A controlled study of morbidity of Schistosomiasis mansoni in St. Lucian children, based on quantitative egg excretion

A study of the morbidity of schistosomiasis mansoni was made in 138 schoolchildren (age range, 7-16 years) in St. Lucia. The study was based on quantitative egg excretion data collected over a 4-year period before the study and included a comparable uninfected control group. All examinations were carried out "blind". Infected subjects were divided into three levels of intensity of infection: heavy, 400 or more eggs/ml of feces; moderate, 100 to 300 eggs/ml; and light, 10 to 75 eggs/ml. The children were hospitalized for medical histories and physical and laboratory examinations. Gastrointestinal symptoms were present at relatively high levels in all groups, and were more frequent in the Schistosoma mansoni-infected subjects than in the controls. Anthropometric measurements showed no differences between the groups. Hepatomegaly and splenomegaly were significantly more frequent in the heavy-moderate infection group, and extension of the liver below the coastal margin was found to increase with intensity of infection; serum albumin level was inversely related. It was clear that in this St. Lucian study, infection with S. mansoni did not result in disease in most of the school-age subjects investigated; assessment of possible long-term(>4 years) effects was not made. This study provides a method for assessing morbidity of schistosomiasis based on quantitative egg excretion and demonstrates the relation of objective morbidity to intensity of infection.(AU)

Morbidity of schistosomiasis mansoni in St. Lucia and the response of hepatosplenic disease to treatment

A study was undertaken to objectively evaluate the morbidity of schistosomiasis mansoni in St. Lucia. School children (138) selected on the basis of long-standing infection at 3 intensities of infection (based on quantiative egg excretion) were evaluated blind to determine symptoms, signs and laboratory manifestations of disease. Symptoms in infected patients did not differ from the uninfected control group. Liver enlargement and serum protein abnormalities were found to be directly related to the intensity of infection. Splenomegaly was found in the more heavily infected patients. A review of the effect of treatment in cases of hepatosplenic disease shows that 62 percent of enlarged livers and 50 percent of enlarged spleens returened to normal. Younger patients were found to be more likely to respond to treatment (AU)

Immunologic diagnosis of schistosomiasis. III. The effects of nutritional status and infection intensity on intradermal test results in St. Lucian children

The question of the insensitivity of immediate and delayed skin testing in children was studied with respect to both nutritional status and intensity of infection. Ninety-seven children on the island of St. Lucia, 5 to 11 years of age, with almost equal male:female distribution, all excreting eggs of Schistosoma mansoni were tested as follows: qualitatively and quantitative stool examinations; anthropometric measurements (height, weight, mid-arm circumference and triceps skinfold thickness); hematocrit; fluorescent antibody test; and skin tests with control material, S. mansoni adult worm antigen (both Puerto Rican and St. Lucian strains), and intermediate strenght PPD tuberculin. The anthropometric measurements revealed marginal malnutrition among the children. The overall positive intradermal response rate for each of the two antigens was similar, being 56 percent for the immediate and 37 percent for the delayed test. There was no relationship discernible between relative over- and under-nutrition and the skin test responses. A striking and highly significant positive association was revealed, however, between the intensity of infection, as shown by quantitative egg counts, and the sensitivity and extent of both the immediate and delayed skin test reactions.(AU)

Immunologic diagnosis of schistosomiasis. II. Further studies on the sensitivity and specificity of delayed intradermal reactions

The specificity of the delayed intradermal reaction was compared to that of the immediate response in 80 adult St. Lucians with proven schistosomiasis mansoni, using homologous and heterologous antigens. Adult worm antigens at a uniform concentration of 35æg/ml from four geographic strains of Schistosoma mansoni (St. Lucian, Puerto Rican, Brazilian, and Egyptian) and from S. haematobium and S. japonicum were color coded and injected randomly in the skin of the upper back. The immediate reactions to all the antigens showed equal sensitivity (94 to 99 percent positive). The delayed reactions with the four S. mansoni strains ranged from 49 to 60 percent positively, but the heterologous S. haematobium and S. japonicum antigens were significantly less sensitive, with only 20 percent and 30 percent positive reactions. In an attempt to improve the sensitivity of the delayed intradermal test, 30 of the 80 St. Lucians were retested 1 month later with different concentrations of the Puerto Rican antigen (5, 15, 35, 70 æg/ml). Immediate rections were 100 percent at all but the lowest concentration (93 percent). Delayed reactions were at their peak (87 percent) at the standard concentration of antigen (35 æg/ml), the other concentrations being similar with the exception of the lowest (53 percent). Comparisons of the results of the two series of tests performed 1 month apart in the same individuals revealed no changes in the immediate reactions, but a marked increase in both the percentage positivity and the mean lesion area in the delayed response.(AU)

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)