Rapid evolution of insecticide resistance and patterns of pesticides usage in agriculture in the city of Yaoundé, Cameroon

Abstract

Background The practice of agriculture in urban settings contributes to the rapid expansion of insecticide resistance in malaria vectors. However, there is still not enough information on pesticide usage in most urban settings. The present study aims to assess the evolution of Anopheles gambiae (s.l.) population susceptibility to insecticides and patterns of pesticide usage in agriculture in the city of Yaoundé, Cameroon. Methods WHO susceptibility tests and synergist PBO bioassays were conducted on adult An. gambiae (s.l.) mosquitoes aged 3 to 5 days emerging from larvae collected from the field. Seven insecticides (deltamethrin, permethrin, DDT, bendiocarb, propoxur, fenitrothion and malathion) were evaluated. The presence of target site mutation conferring knockdown (kdr) resistance was investigated using TaqMan assay, and mosquito species were identified using SINE-PCR. Surveys on 81 retailers and 232 farmers were conducted to assess general knowledge and practices regarding agricultural pesticide usage. Results High resistance intensity to pyrethroids was observed with a high frequency of the kdr allele 1014F and low frequency of the kdr 1014S allele. The level of susceptibility of An. gambiae (s.l.) to pyrethroids and carbamates was found to decrease with time (from > 34% in 2017 to < 23% in 2019 for deltamethrin and permethrin and from 97% in 2017 to < 86% in 2019 for bendiocarb). Both An. gambiae (s.s.) and An. coluzzii were recorded. Over 150 pesticides and fertilizers were sold by retailers for agricultural purposes in the city of Yaoundé. Most farmers do not respect safety practices. Poor practices including extensive and inappropriate application of pesticides as well as poor management of perished pesticides and empty pesticide containers were also documented. Conclusions The study indicated rapid evolution of insecticide resistance and uncontrolled usage of pesticides by farmers in agriculture. There is an urgent need to address these gaps to improve the management of insecticide resistance. Graphical Abstract

Pyrethroid Resistance Situation across Different Eco-Epidemiological Settings in Cameroon

“…to both deltamethrin and permethrin was recorded in all sites. The resistance profile detected during the present study, was in accordance with studies conducted so far across the country, suggesting rapid expansion of insecticide resistance in vector populations [ 5 , 7 , 35 ]. Similar evolution of pyrethroid resistance patterns have been reported across Africa [ 6 , 18 , 25 ].…”

“…It is likely that mosquitoes in the sites of Kaélé, Santchou, Kékem and Bélabo are exposed to additional selective pressure resulting from the use of pesticides in agriculture and or public health. A recent study indicated the use of a large variety of compounds, including herbicides, fungicides and insecticides, in agriculture in Cameroon [ 7 ]. Kaélé is situated in an area with intense cultivation of cotton.…”

“…It is possible that the increasing use of LLINs may have contributed to increase insecticide selective pressure on mosquito populations. Moreover, the uncontrolled use of pesticides in agriculture is also considered to contribute to vector resistance to pyrethroids [ 5 , 6 , 7 ].…”

“…Although in recent years there have been an increasing number of studies assessing pyrethroid resistance levels in malaria vectors in Cameroon [ 7 , 8 , 15 , 16 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ], there is still not enough data providing a global picture of the pyrethroid resistance situation in different eco-epidemiological settings. The present study aimed to provide updated data on pyrethroid resistance profiles in An.…”

DDT Resistance in Anopheles pharoensis from Northern Cameroon Associated with High Cuticular Hydrocarbon Production

“…funestus populations across Cameroon. characterized by no or very low mortality rates to this compound [ 17 , 18 , 19 ]. To our knowledge, this is the first report of insecticide resistance in An.…”