Schistosomiasis

Transmission dynamics of Schistosoma japonicum in the lakes and marshlands of China

BACKGROUND

Schistosoma japonicum is a major public health concern in China, with over one million people infected and another 40 million living in areas at risk of infection. Unlike the disease caused by S. mansoni and S. haematobium, schistosomiasis japonica is a zoonosis, involving a number of different mammalian species as reservoir hosts. As a result of a number of published reports from China, it has long been considered that bovines, particularly water buffaloes, play a major role in human S. japonicum transmission there, and a drug-based intervention study (1998-2003) around the Poyang Lake in Jiangxi Province provided proof of concept that water buffaloes are, indeed, major reservoirs of human infection in this setting.

METHODS AND FINDINGS

In this study we incorporated recently obtained epidemiological information to model the steady-state S. japonicum transmission as well as the impact of the removal of S. japonicum transmission attributable to water buffaloes on human infection rates across six different endemic scenarios within three villages in the Dongting (Hunan) and Poyang (Jiangxi) lakes of southern China. Similar results were obtained for all scenarios. Steady-state S. japonicum infection rates remained constant and human prevalence and incidence were predicted to fall considerably over time. The model showed that the contribution of S. japonicum water buffalo transmission to human infection ranged from 39.1% to 99.1% and predicted that the removal of water buffalo transmission would reduce parasite reproductive rates below 1. This indicates that without the contribution of water buffaloes, S. japonicum transmission is interrupted and unsustainable. These scenarios are generalizable to other endemic villages in the lake and marshland areas of China where a similar cycle of snail infection and infection/reinfection of humans and bovines occurs.

CONCLUSIONS

Along with previous epidemiological data, our findings strongly support water buffaloes as an important component of the transmission cycle that affects humans in the lake and marshlands region of China, a feature which appears to differ from the situation prevalent in the Philippines where their contribution is less pronounced. Our conclusions underscore the rationale for removal, replacement or treatment of water buffaloes, and for the development and deployment of a transmission blocking buffalo vaccine against S. japonicum for this setting to achieve the goal of transmission control. The Chinese Government has recently commenced a new integrated national strategy to improve on existing approaches to control schistosomiasis in the lake and marshlands region by reducing bovines and humans as a source of S. japonicum infection to Oncomelania snails.

Metabolic profiling of a Schistosoma mansoni infection in mouse tissues using magic angle spinning-nuclear magnetic resonance spectroscopy

In order to enhance our understanding of physiological and pathological consequences of a patent Schistosoma mansoni infection in the mouse, we examined the metabolic responses of different tissue samples recovered from the host animal using a metabolic profiling strategy. Ten female NMRI mice were infected with approximately 80 S. mansoni cercariae each, and 10 uninfected age- and sex-matched animals served as controls. At day 74 post infection (p.i.), mice were killed and jejunum, ileum, colon, liver, spleen and kidney samples were removed. We employed (1)H magic angle spinning-nuclear magnetic resonance spectroscopy to generate tissue-specific metabolic profiles. The spectral data were analyzed using multivariate modelling methods including an orthogonal signal corrected-projection to latent structure analysis and hierarchical principal component analysis to assess the differences and/or similarities in metabolic responses between infected and non-infected control mice. Most tissues obtained from S. mansoni-infected mice were characterized by high levels of amino acids, such as leucine, isoleucine, lysine, glutamine and asparagine. High levels of membrane phospholipid metabolites, including glycerophosphoryl choline and phosphoryl choline were found in the ileum, colon, liver and spleen of infected mice. Additionally, low levels of energy-related metabolites, including lipids, glucose and glycogen were observed in ileum, spleen and liver samples of infected mice. Energy-related metabolites in the jejunum, liver and renal medulla were found to be positively correlated with S. mansoni worm burden upon dissection. These findings show that a patent S. mansoni infection causes clear disruption of metabolism in a range of tissues at a molecular level, which can be interpreted in relation to the previously reported signature in a biofluid (i.e. urine), giving further evidence of the global effect of the infection.

Immune response and pathogenesis of neuroschistosomiasis mansoni

The involvement of the central nervous system (CNS) by schistosomes may or may not determine clinical manifestations. When symptomatic, neuroschistosomiasis (NS) is one of the most severe presentations of schistosome infection. Considering the symptomatic form, Schistosoma mansoni causes almost always spinal cord disease. Cerebral and spinal cord disorders in S. mansoni infections are inflammatory conditions of the CNS that cause mild-moderate impairment of the blood-brain barrier and intrathecal synthesis of antibodies against schistosomal antigens. Little is known about the pathogenesis of NS, but available evidence strongly suggests that it depends basically on the presence of parasite eggs in the nervous tissue and on the host's immune response against the trapped eggs. Numerous eggs surrounded by granulomas lodged together in circumscribed areas of the CNS damage the nervous tissue by both the mass effect and the egg-induced inflammatory reaction. Vasculitis of immune etiology, which causes isquemic lesions, may also play an important role in the genesis of the neurological symptoms. Although the mechanisms involved in the immunophatogenesis of NS are largely unknown, initial investigations on cerebrospinal fluid (CSF) and serum cytokine profiles suggest the occurrence of inflammation as well as a skewed Th2 immune response that probably occur both locally and systemically.

