[Preliminary evaluation of the insecticide susceptibility in Anopheles gambiae and Culex quinquefasciatus from Lobito (Angola), using WHO standard assay]. / Premiers tests OMS d'évaluation de la sensibilité aux insecticides chez Anopheles gambiae et Culex quinquefasciatus à Lobito, Angola.

Field collections of the most common urban mosquito vectors Anopheles gambiae and Culex quinquefasciatus were carried out in June 2003, March 2004 and November 2005 to gather preliminary data on the insecticide susceptibility in mosquitoes from Lobito (Angola) using the WHO standard bioassays. Bioassays were performed on F0 adults emerging from the field larval collections and on unfed adults from landing catches on volunteers. Batches of mosquitoes from three selected locations (Alto Liro, San Jao and Bela Vista) were exposed for 1 hour to several insecticides such as DDT 4%, carbosulfan 0.4%, permethrin 1%, deltamethrin 0.05% and cyfluthrin 0.15%, in order to estimate the immediate knockdown times (kdT50 and kdT95) and the mortality rate after exposure. The results revealed that mosquito susceptibility to insecticides varied depending on the insecticide, the site and the period of collection. The main local malaria vector A. gambiae (both M and S forms) was basically resistant to DDT and susceptible to all pyrethoids, regardless of the period and the site of collections. The overall mortality rate due to DDT was 73% in Alto Liro, 89% in San Jao and varied depending on the period in Bela Vista between 95% in March 2004 and 100% in November 2005. The mortality due to pyrethoids was 100% at all locations, with the kdT50 and KdT95 times ranging between 9 and 16 minutes and between 18 and 29 minutes, respectively. Concerning the C. quinquefasciatus, populations from Yard and Caponte were resistant to all insecticides tested; the mortality rate was 40% with deltamethrin and 70% with permethrin, while no lethal effect was observed with DDT or carbosulfan. In conclusion, despite its probable high resistance to DDT, the main local malaria vector A. gambiae remained fully susceptible to pyrethroids. This could forecast a good biological efficacy of the scheduled vector control interventions in Angola, based on a large-scale distribution of long-lasting, insecticide-treated nets and on the implementation of indoor residual spraying. The local vector control programme must include well-adapted IEC campaigns and full participation of the community for better management of the insecticide resistance in targeted mosquitoes and for better control of malaria vector populations.

Entomological survey and report of a knockdown resistance mutation in the malaria vector Anopheles gambiae from the Republic of Guinea.

The purpose of our entomological survey was to estimate mosquito biodiversity, infectivity rates and insecticide resistance levels in Anopheles species in four study sites in a mining area with high malaria transmission in southeastern Guinea. Anopheles gambiae s.l. (77%) was the most common Anopheles collected followed by An. funestus (20%). The specimens of the An. gambiae complex were predominantly An. gambiae S form (97.6%) with 1.4% of An. gambiae M form found in Kérouané only, and 1% of An. arabiensis which was present in all four study sites. Anopheles gambiae S form and An. funestus were found to be infected with Plasmodium falciparum, with infectivity rates of 4.1% and 4.4% and inoculation rates of 0.60 and 0.19 infected bite/person/night, respectively. In addition, a high level (79%) of the knockdown resistance (kdr) L1014F mutation was reported in the populations of An. gambiae S form. The high malaria transmission that occurs in the prospected area of Guinea requires a long-term vector control programme. However, such a control programme will have to consider the presence of the kdr gene at a surprisingly high level within the dominant vector, which could reduce the expected impact of vector control.

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

First record of Aedes albopictus in Gabon.

Aedes albopictus were collected in the French military camp of Libreville, Estuaire Province, Gabon, from January to March 2007 by human landing catches during an entomological evaluation of malaria transmission. Inspection of potential larval habitats within and outside the camp showed that Ae. albopictus was found only in artificial containers (discarded tires and small water containers). Associated species of mosquito larvae were Ae. aegypti (L.) and Culex quinquefasciatus. At the same time, Ae. albopictus adults and larvae were also collected from discarded tires in Tcheungue near Port Gentil, Ogoue Maritime Province. Ae. albopictus seems to be established in this part of Gabon's littoral. Further studies are necessary to investigate the extension of Ae. albopictus establishment throughout the country.

