Natural history of papillary lesions of the urinary bladder in schistosomiasis.
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Variable epithelial hyperplasia was observed in urinary bladder of nine capuchin monkeys (Cebus apella) when examined at cystotomy 94 to 164 weeks after infection with Schistosoma haematobium. These hosts were followed for 24 to 136 weeks postcystotomy to determine the status of bladder lesions in relation to duration of infection and to ascertain whether lesion samples removed at cystotomy reestablished themselves in autologous and heterologous transfers. There was involution of urothelial hyperplasia in eight of nine animals and no evidence for establishment of transplanted bladder lesions. (+info)
Candidate parasitic diseases.
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This paper discusses five parasitic diseases: American trypanosomiasis (Chagas disease), dracunculiasis, lymphatic filariasis, onchocerciasis and schistosomiasis. The available technology and health infrastructures in developing countries permit the eradication of dracunculiasis and the elimination of lymphatic filariasis due to Wuchereria bancrofti. Blindness due to onchocerciasis and transmission of this disease will be prevented in eleven West African countries; transmission of Chagas disease will be interrupted. A well-coordinated international effort is required to ensure that scarce resources are not wasted, efforts are not duplicated, and planned national programmes are well supported. (+info)
Double-blind placebo-controlled study of concurrent administration of albendazole and praziquantel in schoolchildren with schistosomiasis and geohelminths.
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A double-blind placebo-controlled study of the concurrent administration of albendazole and praziquantel was conducted in>1500 children with high prevalences of geohelminths and schistosomiasis. The study sites were in China and the Philippines, including 2 strains of Schistosoma japonicum, and 2 different regions of Kenya, 1 each with endemic Schistosoma mansoni or Schistosoma haematobium. Neither medication affected the cure rate of the other. There was no difference between the side effect rate from albendazole or the double placebo. Praziquantel-treated children had more nausea, abdominal pain, and headache but these side effects were statistically more common in children with schistosomiasis, suggesting a strong influence of dying parasites. The subjects were followed for 6 months for changes in infection status, growth parameters, hemoglobin, and schistosomiasis morbidity. In all 4 sites, a significant 6-month increase in serum hemoglobin was observed in children who received praziquantel, strongly supporting population-based mass treatment. (+info)
Age-specific decrease in seroprevalence of schistosomiasis in Puerto Rico.
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In our previous work, we reported the first systematic, island-wide, serologic survey for schistosomiasis in Puerto Rico in 40 years. In that study, approximately 3,000 serum samples from the 76 municipalities comprising the island of Puerto Rico were tested for the detection of antibodies to S. mansoni microsomal antigens by the Falcon assay screening test-enzyme-linked immunosorbent assay (FAST-ELISA) and those positive were confirmed by an enzyme-linked immunoelectrotransfer blot (EITB). The highest EITB positivity was found in 17 municipalities, which comprised 48% of all seropositive samples. An additional finding was that 10% of the 215 EITB-positive samples were from individuals 25 years or younger and were for the most part of residents from the high seroprevalence areas. Thus, for this study we focused on 766 individuals 25 years of age or younger (45.5% males and 54.4% females), two-thirds of which were from 10 municipalities with the highest EITB seropositivity, and one-third from the 10 municipalities with the lowest EITB seropositivity found in our previous study. Of all samples, the results showed an overall FAST-ELISA positivity of 11.6%, with males similar to females (12.6 versus 10.7%, respectively). Confirmation by EITB was only 1.8%, with a males three-fold higher than females (3% versus 0.7%). When seropositivity was measured by age in five-year increments, a clear age-specific decrease in seropositivity was observed. Thus, by FAST-ELISA, 16.7% of the 21-25-year-old age group was positive, decreasing to 14.6%, 9.9%, 7.9%, and 9.3% in the 16-20-, 11-15-, 6-10-, and 1-5-year-old age groups, respectively. Confirmatory EITB showed even more impressive results: 4.7%, 2.6%, 1.2%, 0.7%, and 0% in the same age brackets. With regard to the high prevalence municipalities, only four of 10 (11 of 228 = 4.8%) had confirmatory EITB-positive samples and most were from municipalities of the Rio Grande de Loiza River basin and tributaries. The male to female positivity ratio was 4:1. Of the low prevalence municipalities, only single positive cases (by EITB) were found in three disperse municipalities. These results support the concept that there has been little transmission of S. mansoni in Puerto Rico during the first half of the 1990s and confirms anecdotal comments of local physicians who have seen virtually no new infections during the past three years. This makes the documentation of eradication of schistosomiasis from Puerto Rico feasible, a goal that should be set as being before the 100th anniversary of its discovery on the island by Isaac Gonzalez-Martinez in 1904. (+info)
Full results of the genome-wide scan which localises a locus controlling the intensity of infection by Schistosoma mansoni on chromosome 5q31-q33.