Clinical characterization of neuroschistosomiasis due to Schistosoma mansoni and its treatment

The involvement of the central nervous system (CNS) by Schistosoma mansoni may or may not cause clinical manifestations. When symptomatic, neuroschistosomiasis mansoni (NSM) is one of the most severe presentations of this infection. The neurological manifestations are due to numerous granulomas grouped in confined areas of the spinal cord or the brain. Considering the symptomatic form, myelopathy is far more frequent than the cerebral disease. Spinal cord NSM presents as a low cord syndrome of acute/subacute progression usually associated with involvement of the cauda esquina roots. Lower limbs pain, weakness and sensory disturbance, and autonomic dysfunctions, particularly bladder dysfunction, are often present. Cerebrospinal fluid (CSF) examination generally shows an inflammatory pattern with or without eosinophils and/or IgG against schistosomal antigens. Magnetic resonance imaging (MRI) demonstrates signs of inflammatory myelopathy. Cerebral NSM presents as a slow-expanding intracranial tumor-like lesion. Its clinical manifestations are variable and depend on the increased intracranial pressure and on the site of the lesion. The diagnosis of spinal cord NSM is based on clinical evidence whereas the cerebral disease is usually diagnosed by biopsy of the nervous tissue. There is no consensus on the treatment of NSM. We discuss the literature data on this topic, and suggest a therapeutic approach based on our experience with 69 spinal cord NSM patients who have been followed up by a long period of time. Outcome is largely dependent on early treatment, particularly in the medullar disorder, and is better in cerebral NSM.

Expression and characterization of two tyrosinases from the trematode Schistosoma japonicum

Tyrosinase (TYR) was thought to play a critical role during trematode egg production. In this study, we analyzed two genes (SjTYR1 and SjTYR2), derived from Schistosoma japonicum genome databases, which encode proteins with significant homologies to mammalian TYR. They exhibited the typical TYR topology, including two copper-binding domains and a highly conserved cysteine-rich domain. Semi-quantitative reverse transcription polymerase chain reaction showed that two SjTYR genes were mainly expressed in the female adult worm. A complementary DNA coding the putative common copper center domain of each SjTYR was cloned and inserted into a pET-28a-c(+) prokaryotic expression vector. After purification, the recombinant proteins expressed in Escherichia coli were used to produce their specific antibodies. The native active SjTYRs enzyme appeared to function as a homodimer, the subunits of which were linked to each other via covalent disulfide bonds. Both female and male worms possessed monophenol oxidase and diphenol oxidase activities of TYR. The relative enzymatic activities were 0.165 min(-1) mg(-1) and 0.0805 min(-1) mg(-1), which were inhibited by a copper-chelating agent (allyl thiourea) and correlated with disruption of female egg production. Our results revealed that SjTYRs might play a significant role during eggshell formation.

Proteome approach for identification of schistosomiasis japonica vaccine candidate antigen

Experimental vaccination with radiation-attenuated cercariae (RAC) confers possible practical levels of resistance to challenge infection by humoral and by cellular mechanism. Here, we aimed to identify possible vaccine antigens by using specific IgG antibody from RAC vaccinated miniature pig. Two milligrams of soluble egg antigen (SEA) or schistosomal worm antigen preparation (SWAP) was fractionated using two dimensional liquid chromatography (proteome PF 2D) consisted of high performance chromatofocusing (HPCF) and high resolution reversed phase chromatography (HPRP). Of the 42 HPCF fractions of SEA or SWAP, 26 (61.9%) or 15 (35.7%) showed positive dot blot reaction with RAC vaccinated serum respectively. The dot blot positive fractions were applied to the second HPRP column. One hundred and seven out of 26 x 96 of SEA fractions and 18 out of 15 x 96 SWAP fractions reacted with RAC vaccinated serum. From the positive fractions we chose 17 of SEA and 10 of SWAP that had no reactivity with normal cercariae infected (NCI) sera and had single peak of 214 nm; and automated N-terminal amino acid sequence based on in situ Edman Reaction was conducted. Four sequences were obtained and applied to the homology search in NCBI database. A total of eight candidate genes were listed up and their cDNA clones from schistosomula stage were obtained. Two of the recombinant proteins (AAW27472.1 and AXX25883.1) showed strong reactivity with the RAC vaccinated serum but marginal with NCI serum. This protocol using proteome PF 2D could be applicable in identifying immunoreactive proteins from crude extract for the development of vaccines or for diagnostics.

