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PubMed1979

Studies of the relationship between Schistosoma and their intermediate hosts. III. The genus Biomphalaria and Schistosoma mansoni from Egypt, Kenya, Sudan, Uganda, West Indies (St. Lucia) and Zaire (two different strains: Katanga and Kinshasa).

The compatibility between strains of Schistosoma mansoni from Egypt, Kenya, Sudan, Uganda, the West Indies, and Zaire (two strains which came from Katanga and from Kinshasa), and various species and strains of Biomphalaria, i.e. Biomphalaria pfeifferi, B. alexandrina, B. glabrata and B. camerunensis was investigated. Data as mortality, rate of infection of the surviving snails, duration of infection, cercarial production per day per positive snail, etc., were observed. The main emphasis was placed on determining the total cercarial production per 100 exposed snails for each snail population. It was possible to infect all the tested populations of B pfeifferi with the various strains of S. mansoni, but the observation as e.g. TCP/100 exposed snails varied greatly according to the population of snail and the strain of S. mansoni. The results for the remaining species of Biomphalaria varied greatly, depending on the combination, e.g. B. alexandrina was only susceptible to the local S. mansoni from Egypt. The highest TCP/100 exposed snails was more than 1 million for the strains of S. mansoni from Egypt, Kenya and the West Indies in B. alexandrina, B. pfeifferi and B. glabrata, respectively. The next group, with a TCP/100 exposed snails on 7--800 000 consists of S. mansoni from Sudan, Uganda and Zaire (Katanga) all in B. pfeifferi. The last tested strain of S. mansoni, Zaire (Kinshasa) yielded a cercarial production on 500 000 per 100 exposed snails in B. pfeifferi and B. camerunensis. The shortest prepatent period, 19 days, was observed for S. mansoni from Kinshasa, Zaire, in B. camerunensis, and the longest prepatent period, 25 days, was found for strains from Egypt and from the West Indies in B. alexandrina and B. glabrata, respectively. In general, a very long duration of infection, lasting up to 200 days, was observed.

Animals↗
PubMed1979

Studies of the relationships between Schistosoma and their intermediate hosts. IV. The genus Bulinus and Schistosoma bovis from Morocco.

Schistosoma bovis from Morocco was used in infection experiments with several populations of Bulinus truncatus. The snails from Libya, Malawi, Morocco and Senegal were very compatible with the schistosome since the infection rates were approximately 90%, the mortality was low, and a very high production of cercariae, approximately 1.2 million per 100 exposed snails, was observed. Only a very few B. truncatus (2n = 36) from Rhodesia became infected. B. permembranaceus and B. forskalii were refractory.

Animals↗
PubMed2002

A model to explain the replacement of Schistosoma intercalatum by Schistosoma haematobium and the hybrid S. intercalatum x S. haematobium in areas of sympatry.

Numerous hypotheses have been postulated to explain the rapidly changing parasitological situation in Loum, Cameroon as a result of the interaction between Schistosoma haematobium and S. intercalatum. The aim of this study is to test the various hypotheses using a simple mathematical model, incorporating equal and unequal sex ratios of adult schistosomes, recombinations, and levels of compatibility with the intermediate molluscan hosts, B. forskalii and B. truncatus. The model assuming an equal sex ratio does not fit with the existing field data in that it predicts a continued presence of S. intercalatum, S. haematobium and the hybrids. The model assuming a sex bias in favour of males, which reflects the situation usually observed in schistosome populations, predicts the loss S. intercalatum which indeed concurs with the most recent data.

Animals↗
PubMed2002

Susceptibility of freshwater snails to the amphistome Calicophoron microbothrium and the influence of the species on susceptibility of Bulinus tropicus to Schistosoma haematobium and Schistosoma mattheei infections.

The susceptibility of Bulinus tropicus, B. globosus, Biomphalana pfeifferi, Lymnaea natalensis, and Melanoides tuberculata to Calicophoron microbothrium was examined. Bulinus tropicus had the highest prevalence (65.0%), followed by B. pfeifferi (37.5%), B. globosus (6.8%), and M. tuberculata (5.9%). Lymnaea natalensis was refractory to infection. Bulinus tropicus snails infected with C. microbothrium alone or coinfected with either Schistosoma haematobium or S. mattheei 0, 7, 14, and 21 days after exposure to C. microbothrium produced C. microbothrium cercariae only.

