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.

[Role of patient travel in transmission of human African trypanosomiasis in a highly endemic area of the Ivory Coast]. / Représentation spatiale des déplacements des malades dans un foyer de trypanosomose humaine africaine de Côte d'Ivoire.

Human African trypanosomosis (HAT) remains a major public health problem in Subsaharan Africa. The region around the town of Bonon in middle western Côte d'Ivoire is a highly endemic HAT zone. The purpose of this study was to assess the role of travelling of infected patients in transmission of HAT. The study population included a total of 96 patients in whom HAT had been diagnosed actively or passively between 1999 and 2000. Information on each patient's residence and workplaces, i.e. water site, and farm field, was used to calculate the mean distance traveled and mean number of places visited daily by each patient. Findings indicated that both parameters, i.e., distance traveled and number of places visited, were significantly higher for patients living in Bonon than those living in hamlets or homesteads. Based on analysis of patient movements the endemic zone could be divided into three subdivisions with different modes of disease transmission. This study was performed as a preliminary step for a larger investigation designed to allow specific targeting of HAT hot spots based mainly on a geographic information system.

Host age and time of exposure in Trypanosoma brucei gambiense Human African Trypanosomiasis.

Human African Trypanosomiasis is related to behavioural risk factors but complex interactions exist between (i) environmental and behavioural risk factors, (ii) vector and (iii) human host. Our aim was to investigate the interrelationships between previously analysed risk factors and the roles of age and time of exposure according to ethnic group and migration status. However, this descriptive and retrospective study is based on cases only (no controls) and our results must therefore be regarded as hypothesis-generating. Individuals originating from areas where sleeping sickness is absent and who settle in an endemic area seem to develop the disease after a shorter time of exposure than native subjects from endemic areas. Our results emphasise the complexity of vector-transmitted disease epidemiology, involving behavioural and/or environmental risk factors on the one hand, and more individual ones such as ageing, immunity and genetic background on the other hand.

[Spatial distribution and bloodmeal preferences of Glossina palpalis palpalis in the forest focus of Zoukougbeu (Ivory Coast). Epidemiological consequences]. / Répartition spatiale et préférences trophiques de Glossina palpalis palpalis dans le foyer forestier de Zoukougbeu (Cote d'Ivoire). Implications épidémiologiques.

In the sleeping sickness focus of Zoukougbeu (Côte d'Ivoire), in the cropping areas which are favourable for disease transmission, more than a quarter of the flies collected were found to have fed on domestic pigs. The sites where Glossina palpalis palpalis was caught fed on these animals were concordant with the sites where the patients were present. These results might indicate that in Zoukougbeu, but perhaps also in other sleeping sickness foci, the pig could play an active role in disease transmission, allowing the parasite to spread widely via the tsetse.

[Diversity of feeding behavior of Glossina palpalis palpalis in the forest belt of the Ivory Coast: relation to the prevalence of human African trypanosomiasis]. / Diversité du régime alimentaire de Glossina palpalis palpalis en zone forestière de Côte d'Ivoire: relation avec la prévalence de la trypanosomiase humaine africaine.

The feeding habits of Glossina palpalis palpalis, the main vector of human African trypanosomiasis (HAT) were retrospectively analysed using data collected between 1984 and 1994 in five areas in the forest belt in the mid-west of Côte d'Ivoire. The authors compare the feeding habits of the vector in these different foci. This analysis is aimed at determining if there is any relationship between the feeding pattern of tsetse-flies and the prevalence rates of HAT. The feeding pattern was measured using two indices: the conventional index of Shannon and Weaver (Ish) and a new one, the zoophily/anthropophily index (Za). The latter is an estimate of the ratio of the percentage of animal blood meals divided by the percentage of human blood meals. There was no correlation between apparent density and prevalence rate. A high Ish and a high Za were observed in the foci of Vavoua, Zoukougbeu and Sinfra where prevalence rates of HAT were high. Conversely, a low Ish and a low Za were observed in the hypoendemic areas of Daniafla and Gagnoa. Both indices are highly but not significantly correlated with prevalence rates. The Za index seemed to be more strongly correlated to the disease rate as compared to the Ish index. The epidemiological significance of these observations is discussed.

[Age group distribution of Glossina palpalis palpalis females in plantations and shallow water of the forest region of Côte d'Ivoire. Relation to the prevalence of sleeping sickness]. / Répartition des groupes d'âge de Glossina palpalis palpalis femelle dans les plantations et les talwegs en zone forestière de Côte d'Ivoire. Relation avec la prévalence de la maladie du sommeil.

In epidemiologically dangerous biotopes of foci with high prevalence of Human African Trypanosomiasis (HAT), different female age groups (nulliparous, young parous, old parous) were observed in the same proportions. On the contrary, in areas without HAT or in low prevalence foci (< 0.2%), these proportions significantly differed. Female age group distribution in epidemiologically dangerous biotopes could thus be a good indication by which to guide the control of Human African Trypanosomiasis (HAT).

[Detecting sleeping sickness: comparative efficacy of mobile teams and community health workers]. / Dépistage de la maladie du sommeil: efficacité comparée des équipes mobiles et des agents de santé communautaires.

