Showing papers on "Schistosoma haematobium published in 1976"

Schistosomiasis at Loum, Cameroun; Schistosoma haematobium, S. intercalatum and their natural hybrid.

Abstract: A survey of 500 schoolchildren in Loum in 1968 revealed an overall infection rate of 54.2% with Schistosoma intercalatum and this was the only species of schistosome encountered. In 1972 a number of children were found to be passing schistosome eggs in their urine and these eggs ranged in shape and size from the forms characteristic for S. haematobium to those of S. intercalatum. Preliminary laboratory studies demonstrated that hybridisation between the two species was occurring. Subsequent field surveys showed that the snail hosts for the two parasites (B. rohlfsi for S. haematobium and B. forskali for S. intercalatum) were both present in the river Mbette and its tributaries in Loum and the distribution of the two snail species coincided closely with the distribution of the schistosomes in the human population. Detailed study of a small group of children passing hybrid eggs in their urine revealed that few of them were passing eggs in their faeces and that those eggs which were found in faeces were not viable. Analysis of schistosome egg-shape by plotting cumulative size-frequency data on probability paper demonstrated that the graph obtained from a natural hybrid series was different from that given by a known mixture of the two separate species. The hybrid series included a number of exceptionally large eggs resembling those of S. bovis but isolation of these eggs and subsequent laboratory passage of the parasites showed that they were part of the series and were not evidence of the presence of a third species. Hybridisation experiments in the laboratory showed that the cross S. haematobium ♂ × S. intercalatum ♀ is fully viable but that the reverse mating is not successful, thus accounting for the failure of the faecal eggs recovered from children with hybrid infections. Histological results from laboratory passaged hybrids suggest that the Ziehl-positive staining reaction of the egg-shells of S. intercalatum may be a recessive character. The observations reported here indicate that S. haematobium has only recently become established in Loum and that it is, through introgressive hybridisation, replacing the indigenous S. intercalatum. A suggested explanation for the change in the parasite fauna is offered and this depends upon ecological changes resulting from forest clearance and agricultural development providing improved conditions for the spread of B. rohlfsi, the snail host for S. haematobium. It is suggested that, in contrast to recent reports on the spread of S. intercalatum, this species is in fact retreating and being replaced by S. haematobium in areas where forest clearance is taking place. In conclusion it is suggested that introgressive hybridisation of this kind may have been responsible for the evolution of certain characteristic local strains of African schistosomes.

Studies on schistosomiasis in Saudi Arabia.

Abstract: During studies on schistosomiasis in Saudi Arabia, urine and stool samples from inhabitants of various areas (mostly rural) were examined, and 97 aquatic habitats in 46 localities were searched for snails. The results indicate the occurrence of both urinary and intestinal schistosomiasis in most parts of the country, with a patchy distribution and varying infection rates. The snail intermediate host of Schistosoma mansoni was found to be Biomphalaria arabica. For S. haematobium three species of snails, namely, Bulinus truncatus and B. beccarii in the west and B. reticulatus wrighti in the northeast, may transmit the infection; the susceptibility of the two former species has been confirmed in the laboratory. The limitation in the size of snail habitats--which consist of wells, small canals, cisterns, small swamps, interrupted streams, and ponds--creates a special type of transmission which can be defined as "oasis transmission," making control of the disease both simple and practical.

