Nutritional status of children with schistosomiasis mansoni in two different areas of Machakos District, Kenya.

A possible association between nutritional status and Schistosoma mansoni infection or morbidity was investigated by comparing anthropometric indices among 362 children from 3 primary schools in Machakos District, Kenya. Matithini was a prosperous school in an area (Kangundo) of moderate intensity of schistosome infection but low associated morbidity. A second area (Kambu) showed more severe schistosome-associated morbidity: in this area, Kitengei school was prosperous and with high intensities of schistosome infection, while Misuuni school was less prosperous and with low intensities of infection.

Human IgE responses to Schistosoma mansoni and resistance to reinfection.

Schistosoma mansoni infected Kenyan patients were treated and the intensities of their reinfections were followed over the next two years. In addition, their pre- and six month post-treatment serum levels of IgG1-4, IgM, and IgE, specific for schistosomula, egg and adult worm, were measured in ELISA. No reinfection took place before six months post-treatment.

Identification of schistosome-infected snails by detecting schistosomal antigens and DNA sequences.

Cercarial shedding tests do not provide species identification of the schistosomes concerned and cannot detect prepatent schistosomal infections. We have demonstrated that both immunodetection by ELISA of schistosomal antigens in snail hemolymph, and dot hybridization of snail extracts by a DNA probe representing highly repeated sequences, proved suitable for detecting infected snails during prepatency as well as patency. A group-specific monoclonal antibody was found to be suitable for detecting Schistosoma mansoni infection in Biomphalaria sp.

Age-targeted chemotherapy for control of urinary schistosomiasis in endemic populations.

Severity of urinary tract morbidity increases with intensity and duration of Schistosoma haematobium infection. We assessed the ability of yearly drug therapy to control infection intensity and reduce S. haematobium-associated disease in children 5-21 years old in an endemic area of Kenya.

Comparison of different chemotherapy strategies against Schistosoma mansoni in Machakos District, Kenya: effects on human infection and morbidity.

A comparison was made of the long-term impact of different methods of administration of chemotherapy (oxamniquine, 30 mg/kg in divided doses; or praziquantel, 40 mg/kg) on prevalence and intensity of Schistosoma mansoni infection in four areas in Kangundo Location, Machakos District, Kenya. In Area A, treatment was offered in October 1983 and again in April 1985 to all infected individuals. In Area H, treatment was offered in April 1985 to individuals excreting greater than or equal to 100 eggs per gram (epg) of faeces.

Chemotherapy-based control of schistosomiasis haematobia. IV. Impact of repeated annual chemotherapy on prevalence and intensity of Schistosoma haematobium infection in an endemic area of Kenya.

To determine the effect of repeated, annual, age-targeted therapy on prevalence and intensity of Schistosoma haematobium infection in an endemic area, we treated all available, infected, school-age children (n = 2, 493) in the Msambweni area of Coast Province, Kenya with a randomized protocol of oral metrifonate (10 mg/kg for three doses each year) or praziquantel therapy (40 mg/kg as a single dose each year) for a period of one to three years. During 1984-1987, 1, 101 children completed three years of therapy, 550 received two years, and 842 received a single year. Annual followup revealed significant long-term suppression of S.

Differences in the rate of hepatosplenomegaly due to Schistosoma mansoni infection between two areas in Machakos District, Kenya.

The relationship between intensity of Schistosoma mansoni infection and the degree of related morbidity was suspected to differ locally within the Machakos district of Kenya. To test this possibility, prevalences of hepatomegaly and splenomegaly among 1483 school children were compared between 2 areas, Kangundo and Kambu, within this district. These areas, which were similar in many geographical and economic respects and populated by the same tribe (Akamba), had comparable levels of S.

Antibody response of Schistosoma mansoni-infected human subjects to the recombinant P28 glutathione-S-transferase and to synthetic peptides.

The 28-kilodalton antigen of Schistosoma mansoni has been previously described as having importance as the basis for a potential vaccine. The P28 recombinant molecule and three peptides derived from its primary sequence, namely the 24-43, 115-131, and 140-153 peptides, have been tested to evaluate the humoral responses of Kenyan school children previously classified as susceptible or resistant to reinfection after chemotherapy. We report here that the P28 molecule and two of the peptides studied (peptides 115-131 and 140-153) can be used for detecting specific immunoglobulin G (IgG), IgE, and IgA antibodies.