First report of the oriental mosquito Aedes albopictus on the West African island of Bioko, Equatorial Guinea.

The invasive oriental mosquito Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) was detected on Bioko Island for the first time in November 2001. It was found to be well established breeding in artificial containers at Planta, near Malabo, the capital of Equatorial Guinea. Associated species of mosquito larvae were Aedes aegypti (L.), Ae. africanus (Theobald), Culex near decens Theobald, Cx. duttoni Theobald, Cx. quinquefasciatus Say, Cx. tigripes De Grandpré & De Charmoy, Eretmapodites quinquevittatus Theobald and Mansonia africana (Theobald). This is the third tropical African country to be invaded by Ae. albopictus, which has recently spread to many parts of the Americas and Europe--with vector competence for dengue, yellow fever and other arboviruses. In the Afrotropical environment, it will be interesting to monitor the ecological balance and/or displacement between introduced Ae. albopictus and indigenous Ae. aegpyti (domestic, peri-domestic and sylvatic populations).

Aedes (Stegomyia) albopictus (Skuse), a potential new Dengue vector in southern Cameroon.

Aedes albopictus, a mosquito vector of Dengue virus, has been recorded for the first time in Cameroon. Entomologic surveys in 2000 demonstrated that it is widespread in southern Cameroon, colonizing a wide variety of breeding sites and biting humans in every district surveyed. The presence of this vector increases the risk for emergence of dengue in Cameroon.

[Anopheles species and the transmission of malaria in the forest/savannah transition zone in central Cameroon]. / La faune anophélienne et la transmission du paludisme dans une zone de transition forêt/savane au centre du Cameroun.

A longitudinal study on malaria vectors and transmission was carried out in a forest-savannah transitional area in Cameroon. Indoor all night mosquito collections on human bait were performed during one year in two villages: Nditam and Ngoume. Nditam was located in a secondary forest block surrounded by savannah, while Ngoume was situated in an ancient forest block. The results showed that at Nditam, only one anopheline species was collected, that was Anopheles gambiae s.l.. The average daily biting rate was 2.4 bites per man per night. The sporozoitic index of An. gambiae was 9.4%. The entomological inoculation rate was therefore estimated at 0.225 infective bite per man per night that is to say 82 infective bites per man per year. Malaria transmission was low during the year, but an important increase was observed in September, when the rainfall was at its peak. At Ngoume, no Anopheles mosquito was collected. Therefore, malaria transmission was not observed in that village.

Malaria vectors and transmission in an area deforested for a new international airport in southern Cameroon.

Nsimalen, a village in Southern Cameroon, has been deforested over a surface of 370 hectares for the construction of the new Yaounde international airport (Cameroon). Mosquitoes night catches on human bait were performed over a year in two hamlets of this village, one adjoining the airport and the other situated 3 kilometers off the deforested area. The aim of the survey was to observe malaria vectors and transmission around the airport and to record malaria epidemiological changes resulting from deforestation. The findings showed that the main malaria vector was Anopheles moucheti (95% of the vector population). Anopheles gambiae was also present but in very small quantities. The increased density of the latter near the airport combined with the low parity rates, indicated that deforestation favoured the breeding of this species. Malaria transmission was estimated at 106 and 68 infective bites per man per year in hamlets close to and far away from the airport zone respectively. An. gambiae accounted for 13% of the transmission in the hamlet adjoining the airport and 0% three kilometers off the airport.

Early sporogonic development in local vectors of Plasmodium falciparum in rural Cameroon.

In ongoing studies on experimental transmission of Plasmodium falciparum in the city of Yaounde gametocyte carriers are daily being identified among dispensary patients with malaria-like complaints. This species comprises 93% of all parasitemias and because of the selection criteria most patients have it as a recent infection. 17% of all P. falciparum-positives carry detectable gametocytes with little difference between youngsters and adults. Blood of adult carriers is taken and infection of Anopheles gambiae mosquitoes is attempted by membrane feeding; the establishment of infection is judged by the presence of oocysts.

