| Summary: | <p>Abstract</p> <p>Background</p> <p>Insecticide resistance in malaria vector mosquitoes presents a serious problem for those involved in control of this disease. South Africa experienced a severe malaria epidemic during 1999/2000 due to pyrethroid resistance in the major vector <it>Anopheles funestus</it>. Subsequent monitoring and surveillance of mosquito populations were conducted as part of the malaria vector control programme.</p> <p>Methods</p> <p>A sample of 269 <it>Anopheles funestus s.l. </it>was collected in Mamfene, northern KwaZulu-Natal, using exit window traps in pyrethroid sprayed houses between May and June 2005. Mosquitoes were identified to species level, assayed for insecticide susceptibility, analysed for <it>Plasmodium falciparum </it>infectivity and blood meal source.</p> <p>Results</p> <p>Of the 220 mosquitoes identified using the rDNA PCR method, two (0.9%) were <it>An. funestus s.s. </it>and 218 (99.1%) <it>Anopheles parensis</it>. Standard WHO insecticide susceptibility tests were performed on F1 progeny from wild caught <it>An. parensis </it>females and a significant survival 24 h post exposure was detected in 40% of families exposed to 0.05% deltamethrin. Biochemical analysis of F1 <it>An. parensis </it>showed no elevation in levels/activity of the detoxifying enzyme systems when compared with an insecticide susceptible <it>An. funestus </it>laboratory strain. Among the 149 female <it>An. parensis </it>tested for <it>P. falciparum </it>circumsporozoite infections, 13.4% were positive. All ELISA positive specimens (n = 20) were re-examined for <it>P. falciparum </it>infections using a PCR assay and none were found to be positive. Direct ELISA analysis of 169 blood meal positive specimens showed > 75% of blood meals were taken from animals. All blood fed, false positive mosquito samples for the detection of sporozoites of <it>P. falciparum </it>were zoophilic.</p> <p>Conclusion</p> <p>The combination of pyrethroid resistance and <it>P. falciparum </it>false-positivity in <it>An. parensis </it>poses a problem for vector control. If accurate species identification had not been carried out, scarce resources would have been wasted in the unnecessary changing of control strategies to combat a non-vector species.</p>
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