Methods in Anopheles Research - MR4

Chapter 2 : Anopheles Laboratory Biology and Culture2.2 Infections in Mosquito CulturesPage 7 of 10Brachiola algerae (Nosema algerae) This is considered one of the most important infections in aninsectary. As with other protists, these are often found infecting the tissues associated with larval fatbodies, ovaries, midguts, and gastric systems in mosquitoes. Infections with this parasite are rarelyreported from insectaries. Intra-insectary transmission is reported often from colony to colony (Savageand Lowe 1970). In An. gambiae, infections with Brachiola have caused a reduction in egg production(Jenkins 1964). Infections are transmitted via contaminated surfaces, especially eggs, therefore surfacesterilization of eggs can be used to break the transmission cycle. It is a chronic infection that will sweepthrough a colony until all individuals are infected (J. Becnel personal communication).Vavraia spp (Plistophora). These were formally recognized as Brachiola but have since been movedinto a new genus. As in Brachiola, Vavraia parasitize the malpighian tubules and ovaries and will continueto infect other organs over time. However, mortality is usually negligible. Transmission of this parasite isthought to occur through the embryos. The main effect of parasitism is Vavraia’s ability to interfere withookinete development of Plasmodium parasites within the midgut (Jenkins 1964), (Kramer 1964)).Infections within laboratory colonies have been reported from minimal to critical, and some infectionshave been said to spontaneously disappear.External infectionsEpistylis spp. These protists are recognized as epibionts (An organism that lives on the body surface ofanother) of mosquito larvae. Although they attach themselves to larvae, they do not cause any diseasewithin the animal. These generally will appear as a fuzzy coating around the larvae. Mortality frominfestation with Epistylis is caused by either physically blocking the larva from feeding or by overwhelmingthe larva and reducing its normal movements. Heavily infested larvae may have trouble reaching thesurface to breathe or their siphons may be blocked by attached protists (Larson 1967).Vorticella spp. As in Epistylis, these are considered epibionts of mosquito larvae and appear as a fuzzycoating around the larvae (Figures 2.2.9 and 2.2.10) (Schober 1967). Although they are frequentlyencountered in nature, they have been isolated in laboratory colonies (Armstrong and Bransby-Williams1961; Hati and Ghosh 1961; Larson 1967).Figure 2.2.9 Vorticella-infested Anopheles stephensi L4.