Methods in Anopheles Research - MR4

Chapter 2 : Anopheles Laboratory Biology and Culture2.2 Infections in Mosquito CulturesPage 4 of 10Leptothrix buccalis common water bacterium isolated in fresh and polluted water sources and found tobe highly lethal to An. maculipennis. With this infection, the larva maintains the disease through eclosion,but death does not occur until sometime after emergence (Jenkins 1964).Streptococcus spp common human fauna. These bacteria can rapidly grow in the warm insectaryconditions and will attach to larvae in large numbers. The bacteria invade the integument (insect's hardouter coat) and cause internal damage leading to mortality in the L3 or L4 stage (Kramer 1964).Treatment of bacterial infectionsAntibiotics such as Penicillin-Streptomycin-Fumigillin (PSF) (Invitrogen 15240-062) can be used in larvalculturing (de St. Jeor and Nielsen 1964). However, it is recommended that before full scaleimplementation, trials are conducted to determine the dosage required to eliminate the infection withoutkilling too many larvae. Additionally, you can feed antibiotics to adults in the sugar meal (Toure et al.2000).In the insectaryTo ensure that an infection does not spread to another colony, sterilize all rearing trays by eitherautoclaving them or soaking them in a 5-10% household bleach solution for 24 hours. Wipe down allcounters with a 5-10% bleach solution and replace any larval rearing diets in the rearing room.FungiFungi have been considered one of the most pathogenic organisms that can infect mosquitoes. A largenumber of fungi have been isolated from mosquitoes, both wild and laboratory reared, recently reviewedby (Scholte et al. 2004). Most fungal infections are transmitted by free-floating spores.Coelomomyces spp This is the one of the most widely studied fungi that infects mosquitoes. Infectionstypically occur in early larval instars, and infected larvae rarely pupate or emerge. The infection can bedetected by locating “buds” or lumped structures in the anal gills of the larva (Figures 2.2.5 and 2.2.6). Ifinfection is suspected, dissecting the larvae should reveal hyphae emanating from several tissuesincluding the malpighian tubes and muscles. The hyphae will be branched, multinucleate, and clavate(club) shaped. Sporongia, the reproductive portion, will develop into dark spherical spores. Although thisis highly pathogenic, it is self limiting and usually only 1 or 2 generations will be affected due to the needof an intermediary host to complete its life cycle (Madelin 1965), (Scholte et al. 2004). In Africa, thesefungi have been often reported to be isolated from the ovaries and fat bodies of females only (Hazard1973). Authors have reported that larvae infected with Coelomomyces fungi often have a yellow, orange,or brownish color due to a number of sporangia that have developed internally (Kramer 1964).Leptolegnia spp. These are typically encountered in wild isolates. They are highly pathogenic, especiallyto L1 and L2 larvae. In An. gambiae it was shown that 100% of larvae were killed within 72 hours postinfection (Scholte et al. 2004).