Entomological surveys were undertaken between October 1994 and August 1995 and from April to August 1995 in the villages of Kafiné and Pékaha, respectively These villages are located in the centre of Côte-d'Ivoire in a humid savannah area in the prefecture of Niakaramandougou. Rice plots are located to about 500 meters from the first habitations of Kafiné. They also form an enclosure around the village causing a great culicidian nuisance. On the other hand in the village of Pékaha, situated at 8 km from the enclosure, one can find a non-developed low ground area with swamps according to the season which has caused the multiplication of anthropophilic Culicidae. Five genera of mosquito were caught in the two villages: Anopheles, Aedes, Culex, Mansonia and Uranotaenia. The genus Anopheles is by far the most predominant in Kafiné with 84.3% (n=17556). Mansonia, Culex and Aedes respectively constitute 12%, 3% and 0.01% of the total anthropophilic mosquitoes. In the contrary the genus Mansonia was the most predominant in Pékaha with 78.2% (n=6642). Anopheles, Aedes and Culex respectively represent 13.2%, 8.3% and 0.1% of the total number of mosquitoes caught during the surveys. If in the village of Kafiné, the culicidian nuisance is mainly due to anopheles mosquitoes (84.3%) and particularly to An. gambiae s.s. (70.6%), in the village of Pékaha, dwellers suffer more from Mansonia (78.2%) bites than those of Anopheles (13.2%).

A study on malaria transmission based on samples of mosquitoes caught on human subjects was conducted malaria from February to August 1995 in the rice growing area of Kafine, a village located in the Niakara-mandougou district of northern Cote d'Ivoire. The village is surrounded by 117 500 acres of rice fields. Irrigation is sub-permanent in the rice field and harvests number two a year Kafin6 During the 6 months of the study, 12.353 mosquitoes were caught, The average biting rate was 118.8 savannah bites per man per night (b/m/n). Mansonia, Culex and Aedes represented only 17.5% of the total number of mosquitoes caught. Anopheles accounted for 82.5% of the number of anthropophilic mosquitoes, Anopheles gambiae s.s. represented 83.7% of the total Anopheles species. As a whole, the average biting rate (Ivory Coast) recorded for the Anopheles was 98 b/m/n, The average biting rate of An. gambiae was 90.4 b/m/n, The highest rate (121.5 b/m/n) was recorded in April. During the dry and rainy season, the indoor biting cycle per hour of An gambiae s s. was studied from 6 p.m. to 6 a.m. In both seasons, a marked biting activity was noticed between 10 p.m. and 5 a,m. The average annual parity rate reached 40.2% but it ranged from 59.8% (n = 82) in February to 19% (n = 63) in May The mean sporozoitic index of An. gambiae throughout the study period was 1.1% (14 positive salivary glands/1.251 dissected), The index ranged from 0 in April, May and June to 6.2 in = 192) in July, The rate did not vary with rainfall but with the different stages of rice growing. The non-synchronisation of agricultural practises for each growing cycle seemed to be a conclusive factor in the transmission of malaria in this locality. Malaria transmission at Kafine can be characterised by 3 main elements. transmission is intensive with an estimated inoculation rate of 1 ib/m/l; transmission is more related to double phase rice cultivation (regardless of synchronisation on plots) than to rain fall; transmission shows particular variations linked to rice cultivation cycles with an increase during periods of ripeness and harvest, The nuisance caused by higher mosquito density has brought people to comply with use of pyrethroid impregnated bed nets advocated for wide use by the National Malaria Control Program.

In West Africa, Aedes aegypti (Diptera: Culicidae) (Linnaeus, C., 1762. Zweyter Theil, enhalt Beschreibungen veschiedener wichtiger Naturalien. In: Hasselquist, F. (Ed.), Reise nach Palastina in den Jahren von 1749 bis 1752, Rostock, Germany, pp. 267-606) represents the principal vector of yellow fever. This study reports the use of microsatellite markers to characterise various A. aegypti populations from Côte d'Ivoire according to a north-south transect, and to perform a temporal genetic survey of the mosquitoes. Three microsatellite loci were used to analyse individuals from four different places: Kabolo, Bouaké, and two different districts of Abidjan. We found that the four populations are genetically distinct except the two Abidjan populations. In the Bouaké population, the coexistence of two cryptic species, not morphologically distinguishable, seems to account for the extensive heterozygote deficiency observed. Comparison of mosquitoes from Bouaké 1 year apart indicated that a dramatic change occurred in the structuring of this population over time. Taken together these results indicate that microsatellite markers could be useful for identifying various populations of A. aegypti on a microgeographic scale and to assess for temporal variation within mosquito populations.