Animals↗
PubMed1977

Comparative effects of hycanthone in Schistosoma mansoni and Schistosoma japonicum.

After in vitro hycanthone treatment followed by a 20-hour incubation in drug-free medium, Schistosoma mansoni were still resistant to labeling by a fluorescent analog of acetylcholine. S. japonicum, in contrast with the hycanthone sensitive species, showed prompt reversal of the blocking effects of hycanthone on fluorescent labeling. This finding suggests that differences in the reversibility of hycanthone may correlate with the usefulness of the drug in the therapy of schistosome infections by different species of parasites. Scanning electron microscopy has been used to demonstrate that hycanthone treatment causes degeneration of the integument of S. mansoni, but not S. japonicum, over a period of few days after in vivo exposure to hycanthone. The mechanism by which hycanthone causes this effect is not known.

Acetylcholine↗
PubMed1991

[Studies on the strain differences of Schistosoma japonicum in the mainland of China. IV. Fuzzy cluster analysis on some biological characters of different isolates of Schistosoma japonicum].

In this paper, a computerized numerical systematics was used to analyse the 5 different isolates of Schistosoma japonicum in the mainland of China by means of fuzzy clustering method with 32 quantitative data of each isolate about the morphological and biological characters. A dendrogram of the 5 isolates of S. japonicum was constructed on the basis of similarity coefficients as shown. The phylogenetic relationships revealed by the present study show that the two isolates of Anhui and Hubei get together firstly in one group, then the isolates of both Yunnan and Guangxi gather in another group, while the Sichuan isolate is closely related to the group of Anhui-Hubei isolates, not to the Yunnan ones, although both Sichuan and Yunnan isolates were in the southwest China.

Animals↗
PubMed1987

Interference with homologous immunity and faecal egg excretion in Schistosoma infections in mice concurrently infected with Trypanosoma brucei and Schistosoma mansoni.

The effects of the blood protozoan, Trypanosoma brucei, was assessed on the homologous immunity to Schistosoma mansoni infection and the distribution of S. mansoni eggs in the tissues and faeces of dually infected mice. The trypanosome infection reduced the homologous protection induced by a primary S. mansoni infection against a challenge infection and the faecal excretion of eggs during the primary schistosome infection. The findings are discussed in relation to the immunosuppressive action of Trypanosoma infection.

Animals↗
PubMed1998

A simple method of preparing clean intact granulomas and granuloma cells from livers of definitive hosts infected with either Schistosoma mansoni or Schistosoma japonicum.

The drawback of existing techniques for obtaining intact granulomas and granuloma cells have been, (1) lack of clean intact granulomas without adhering liver tissues, (2) isolating inadequate numbers of clean intact granulomas, and (3) obtaining low numbers of viable granuloma cells from the granulomas. This work aims at developing a method which eliminates these problems. C57B1/6 mice and baboons have been utilized as definitive hosts. Major emphasis has been on Schistosoma mansoni liver egg granuloma, though some work was carried out using S. japonicum. The work demonstrates that it is possible to obtain enough clean liver granulomas and large numbers of granuloma cells from animals with schistosome infection by using two stages of digestion with collagenase. However, one needs to adjust the concentration of collagenase and also the periods of incubation, depending on the parasite and the host species.

Animals↗
PubMed1976

Preliminary observations on the distribution, definitive hosts and possible relation with other schistosomes, of Schistosoma margrebowiei, Le Roux, 1933 and Schistosoma leiperi, Le Roux, 1955.

In attempting to define the south western limits of the distribution of Schistosoma margrebowiei and S. leiperi and investigating their apparent limited distribution in relation to their snail hosts it was found that there was little overlap in the distribution of S. margrebowiei and S. leiperi and that of the human parasites S. haematobium and S. mansoni, and no overlap with S. mattheei within the area surveyed. It is suggested that the presence of either or both lechwe schistosomes prevented the development of the human parasites and in addition, prevented the development of S. mattheei in certain areas inhabited or surrounded by certain Kobus spp. The restricted distribution of S. margrebowiei and S. leiperi was thought to be due to the restricted distribution of their main definitive hosts Kobus leche and K. vardoni; the poor host susceptibility of cat and possibly Syncerus caffer; and the likelihood of most other "common" game being unable to maintain the parasites indefinitely outside the confines of lechwe and puku distribution in southern Africa.

