Abstract
Insecticide resistance in Aedes spp is a major concern to yellow fever vector control programmes, in particular in Awka, Nigeria owing to the dense population of monkeys and the tradition that barns the killing of monkeys in this area. The study was aimed to determine the insecticide susceptibility status of Aedes aegypti and Aedes albopictus in Awka South, Anambra state, Nigeria. Locally modified American Centre for Disease Control (CDC) ovitraps were used for the collection of Ae. aegypti and Ae. albopictus eggs from Ifite, Awka. The eggs were reared to adult stage at the insectary unit of National Arbovirus and Vectors Research Centre, Enugu and the first generation progeny (F1) exposed to WHO insecticide impregnated papers. The treatments used for the two species consist of carbamates (0.1% propoxur), organophosphates (0.25% pirimiphos-methyl), pyrethroids (0.05% deltamethrin) and organochlorines (4% DDT). The result showed Ae. aegypti to be susceptible to primiphos-methyl (98.75%) and deltamethrin (100%), tolerant to propoxur (97.3%) and resistant to DDT (10.55%) while Ae. albopictus were susceptible to propoxur (100%), resistant to DDT (62.5%) and showed possibility of resistance to primiphos-methyl (97.5%) and deltamethrin (93.6%). Knock down times (KDT50 and KDT95) are as follows; For Ae. aegypti- propoxur (4.26 and 39.79mins), pirimiphos-methyl (4.18 and 41.35mins), deltamethrin (3.77 and 17.27mins), DDT (53.33 and 248.53mins) and for Ae. albopictus- propoxur (30.19 and 54.76mins), pirimiphos-methyl (1.12 and 195.02mins), deltamethrin (5.88 and 46.39mins), DDT (45.94 and 176.16mins). This study clearly demonstrates that both Ae. aegypti and Ae. albopictus are resistant to DDT. Also, frequent use of these insecticides for vector control interventions (long lasting insecticide nets and indoor residual spraying) in Nigeria may result to resistance in deltamethrin and pirimiphos-methyl. There is therefore urgent need to implement proper insecticide resistance management strategies in line with international best practices in this area.
Highlights
Insecticide resistance in the major tropical arbovirus vector, Aedes aegypti and Aedes albopictus (Diptera: Culicidae) is common in West Africa
The result showed that propoxur, pirimiphos-methyl, deltamethrin and DDT recorded mortalities of 97.50%, 98.75%, 100% and 12.50% respectively (Table 1)
The mosquito populations were susceptible to propoxur (97.50% mortality), Pirimiphos-methyl (98.75% mortality) and deltamethrin (100% mortality) respectively
Summary
Insecticide resistance in the major tropical arbovirus vector, Aedes aegypti and Aedes albopictus (Diptera: Culicidae) is common in West Africa. This presents a major challenge in the control of yellow fever and other arboviral diseases in this region [1]. Ae. albopictus was first discovered by Skuse in 1894 from specimens collected in the city of Calcutta on the Indian subcontinent [4]. This species has since expanded its distribution to other continents except Antarctica [4]. The breeding of Ae. albopictus was first noticed in Nigeria
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