[The Anopheles gambiae species complex and Kdr resistance gene at the periphery of Douala, Cameroon]. / Le complexe d'espèces Anopheles gambiae et le gène de résistance Kdr en périphérie de Douala, Cameroun.

This study was conducted from May to June 2015 in Yassa (industrialized area) and Logbessou (non-industrialized area), two peri-urban areas of the city of Douala, Cameroon with the aim of an assessment of the spatial distribution of the gambiae complex, the determination of their resistance to insecticides and the distribution of the Kdr mutation. Mosquito larvae were collected by the dipping method and nursed to adult stage. The sensitivity of adult Anopheles gambiae s.l. populations to DDT and pyrethroids was assessed following WHO protocol. All tested mosquitoes were identified by PCR SINE. Only survivors were used to search for the Kdr mutation. In both areas, the gambiae complex included An. coluzzii and An. gambiae sympatric in their breeding sites. However, An. gambiae was predominant in Logbessou (88%) and An. coluzzii in Yassa (68%). Tests with deltamethrin, permethrin and DDT revealed mortality rates below 90% regardless of the area of origin of the mosquitoes. PCR diagnosis of Kdr mutation showed that over 95% of survivors harbored the Kdr gene in both sites, with resistant allele frequencies ranging from 0.96 to 1.0 in An. gambiae and from 0.89 to 0.96 in An. coluzzii. The strong resistance of An. coluzzii and This study was conducted from May to June 2015 in Yassa (industrialized area) and Logbessou (nonindustrialized area), two peri-urban areas of the city of Douala, Cameroon with the aim of an assessment of the spatial distribution of the gambiae complex, the determination of their resistance to insecticides and the distribution of the Kdr mutation. Mosquito larvae were collected by the dipping method and nursed to adult stage. The sensitivity of adult Anopheles gambiae s.l. populations to DDT and pyrethroids was assessed following WHO protocol. All tested mosquitoes were identified by PCR SINE. Only survivors were used to search for the Kdr mutation. In both areas, the gambiae complex included An. coluzzii and An. gambiae sympatric in their breeding sites. However, An. gambiae was predominant in Logbessou (88%) and An. coluzzii in Yassa (68%). Tests with deltamethrin, permethrin and DDT revealed mortality rates below 90% regardless of the area of origin of the mosquitoes. PCR diagnosis of Kdr mutation showed that over 95% of survivors harbored the Kdr gene in both sites, with resistant allele frequencies ranging from 0.96 to 1.0 in An. gambiae and from 0.89 to 0.96 in An. coluzzii. The strong resistance of An. coluzzii and This study was conducted from May to June 2015 in Yassa (industrialized area) and Logbessou (nonindustrialized area), two peri-urban areas of the city of Douala, Cameroon with the aim of an assessment of the spatial distribution of the gambiae complex, the determination of their resistance to insecticides and the distribution of the Kdr mutation. Mosquito larvae were collected by the dipping method and nursed to adult stage. The sensitivity of adult Anopheles gambiae s.l. populations to DDT and pyrethroids was assessed following WHO protocol. All tested mosquitoes were identified by PCR SINE. Only survivors were used to search for the Kdr mutation. In both areas, the gambiae complex included An. coluzzii and An. gambiae sympatric in their breeding sites. However, An. gambiae was predominant in Logbessou (88%) and An. coluzzii in Yassa (68%). Tests with deltamethrin, permethrin and DDT revealed mortality rates below 90% regardless of the area of origin of the mosquitoes. PCR diagnosis of Kdr mutation showed that over 95% of survivors harbored the Kdr gene in both sites, with resistant allele frequencies ranging from 0.96 to 1.0 in An. gambiae and from 0.89 to 0.96 in An. coluzzii. The strong resistance of An. coluzzii and An. gambiae to insecticides highlights the need for developing new mosquito insecticides.

Malaria transmission and the sensitivity of aggressive mosquitoes to insecticides in a poorly urbanized area of the Deido health district in Douala (Cameroon).

The design of an appropriate strategy for mosquito control in urban areas must take into account the local ecoclimate and its particularities. This study sought to determine the dynamics of malaria transmission and the level of insecticide susceptibility of aggressive mosquitoes in Ndogbong, a poorly urbanized district of Douala. Mosquitoes were captured on volunteers in 4 houses and outdoors for 2 consecutive nights a month, from April to September 2014, and identified by molecular and morphologic techniques. The infectivity of vectors was determined by a circumsporozoite protein (CSP) ELISA test. The susceptibility of vectors to DDT, deltamethrin, and permethrin was also assessed. Overall, 3794 mosquitoes belonging to 6 species were captured in 96 person-nights. The aggressive mosquito fauna comprised : Culex pipiens (57.83%), Cx. poicilipes (1.45%), Anopheles gambiae s.l. (39.01%), Aedes albopictus (1.51%), and An. paludis (0.10%). An. coluzzii accounted for 97% of members of the Gambiae complex captured and was the only species found to be infected with P. falciparum, with an average infection rate of 1.9% (95% CI : 0.82-4.41). The mean entomological inoculation rate was estimated at 0.3 ib/p/n. Susceptibility testing on female An. gambiae s.l. and Cx. pipiens revealed mortality rates lower than 85 % and thus suggested strong resistance to insecticides. An. Coluzzii develops well in poorly urbanized built-up areas of Africa and appears to be the major malaria vector in Ndogbong, especially during the rainy season. The high resistance to insecticides observed requires the development of new formulations for insecticides.

