Patients with severe schistosomiasis mekongi morbidity demonstrating ongoing transmission in Southern Lao People's Democratic Republic.

Chronic infection with Schistosoma mekongi may result in severe hepatosplenic morbidity. We report on eight patients with severe morbidity due to S. mekongi infection. The patients were diagnosed, treated and followed-up between 2007 and 2010 in Khong district, Southern Lao People's Democratic Republic (Lao PDR), eight years after the end of a control intervention. S. mekongi control programmes aimed to prevent morbidity and mortality associated with infection. The patients were visited and interviewed annually. In addition, clinical and abdominal ultrasound examinations were performed and faecal and blood samples were examined. The patients' ages ranged from 6 to 66 years. Of the eight patients, three were children and five were adults. The four youngest patients (aged 6-27 years) significantly improved after praziquantel treatment. One patient (age 46 years) worsened between 2007 and 2010. Two patients died due to bleeding of the oesophageal varices. One patient was lost to follow-up. The leading clinical signs were ascites, splenomegaly, collateral veins on the abdomen and a poor general nutrition status. Ultrasonography disclosed advanced liver fibrosis patterns in all patients; in seven patients, fibrosis pattern E or F was revealed, as per the Niamey protocol (pattern A normal, pattern B to F pathological with increasing severity). Stool microscopy revealed that five patients were co-infected with hookworm and Opisthorchis viverrini. The youngest patient (aged 6 years) was born after the schistosomiasis control program had ended. From her severe morbidity, we can conclude that S. mekongi transmission was on-going in Khong district, and that even in areas with low S. mekongi transmission intensities, severe morbidity from schistosomiasis can develop quickly. Early diagnosis and treatment are imperative, and close monitoring is required.

Copro-PCR based detection of bovine schistosome infection in India.

Schistosomosis and amphistomosis are the two economically important and widely prevalent snail-borne trematode infections in grazing cattle of southern India. Acute infections are symptomatically similar and difficult to detect by routine microscopy for eggs. The present study was directed towards the development of a copro-polymerase chain reaction (copro-PCR) for detection of bovine schistosome species, using custom-designed primers targeting 18S and 28S ribosomal RNA as well as mitochondrial DNA. The study demonstrated the enhanced diagnostic specificity of mitochondrial DNA markers over ribosomal RNA genes as genus-specific probes to detect schistosomes. We developed a sensitive PCR assay using primers designed from mitochondrial DNA sequences targeting the partial rrnl (16S rRNA), tCys (transfer RNA for cysteine) and partial rrnS (12S rRNA) genes of Schistosoma spindale to specifically detect schistosome infection from faecal samples of naturally infected bovines. The salient findings of the work also throw light on to the high similarity of the ribosomal RNA gene sequences of schistosomes with those of Gastrothylax crumenifer and Fischoederius elongatus, the most prevalent pouched amphistomes of the region. Further investigation has to be directed towards unravelling the complete gene sequences of 18S and 28S ribosomal RNA as well as mitochondrial DNA sequences of amphistome isolates from India.

Schistosomiasis in pre-school-age children and their mothers in Chikhwawa district, Malawi with notes on characterization of schistosomes and snails.

BACKGROUND: To complement ongoing schistosomiasis control within national control programmes (NCPs) that administer praziquantel to school-age children, assessing the risk and extent of schistosomiasis in pre-school-age children (PSAC) is important. METHODS: In June 2012, schistosomiasis in Chikhwawa district, Malawi was assessed across 12 villages examining pre-school-age children (PSAC) and their mothers by serological and parasitological diagnosis, as supplemented with urine-antigen and questionnaire-interview methods. Urinary tract morbidity was inferred by haematuria and albuminuria assays. RESULTS: In total, 49.5% (CI95 42.6-56.4) of 208 PSAC and 94.5% (CI95 90.9-98.1) of 165 mothers were seropositive for schistosomiasis, in 2 villages seroprevalence exceeded 75% in PSAC. Egg-patent urogenital and intestinal schistosomiasis was observed; 17.7% (CI95 12.4-23.2) of PSAC and 45.1% (CI95 37.4-52.8) of mothers having active schistosomiasis by parasitological and urine-antigen testing combined. PSAC often had extensive daily water contact and many (~25%) had haematuria and albuminuria. As eggs with an atypical morphology of Schistosoma haematobium were observed, a general selection of schistosome eggs was characterized by DNA barcoding, finding Group I S. haematobium and Group IV and V S. mansoni. Malacological surveys encountered several populations of Bulinus globosus but failed to find Biomphalaria. CONCLUSIONS: Both PSAC and their mothers appear to be at significant risk of schistosomiasis and should be considered for treatment within the NCP of Malawi.

