Methods in Anopheles Research - MR4

Chapter 2 : Anopheles Laboratory Biology and Culture2.2 Infections in Mosquito CulturesPage 3 of 10Non-Occluded Viruses (Becnel and White 2007)These viruses form paracrystalline arrays of virions in infected cells.IridioviridaeMosquito Iridescent Virus (MIV): These are cosmopolitan in nature in field collected larvae. Infections canbe detected by placing larvae in a dark pan and scanning them with a fluorescent light. Infected larvae willhave iridescent patches of turquoise, green or orange depending on the specific infecting virus. Infectionsare usually localized in the fat body or epidermis. Larvae infected in early instars are highly susceptible.Infections in later instars are typically passive allowing for transovarial transmission. Sub-lethal infectionsoften result in reduced fecundity and longevity in the stock (Becnel 2007).ParvoviridaeMosquito Densovirus (MDV): Infections with the viruses are typically subtle in nature. Infected larvae willbecome lethargic, loose their body color, have a contorted appearance, or appear whitish in color beforeexpiring (Becnel and White 2007) Infections are widespread except in the midgut epithelium. Many ofthese viruses have been isolated from anopheline mosquitoes and from established cell lines.BacteriaAlthough several bacteria are known to be pathogenic to mosquito larvae, relatively few of them occurnaturally in an insectary setting. Infections in the rearing containers are often caused by the inadvertentintroduction of bacteria from the skin of an insectary employee or through the addition of contaminatedwater or food. In Africa, Enterobacteria infections were seen in the haemolymph of insect larvae (Muspratt1966). In advanced stages of disease, black spores were visible inside the larvae and eventually thelarvae displayed a “milky” coloration and swollen appearance (Figure 2.2.4).Figure 2.2.4 Infected Anopheles stephensi. Note the milky swollen appearance indicative ofan infection.Escherichia coli common human fauna. E. coli bacteria have been found to be pathogenic to earlyinstar Culex mosquitoes (Jenkins 1964).Serratia marcescens commonly found growing in standing water. This bacterium has not been reportedto be lethal, but in poor rearing conditions it grows quickly forming a reddish film on the bottom of therearing pans.Pseudomonas fluorescens ubiquitous flagellated bacterium. P. fluorescens is a commonly isolatedbacterium from soil and water sources, and it has been shown to be lethal to mosquito larvae.Pseudomonads are known to cause extensive larval mortality due to their production of toxic substances(Jenkins 1964).