Submitted to: Folia Parasitologica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/17/2004
Publication Date: 6/15/2005
Citation: Becnel, J.J., White, S.E., Shapiro, A.M. 2005. Microsporidia-mosquito relationships: from the simple to the complex. Folia Parasitologica. 52: 41-50. Interpretive Summary: Mosquitoes are important vectors of diseases to man and animals. Naturally occurring diseases of mosquitoes are being evaluated as biological control agents by ARS Scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville Florida. This article discusses the current knowledge of the life cycles, host parasite relationships and safety of a group of protozoan pathogens (microsporidia) from mosquitoes. New information on these mosquito pathogens is reviewed to describe features that distinguish mosquito parasitic microsporidia with simple life cycles and broad host ranges from truly mosquito-specific microsporidian parasites with complex life cycles.
Technical Abstract: Microsporidia in mosquitoes can be divided into two categories based on their life cycles and host-parasite relationships. Some species of microsporidia exhibit simple life cycles with one spore type responsible for oral (horizontal) transmission. They affect only one generation of the mosquito and are not usually host or tissue specific. Brachiola algerae (Vavra and Undeen, 1970) and Vavraia culicis (Weiser, 1947) are examples of species isolated from mosquitoes with relatively straightforward life cycles (one spore type) and simple host-parasite relationships. B. algerae and a close relative of V. culicis have also been isolated from a vertebrate (human) hosts but sources for these infections are unknown. In contrast to B. algerae and V. culicis, polymorphic (heterosporous) microsporidia in mosquitoes are characterized by complex life cycles involving multiple spore types responsible for horizontal and vertical transmission. They affect two generations of the mosquito and some involve an obligate intermediate host. These microsporidia are generally very host and tissue specific with complex developmental sequences comprised of unique stages and events. The microsporidium Edhazardia aedis (Kudo, 1930) is a pathogen of Aedes aegypti and does not require an intermediate host. The developmental cycle of E. aedis is characterized by four sporulation sequences, two in the parental host and two in the filial generation. Recent speculation relative to the source of B. algerae human infection have implicated infected mosquitoes and raised concerns about the safety of mosquito microsporidia in general. The subject of this review is to compare and contrast three species of microsporidia from mosquitoes, two with broad host ranges (B. algerae and V. culicis) and one specific to mosquitoes (E. aedis). This review describes features that distinguish mosquito parasitic microsporidia with simple life cycles and broad host ranges from truly mosquito-specific microsporidian parasites with complex life cycles.