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Three hundred million individuals are at risk of infection by schistosomes, and thousands die each year of severe hepatic disease. Previous studies have shown that the intensity of infection by Schistosoma mansoni in a Brazilian population is controlled by a major gene, denoted as SM1. We report here the full results of a genome-wide search that was performed on this population to localise SM1. Two hundred and forty-six microsatellites were used for the primary map, and only one region in 5q31-q33 provided significant evidence of linkage. SM1 was subsequently mapped to this region, which contains several genes encoding cytokines or cytokine receptors which are involved in protection against schistosomes. Three additional regions, 1p22.2, 7q36 and 21q22-22-qter, yielded promising, although not significant, lod-score values. These regions contain candidate genes encoding cytokines or molecules relevant to anti-schistosome immunity. (+info)
Cytotoxicity of human and baboon mononuclear phagocytes against schistosomula in vitro: induction by immune complexes containing IgE and Schistosoma mansoni antigens.
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Normal human blood monocytes, pre-incubated at 37 degrees C with sera from patients infected with Schistosoma mansoni, strongly adhered to S. mansoni schistosomula in vitro, whereas no significant adherence was induced by sera from uninfected individuals. Comparable adherence occurred with normal baboon blood monocytes or peritoneal macrophages when these cells were incubated with sera from S. mansoni-infected baboons. Adherence of macrophages to schistosomula was associated with damage to the larvae, as estimated by a 51Cr release technique. Neither adherence nor cytotoxicity was induced by pre-incubation of the schistosomula, instead of the monocytes, with immune serum. The relevant factor in immune serum was heat-labile, but was not a complement component. Absorption and ultracentrifugation experiments showed that immune complexes, containing S. mansoni-specific IgE antibody and soluble parasite antigens, produced monocyte or macrophage adherence and cytotoxicity. Similar observations have been reported previously in the rat model. Since the production of large amounts of IgE is a predominant feature of schistosome infections in man and experimental animals, it is possible that this new mode of mononuclear phagocyte activation could act as an immune effector mechanism against S. mansoni. (+info)
Controlling schistosomiasis: the cost-effectiveness of alternative delivery strategies.
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Sustainable schistosomiasis control cannot be based on large-scale vertical treatment strategies in most endemic countries, yet little is known about the costs and effectiveness of more affordable options. This paper presents calculations of the cost-effectiveness of two forms of chemotherapy targeted at school-children and compares them with chemotherapy integrated into the routine activities of the primary health care system. The focus is on Schistosoma haematobium. Economic and epidemiological data are taken from the Kilombero District of Tanzania. The paper also develops a framework for possible use by programme managers to evaluate similar options in different epidemiological settings. The results suggest that all three options are more affordable and sustainable than the vertical strategies for which cost data are available in the literature. Passive testing and treatment through primary health facilities proved the most effective and cost-effective option given the screening and compliance rates observed in the Kilombero District. (+info)
Eradication of schistosomiasis in Guangxi, China. Part 3. Community diagnosis of the worst-affected areas and maintenance strategies for the future.
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Reported are the results of a community-based assessment of maintenance of schistosomiasis eradication in Guangxi, a large autonomous region of China with a population of 44 million. Eradication of the disease was achieved in 1989 in Guangxi but maintenance costs are rising. We focused on three counties that had the most intense transmission in the past: Binyang, Jingxi, and Yishan. Four instruments were used: in-depth interviews, focus group discussions, a knowledge, attitudes and practices survey, and subsequent community feedback. In the past, schistosomiasis had serious consequences in Guangxi, decreasing work capacity and restricting marriage and occupational mobility. Since its eradication there have been clear benefits in terms of increased agricultural output and improved farming conditions. Personal habits and traditional manual farming activities in Guangxi would continue to expose a large proportion of the population to environmental risk if the disease were to return. Ignorance about control programme achievements is increasing and is related to youth and inexperience. There was a universal desire in the study counties for more local education about the history of the programme and about the risk of schistosomiasis returning. Snail surveillance is considered important, but people are not willing to volunteer for such work. Our study methods were novel for Guangxi and community feedback was helpful. Snail checking procedures have been modified to make them more efficient and no snails have been found since 1992. The animal and human stool examinations have ceased and vigilance now concentrates on snails and children (skin tests). The long-term strategy is to make the population invulnerable to future schistosomiasis transmission if the snail vectors return. This means continuing education and making the former endemic counties a high priority for water and sanitation improvements. (+info)