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Une étude sur un cycle annuel du parasitisme de Glossina palpalis palpalis par Hexamermis glossinae a été effectuée dans les secteurs d'Abengourou, d'Aboisso et de Daloa (zones forestières de Côte d'Ivoire). Les dissections de 2 168 glossines à Abengourou et 9732 à Aboisso n'ont pas permis de mettre le parasite en évidence. À Daloa, en revanche, le pourcentage d'infection est de 1,75 % sur un total de 7341 mouches disséquées. Tous les parasites sont localisés dans la cavité abdominale sans léser les organes. Les mâles sont plus infectés que les femelles (2,68 % contre 1,26 %), et parmi celles-ci les nullipares sont plus infectées que les jeunes pares et vieilles pares (2,30 % contre 1,19 % et 0,52 % respectivement). Le parasite est le plus abondant chez les glossines en début de saison des pluies (5, 17 %) et plus rare en saison sèche (0,23 %). Le faible niveau de parasitisme observé ici semble indiquer que celui-ci a naturellement peu d'impact sur la dynamique du principal vecteur de la maladie du sommeil en Côte d'Ivoire.

L'étude des anomalies de la reproduction a été faite par dissection de 11012 mouches tsé-tsé capturées pendant un an dans les différents habitats forestiers de G. palpalis palpalis à Daloa en Côte d ’Ivoire. La proportion de femelles avec des anomalies était très faible, de l'ordre de 0,79 %. Sur 87 glossines présentant des anomalies, 93,10 % étaient dues à des avortements, 5,77 % à des blocages d'ovulation et 1,13 % à des pupaisons in utero. Les anomalies ont été enregistrées dans toutes les classes d'âge étudiées : 0,78 % chez les jeunes pares (sur un échantillon de 6398 glossines) et 0,80 % chez les vieilles pares (4614 glossines). Nos résultats indiquent donc que les anomalies surviennent à n'importe quel stade du cycle de gestation de la femelle. Les auteurs proposent donc d'augmenter les anomalies de la reproduction à l'aide de substances chimiques, afin d'améliorer l'efficacité de la lutte à l'aide de supports attractifs toxiques en zone forestière.

Des expériences de captures de G. p. palpalis ont été faites en utilisant le porc et l'homme dans le village de Noumousséria II (zone forestière de Daloa) en Côte d'Ivoire. L'analyse des résultats montre que : 1) les récoltes faites avec le porc sont 2,4 fois plus abondantes que celles réalisées avec l'homme; 2) le pourcentage de femelles capturées sur le porc est plus élevé (76,16 %) que celui des mâles alors que chez l'homme aucune différence n'apparaît entre les sexes; 3) l'amplitude des variations saisonnières est plus marquée chez le porc que chez l'homme. Du point de vue qualitatif, une similitude a été observée entre les échantillons de glossines prises avec le porc et ceux du piège biconique. Malgré le faible nombre de glossines marquées recapturées, il semblerait que les mouches tsé-tsé reviennent plus au porc (2 mouches tsé-tsé) qu'à l'homme (aucune)..

Observations on the parasitism of Glossina palpalis palpalis by Hexamermis glossinae were carried out over a period of one year by catching flies at Abengourou, Aboisso and Daloa (forested area of Ivory Coast). No parasite is observed out of 2,168 Glossina palpalis palpalis caught in Abengourou and 9,732 in Aboisso. At Daloa, dissections of 7,341 Glossina reveal 1.75% parasited flies. All the worms were located in the abdominal cavity, loosely intertwined with the internal organ. Males were more infested than females (2.68% versus 1.26%). The parasites were more abundant among the nulliparous (2.30%) than the young parous (1.19%) and than the old parous (0.52%). The majority of infected flies were caught at the beginning of the rainy season (5.17%) and few in the dry season (0.23%). The low parasitic infection rate observed here indicates a minimal effect on the population dynamics of the vector of sleeping sickness in Ivory Coast.

Study of reproductive disorders were carried out through the dissection of 11,012 tsetse flies caught over a period of one year in forested different habitats of Glossina palpalis palpalis of Daloa in Ivory Coast. The proportion of females with reproductive disorders was very low and estimated at 0.79%. Out of 87 tsetse files with reproductive disorders, 93.10% were abortions, 5.77% were ovular blockage and 1.13% was uterine pupaison. Reproductive disorders were recorded from all age groups: 0.78% in young parous (out of 6,398 tsetse flies examined) and 0.80% in old parous (out of 4,614 tsetse flies dissequed). Our results show that reproductive disorders occur at any stage of the female pregnancy cycle. Amplifying these reproductive disorders using chemical compounds is proposed as a way of improving the efficacy of insecticide-impregnated targets (pour-on, traps and screens) of tsetse control in rain-forest areas.

Historically the region of Abengourou is a well-known of sleeping sickness in the forest area of Cote d'Ivoire. However data from epidemiologic studies carried out since 1980 show that this area is currently disease-free. This finding warrants study of glossina vectors to clarify the epidemiology of the disease in this area. Entomologic surveys were carried out over a period of one year. Traps were used to capture glossina in ten natural habitats: villages with or without pigs, coffee, cocoa and rice plantations, grazing lands, camping areas, uncultivated farmlands, trails, forest borderlands and wilderness. Findings documented almost total disappearance of zoophilic glossina (Glossina nigrofusca and Glossina pallicera) which accounted for less than 0.5% of glossina captured only during the rainy season. The apparent trap density (ATD) of Glossina palpalis, the main vector of disease, was low overall. However ATD values tended to be higher in villages with pigs (ATD : 2.07 glossina/trap/day) and forest borderlands (ATD : 2.63 glossina/trap/day) than in other habitants where values were always lower than 1 glossina/trap/day. This almost complete disappearance of Glossina palpalis can be attributed mainly to deforestation in most of the areas studied. This accounts for reduced contact with man. The absence of contact between man and anthropophilic glossins could explain that unlike Daloa and Vavoua sleeping sickness has disappeared from the region of Abengourou.

2,153 Glossina palpalis palpalis caught in biconical traps from different biotopes in relation with human activities in the forest areas of Côte d'Ivoire were used to calculate the trypanosome infection rates. The results showed that there was no preferential biotope for Glossina infected by trypanosomes. The most widespread species of trypanosomes infecting Glossina p. palpalis is T. congolense (10.13%) followed by T. vivax (8.22%) and seldomly by T. brucei (0.70%). Female Glossina are infected with trypanosomes (21.27%) more than the male ones (13.56%). Regarding female Glossina, the physiological age concerned by the first infection of T. vivax, T. congolense and T. brucei reached respectively 5, 15 and 35 days. These different infection rates vary in relation to seasons.

Tsetse control trials were carried out in forest zone of Côte d'Ivoire with biconical traps. Some of the traps were impregnated with deltamethrin (1, 2 g per trap) and others were not. Results show a rapid and effective action of the treated supports. In nine days, the tsetse population had been reduced by 85% on the treated supports and by 60% on the non treated supports. After one month, a rapid decrease of the efficacy of the treated traps was observed. The fall in the effectiveness (more masked in the treated traps) was certainly due to heavy rains (875 mm) which caused an important increase in growth of vegetation.

The biometric analysis of the male genitalia of Glossina palpalis palpalis and Glossina palpalis gambiensis about samples caught along four bits of road in Côte d'Ivoire permitted to determine the geographic limit between both subspecies. G. p. palpalis is everywhere in the Guinean area whereas G. p. gambiensis is found in the Sudanese one. In the wet savanna, both subspecies live together and mate to give out a reduced number of hybrids.