Chemotherapy-based control of schistosomiasis haematobia. II. Metrifonate vs. praziquantel in control of infection-associated morbidity.

To determine the relative efficacy of metrifonate and praziquantel in controlling urinary tract morbidity due to Schistosoma haematobium infection, a random allocation treatment trial was performed among 1,813 school age S. haematobium-infected children from the Msambweni area of Coast Province, Kenya. Following baseline examination for infection, hematuria, proteinuria, and ultrasonographic urinary tract abnormalities, oral treatment with either metrifonate (10 mg/kg, repeated at 4 month intervals) or praziquantel (1 dose of 40 mg/kg) was given to infected subjects.

Chemotherapy-based control of schistosomiasis haematobia. 3. Snail studies monitoring the effect of chemotherapy on transmission in the Msambweni area, Kenya.

Regular snail sampling was performed at 40 sites, representing the principal snail habitats, during a 4 year chemotherapy programme targetted at school-children in the Msambweni area of the coastal plain of Kenya. Populations of Bulinus africanus group snails, primarily from pools, showed seasonal variations, dropping when sites dried out and rising when they were refilled by the rains. Transmission, judged by the recovery of snails shedding typical fucocercous cercariae, continued throughout the treatment period at very low levels (less than 1% of the snails collected were infected) with peaks in October/November and in January/February after seasonal rains.

A comparative evaluation of snail sampling and cercariometry to detect Schistosoma mansoni transmission in a large-scale, longitudinal field-study in Machakos, Kenya.

In an operational Schistosoma mansoni field-study in an area about 20 km 2 (population approximately 8000), transmission detection by simple snail sampling was compared with cercariometry. Between 1985 and 1987, 62 field sites were sampled at fortnightly intervals. Of a total of 2758 field observations, 89.

Identification of snails infected with schistosomes by ELISA employing monoclonal antibodies: Schistosoma mansoni in laboratory snails (Biomphalaria glabrata) and in field snails (Biomphalaria pfeifferi) from Kenya.

An enzyme-linked immunosorbent assay (ELISA) employing monoclonal antibodies was used for detecting Schistosoma mansoni antigens in hemolymph of laboratory snails (Biomphalaria glabrata) in Kenya. Infected laboratory snails shedding cercariae were differentially identified by ELISA from uninfected snails with 100% sensitivity and specificity. Prepatent infections were detected by ELISA from 2 weeks after exposure to miracidia.

Dose-finding study for praziquantel therapy of Schistosoma haematobium in Coast Province, Kenya.

To assess the efficacy of low dose praziquantel regimens in comparison with standard 40 mg/kg dosing in the treatment of urinary schistosomiasis, a random allocation dose-finding trial was performed in children and adults from a Schistosoma haematobium endemic region in Coast Province, Kenya. Following an initial screening, 280 individuals with greater than or equal to 50 eggs/10 ml urine were randomly assigned to receive either 10, 20, 30, or 40 mg/kg of the drug in a single oral dose. Two to three months later, cure rates of 26%, 68%, 78%, and 84% were found for the 10, 20, 30, and 40 mg/kg doses, respectively.

Longitudinal studies on human schistosomiasis.

A major difficulty in understanding the epidemiology of human schistosomiasis has been to distinguish between acquired immunity and reduced exposure as possible reasons for an observed decline, in older individuals, of levels of superinfection or of reinfection after chemotherapy. A series of studies of Schistosoma mansoni infections in Kenya has been undertaken to approach this problem, by investigation of intensities of reinfection after treatment of individuals whose levels of contact with contaminated water is subsequently observed. Intensities of reinfection are highest among younger children, thereafter declining sharply.

Urinary tract morbidity in schistosomiasis haematobia: associations with age and intensity of infection in an endemic area of Coast Province, Kenya.

To gain better understanding of the natural history of Schistosoma haematobium associated disease, age- and intensity-related urinary tract morbidity were assessed in a cross-sectional study of Kilole (population 719) in Coast Province, Kenya. Overall prevalence of infection was 65% (39% light, 16% moderate, 9% heavy). Infection prevalence and mean intensity of infection were highest in the 5-14-year-old bracket for both sexes.

Chemotherapy-based control of schistosomiasis haematobia. I. Metrifonate versus praziquantel in control of intensity and prevalence of infection.

