Sensibilité des Populations D’Aedes Aegypti des Zones Héveicoles de Dabou (Sud de la Côte d’Ivoire) aux Organophosphorés, aux Pyréthrinoïdes et au Bacillus Thuringiensis Israelensis

L’expansion de l’hévéaculture entraine une forte modification de l’environnement en Côte d’Ivoire. Aussi, plusieurs épidémies de dengue et de fièvre jaune dues Aedes aegypti ont récemment été observées en Côte d’Ivoire. Le profil de sensibilité aux insecticides d’Aedes aegypti dans ces zones d’agriculture de masse nécessitant une main d’œuvre importante est mal connu. Cette étude a établi le profil de sensibilité d’Aedes aegypti dans les zones de cultures d’hévéa de Dabou afin de mieux planifier les mesures de lutte contre le vecteur majeur des d’arbovirus. Des larves d'Aedes aegypti ont été échantillonnées en janvier 2018 dans des plantations immatures et matures d’hévéa, ainsi que dans les villages environnants aux plantations d’hévéa dans le département de Dabou. Des tests larvicides (Bacillus thuringiensis israelensis et téméphos) et adulticides (chlorpyriphos-méthyl 0.8%, malathion 0,1% et Fenitrithion 0,1%, perméthrine 0,75%, deltaméthrine 0,05%, lambdacyahalothrine 0,05%) en tube sur les générations F1 ont été réalisés conformément aux directives de l'Organisation Mondiale de la Santé (OMS). Les 3743 larves d’Aedes aegypti testées ont été toutes sensibles aux deux larvicides avec des LC50 comprises entre 7.10-3 mg/L et 9.10-3 mg/L pour le Bacillus thuringiensis israelensis et entre 6,5.10-2 mg/L et 1,2.10-1 mg/L pour le téméphos. Les LC95 respectives étaient comprises entre 2,1.10-2 mg/L et 2,4.10-2 mg/L et entre 6,5.10-2 mg/L et 1,2.10-1 mg/L. Aussi, 2400 Aedes aegypti adultes testés ont été tous sensibles aux organophosphorés (chlorpyriphos-méthyl 0.8%, malathion 0,1% et fenitrithion 0,1%) avec des mortalités comprises entre 98% et 100% et aux pyréthrinoïdes (perméthrine 0,75%, deltaméthrine 0,05%, lambdacyahalothrine 0,05%) avec des mortalités de 100%. L’étude a montré que les populations immatures et adultes d’Aedes aegypti des plantations d’hévéa et les villages environnants de la zone d’étude étaient sensibles au Bacillus thuringiensis israelensis, aux organophosphorés et aux pyréthrinoïdes. The expansion of rubber cultivation is leading to a strong modification of the environment in Côte d'Ivoire. As a result, several outbreaks of dengue and yellow fever caused by Aedes aegypti have recently been observed in Côte d'Ivoire. The insecticide susceptibility profile of Aedes aegypti in these labourintensive mass farming areas is poorly known. This study established the susceptibility profile of Aedes aegypti in the rubber growing areas of Dabou in order to better plan control measures against the major arbovirus vector. Aedes aegypti larvae were sampled in January 2018 in immature and mature rubber plantations, as well as in the villages surrounding the rubber plantations in the Dabou department. Larvicidal (Bacillus thuringiensis israelensis and temephos) and adulticidal (chlorpyriphos-methyl 0.8%, malathion 0.1% and Fenitrithion 0.1%, permethrin 0.75%, deltamethrin 0.05%, lambdacyahalothrin 0.05%) tube tests on F1 generations were carried out in accordance with the World Health Organization (WHO) guidelines. All 3743 Aedes aegypti larvae tested were sensitive to both larvicides with LC50 ranging from 7.10-3 mg/L to 9.10-3 mg/L for Bacillus thuringiensis israelensis and from 6.5.10-2 mg/L to 1.2.10-1 mg/L for temephos. The respective LC95 were between 2.1.10-2 mg/L and 2.4.10-2 mg/L and between 6.5.10-2 mg/L and 1.2.10-1 mg/L. Also, 2400 adult Aedes aegypti tested were all sensitive to organophosphates (chlorpyrifos-methyl 0.8%, malathion 0.1% and fenitrithion 0.1%) with mortalities between 98% and 100% and to pyrethroids (permethrin 0.75%, deltamethrin 0.05%, lambdacyahalothrin 0.05%) with mortalities of 100%. The study showed that immature and adult populations of Aedes aegypti in rubber plantations and surrounding villages in the study area were susceptible to Bacillus thuringiensis israelensis, organophosphates and pyrethroids

