When intensity of deltamethrin resistance in Anopheles gambiae s.l. leads to loss of Long Lasting Insecticidal Nets bio-efficacy: a case study in north Cameroon

• Published in: Parasites & vectors 2016-03, Vol.9 (131), p.132, Article 132
• Main Authors: Etang, Josiane, Pennetier, Cédric, Piameu, Michael, Bouraima, Aziz, Chandre, Fabrice, Awono-Ambene, Parfait, Marc, Coosemans, Corbel, Vincent
• Format: Article
• Language: English
• Subjects: Animal biology; Animals; Anopheles; Anopheles - drug effects; Anopheles - genetics; Biological Assay; Cameroon; Control; DDT - pharmacology; Demographic aspects; Genotype; Genotyping Techniques; Insecticide Resistance; Insecticide-Treated Bednets; Insecticides; Insecticides - pharmacology; Invertebrate Zoology; Life Sciences; Malaria; Microbiology and Parasitology; Nitriles - pharmacology; Parasitology; Permethrin - pharmacology; Pesticide resistance; Physiological aspects; Pyrethrins - pharmacology; Risk factors; Santé publique et épidémiologie; Survival Analysis
• ISSN: 1756-3305; 1756-3305
• DOI: 10.1186/s13071-016-1420-x

In Cameroon, insecticide resistance in Anopheles (An.) gambiae s.l. has been reported in several foci, prompting further investigations on associated patterns of Long-Lasting Insecticidal Nets (LLINs) bio-efficacy. The current study, conducted from June to August 2011, explored the intensity of deltamethrin resistance in An. gambiae s.l. from Pitoa and its impact on the residual bio-efficacy of LifeNet, a LLIN with deltamethrin incorporated into polypropylene nets (PND). Two-four days old females An. gambiae s.l. reared from larval collections in Pitoa were tested for susceptibility to DDT, permethrin and deltamethrin, using standard World Health Organization (WHO) tube assays. Intensity of deltamethrin resistance was explored using WHO tube assays, but across six working concentrations from 0.001 % to 0.5 %. Bio-efficacy of unwashed and washed PND was assessed using WHO cone test. Species identification and kdr 1014 genotyping were performed on mosquito samples that were not exposed to insecticides, using PCR-RFLP and HOLA methods respectively. The Kisumu reference susceptible strain of An. gambiae s.s. was used for comparisons. A total of 1895 An. gambiae s.l. specimens from Pitoa were used for resistance and PND bio-efficacy testing. This mosquito population was resistant to DDT, permethrin and deltamethrin, with 18-40 min knockdown times for 50 % of tested mosquitoes and 59-77 % mortality. Deltamethrin Resistance Ratio compared with the Kisumu strain was estimated at ≥500 fold. LifeNets were effective against the susceptible Kisumu (100 % knockdown (KD60min) and mortality) and the resistant Pitoa samples (95 % KD60min, 83-95 % mortality). However, the bio-efficacy gradually dropped against the Pitoa samples when nets were washed (X (2) = 35.887, df = 8, p