The importance of considering community-level effects when selecting insecticidal malaria vector products

BACKGROUND\ud \ud Insecticide treatment of nets, curtains or walls and ceilings of houses represent the primary means for malaria prevention worldwide. Direct personal protection of individuals and households arises from deterrent and insecticidal activities which divert or kill mosquitoes before they can feed. However, at high coverage, community-level reductions of mosquito density and survival prevent more transmission exposure than the personal protection acquired by using a net or living in a sprayed house.\ud \ud METHODS\ud \ud A process-explicit simulation of malaria transmission was applied to results of 4 recent Phase II experimental hut trials comparing a new mosaic long-lasting insecticidal net (LLIN) which combines deltamethrin and piperonyl butoxide with another LLIN product by the same manufacturer relying on deltamethrin alone.\ud \ud RESULTS\ud \ud Direct estimates of mean personal protection against insecticide-resistant vectors in Vietnam, Cameroon, Burkina Faso and Benin revealed no clear advantage for combination LLINs over deltamethrin-only LLINs (P = 0.973) unless both types of nets were extensively washed (Relative mean entomologic inoculation rate (EIR) ± standard error of the mean (SEM) for users of combination nets compared to users of deltamethrin only nets = 0.853 ± 0.056, P = 0.008). However, simulations of impact at high coverage (80% use) predicted consistently better impact for the combination net across all four sites (Relative mean EIR ± SEM in communities with combination nets, compared with those using deltamethrin only nets = 0.613 ± 0.076, P < 0.001), regardless of whether the nets were washed or not (P = 0.467). Nevertheless, the degree of advantage obtained with the combination varied substantially between sites and their associated resistant vector populations.\ud \ud CONCLUSION\ud \ud Process-explicit simulations of community-level protection, parameterized using locally-relevant experimental hut studies, should be explicitly considered when choosing vector control products for large-scale epidemiological trials or public health programme procurement, particularly as growing insecticide resistance necessitates the use of multiple active ingredients

Susceptibility status of mosquitoes (Diptera: Culicidae) to Malathion in Lagos, Nigeria

Mosquitoes are major vectors of infectious diseases transmitting malaria,&nbsp; lymphatic filariasis, yellow fever, dengue fever, zika and chikungunya virus.&nbsp; Resistance to DDT, pyrethriods and carbamates has been reported to different mosquito species in Nigeria. This investigation was carried out to determine the susceptibility status of mosquitoes in Lagos State, Nigeria to malathion. Mosquito larva were collected from four different Local Government Areas of Lagos, and reared to adult. Female adult mosquitoes were exposed to 5 % malathion insecticide test papers using WHO standard procedures and kits. Species identification was done using PCR assay. Suspected resistance was observed in Cx. quinquefasciatus from Kosofe and Alimosho with 24 hour mortality of 96 % and 95 % respectively. Other mosquito species and Cx. quinquefasciatus from Badagry and&nbsp; Ibeju-Lekki were fully susceptible 24 hours post exposure period. KDT50 and KDT95 for An. gambiae s.s ranges from 14.6 – 25.1 and 23.7 – 51.5 minutes respectively for all the location, KDT50 and KDT95 for Ae. aegypti ranges from 24.8 – 27.8 and 44.8 – 62.5 minutes respectively for all the location and KDT50 and KDT95 for Cx. quinquefasciatus ranges from 21.5 – 37.8 and 41.5 – 77.7 minutes respectively for all the location. The relatively high values of KDT50 and KDT95 in all assayed mosquito species call for urgent attention and may indicate the gradual development of malathion resistance to different mosquito species in Lagos. Regular insecticide resistance monitoring is needed and the indiscriminate use of unapproved organophosphate insecticides to be discouraged to forestall the development of malathion resistance in mosquitoes. Keywords: Mosquitoes, Insecticide resistance, Malathion, Organophosphates, Infectious disease