Schistosomiasis in Antiquity

Abstract: INTODUCF1ON SCHISTOSOMES that infect domestic animals are of great economic importance, and may even cause death in cattle and sheep.' These parasites may also at times infest man, the most important of the several species being Schistosoma haematobium and Schistosoma mansoni. They are the subject of the present discussion. Both these parasites have a complicated, but similar, life cycle. Mature adult male and female schistosomes inhabit the small mesenteric or pelvic veins of man, the definitive host. After fertilization, the eggs are eventually extruded into the urinary tract or the rectum, causing haemorrhage from these sites. In general, infection by S. haematobium tends to localize in the genito-urinary system, whereas infection by S. mansoni is more likely to be found in the rectum. Their mature eggs are, therefore, found either in the urine or faeces, or in the walls of the bladder or rectum. Both eggs and schistosomes may, however, be in aberrant sites, such as the internal viscera or in the superficial tissues.2 On discharge from the body, the eggs hatch out in fresh water, and the free-swimming miracidia infest snails ofthe family Physidae or Bulinidae for S. haematobium, and of the family Planorbidae for S. mansoni infections. These multiply asexually within the visceral mass of the snail, the alternative host, and when conditions are suitable, free-swimming larval forms, cercariae, escape into the water, penetrate the skin of the definitive host, man, and become immature schistosomes. Eventually, after passing through the lungs, they migrate to the venules of the pelvis or mesentery, where they mature in situ and lay eggs intravascularly, thus repeating their life cycle. Natural infection by S. haematobium is restricted to primates, and only five cases occurring among monkeys and baboons have so far been discovered in East and West Africa;3 it appears to be primarily an intestinal disease in monkey hosts.4 On *P. B. Adamson, M.D., D.T.M. & H., Beckwith House Farm, Beckwith, Harrogate, North Yorkshire HG3 1QQ.

Acquired resistance to Schistosoma haematobium in the baboon (Papio anubis) after cercarial exposure and adult worm transplantation.

Abstract: Observations were made on the development of acquired resistance to Schistosoma haematobium in the baboon following immunization with cercariae by the percutaneous route and by the transplantation of adult worms into the mesenteric veins. In the first experiment six baboons were immunized with 1000 S. haematobium cercariae given percutaneously. They were challenged with 10 000 cercariae given 73 weeks later and the results were compared with a similar infection in non-immunized animals. The results showed that the baboon can develop a strong resistance to reinfection with S. haematobium. The manifestations of the immunity were (i) the absence of any increase in egg output after challenge (ii) the substantially lower level of adult worms and eggs in the tissues of the immunized baboons compared with the challenge control animals (iii) a reduction in the egg laying capacity of the residual worms and (iv) the virtual absence of gross pathology and the mild lesions seen in the tissue sections of all the immunized animals. The depression in egg laying of the worms was confirmed by transplanting them into non-immune baboons. This experiment indicated that the non-egg-laying worms in the immune baboons were not irreversibly damaged since they survived, some even migrating to the vesical and ureteric vessels, and egg-laying was rapidly resumed after transplantation. A further experiment was designed to see if a similar degree of immunity could be produced by an adult worm infection without previous exposure to cercariae or schistosomula. The immunization dose consisted of 50-100 S. haematobium worm pairs which were transplanted into the mesenteric veins of each of six baboons and the animals were challenged percutaneously with 7000 cercariae 35-55 weeks later. There was little difference in the worm burdens of the immunized and control animals but the worms in the immunized baboons produced fewer eggs and the pathology seen in these animals was much milder than in the challenge control animals suggesting that some degree of resistance to reinfection was produced by the transplanted worms.

Culture of Schistosoma haematobium in vivo and in vitro.

Abstract: The maximum rate of development of Schistosoma haematobium in the hamster was determined by examination of the most advanced worms recovered at short intervals throughout the course of development. In culture S. haematobium developed at the same rate as in the hamster up to day 31 when pairing first occurs and male worms produce some spermatozoa. In vitro males formed some spermatozoa but pairing did not take place and, probably for this reason, females did not complete sexual maturation as occurs in the host between days 57-65. Somatic growth continued in vitro and at 70 days male worms had achieved almost the same length as in the hamster at this time. The culture medium, previously used for S. mansoni, consisted of equal volumes of serum and Earle's balanced saline with a final concentration of 0.25% lactalbumin hydrolysate, 100 units/ml penicillin, 100 mug/ml streptomycin and 1% rbc. The best culture results were obtained with one particular human serum; seven other human sera gave a wide range of growth support. The samples of baboon, rhesus monkey or foetal calf sera tested provided little or no growth support but prolonged survival was possible in all the sera.

