The tsetse fly Glossina palpalis palpalis is composed of several genetically differentiated small populations in the sleeping sickness focus of Bonon, Côte d'Ivoire.

Glossina palpalis is the main vector of human African trypanosomosis (HAT, or sleeping sickness) that dramatically affects human health in sub-Saharan Africa. Because of the implications of genetic structuring of vector populations for the design and efficacy of control campaigns, G. palpalis palpalis in the most active focus of sleeping sickness in Côte d'Ivoire was studied to determine whether this taxon is genetically structured. High and statistically significant levels of within population heterozygote deficiencies were found at each of the five microsatellite loci in two temporally separated samples. Neither null alleles, short allele dominance, nor trap locations could fully explain these deviations from random mating, but a clustering within each of the two samples into different genetic sub-populations (Wahlund effect) was strongly suggested. These different genetic groups, which could display differences in infection rates and trypanosome identity, were composed of small numbers of individuals that were captured together, leading to the observed Wahlund effect. Implications of this population structure on tsetse control are discussed.

[Human African trypanosomiasis: urban transmission in the focus of Bonon (Côte d'Ivoire)]. / Trypanosomose Humaine Africaine: transmission urbaine dans le foyer de Bonon (Côte d'Ivoire).

Human African trypanosomiasis (HAT) is a vector-borne parasitic disease which has often been considered a rural disease. Population increases in African countries have entailed the spread of urban centres, creating favourable conditions for the appearance of new epidemiological conditions. In Cote d'Ivoire, HAT transmission has been described in the surroundings of towns such as Daloa or Sinfra. In the focus of Bonon, located in central-western Cote d'Ivoire, a medical survey detected 96 patients. The sites visited by the patients every day were geo-referenced and the routes between them recorded. In parallel, an entomological survey of the patients' daily locations enabled the collection of data on the vector. In Bonon, we observed urban cases and tsetse (Glossina palpalis) feeding on men. Trypanosoma brucei gambiense was identified in both man and vector; thus all conditions for possible intra-urban trypanosomosis transmission were met. The consequences of this are discussed regarding the problem of diffusion of the disease.

Mixed infections of trypanosomes in tsetse and pigs and their epidemiological significance in a sleeping sickness focus of Côte d'Ivoire.

In a sleeping sickness focus of Côte d'Ivoire, trypanosomes were characterized in humans, pigs and tsetse using various techniques. Out of 74 patients, all the 43 stocks isolated by KIVI (Kit for In Vitro Isolation) appeared to belong to only one zymodeme of Trypanosoma brucei gambiense group 1 (the major zymodeme Z3). The only stock isolated on rodents belonged to a different, new, zymodeme (Z50), of T. b. gambiense group 1. From 18 pigs sampled in the same locations as the patients, PCR showed a high proportion of mixed infections of T. brucei s. l. and T. congolense riverine-forest. Zymodemes of T. brucei s. l. from these pigs were different from those found in humans. From a total of 16 260 captured tsetse (Glossina palpalis palpalis), 1701 were dissected and 28% were found to be infected by trypanosomes. The most prevalent trypanosome was T. congolense riverine-forest type, followed by T. vivax, T. bruceis. l. and T. congolense savannah type, this latter being associated to the forest type of T. congolense in most cases. Mixed infections by 2 or 3 of these trypanosomes were also found. Use of a microsatellite marker allowed us to distinguish T. b. gambiense group 1 in some of the mature infections in tsetse. Differences in infection rates and in trypanosome genotypes according to the host might indicate that the pig may not be an active animal reservoir for humans in this focus.

[Stegomyian indices and epidemiological status of yellow fever in a rural area of the Ivory Coast]. / Indices stégomyiens et situation épidémiologique de la fièvre jaune en zone rurale de Cote d'Ivoire.

The M'bahiakro region, located in the center of Ivory Coast and inhabited by the N'gain, has been the scene of a yellow fever epidemic since 1982. This region reunites all the conditions for cyclic emergence of the flavivirus given the current epidemiologic pattern of yellow fever in Africa. In view of this situation ORSTOM, in collaboration with the Pasteur Institute of Ivory Coast, has created a pilot zone for epidemiologic surveillance of yellow fever in this region. The N'gain region which has a total population of 12,000 living in 20 villages with between 100 and 2000 inhabitants is located in a preforest area with an attenuated transitional climate characterized by a dry season and a rainy season with two peak periods of precipitation (May and October) but a low mean annual rainfall (1172 mm). There are few springs, wells and rivers and maintaining water supplies is difficult. As a result villagers stockpile rainwater in various types of containers. Inspections were carried out from February to July in the 20 villages of the region. Each room of every dwelling was registered and visited. Water reserves were inspected and those containing pre-imaginal stage Culicidae were counted as positive. Nymphs and larva were sometimes collected. Nymphs were raised and larva preserved. Species identification by the laboratory was based on these larva and imagos obtained by raising the nymphs. Correspondence tables established by the World Health Organization between stegomiyan indices (dwelling), container, BRETEAU) and flavivirus in the population were used to exploit the results.(ABSTRACT TRUNCATED AT 250 WORDS)