Effects of larval rearing substrates on some life-table parameters of Lutzomyia longipalpis sand flies

Sand flies are the insects responsible for transmitting Leishmania parasites, the causative agents of leishmaniasis in humans. However, the effects of sand fly breeding sites on their biology and ecology remain poorly understood. Herein, we studied how larval nutrition associated with putative breeding sites of the sand fly Lutzomyia longipalpis affects their oviposition, development, microbiome, and susceptibility to Leishmania by rearing L. longipalpis on substrates collected from an endemic area for leishmaniasis in Brazil. The results showed that female L. longipalpis select the oviposition site based on its potential to promote larval maturation and while composting cashew leaf litter hindered the development, larvae reared on chicken feces developed rapidly. Typical gut microbial profiles were found in larvae reared upon cashew leaf litter. Adult females from larvae reared on substrate collected in chicken coops were infected with Leishmania infantum, indicating that they were highly susceptible to the parasite. In conclusion, the larval breeding sites can exert an important role in the epidemiology of leishmaniasis. Author summary Sand flies are the insect vectors involved in the transmission of many pathogens, however, the transmission of parasites to humans leading to visceral leishmaniasis is currently the most critical threat caused by this insect. Despite the importance of the vector, many aspects of the biology of sand flies are poorly understood, especially their breeding sites. This study was designed to evaluate the oviposition, life span, microbiome, and parasite infections in the main species of sand fly responsible for visceral leishmaniasis in America. Insects were reared on substrates collected from different putative habitats of sand flies in an endemic area for the disease in Brazil. The results showed that female vectors selected an oviposition site depending on the potential offered to their offspring. Furthermore, the development of immature stages varied according to the type of substrate evaluated, with cashew leaves litter delaying larval development, while chicken shelter promoted larval development. The challenge of females emerging from chicken shelter substrate with the parasite indicates that insects reared in such an environment could successfully sustain the infection. These results suggest that the type of breeding site can affect insect biology as well as the epidemiology of the disease.

Automated summary

The study found that female sand flies select oviposition sites based on the potential for larval maturation, and that composting cashew leaf litter hindered development while larvae reared on chicken feces developed rapidly. Adult females from larvae reared on chicken coop substrates were highly susceptible to Leishmania infection.