Helminthic parasites and seizures

A large number of helminthic parasites are known to involve the central nervous system (CNS) and produce neurologic symptoms including seizures and epilepsy. Taenia solium (the pork tapeworm) is perhaps most widely prevalent and well known for its association with seizures and epilepsy. Many of the other helminthic disorders have fairly restricted geographic predilections and their occurrence in much of the remaining world is limited to rare cases among travelers and immigrants. Nonetheless, knowledge about the helminthic disorders, the life cycle of their causative agents, and their clinical manifestations and diagnostic features are important in order to recognize them.

Schistosomiasis: an unexpected finding in an inguinal hernia sac

We report an 11-year-old boy who was diagnosed with schistosomiasis based on histopathologic examination of an inguinal hernia sac specimen. The child was an immigrant from Liberia and presented to our institution with inguinal and scrotal swelling. His past medical history was remarkable for previous ipsilateral hernia sac repair in West Africa, and at the time of his recurrent hernia repair, he was noted to have a peculiar loculated fluid-filled hernia sac, which was sent for pathologic examination because of its unusual appearance. Histologic examination revealed an intense infiltrate of eosinophils and numerous granulomas with ova of Schistosoma mansoni, and this speciation was confirmed with a stool wet prep examination for ova and parasites. Review of the English-language literature uncovered no prior cases of schistosomiasis presenting as an inguinal hernia. This unusual finding in a "routine" specimen, otherwise destined for the incinerator without pathologic evaluation, reinforces the importance of surgical vigilance in recognizing unusual or atypical features in these specimens.

A Mathematical model of Schistosoma mansoni in Biomphalaria glabrata with control strategies

We describe and analyze a mathematical model for schistosomiasis in which infected snails are distinguished from susceptible through increased mortality and no reproduction. We based the model on the same derivation as Anderson and May (J. Anim. Ecol. 47:219-247, 1978), Feng and Milner (A New Mathematical Model of Schistosomiasis, Mathematical Models in Medical and Health Science, Nashville, TN, 1997. Innov. Appl. Math., Vanderbilt Univ. Press, Nashville, pp. 117-128, 1998), and May and Anderson (J. Anim. Ecol. 47:249-267, 1978), but used logistic growth both in human and snail hosts. We introduce a parameter r, the effective coverage of medical treatment/prevention to control the infection. We determine a reproductive number for the disease directly related to its persistence and extinction. Finally, we obtain a critical value for r that indicates the minimum treatment effort needed in order to clear out the disease from the population.

Intramedullary schistosomiasis presenting in an adolescent with prolonged intermittent back pain

A 14-year-old boy traveling from Guinea presented with a 2-month history of stable lower back pain. His neurologic examination was significant only for mild weakness in the distal lower extremities. He manifested peripheral eosinophilia, and magnetic resonance imagining revealed enlargement of the caudal aspect of the spinal cord and conus. A presumptive diagnosis of spinal schistosomiasis was rendered, and appropriate medication was administered before obtaining positive serology results. The patient's signs rapidly resolved. Spinal schistosomiasis should be considered in the differential diagnosis of any child with back pain and an appropriate travel history.

[Vulval bilharziasis]

Vulvar localisation of schistosomiasis is a rare presentation. We report a case of a woman of 20 years old hospitalised for a vulvar mass of six months. That mass progressively increased in volume and was tender. It was accompanied by frequency and dysuria. The patient had a history of swimming in fresh water and hematuria when she was eight years old. Initial clinical examination found a good general state, there was a mass involving the clitoris and the small lips. This painless mass had a cauliflower appearance and was soft with a large implantation. Pathology exam of the mass revealed a vulvar schistosomiasis with an important amount of living eggs. A tumour removal with a plasty of small lips was performed. Additionally, praziquantel was administered orally. Vulvar localisation of schistosomiasis might suggest a malignant tumour. Only pathological examination can assess the diagnosis.

Retroperitoneal fibrosis and schistosomiasis: a causal relationship?

Retroperitoneal fibrosis (RPF) is characterized by replacement of the normal tissue of the retroperitoneum with fibrosis and/or chronic inflammation. About two-thirds of cases of RPF are idiopathic and one-third is secondary to drugs, infections (tuberculosis, syphilis, actinomycosis, fungal infections), retroperitoneal hemorrhage, or malignancy. We report the case of a patient who was diagnosed as having RPF and schistosomiasis caused by Schistosoma haematobium with histological documentation. He was treated with praziquantel and afterwards with corticosteroids with remission of RPF. To our knowledge, the association between schistosomiasis and RPF has not been described in the literature. We postulate that there is a causal relationship between these two conditions.