Evaluation entomologique de l'effet insectifuge du DMP sur trois vecteurs du paludisme au Sud-Cameroun

Le repulsif le plus frequemment disponible a Yaounde; le DMP (dimethylphtalate); a ete evalue contre les piqures de trois vecteurs de paludisme humain; par la methode classique des captures sur hommes. La protection du repulsif n'a ete totale qu'au cours de la premiere heure de traitement. La reduction du taux de piqures d'Anopheles a ete moyenne de 86 pour cent pendant les cinq premieres heures. L'efficacite repulsive de DMP etait tres differente selon les especes anopheliennes: elle a ete particulierement bonne contre Anopheles gambiae. La formulation de DMP testee procure une bonne protection a l'utilisateur pendant plus de deux heures. L'emploi de ce type de repulsif permet de reduire le risque d'impaludation et peut etre conseille comme methode d'appoint pour la prevention des piqures de vecteurs de paludisme

Anthropophilic mosquitoes and malaria transmission at Edea, Cameroon.

An entomological study was carried out during 1990 in the town of Edea in the south of Cameroon to study anthropophilic mosquitoes with special reference to malaria transmission. Man-biting mosquitoes were caught regularly during one night each month in two different districts: Bilalang which is a well planned suburb with 160 houses on a hill-top, provided with a piped water supply; and Pongo which is a densely urbanised suburb in a valley. From 188 man-nights 1030 mosquitoes were collected, comprising 700 Culex quinquefasciatus (68%), 262 Anopheles gambiae (25%) and others species (7%) belonging to the genus Anopheles, Mansonia, Culex and Aedes. The estimated annual biting rates of mosquitoes were 811 bites per man in Bilalang and 2,866 in Pongo. The estimated yearly malaria inoculation rates were 3.8 and 30.2 infective bites per man in Bilalang and Pongo, respectively. In different parts of Pongo district much variation existed; extreme values of the estimated yearly inoculation rate were zero and 86.3 in two houses 200 m apart, located on the top of a hill and in the bottom of a valley, respectively. This study is one of the first conducted on malaria transmission in a moderate sized African town; it shows that the mosquito populations are typically urban and differ greatly from rural ones.

Anopheles moucheti; vecteur principal du paludisme au Sud-Cameroun

Une etude longitudinale a ete realisee pendant un an (avril 1991-mars 1992) dans le village forestier d'Ebogo. Elle avait pour objet de quantifier la transmission du paludisme en utilisant la methode classique des captures des moustiques sur sujets humains. Dans ce village; situe au bord de deux cours d'eau; deux anopheles sont identifies comme responsables de la transmission du paludisme a savoir anopheles moucheti representant 91;8 pour cent du total et anopheles gambiae present uniquement en saison seche

La duree du cycle gonotrophique d'anopheles moucheti varie de trois a quatre jours en fonction de la proximite par rapport aux gites de ponte

La duree du cycle gonotrophique d'anopheles moucheti a ete precisee dans le village forestier d'Ebogo en bordure du fleuve Nyong. D'ordinaire c'est le vecteur secondaire du paludisme mais localement; comme a Ebogo; c'est le vecteur principal qui assure meme une transmission pendant toute l'annee. Au total; le cycle gonotrophique dure 3 jours pour les anopheles moucheti qui prennent leur repas de sang a proximite du gite de ponte. Il dure 4 jours pour les anopheles moucheti qui doivent parcourir de 3;5 a 5 kilometres du gite de ponte

Les moustiques et la transmission du paludisme dans un village traditionnel du bloc forestier camerounais

Les auteurs presentent les resultats de trois enquetes transversales; concernant la faune culicidienne et la transmission du paludisme; effectuees dans un village de foret equatoriale. Trois genres culicidiens ont ete collectes a chaque enquete: Anopheles; Mansonia et Culex. Les anopheles vecteurs de paludisme sont; par ordre d'importance numerique: An.moucheti; An.gambiiae et An.funestus. Les densites anopheliennes ont ete faibles. Ces densites ont ete constantes pour An.funestus mais pas pour les deux autres especes. La transmission du paludisme; quoique seulement observee en avril et en juillet; doit etre permanente. Elle apparait relativement homogene dans tout le village

Anopheles nili as the main vector of human malaria in villages of southern Cameroon.

