Abstract
BackgroundMalaria burden is high in Nigeria, yet information on the major mosquito vectors is lacking especially in the Sudan savannah region of the country. In order to facilitate the design of future insecticide-based control interventions in the region, this study has established the resistance profile of An. gambiae s.l. populations in two northern Nigeria locations and assessed the contribution of target site resistance mutations.MethodsLarval collection was conducted in two localities in Sudan savannah (Bunkure and Auyo) of northern Nigeria between 2009 and 2011, from which resulting adult, female mosquitoes were used for insecticides bioassays with deltamethrin, lambda-cyhalothrin, DDT and malathion. The mosquitoes were identified to species level and molecular forms and then genotyped for the presence of L1014F-kdr, L1014S-kdr and ace-1R mutations.ResultsWHO bioassays revealed that An. gambiae s.l. from both localities were highly resistant to lambda-cyhalothrin and DDT, but only moderately resistant to deltamethrin. Full susceptibility was observed to malathion. An. gambiae, M form (now An. coluzzii), was predominant over An. arabiensis in Auyo and was more resistant to lambda-cyhalothrin than An. arabiensis. No ‘S’ form (An. gambiae s.s.) was detected. A high frequency of 1014 F mutation (80.1%) was found in An. coluzzii in contrast to An. arabiensis (13.5%). The presence of the 1014 F kdr allele was significantly associated with resistance to lambda-cyhalothrin in An. coluzzii (OR = 9.85; P < 0.001) but not in An. arabiensis. The L1014S-kdr mutation was detected in a single An. arabiensis mosquito while no ace-1R mutation was found in any of the mosquitoes analysed.ConclusionsThe predominance of An. coluzzii and its resistance profile to main insecticides described in this study can guide the implementation of appropriate vector control interventions in this region of Nigeria where such information was previously lacking.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2334-14-441) contains supplementary material, which is available to authorized users.
Highlights
Malaria burden is high in Nigeria, yet information on the major mosquito vectors is lacking especially in the Sudan savannah region of the country
Insecticide susceptibility bioassays Insecticides bioassay conducted using the mixed F0 adults from Auyo, revealed resistance to DDT with only 12% knockdown after one hour exposure (Figure 2A) and mortality of 44.6% after 24 hours (Figure 3A). These mosquitoes were resistant to lambda-cyhalothrin and deltamethrin with slow knockdown of about 30% after an hour of exposure and mortality of 52.8% and 78.4% respectively 24 hours postexposure
An. coluzzii was predominant among the mosquitoes resistant to lambdacyhalothrin (86.8%) while An. arabiensis was predominant in the susceptible mosquitoes (69.2%)
Summary
Malaria burden is high in Nigeria, yet information on the major mosquito vectors is lacking especially in the Sudan savannah region of the country. Information about distribution of Anopheles vectors and pattern of resistance to the major insecticides from Nigeria especially northern region is grossly lacking. Vector control strategies involve the use of pyrethroid-based long-lasting insecticidal treated nets (LLINs) and indoor residual spray (IRS) bendiocarb and dichlorodiphenyltrichloroethane (DDT) are used in some areas for IRS [8]. This widespread use of a single class of insecticide could result in development of more insecticide resistance in the mosquito vectors and lead to a major public health problem given the limited availability of alternative insecticides [9]
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