Schistosomiasis in the Republic of São Tomé and Principe: characterization of Schistosoma intercalatum

Abstract

This paper reports the morphological and biochemical characterization of the species of Schistosoma infecting humans in the Republic of São Tomé and Principe. The eggs are typical in shape and size of S. intercalatum, measuring on average between 174.5 microns and 189.1 microns. The eggs are voided in the faeces and not the urine of infected people. The parasite experimentally develops in several different species of Bulinus belonging to the B. forskalii group, including B. forskalii, with a minimum prepatent period of 25 d, and also in snails of the B. reticulatus group (B. wrighti); it is incompatible with snails of the B. africanus and B. truncatus/B. tropicus complex. A survey of 5 different habitats at intervals of 2 weeks over a period of one year showed that populations of B. forskalii increased during the dry period of June, July and August in 1988, and in 3 of the habitats snails were present throughout the year. Hence transmission may take place in these habitats throughout the year. Preliminary evidence suggests that water velocity is a limiting factor confining Bulinus to the north-east of the island where the terrain is less mountainous. Development of schistosomes from São Tomé was followed in experimentally infected hamsters. The cross-over point (the point at which the paired male and female worms are of the same average length) occurred at about 49 d after infection: eggs were first seen in the uteri of the female worms 48 d after infection. The parasite from São Tomé developed in sheep and produced viable eggs.(ABSTRACT TRUNCATED AT 250 WORDS)

Natural Interactions betweenS. haematobiumandS. guineensisin the Republic of Benin

“…Comparison of egg sizes found in the present study with published data shows that: (i) the mean egg length of the S. haematobium morphotype (146  μ m for Dangbo samples and 139  μ m for Doh samples) was similar to that of S. haematobium reported by Pitchford [23] (131–142  μ m), Loker [24] (144  μ m), and Richard-Lenoble and colleagues [25] (146  μ m); (ii) the mean egg length of the intermediate morphotype (151  μ m for both Dangbo and Doh samples) was similar to that of hybrids collected from urine by Mintsa Nguema and colleagues [26] (144 and 159  μ m) and Brown and colleagues [8] (151  μ m); (iii) the mean egg length of the S. guineensis morphotype (158  μ m for Dangbo samples and 164  μ m for Doh samples) was less than that of S. guineensis collected from feces by Wright and colleagues [6] (172  μ m), Richard-Lenoble and colleagues [25] (173  μ m), Southgate and colleagues [7] (175–189  μ m), and Pagès and Théron [27] (188  μ m). Consequently, our morphological data are correlated with previous data for S. haematobium and hybrids of S. haematobium and S. guineensis , but inconsistent with previous data for S. guineensis .…”

Prevalence of intestinal parasitic infections among school children in capital areas of the Democratic Republic of São Tomé and Príncipe, West Africa

“…However, IPIs studies in SAC are quite rare; only two studies conducted in 1987 and 2005 indicated that the prevalence of A. lumbricoides, T. trichiura, and some intestinal protozoan infections were fairly high in SAC [13][14][15][16][17] . Largely from 2005 onwards, the DRSTP accepted the advice of non-governmental organizations (NGOs) to begin SAC-based deworming program using a single-dose mebendazole regimen annually.…”

“…Although limited information is available regarding the IPIs status among inhabitants of the Democratic Republic of Sao Tome and Principe (DRSTP) [13][14][15][16][17] , like other developing countries, IPIs are supposedly a major health problem in the DRSTP due to tropical climatic and poor hygienic conditions. However, IPIs studies in SAC are quite rare; only two studies conducted in 1987 and 2005 indicated that the prevalence of A. lumbricoides, T. trichiura, and some intestinal protozoan infections were fairly high in SAC [13][14][15][16][17] .…”

Competitive exclusion in human schistosomes: the restricted distribution ofSchistosoma intercalatum

“…The Zaire strain of S. intercalatum was known to occur only in the North East of Zaire while the Lower Guinea strain was reported in Gabon and Cameroon (Doumenge et al 1987). Over the last 10 years, new foci of transmission of the Lower Guinea strain have been reported, either within the historically endemic countries (Gabon and Cameroon) (Brown et al 1984;Burchard & Kern, 1985) or in new countries (Nigeria, Mali, Equatorial Guinea and Sao Tome) (Corachan et al 1987(Corachan et al , 1988Arene, Ukeibo & Nwawze, 1989;Simarro, Sima & Mia, 1989;Southgate et al 1994). Sporadic cases of S. intercalatum infections have also been reported from Central African Republic, Chad, Angola, Burkina Fasso, Congo, Uganda and Senegal, but no active foci of transmission have so far been described in these countries.…”