In villages near Sanaga river, in the forest zone of south Cameroon, Anopheles nili Theobald is the main species of mosquito regularly found biting man inside houses. Its densities are related to the flow level of the river. It is also the main malaria vector in terms of intensity and seasonal duration of transmission. The yearly malaria inoculation rate due to An. nili alone is 104 infective bites/man, varying between 3 infective bites/man in October and 20 in March. Anopheles gambiae Giles is a less important vector in the area but reached its peak in the dry season, when the Sanaga river is at its lowest level. These observations underline the influence of local ecology on malaria transmission and the need for entomological studies in each situation.

[Malaria in Yaounde (Cameroon). Cost and antivectorial control at the family level]. / Le paludisme-maladie dans la ville de Yaoundé (Cameroun). Prise en charge et lutte antivectorielle au niveau familial.

In order to evaluate the financial charges of antivector control and disease at family level for "malaria disease" as perceived by Yaounde inhabitants, the authors carried out a transverse survey on a representative sample of populations derived from sampling surveys at different degrees. Malaria, so defined, represents a dominating endemic for which the yearly financial effort consented by each family amounts to 57,000 FCFA which represents medical care and entailed services as well as the purchase of chemicals for antivector control. The development of more efficient therapeutic behaviours and promotion of greater use of remanent insecticide impregnated bed nets comes in first in setting up training programmes aimed at health personnels and populations who are under their responsibility.

[Urban malaria in Yaounde (Cameroon). 2. Entomologic study in 2 suburban districts]. / Le paludisme urbain a Yaoundé (Cameroun). 2.--Etude entomologique dans deux quartiers peu urbanisés.

A one year entomological survey was carried out to precise the malaria vectors and the malaria transmission in Yaounde, the Cameroon capital (800,000 inhabitants). The study was done in two districts not yet fully urbanized: Nkol Bikok and Nkol Bisson. The latter is located at the periphery and has a pool. Anopheles gambiae was the only human malaria vector. Its agressivity for man depended on the urbanization of the district. Annual man biting rate was 284 in Nkol Bikok and 1,813 in Nkol Bisson. The densities were maximum in May-June and in October-November, corresponding to the end of the short and long rainy seasons. The presence of A. gambiae was permanent except in August-September in Nkol Bikok. In Nkol Bisson the density was higher in the houses near the pool. The yearly inoculation rate (h) was 14 in Nkol Bikok and 30 in Nkol Bisson. The vectorial transmission was observed in may in Nkol Bikok and during four months (June, August, January, February) in Nkol Bisson. These entomological data showed clearly that malaria transmission actually occurred in Yaounde and that the probability to receive at least one infected anopheline bite per year was very near to 1 for inhabitants unprotected against mosquito bites.

Premier essai d'utilisation de moustiquaires impregnees de deltamethrine en milieu urbain a Yaounde (Cameroun)

Il s'agit d'une enquete menee a Yaounde sur l'utilisation des moustiquaires impregnees. 30 foyers ont ete consideres. En effet; 28 des 30 foyers declarent ne plus etre genes par les moustiques; les deux autres le sont avant le coucher.

Les vecteurs et la transmission du paludisme autour du nouvel aeroport international de Yaounde-Nsimalen

Une etude entomologique des vecteurs et de la transmission du paludisme a ete realisee dans le village de Nsimalen pendant un an. les resultats obtenus etablissent que anopheles moucheti est le vecteur principal du paludisme dans ce village et represente plus de 90 pour cent des anopheles captures. Anopheles gambiae est present mais en faible quantite. Il semble cependant que cette espece colonise progressivement la zone deforestee