Angola↗
PubMed1988

Praziquantel and oltipraz: the treatment of schoolchildren infected with Schistosoma mansoni and/or Schistosoma haematobium in Gezira, Sudan.

Of 111 schoolchildren--all of whom were infected with Schistosoma mansoni and 97 of whom were also infected with S. haematobium--54 were treated with Praziquantel (2 x 20 mg kg-1) and 57 with Oltipraz (2 x 15 mg kg-1). There was no apparent difference between the efficacy of the two drugs. Follow-up studies over the following 12 months indicated that mass chemotherapy of schoolchildren can be expected to reduce the egg output of those treated by almost 100%, but that, unless there is some break in transmission, the egg output may well be as high after 12 months as it was before treatment--at least in the boys. After a round of chemotherapy, retreatment of school-aged boys in an area where transmission is heavy will be necessary six to 12 months later.

Child↗
PubMed1990

Further studies on variable resistance of 129/J and C57BL/6 mice to infection with Schistosoma japonicum and Schistosoma mansoni.

Two mouse strains maintained in this laboratory (WEHI) are variably resistant to infection with Schistosoma japonicum and S. mansoni in that worms cannot be found in the liver and portal system in a high proportion (WEHI 129/J mice) or low proportion (C57BL/6 mice) some weeks after exposure to cercariae. Resistance can be as high as 100% in WEHI 129/J mice and is usually around 20% in C57BL/6 mice. The proportion of resistant mice closely parallels the proportion of mice that demonstrate a shunting of microbeads, injected into a mesenteric vein, from liver to lungs. This applies to F1 x WEHI 129/J backcross mice in which the data suggest oligogenic genetic effects although no evidence for a participation of MHC-linked genes in the phenomenon has emerged. 129/J mice derived from the Jackson Laboratory do not show a shunting of beads from the portal system to the lungs but their progeny bred at WEHI do. Germ-free WEHI 129/J mice resemble conventionally-maintained, SPF-derived WEHI 129/J mice in their variable resistance to schistosome infection. No satisfactory explantation for hepato-portal system peculiarities in WEHI 129/J and C57BL/6 mice can be advanced as yet and a possibility raised in this paper is a contribution from nutritional factors such as hypervitaminosis A superimposed on a genetic predisposition in these two related mouse strains.

Animals↗
PubMed2001

Human T- and B-cell responses to Schistosoma mansoni recombinant glyceraldehyde 3-phosphate dehydrogenase correlate with resistance to reinfection with S. mansoni or Schistosoma haematobium after chemotherapy.

Recently we reported that human T- and B-cell recognition of a 42-kDa protein (p42) in soluble extracts of adult Schistosoma mansoni worms correlates with resistance to reinfection with S. mansoni or S. haematobium. Amino acid microsequencing of p42 revealed that it consists predominantly of schistosome glyceraldehyde 3-phosphate dehydrogenase (SG3PDH). We have expressed SG3PDH in Escherichia coli and purified the recombinant protein in a soluble and enzymatically active form. Recombinant SG3PDH (rSG3PDH) reacted with human monospecific antibodies to p42. Lymphoproliferation and production of interleukin-4 and gamma interferon (IFN-gamma) after in vitro stimulation with rSG3PDH and serum isotype responses to rSG3PDH were examined in individuals with extremes of resistance and susceptibility to reinfection after treatment of previous S. mansoni or S. haematobium infection. Lymphoproliferation and IFN-gamma production in response to rSG3PDH and the presence of serum immunoglobulin G1 (IgG1), IgG3, and IgA antibodies to rSG3PDH generally characterized individuals who are resistant to reinfection after chemotherapy. The data indicate that T- and B-cell immune reactivity to rSG3PDH correlates with resistance to reinfection, confirming previous studies identifying SG3PDH as a target of protective immunity in humans, and suggest that SG3PDH should be investigated as a possible vaccine for human schistosomiasis.