Estudo do efeito moluscicida de espécies vegetais em embriões e caramujos adultos de Biomphalaria glabrata SAY 1818 (Gastropoda, Planorbidae) / Investigation of the effects of plant species molluscicides on embryos and adult snails of the species Biomphalaria glabrata

A esquistossomose é uma doença parasitária causada por helmintos trematódeos do gênero Schistosoma, que tem o ser humano como hospedeiro definitivo e os planorbídeos do gêneroBiomphalaria como hospedeiros intermediários. É a segunda doença parasitária mais importante nomundo, atingindo mais de 220 milhões de pessoas. A busca por moluscicidas derivados de espécies vegetais tem sido intensificada como alternativa ao uso de moluscicidas sintéticos. O objetivo destetrabalho foi investigar o efeito moluscicida de Annona muricata e Jatropha elliptica no caramujoadulto e em suas desovas. Nos bioensaios, observou-se que os extratos etanólicos das espécies A. muricata e J. elliptica apresentaram efeito concentração-dependente com valores de DL90 68,3 e 41,1 mg/mL-1 , respectivamente, sobre o caramujo adulto, e DL90 27,7 e 24,0 mg/mL-1 sobre as suas desovas. As espécies vegetais investigadas neste trabalho apresentam efeito moluscicida epossivelmente podem ser fontes de compostos no controle da esquistossomose.

Schistosoma mekongi in Cambodia and Lao People's Democratic Republic.

Schistosomiasis found in communities along the Mekong River in Cambodia and Lao People's Democratic Republic (Lao PDR) is caused by the blood fluke Schistosoma mekongi. Early observations on patients in 1957 revealed severe intestinal and hepatosplenic disease. High mortality rates and widespread disease were reported from the provinces of northern Cambodia (Stung Treng and Kratié) and southern Lao PDR (Champasack) in the early 1970s and 1990s. Control programmes built around mass drug administration, with praziquantel, and combined with information and education campaigns, were carried out. In Cambodia, such programmes were started in 1995 in the endemic provinces and sustained until today; these efforts resolved the public health problem of schistosomiasis mekongi and led to a significant reduction in transmission. In Lao PDR, the interventions started in the late 1980s, but suffered several interruptions which permitted transmission to resume. Today, a number of small foci continue to show substantial prevalence rates. The snail intermediate host, Neotricula aperta, is present in the Mekong River and some of its tributaries. There is evidence that the snail might not yet have reached its full geographical distribution emphasising the need to sustain vigilance. New infections with S. mekongi occur in the endemic population and travellers alike. Comprehensive guidelines for the elimination of S. mekongi and bilateral efforts between Cambodia and Lao PDR are required.

Characteristics of granuloma formation and liver fibrosis in murine schistosomiasis mekongi: a morphological comparison between Schistosoma mekongi and S. japonicum infection.

