Implication of Papio anubis in the transmission of intestinal schistosomiasis in three new foci in Kime area, Ethiopia

Epidemiological studies were conducted in the Lake Langano area in the Rift Valley of Ethiopia to determine the occurrence of schistosomiasis and assess factors involved in its transmission. Microscopic examination of faecal specimens from free ranging Papio anubis (anubis baboon) troops from Bishan Gari and Burka Dita forest reserves revealed Schistosoma mansoni eggs with a prevalence of 12.1% (11/91) and 26.2%(34/130), respectively. The eggs were viable as confirmed by miracidial hatching and infectivity tests. Out of the total 12 communities (three schools, five villages and one herdsmen community) surveyed for schistosomiasis around Lake Langano, individuals excreting S. mansoni eggs were found in nine communities with prevalence of infection ranging from 1.4 to 43%. The intensity of infection ranged from 24 EPG (eggs per gram of faeces) to 243 EPG. Excretion of viable eggs by the baboons indicate that they play a role in maintenance of S. mansoni infection in the locality. The detection of S. mansoni eggs in young children, collection of cercarial-infected Biomphalaria pfeifferi in water bodies, and establishment of S. mansoni infection in lab-bred mice have confirmed establishment of transmission foci in Kime area, south-east of Lake Langano. However, the lake itself does not seem to support transmission of schistosomiasis since no snails were found along the shore of the Lake. Further investigations are indicated to fully elucidate the role baboons play in the epidemiology of schistosomiasis in the Rift Valley of Ethiopia. The risk of introduction of water-based development projects in these new endemic foci in relation to S. mansoni infection in the baboons is discussed.     

Production of monoclonal antibodies against target schistosomal antigen secreted in the urine of Schistosoma mansoni-infected patients

This study was undertaken to develop an immunodiagnostic test of active human schistosomiasis mansoni using a monoclonal antibody which targets urinary schistosomal antigen. Polyclonal antisera raised in rabbits against the processed urine of Schistosoma mansoni-infected patients showed very high and significant reactivity with ES product of ova compared with other different S. mansoni antigens. The monoclonal antibody (4.23) was reactive with repetitive epitopes of S. mansoni soluble egg antigen and ES product of ova with molecular mass range of 65–23 kDa and 80–23 kDa, respectively. It recognised different stages of the parasite life-cycle, with no cross reaction with Fasciola or hydatid antigen. MAbs were characterised by isotyping, immunoelectrophoresis, SDS–PAGE and the enzyme-linked immunoelectrotransfer blot technique, ELISA, and their recognition of carbohydrate or protein antigenic epitopes by periodate oxidation and trichloroacetic acid treatment of the antigen. It was used for detection of circulating schistosomal antigen in an antigen capture antibody sandwich ELISA on sera and urines of 58 S. mansoni-infected patients, 17 S. haematobium-infected patients, 15 parasite-free negative healthy controls and sera from 13 schistosomiasis-free patients harbouring Fasciola or hydatid infections. The percentage sensitivity of the assay in the serum of S. mansoni-infected patients was 98.4% and in urine 94.8%. A positive correlation was found between the number of faecal S. mansoni eggs and the circulating antigen, both in serum and in urine. Antigen circulating in urine correlated with that in the sera of S. mansoni patients. These data provide a sensitive and non-invasive method almost comparable with the use of sera for immunodiagnosis of schistosomiasis and an indirect way to reflect the intensity of infection. Australian Society for Parasitology.     

Cloning and partial nucleotide sequence of Schistosoma japonicum paramyosin: a potential vaccine candidate against schistosomiasis.

, , , and 1992. Cloning and partial nucleotide sequence of Schistosoma japonicum paramyosin: a potential vaccine candidate against schistosomiasis. International Journal for Parasitology 22: 1187–1191. Paramyosin from the blood fluke, Schistosoma mansoni, has shown promise as a vaccine candidate for schistosomiasis mansoni. Here we report the cloning and partial nucleotide sequence of a cDNA encoding paramyosin from the related human parasite, Schistosoma japonicum. Affinity purified antibodies to this clone recognized a S. japonicum antigen of molecular weight 97 kDa, equivalent to the reported size of S. mansoni paramyosin. Alignment of the cDNA sequence with that of S. mansoni paramyosin revealed 90% identity. Comparison of the predicted amino acid sequences revealed 95% identity. Although these two parasites differ in many characteristics, the substantial homology demonstrated here between S. mansoni and S. japonicum paramyosin could have important implications for the development of a S. japonicum vaccine.     