Decision-model estimation of the age-specific disability weight for schistosomiasis japonica: a systematic review of the literature

Schistosomiasis is among the most prevalent parasitic infections worldwide. However, current Global Burden of Disease (GBD) disability-adjusted life year estimates indicate that its population-level impact is negligible. Recent studies suggest that GBD methodologies may significantly underestimate the burden of parasitic diseases, including schistosomiasis. Furthermore, strain-specific disability weights have not been established for schistosomiasis, and the magnitude of human disease burden due to Schistosoma japonicum remains controversial. We used a decision model to quantify an alternative disability weight estimate of the burden of human disease due to S. japonicum. We reviewed S. japonicum morbidity data, and constructed decision trees for all infected persons and two age-specific strata, <15 years (y) and ≥15 y. We conducted stochastic and probabilistic sensitivity analyses for each model. Infection with S. japonicum was associated with an average disability weight of 0.132, with age-specific disability weights of 0.098 (<15 y) and 0.186 (≥15 y). Re-estimated disability weights were seven to 46 times greater than current GBD measures; no simulations produced disability weight estimates lower than 0.009. Nutritional morbidities had the greatest contribution to the S. japonicum disability weight in the <15 y model, whereas major organ pathologies were the most critical variables in the older age group. GBD disability weights for schistosomiasis urgently need to be revised, and species-specific disability weights should be established. Even a marginal increase in current estimates would result in a substantial rise in the estimated global burden of schistosomiasis, and have considerable implications for public health prioritization and resource allocation for schistosomiasis research, monitoring, and control.

Schistosomiasis is a parasitic infection caused by a flatworm that disproportionately affects the world's poorest populations. Schistosomiasis is one of the most common infections worldwide, affecting over 207 million people in 76 countries. Current international estimates indicate that schistosomiasis has a minimal impact at the population level. This has contributed to its low prioritization in global health and subsequent resource allocation for disease control. However, recent studies indicate that these measures underestimate the extent of neglected tropical diseases, including schistosomiasis. Despite World Health Organization recommendations, the burden of schistosomiasis has not been re-examined in over a decade, and there are no established estimates for different types of schistosomiasis. The impact of symptoms associated with the Asian strain, Schistosoma japonicum, remains controversial. This study was conducted to provide an alternate measure of the burden of S. japonicum. We reviewed the literature and calculated a summary estimate for S. japonicum which was seven to 46 times greater than current measures for schistosomiasis. Findings suggest that current measures severely underestimate the extent of schistosomiasis, and urgently need to be revised. Further research is needed to examine the burden of schistosomiasis and other forgotten tropical diseases affecting the world's poorest people in endemic countries.

Parasitic lung infection and the paediatric lung

Human parasitosis is still prevalent worldwide and causes significant morbidity and mortality in developing countries. The involvement of the lung is variable depending on the characteristics of the parasites and hosts. In malnourished and immunodeficient children, the consequences of lung parasitosis may result in significant morbidity and mortality.

Current status of vaccines for schistosomiasis

Schistosomiasis, caused by trematode blood flukes of the genus Schistosoma, is recognized as the most important human helminth infection in terms of morbidity and mortality. Infection follows direct contact with freshwater harboring free-swimming larval (cercaria) forms of the parasite. Despite the existence of the highly effective antischistosome drug praziquantel (PZQ), schistosomiasis is spreading into new areas, and although it is the cornerstone of current control programs, PZQ chemotherapy does have limitations. In particular, mass treatment does not prevent reinfection. Furthermore, there is increasing concern about the development of parasite resistance to PZQ. Consequently, vaccine strategies represent an essential component for the future control of schistosomiasis as an adjunct to chemotherapy. An improved understanding of the immune response to schistosome infection, both in animal models and in humans, suggests that development of a vaccine may be possible. This review considers aspects of antischistosome protective immunity that are important in the context of vaccine development. The current status in the development of vaccines against the African (Schistosoma mansoni and S. haematobium) and Asian (S. japonicum) schistosomes is then discussed, as are new approaches that may improve the efficacy of available vaccines and aid in the identification of new targets for immune attack.

Experimental vaccines in animal models for schistosomiasis

Considerable morbidity and mortality results from the affliction of an estimated 200 million people worldwide by several species of schistosomes; 779 million are exposed to the disease in 74 different countries. Even though anti-parasitic drugs and other control measures, including public hygiene and snail control are available, the advent of an effective vaccine still remains the most potentially powerful means for the control of this disease. The putative vaccine could be administered to small children prior to the time when their contact with infected water is maximal, so as to prevent severe infection in the subsequent years. This review attempts to summarize the status of schistosome vaccine development with special emphasis on functionally important vaccine candidates. The importance of utilizing both murine and nonhuman primate models as a prerequisite for clinical trials is discussed.

