Insecticide resistance status of the Anopheles funestus population in Central African Republic: a challenge in the war.
BACKGROUND
In the Central African Republic, malaria is a major public health problem and the leading cause of death among children. This disease appears to be hyperendemic but no substantial entomological data, including data on Anopheles spp. susceptibility to insecticides, is available. This study evaluates, for the first time in the CAR, the status of insecticide resistance in the Anopheles funestus population, the second major vector of malaria in Africa.


METHODS
WHO standard bioassay susceptibility tests were performed on the An. funestus population using F1 generation from gravid females mosquitoes (F0) collected by manual aspirator sampling of households in Gbanikola, Bangui in October 2014 to assess: (i) An. funestus susceptibility to bendiocarb, malathion, permethrin, lamda-cyhalothrin, deltamethrin and DDT, and (ii) the effect of pre-exposure to the piperonyl butoxide (PBO) synergist on insecticide susceptibility. Additional tests were conducted to investigate metabolic resistance status (cytochrome P450 monooxygenases, glutathione S-transferases, and esterases).


RESULTS
A high phenotypic resistance of An. funestus population to malathion, DDT and pyrethroids was observed with a mortality rate ranging from 23 to 74%. For the pyrethroid groups, the mortality rate was 35, 31 and 23% for lambda-cyhalothrin, deltamethrin, and permethrin, respectively. In contrast a 100% mortality rate to bendiocarb was recorded. Knockdown time (KDT) was long for all pyrethroids, DDT and malathion with KDT50 higher than 50 min. Pre-exposure of An. funestus to PBO synergist significantly restored susceptibility to all pyrethroids (Fisher's exact test P <0.0001) but not in DDT (Fisher's exact test P = 0.724). Data from biochemical tests suggest the involvement of cytochrome P450 monooxygenases, esterases and glutatione S-transferases in the resistance of An. funestus population from Gbanikola (Wilcoxon test P <0.05).


CONCLUSIONS
Evidence of biochemical resistance to insecticide was detected in An. funestus population from the district of Gbanikola, Bangui. This study suggests that detoxifying enzymes are involved in insecticide resistance of An. funestus. However, despite disruptive violence, further research is urgently needed to assess the insecticide susceptibility status of An. funestus population in all CAR regions; insecticide resistance could rapidly compromise the success of malaria control programs.
G4 Malaria Group Institut Pasteur in Bangui, Bangui, Central African Republic.|Faculté des Sciences et Techniques, Université d'Abomey Calavi, Cotonou, Bénin.
Marina Lidwine Olé
ML
Sangba
G4 Malaria Group Institut Pasteur in Bangui, Bangui, Central African Republic.|Faculté des Sciences et Techniques, Laboratoire de Biologie Animale Appliquée et de Biodiversité, Université de Bangui, Bangui, Central African Republic.
Tanguy
T
Deketramete
Faculté des Sciences et Techniques, Laboratoire de Biologie Animale Appliquée et de Biodiversité, Université de Bangui, Bangui, Central African Republic.
Solange Patricia
SP
Wango
Virology Department, Institut Pasteur in Bangui, Bangui, Central African Republic.
Mirdad
M
Kazanji
Faculté des Sciences et Techniques, Université d'Abomey Calavi, Cotonou, Bénin.|Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, 06 BP 2604, Bénin.
Martin
M
Akogbeto
G4 Malaria Group Institut Pasteur in Bangui, Bangui, Central African Republic. ousmane.ndiath@gmail.com.
Mamadou Ousmane
MO
Ndiath
D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D002488:Central African Republic; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004950:Esterases / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*
D007306:Insecticides; D003577:Cytochrome P-450 Enzyme System; D005982:Glutathione Transferase; D004950:Esterases
Anopheles funestus; Bangui; Central African Republic; Insecticide resistance; Malaria; kdr