Insecticide resistance status of the Anopheles funestus population in Central African Republic: a challenge in the war

Abstract

BackgroundIn 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.MethodsWHO 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).ResultsA 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).ConclusionEvidence 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.

Insecticide susceptibility of Anopheles stephensi to DDT and current insecticides in an elimination area in Iran

“…Similar trends have been reported from Middle East different regions, Indian subcontinent, and many African malaria endemic countries [23, 24, 27]. The use of pyrethroids as pesticides in agriculture and bed-net treatment has been recognized as factors responsible for the natural selection of resistant mosquitoes in sub-Saharan Africa [26, 28]. …”

“…However, in the recent years the efficacy of these insecticides against potential malaria vectors has been found to be reduced in endemic areas [24, 25]. In this regard, resistance of the malaria vectors to pyrethroids have been reported from some Afrotropical regions including Mozambique, Uganda, southern Africa, Benin and Ghana [26]. …”

“…stephensi as the main malaria vector to pyrethroid insecticides in the southeast of Iran. The emergence and rapid spread of insecticide resistance in Anopheles population may impair the effectiveness of malaria vector control measures which are based on the use of LLINs and IRS and therefore threaten the sustainability of the current strategies for malaria elimination [26, 29, 30]. Therefore, to implement a successful malaria control program it is vital to take into account the implications of insecticide resistance to pyrethroids.…”

Evidence of multiple insecticide resistance mechanisms in Anopheles gambiae populations in Bangui, Central African Republic

“…In the Central African Republic (CAR), malaria is the major public health problem and the leading cause of death among children [1, 2]. In Bangui, the capital of CAR, malaria represents over 58% of the reasons for consultations and 54% of hospital deaths among children [3].…”

Piperonyl Butoxide: An Enhancing Arsenal for an Adomant Foe

“…At present, LLINs are no longer showing the impact it has shown few decades ago in Africa where there has been reports of rapid decline of child mortality and mobidirty [7] due to mosquitoes insecticides resistance problem [8][9][10][11]. Changing of IRS compound have caused some resistant mosquitoes to be susceptible but with time they have built resistance [9,[12][13][14][15]. Inseticides detoxification enzymes have been expressed in higher level and caused insecticides tolerance which increases the survivorship of mosquitoes and increase the disease risk [16].…”