A histopathological study was performed to clarify the characteristics of granuloma formation and liver fibrosis in Schistosoma mekongi infection in comparison with S. japonicum infection. Mice were exposed to S. mekongi (Laotian strain) and S. japonicum (Japanese strain) cercariae, and were dissected at 6, 8, 12, 16, and 20 weeks post-exposure. In the liver, granulomas in S. mekongi infection were cellular, initially organized with foam cells, and continuously appeared in the intralobular area, while granulomas in S. japonicum infection were fibrous and did not continuously appear in the intralobular area. Portal fibrosis was not seen in S. mekongi infection, but was commonly seen in S. japonicum infection in the later weeks. Granulomas in the small intestine were seen mainly in the submucosa with foam cells in S. mekongi infection and without foam cells in S. japonicum infection. The lung granulomas contained mainly histiocytes in both S. mekongi and S. japonicum infection. The absence of portal fibrosis in S. mekongi infection allows schistosome eggs to infiltrate into the intralobular area continuously, which can be what lies behind the ultrasonographic differences; the echogenic network pattern as was seen in S. japonicum infection, has not been noted in S. mekongi infection.

Immunoblot analysis of membrane antigens of Schistosoma mansoni, Schistosoma intercalatum, and Schistosoma haematobium against Schistosoma-infected patient sera.

Antigens present in aqueous n-butanolic extracts (BE) of Schistosoma mansoni (Venezuelan JL strain), Schistosoma intercalatum (Cameroon EDEA strain), and Schistosoma haematobium (Yemen strain) adult worm membranes were compared in immunoblot against sera of patients infected with S. mansoni, S. intercalatum, S. haematobium, Schistosoma japonicum, or Schistosoma mekongi looking for similarities (common antigens) and differences (species-specific antigens). About 17 S. mansoni BE polypeptides (M (r) approximately 8 to >80 kDa) were commonly recognized by S. mansoni-infected patient sera from Venezuela, Senegal, and Ethiopia. S. intercalatum-, S. haematobium-, or S. japonicum-infected sera were almost unreactive with S. mansoni BE. Nonetheless, S. mekongi-infected sera weakly cross-reacted with a approximately 10-15-kDa subset of S. mansoni BE. About 72.7% of S. intercalatum-infected patient sera reacted with a approximately 19-21-kDa complex in S. intercalatum BE and cross-reacted with a similar complex in S. haematobium BE. Conversely, all S. haematobium-infected patient sera reacted with a approximately 19-21-kDa complex in S. haematobium BE and cross-reacted with the approximately 19-21-kDa complex in S. intercalatum BE; S. mansoni- and S. japonicum-infected patient sera did not react with S. intercalatum or S. haematobium BE. Results showed the presence of a common membrane antigen between African schistosome species and species-specific antigens in S. mansoni BE that could be useful to discriminate between species and/or to detect Schistosoma infections.

Radiation-attenuated schistosome vaccination--a brief historical perspective.

The high level of protection which can be induced by vaccination of a range of hosts, from rodents to primates, with live radiation-attenuated schistosome larvae offers great promise for development of a human schistosome vaccine. Studies of the irradiated vaccine models benefitted from significant funding during the 1970-90s and much was learned concerning the inducers, targets and mechanisms of immunity. Less progress was made in definition of the protective antigens involved. The application of new techniques for identifying membrane and secreted antigens has recently provided new vaccine candidates and a new impetus for schistosome vaccine development. This article is intended as an overview of some of the main lessons learned from the studies of the irradiated vaccines as a backdrop to renewed interest in schistosome vaccine development.

Schistosoma spp.: Isolation of microtubule associated proteins in the tegument and the definition of dynein light chains components.

Schistosomes are parasitic blood flukes that reside in human mesenteric veins or urinary bladder veins, depending on species of the parasite. The syncytial tegument of these parasites represents a dynamic interface that regulates nutritional and immunological interactions between the parasite and the host. It is known that the components for biogenesis and maintenance of the tegument are supplied via vesicles from the nucleated cell bodies beneath the syncytium and muscle layer. To investigate the common motor components of vesicular transport in the tegument of schistomes, we extracted Schistosoma mansoni tegumental microtubule associated proteins utilizing detergent/high-salt procedure and raised antiserum against these proteins. The antiserum was applied to screen Schistosoma haematobium lambda gt11 expression library and some of the isolated clones were sequenced. Blast search for the sequences against NCBI database identified clones that are dynein light chains and myosin genes. Further analysis of schistosome dynein genes in the databases identified three families of dynein light chains (Dlcs). The Tctex family protein sequences are significantly different from the mammalian homologs and, therefore, offer a potential vaccine/drug target against schistosomes.

