Controle de qualite lors de l'evaluation echographique de la morbidite due a Schistosoma haematobium au Niger

Lors d'un programme de lutte contre la bilharziose urinaire au Niger; il a ete procede a un controle de qualite au cours d'enquetes d'eva l u ation ech ographique de la morbidite due a Schistosoma haematobium. L'objectif etait d'evaluer la vari abilite et la r ro d u c t ibilite des donnees epidemiologiques fournies par deux observat e u rs independants specialement fo rmes. Trois types d'enquetes ont ete menes : etude de la variabilite inter- observateur sur donnees appariees; etude de la vari abilite inter- observateur au niveau communautaire sur les memes sujets ou des sujets differents; y compris apres traitement parpra z i q u a n t e l ; etude de la va ri ab ilite intra- observateur. Au total; 1416 habitants de 10 vill ages hyperendemiques; dont 70 p. 100 d'enfants scolarises; ont subi 1750 examens ech ographiques selon le protocole OMS du Caire legerement modifie. La vari abilite inter- o b s e rvateur au niveau individuel etait elevee pour certaines anomalies vesicales elementaires. Elle etait d'environ 20 p. 100 pour les deux indicat e u rs synthetiques que sont la presence d'au moins une anomalie urinaire et la dilat ation du tractus uri n a i re superi e u r. Au niveau communautaire; la vari abilite inter- observateur etait moderee et les deux observat e u rs donnaient globalement le meme diagnostic sur le niveau de morbidite lie a S chistosoma haemat o b i u m. Les vari ations de morbidite liees au niveau d'endemicite etait percues para llelement. Les memes observations au niveau individuel ou communautaire ont ete faites quant a la variabilite intra - o b s e rvateur. Au cours d'un programme de controle; les ultrasons sont senses fournir des indicateurs epidemiologiques de morbidite afin d'orienter les activites de lutte (selection des communautes a risque; periodicite des traitements). Dans cette optique; les variations d'eva l u ation de la morbidite liees a l'ech ograp h i s t e observees au Niger sont accep t ables au niveau communautaire

The WHO collaborating centre for research and control of schistosomiasis at Niamey, Niger

The Centre de Recherche sur les Meningites et les Schistosomes (CERMES) is a research institute depending on the Organisation de Coordination et de Cooperation pour la lutte contre les Grandes Endemies - a West African Organisation for Public Health - devoted to the studies on schistosomiasis and meningitis. The staff includes 32 persons with 11 scientists and one financial officer. The activities of the CERMES involving schistosomiasis concern three research units: (a) ecology of human and animal schistosomiasis transmission: the CERMES defined the different patterns of schistosomiasis transmission in Niger (involving African dry savana); in this field, we have shown, (i) the existence of important variability in conditions of transmission of S. haematobium and, (ii) natural hybridization between parasite species of the ruminants (s. bovis and S. curassoni) and genetic interaction between human and animal parasites; (b) definition of morbidity indicators usable for rapid assessment methods, for appraisal of the severity of the disease and for the evaluation of the efficiency of control methods; we have established the correlation between ultrasonographic data and some cheap and sample field indicators; (c) immune response and protective immunity by recombinant glutathion S-transferase (Sm28, Sb28 and Sh28) in homologous and heterologous animal including goats, sheep and non human primates (Erythocebus patas). In Niger, we participate in all control programs against schistosomiasis to define control strategies, to supervise operations and to participate in their evaluation with external experts. International collaborations constitute a frame including four laboratories in Africa and six labotatories in developed countries (Europe and USA).

GP38, P28-I and P28-II: candidates for a vaccine against Schistosomiasis

Three antigens protective against Schistosoma mansoni have been extensively characterized. The schistosomulum surface antigen GP38 possesses an immunodominant carbohydrate epitope of which the structure has been defined. Protection can be achieved via the transfer of monoclonal antibodies recognizing the epitope or by immunization with anti-idiotype monoclonal antibodies. The glycan epitope is shared with the intermediate host, Biomphalaria glabrata as well as being present on other molluscs, including the Keyhole Limpet. A group of molecules at 28 kDa were initially characterized in adult worms and shown to protect rats and mice against a challenge infection. One of these molecules, P28-I, was cloned and expressed in E. coli, yeast and vaccinia virus. The recombinant antigen significantly protected rats, hamsters and baboons against a challenge infection. P28-I is a glutathione-S-transferase and the recombinant antigen produced in yeast exhibits the enzyme activity and has been purified to homogeneity by affinity chromatography. A second P28 antigen, P28-II, has also been cloned, fully sequenced and expressed. This recombinant antigen also protects against S. mansoni infection.