Expression, immunolocalization and serodiagnostic value of a myophilin-like protein from Schistosoma japonicum

The cDNA of a Schistosoma japonicum myophilin-like protein was cloned, sequenced, and expressed in Escherichia coli as a recombined protein (rSj myophilin-like protein), and the protein was purified by affinity chromatography. The deduced amino acid sequences of the Sj myophilin-like protein showed significant homology to myophilin, calponin, Np22 and Mp20. Northern blot and RT-PCR analyzes revealed expression of the Sj myophilin-like protein mRNA in eggs, sporocysts, cercariae, hepatic schistosomula and adult worms. Confocal fluorescence microscopy localized the native protein to the muscle of the adult worm. In schistosome-infected rabbits, the rSj myophilin-like protein antibody level, assessed by ELISA, was elevated after infection but was reduced after praziquantel treatment. In humans, the myophilin-like protein antibody level was evaluated by ELISA in sera from 33 non-infected humans and 61 schistosomiasis patients; the results showed a highly significant difference between the two groups with a sensitivity of 57.4%. Taken together, the myophilin-like protein may prove useful for monitoring the therapeutic effect of praziquantel rather than in serodiagnosis of schistosomiasis.

Transmission of tropical and geographically restricted infections during solid-organ transplantation

In recent years, the increasing number of donors from different regions of the world is providing a new challenge for the management and selection of suitable donors. This is a worldwide problem in most countries with transplantation programs, especially due to the increase in immigration and international travel. This paper elaborates recommendations regarding the selection criteria for donors from foreign countries who could potentially transmit tropical or geographically restricted infections to solid-organ transplant recipients. For this purpose, an extensive review of the medical literature focusing on viral, fungal, and parasitic infections that could be transmitted during transplantation from donors who have lived or traveled in countries where these infections are endemic has been performed, with special emphasis on tropical and imported infections. The review also includes cases described in the literature as well as risks of transmission during transplantation, microbiological tests available, and recommendations for each infection. A table listing different infectious agents with their geographic distributions and specific recommendations is included.

Up-converting phosphor technology-based lateral flow assay for detection of Schistosoma circulating anodic antigen in serum

Schistosoma sp. circular anodic antigen (CAA) serum concentrations reflect actual worm burden in a patient and are a valuable tool for population screening and epidemiological research. However, for the diagnosis of individual imported schistosomiasis cases, the current enzyme-linked immunosorbent assay (ELISA) lacks sensitivity and robustness. Therefore, a lateral flow (LF) assay was developed to test CAA in serum for individual diagnosis of imported active schistosome infections. Application of fluorescent submicron-sized up-converting phosphor technology (UPT) reporter particles increased analytical sensitivity compared to that of the standard ELISA method. Evaluation of the UPT-LF test with a selection of 40 characterized epidemiologic samples indicated a good correlation between signal intensity and infection intensity. Subsequently, the UPT-LF assay was applied to 166 serum samples of Dutch residents (immigrants and travelers) suspected of schistosomiasis, a case in which group routine antibody detection frequently fails straightforward diagnosis. The UPT-LF assay identified 36 CAA-positive samples, compared to 15 detected by CAA-ELISA. In conclusion, the UPT-LF assay is a low-complexity test with higher sensitivity than the CAA-ELISA, well suited for laboratory diagnosis of individual active Schistosoma infections.

Cloning and characterization of an orphan seven transmembrane receptor from Schistosoma mansoni

A partial cDNA sequence was obtained from the human blood fluke, Schistosoma mansoni using a signal sequence trap approach. The full-length cDNA was cloned and termed Sm-7TM. The corresponding open reading frame had 7 membrane spanning domains and shared identity with a small, novel group of seven transmembrane (7TM) receptors from vertebrates and invertebrates, including the human ee3 receptor - a heptahelical protein implicated in neuronal signalling. Phylogenetic analysis of this novel family showed that the Sm-7TM ORF formed a clade with exclusively invertebrate sequences. Based on topology modelling with ee3, Sm-7TM was predicted to possess an intracellular C-terminal tail, which was expressed as a soluble thioredoxin fusion protein (Sm-7TMC) in Escherichia coli and purified using metal ion-affinity chromatography. A polyclonal antiserum against this domain was used to detect Sm-7TM in detergent-soluble parasite extracts and to immunolocalize the receptor to the tegument of adult S. mansoni.

Tyrosine kinase and cooperative TGFβ signaling in the reproductive organs of Schistosoma mansoni

Drug-induced suppression of female schistosome sexual maturation is an auspicious strategy to combat schistosomiasis since the eggs are the causative agent. The establishment of drug targets requires knowledge about the molecular mechanisms that regulate the development of the female reproductive organs, which include vitellarium and ovary. This review summarizes recent studies suggesting tyrosine kinases as important factors for the regulation of female gonad development. In this context, especially cytoplasmatic tyrosine kinases of the Src class seem to play dominant roles. Moreover, experimental data and theoretical concepts are provided supporting a crosstalk between tyrosine kinase and TGFbeta signaling in the production of vitellocytes. Finally, we take advantage from the schistosome genome project to propose a model for the regulation of vitelline-cell production and differentiation.