Allobilharzia visceralis gen. nov., sp. nov. (Schistosomatidae-Trematoda) from Cygnus cygnus (L.) (Anatidae).

In Iceland, the examination of whooper swans (Cygnus cygnus L.) viscera resulted in the detection of adult digenean flukes of the family Schistosomatidae. The mature worms occurring in the blood vessels of the large intestine and mesenterium caused vascular lesions, around the eggs deposited in the intestinal mucosa and liver granulomatous reactions developed. The morphology of the isolated schistosomes shows certain similarity with the flukes of the genus Trichobilharzia; in males reduced gynecophoral canal, and on both sexes both suckers and spatulate ends are present. However, the Icelandic flukes possess other morphological features which are distinct from the genus: the point of caecal reunion in males takes place posterior to gynecophoral canal and the genital pore is behind acetabulum and anterior to caecal reunion. In order to evaluate the identity of Icelandic schistosomes, sequencing of ITS region of DNA was performed, and the obtained sequence was deposited in GenBank under the accession no. DQ067561. Following phylogenetic analysis of relationship between the sequence of Icelandic flukes and database sequences of other bird schistosome genera (Trichobilharzia, Gigantobilharzia and Dendritobilharzia) showed different position of Icelandic worms in the phylogenetic tree. In conclusion, our study revealed new genus and species of schistosome flukes--Allobilharzia visceralis gen. et sp. n.

Schistosoma: cross-reactivity and antigenic community among different species.

It is not unusual to find common molecules among different species of the genus Schistosoma. When those molecules are antigenic, they may be used in immunodiagnosis and vaccines, but they could also be applied to taxonomic and evolutionary studies. To study cross-reactivity and antigenic community among different species of schistosomes, plasmas from laboratory animals infected with Schistosoma bovis, S. guineensis, S. rodhaini, S. haematobium, and four strains of S. mansoni were evaluated with a crude extract of adult worms of S. mansoni by Western blot. Using the multiple antigen blot assay, plasmas from these infected animals were exposed to a selected group of synthetic peptides from Sm28GST, Sm28TPI, Sm elastase, Sm97, Sm32, Sm31, and Sm Cathepsin L. The results presented herein demonstrate differential cross-reactivity and antigenic community among the Mansoni and Haematobium groups of schistosomes, which is of relevance as an additional new tool for phylogenetic studies of schistosomes as well as for diagnosis and vaccine purposes.

Mutagenicity evaluation of Schistosoma spp. extracts by the umu-test and V79/HGPRT gene mutation assay.

Schistosomiasis has been suspected of being a risk factor for various types of cancers for sometime, e.g., bladder cancer, colorectal cancer and hepatic cancer. Among them, the etiological relationship between urinary schistosomiasis and bladder cancer is now widely accepted. However, mechanisms of the carcinogenesis are still unclear. Here, we tested the mutagenicity of the parasite extracts by the umu-test and hypoxanthine guanine phosphoribosyltransferase (HGPRT) gene mutation assay, which both overcome disadvantages of the Ames plate assay. Adult worm extracts and egg extracts of Schistosoma haematobium and Schistosoma mansoni were tested. Under our experimental conditions, neither worm nor egg extracts were shown to have any mutagenicity in both tests even in the presence of S9 mix. Our results suggest that there is very little possibility of immediate gene mutation due to the parasite-derived substances in schistosomiasis-related carcinogenesis.

Cytokine-mediated host responses during schistosome infections; walking the fine line between immunological control and immunopathology.

