38th Annual Meeting of the Society for Invertebrate Pathology

Members of the genus Helicosporidium are the first described algal insect pathogens. They have a close affinity to the non-photosynthetic algae of the genus Prototheca, and exhibit a wide host range, infecting many species of aquatic and terrestrial insects. In this study, the infectivity of two Helicosporidium spp. isolates, originating from a black fly (SjHe) and an aquatic weevil (CsHe), was tested against four mosquito species (Anopheles quadrimaculatus Say, Anopheles albimanus Weidemann, Culex quinquefasciatus Say, and Aedes aegypti (L.)). Each of these experimental hosts was susceptible to infection with SjHe and CsHe. Anopheles quadrimaculatus was the most susceptible mosquito species measured by infection rate and mortality. In An. quadrimaculatus exposure to helicosporidia did not effect development of the larvae, whereas in exposed Ae. aegypti, larval development was impaired. Bioassays with Ae. aegypti also showed that susceptibility to infection decreased with increasing age of larvae. In addition, greater resistance and melanization in all hosts in response to CsHe may indicate that mosquito larvae are less-suitable hosts for this isolate. Future research will be focused on interactions between host and pathogen development and the mechanism of pathogen ingress.