Evaluation of LATEX/T.b.gambiense for mass screening of Trypanosoma brucei gambiense sleeping sickness in Central Africa.

We compared the Card Agglutination Test for Trypanosomiasis (CATT), which consists of lyophilized bloodstream form trypomastigotes of Trypanosoma brucei gambiense (T.b.g.) variable antigen type LiTat 1.3, with LATEX/T.b.g., which consists of a lyophilized suspension of latex particles coated with variable surface glycoproteins of T.b.g. variable antigen types LiTat 1.3, 1.5 and 1.6. This study was carried out during two mass screening surveys in 1998 in Campo, a sleeping sickness focus in Cameroon, with a low prevalence (0.3%) and in 1999 in Batangafo which belongs to the Central African focus of Ouham which has a higher prevalence (3%). In Campo, we compared the CATT performed on whole blood with the LATEX/T.b.g. on diluted blood. In Batangafo, both tests were performed on diluted blood. In all circumstances, the specificity of the LATEX/T.b.g. was higher than of CATT. The use of LATEX/T.b.g. on diluted blood instead of CATT results in an important decrease of workload and as a consequence, of costs related to parasitological examinations. In the case of Campo the workload was up to 12 times less than when using CATT 1.3 on whole blood and the cost divided by 3. In Batangafo the workload was decreased by nearly 20% with the LATEX/T.b.g. Finally, it should be noted that in Batangafo, one of the parasitologically confirmed sleeping sickness patients was negative in CATT and positive in LATEX/T.b.g. and that the reading of the test result in LATEX/T.b.g. is easier than in CATT.

[The focus of human trypanosomiasis in Campo (Cameroon). History and endemic situation in 1998]. / Le foyer de trypanosomose humaine de Campo (Cameroun). Historique et situation de l'endémie en 1998.

For the first time in the last thirteen years, the human sleeping sickness focus at Campo, spanning the Cameroon-Equatorial Guinea border areas, has been prospected. The screening was carried out simultaneously on both sides of the border. This focus has been known since the beginning of the century but, contrary to what took place in other well-known foci in bordering countries south of Cameroon, either in the 1920s or the 1980s--there has never been an epidemic outbreak in that area. Such an epidemiological situation makes this focus particularly interesting. Though still active, trypanosomiasis is not very manifest. According to passive screening carried out in recent years, the estimated prevalence ranges between 0.2 and 0.5%. For this screening, 5,255 persons were examined on the Cameroonian side of the focus (90.6% of the census population). The serological screenings were carried out with the CATT 1.3, which is the CATT generally used in screening, and with the latex CATT which associates LiTat 1.3, 1.5 and 1.6. The search for trypanosomes was made by testing the lymph nod juice in presence of adenopathy and in the blood by Quantitative Buffy Coat (QBC), the mini anion exchange centrifugation (mAEC), as well as the in vitro culture using the kit for in vitro isolation of trypanosomes (KIVI) for individuals suspected to be serologically positive. 16 patients were identified in Cameroon but none in Equatorial Guinea. The results show that the Campo focus is active only on the Cameroonian side, centred on the village of Ipono with a limited prevalence (0.3%). The persisting epidemic is most likely to be associated with the presence of pigs carrying the Trypanosoma brucei gambiense which was identified during the study in Ipono. The strain that we isolated was studied by isoenzyme electrophoresis on cellulose acetate. Its zymodeme is the same as that of the human strain isolated in Campo. With the collected epidemiological data, a concerted medical and entomological action could be planned within the limits of the village of Ipono to eradicate the disease. This action may be organised by the existing local health structures. During this study, the latex CATT proved to be more cost-effective than the CATT 1.3 since a similar result was reached requiring eight times less work at a lower cost. This remains to be confirmed in a hyperendemic focus.