Serological differentiation of acute and chronic schistosomiasis using Schistosoma mansoni recombinant protein RP26

We obtained a recombinant protein encoded by Schistosoma mansoni gene which was able to differentiate acute from chronic schistosomiasis when applied as antigen in enzyme-linked immunosorbent assay (ELISA). A cDNA clone encoding a 26 kDa recombinant protein (RP26) was selected by screening of an adult worm S. mansoni λZAP expression library with rabbit sera produced against PIII, an adult worm protein fraction already known to possess protective and immunomodulating effects. The clone cDNA presented 99% identity with S. mansoni Sm22.3 gene. We assayed IgG reactivity of sera from 18 patients with acute, 25 patients with chronic S. mansoni infection and 20 uninfected donors with RP26 in ELISA. Our results showed that 89% of sera were positive in acute schistosomiasis group, and only 26% in chronic group, without false-positive reactions in uninfected group. In mice the immune response to RP26 increased up to week 9 after infection and then diminished. We proposed that production of antibodies binding to RP26 stopped at the chronic stage of disease. The testing of sera from eight other parasitic infections with RP26 revealed no positive reactions in majority of sera. However, we observed low positive reaction in sera from 20% of leishmaniasis patients. Our results indicate that a recombinant protein RP26 can be used as immunodiagnostic reagent for detection of acute phase of schistosomiasis mansoni.     

Specificity of natural resistance to trematode infections in Biomphalaria glabrata

The 10-R2 strain of Biomphalaria glabrata was strongly resistant to various strains of Schistosoma mansoni in its laboratory of origin (NIH) and to three strains of S. mansoni we tested against it. However, subsequent development of three inbred lines of B. glabrata 10-R2 snails, separately maintained in our San Francisco laboratory, showed slight loss of resistance in one colony, very much less resistance (or partial susceptibility) in another, and retention of the original resistance in a third to the Puerto Rico (PR-1) strain of S. mansoni. No selection for resistance to infection was involved in the breeding protocol for these 10-R2 lines, so the changes were apparently random ones that became established in the separate inbred substrains. In spite of their changed response to the PR-1 strain of S. mansoni, all three 10-R2 substrains retained only slightly diminished resistance to S. mansoni Lc-1 strain and an essentially undiminished resistance to irradiated Echinostoma lindoense, E. paraensei and E. liei sporocysts. This suggests that natural resistance to S. mansoni PR-1 in B. glabrata is specific, a response that differs from the host response to either S. mansoni Lc-1 or to the echinostomes.     

Mechanisms of resistance to S. mansoni infection: the rat model

Human schistosomiasis is associated with IgE and eosinophilia, feature of a type 2 response. In experimental investigations, murine model has been widely used in order to dissect the immune responses involved in the expression of protective immunity or disease in Schistosoma mansoni infection. Collectively, observations made in this model and in humans demonstrated a strong contrast since a Th2 response in infected mice is involved in the expression of pathology, however, in infected humans the same type of response is rather beneficial for the host. This review will consider the relevance of extrapolating studies of immune responses from experimentally infected rats a semi-permissive host, to studies on S. mansoni infected humans.     

Capacity of irradiated echinostome sporocysts to protect Schistosoma mansoni in resistant Biomphalaria glabrata

Three closely related species of Echinostoma flukes each has a distinctive pattern of protection of Schistosoma mansoni in schistosome-resistant Biomphalaria glabrata host snails. Protection of developing S. mansoni by irradiated E. paraensei sporocysts in the schistosome-resistant snail host was strong; protection induced by irradiated E. lindoense and E. liei sporocysts was weak or not measurable. The capacity of irradiated E. paraensei sporocysts to interfere with the host's innate anti-schistosome response also differed between strains of B. glabrata. Protection of S. mansoni strain Lc-1 was greater in B. glabrata strain 10-R2 than it was in strain M-RLc snails. Irradiated E. paraensei sporocysts also induced a different response to the two schistosome strains in a single host strain. Irradiated E. paraensei sporocysts induced in B. glabrata 10-R2 snails a stronger protection of S. mansoni strain PR-1 than of strain Lc-1. Exposure of each snail to the irradiated E. paraensei miracidia usually protected the following challenge schistosome infection better when 30 rather than 10 irradiated echinostome miracidia were used.     

