Is there a suburban sleeping sickness in Libreville?

BACKGROUND: The transmission of sleeping sickness occurs primarily in rural areas, and exposed populations are those living from rural activities such as agriculture, fishing, animal husbandry or hunting. However, urban and suburban foci are more and more reported in T. b. gambiense areas. In Libreville town, sleeping sickness cases are regularly diagnosed. In order to investigate about the establishment of a transmission cycle of that disease, we have carried out an entomological survey in two quarters in the vicinity of the town. METHODS: Vavoua traps were set out in all suitable biotopes for tsetse flies during four days and examined twice a day. Flies were collected, identified and dissected. RESULTS: Two species of Glossina were caught: G. palpalis palpalis (90.58%) and G. caliginea (9.42%). A total infection rate of 9.37% was observed after dissection of all non-teneral flies captured. CONCLUSION: These results suggest the establishment of a trypanosomiasis transmission cycle in the area. No salivary gland was found infected. Given that infected persons are regularly detected, we can think about the existence of a suburban sleeping sickness focus in Libreville. More analysis is needed concerning the identification of human trypanosomes and the origin of Glossina blood meals that may confirm the existence of that focus.

[Entomological survey in the historical focus of human African trypanosomiasis of Bendje (Gabon)]. / Enquête entomologique dans le foyer historique de trypanosomose humaine africaine de Bendjé (Gabon).

The situation of human African trypanosomiasis (sleeping sickness) is poorly known in Gabon. Most of the historical foci have not been investigated for more than 15 years. Few cases are passively recorded from the historical focus of Bendjé; they involved mainly fishermen but determining their contamination site is difficult because of their mobility due to their activity. The presence of these cases in that focus could favour its reactivation if the vector is still there. In order to assess a potential transmission risk in that area, an entomological survey has been carried out in it. Traps were set up during four days in different habitats used by humans during their daily activities. Three species of tsetse flies (Glossina palpalis palpalis, G. pallicera newsteadi and G. caliginea) were caught and two species of trypanosomes (Trypanosoma vivax and T. brucei s.l.) were identified by PCR. These results suggest the presence of an animal transmission cycle. Human-flies contact was confirmed in all type of habitats but no transmission was quantified in the mangrove.

[Glossina feeding habits and diversity of species of trypanosomes in an active focus of human African trypanosomiasis in Gabon]. / Régime alimentaire des glossines et diversité des espèces de trypanosomes dans un foyer actif de trypanosomose humaine africaine au Gabon.

Feeding host is an important factor upon which depend the Glossina infection rate and the proportion of different species of trypanosome. Glossina feed both upon animals and humans. In order to identify species of trypanosomes present in the Komo-Mondah focus and to verify whether there is any relationship between the prevalence of sleeping sickness and the feeding habits of Glossina, we have carried out an entomological survey in this focus of Gabon. Flies were dissected and organs were analysed by PCR, while the origin of blood meals was determined by ELISA. Three species of trypanosomes were found: Trypanosoma congolense "forest type" (14/104; 13.46%), Trypanosoma vivax (11/104; 10.58%) and Trypanosoma brucei s.l. (65/104; 62.5%) with 13.46% (14/104) of mixed infections of T. brucei s.l. and T. congolense Glossina palpalis palpalis was caught in all biotopes investigated (91.85%) and was infected by all these species of trypanosomes. Glossina caliginea was not infected and Glossina fuscipes fuscipes was infected by T. brucei s.l. Tsetse flies feed more on animals than on humans in almost all villages, but there was no significant difference between the number of blood meals taken upon these two groups of vertebrates (Chi 2 = 7.43; p > 0.05). A negative correlation was found between the zoophylic/anthropophylic index and the prevalence of HAT. This result is insufficient to conclude that this index can be used as an indicator of the degree of prevalence of HAT. In contrary, the trypanosomian risk seems to be an appropriate indicator of the prevalence of HAT in an area. The identification of the reservoir hosts in this focus would be useful for a good understanding of the HAT epidemiology.

[Human African trypanosomiasis: description of two pediatric cases in Yaoundé, Cameroon]. / Trypanosomiase humaine africaine: à propos de deux cas pédiatriques à Yaoundé, Cameroun.

During the first decades of the 20th century, about 45% of deaths in Cameroon were believed to be due to human African trypanosomiasis. Thanks to the screening and treatment campaigns implemented between 1926-1932, a considerable regression of the disease was achieved and, by the 1950s, only a few well-known and delimited foci remained. Today, human African trypanosomiasis is an extremely rare diagnosis, especially in children. The purpose of this report is to describe two cases of neuromeningeal human African trypanosomiasis that were discovered coincidentally in two children, ages 12 and 2 years. The children were from two villages in the center of Cameroon that is not considered as a known endemic focus. These two cases raise difficult questions about the possibility of latent endemic foci of human African trypanosomiasis and of animal-to-human transmission. The outcome was favorable in the first case and fatal in the second.

