Vectorial capacity of Lutzomyia (Lutzomyia) cruzi (Diptera: Psychodidae) for Leishmania (Leishmania) infantum.

Author(s)

Everton Falcão de Oliveira

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Saúde Pública (FSP/CIR)
• Defense date: 2015-03-31

Examining board members

Eunice Aparecida Bianchi Galati; Claudio Casanova; Fernando Ferreira; Marcia Dalastra Laurenti; Delsio Natal

• Advisor: Eunice Aparecida Bianchi Galati

Abstract

In some regions such as in the municipalities of Corumbá and Ladário in Mato Grosso do Sul state, there are ecological and epidemiological evidence that Lutzomyia (Lutzomyia) cruzi (Mangabeira, 1938) is the vector of Leishmania (Leishmania) infantum Nicolle, 1908 (or subspecies of L. (L.) infantum chagasi Cunha & Chagas, 1937 according to some authors), the etiologic agent of visceral leishmaniasis (VL). The absence of Lutzomyia (Lutzomyia) longipalpis (Lutz & Neiva, 1912), the main vector of the parasite, supports this hypothesis. This study aimed to evaluate the parameters and estimate the vectorial capacity of Lu. cruzi for L. (L.) infantum and Leishmania (Leishmania) amazonensis Lainson & Shaw, 1972. For the latter, only parameters was evaluated without numerical estimation of the vectorial capacity. The evaluation of the vectorial capacity was carried out from laboratory experiments (experimental infection) and field (attractiveness to sandflies). Through experimental infection by the parasite, it was possible to estimate the expected daily survival of infected females (vertical and laboratory estimate), evaluate the extrinsic incubation period of the parasite and get the length of gonotrophic cycle. To evaluate the insect vector competence, attempts have been made of experimental and natural transmission of Leishmania from females from colony whose subjects were fed for xenodiagnosis and wild females captured in the field, respectively. Monthly and seasonal distribution of Lu. cruzi was evaluated by weekly installation of light traps in the peridomicile of five residences in the urban area of the Municipality of Corumbá. Meteorological variables obtained from the Weather Monitoring Center, Climate and Water of Mato Grosso do Sul Resources, radiometric indices calculated from spatial resolution images (GeoEye) and the percentage of plant cobertural were used in this study. Results allowed estimating the vectorial capacity of Lu. cruzi for L. (L.) infantum, which was 0.24, i.e., it is expected that the female population in the region produce 0.24 new infections per day of exposure to an infection. Vector competence of Lu. cruzi for L. (L.) infantum and L. (L.) amazonensis by biting, was demonstrated by natural and experimental transmission of both parasites, respectively. Natural infection of Lu. cruzi by L. (L.) amazonensis was identified. Regarding the monthly x distribution, there was no significant association between of sandflies and the environmental and climate variables. It was observed high peaks population in the rainy season and lower peaks in the dry season. The pattern of seasonal distribution of species of sand flies demonstrated in this study was determined primarily by Lu. cruzi specimens, since this species represent 93.94 per cent of the total captured. The monthly change showed that Lu. cruzi species has great plasticity and has been observed in all months of collection. (AU)

• FAPESP's process: 11/23414-0 - Vectorial capacity of Lutzomyia (Lutzomyia) cruzi and Lutzomyia (Lutzomyia) forattinii (Diptera: Psychodidae) to Leishmania (Leishmania) infantum chagasi
• Grantee: Everton Falcão de Oliveira
• Support Opportunities: Scholarships in Brazil - Doctorate