Insecticide susceptibility of Anopheles coluzzii and Anopheles gambiae mosquitoes in Ibadan, Southwest Nigeria

Abstract

The emergence of insecticide resistance in Anopheles mosquitoes has great implications for malaria control in Nigeria. This study aimed to determine the dynamics of insecticide susceptibility levels and frequency of knockdown resistance (kdr) mutations (L1014F) in wild Anopheles coluzzii Coetzee & Wilkerson sp. n. and An. gambiae Giles ( (Diptera: Culicidae) from Ojoo and Bodija areas of Ibadan, South-West, Nigeria. Insecticide susceptibility to pyrethroids, organophosphates, carbamates and organochlorines was assessed using WHO bioassays. A subset of the mosquitoes exposed to pyrethroids and DDT was used for species and molecular form identification and kdr genotyping was determined using the Taqman real time PCR assay. The mosquitoes were resistant to pyrethroids and DDT but completely susceptible to organophosphates and carbamates. Bodja samples (n=186) comprised of An. gambiae (91.4%) and An. coluzzii (8.1%) while one An. coluzzii / An. gambiae hybrid was recorded. All mosquitoes screened in Ojoo (n=26) were An. gambiae. The 1014F kdr mutation was detected at a frequency of 24.52% and 5.8% in Bodija and Ojoo respectively. No correlation was observed between kdr genotypes and resistance phenotypes. The results indicate that metabolic resistance probably plays an important role in the resistance and highlights the need to implement insecticide resistance management strategies.

Distribution of members of the Anopheles gambiae complex in selected forested tourist areas of Cross River State, Nigeria

“…In addition, this study found a hybrid form of A. gambiaes.s./A.coluzzii, which agrees with the findings from two recent studies [22]. The findings from our study and the previous reports showed that the hybridization of A. gambiaes.s./A.coluzzii is still rare with these two studies [21][22] reporting its occurrence in Nigeria at a low prevalence that ranges between 0.5% -0.8 %. Although, the epidemiological implication of the hybrid form to malaria control is still unclear, it should be a cause for concern because of the possible transference of "knock down resistant gene" (kdr gene) from A. gambiae to A.coluzzii [32,[36][37].…”

“…It is believed that small collections of water from rainfall and human activities will encourage A. gambiaes.s. to breed, in addition to the availability of blood meals from humans [6,21,38]. This was evident in the distribution of A. gambiae s.s in CRNP at 40% compared to 4% caught at Drill Ranch and none from Rhoko forest.…”

“…Studies in Lagos, South Western Nigeria which lies in the forest ecological zone of Nigeria [17][18] and Kano, Northern Nigeria in Savannah ecological zone of Nigeria [19] showed that A. coluzzii is more abundant than A. gambiae. However, this is in contrast with the previous report from a wider surveillance which showed that the molecular S form (now known as A. gambiae) is predominant and has a wider distribution across Nigeria compared to A. coluzzii [7][8][9][10][11][12][13][14][15][16][17][18][19][20] .Hybridization of the two species is rarely reported to occur, however,the hybrid form was recently reported in Nigeria by two studies from South Western Nigeria [21] and North Central Nigeria [22] respectively. The rainforest belt of Nigeria where Cross River State (CRS) is located has a fairly large population of very rare wildlife.…”

Evidence of a multiple insecticide resistance in the malaria vector Anopheles funestus in South West Nigeria

“…However, this high frequency of L119F in this location is probably the reason why a lack of correlation was observed when comparing resistant and susceptible samples as observed regularly for kdr mutations such as L1014F in An. gambiae in situation when the 1014F resistant allele is nearly fixed [55]. The L119F-GSTe2 mutation has also been detected in other DDT resistant populations such as Ghana (44.2%) and Burkina-Faso (25%) in West Africa, and Cameroon (48.2%) in Central Africa [20, 23] as well as Uganda (20.4%) and Kenya (7.8%) in East Africa [12].…”

Insecticide Susceptibility Status of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in Awka South Local Government Area, Anambra State, Nigeria

“…The mechanisms responsible for resistance to insecticides used in mosquito control has also been identified and are of two main types namely; those mediated by changes at the target site of the insecticide (e.g. kdr mutations) and those caused by increase in the rate of insecticide metabolism resulting in increased metabolic detoxification [9,18]. Resistance to multiple insecticides (pyrethroids and organophosphates) has been reported in Ae.…”