The use of some pyrethroids (insecticides), their combination and synergist on Anopheles mosquitoes in Isoko South, Delta State

Abstract

Humans get infected with malaria parasites (Plasmodium species) through the bites of infected female Anopheles mosquitoes. Malaria incidence is rapidly increasing and insecticide resistance remains a global threat to vector control programmes. Considering the fact that susceptibility studies are lacking in Delta State, this present study evaluates the efficacy of using some insecticides (deltamethrin and permethrin), their combination and synergists (PBO) on the female Anopheles mosquitoes in Isoko
South LGA. Larva and pupa of Anopheles mosquitoes were collected using 350 ml dippers. Two to five day-old emerged females were exposed to 0.75% deltamethrin and 0.05% Permethrin using the WHO bioassay and CDC bottle assay methods (combination) in four replicates. Percentage knock down time for 50 and 95% was determined using probit analysis. Mosquitoes’ susceptibility to
permethrin and deltamethrin was 72 and 87%, respectively and were termed resistant following WHO standard protocol. In the combined forms, mortality of 71 and 99% was recorded at 15 and 30 min, respectively. The differences between insecticides and combined forms were highly significant (P<0.0001). Synergized permethrin and deltamethrin recorded high susceptibility of 99 and 98%, respectively. The highest percentage knock down was recorded with synergized permethrin and deltamethrin at 60 min of exposure and the difference was significant (P<0.05). KDT50 and KDT95 ranged between 38.99 and 57.06 and 147.17 and 284.66 min, respectively. Synergized permethrin recorded the lowest (38.99 and 147.17 min, respectively). In conclusion, synergized forms of deltamethrin and permethrin could be adopted for the control of Anopheles mosquitoes’ population. This could be used for impregnating bed nets as it would be effective against the spread of malaria in Isoko South Local Government Area.