná, Sul do Brasil

Avaliam-se medidas de controle de flebotomíneos no Município de Lobato, Estado do Paraná, Brasil. Esses insetos foram coletados com armadilhas de Falcão em residências, num curral e na mata, de julho a novembro de 1999 e de fevereiro a junho de 2000. Em dezembro de 1999 e janeiro de 2000, foram utilizadas as seguintes medidas na tentativa de diminuir a densidade de flebotomíneos no peridomicílio e domicílio: (i) as janelas das edificações (residências, alojamento, refeitório) foram teladas; (ii) todo tipo de matéria orgânica existente na área peridomiciliar foi retirada, e as edificações foram desinsetizadas. Nyssomyia whitmani, Pintomyia fischeri, P. monticola e Brumptomyia brumpti predominaram no primeiro período de coletas, enquanto N. neivai, Migonemyia migonei e N. pessoai predominaram no segundo. No primeiro período, a maioria dos flebotomíneos foi coletada na mata, e no segundo, nas residências. Não houve diferença entre o número de flebotomíneos coletados no primeiro período e no segundo. Esses resultados mostram uma possível frustração das medidas empregadas para diminuir a população desses dípteros na Fazenda da Barra, em Lobato.

Biology of the first generation of a laboratory colony of Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) (Diptera: Psychodidae)

The phlebotomine sand flies Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) are very close and may be involved in the transmission of Leishmania spp. Ross, 1903 in Brazil. The biology of the first laboratory-reared generations of these species, descended from insects captured in Além Paraíba (N. intermedia) and Corinto (N. neivai) in the Brazilian state of Minas Gerais, is described here. The captured females were fed on hamsters and maintained individually in rearing pots. Laboratory temperature and relative humidity were maintained at 25-26 masculineC and 80% respectively. The productivity of the first generation of N. intermedia was greater than that of N. neivai, and its development time clearly shorter, particularly for the second and third larval instars.