A High Proportion of Malaria Vector Biting and Resting Indoors despite Extensive LLIN Coverage in Côte d’Ivoire

Malaria is still a leading cause mortality in Côte d’Ivoire despite extensive LLINs coverage. We present the results of an entomological survey conducted in a coastal and in an inland village with the aim to estimate Anopheles gambiae sensu lato (s.l.) female’s abundance indoor/outdoor and Plasmodium falciparum infection rate and analyze the occurrence of blood-feeding in relation to LLINs use. Pyrethrum spray (PSC) and window exit traps (WT) collections were carried out to target endophagic/endophilic and endophagic/exophilic females, respectively. Data on LLINs use in sampled houses were collected. (1) high levels of malaria transmission despite LLINs coverage >70% (~1 An. gambiae s.l. predicted mean/person/night and ~5% Plasmodium falciparum infection rate); (2) 46% of females in the PSC sample were blood-fed, suggesting that they fed on an unprotected host inside the house; (3) 81% of females in WT were unfed, suggesting that they were leaving the house to find an available host. Model estimates that if everyone sleeps under LLINs the probability for a mosquito to bite decreases of 48% and 95% in the coastal and inland village, respectively. The results show a high proportion of mosquito biting and resting indoors despite extensive LLINs. The biological/epidemiological determinants of accounting for these results merit deeper investigations

Is Côte D'Ivoire a new high hybridization zone for the two major malaria vectors, Anopheles coluzzii and An. gambiae (Diptera, Culicidae)?

12openInternationalInternational coauthor/editorAnopheles gambiae and An. coluzzii are very closely related and recently differentiated species representing the main malaria vectors in the Afrotropical region and responsible of up to >3 infective bites/person/night in Côte D'Ivoire, where prevention and control has stagnated in recent years. The aim of the present study was to genetically and ecologically characterize An. gambiae and An. coluzzii populations from two villages of Côte D'Ivoire, lying in the coastal forest belt and 250 km inland in the Guinean savannah mosaic belt, respectively. Results reveal high frequencies of both species in both study sites and high frequencies of hybrids (4–33%) along the whole year of sampling. Consistently with observations for the well-known high hybridization zone at the far-west of the species range, hybrid frequencies were higher in the coastal village and highest when the two species occurred at more balanced frequencies, supporting the “frequency-dependent hybridization” ecological speciation theory. Pilot genotyping revealed signatures of genomic admixture in both chromosome-X and −3. Coupled with previous reports of hybrids in the region, the results point to the coastal region of Côte D'Ivoire as a possible regions of high hybridization. Preliminary characterization of parameters relevant for malaria transmission and control (e.g. possibly higher sporozoite rates and indoor biting preferences in hybrids than in the parental species) highlight the possible relevance of the breakdown of reproductive barriers between An. gambiae and An. coluzzii not only in the field of ecological evolution, but also in malaria epidemiology and controlopenCaputo, Beniamino; Tondossoma, Naminata; Virgillito, Chiara; Pichler, Verena; Serini, Paola; Calzetta, Maria; Manica, Mattia; Coulibaly, Zanakoungo Ibrahim; Dia, Ibrahima; Akré, Maurice; Offianan, Andre; Della Torre, AlessandraCaputo, B.; Tondossoma, N.; Virgillito, C.; Pichler, V.; Serini, P.; Calzetta, M.; Manica, M.; Coulibaly, Z.I.; Dia, I.; Akré, M.; Offianan, A.; Della Torre, A