[Assessing the Effectiveness of Impregnated Mosquito Nets, 36 Months after Their Distribution in the South of Cameroon]. / Évaluation de l'efficacité des moustiquaires imprégnées 36 mois après leur distribution dans le Sud Cameroun.

Mosquito control in Cameroon relies largely on the proper use of Long-Lasting Insecticidal Nets (LLINs). It is necessary to monitor their effectiveness in order to propose corrective measures to improve the strategy. The aim of this work was to determine the physical integrity and effectiveness of LLINs (Interceptor brand) on Anopheles gambiae s.l. populations in two urban and rural areas of the Ayos health district. The level of LLIN coverage and use was assessed through a population survey. The physical integrity of LLINs was assessed by measuring the holes according to the WHO method. Bio-efficacy testing of ITNs was carried out according to the cone test protocol using 2-5-day-old, non-blood fed Anopheles gambiae s.l. females from the natural field strain and the reference susceptible strain. Household LLIN coverage rates in urban and rural areas were 55.50% and 66.94%, respectively. On the other hand, the rates of use were 78.01% and 75.22% in urban and rural areas respectively. The proportion of nets that had lost their physical integrity after 36 months of use was 47.00% and 59.63% in urban and rural areas respectively. The size of holes ranged from 0.5 to 25 cm. Alphacypermethrin was found to be ineffective against both strains of Anopheles gambiae s.l. tested. Knockdown rates ranged from 8.5% to 73% for the reference susceptible strain and less than 2.5% for the natural field strain. Mortality rates for the natural strain of Anopheles gambiae s.l. ranged from 0% to 2.5% while they were between 29% and 70% for the susceptible strain. The results show a decrease in the effectiveness of LLINs against the mosquitoes tested. This may be due to the lower than expected WHO possession and use rates of LLINs, their relatively high degree of wear and tear, and the resistance of the vectors to alphacypermethrin.

La lutte antimoustique au Cameroun repose en grande partie sur une bonne utilisation des moustiquaires imprégnées d'insecticide à longue durée d'action (MILDA). Il est nécessaire de suivre l'efficacité de ces dernières afin de proposer des mesures correctives pour améliorer la stratégie. Le présent travail a pour but de mesurer l'intégrité physique et l'efficacité des MILDA (marque Interceptor®) sur les populations d'Anopheles gambiae s.l. dans deux zones, urbaine et rurale, du district de santé d'Ayos. Le niveau de couverture et d'utilisation des MILDA a été évalué par une enquête menée auprès des populations 36 mois après la distribution des moustiquaires. L'intégrité physique des MILDA a été évaluée en mesurant les trous suivant la méthode de l'OMS. Les tests de bioefficacité des MILDA ont été effectués suivant le protocole des tests en cône en utilisant des femelles d'Anopheles gambiae s.l. non gorgées âgées de deux à cinq jours, élevées en insectarium et issues de deux souches : la souche locale et une souche sensible de référence. Les taux de couverture des ménages en MILDA en zone urbaine et en zone rurale étaient de 55,50 et 66,94 %, respectivement. Les taux d'utilisation étaient de 78,01 et 75,22 % respectivement. La proportion de moustiquaires trouées était de 47,00 % en zone urbaine et de 59,63 % en zone rurale. La taille des trous variait de 0,5 à 25 cm. L'alphacyperméthrine s'est révélée inefficace contre les deux souches d'Anopheles gambiae s.l. Les taux de knockdown étaient compris entre 8,5 et 73 % pour la souche sensible de référence et inférieurs à 2,5 % pour la souche de terrain. Les taux de mortalité de la souche de terrain d'Anopheles gambiae s.l. variaient de 0 à 2,5 % alors qu'ils étaient compris entre 29 et 70 % pour la souche sensible. Ces résultats révèlent une faible efficacité insecticide des MILDAvisà-vis des anophèles localement. Les taux de possession et d'utilisation des MILDA restent en deçà des attentes de l'OMS. Leur degré d'usure est relativement élevé. Ces observations, dans un contexte où les vecteurs sont résistants à l'alphacyperméthrine, sont alarmantes.