sTNFR-II and sICAM-1 are associated with acute disease and hepatic inflammation in schistosomiasis japonica

Soluble intracellular adhesive molecule 1 (sICAM-1) and tumour necrosis factor receptors I (TNFR-1) and II (TNFR-II) have been shown to be associated with numerous liver disorders. Shedding of these membrane proteins can be triggered by the Th1 cytokines, TNF-alpha and IFN-gamma, which are associated with susceptibility or resistance to hepatic schistosomiasis, respectively. Further, TNF-alpha receptors and sICAM-1 have been implicated in periportal fibrosis in advanced human schistosomiasis mansoni and correlate with schistosome granuloma formation in the murine model. We measured serum levels of sICAM-1, TNFR-I and TNFR-II in Chinese patients with different clinically defined stages of schistosomiasis japonica and controls; these included 35 patients with acute schistosomiasis, 45 patients with chronic schistosome infections, 34 advanced patients with evidence of severe morbidity and 20 patients with no known history of exposure to infection. Markedly elevated levels of soluble TNFRs (sTNFRs) and sICAM-1 were observed in the acute and advanced patients compared with the chronic and control groups. Mean sTNFR-II levels were significantly higher in acute patients compared with advanced (P < 0.00001) and chronic patients (P < 0.00001) and showed the strongest association of the markers with acute disease (odds ratio (OR) = 1.099). sTNFR-II and sICAM-1 levels both correlated with infection intensity and there were significant positive correlations observed between eosinophil count and infection intensity (P = 0.0072) and sICAM-1 (P = 0.0014). Although there were significantly higher levels of antigen-specific IgG4 and total IgG in infected individuals compared with controls, none correlated with infection intensity. Further, no differences in IgG4 and total IgG levels were observed between the acute and chronic groups. The results suggest sTNFRs and sICAM-1 are associated with liver inflammation and disease progression. Measurement of sTNFR-II and sICAM-1 levels in serum could serve as additional markers for the diagnosis of acute stage disease and the monitoring of hepatic inflammation in human schistosomiasis japonica.

High prevalence and presumptive treatment of schistosomiasis and strongyloidiasis among African refugees

BACKGROUND

Schistosomiasis and strongyloidiasis cause substantial morbidity and mortality among hundreds of millions of infected persons worldwide. In the United States, these infections are most commonly found among international travelers, immigrants, and refugees from areas of endemicity. Refugees resettled to the United States since 2000 include >3800 "Lost Boys and Girls" of Sudan and 8000 Somali Bantu. Many Lost Boys and Girls of Sudan reported chronic abdominal pain only since arrival, and some received diagnoses of schistosomiasis or strongyloidiasis. We assessed seroprevalence of these infections among these refugees and hypothesized an association between infection and abdominal pain.

METHODS

We offered a survey assessing chronic abdominal pain and serologic testing for schistosomiasis and strongyloidiasis to all 800 attendees of a Lost Boys and Girls of Sudan reunion in the United States. Serologic testing was performed on preimmigration specimens obtained from 100 United States-bound Somali Bantu refugees.

RESULTS

Of the 462 Sudanese refugees (58%) tested, 44% and 46% were seropositive for schistosomiasis (primarily due to Schistosoma mansoni) and strongyloidiasis, respectively; 24% of those who tested positive for schistosomiasis had S. mansoni antigenemia. Forty-six percent reported chronic abdominal pain, which was not associated with either infection. Among 100 Somali Bantu, 73% and 23% tested seropositive for schistosomiasis (primarily due to Schistosoma haematobium) and strongyloidiasis, respectively.

CONCLUSIONS

The high seroprevalence of schistosomiasis and strongyloidiasis among Sudanese Lost Boys and Girls and Somali Bantu refugees supports presumptive treatment for these refugees. Current refugee resettlement policies inadequately address these diseases; our data support consideration of predeparture presumptive therapy for all refugees from areas of endemicity.

Neurological complications of Schistosoma infection

Schistosomiasis is a parasitic disease caused by blood flukes of the genus Schistosoma. Currently more than 200 million people worldwide are affected. Neuroschistosomiasis constitutes a severe presentation of the disease. Neurological symptoms result from the inflammatory response of the host to egg deposition in the brain and spinal cord. Neurological complications of cerebral schistosomiasis include delirium, loss of consciousness, seizures, dysphasia, visual field impairment, focal motor deficits and ataxia. Cerebral and cerebellar tumour-like neuroschistosomiasis can present with increased intracranial pressure, headache, nausea and vomiting, and seizures. Myelopathy (acute transverse myelitis and subacute myeloradiculopathy) is the most common neurological complication of Schistosoma mansoni infection. Schistosomal myelopathy tends to occur early after infection and is more likely to be symptomatic than cerebral schistosomiasis. The conus medullaris and cauda equina are the most common sites of involvement. Severe schistosomal myelopathy can provoke a complete flaccid paraplegia with areflexia, sphincter dysfunction and sensory disturbances. Schistosomicidal drugs, steroids and surgery are the currently available treatments for neuroschistosomiasis. Rehabilitation and multidisciplinary team care are needed in severely disabled patients.

