Pythium insidiosum isolated from infected mosquito larvae in central Brazil.

Pythium insidiosum is a straminopilan pathogen causing life threatening infections in mammals inhabiting temperate, tropical and subtropical areas of the world. The concept that P. insidiosum could also infect mosquitoes was mentioned earlier by investigators conducting phylogenetic analysis on available P. insidiosum isolates deposited at different culture collections. However, an official report and details on its pathological features in mosquitoes are not available. We are reporting the isolation of P. insidiosum from infected mosquito larvae during a survey conducted in central Brazil. At least three oomycotan isolates were recovered during the survey. Due to their ability to infect mosquito larvae the isolates were deposited in the U.S. Department of Agriculture, Agricultural Research Service Collection of Entomopathogenic Fungi (ARSEF; Ithaca, New York) as putative Lagenidium species. The investigated isolates developed very well at 37 °C, produced typical Pythium-like vesicles containing numerous biflagellate zoospores, hydrolyzed sucrose, and their cultured extracted proteins were recognized in serological analysis by anti-P. insidiosum antibodies. Phylogenetic analyses using ITS and partial COXII DNA sequences identified the isolates as P. insidiosum within the American Cluster I. This is the first official report of P. insidiosum recovered from infected mosquito larvae, indicating that this mammalian pathogen, in addition to plants, it could also use mosquito larvae to complete its life cycle in nature.