Fish, mosquito resistant

The development of strains resistant to insecticides is an extremely widespread phenomenon that is known to have occurred in more than 200 species of insects and mites, and resistance of up to several 100-fold has been noted. The different biochemical and genetic factors involved have been studied extensively and well characterized. Relatively few vertebrate species are known to have developed pesticide resistance and the level of resistance in vertebrates is low compared to that often found in insects. Susceptible and resistant strains of pine voles exhibit a 7.4-fold difference in endrin toxicity. Similarly pine mice of a strain resistant to endrin were reported to be 12-fold more tolerant than a susceptible strain. Other examples include the occurrence of organochlorine insecticide-resistant and susceptible strains of mosquito fish, and resistance to Belladonna in certain rabbit strains. 

Reports are published on the metabolism of methoprene by plants (25), aquatic microorganisms (26), soil microbes (27), house flies and mosquitoes in vivo (28), resistant house flies in vivo and in vitro (29), a steer (30), a lactating cow (31), chickens (32), and bluegill fish (33). In addition, radioactive material balance studies have been published for a guinea pig, steer, and cow (34), chickens (35), and rats (36, 37), including whole-body autoradiography in rats (37). 

Klerks, P.L., and Lentz, S.A. (1998) Resistance to lead and zinc in the western mosquito fish Gambusia affinis inhabiting contaminated Bayou Trepagnier. Ecotoxicology 7, 11-17. 

Fenthion is a broad spectrum insecticide. When applied as a surface spray, it controls adult mosquitoes and other insect pests and spiders in agricultural, horticultural, and home garden use. Recent reports indicate that resistance to fenthion has developed in some species of mosquitoes. Fenthion is used in dermal application for treatment of swine and cattle for control of lice, flies, and ticks, and in flea and tick treatments for pets. It is also used in aqueous applications to kill dragonfly larvae in ornamental fish production ponds. Fenthion is an effective avicide, and has been marketed to control birds considered to be pests. 

Boyd, C.E. and Ferguson, D.E. (1964) Spectrum of cross-resistance to insecticides in the mosquito fish, Gambusia affinis. Mosquito News, 24, 19-21. 

The use of DDT increased enormously on a worldwide basis after World War II, primarily because of its effectiveness against mosquitoes that spread malaria and hce that carry typhus. The World Health Oi anization estimates that approximately 25 million fives have been saved through the use of DDT. DDT seemed to be the ideal insecticide—it is cheap and has relatively low toxicity to mammals (oral LD is 300-500 mg/kg). However, problems related to extensive use of DDT began to appear in the late 1940s. Many species of insects developed resistance to DDT, and DDT was also discovered to have a high toxicity toward fish. The chemical stability of DDT and its fat solubility compounded the problem. 

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