Spinal Cord Compression Secondary to Epidural Bilharzioma: Case Report

A case of an epidural granuloma due to Schistosoma mansoni compressing the spinal cord at T7-T9 is presented. The patient, a 35-year-old Brazilian man, started complaining of recurrent back pain since 2003. A magnetic resonance imaging (MRI) scan showed a large epidural mass extending from T7 to T9 and causing mild spinal cord compression. Through a bilateral laminectomy the bilharzioma was subtotally removed without significant bleeding. The histopathology confirmed the diagnosis of granuloma due to S. mansoni. The patient recovered completely. Although the MRI is nonspecific, this differential diagnosis should be included in homogeneous epidural lesions without bone involvement, more than ever in endemic countries or during the evaluation of travelers to those regions.

Avaliação da concordância entre ressonância magnética de ultra-sonografia na classificação de fibrose periportal em esquitossomóticos, segundo a classificação de Niamey

OBJETIVO: Avaliar a reprodutibilidade da ressonância magnética e a concordância entre a ultra-sonografia e a ressonância magnética na classificação da fibrose periportal em pacientes esquistossomóticos, segundo os critérios qualitativos de Niamey. MATERIAIS E MÉTODOS: Foi realizado estudo prospectivo e duplo-cego, entre fevereiro de 2005 e junho de 2006, em 20 pacientes (10 homens e 10 mulheres, idades entre 24 e 60 anos, média de 42,75 anos) com diagnóstico de esquistossomose mansônica. As imagens de ultra-sonografia e de ressonância magnética foram avaliadas por dois examinadores experientes de forma independente. Foi medida a concordância interobservador para a ressonância magnética e entre a ressonância magnética e a ultra-sonografia. RESULTADOS: A ressonância magnética apresentou resultados concordantes entre os observadores em 14 pacientes (70%). Quando comparamos a ressonância magnética com a ultra-sonografia, obtivemos concordância em apenas seis pacientes pelo observador 1 (30%) e em oito pacientes pelo observador 2 (40%). CONCLUSÃO: A ressonância magnética tem boa reprodutibilidade na avaliação de fibrose periportal em pacientes com esquistossomose avançada, porém sua concordância com a ultra-sonografia é fraca.

Prevalence, intensity and associated morbidity of Schistosoma japonicum infection in the Dongting Lake region, China

OBJECTIVE

To determine the prevalence and intensity of Schistosoma japonicum infection and associated morbidity, and to estimate the infected human and buffalo populations in the Dongting Lake region, Hunan province, China.

METHODS

We used data from the third national schistosomiasis periodic epidemiological survey (PES) of 2004. These included 47 144 human serological and 7205 stool examinations, 3893 clinical examinations and questionnaire surveys, and 874 buffalo stool examinations, carried out in 47 villages in Hunan province. Serological examinations were performed using the enzyme linked immunosorbent assay technique and human stool samples were examined by the Kato-Katz method. Stools from buffaloes and other domestic animals were examined for schistosome infection by the miracidial hatching test.

FINDINGS

Sero-prevalence was 11.9% (range: 1.3-34.9% at the village level), and the rate of egg-positive stools was estimated at 1.9% (0-10.9%) for the same population. The prevalence of infection among buffaloes was 9.5% (0-66.7%). Extrapolating to the entire population of the Dongting Lake region, an estimated 73 225 people and 13 973 buffaloes were infected. Most frequently reported symptoms were abdominal pain (6.2%) and bloody stools (2.7%). More than half of the clinically examined people reported having had at least one prior antischistosomal treatment.

CONCLUSION

There was a significant reduction in the number of humans infected with S. japonicum since the previous national PES carried out in 1995, partially explained by large-scale chemotherapy campaigns. However, a near-stable number of buffalo infections suggest continuing human re-infection, which may lead to future increases in human prevalence.

Intrahepatic Cholangiocarcinoma with Old Infestation of Schistosoma japonicum: Report of a Case

We report a rare case of intrahepatic cholangiocarcinoma associated with old infestation of Schistosoma japonicum. The patient was a 76-year-old Japanese man who had lived his childhood in an endemic area of this parasite. He presented with jaundice and computed tomography showed a 4-cm, hypodense tumor in segment VIII of the liver. Microscopically, the resected mass was composed of well-differentiated adenocarcinoma cells. Fibrosis and inflammation were seen around the dilated peripheral portal veins embolized with dead S. japonicum eggs. Our search of the literature found only one other case of cholangiocarcinoma coincident with S. japonicum, suggesting that it is not a risk factor for cholangiocarcinoma, although the inflammation and fibrosis caused by the S. japonicum eggshells may predispose to carcinogenesis. However, there is no evidence supporting this hypothesis. More data are necessary to evaluate the differences in clinicopathological findings between cholangiocarcinoma concomitant with S. japonicum and the usual type of cholangiocarcinoma.