Cross-reactivity between Necator americanus and Schistosoma mansoni in mice.

, , and 1992. Cross-reactivity between Necator americanns and Schistosoma mansoni in mice. International Journal for Parasitology 22: 1143–1149. Poly-parasitism is common in endemic communities and reactivity of sera from hookworm-infected patients against schistosomular antigens has been reported. Protective cross-immunity between N. americanus and S. mansoni was investigated in NIH and BALB/c mice. Protective resistance to homologous challenge with both parasites was confirmed in this model, however, functional immunity to heterologous challenge was not demonstrated. Sera from animals which had received homologous challenge with N americanus and from hookworm-infected mice, which had previously been exposed to radiation-attenuated S. mansoni, exhibited an enhanced IgGAM response to infective stage N. americanus somatic antigens. The implications of these results with respect to serodiagnosis are discussed.     

Control of Schistosoma mansoni transmission: Strategy for using molluscicides on St. Lucia

Control of Schistosoma mansoni transmission: strategy for using molluscicides on St. Lucia. International Journal for Parasitology 3: 795–801. A simplified model, based on previous field studies, is described to summarize the transmission of Schistosoma mansoni on the West Indian Island of St. Lucia by the snail Biomphalaria glabrata. Snail populations in static habitats play little part in transmission but form a reservoir of snails which invade flowing habitats in the dry season. These flowing habitat populations account for most of the transmission: preventing their establishment should greatly reduce transmission. The reasons why a single molluscicide treatment of the static habitat populations is unlikely to achieve this result are discussed and an alternative, practical strategy is suggested. An initial intensive mollusciciding followed by surveillance, coupled with focal mollusciciding of surviving snail colonies, should suppress the static habitat populations sufficiently to prevent the invasion of the flowing habitats. This practical strategy should have a reasonable chance of reducing S. mansoni transmission judging by the results of similar control schemes using molluscicides.     

Host reactions in Biomphalaria glabrata to Schistosoma mansoni miracidia, involving variations in parasite strains, numbers and sequence of exposures

M-line Biomphalaria glabrata snails are susceptible to Puerto Rican (PR-1) strain of Schistosoma mansoni, but are resistant to a St. Lucian (LC-1) strain. 10-R2 B. glabrata snails are resistant to both strains of S. mansoni. When 10-R2 snails were exposed repeatedly to PR-1 S. mansoni miracidia for 5 consecutive days, all of the sporocysts were encapsulated and destroyed by the snails. Thirty-four per cent of sporocysts examined in M-line snails with similar exposures were also degraded. In double concurrent infections of M-line B. glabrata with [³H]leucine-labeled and unlabeled PR-1 and Lc-1 S. mansoni, the incompatible Lc-1 miracidia were selectively attacked and destroyed. This destruction occurred irrespective of the sequence of exposure of the 2 strains of miracidia, and whether or not the miracidia were labeled. Successful superinfection of M-line B. glabrata with homologous S. mansoni miracidia was obtained at least 4 days after the primary exposure to the miracidia.     

Imaging diagnosis of schistosomiasis japonica--the use in Japan and application for field study in the present endemic area

For detecting lesions-related schistosomiasis japonica, X-rays, scintillation scanning, ultrasonography (US), computed tomography (CT), magnetic resonance (MR) and endoscopic examinations with biopsies have been used in Japan. Liver fibrosis and calcified changes are detected by US and CT. Most of the lesions that are detected by endoscopic examinations are due to deposited ova of Schistosoma japonicum. Portal hypertension is detected by US, CT and gastroscopic examination. Because schistosome infection decreased rapidly in Japan, most of the studies on imaging diagnosis were performed on chronic lesions or sequelae of schistosomiasis. Most of the techniques were used on admitted patients in well-equipped hospitals. US was introduced in the 1970s as a safe, rapid, non-invasive and inexpensive technique and has been used for diagnosis in hospitals and screening in the fields. As a typical US image of the liver, septal formation by high echogenic bands like mosaic was described, and this network pattern was reported in the other endemic countries; China and Philippines. As an appropriate technique, US has been broadly used in developing countries. Not only for diagnosis in a hospital, but also for monitoring changes of morbidity, US is used in the community level. Network pattern related to the severity of S. japonicum infection, has not been described in S. mansoni or S. haematobium infection. Appearance of network pattern depends on pathological changes such as periportal fibrosis, postnecrotic fibrosis and calcified ova. For advanced studies on morbidity of schistosomiasis japonica, further research on pathological basis of network pattern and standardization of US diagnosis are necessary.     