A study on malaria transmission based on samples of mosquitoes caught on human subjects was conducted from February to August 1995 in the rice growing area of Kafine, a village located in the Niakaramandougou district of northern Côte d'Ivoire. The village is surrounded by 117,500 acres of rice fields. Irrigation is sub-permanent in the rice field and harvests number two a year. During the 6 months of the study, 12.353 mosquitoes were caught. The average biting rate was 118.8 bites per man per night (b/m/n). Mansonia, Culex and Aedes represented only 17.5% of the total number of mosquitoes caught. Anopheles accounted for 82.5% of the number of anthropophilic mosquitoes. Anopheles gambiae s.s. represented 83.7% of the total Anopheles species. As a whole, the average biting rate recorded for the Anopheles was 98 b/m/n. The average biting rate of An. gambiae was 90.4 b/m/n. The highest rate (121.5 b/m/n) was recorded in April. During the dry and rainy season, the indoor biting cycle per hour of An. gambiae s.s. was studied from 6 p.m. to 6 a.m. In both seasons, a marked biting activity was noticed between 10 p.m. and 5 a.m. The average annual parity rate reached 40.2% but it ranged from 59.8% (n = 82) in February to 19% (n = 63) in May. The mean sporozoitic index of An. gambiae throughout the study period was 1.1% (14 positive salivary glands/1.251 dissected). The index ranged from 0 in April, May and June to 6.2 (n = 192) in July. The rate did not vary with rainfall but with the different stages of rice growing. The non-synchronisation of agricultural practises for each growing cycle seemed to be a conclusive factor in the transmission of malaria in this locality. Malaria transmission at Kafine can be characterised by 3 main elements: transmission is intensive with an estimated inoculation rate of 1 ib/m/n; transmission is more related to double phase rice cultivation (regardless of synchronisation on plots) than to rainfall; transmission shows particular variations linked to rice cultivation cycles with an increase during periods of ripeness and harvest. The nuisance caused by higher mosquito density has brought people to comply with use of pyrethroid impregnated bed nets advocated for wide use by the National Malaria Control Program.

Cote d'Ivoire is an endemic country for yellow fever but no case was officially notified in recent years. In July 1999, however one fatal case was reported, A German citizen was infected in the national park of Comoe, in the north eastern area of the country, In order to evaluate the extent of amaril virus circulation and the risk for local people, a virological entomological and epidemiological investigation logical investigation was carried out by the ministry of health, the OCCGE, the Cote d'Ivoire Pasteur Institute (IPCI) and the World Health Organisation in the area where the fatal case had been staying. 18 suspected and 24 confirmed mosquito catchers were identified by interview and a blood specimen was collected from each of them. In addition, 159 batches of mosquitoes from which 94 batches of potential vectors were collected; among the suspected cases, 22% were immunised against yellow fever Serological and virological analyses were made at IPCI and the Paris Pasteur Institute by ELISA technique and isolation on cells cultures and newborn mice. All the suspicious sera and 87,5% of the catchers were positive for IgG anti-amaril virus. One catchers serum was positive for IgM anti-amaril virus. 11 suspected sera were positive for IgG anti-dengue virus with 1 positive for IgM. 1 strain of amaril virus and 3 strains of Zika virus were isolated from mosquitoes at IPCI and confirmed by CRORA in Dakar These results indicated that there is a yellow fever and dengue virus are prevalent among the human and vector populations in the study area. Preventive measures must be adopted to protect human beings at risk for amaril infection.

Côte d'Ivoire is an endemic country for yellow fever, but no case was officially notified in recent years. In July 1999, however, one fatal case was reported. A German citizen was infected in the national park of Comoe, in the north eastern area of the country. In order to evaluate the extent of amaril virus circulation and the risk for local people, a virological, entomological and epidemiological investigation was carried out by the ministry of health, the OCCGE, the Côte d'Ivoire Pasteur Institute (IPCI) and the World Health Organisation in the area where the fatal case had been staying. 18 suspected and 24 confirmed mosquito catchers were identified by interview and a blood specimen was collected from each of them. In addition, 159 batches of mosquitoes from which 94 batches of potential vectors were collected; among the suspected cases, 22% were immunised against yellow fever. Serological and virological analyses were made at IPCI and the Paris Pasteur Institute by ELISA technique and isolation on cells cultures and newborn mice. All the suspicious sera and 87.5% of the catchers were positive for IgG anti-amaril virus. One catcher's serum was positive for IgM anti-amaril virus. 11 suspected sera were positive for IgG anti-dengue virus with 1 positive for IgM. 1 strain of amaril virus and 3 strains of Zika virus were isolated from mosquitoes at IPCI and confirmed by CRORA in Dakar. These results indicated that there is a yellow fever and dengue virus are prevalent among the human and vector populations in the study area. Preventive measures must be adopted to protect human beings at risk for amaril infection.

