Determining the species composition, density of Anopheles mosquitoes and sensitivity to insecticides of the primary vector of malaria transmission in Cai Nuoc district, Ca Mau province in 2023

Abstract

Cross-sectional descriptive study and controlled field trials were conducted from April to December 2023 in Dong Hung and Tran Thoi commune, Cai Nuoc district, Ca Mau province, to assess the species composition and density of Anopheles mosquitoes and the susceptibility of An. epiroticus to some insecticidal chemicals used in malaria prevention programs. The results collected 789 Anopheles mosquitoes and 201 Anopheles larvae, including 3 species: An. epiroticus, An. nimpe and An. sinensis. Among them, An. epiroticus, the primary malaria vector, dominated at 94.03% (714/789), followed by An. nimpe 9.00% (71/789), An. sinensis with the lowest rate of 0.51% (4/789). The species composition of Anopheles in Ca Mau province has been relatively stable over the years. At the research sites, the density of the collected An. epiroticus outdoor collections was 17.00 individuals/hour/person and in indoor collections was 11.50 individuals/ hour/ person, indoor screening was 3.0 individuals/ person. The densities of the collected An. nimpe and An. sinensis in outdoor collections were 2.04 and 0.13, and in indoor collections were 0.88 and 0.04, respectively. Outdoor mosquito density was 1.48 times higher than indoor mosquito density. The An. epiroticus density in Tran Thoi commune was about 3.38 - 4.00 times higher than Dong Hung commune. The density of larvae An. epiroticus dominated the population of 18.9 individuals/10 patches. The density of larvae An. nimpe was 1.2 individuals/10 patches. The density of larvae An. epiroticus in Tran Thoi commune was 3.5 times higher than in Dong Hung commune. An. epiroticus in Cai Nuoc district, Ca Mau province resistanted to alphacypermethrin 0.08%, lambdacyhalothrin 0.05%, deltamethrin 0.05% and permethrin 0.75% with mosquito death rate after 24 hours in biological testing from 47 - 89%. An. epiroticus in Cai Nuoc district, Ca Mau province, is still susceptible to the chemical malathion 5%.