Schistosomiasis and Carcinoma of the Bladder in Zambia

Abstract: Carcinoma of the bladder is the third most important malignancy seen in Zambia, accounting for nearly 9% of all malignancies seen in the Department of Pathology at the University of Zambia. A review of 217 cases of carcinoma of the bladder seen in the department over a 5-year period revealed a preponderance of well-differentiated squamous cell carcinoma (75%). Of the 217 cases, 65% had concomitant schistosomiasis. These tumours tended to occur in a younger age group than that reported from England and North America. The pattern of pathology conforms with that reported from other parts of Africa with hyperendemic and endemic schistosomiasis. The aetiological role of schistosomiasis in bladder cancer is critically examined.

Cross-immunity to Schistosoma mansoni and S. haematobium in the hamster.

Abstract: Hamsters (WO strain) with a primary infection of Schistosoma mansoni or S. haematobium rapidly developed immunity to homologous challenge judged by the lung recovery assay. Immunity was detected at 4–5 weeks and reached a plateau 6 weeks after infection. Using this information, hamsters with an 8-week primary infection with S. mansoni or S. haematobium were tested for resistance to homologous reinfection and resistance to a challenge with the other species of schistosome. Primary infection with S. mansoni or S. haematobium conferred a high level of immunity to reinfection with either species of schistosome judged by the perfusion assay, involving recovery of adult worms 6–10 weeks following challenge. Estimation of the level of immunity with the lung recovery assay, 5 days after challenge, indicated that immunity due to a primary infection with S.mansoni acted at or before migration of the challenge through the lungs but immunity stimulated by a primary S. haematobium infection was only partially effective at the lung stage and substantial destruction of challenging organisms occurred at a later stage of development. Antibodies in immune sera of hamsters with a primary S. mansoni or S. haematobium infection were shown to bind to common antigens on the surface of young schistosomula of either species by u.v. microscopy using as detecting agent a fluorescein-labelled rabbit antiserum directed against hamster globulins.

Cutaneous ectopic schistosomiasis.

Abstract: Two cases of cutaneous schistosomiasis due to ectopic ova have recently been seen. Both patients presented with abdominal papular lesions, which were found on biopsy to contain schistosoma ova. To reach these abdominal sites mature worms probably migrate from the portal circulation to the paraumbilical veins, where they anastomose with veins of the caval system.

The use of a molluscicide in conjunction with chemotherapy to control Schistosoma haematobium at the Barombi Lake foci in Cameroon. III. Conclusions and costs.

Abstract: Although Frescon successfully controlled snails on the margins of the Barombi lakes, and although the continuation of niridazole and Frescon control reduced transmission of S. haematobium very considerably, practical difficulties, which are discussed, rendered the twin goals of snail- and parasite-eradication impossible to achieve. The "break-point" in transmission of S. haematobium appears to lie so low as to be practically synonymous with total eradication. Control operations would thus have had to be maintained indefinitely in order to avoid a rapid return to the pre-control situation. The cost of the control element in this combined chemotherapeutic and molluscicidal research project, at 2 lacustrine foci of S. haematobium transmission in the United Republic of Cameroon, was 9 to 10 U.S. dollars per year per head of population protected. This sum is about three times the country's total estimated expenditure per head of population on all health and social services for the year 1974-1975. The high cost of such operations is only likely to be acceptable where schistosomiasis causes much ill-health and reduced economic productivity, and where tangible benefits may be expected from a reduction in the intensity of infections, short of eradication.

Intermediate host antigens associated with the cercariae of Schistosoma haematobium.

Abstract: Bulinus (Physopsis) africanus antigens were shown to be associated with the cercarial glycocalyx of Schistosoma haematobium using immunofluorescence and the Cercarienhullen Reaktion. It is proposed that this snail antigen may sensitise the definitive host and that resistance to further invasion by cercariae could be induced in this manner.

