Entomological and transmission risk indices of malaria vectors in selected communities in Osun state, Nigeria

Baseline survey is an integral component of a malaria vector control programme, providing valuable information on mosquito behaviour that guide the suitability of chosen interventions. A need assessment of baseline entomological indices towards the future implementation of indoor residual spray (IRS) was conducted in Osun State, Nigeria. Indoor resting mosquitoes were collected in human households from three LocalGovernment Areas. These were morphologically identified, subjected to species specific polymerase chain reaction (PCR) assay and analyzed for sporozoite infection and blood meal origin using enzyme linked   immunosorbent assay (ELISA). All female Anopheles identified fed on human blood but tested negative to Plasmodium falciparum circumsporozoite antigen. The PCR analysis showed a predominance of An. gambiae s.s. (95%) over An. arabiensis (5%). The preponderance of indoor resting An. gambiae s.s and the incidence of exophilic An. arabiensis suggest a combination of IRS and long lasting insecticidal nets (LLINs) for this region.Keywords: Malaria vectors, Transmission risk indices, Species specific PCR, Plasmodium falciparum, Circumsporozoite antigen, Long lasting insecticidal nets, Osun State, Nigeri

Underpinning Sustainable Vector Control through Informed Insecticide Resistance Management

Background: There has been rapid scale-up of malaria vector control in the last ten years. Both of the primary control strategies, long-lasting pyrethroid treated nets and indoor residual spraying, rely on the use of a limited number of insecticides. Insecticide resistance, as measured by bioassay, has rapidly increased in prevalence and has come to the forefront as an issue that needs to be addressed to maintain the sustainability of malaria control and the drive to elimination. Zambia’s programme reported high levels of resistance to the insecticides it used in 2010, and, as a result, increased its investment in resistance monitoring to support informed resistance management decisions. Methodology/Principal Findings: A country-wide survey on insecticide resistance in Zambian malaria vectors was performed using WHO bioassays to detect resistant phenotypes. Molecular techniques were used to detect target-site mutations and microarray to detect metabolic resistance mechanisms. Anopheles gambiae s.s. was resistant to pyrethroids,DDT and carbamates, with potential organophosphate resistance in one population. The resistant phenotypes were conferred by both target-site and metabolic mechanisms. Anopheles funestus s.s. was largely resistant to pyrethroids and carbamates, with potential resistance to DDT in two locations. The resistant phenotypes were conferred by elevated levels of cytochrome p450s. Conclusions/Significance: Currently, the Zambia National Malaria Control Centre is using these results to inform their vector control strategy. The methods employed here can serve as a template to all malaria-endemic countries striving to create a sustainable insecticide resistance management pla

Modelling of bio-oil yield from fast pyrolysis of sawdust

Bio-oil has received great attention due to the environmental concerns associated with the usage of fossil fuels and the predicted inability of these fuels to cope with future increases in energy demands. In this work an existing kinetic model equation has been modified using polynomial equations in conjunction with experimental data for six different sawdust types using the least squares method. The existing Model was modified with a linear equation (Model B), quadratic equation (Model C), and also by a cubic equation (Model D). The new models for bio-oil yield predictions obtained from the sawdust types show very low average errors of 1.2% - 4.4% compared to the experimental results and high correlation coefficients in the range 0.95 - 0.99 attesting to their reliability. Model C has been found to be the best for the spruce sawdust while Model D is the best for other sawdust types mentioned.Keywords: Modeling, Bio-oil yield, Sawdust, Fast PyrolysisNigerian Journal of Technological Researc

Evidence of carbamate resistance in urban populations of <it>Anopheles gambiae s.s.</it> mosquitoes resistant to DDT and deltamethrin insecticides in Lagos, South-Western Nigeria

<p>Abstract</p> <p>Background</p> <p>Resistance monitoring is essential in ensuring the success of insecticide based vector control programmes. This study was carried out to assess the susceptibility status of urban populations of <it>Anopheles gambiae</it> to carbamate insecticide being considered for vector control in mosquito populations previously reported to be resistant to DDT and permethrin.</p> <p>Methods</p> <p>Two – three day old adult female <it>Anopheles</it> mosquitoes reared from larval collections in 11 study sites from Local Government Areas of Lagos were exposed to test papers impregnated with DDT 4%, deltamethrin 0.05% and propoxur 0.1% insecticides. Additional tests were carried out to determine the susceptibility status of the <it>Anopheles gambiae</it> population to bendiocarb insecticide. Members of the <it>A. gambiae complex</it>, the molecular forms, were identified by PCR assays. The involvement of metabolic enzymes in carbamate resistance was assessed using Piperonyl butoxide (PBO) synergist assays. The presence of kdr-<it>w/e</it> and ace-1R point mutations responsible for DDT-pyrethroid and carbamate resistance mechanisms was also investigated by PCR.</p> <p>Results</p> <p>Propoxur resistance was found in 10 out of the 11 study sites. Resistance to three classes of insecticides was observed in five urban localities. Mortality rates in mosquitoes exposed to deltamethrin and propoxur did not show any significant difference (P > 0.05) but was significantly higher (P < 0.05) in populations exposed to DDT. All mosquitoes tested were identified as <it>A. gambiae s.s</it> (M form). The <it>kdr -w</it> point mutation at allelic frequencies between 45%-77% was identified as one of the resistant mechanisms responsible for DDT and pyrethroid resistance. <it>Ace-1R</it> point mutation was absent in the carbamate resistant population. However, the possible involvement of metabolic resistance was confirmed by synergistic assays conducted.</p> <p>Conclusion</p> <p>Evidence of carbamate resistance in <it>A. gambiae</it> populations already harbouring resistance to DDT and permethrin is a clear indication that calls for the implementation of insecticide resistance management strategies to combat the multiple resistance identified.</p