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United States Department of Agriculture

Agricultural Research Service


item Becnel, James

Submitted to: Society for Invertebrate Pathology Annual Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 18, 2002
Publication Date: August 18, 2002

Technical Abstract: Control of the invertebrate host is an integral part of any integrated program to prevent the spread of vector borne diseases of man and animals. This includes important mosquito borne arboviruses such as yellow fever, dengue and the various types of encephalitis including West Nile Virus, St. Louis Encephalitis, Eastern Equine Encephalitis and Venezuelan Equine Encephalitis among many others. Efforts to control mosquito vectors have relied primarily on chemical adulticiding and larviciding, source reduction and biological control. Investigations on biological control, specifically microbial control, have resulted in many important contributions to both applied and basic research on pathogens of mosquitoes and other Diptera. Invertebrate pathologists worldwide have discovered important diseases of mosquitoes including bacteria, fungi, protozoa, microsporidia, nematodes and viruses some of which are currently widely utilized in vector control programs. The microbial insecticide, Bacillus thuringiensis var. israelensis (Bti) was first discovered in 1976 (Goldberg and Margalit, 1977) and since that time has proven to be highly pathogenic for many aquatic Diptera mainly the Culicidae, Simuliidae, Dixiidae, Chironomidae, and some Ceratopogonidae (Lacey, 1997). Bti was registered by the US EPA in 1983 and has been successfully utilized for control of mosquitoes and black flies worldwide with more than 25 products registered for mosquito and black fly control. Bti has an excellent safety record and resistance has not been found probably due to its complex mode of action involving synergistic interaction between up to four proteins (Becker and Margalit, 1993). Bacillus sphaericus (Bs) is another successful microbial insecticide isolated from mosquitoes in 1965 (Kellen et al., 1965; Lacey, 1997). It was registered in 1991 and there are currently two registered products for mosquitoes with good activity for Culex and some Anopheles mosquitoes but less effective for Aedes spp. Bs also has an excellent safety record but there have been numerous reports of resistance development (Rao et al., 1995). Fungi belonging to the genera Lagenidium, Culicinomyces and Coelomomyces have been studied as microbial control agents for mosquitoes (Lacey and Undeen, 1986). Lagenidium giganteum has been the most extensively developed (Brey and Remaudiere, 1985; Kerwin and Petersen, 1997) and is registered with the U.S. Environmental Protection Agency and several states, including California and Florida, for operational control of larval mosquitoes. L. giganteum is specific for mosquitoes and has shown good recycling capabilities for weeks, months, or even years in certain breeding habitats after a single application (Kerwin et, 1994). Other groups of mosquito pathogens have been extensively investigated including the ciliate Lambronella clarki (Washburn and Anderson, 1991), microsporidia such as Branciola (=Nosema) algerae (Anthony, 1978), Edhazardia aedis (Becnel et al.,1989) and Amblyospora connecticus (Andreadis, 1988; 1990 ) and the mermithid nematodes Romanomermis culicivorax (Petersen, 1985) and Strelkovimermis spiculatus (Camino and Garcia, 1990; Garcia and Camino, 1991). While these are important natural control agents for mosquitoes, their use for operational mosquito control is limited because of requirements for in vivo production and a short shelf life. However, some of these have demonstrated effectiveness as introduced agents and may play a role in classical biological control projects such as E. aedis for Aedes aegypti (Becnel and Johnson, 2000) and S. spiculatus for Culex mosquitoes (Becnel and Johnson, 1998). Mosquito pathogenic viruses such as baculoviruses and iridescent viruses have been known since 1963 but none have shown any potential due to the inability to transmit these pathogens to the host. Recently, a new baculovirus for Culex mosquitoes (CuniNPV) has been isolated where transmission has been determined to be mediated by divalent cations: magnesium is required for transmission whereas calcium inhibits transmission (Becnel et al., 2001). The ability to transmit CuniNPV has, for the first time, allows the evaluation of these viruses as control agents for mosquitoes and also to conduct molecular studies to investigate genes that determine transmission, host range, virulence and other key biological features required to infect and kill mosquitoes (Afonso et al., 2001; Moser et al., 2001).

Last Modified: 11/27/2015
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