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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.

Fly catching experiments using the biconical trap and a vector collector (under mosquito net) were performed in different biotopes of the forest zone in Cote d'Ivoire (Daloa region).Of the three species of tsetse usually caught, Glossina palpalis, and to a very minor degree Glossina pallicera, was attracted to man. G. palpalis showed vis-a-vis man a clear difference in attractiveness according to the point of capture. In those habitats where hosts were rare and dispersed (gallery forest, coffee and cocoa plantations) this species frequently attacked man who came into contact with it during the accomplishment of his usual activities, whereas in the village it voluntarily abandoned him in preference for pigs. Whatever the type of biotope, the trap had the same attractiveness. Its use, in contrast to captures on man, enabled a simultaneous study of diverse species that co-existed anthropophilically or zoophilically.Although almost all the tsetse taken in the trap or on vector collector were hungry, it was noticed that the number of females in the trap samples was always higher than that of males.

The spread of human trypanosomiasis towards Central Africa from sources in the Congo at the beginning of the present century, has been linked to population changes and movements between the affected states.The re-appearance of the disease in this part of Africa during the last 10 to 15 years raises again the question of how this disease is propagated. Although present day population movements are not so pronounced as those at the beginning of the century, these are significant population movements along major lines of communication (large rivers particularly). Of equal importance are disease foci which straddle national boundaries. Migrant populations (fishermen from Nigeria and displaced persons or refugees) also play important roles in the dispersal of the disease.Even within certain foci, the mobility of rural populations helps to sustain the endemicity of the disease over large areas.The risks of introducing or increasing trypanosomiasis must not be neglected when populating new areas and when developing agro-industrial complexes which require large labour forces.

A swine fever epizootic decimated the pig herds in villages within the Yamba focus of human trypanosomiasis. Ecological studies of Glossina palpalis palpalis populations were carried out in one of the villages for four years following the disappearance of the pigs, which had been the principal nutritive host of the Glossina in the area. One important behavioural modification occurred, namely the establishment of a small peridomestic tsetse population. The flies deserted the patches of residual forest to settle around the periphery of the village. This probably occurred in numerous other villages where the epizootic had destroyed the herds of pigs. The modified behaviour has increased the man-fly contact, but, on the other hand, facilitates vector control.

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.