The solution to the problem of human African trypanosomiasis (HAT) first of all requires improved case detection. Effective tests have been available for a number of years but the results of medical surveys are still mediocre, mainly because the populations are poorly mobilized. Those few mobile teams still visiting villages obtain very low presentation rates. In spite of major information campaigns among villagers, in Côte d'Ivoire the Institut Pierre Richet (IPR) and Trypanosomiasis Clinical Research Project (PRCT) teams examined only 42% (9311) of the 22,300 inhabitants of a disease focus during a conventional ten-day survey. In the same focus, community health workers specially trained in sleeping sickness and in the collection of blood samples on filter-paper examined 73% of the population (15,000 individuals) in less than two months. Implementation of a sleeping sickness control strategy is restricted to two types of intervention: either conventional mobile teams which are on hand, competent and rapidly operational but which fail to carry out exhaustive case detection, or integration of case detection into primary health care by entrusting surveillance to the community health workers. This approach requires a minimum of training but ensures that sentinels are permanently present in the village communities. By using the community health workers rather than mobile teams it should be possible to achieve comprehensive monitoring. In operational terms, the cost of surveillance per person is US$ 0.55 for the mobile teams as against US$ 0.10 for the community health workers. Integration of HAT case detection into primary health care is therefore an effective and economical solution, provided the community health workers are properly supervised and above all motivated.

[Epidemiologic risk of infectious disease transmission in regions of the Ivory Coast]. / Le risque epidemiologique dans un foyer de maladie du sommeil en Cote d'Ivoire.

An epidemiological risk indicator based on purely entomological factors can be used to identify regions which are at higher risk of transmission within the endemic forest zones of Ivory Coast, and can serve to point out biotopes to be treated to make antivector campaigns more effective. In the forests of Ivory Coast, so-called socially open environments which are populated by a great number of ethnic groups who are highly mobile and whose amps are spread over a large area, are particularly vulnerable to epidemics of the disease. Transmission always occurs near water: at rivers, water holes, plantations. By contrast, socially closed societies consisting of a single ethnic group settled in a village are at much lower risk. It seems that human behaviour plays as much a role in transmission dynamics as environmental changes which may be more or less favourable to the vector.

[In vivo chemosensitivity tests of Plasmodium falciparum to chloroquine in Senegal: the development of resistance and the assessment of therapeutic efficacy]. / Tests in vivo de chimiosensibilité de Plasmodium falciparum à la chloroquine au Sénégal: évolution de la résistance et estimation de l'efficacité thérapeutique.

The efficacity of oral chloroquine was assessed in 360 out-clinic patients with symptomatic Plasmodium falciparum malaria who were enrolled at five sites, in four administrative regions of Senegal, between 1991 and 1995. They were three rural areas: Mlomp (Casamance), Bandafassilbel (Eastern Senegal), Diohine (Sine-Saloum) and one urban area: Pikine (agglomeration of Dakar). Parasitological failure at Day-7 was observed in 108 patients (30%) and ranged from 14% to 50% according to the study areas. The proportion of RI, RII and RIII responses were 6%, 23% and 1%, respectively. Chloroquine resistance was lowest in Bandafassi, one of the most remote area of Senegal. It was highest in Mlomp where a malaria control programme with mass chemoprophylaxis had been carried out since 1975. The therapeutic failure rate defined by the persistence or reappearance of fever and P. falciparum trophozoites on days 4-7 was 6%. The percentages of therapeutic failure for RI, RII and RIII patients were respectively 14%, 19% and 100%. These results and those of previous studies in Senegal suggest that chloroquine resistance, which first emerged in vivo in 1988 in Dakar, spread between 1990 and 1993 in all regions of this country. The limitations of in vivo tests for the determination of the therapeutic efficacy of chloroquine in malaria endemic regions with increasing chemoresistance are discussed. The low proportion of potentially severe malaria infections in semi-immune persons, the biases in patients selection, and the possibility of delayed complications, considerably limit the potential of these tests for guiding the choice of the best adapted first line treatment.

Measurement of risk in endemic areas of human African trypanosomiasis in Côte d'Ivoire.

An index of epidemiological risk was developed for the foci of human African trypanosomiasis (HAT) in the forest zone of Côte d'Ivoire, based on the following characteristics of Glossina palpalis palpalis populations: daily survival rate, apparent density of teneral males and females, and frequency of human-fly contact. The index agreed well with HAT prevalence. It varied according to ethnic groups and with seasonal changes in agricultural activities and fell rapidly to zero following the start of an anti-vector control campaign. Further studies in different biogeographical zones are desirable in order to substantiate the validity of the index.

Human rabies: clinical features, diagnosis, complications, and management.

A case of rabies was treated with intensive medical support. This led to a prolongation of life to 25 days. The neurologic progression of the disease was monitored clinically and with serial EEG. This prolonged course enabled us to witness and manage a wide variety of unusual complications including the adult respiratory distress syndrome, hypothermia, myocarditis, and diabetes insipidus. This report documents the clinical features, diagnostic problems, complications, and management.