Man-fly contact in the Gambian trypanosomiasis focus of Nola-Bilolo (Central African Republic).

A study using bipyramid tetse fly traps in the Nola-Bilolo sleeping sickness focus (Central African Republic) reveals ecological and behavioural differences between two vectors, Glossina palpalis palpalis and G. fuscipes fuscipes. The latter species inhabits mainly open water sites and surrounding forest, whereas G. p. palpalis occurs mainly in coffe plantations near villages. Consequently, the man-fly contact differs considerably according to the species. The intensity of trypanosomiasis transmission, estimated by the probable distribution of cases, showed significant positive correlation with the density of the flies. Analysis of the fly blood meals in two villages show that, unlike G. g. palpalis, G. f. fuscipes feeds on men more than on pigs. Trypanosoma vivax infection was observed only in G. fuscipes fuscipes. The differences in occupation of the environment between the two vectors must be taken in account in trapping programmes which may modify this distribution.

[An epidemiological survey to discover the probable places of infection with sleeping sickness in the Central African Republic]. / Enquête épidémiologique pour la recherche des lieux de contamination probables dans un foyer centrafricain de maladie du sommeil.

The sleeping sickness focus at Nola-Bilolo in the forest region was the subject of a survey of 142 patients in order to discover their probable places of infection. Seventy of these patients had been detected by active case-finding during a survey conducted in January-February 1991; the other 12 had been discovered by passive case-finding during 1990. The sample of actively detected patients is significantly younger (average 22 +/- 3 years) than the sample detected passively (30 +/- 3 years). This survey highlights the geographical heterogeneity of transmission in the focus. The places where infection is highest are M'Poyo, which with 18% of cases forms the epicentre of the focus and the main reservoir of infecting flies, followed by Bilolo (9%), Mékara (8%), Modigui-Kouna, Ziendi and Domissili (7%). The patients, 95% of whom belong to the M'Bimou tribe, all engage in agriculture; the main activities are coffee-growing for men and the steeping of casava in the river for women. These two activities determine the main places and times of human-tsetse contact. The information obtained by listing the cases detected passively from medical registers is inadequate for locating the places of transmission. The information gathered during active case-finding campaigns by the mobile teams offers a better approach. The method used here, which is recommended, consists of matching the replies given by the patients about their points of contact with the tsetse flies, not just with their places of residence but also with their successive movements and their places of work. The rigour demanded by this kind of approach can only be ensured by a specific survey. This survey also made it possible to demonstrate substantial movements from village to village, which appear to be characteristic of this focus. The results indicate that poorly targeted vector control is likely to be doomed to failure. The study makes it possible to specify priority areas for vector control by trapping and to avoid a "blind" control strategy whereby the whole focus is swamped with traps. The latter strategy is not financially feasible for many countries of tropical Africa.

PIP: In January-February 1991, an epidemiological survey took place in the Nola-Bilolo foyer (a forested zone), a focus of sleeping sickness in the Central African Republic, to learn where patients with sleeping sickness likely became infected. Active case finding during the survey detected 70 cases. Passive case finding in 1990 detected 72 cases. The principal activities which put cases at risk of acquiring African trypanosomiasis were those that took place almost always within a radius of 3 km, suggesting that a peridomestic tse-tse fly population was responsible. These activities included working in coffee plantations for men (31%) and the steeping of cassava in rivers for women (20%). Contact with the tse-tse fly within the village and in the forest contributed somewhat to acquisition of sleeping sickness (12%). Bathing in the rivers was the main activity placing children at risk. The epicenter of the foyer and the principal reservoir of the infective flies was M'poyo which had 18% of sleeping sickness cases. Other significant foci were Bilolo (9%), Mekara (8%), and Modigui-Kouna, Bindjo-Jeolo, Ziendi, and Domissili, all of which had 7% of cases. This survey revealed considerable movements from village to village, which seems to be characteristic of this foyer. It also showed that passive case finding from medical registers is adequate in obtaining information about the location of places of transmission and that mobile health teams are a better approach. The case finding approach allowed health workers to identify people's contact points with the tse-tse fly as well as their place of residence, which better depicts reality. It also allows health planners to identify specific priority areas for vector control by trapping which is financially more feasible for West African countries than is trapping the entire foyer. In conclusion, the case finding survey showed geographic heterogeneity of transmission of typanosomes.

[Absence of epidemiologic interrelations between retroviral infection by HIV and human African trypanosomiasis (HAT)]. / Absence d'inter-relations épidémiologiques entre l'infection rétrovirale à VIH et la trypanosomiase humaine africaine (THA). Analyse de trois enquêtes cas-témoins réalisées en 1989 et 1990 en Afrique centrale.

Authors are reporting results from 3 control-case surveys carried out in sleeping sickness foci in Cameroon, Central African Republic and Congo. HIV seroprevalence rates are comparable among sleeping sickness patients and trypanonegative control persons. These results lead towards the absence of inter-relationships between sleeping sickness and retroviral infection.