La presence des bovins comme hotes alternatifs peut-elle modifier le comportement trophique des vecteurs du paludisme en zone de foret?

Des enquetes entomologiques longitudinales ont ete effectuees de novembre 1998 a novembre 2000 en vue de determiner le comportement trophique des anopheles en presence de bovins comme hotes alternatifs a l`homme dans deux localites de la zone de foret du sud Cameroun; Obala et Nkolbisson. Les collectes des moustiques ont eu lieu a l`interieur des habitations par pulverisation intra domiciliaire et a l`exterieur a l`aide de captures sous moustiquaire piege avec comme appats l`homme et le veau. L`origine du repas de sang et l`infectivite des moustiques ont ete identifiees par la technique ELISA (Enzyme Linked Immunosorbent Asay). Au total; 992 anopheles appartenant a 8 especes ont ete collectees au cours de cette etude. An. funestus etait l`espece la plus abondante a Obala tandis qu`An. nili predominait a Nkolbisson. Le taux d`anthropophilie etait plus eleve chez les moustiques collectes a l`interieur des habitations que chez ceux collectes a l`exterieur sous moustiquaire piege. An. gambiae et An. funestus ont montre une nette preference pour l`homme tandis qu`An. nili a pique indifferemment l`homme et le boeuf. An. gambiae etait de loin le vecteur principal dans les deux sites d`etude avec 24 cas d`infections sur les 42 trouves. Ces resultats montrent que les vecteurs en zone de foret peuvent diversifier la source de leur repas de sang en presence d`hotes alternatifs tels que les bovins. Toutefois; il serait important de comprendre si l`introduction de l`elevage de bovins dans cette region pourrait influencer le cycle de transmission du paludisme

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

Field Evaluation of Three Commercial Repellents Formulations against Afrotropical Vectors Mosquitoes in Camerooun

Three synthetic commercial insert repellents; Buzz-Off TM (30DEET); Cinq-sur-CinqTM (25IR3535 + essential oils) and prebutix TM(25IR3535) were tested in field conditions for their efficacy and persistence against mosquitoes in the forest area of Cameroon. During 48-days; 7; 569 mosquitoes belonging to four genera were collected: Mansonia spp (67.3); Anopheles spp (27.4); Aedes spp(3.8); and Culex spp (1.5). At the end of the 8-hours exposure period; the DEET-based repellent; Buzz Off TM produced the highest protection against Aedes spp; Culex spp and Mansonia spp. For Anophelines; results were more variable : PrebutixTM showed better protection against An. mouchetti; Cinq-sur-CinqTM was more efficacious against An. Funestus and An.ziemani; whereas Buzz-OffTM appeared more effective against An. Gambiae s.s. and An. nili. Efficacy and persistence parameters were estimated only for An. moucheti and Mansonia spp. The effective dosages (ED50 and ED95) as well as the effective half-life obtained with the DEET-based repellent were highly variable among replicates in the case of An. moucheti. For mansonia spp; the estimated EDO value for the DEET -based repellent was = 0.06mg/cm2. For the two IR3535-based repellents; the ED50 values varied from 0.06 to 0.10 mg/cm2; and 0.15 to 0.20 mg/cm2 for An. moucheti and Mansonia spp; respectively. Globally; the ED95 values values of the three repellents were around 1mg/cm2 except that of Cinq-sur-CinqTM which was ? 0.3mg/cm2 in the case of An. moucheti. The estimated effective half-lifes of the three repellents were approximately between 3 and 5h. Our results highlight the heterogeneity in the response of different mosquito species when exposed to the tested insect repellents; showing the relevance of evaluating efficacy and persistence profiles of different formulations in specific environmental contexts