[The Mandoul human African trypanosomiasis focus in Chad: from evaluation to control]. / Le foyer de trypanosomiase humaine africaine du Mandoul au Tchad : de l'evaluation au contrôle.

The Mandoul focus of human African trypanosomiasis in southern Chad was first described by Gaston Muraz in the 1920s. After 40 years of control measures, case reports became rare and the focus was forgotten. However the number of cases began to increase in 1993 and coordinated control measures were implemented in 2002. The first phase of control consisted of mapping out the focus that was shown to involve 45 villages and camps on both sides of the Mandoul River. The estimated number of inhabitants in the area is 20.000 and the endemic prevalence was 3.78%. Dynamic passive screening and regular active screening undertaken in the framework of the Chadian human African trypanosomiasis control program with the assistance of expert technicians from the subregion reduced the prevalence to 0.77% in 2006. Although this reduction is encouraging, control measures must be maintained and greater involvement of the health care system will be needed to achieve sustainable control of the disease and ultimately to eliminate human African trypanosomiasis as a public health problem.

La trypanosomiase humaine africaine en Afrique centrale en 2007: progres et contraintes

L`Afrique centrale est une region historique de la trypanosomiase humaine africaine. A l`aube du vingt et unieme siecle; la maladie reste epidemique en Angola et en Republique Democratique du Congo et preoccupante dans les autres pays de la region. Malgre la mise en ouvre de nombreux efforts de lutte; le seuil de l`elimination fixe a 1 cas par an pour 10.000 habitants exposes est encore loin d`etre atteint. La transmission se poursuit dans les foyers a faible niveau d`endemicite du fait de l`absence de lutte antivectorielle ciblee au point de contact homme-glossines. Des cas d`echecs therapeutiques sont observes dans certains foyers. De plus en plus; des foyers quiescents se remettent en activite. Une strategie de lutte associant le depistage-traitement des malades et la lutte antivectorielle permettrait d`atteindre plus rapidement l`objectif de l`elimination de la maladie dans les foyers. La presence d`un personnel qualifie et equipe permettrait d`assurer une surveillance sentinelle dans les foyers

[Status of human African trypanosomiasis in the Nola-Salo-Bilolo in the Central African Republic in 2005]. / Situation de la trypanosomiase humaine africaine dans le foyer de Nola-Salo-Bilolo en République Centrafricaine en 2005.

In November-December 2005, the technical staff of the Organisation for Coordination of the Control of Endemic Diseases in Central Africa (OCEAC) and the National Program for Control of Human African Trypanosomiasis (PNLTHA) undertook screening for human African trypanosomiasis in the historical focus of Nola-Salo-Biolo in Central Africa. A total of 31 new cases of typanosomiasis were detected for a prevalence of 0.44%. This study also provided insight into the limits of this old focus and showed that circulation of the parasite is still heavy. The endemia of sleeping sickness has now been contained in Nola-Salo-Bilolo but maintaining control measures is essential to preventing a potentially major recrudescence.

[Organizing an active screening campaign for human African trypanosomiasis due to Trypanosoma brucei gambiense]. / Organisation d'une campagne de dépistage actif de la trypanosomiase humaine africaine à Trypanosoma brucei gambiense.

Organization of an active screening program for human African trypanosomiasis in an outbreak area is subject to strict guidelines that must take into account the size of the population, the specificity and sensitivity of the diagnostic techniques used, and the cost of screening. Numerous parameters can affect the outcome including accessibility of the outbreak area (road conditions, rainy season); awareness of village populations and of local administrative, traditional, and religious personalities; quality of local health-care facilities and personnel; possibility of referring patients to a health care institution able to provide treatment, etc. For these reasons the cost of screening programs can be high in terms of human, physical, and financial resources. Careful planning and preparation is necessary to ensure worthwhile results. The model described in this article allows screening of 300 to 600 persons a day in areas in which the endemic disease prevalence is higher than 1%. A variant for areas with lower endemicity allows screening of up to 1500 persons a day.

Situation de la trypanosomiase humaine africaine dans le foyer de Nola-Salo-Bilolo en Republique Centrafricaine; 2005

En novembre-decembre 2005; les equipes techniques de l'Organisation de Coordination pour la lutte contre les Endemies en Afrique Centrale (OCEAC) et du Programme national de lutte contre la trypanosomiase humaine africaine de la Republique Centrafricaine (PNLTHA) ont procede a un depistage de la trypanosomiase humaine africaine dans le foyer historique de Nola-Salo-Bilolo en Republique Centrafricaine. Cette prospection a permis le diagnostic de 31 nouveaux cas de trypanosomiase; soit une prevalence de 0;44. Elle a permis egalement de mieux cerner les limites actuelles de ce vieux foyer et de constater que la circulation du parasite y est toujours importante. La maladie du sommeil y est actuellement contenue; mais il est essentiel que les efforts de lutte ne s'y relachent pas; faute de quoi l'endemie pourrait a nouveau connaitre une recrudescence preoccupante