Insecticide treatments for crops protection in cotton fields have often been cited as the main factor in the selection of insecticide resistance in Anopheles gambiae populations. To explore this hypothesis further, the present study was designed to identify potential practices that may contribute to the emergence of insecticide resistance in Anopheles gambiae in cotton crop protection strategies such as the “Calendar Control Program (CCP)” and “Targeted Intermittent Control Program (TICP)” officially recommended already operate in Benin. Firstly, Knowledge Attitude-Practice (KAP) surveys were organized in the study sites to generate adequate information on the use of insecticide on cotton fields. In each site, leaders of farmer’s organizations were interviewed using semi-structured questionnaires that focused on the treatment strategies, and the use of insecticides in the farms. Further, bioassays were performed on adult mosquitoes collected from various of each program to assess the susceptibility of malaria vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. Results of this study showed that various pesticides particularly pyrethroids were used for pests control in CCP and TICP sites; ii)-Susceptibility tests showed that An. gambiae populations have developped resistance to DDT (4% as mean mortality despite the strategies), permethrin (30% in CCP and TICP), deltamethrin (38% and 46% as mean mortality in CCP and TICP respectivetly), but fully susceptible to bendiocarb . These findings confirmed the role of insecticide treatments in mosquitoes resistance. Measure must be taken for better management of the use of insectides for pest control.

For better management of the use of insecticide in public health against Culex quinquefasciatus, an arboviral and filarial vector, a study was conducted at Natitingou, a town located in northern Benin, from October 2015 to March 2016, to evaluate the susceptible of this mosquito to insecticides and the mechanisms of resistance developed. The protocol was based on mosquito collection during both dry and rainy seasons across the four areas selected in northern Benin. Bioassays were performed on adult mosquitoes collected from the field to assess the susceptibility of filarial vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. Moreover, mosquitoes from the susceptible tests were used to search for the presence of the knock down resistance (Kdr) and the Acethylcholinesterase (Ace-1R) mutations. Finally, F1 generation of the wild population of Cx. quinquefasciatus were used for biochemical analysis to target Mixed Function Oxidase (MFO), non-speci?c esterase (NSE) and glutathione-S-transferases (GST) enzymes. This research showed: 1)-A wide spread of resistance to permethrin, delthamethrin and DDT was found in samples of Cx. quinquefasciatus despite the collection areas with 4%; 7% ; 19% and 60% as average of mortality respectively with DDT, permethrin, deltamethrin and bendiocarb; 2)- The kdr mutation was detected in all areas at various frequencies (0.8 to 0.88) whereas the Ace-1 mutation was found at a very low frequency (? 5%); 3) - Enzymes activities (oxidase, esterase and glutathion-S-transferases) were detected in all mosquito populations despite the areas of collection. This work has highlighted the high resistance of Cx. quinquefascitus to the 3 classes of insecticides used in public health. Moreover, the high frequency of kdr and the presence of enzyme activity in Cx. quinquefasciatus will augment the existing data on the insecticide resistance of filariasis vectors and will be useful for making decision to control this mosquito.

Background: Agricultural pesticides may play a profound role in selection of resistance in field populations of mosquito vectors. The objective of this study is to investigate possible links between agricultural pesticides use and development of resistance to insecticides by the major malaria vector Anopheles gambiae from cotton field.
Method: Susceptibility to 4% DDT, 0.05% deltamethrin, 0.75% permethrin, 0.1% bendiocarb was assessed using the WHO standard procedures for adult mosquitoes from cotton field. Tests were carried out with two to three days-old, non-engorged female mosquitoes. The An. gambiae Kisumu strain was used as a reference. Knockdown effect was recorded every 5 min and mortality scored 24 h after exposure. Mosquitoes were identified to species and molecular form by PCR-RFLP and genotypes at the knock down resistance (kdr) and, acetylcholinesterase mutations were determined in surviving specimens.
Results: During this survey, full susceptibility to bendiocarb was recorded in all samples. WHO diagnostic tests showed high frequency of resistance in An. gambiae to permethrin (ranging from 3% to 4% mortality), deltamethrin (13% to 22%), DDT (1.01% to 2%) in the seven selected areas. The Kdr gene seemed the main target- site resistance mechanism detected at the rates ranging from ranging from 65 to 71%.
The frequency of ace-1R gene was found but at very low frequency (< 0.1).
Conclusion: This investigation of malaria vector susceptibility to insecticides revealed a strong resistance to pyrethroid insecticides (permethrin and deltamethrin).
This Pyrethroid resistance may seriously jeopardize the efficacy of of IRS and LLINs on which, most African countries including Benin, rely to reduce malaria transmission.
The current findings will help for decision making in the National Malaria control program particularly in the choice of insecticide to use during campaigns of Indoor residual spraying in this part of Benin.

Background: Aedes aegypti is present year round in several cities of the Republic of Benin. This study aims to assess the seasonal distribution of this mosquito at Dandji, in southern Benin.
Method: A cross seasonal entomological study on larvae and adults of Ae. aegypti was carried out from May 2013 to April 2014 in southern Benin (Dandji). The study was based on sampling Ae. aegypti immature stages (larvae/pupae) from domestic, peri-domestic and natural water sources and were reared to adults. The collections were made during the dry and rainy seasons. Addional Ae. aegypti were collected by Human Landing Catches (HLC), Indoor Pyrethrum Spray Catches (PSC), Biogents (BG) sentinel trap and Gravid traps (GT).
Results: During the year of study, a total number of 18,658 mosquitoes were collected where 15,204 were collected by HLC; 303 with BG trap, 3,038 with PSC, 48 with the GT. Among the 18, 593 of Ae. aegypti collected, the female populations (13,834) was significantly higher than the male populations (p<0.05). From the 13,834 females, 1,380 were blood-fed.
Adult's collection was high during the two rainy seasons (June to July and October to November) but declined in the two dry seasons (December to March and August to September).
At Dandji, the average of Human Biting Rates (HBR) obtained during the rainy seasons (79.6 bites/p/n) was significantly higher than those obtained during the dry seasons (58.62 bites/p/n) (p < 0.05).
Conclusion: These findings showed the presence of Aedes aegypti year round at Dandji in southern Benin. This presence is strengthening with the trade of second hand tires which are good breeding sites for the development of Ae. aegypti. Data on blood feeding patterns of Ae. aegypti collected during this study will certainly provide valuable information about potential Dengue virus (DENV) hosts others than humans and will help to get a greater understanding about DENV ecology in Benin. It is therefore crucial for health authorities of Benin to develop a program to fight against this mosquito in order to avoid an outbreak of DENV as it was the case in many sub Saharan Africa countries recently.