To determine the effect of targeted field administration of oral chemotherapeutic agents on the prevalence, intensity, and morbidity of Schistosoma haematobium infections, we initiated a long-term school-based program in the Msambweni area of Kwale District, Coast Province, Kenya. Prior to treatment, 69% of the children examined (ages 4-21, n = 2,628) were infected; 34% had moderate or heavy infections (greater than 100 eggs/10 ml urine). Infected individuals were randomized to receive, during one year, either metrifonate (10 mg/kg x 3 doses) or praziquantel, (40 mg/kg x 1 dose).

Immunity in human schistosomiasis mansoni: cross-reactive IgM and IgG2 anti-carbohydrate antibodies block the expression of immunity.

We have previously reported that the slow development of immunity to reinfection after treatment of Schistosoma mansoni infections is partly attributable to the continued presence of 'blocking' antibodies in young, susceptible children. A further analysis of this phenomenon supports the hypothesis that such blocking antibodies can be of the IgG2 as well as the IgM isotype, and that they react with carbohydrate epitopes expressed both on egg polysaccharides and on schistosomulum surface antigens, of particular importance being those antigens that are shed from the schistosomulum surface during the early stages of maturation in vitro. Evidence is also presented that, in those patients lacking high levels of IgG2 blocking antibodies, resistance to reinfection after treatment is associated with the presence of other IgG isotypes against the same shed antigens.

Effect of mass chemotherapy and piped water on numbers of Schistosoma haematobium and prevalence in Bulinus globosus in Kwale, Kenya.

From June 1982 to May 1986 in a small village in Kwale, Kenya, we studied seasonal fluctuations in populations of Bulinus globosus, prevalence of Schistosoma haematobium infection in this snail, and effects of chemotherapy and piped water supply on infection rate of snails. In the perennially-flowing Pemba River, relatively small numbers of snails were collected; they were found only during the hot dry season (December to March). In a tributary stream, the Kadingo River, whose flow ceased at the end of both the cool and hot dry seasons, snail numbers peaked at the end of the cool dry season (October to November) and at the beginning of the hot dry season (January).

Predisposition of humans to infection with Schistosoma mansoni: evidence from the reinfection of individuals following chemotherapy.

In a study of faecal egg counts of Schistosoma mansoni from 359 people of all ages from a rural Kenyan community, a positive association was demonstrated between infection intensity in individuals before treatment and reinfection intensity in the same individuals 9 months after treatment in certain age groups of the sampled population. Consequences and possible causes of these observations are discussed in terms of the epidemiology and control of schistosomiasis.

Human antibody responses to Schistosoma mansoni: the influence of epitopes shared between different life-cycle stages on the response to the schistosomulum.

Sera from 120 Kenyan schoolchildren who were infected with S. mansoni were individually examined, using an enzyme-linked immunoabsorbent assay (ELISA), for the presence of IgG and IgM antibodies reactive with antigens derived from adult worms, the outer membrane of the schistosomulum or from the parasite egg. In addition, antibodies against more purified egg antigens, an egg stage-specific glycoprotein preparation and a polysaccharide egg antigen known to share epitopes with the schistosomular surface were measured in ELISA, as were antibodies reactive with trichloroacetic acid-soluble and periodate-insensitive antigens derived from the outer membrane of schistosomulum and antigens shed when schistosomula were cultured in vitro.

Immunity to schistosomes: progress toward vaccine.

Among the major parasitic infections, schistosomiasis may be the most promising candidate for human vaccination. Information about mechanisms of immunity, gained mainly from experimental models but likely to be relevant to human infection, indicates a dynamic balance between protective and regulatory (blocking) mechanisms. Besides cell-mediated responses leading to macrophage activation, antibody-dependent cell-mediated cytotoxicity systems involving precise antibody isotypes and nonlymphoid cells (mononuclear phagocytes, eosinophils, and platelets) appear to be essential effectors of immune attack.

Preliminary evaluation of some wild and cultivated plants for snail control in Machakos District, Kenya.

Fifty local medicinal, agricultural and wild growing deciduous plants, representing 49 species, 46 genera and 22 families, were screened as water extracts at 1:1000 concentration for molluscicidal activity against Biomphalaria pfeifferi in Machakos District, Kenya. Forty-seven of the 50 (94%) plants and 106 of the 134 (79%) plant materials (roots, stems, leaves, fruits, flowers and seeds) were molluscicidal. The leaves of Pappea capensis (Sapindaceae), Steganotaenia araliacea (Umbelliferae), Zornia setosa subsp.