L'extension geographique de la bilharziose a Schistosoma intercalatum en Afrique tropicale

Abstract

The specificity of S. intercalatum as a cause of intestinal schistosomiasis, and the separate identity of this infection, were established by Fisher in 1934. The original geographical distribution was in Equatorial Africa (Congo, Gabon), and the classical intermediate snail host is Bulinus (Physopsis) africanus. Since 1966 there has been a spread of this infection from the original foci in the Congo and Gabon as far as Cameroun, where, between 1966 and 1969, 9 foci have been discovered. These are, in South Cameroun (3° to 6° N.) the foci of Eséka, Edea, Mbalmayo, Yaoundé, Obala and Bokito; in West Cameroun the focus of Penja (50 km. northwest of Douala); in North Cameroun the foci of Garoua (Benoué) and Maroua (Diamare). The number of cases discovered in Cameroun is now 700. Details are given of the numbers of cases found during 1966-68 in various areas of the region, the rates of infection ranging from 5.71 in Obala to 24.3% in Yaoundé Severe infections are common, particularly in young people, presumably as a result of massive infections. Treatment with niridazole is fairly satisfactory, though relapses have been observed in the absence of opportunity for reinfection. A new intermediate host, Bulinus (Pyrgophysa) forskali, has now been recognized in Cameroun and Gabon; this snail is present in practically the whole of tropical Africa. The importation of S. intercalatum into Cameroun runs parallel with the movements of infected labourers and nomadic peoples from Gabon or the Congo. Such movements are favourable to the spread of parasitic diseases. Extension within Cameroun, from the south northwards, follows the traditional nomad route from south Cameroun to the Tchad basin, across the Adamoua massif. African nomadism and the exchange of African labourers, which have followed the great increase in the facilities of transport, as well as the very wide geographical distribution of Pyrgophysa forskali and Physopsis africanus in equatorial and tropical Africa, suggest that this infection may continue to spread on a large scale. The sanitary services of the République Centrafricaine and Tchad have not discovered evidence of foci introduced from outside, but have shown that introduction is possible. We suggest that in Nigeria, the Sudan, Tanzania and Angola the situation should be studied.