The biting indoor cycle of Anopheles gambiae s.s. was studied in a rural zone near Bouaké from 6 pm to 6 am. The cycle was characterized by a peak between midnight and 1 am (n = 19,181). The parturity rate of biting females regularly increased from 6 pm until 3 am, then remained at a high level up to 6 am (n = 14,239). Infected bites were observed from 7 pm to 6 am with a maximum between 0 and 3 am, and 96.7% of them were obtained between 11 pm and 4 am (n = 219). It appears that malaria transmission occurs essentially at the moment when villagers are in bed. The correct use of impregnated bed nets may thus greatly reduce malaria transmission.

The biting indoor cycle of Anopheles gambiae s.s. was studied in a rural zone near Bouake from 6pm to 6am. The cycle was characterized by a peak between midnight and 1am (n = 19 181). The parturity rate of biting females regularly increased from 6pm until 3am, then remained at a high level up to 6am (n = 14 239). Infected bites were observed from 7pm to 6am with a maximum between 0 and 3am, and 96.7% of them were obtained between 11pm and 4am (n = 219). It appears that malaria transmission occurs essentially at the moment when villagers are in bed. The correct use of impregnated bed nets may thus greatly reduce malaria transmission.

Dans la zone rurale proche de Bouake, le cycle d'agressivite intradomiciliaire d'Anopheles gambiae s.s. a ete etudie de 18 heures a 6 heures. Il a ete caracterise par un pic entre 0 et 1 heure du matin (n = 19 181). Le taux de parturite des femelles agressives a augmente de facon continue de 18 heures a 3 heures puis est reste eleve jusqu'a 6 heures (n = 14239), Des piqures d'An. gambiae infectees ont ete observees de 19 a 6 heures avec un maximum entre 0 et 3 heures ; 96, 7 % des infections ont ete rencontrees entre 23 heures et 4 heures du matin (n = 219). II apparait donc que la transmission du paludisme survient essentiellement a une periode de la nuit ou les villageois sont couches. Dans un tel contexte, l'utilisation convenable de moustiquaires impregnees d'insecticide pourrait grandement limiter la transmission du paludisme.

This study evaluates the impact of rice fields in the city of Bouake on anopheline fauna and malaria transmission. The Anopheles species represents between 11.4 to 39.2% of mosquitoes in the districts with rice fields and 5.2 to 47.8% in lowland districts with market-gardening. An. gambiae constitutes more than 98% of anopheline population in the city. In the lowland districts with market-gardening, biting rates of An. gambiae varied from 3650 to 6935 bites per man per year. Seasonal variations were correlated with rainfall. The mean annual parturity rate was 72% and the mean sporozoitic index 2%. Malaria transmission started at the begining of the rainy season and attained its height during the second half of this season. Depending on the district, inhabitants were infected with 78 to 134 bites per year. The mean biting rate of An. gambiae in the districts with rice fields varied from 4745 to 22630 bites per man per year. Seasonal variations were not correlated with rainfall, but with the growth of rice and the two annual cycles of rice cultivation. The parturity rates of the population of An. gambiae were low (46.2% to 57.2%), especially after rice transplantation. The mean infection rates were between 0.7 and 1.0%. The transmission period covered 7 to 11 months depending on the district with two annual peaks observed at the end of rice cultivation. inhabitants were infected with 44 to 155 bites per year. Rice fields in Bouake do not seem notably to have modified malaria transmission in the city.

A study of the bloodfeeding behaviour of An. gambiae and An. funestus was carried out in the city of Bouake and surrounding villages. The results showed that 99.4% of An. gambiae in the city feed on human hosts. In villages 98.8% of An. gambiae and all An. funestus feed on human hosts. in this area, the anthropophily of major malaria vectors is almost exclusive.

The purpose of this report is to describe six surveys carried out from March 1993 to March 1994 to assess seasonal variations in parasite indexes and malaria morbidity rates in children between the ages of 0 and 14 years living in the village of Alloukoukro in the wet Savannah region of Cote d'Ivoire. Results demonstrated the presence of both Plasmodium falciparum and Plasmodium malariae. No case of infection only by Plasmodium malriae was observed. Parasite indexes were greater than 50% in all newborns and preschoolers. Wide seasonal variations were observed with the highest indexes (91.9%) occurring at the end of the rainy season. The lowest indexes were always observed in children between the ages of 10 and 14 years. There was not a significant proportional relationship between parasite index and daily mosquitoes inoculation rates. However highest parasite indexes were always measured after periods of intense transmission. Overall findings showed that gametocyte index increased during the rainy season and peaked at the beginning of the dry season in December. Strong recrudescence of malarious disease during the rainy season corresponded to an increase in the mean parasite density. The seasonal rises in malaria incidence occurred a few weeks after the first rains of the year with the greatest incidence occurring in May. Curves for maximum mean parasitemia rate and peak parasite incidence crossed at the end of the rainy season in October. The results of this study indicate that malaria is the most common parasitic disease year round in children living in the wet Savannah region of Cote d'Ivoire and that it is one of the main causes of morbidity.