Most helminth infections of humans and animals induce similar immune responses, which are characterised by the production of Th2-associated cytokines (interleukin (IL)-4, IL-5, IL-9, IL-10, IL-13) and antibodies (IgG1--mouse, IgG4--man, IgE--both). This type-2-biased immune phenotype generally persists for the duration of the infection. Although similar types of immune responses are also triggered during allergy, atopy and anaphylaxis, chronic helminth-induced type-2-associated responses are usually held in check by appropriately regulated control mechanisms that limit the destructive potential of prolonged cytokine bias. Among numerous reported activities, helminth-induced type-2-associated immune responses have been linked to the expulsion of gastrointestinal nematodes and the formation of circumoval granulomas during schistosomiasis. However, what happens when this highly regulated, and often beneficial, type-2 immune response becomes chronic, improperly controlled, or exaggerated during helminth infections? Using schistosomiasis as a model disease, we describe the lethal consequences of inappropriate immune response induction by reviewing the literature generated from experimental animal studies and human epidemiological investigations. Development of severe and non-overlapping immunopathological phenotypes will be discussed in the context of immune deviation and in the setting of chronic and/or hyper-polarised cytokine environments.

Recent studies on Schistosoma intercalatum: taxonomic status, puzzling distribution and transmission foci revisited

Schistosoma intercalatum, which causes human rectal schistosomiasis in Africa, still presents a great interest for its imprecise taxonomic status and its puzzling distribution in Africa. Two geographically isolated strains of S. intercalatum are recognized, the Lower Guinea strain and the Congo strain, which differ from each other in a number of morphological, biological and biochemical characteristics. Recent molecular data using RAPD markers indicate high divergence between the two strains, with values of Nei and Li's similarity indice allowing recognition of two genetically distinct taxa: experiments on pre- and post-isolating mechanisms are in progress in order to re-evaluate the taxonomic status of this polytypic species. With regard to its geographical distribution, S. intercalatum is characterized by the existence of two stable endemic areas (localized in Lower Guinea and North East of Democratic Republic of Congo) which correspond to the historical areas of species discovery, and the emergence during the last 15 years of new foci of the Lower Guinea strain outside previously known endemic areas. The absence of local adaptation of the Lower Guinea strain to its intermediate host, supported by experimental studies, may help to facilitate the spread of this strain. Nevertheless, the present restricted distribution of this species remains puzzling, because its potential snail hosts (bulinids) are widely distributed throughout much of Africa. Recent experimental and epidemiological studies suggest that interspecific sexual interactions between human schistosomes could have a role in limiting the distribution of S. intercalatum: the competitive sexual processes acting among human schistosomes show that S. haematobium and S. mansoni are always competitively dominant over S. intercalatum. These epidemiological observations lead the authors to distinguish three kinds of transmission foci for S. intercalatum

[Schistosoma intercalatum bilharziasis: clinical and epidemiological considerations]. / La bilharziose à Schistosoma intercalatum: considèrations cliniques et èpidèmiologiques.

Schistosoma intercalatum bilharziasis continues to raise numerous questions regarding pathogenicity and gravity. The parasite was identified recently and the last fully described outbreak occurred 10 years ago in the city of Bata, Equatorial Guinea. Geographically Schistosoma intercalatum biharziasis is limited to one part of the African continent but has shown a tendency to spread. Hybridization of Schistosoma intercalatum and Schistosoma haematobium has been observed. The main clinical manifestation of Schistosoma intercalatum is rectal bleeding. The endoscopic appearance of lesions is variable and non-specific ranging from granulomas or polyps to ulcerations. Complications include severe rectitis or genital involvement such as salpingitis with secondary sterility. Spontaneous abortion has also been reported. Association with salmonella and klebsiella infection has been confirmed and can lead to life-threatening situations. Few studies have been performed to assess the value of diagnostic tests. The sensitivity of stool smears and urinary sedimentation testing is 81.7% and 56.3% respectively using the two examinations as references for one another. The sensitivity of immunological tests is generally good but varies depending on the reference technique used. Specificity can be affected by cross-reaction with other schistosomas or trematodes and even with nematodes and hematozoons. Treatment with a single dose of Biltricide has proven to be effective. Prevention requires education of the population at risk and use of molluscacides. The control strategy must be adapted in function of the epidemiology of the disease, diagnostic data, cost and effectiveness of screening and treatment.