Proliferative Epithelial Lesions of the Urinary Bladder in Cynomolgus Monkeys (Macaca fascicularis) Infected with Schistosoma intercalatum

Abstract: Summary Five cynomolgus monkeys ( Macaca fascicularis ) were infected with Schistosoma intercalatum , a helminth that is morphologically similar to Schistosoma haematobium . Infections were readily established and remained active until the monkeys were sacrificed 21 to 84 weeks after exposure. Although the schistosomes were located predominantly in mesenteric and hepatic portal venules, schistosome eggs were found in the bladders of 3 monkeys. Nodules of atypical epithelial cells interpreted as superficially infiltrating undifferentiated bladder carcinomas were found in one monkey 23 weeks after infection. These sessile tumors differ strikingly from the well-differentiated, papillary transitional cell tumors previously reported from several species of experimental animals infected with S. haematobium . The tumors are also dissimilar to the squamous cell bladder tumors associated with S. haematobium infection in man but may nonetheless be useful for investigations of schistosomal bladder cancer.

Schistosomiasis and carcinoma of the bladder: a critical appraisal of causal relationship.

Abstract: The pathology of 154 cases of carcinoma of the urinary bladder diagnosed in surgical specimens in Ibadan is reviewed. Schistosoma haematobium-infections are found in association with all varieties of urothelial carcinoma. The majority of tumours in this and previously reported series from bilharzial and nonbilharzial underdeveloped regions presented in advanced stages. It is suggested that the preponderance of squamous cell carcinoma in these regions is a reflection of late clinical presentation. The evidence so far presented to support a causal relationship between schistosomiasis and carcinoma of the bladder is reviewed. It is concluded that such relationship is probably not true.

Absence of schistosomal glomerulopathy in Schistosoma haematobium infection in man

Abstract: Kidneys were studied by light microscopy in 246 consecutive autopsies in Cairo, Egypt. Glomerulonephritis was not related to the presence or intensity of either S. haematobium or S. mansoni infection, and mesangial thickening and proliferation were also unrelated to schistosome infection. Acute and chronic pyelonephritis were also unrelated to the presence of schistosome infection.

A demonstration of the presence of anti-snail antibodies in individuals infected with Schistosoma haematobium.

Abstract: An extract of the snail Bulinus (Physopsis) africanus, the intermediate host of Schistosoma haematobium, was used as the antigen in haemagglutination tests in a survey of the prevalence of anti-snail antibodies in various population groups It was found that sera from known bilharzia-infected individuals and randomly selected individuals from bilharzia endemic areas had significantly higher incidences as well as higher titres of antibodies to this snail antigen than non-infected individuals and individuals from non-endemic areas

The use of a molluscicide in conjunction with chemotherapy to control Schistosoma haematobium at the Barombi Lake foci in Cameroon. II. Urinary examination methods, the use of niridazole to attack the parasite in man, and the effect on transmission from man to snail.

Abstract: The use of niridazole, in conjunction with snail control, in an attempt to control the transmission of Schistosoma haematobium at 2 Cameroon crater-lake villages is described. Quantitative examinations of urines for S. haematobium eggs were made on the whole population before control began, at intervals during the maintenance of control, and again after control ceased. The methods and difficulties are described, and their accuracy is discussed. After each examination all accessible egg-passers were treated or re-treated with niridazole. The drug was well tolerated and effective. Most treated patients ceased to pass live eggs, and most of those who later became positive again were thought to represent reinfections rather than relapses. During the maintenance of snail control, niridazole treatment of the 'whole' community reduced the total load of S. haematobium eggs passed to less than 1 per cent of the pre-control figure; and repeated subsequent treatments maintained a level of the same order. Despite this, there remained at different times 0.6-50.9 per cent of persons passing small quantities of live eggs, and these were an important source of continuing transmission. The possibility that more than one strain of S. haematobium was involved is discussed. An index of transmission from man to snail is proposed and discussed in relation to determining the level of the "break-point" in transmission. Although combined niridazole/molluscicide control reduced transmission from man to snail by about 3 log cycles, the "break-point", which is thought to lie 4 or more log-cycles lower, was not reached. When control was stopped, transmission built up again, with the prevalence rate in man rising more rapidly than the intensity of infections.

