Culex

The value of insecticides in controlling human and animal diseases spread by insects has been dramatic. It has been shown that between 1942 and 1952, the use of DDT in pubHc health measures to control the mosquito vectors of malaria and the human body louse vector of typhus saved five million hves and prevented 100 million illnesses (4). Insecticides have provided the means to control such important human diseases as filariasis transmitted by Culex mosquitoes and onchocerciasis transmitted by Simulium blackflies. 

As mosquito larvae are relatively easy to kill with insecticides, any toxic spray residue is likely to be detected. Two species of mosquito larvae were used, the yellow fever mosquito (Aedes aegypti L.) and the southern house mosquito (Culex quinquefasdatus Say). Tests with the southern house mosquito were made essentially according to the method of Campbell, Sullivan, and Smith (I), except for the kind of food supplied and size of containers used. 

An aqueous solution containing 1 part in 200,000,000 of parathion gave 50% kill to southern house mosquito larvae (Culex quinquefasdaius Say). Parathion solutions did not lose any toxicity on standing for a month at room temperature (Figure 1). At the end of 2 months, however, the solutions lost their toxicity to mosquito larvae. 

Normal routes of exposure Vectors (mosquitoes—Aedes vexans, Culex triteeniorhynchus, Anopheles funestus midges—Culicoides species). 

Normal Routes of Exposure Vectors (mosquitoes—Culex species, Aedes species, Cocjuillet-tidia species). 

Normal routes of exposure Vectors (mosquitoes—Culex species). 

Normal Routes of Exposure Inhalation Ingestion Abraded skin Mucous membranes Vectors (mosquitoes—Aedes species and Culex species sandflies). 

Normal Routes of Exposure Vectors (mosquitoes—Aedes species, Culex species, Psorophora species, Mansonia, species, Deinocerites species, Haemogogus species, Sabethes species, Anopheles species). 

Bailey, D.L., G.C. Labrecque, and T.L. Whitfield. 1970. Slow-release and emulsifiable formulations of Dursban and Abate for controlling larvae of Culex pipiens quinquefasciatus. Mosq. News 30 465-467. 

Moore, J.B. and S.G. Breeland. 1967. Field evaluation of two mosquito larvicides, Abate and Dursban against Anopheles quadrimaculatus and associated Culex species. Mosquito News 27 105-111. 

Rawn, G.P., G.R.B. Webster, and G.M. Findlay. 1978. Effect of pool bottom substrate on residues and bioactivity of chlorpyrifos, against larvae of Culex tarsalis (Diptera Culicidae). Canad. Entomol. 110 1269-1276. 

Reisen, W.K., G. Yoshimura, W.C. Reeves, M.M. Milby, andR.P. Meyer. 1984. The impact of aerial applications of ultra-low volume adulticides on Culex tarsalis populations (Diptera Culicidae) in Kern County, California, USA, 1982. Jour. Med. Entomol. 21 573-585. 

Unknown Fish exposed to radiolabeled diflubenzuron for33 days contained about 6% of the parent diflubenzuron vs. 54% for alga (Oedogonium cardiacum), 82% for snail (Physa sp.), and 94% for larvae of mosquito (Culex pipiens quinquefasciatus) 42... 

Mittal, P.K. and V.K. Kohli. 1988. The effect of diflubenzuron on the egg laying and vitellogenesis in female Culex pipiens quinquefasciatus. Res. Bull Panjab Univ. 39 93-100. 

Until recently, the resistance of mosquitoes to pyrethroids has not been taken as a serious issue. In Japan, C. p. pallens and Aedes albopictus (Skuse) are the main species living around houses. Although mosquito coils have utilized natural pyrethrins as insecticidal ingredients for about 50 years and then allethrin for about 50 years, there has been no report on resistance development. The reason for this is considered to be the short active time of 4-5 months per year for C. p. pallens. Yasutomi et al. [50] reported in 1989 the presence of pyrethroid-resistant Culex tritaeniorhynchus in Okinawa, but Japanese encephalitis transmitted by C. tritaeniorhynchus decreased markedly after 1992 and disappeared. 

Yasutomi K, Takahashi M (1989) Insecticidal resistance of Culex tritaeniorhynchus in Chinen, Okinawa Prefecture, with special reference to the mechanism of pyrethroid-resistance. Jpn JSanitZool 40 315-321... 

Thanispong K, Sathantriphop S, Chareonviriyaphap T (2008) Insecticide resistance of Aedes aegypti and Culex quinquefasciatus in Thailand. J Pestic Sci 33(4) 351-356... 

Topical application for evaluating insecticidal efficacy against common house mosquitoes (Culex pipiens pallens) complied with the method described by Yamaguchi et al. [18]. 

The lethal efficacy of Metofluthrin against four medically important mosquito species (C. pipiens pallens, Culex quinquefasciatus, Aedes aegypti, and A. albopictus) is summarized in Fig. 2. The efficacy of Metofluthrin was found to be very high against all these 4 species and it was between 19 and 49 times higher than that of d allethrin. 

Compounds Culex pipiens pallens Aedes albopictus Musca domestica Blattella germanica... 

Fig. 2 Lethal efficacy of Metofluthrin against mosquitoes topical application method, relative efficacy the larger the number the more active the compound (Cp Culex pipiens pallens, Cq Culex quinquefasciatus, Ae Aedes aegypti, Aa Aedes albopictus)...

Fig. 3 Lethal efficacy of Metofluthrin against field strains of Culex quinquefasciatus. topical application method, LD50(pg/female adult) ( Laboratory strain is a susceptible strain) (reproduced from [3])...

Table 2 Knockdown efficacy of Metofluthrin coil against Culex pipiens pallens (laboratory strain) by large chamber free-flying method...

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