The epidemiology and control of human African trypanosomiasis.

Human African trypanosomiasis is caused by Trypanosoma brucei gambiense in West and Central Africa, and by Trypanosoma brucei rhodesiense in East and southern Africa. In recent years there has been a dramatic resurgence of Gambian trypanosomiasis in Central Africa, especially in the Democratic Republic of Congo, Angola and Sudan. The disease is quiescent in most of West Africa, as is Rhodesian trypanosomiasis the other side of the continent. The epidemiology of Gambian trypanosomiasis is reviewed in detail. The long duration of infection in human hosts with cycles of intermittent parasitaemia, the vectors' feeding habits and the intensity of human-fly contact are the major determinants of the dynamics of transmission of this parasite. The development of immunity may lead to a reduction in the fraction of the population that is susceptible to infection and the burning out of epidemics after 20 to 30 years. So far, the acquired immune deficiency syndrome pandemic has had no impact on the epidemiology of Gambian trypanosomiasis. A brief review of the epidemiology of Rhodesian trypanosomiasis highlights the differences from Gambian trypanosomiasis that, to some extent, explain its lower propensity to cause epidemics: it is a more aggressive disease that rapidly kills its human host, and its transmission involves mostly domestic and game animals, humans being in most circumstances an accidental host. The various methods and strategies for the surveillance and control of both diseases are reviewed.

[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.

Epidemic of fatal encephalopathy in preschool children in Burkina Faso and consumption of unripe ackee (Blighia sapida) fruit.

BACKGROUND: On March 21, 1998, the Regional Health Authority of Bobo-Dioulasso, Burkina Faso, asked the Centre Muraz to investigate an unexplained outbreak of epidemic fatal encephalopathy (EFE). We aimed to identify the cause of this epidemic. METHODS: We identified cases retrospectively through review of health-service records and interviews of family members, village chiefs, and local healers. Active surveillance was started in administrative divisions within the study area in April, 1998, to identify further EFE cases. We did a case-control study of households to investigate the risk from various environmental and health factors. Blood and urine samples were collected if possible and urine dicarboxylic acid concentrations measured by gas chromatography. FINDINGS: 29 cases of EFE were identified from January to May, 1998. Estimated age-specific attack rates (2-6 years) ranged from 31 to 847 per 100,000 population (p<0.001). The most common symptoms were hypotonia, vomiting, convulsions, and coma. All children died in 2-48 h. The only factor associated with EFE was the presence of ackee trees (Blighia sapida) within 100 m of households (odds ratio 5.1 [95% CI 1.8-14.7] p=0.001). Poisoning with unripe ackee fruits was suggested by urine concentrations of dicarboxylic acids four to 200 times higher in cases (n=2) than in controls (n=3). CONCLUSION: Consumption of unripe ackee fruit probably caused this epidemic and may lead to a substantial number of unexplained deaths in preschool children in west Africa every year. Educational campaigns have the potential to prevent these deaths.

Assessment of central nervous system involvement in gambiense trypanosomiasis: value of the cerebro-spinal white cell count.

OBJECTIVE: To assess, in a clinical setting, the comparative values of conventional criteria used in the diagnosis of central nervous system (CNS) involvement in Trypanosoma brucei gambiense sleeping sickness: white cell count (WCC) in cerebrospinal fluid (CSF) > 5 x 10(6) cells/l; total protein concentration in CSF > 40 mg/100 ml); evidence of trypanosomes in CSF following double centrifugation (DC). METHOD: In vitro culture of CSF was used as the gold standard. RESULTS: The study showed that WCC is, by itself, as sensitive for the diagnosis of the CNS involvement as the usually recommended combination of three conventional criteria. The specificity of WCC is improved while the sensitivity is reduced when the cut-off point is set at a higher value (WCC > 10 X 10(6)/l). CONCLUSION: In poorly equipped laboratories, the diagnosis of CNS involvement in patients with confirmed systemic infection should be based only on the WCC. However, a pilot study is needed to assess the feasibility and reliability of the WCC handled by 'front line' personnel, for different cut-off values.

[Serologic diagnosis of human african trypanosomiasis caused by Trypanosoma brucei gambiense. 1--Production and use of rough antigens in ELISA and latex agglutination tests]. / Diagnostic Sérologique de la trypanosomose humaine africaine à Trypanosoma brucei gambiense. 1--Obtention et utilisation d'antigènes bruts dans les tests ELISA et d'agglutination au latex.

The extraction of rough antigens (Ag) from trypanosomes came across a major problem getting of a high number of parasites. Moreover several technics for the extraction of rough antigens are described. Some of them are sophisticated and time consuming. Aiming the obtention of a large number of Ag for this study, inoculation of trypanosomes into Cricetomys gambianus and affinity chromatography of blood allow to collect of large number of trypanosomes. This new technique leads to the extraction of 50 to 60 mg of rough Ag of trypanosomes isolated from infected Cricetomys. In order to set up a specific and sensitive serological diagnosis of gambian human trypanosomiasis, the different rough Ag were used comparatively by ELISA and Latex Agglutination tests. Confirming previous works, the results indicate a high sensitivity and a doubtful specificity for both techniques.

Human immunodeficiency virus infection and human African trypanosomiasis: a case-control study in Côte d'Ivoire.

To assess the association between human immunodeficiency virus (HIV) infection and human African trypanosomiasis (HAT) in Côte d'Ivoire, West Africa, a cross-sectional case-control study was conducted on 301 HAT patients recruited in the main foci of the country. For each HAT patient, 3 controls, matched for sex, age and residence, were selected. Data relating to socio-demographic factors and potential risk factors for Trypanosoma brucei gambiense and HIV infections were obtained, and serum samples were collected for HIV-1 and HIV-2 tests. A positive test consisted of enzyme immunoassay reactive to HIV-1, HIV-2 or both and confirmed by a synthetic peptide test or Western blot. Data were analyzed using conditional logistic regression with EGRET software. No statistically significant difference was found between the prevalence of HIV infection in HAT patients and controls (4.3% and 3.5% respectively; crude odds ratio (OR) 1.28, 95% confidence interval (CI) 0.65-2.50). In multivariate analysis, allowance for 5 covariates did not change the association between the 2 infections (adjusted OR 1.27, 95% CI 0.64-2.52). Although this study had limited statistical power, no significant association was found between HIV infection and T.b. gambiense infection in rural Côte d'Ivoire. Studies are needed to determine whether HIV infection influences the clinical course of HAT, a question not addressed in the present study.

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.

[Perinatal mortality in Burkina Faso: risk factors in an urban environment of Bobo-Dioulasso]. / La mortinatalité au Burkina Faso: facteurs de risque en milieu urbain de Bobo-Dioulasso.

A total of 96 mothers of stillborn babies (cases) and 402 mothers of live-born babies (controls) were studied between the 1st November 1988 and the 31st July 1989 in an attempt to identify the risk factors for the high number of stillbirths in the Maternity wing of the Hôpital National Sourô SANON in Bobo-Dioulasso, Burkina Faso. From a stratified analysis, eight risk factors emerged as significant predictors of mortality: mother older than 35 years, high parity (five or more), previous history of stillbirth, lack of medical supervision of pregnancy, interval between last consultation and birth longer than 30 days, complications during delivery and birth weight less than 2,500 g. Polygamy was associated with a 51% reduction in the risk of stillbirth. The problem of selection bias which affects the validity of hospital based case-control studies is discussed. Techniques for reducing selection bias in hospital based case-control studies are proposed. Improvements in antenatal care in Bobo-Dioulasso are suggested.