Schistosomiasis in the Republic of São Tomé and Principe: human studies.

The only schistosome species found in stool specimens in the local population of the republic of São Tomé is Schistosoma intercalatum. An initial survey of schoolchildren showed an overall prevalence of 10.9%, with some schools reaching 29%. No S. haematobium egg was found in 782 urine specimens from the local population, although some were seen in the urine of Angolan soldiers stationed near the capital city. One village in the endemic area, San Marçal, had an S. intercalatum prevalence of 43%, with 14 persons > 40 years of age harbouring severe infections. The transmission area is restricted to the north-east of the main island, where 5 foci apparently account for most of the infections. Seven cases recorded from Principe may be explained by the fact that the children were attending school at São Tomé. Women carrying out domestic activities are more at risk of contracting the infection because of longer periods of water contact than men. The morbidity produced by the infection is restricted to splenomegaly and blood in the stools. High prevalences have been found of Ascaris lumbricoides and Trichuris trichiura, and hookworm and Stronglyloides stercoralis were also observed. Praziquantel was well tolerated and appears to be a good tool for control purposes, although reinfection in the transmission area apparently occurs rapidly. Control strategies based on chemotherapy should take into account an older age group as well as the schoolchildren. Focal mollusciciding and the introduction of washing facilities may also have a role to play in control. The possible recent introduction of the infection to the island is discussed.

[Bilharziasis caused by Schistosoma intercalatum, a recent and forgotten form of schistosomiasis]. / Bilharziose à Schistosoma intercalatum bilharziose récente et oubliée.

Schistosoma intercalatum schistosomiasis is confined to the western regions of equatorial Africa. It is often asymptomatic but it produces microscopic lesions in the intestine (mainly the rectum), the liver and the genital organs of both men and women, the latter lesions being more insidious and insufficiently explored. Its treatment, like that of other schistosomiases, consists of one course of praziquantel. Naturally, S. intercalatum may be hybridized with S. haematobium in Gabon and Cameroun which are the two countries where the two parasites coexist.

Pulmonary pathology in rabbits infected with the Baling and Koyan strains of Schistosoma malayensis.

Two distinct strains of Schistosoma malayensis exist in Malaysia (designated the Baling and Koyan strains). Both these strains show intraspecific variations in pathology (Greer et al, 1988). To evaluate the differences in the pulmonary pathology resulting from infections of the two different strains of Malaysian schistosome, a total of 20 experimental rabbits were infected, 10 each with cercariae of the Koyan strains. Pathological changes were studied over a period of 28 weeks. Granulomas in the lung occurring as a result of infection with the Baling strain were compared with those caused by infection with the Koyan strain. Although both strains produced parenchymatous and alveolar lesions, granulomas caused by the Baling strain of Malaysian schistosome were more numerous and larger (when comparing mean diameter as well as area of granuloma, p < 0.05). In addition, pulmonary vascular hypertensive changes were present in Baling strain infected rabbits. These comprised of pulmonary arteriolar endothelial swelling and damage, intimal elastosis and medial hypertrophy. Angiitis and pulmonary periphlebitis were also noted occasionally. In contrast, Koyan strain infection resulted in fewer and smaller granulomas. Pulmonary vascular changes were minimal.

Molecular evidence linking hominid evolution to recent radiation of schistosomes (Platyhelminthes: Trematoda).

Molecular phylogenies for seven species of schistosomes, including four species infecting man, were constructed from PCR-amplified sequences of two ribosomal genes: one nuclear (internal transcribed spacer 2 in the ribosomal multigenic family) and one mitochondrial (16S rDNA). The two phylogenies obtained are congruent, and the data suggest that the mitochondrial sequence evolves about three times faster than the nuclear sequence. We propose a calibration of the phylogenetic tree of schistosomes that dates "human capture" of these parasites from other animal hosts (rodents and ruminants) in Africa to 1-10 million years ago, when the first hominids invaded savanna areas, which are the favorable environment for parasite transmission.