Stimulation of hamster and human lymphocyte cultures by soluble egg antigens (SEA) of Schistosoma haematobium and S. mansoni.

Abstract: Soluble egg and adult worm antigen preparations of Schistosoma haematobium and S. mansoni were tested in hamster and human lymphocyte cultures. Primed lymphocytes from infected donors showed a marked blastogenic response to the homologous antigens. A cross-reactivity to the heterologous antigens was seen especially in S. mansoni infected hamsters.

Experimental Bilharzial Bladder Cancer: Tryptophan Metabolism in Nonhuman Primates Experimentally Infected With Schistosoma haematobium

Abstract: A nonhuman primate species infected with Schistosoma haematobium provided a model system for controlled studies on biharzial bladder cancer. Urinary excretion of tryptophan metabolites by capuchin monkeys (Cebus apella) was similar to that of humans when expressed per g creatinine. Liver tryptophan oxygenase activity of the capuchin monkeys was comparable to that of humans. Excretion of 3-hydroxykynurenine and 3-hydroxyanthranilic acid was elevated above control levels in capuchin monkeys infected experimentally with S. haematobium. The capuchin-S. haematobium system closely resembles the human biharziasis system and offers a reproducible laboratory model system for the controlled study of the parasitology, pathogenesis, and biochemistry of biharzial bladder cancer.

A comparative study of the death of schistosomula of Schistosoma haematobium and Schistosoma mansoni in the skin of mice and hamsters.

Abstract: This study shows that some cercariae of S. haematobium and S. mansoni die during penetration of mouse or hamster skin. Approximately 30-38% of cercariae of both species die in mouse skin and 14-16% die in hamster skin. The greater number of cercariae which die in the skin of mice seems to account for the higher yield of adult worms recovered in hamsters. Adult worm recoveries from animals infected with S. haematobium were, however, only about half the worm recoveries from hosts infected with S. mansoni.

Schistosomiasis in the Gorgol Valley of Mauritania.

Abstract: Schistosomiasis may be increasing in West Africa due to the development of water-resource projects which were given a strong impetus by the disastrous Sahelian drought. This report concerns the existing epidemiology of schistosomiasis in West Africa for the Fourth Region of Mauritania, along the Gorgol River. In this area two reservoirs are proposed, to supply a new rice irrigation system. During May and November 1974, field surveys were made to determine the prevalence and intensity of schistosomiasis, and the relevant species of snails. The surveys were made as a basis for designing the irrigation systems to minimize transmission. The only snails found in the area were two species of Bulinus; therefore, the human population was tested for Schistosoma haematobium. A high prevalence of schistosomiasis was found in M'Bout, the town nearest the proposed reservoir at Foum Gleita. Prevalence rates were lowest in Kaedi near the confluence of the Gorgol and Senegal rivers. During the period between the first and second survey the incidence rate among children in M'Bout became very high (68%), probably because of increased water contact related to the rains that broke the long drought in August 1974.

A study of the relationship between temperature and the infectivity of Schistosoma mansoni and Schistosoma haematobium cercariae.

Abstract: It was shown that maintenance of cercariae of S. mansoni and S. haematobium at low (10degreesC) and high temperatures (40degreesC) markedly increased their mortality during penetration of mammalian host skin. These increased losses in the skin accounted for the known decrease in infectivity, as measured by adult worm recovery, of cercariae kept at low or high temperatures.

Some observations on the relationship of Schistosoma haematobium with its intermediate host.

Abstract: This paper concerns the relationships between miracidia of Schistosoma haematobium from Aden and various species of the Bulinus complex. It includes evidence on penetration and further development within the snail as revealed in serial sections.