[Ecology and Contribution of Anopheles hancocki Edwards, 1929 in Malaria Transmission in a Village of South Cameroon Forest Block]. / Écologie d'Anopheles hancocki Edwards, 1929 et étude de son implication dans la transmission du paludisme dans un village du bloc forestier sud-camerounais.

Anopheles hancocki is one of the secondary vectors of malaria whose larval ecology in the South Cameroonian forest block is still unknown. This information is however fundamental for developing efficient and sustainable control strategies against this mosquito in localities where it acts as a disease vector. The present study describes the larval ecology of A. hancocki and its contribution in malaria transmission in a riverbank village of the Ayos Health District. Mosquito sampling took place in 2018 on a quarterly rate, combining the dipping method for larval collection with adult mosquito capture on volunteers. For each of the breeding sites, physicochemical characteristics were measured and larvae were collected and reared to adult. Molecular alongside morpho-taxonomic techniques were used for the identification of mosquito species. Physiological age was determined based on the appearance of their ovarian tracheoles and CSP Elisa test was used to assess infectivity. In total, 3,618 adult mosquitoes belonging to seven species were collected in the study area, namely A. hancocki, Anopheles gambiae, Anopheles moucheti, Mansonia africana, Culex pipiens quinquefasciatus, Aedes albopictus and Aedes aegypti. Breeding sites of A. hancocki were similar to those of A. gambiae. However, the total dissolved solids and conductivity values were significantly higher in A. gambiae breeding sites than in those of A. hancocki. A. hancocki was the most aggressive mosquito species and represented 45.6% of the local aggressive culicidofauna. Male species' nocturnal cycle of aggression showed maximum activity between 8 pm and 10 pm. Females of this species were significantly older than those of A. gambiae and contributed to 40% of malaria transmission in the locality with an average annual Entomological Inoculation Rate (EIR) of 2.92 ib/p/year lower than that of A. gambiae (3.65 ib/p/year). Except few differences, ecological requirements for the development of A. hancocki larvae are similar to that of A. gambiae. A. hancocki contributes to the perennial transmission of malaria in the Ayos area; implementation of vector control strategies is therefore needed.

Anopheles hancocki est l'un des vecteurs secondaires du paludisme dont l'écologie larvaire est encore méconnue dans le bloc forestier sud-camerounais. Cette information est pourtant fondamentale pour la mise en place d'une stratégie de contrôle efficace là où ce moustique se fait le vecteur des plasmodiums responsables des paludismes. La présente étude détermine l'écologie larvaire d'A. hancocki et de son degré d'implication dans la transmission du paludisme dans un village fluvial du district de santé d'Ayos. L'échantillonnage des moustiques a eu lieu dans le courant de l'année 2018 au rythme d'une enquête par trimestre en combinant la méthode du dipping de collectes des larves à celle des captures des moustiques adultes sur les volontaires. Pour chaque gîte, les larves ont été prélevées puis élevées en insectarium et les paramètres physicochimiques mesurés in situ. Les moustiques adultes ont été identifiés suivant les critères morphologiques et moléculaires. L'infectivité des vecteurs a été déterminée selon le test Elisa CSP et la détermination de leur âge physiologique fondée sur l'aspect des trachéoles ovariennes. Un total de 3 618 adultes de moustiques appartenant à sept espèces a été obtenu dans la localité d'étude, comprenant A. hancocki, Anopheles gambiae, Anopheles moucheti, Mansonia africana, Culex pipiens quinquefasciatus, Aedes albopictus et Aedes aegypti. Les gîtes d' A. hancocki se sont montrés comparables à ceux d' A. gambiae. Toutefois, les valeurs de total dissolved solid et de conductivité des gîtes d'A. gambiae ont été significativement supérieures à celles des gîtes d'A. hancocki. Ce dernier s'est d'ailleurs montré comme étant l'espèce la plus agressive en représentant 45,6 % de la faune culicidienne capturée dans la zone d'étude. Son cycle nocturne d'agressivité a montré une activité maximale située dans la tranche horaire 20−22 heures. Les femelles de cette espèce étaient significativement plus âgées que celles d'A. gambiae et contribuaient à 40 % de la transmission du paludisme dans la localité avec un taux d'inoculation entomologique moyen annuel de 2,92 pi/H par an, pas loin derrière A. gambiae 3,65 pi/H par an. Les larves d'A. hancocki ont, à quelques différences près, les mêmes exigences écologiques que celles d'A. gambiae. A. hancocki entraîne une transmission pérenne du paludisme dans la région d'étude et impose de ce fait la mise sur pied d'une stratégie durable de contrôle des paludismes.