Schistosoma mansoni and Schistosoma japonicum: Utilization of amino acids

, , and 1972. Schistosoma mansoni and Schistosoma japonicum: utilization of amino acids. International Journal for Parasitology 2: 425–430. The production of ¹⁴CO₂ from 12 labeled amino acids by S. mansoni and S. japonicum was studied. No ¹⁴CO₂ was detected from incubations with glycine, isoleucine, leucine, lysine or phenylalanine. Differences were found between sexes and/or species for the other amino acids studied. Species related differences included a greater rate of metabolism of glutamic and aspartic acid by S. mansoni than by S. japonicum. Proline and histidine were utilized by S. mansoni males and females, respectively. S. japonicum male worms did not utilize proline, while histidine was not utilized by the female of this species. Major sex related differences included greater ¹⁴CO₂ production from glutamic acid, aspartic acid and arginine by S. mansoni males than by females, and the utilization of histidine by male S. japonicum but not by females. Incubation in tyrosine resulted in the release of only small amounts of ¹⁴CO₂ by female worms of both species but no ¹⁴CO₂ production by male worms.     

Haemostatic abnormalities in hepatosplenic schistosomiasis mansoni

Hepatosplenic schistosomiasis is a complex immuno-regulatory disease and is major health problem in endemic countries. Acute bleeding is one of its most serious complications and often life-threatening. Clinical studies have demonstrated that the patients with hepatosplenic schistosomiasis are prone to develop complex haemostatic abnormalities that may be linked to the potential risk of bleeding from ruptured esophageal varices in these patients. The deficit in haemostatic parameters is more pronounced with the advancement of the disease and is maximal in the patients with experience of haematomesis. Evidences of enhanced generation of thrombin and plasmin indicate the presence of low-grade DIC in advanced hepatosplenic schistosomiasis, which is considered as a principal cause of haemostatic abnormalities in this endemic disease. Demonstration of procoagulant expression in peripheral blood monocytes of the patients and in the livers, spleens and intestines of S. mansoni-infected mice suggest their possible implication in the causation of DIC in S. mansoni infections. Moreover, because in vitro analysis indicates a participation of immune mechanisms in the localized procoagulant expression, it seems likely that the immune responses to schstosomes play a major role in the pathogenic mechanisms of haemostatic abnormalities in hepatosplenic schistosomiasis.     

Ranging behavior,group size and behavioral flexibility in Ethiopian hamadryas baboons (Papio hamadryas hamadryas)

This study reports group size, home range size, daily path lengths, seasonal effects on ranging behavior and qualitative information on diet for a population of hamadryas baboons inhabiting the lowlands of the northern Rift Valley in central Ethiopia. The minimum home range size and daily path length for this population are similar to those reported for other populations of hamadryas baboons in Ethiopia and Saudi Arabia. Group sizes, however, are much larger than those in most other hamadryas populations for which published data are available. The large group sizes in this area may be related to the abundance of one food resource in particular, doum palm nuts. Overall, this study suggests that hamadryas baboons may be more flexible in some aspects of their behavioral ecology (e.g. group size) than in others (e.g. ranging behavior).     

ITS2 ribosomal RNA indicates Schistosoma hippopotami is a distinct species

The internal transcribed spacer region of the ribosomal RNA, ITS2, was sequenced from a singlé specimen of S. hippopotami collected from a pulmonary artery of the hippopotamus, Hippopotamus amphibius in South Africa. The nucleotide sequence was aligned with those of S. mansoni, S. rodhaini, S. haematobium, S. intercalatum, S. curassoni. S bovis and S. japonicum. Both maximum parsimony and genetic distance analyses were performed on these data sets. Using S. japonicum as outgroup to the African schistosomes, a single most-parsimonious tree was obtained of length 64 steps with a consistency index of 1. S. hippopotami was the sister-group to the remaining African species. This species has lateral-spined eggs and its basal position in the tree suggests that this condition is primitive and that terminal-spined eggs developed secondarily. Molecular data clearly show that S. hippopotami cannot be considered synonymous with S. mansoni. Assuming the hippopotamus is the normal host of S. hippopotami, phylogenetic analysis is consistent with an ancient association between schistosomes and ungulates.     