This study evaluates the impact of rice fields in the city of Bouaké on anopheline fauna and malaria transmission. The Anopheles species represents between 11.4 to 39.2% of mosquitoes in the districts with rice fields and 5.2 to 47.8% in lowland districts with market-gardening. An. gambiae constitutes more than 98% of anopheline population in the city. In the lowland districts with market-gardening, biting rates of An. gambiae varied from 3650 to 6935 bites per man per year. Seasonal variations were correlated with rainfall. The mean annual parturity rate was 72% and the mean sporozoitic index 2%. Malaria transmission started at the beginning of the rainy season and attained its height during the second half of this season. Depending on the district, inhabitants were infected with 78 to 134 bites per year. The mean biting rate of An. gambiae in the districts with rice fields varied from 4745 to 22,630 bites per man per year. Seasonal variations were not correlated with rainfall, but with the growth of rice and the two annual cycles of rice cultivation. The parturity rates of the population of An. gambiae were low (46.2% to 57.2%), especially after rice transplantation. The mean infection rates were between 0.7 and 1.0%. The transmission period covered 7 to 11 months depending on the district with two annual peaks observed at the end of rice cultivation. Inhabitants were infected with 44 to 155 bites per year. Rice fields in Bouaké do not seem notably to have modified malaria transmission in the city.

Afin de suivre les variations saisonnieres des indices parasitologiques et de la morbidite palustre chez les enfants âges de 0 a 14 ans, six enquetes paludometriques consecutives ont ete menees de mars 1993 a mars 1994 dans le village d'Alloukoukro situe en zone de savane humide de Cote d'Ivoire. Elles ont montre que Plasmodium falciparum et Plasmodium malariae etaient les especes plasmodiales qui circulaient. Aucun cas d'infection monospecifique a Plasmodium malariae n'a ete enregistre. Les indices plasmodiques etaient toujours superieurs a 50 % chez les nourrissons et les enfants en âge prescolaire. Ils presentaient des, variations saisonnieres importantes avec un maximum de 91,9 % en fin de saison des pluies. Les indices les plus bas ont ete enregistres en toute saison chez les enfants âges de 10 a 14 ans. Il n'existaient pas de relation de proportionnalite significative entre les indices plasmodiques observes et les taux quotidiens d'inoculation entomologique. Cependant, les indices plasmodiques les plus eleves etaient precedes par des periodes de transmission intense. Les indices gametocytiques augmentaient, toutes classes d'âge confondues, durant la saison des pluies pour culminer en decembre au debut de la saison seche. La recrudescence du paludisme-maladie etait importante durant la saison pluvieuse avec une elevation des densites parasitaires moyennes. Les poussees saisonnieres de fortes prevalences survenaient quelques semaines apres les premieres pluies de l'annee, avec une incidence tres marquee au mois de mai. Les taux maximaux des parasitemies moyennes et le pic de prevalence parasitaire se rejoignaient au mois d'octobre a la fin de la saison des pluies. Au regard de ces resultats, il apparait que le paludisme constitue en toute saison la plus importante parasitose chez les enfants vivant en zone de savane humide ivoirienne et qu'elle y represente l'une des principales causes de morbidite.

A study of the bloodfeeding behaviour of An. gambiae and An. funestus was carried out in the city of Bouaké and surrounding villages. The results showed that 99.4% of An. gambiae in the city feed on human hosts. In villages, 98.8% of An. gambiae and all An. funestus feed on human hosts. In this area, the anthropophily of major malaria vectors is almost exclusive.

The displacement of adult black flies along a line of breeding sites has been studied in savannah area and in pre-forest zone. This paper presents the results of studies carried out in forest zone of Côte d'Ivoire. Interception traps made with sticky window traps were vertically displayed cross the river. The results showed that the displacement of adult S. damnosum s.l. along a line of breeding sites is correlated with the river flow. In a period of low discharge, adult black flies present a marked tendency to fly up stream. But in period of heavy discharge, they do not show any tendency; they may fly ever up stream or down stream. They fly essentially at the water level during the period of low flow and at a height between 0.5 to 1.5 m during heavy flow of the river.