[Anopheles gambiae, major malaria vector in Logbessou, a peri-urban area of Douala (Cameroon)]. / Anopheles gambiae, vecteur majeur du paludisme à Logbessou, zone péri-urbaine de Douala (Cameroun).

An entomological survey was carried out from August to November 2013, in order to determine the vector system of a building site for social housing in a coastal periurban district of Douala (Cameroon). Mosquito larvae were collected and adult endophilic mosquitoes captured on volunteers, for a total sample of 4897 mosquitoes. Morpho-taxonomic techniques alongside molecular techniques enabled the identification of 4 species, all aggressive to humans: Cx. pipiens (22.3%), Ae. albopictus (0.3%), An. coluzzii and An. gambiae (77.4%). The overall average biting rate recorded was 41.73 bites/person/night (b/p/n). An. gambiae s.l. represents 90.82% of this aggressive fauna, followed by Cx. pipiens (8.58%) and Ae. albopictus (0.6%). The detection of CSP showed that An. gambiae was responsible for 100% of P. falciparum transmission. The overall mean Entomological Inoculation Rate (EIR) was 3.94 ib/p/n. Female An. gambiae mortality rates were 14.47%, 82.5% and 100% respectively with DDT, permethrin and deltamethrin. The proliferation of An. gambiae in this area during raining season, at the detriment of An. coluzzii Coetze & Wilkerson and An. melas Theobald known to be major malaria vectors in island and coastal areas of Africa, may owe to the forest that still colonises this coastal peri-urban locality. Residents should therefore make use of deltamethrin based protective measures.

Polymorphic chromosomal inversions in Anopheles moucheti, a major malaria vector in Central Africa.

Anopheles moucheti Evans (Diptera: Culicidae) is a major vector of malaria in forested areas of Central Africa. However, few genetic tools are available for this species. The present study represents the first attempt to characterize chromosomes in An. moucheti females collected in Cameroon. Ovarian nurse cells contained polytene chromosomes, which were suitable for standard cytogenetic applications. The presence of three polymorphic chromosomal inversions in An. moucheti was revealed. Two of these inversions were located on the 2R chromosome arm. The homology between the 2R chromosome arms of An. moucheti and Anopheles gambiae Giles was established by fluorescent in situ hybridization of six An. gambiae genic sequences. Mapping of the probes on chromosomes of An. moucheti detected substantial gene order reshuffling between the two species. The presence of polytene chromosomes and polymorphic inversions in An. moucheti provides a new basis for further population genetic, taxonomic and ecological studies of this neglected malaria vector.

X-ray sterilization of the An. arabiensis genetic sexing strain 'ANO IPCL1' at pupal and adult stages.

With a view to area wide integrated pest management programs with a sterile insect technique (SIT) component against the malaria vector Anopheles arabiensis, the effects of X-ray exposure of males of the genetic sexing strain (GSS) of An. arabiensis, "ANO IPCL1" have been tested. The suitability of X-ray was assessed in comparison to gamma-ray for mosquito sterilization in operational settings where the acquisition of gamma ray irradiators may be problematic. Pupae and adult males were sterilized using X-ray irradiation at 5 increasing doses and effects were observed in terms of fecundity and fertility. Irradiated pupae and adults were further observed for effects on longevity. The adult stage appeared to be more sensitive to radiation exposure than the pupal stage, with a residual fertility of 1% in adults irradiated at 75Gy and 0% at 105Gy, compared to 8%at 75Gy and 4% at 105Gy in adults irradiated at the pupal stage. All treatment groups except those irradiated at 60Gy were statistically different from the control groups in terms of adult longevity post treatment, however overall survival was not highly compromised in the 75Gy treatment group which showed 96% of induced sterility. To ensure the fine balance between the induced sterility and the fitness of the insect produced is achieved, irradiation of adults at this dose may be a good compromise for the SIT as applied for this species, especially in specific cases such as sterilization after female elimination by spiking blood meals. Investigation into the combined effects of blood spiking and irradiation at the adult stage and additional competitiveness studies both in laboratory and field cages will provide more insight into the radiation dose and mosquito stage to be used in the frame of future SIT programs targeting this important malaria vector.

Epidemiological Importance of the Anopheles Nili Group of Malaria Vectors in Equatorial Villages of Cameroon; Central Africa

From March 1999 to March 2007; entomological surveys were conducted in eight riverside locations of the equatorial domain in Cameroon; to assess the contribution of Anopheles nili group to malaria transmission. Results showed that the anthropophilic Anopheles nili; Anopheles carnevalei and Anopheles ovengensis were involved in 5-68of the Plasmodium falciparum entomological inoculation rates (EIRs) in all the study sites. Alongside; vectors such as Anopheles Gambiae; Anopheles moucheti; Anopheles funestus; Anopheles marshallii and Anopheles hancocki also took a substantial part to these transmission rates in sympatric conditions. Anopheles nili s.s. was the major vector in villages situated near the Sanaga river; with more than 100 infective bites/person/year. Its true Plasmodium falciparum infections rates ranged from 1.4to 6.1. Anopheles carnevalei and Anopheles ovengensis were mainly distributed in the equatorial cross-bordering areas; where they contributed for less than 30of the Plasmodium falciparum EIRs in villages located along the Nten river and Congo river networks. These findings confirm Anopheles nili s.s. as a major malaria vector mosquito; and also provided more data regarding the epidemiological role of Anopheles carnevalei and Anopheles ovengensis througout the central African region