A comparative study on the pathogenicity of two strains of Schistosoma mansoni one from Bor District and the other from the Gezira in the Sudan, using Cercopithecus aethiops monkeys as experimental hosts. The results, which were based on the assessment of various clinical, parasitological and pathological parameters, indicated that Bor strain was responsible for a more severe type of disease than its Gezira counterpart. Monkeys infected with Bor parasite generally revealed higher worm and egg loads, more marked changes in Hb content and body weight gain and more extensive lesions in the liver and two monkeys died.

In the Sudan, it has often been noted that the disease produced by Schistosoma mansoni, as observed among patients from Bor District in the Southern Region, is far more severe than that usually encountered in those from the Gezira in the northern part of the country. These two areas which are about 500 miles apart differ widely in their climate, indigenous population, and social and economic status. It has been suspected that differences in the pathogenicity of the local S. mansoni strains may be one of the important factors determining the clinical presentation of the disease. Accordingly, a comparison of these two strains was undertaken, using the green monkey, Cercopithecus aethiops, as an experimental model. These animals varied in their response to the schistosomal infection, irrespective of the strain used, but the group infected with the Bor strain generally suffered from a more severe illness than their counterparts infected with the Gezira form of the parasite. This was evidenced by the higher worm and egg loads, and consequently the more severe clinical and pathological effects shown by the former group.