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The influence of seasonal changes on epidemiological and entomological indices of malaria transmission in North Central Nigeria was elucidated in a series of studies carried out between January 2004 and December 2009. The climate in the study area was divided into three seasonal periods namely, rainy (May-October), dry (December-March) and transitional (April and November), during which larval and adult anopheline mosquito collections were carried out and assessed for densities, sporozoite infection and parity rates and potentials for malaria transmission. The results indicated that the climate in the study area was clearly seasonal, with close similarities in the patterns of distribution of the climatic factors in the study sites. Mosquito densities, both at the adult and larval stages (i.e., 29.35 +/- 5.10 adult mosquitoes/man/night and 10.36 +/- 3.34 larvae/dip, respectively), were significantly (p<0.05) highest during the rainy season. However, while the former varied significantly in the three seasonal periods, the latter was not significantly different during the dry and transitional seasons. Malaria transmission risks, in terms of sporozoite rates and entomological inoculation rates, was significantly (p<0.05) least in the dry season (i.e., 2.89 +/- 1.25% and 0.37 +/- 0.21 infective bite/man/night, respectively) but the two variables were not significantly (p>0.05) different during the transitional and rainy seasons. Adult mosquito daily survival rate and adult longevity were least in the dry season (26.52 +/- 11.80% and 6.80 days, respectively) and significantly (p<0.05) highest during the rainy season (72.28 +/- 4.00% and 16.95 +/- 4.20 days, respectively). Parous rates of the mosquitoes and duration of sporogony had distinct distribution pattern from the other variables investigated. While, significantly highest parous rates were recorded in the transitional season (86.00 +/- 4.30%), duration of sporogony was not significantly (p>0.05) different during the three seasons. The epidemiology of urban malaria in North Central Nigeria was discussed from the view points of the these results and concluded that the findings should promote the development of informed temporally-targeted vector control programs for the area.

Background: Timely entomological and insecticide resistance monitoring is a key to generating relevant data for vector management. We investigated the insecticide susceptibility status of Anopheles gambiae s.l. in eight rural farming communities in Southern Gombe, Nigeria. Methods: Overall, 3–5 days-old adult female Anopheles mosquitoes reared from field-collected immature stages between September and November, 2014 were exposed to the diagnostic doses of pyrethroids, organophosphate and carbamate insecticides using the Center for Disease Control Bottle bioassay. The observatory knockdown time from exposure to each insecticide was recorded up to two hours. The dead mosquitoes were then identified morphological­ly and by molecular assays. Results: Mortality results showed resistance in An. gambiae s.l. populations to bendiocarb (2.3–100%), deltamethrin (39–70%), pirimiphos-methyl (65–95%), dichloro-diphenyl-trichloroethane (0–38.1%), permethrin (0–46.3%) and lambda-cyhalothrin (42.5–86.4%). The few cases of full susceptibility were observed from lamdacyhalothrin exposed population of An. gambiae s.l. in Banbam and Pantami respectively. An. gambiae 177 (45%) was significantly higher (P< 0.05) than An. arabiensis 64 (16.3%), An. coluzzii 34 (8.7%) and An. gambiae/An. coluzzii hybrid 78 (19.8%). Conclusion: A strong evidence of widespread resistance in the major malaria vector species in Southern Gombe to all common classes of insecticides is a justification for the State Malaria Elimination Programme to consciously con­sider incorporating insecticide resistance management strategies into control programs in order to sustain the future of current control interventions

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