The miniature pig: a unique experimental model for Schistosoma japonicum infection

As part of a search for good animal models for human schistosomiasis, two miniature pigs of the CLAWN strain (C-1, C-2) were inoculated percutaneously with 200 Schistosoma japonicum cercariae of the Chinese strain, and the subsequent infection was monitored parasitologically, pathologically and serologically. Egg excretion into feces began at 5 weeks post-infection (p.i.) and became pronounced from 8 weeks to 17–20 weeks p.i. The average number of eggs in 1 g feces of each pig at the peak period between 8 and 20 weeks were 288 and 277, respectively. C-1 and C-2 were killed and perfused at 27 and 47 weeks p.i. and adult worm numbers recovered were 35 and 15, respectively. C-2 had at least four pairs of viable mature worms but no detectable fecal eggs for a month before perfusion, suggesting that any produced eggs were not excreted into the feces during this period. Egg deposits associated with inflammatory reactions were observed by histological examination of the liver, spleen, pancreas, mesenteric lymph nodes, lung, and small intestine. This suggests that reduced fecal excretion of eggs into the feces did not correlate to reduced parasite numbers in the chronic phase of schistosomiasis. This is the first report showing the miniature pig to be a potential model for human S. japonicum infection.     

Schistosoma mansoni encodes SMT3B and SMT3C molecules responsible for post-translational modification of cellular proteins

The sumoylation pathway is a post-translational modification of nuclear proteins widespread among several organisms. SMT3C is the main protein involved in this process and it is covalently conjugated to a diverse assortment of nuclear protein targets. To date, 3 SUMO paralogues (SMT3C, A/B) have been characterized in mammals and plants. In this work we characterized two SUMO related genes, named SMT3B and SMT3C throughout Schistosoma mansoni life cycle. The SmSMTB/C encodes for proteins sharing significant amino acid homology with SMT3. Phylogenetical analyses revealed that both SmSMT3B/C are distinct proteins. Additionally, SmSMT3B and C are expressed in cercariae, adult worms, eggs and schistosomula however SmSMT3C gene showed an expression level 7 to 9 fold higher than SmSMT3B in eggs, schistosomula and adult worms. The comparison between the SmSMT3C genomic and cDNA sequences established that the encoding sequence is interrupted by 3 introns of 70, 37 and 36 bp. Western Blot has shown SMT3 conjugates are present in nuclear and total protein fractions of adults and cercariae. Therefore our results suggest a functional sumoylation pathway, and the presence of two paralogues also suggests the specificity of substrates for SMT3 in S. mansoni.     

Schistosomiasis mansoni in areas of low transmission: epidemiological characterization of Venezuelan foci

Severe schistosomiasis is a rare event in Venezuela nowadays, after a successful national campaign by the Schistosomiasis Control Program. Unfortunately, this program has practically disappeared, and snail surveillance in field is not a priority, anymore. Thus, schistosomiasis has become a neglected disease in this country. However, surveys in different populations from the endemic area have shown particular epidemiological features described herein. In five communities we evaluated 2,175 persons and searched for the presence of Biomphalaria glabrata snails. Some markers were used for classifying schistosomiasis foci: mean age of the persons with Schistosoma mansoni eggs in the stools, serological tests, presence of B. glabrata snails, and intensity of infection. Places without B. glabrata snails and with few schistosomiasis cases were defined as "past transmission sites"; a site with abundant snails but few cases was defined as "potential risk"; "new transmission" foci were characterized by the presence of infected snails and young people passing eggs in the stools. A "re-emergent" focus has shared these last features, showing in addition a place where schistosomiasis had been reported before. Recent evidences of active transmission with the increasing dispersion of B. glabrata snails, point out the necessity for the re-establishment of the Schistosomiasis Control Program in Venezuela.