| Summary: | <p>Abstract</p> <p>Background</p> <p>The dual problems of rising insecticide resistance in the malaria vectors and increasing human malaria cases since 2001 in southern Mozambique are cause for serious concern. The selection of insecticides for use in indoor residual spraying (IRS) programmes is highly dependent on the extent to which local mosquitoes are susceptible to the approved classes of insecticides. The insecticide resistance status and role in malaria transmission of <it>Anopheles funestus </it>was evaluated at the Maragra Sugar Estate in southern Mozambique where an IRS vector control programme has been in operation for seven years using the carbamate insecticide bendiocarb.</p> <p>Results</p> <p>No <it>Anopheles </it>species were captured inside the sugar estate control area. <it>Anopheles funestus </it>group captured outside of the estate represented 90% (n = 475) of the total collections. Of the specimens identified to species by PCR (n = 167), 95% were <it>An. funestus s.s. </it>One <it>An. rivulorum </it>was identified and seven specimens did not amplify. The <it>Anopheles gambiae </it>complex was less abundant (n = 53) and of those identified (n = 33) 76% were <it>An. arabiensis </it>and 24% <it>An. merus</it>. Insecticide susceptibility tests showed that wild-caught and F-1 family <it>An. funestus </it>were resistant to deltamethrin (32.5% mortality) and lambda-cyhalothrin (14.6% mortality), less so to bendiocarb (71.5% mortality) and fully susceptible to both malathion and DDT (100%). Bendiocarb and pyrethroid resistance was nullified using 4% piperonyl butoxide (Pbo), strongly suggesting that both are mediated by P450 monooxygenase detoxification. ELISA tests <it>of An. funestus </it>for <it>Plasmodium falciparum</it>, gave a sporozoite rate of 6.02% (n = 166). One unidentified member of the <it>An. gambiae </it>complex tested positive for <it>P. falciparum </it>sporozoites.</p> <p>Conclusion</p> <p><it>Anopheles funestus </it>was found to be the most abundant and principle vector of malaria in this area, with members of the <it>An. gambiae </it>complex being secondary vectors. Despite the continual use of bendiocarb within the estate for seven years and the level of <it>An. funestus </it>resistance to this insecticide, the IVC programme is still effective against this and other <it>Anopheles </it>in that no vectors were found inside the control area. However, the Mozambique National Malaria Control Programme ceased the use of DDT and bendiocarb in this area of its operations in 2009, and replaced these insecticides with a pyrethroid which will increase insecticide resistance selection pressure and impact on control programmes such as the Maragra IVC.</p>
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