Animals↗
PubMed1986

The effect of metrifonate in mixed Schistosoma haematobium and Schistosoma mansoni infections in humans.

In order to examine the effect of metrifonate, 156 patients with mixed Schistosoma haematobium and mansoni infection were randomly divided into three groups and treated with metrifonate (twice 10 mg/kg body weight), oxamniquine (60 mg/kg) and praziquantel (40 mg/kg), respectively. The output of S. haematobium and S. mansoni ova were quantitatively assessed in urine and stool. Application of metrifonate resulted in a similar reduction of S. haematobium and S. mansoni eggs in the urine, whereas no effect on egg excretion was observed in the stool irrespective of the parasite species. In contrast, oxamniquine influenced the output of S. mansoni ova in stool and urine, but showed no effect on S. haematobium egg excretion. praziquantel was equally effective against both parasite species. The chemotherapeutic effects were not of transient nature since the number of ova of both parasite species remained unchanged five months after treatment. The results clearly indicate that metrifonate acted exclusively on adult worms located in the perivesical plexus irrespective of the parasite species.

Adolescent↗
PubMed1993

Biology and pathology of Schistosoma mansoni and Schistosoma japonicum infections in several strains of nude mice.

Schistosoma mansoni and S. japonicum infections in nude mice (nu/nu) were compared with infections in nu/+ heterozygotes or intact mice. Seven to 12 weeks after exposure to S. mansoni, the responses of Swiss NCR, C3H, BALB/c and C57B1/6 nude mice did not differ substantially. Nude mice of all these strains showed minute granulomas around eggs in the liver and minimal hepatic fibrosis. Microvesicular and necrotizing changes in hepatocytes were similar in all mouse strains, and S. mansoni infections were frequently lethal to nude, but not to intact mice between the seventh and ninth weeks of infection. Nude mice that survived the ninth week of infection generally lived until the 12th week. The number of eggs per mature worm pair in the tissues of S. mansoni-infected nude mice was similar to the number in intact mice, but nude mice passed fewer eggs in the feces. Nude mice that received serum from infected intact mice excreted eggs in the stool in numbers equivalent to intact mice, but continued to form minute granulomas around S. mansoni eggs. Reconstitution with fetal thymus or with splenocytes from normal or S. mansoni-infected mice partially or completely restored hepatic granuloma size, granuloma eosinophils, hepatic fibrosis, and excretion of eggs in the feces. In contrast to S. mansoni infection, S. japonicum infections in nude mice did not cause necrosis of hepatocytes or excessive mortality, and S. japonicum eggs were passed in the feces in numbers equivalent to those passed by infected intact mice.

Animals↗
PubMed1993

Is Schistosoma mansoni replacing Schistosoma haematobium in the Fayoum?

Schistosoma mansoni is progressively replacing S. haematobium along the Nile River in Egypt. This change has occurred in the past 15-20 years following construction of the Aswan High Dam in the 1960s. The cause is a shift in relative abundance of the snail vectors Biomphalaria alexandrina and Bulinus truncatus. Biomphalaria is increasing while the latter has disappeared from a village in the Fayoum where formerly only schistosomiasis haematobia was endemic. A cross-sectional household survey in this village in 1991 showed the following prevalence values: S. mansoni, 22.3%; S. haematobium, 3.4%; and mixed infections, 2.8%. Only two children less than 10 years of age had S. haematobium infections. A review of the local Ministry of Health records showed that 1) both species were parasitologically diagnosed during the past 7.5 years, 2) Biomphalaria had been abundantly present in the local waterways for the past 10 years and has been found infected with S. mansoni since 1985, 3) Bulinus has not been detected in the local canals and drains since 1986 and the few found between 1981 and 1985 were not infected, and 4) Biomphalaria in this village and in two others in the Fayoum were believed infected by laborers from the Delta who helped build schools in 1984. This change in the distribution of schistosomiasis will impact upon public health and medical practice in Middle and Upper Egypt as it already has in Lower Egypt.

Adolescent↗