Immunologic diagnosis of Schistosomiasis. I. A controlled study of intradermal (immediate and delayed) and serological tests in St. Lucians with Schistosoma mansoni and in uninfected St. Vincentians

In order to test the efficacy of antibody-mediated immunologic methods for the diagnosis of schistosomiasis (immediate intradermal and serological tests) and to compare them with a cell-mediated immunologic reaction (the delayed intradermal test), 350 subjects were examined. Approximately half of them were from the West Indian island of St. Lucia, all with proven schistosomiasis mansoni on fecal examination, and the other half were comparable subjects from St. Vincent, an island 30 miles distant where schistosomiasis has never been found. Five different antigens utilized in the intradermal tests (prepared from Schistosoma mansoni cercariae, adult worms and eggs, and from S. haematobium and S. japonicum eggs) were injected blindly in a randomized manner. The antigens were almost equally and highly sensitive in the immediate skin reaction in the adult St. Lucians (89-95 percent, with the exception of S. haematobium, 74 percent), but were far less sensitive in the children. There was a large number of false positive immediate responses among the Vincentians, e.g., 44 of 171 subjects tested with the S. mansoni cercarial antigen. Delayed skin reactions, which among the St. Lucians reached a peak of 66 percent positively with S. mansoni adult worm antigen, were less sensitive than the immediate reactions, but appeared to be more specific. Among the antigens (S. haematobium and S. japonicum eggs), while the Vincentians had very few false positive reactions with the homologous and none with the heterologous antigens. Of the three serologic tests (complement fixation, cholesterol-lecithin flocculation, and flourescent antibody), the first two were insensitive and non-specific; the third was the only one that provided results which were at all acceptable.(AU)

Sickle cell haemoglobinopathy and Schistosoma mansoni infection

Since the blood fluke, Schistosoma mansoni apparently utilizes host haemoglobin as a major nutrient, the question was raised as to whether the parasite will develop and function normally in hosts with abnormal haemoglobins. When a 13 year old negro girl with heavy schistosome infection was found to have sickle cell anaemia, her parents and four siblings were exammined. Quantitative faecal egg counts were also peformed on five additional patients with sickle cell anaemia. Furthermore, the prevalence of schistosomiasis in a group of 147 urban children and the faecal egg output of 103 rural children with and without sickle cell trait was studied. The data indicate that sickle cell haemoglobinopathy has no influence on either the prevalence of shchistosomiasis or the degree of infection as estimated by stool egg count (AU)