[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.

[New insight into Anopheles coluzzii Coetzee & Wilkerson, 2013 larval ecology in the Wouri estuary, Littoral-Cameroon]. / Nouvel aperçu sur l'écologie larvaire d'Anopheles coluzzii Coetzee et Wilkerson, 2013 dans l'estuaire du Wouri, Littoral-Cameroun.

Malaria vectors control is essentially based on the use of insecticides against adult mosquitoes. However because of the development of resistance to insecticides, there is now a renewed interest in the management of larval sources. The aim of the present study was to map and characterize the breeding sites of Anopheles coluzzii in the Wouri river estuary in Cameroon. Larval surveys were carried out between December 2013 and August 2014 in rural areas on the island of Manoka and urban area in Youpwe at Douala. Culicidae breeding sites identified were georeferenced and mapped. Their larval productivity was evaluated by the method of "dipping" and their physicochemical parameters measured by spectrophotometry and oximetry. Culicidae collected larvae were reared in the insectarium to the adult stage. Adult mosquitoes were subjected to morphological identification and those belonging to the Anopheles gambiae complex have subsequently been subjected to molecular identification by the PCR-RFLP technique. A total of 240 breeding sites were geo-referenced in the two sites, including 10 types. Abandoned containers and pools were the most frequent breeding sites respectively in Manoka and in Youpwe. After morphological and molecular identification, eleven mosquito species have been identified. Anopheles coluzzii and Culex quinquefasciatus were the most frequent species respectively in Manoka and in Youpwe. Mosquito density was higher in managed gutters and canoes respectively in Manoka and in Youpwe. Culex and Aedes genus were more frequent in the hollow palm and water wells respectively in Manoka and Youpwe. The productivity of breeding sites varied according to the physicochemical parameters. Species richness varied according to the type of breeding site. Anopheles coluzzii was observed for the first time in Cameroon in water storage containers, tires, discarded containers and canoes. This study highlighted diversity in the type of breeding site of An. coluzzii in the Wouri estuary, suggesting the adaptation of this species in its environment. These results could be used to develop an antilarval control strategy in Manoka and in Youpwe.

A study of host preference in tsetse flies using a modified heteroduplex PCR-based method.

A study of host preference in tsetse flies using a modified heteroduplex PCR-based method is described. Domestic and wild animal blood samples were collected to extract the corresponding reference DNAs. In Campo (south Cameroon), tsetse flies (mainly Glossina palpalis palpalis) were trapped and 41 bloodmeals were collected. All reference DNAs and 37 bloodmeal DNAs (90.7%) were successfully amplified and hybridised. Twelve bloodmeals (32.4%) were of human origin, 13 (35.4%) were from Sitatunga (Tragelaphus spekei) (an antelope) while 12 (32.4%) were not identified using our set of reference DNAs. The results confirmed the occurrence of frequent contacts between wild animals and this population of tsetse flies.