[Parasites as a cause of urticaria. Helminths and protozoa as triggers of hives?]

Urticaria is one of the most prevalent disorders in dermatological practice. The disease can be incapacitating. There are clear pathophysiological and epidemiological hints that helminths and protozoa are rare but treatable causes of acute and chronic urticaria. Doctors and patients are often not aware that parasitic diseases are increasingly common even in industrialized countries due to a steep rise in migration and international travel. This review presents the most important parasitic causes of urticaria and provides relevant details regarding personal history, clinical presentation, diagnosis and therapy.

Urinary schistosomiasis: an uncommon cause of gross hematuria in the industrialized countries

Schistosomiasis is a parasitic disease that can cause significant illness in humans. While schistosomiasis is not found in the United States and other developed countries, 200 million people are infected worldwide. It is estimated that 400,000 infected persons immigrate to the United States and present to emergency departments with either acute or chronic schistosomiasis. Schistosomiasis can be expected to be seen with increasing frequency in the United States and other developed countries with the continuing influx of immigrants, as well as the return of travelers and soldiers from endemic areas. Although there are several etiologies of gross hematuria in children, schistosomiasis is an uncommon cause of gross hematuria in the industrialized world. The purpose of this report is to bring awareness to health-care providers in the United States and other developed countries of this uncommon cause of gross hematuria, as prompt diagnosis and treatment can result in quick resolution of symptoms.

Eosinophilia: A study of 100 hospitalized patients

BACKGROUND

Eosinophilia accompanies a large number of diseases and conditions, but information is lacking about the clinical characteristics of patients who are hospitalized due to this abnormality. Our aim was to determine the clinical profile and most informative diagnostic tests in patients hospitalized in a tertiary hospital because of hypereosinophilia.

METHODS

A retrospective review was done of the medical records of all patients hospitalized in a large urban medical center due to hypereosinophilia. All relevant clinical, laboratory, and imaging data were analyzed.

RESULTS

A total of 100 patients were included in the study (58 males and 42 females, mean age 55.2+/-29 years). The blood eosinophil blood count was 4107+/-7254/mul (mean+/-SD) and this usually persisted for a few months. The cause of the eosinophilia was asthma or other atopic disease in 13% of the cases, allergic drug reaction in 6%, eosinophilic pneumonia in 10%, neoplastic diseases in 10%, idiopathic hypereosinophilic syndrome in 8%, Churg-Strauss Syndrome in 4%, infections in 10%, allergic fungal disease in 2%, and skin diseases in 3%; the cause remained unknown in 34% of cases.

CONCLUSION

Guidelines are suggested for the investigation of patients with eosinophilia, including the level of the eosinophilia associated with specific diseases and the most informative diagnostic tests.

Tracking the fate of iron in early development of human blood flukes

Iron (Fe) is an important trace element found in nearly all organisms, and is used as a cofactor in many biological reactions. One role for Fe in some invertebrates is in stabilization of extracellular matrices. The human blood fluke, Schistosoma japonicum, is responsible for significant human disease in developing and tropical nations. Disease in humans arises from host immunological reaction to parasite eggs that lodge in tissues. Schistosomes require Fe for development in their hosts, and store abundant Fe in vitelline (eggshell-forming) cells of the female system. The understanding of Fe metabolism and functionality are aspects of its biology that may be exploited in future therapeutics. The biology of Fe stores in vitelline cells of S. japonicum was investigated to illuminate possible functions of this element in early development of these parasites. Vitelline Fe is stored in yolk ferritin that is upregulated in females and is also expressed at low levels in egg-stages and adult males. Laser microdissection microscopy, coupled with reverse transcriptase- and real time-PCR amplification of schistosome ferritin sequences, confirmed that the vitelline cells are the likely progenitor cells of yolk ferritin. Assessment of Fe concentrations in whole male and whole female adult worms, eggs and purified eggshells by colorimetric assays and mass spectroscopy demonstrated higher levels of Fe in the female parasite, but also high levels of the element in whole parasite eggs and purified eggshell. Qualitative energy dispersive spectroscopy of purified eggshells, revealed that Fe is abundant in the eggshell, the matrix of which is composed of heavily cross-linked eggshell precursor proteins. Thus, vitelline stores of Fe are implicated in eggshell cross-linking in platyhelminths. These observations emphasise the importance of Fe in schistosome metabolism and egg formation and suggest new avenues for disruption of egg formation in these pathogenic parasites.

A specific viral cause of multiple sclerosis: One virus, one disease

"Multiple sclerosis is an autoimmune disease," is heard so often that it is widely accepted as fact by the current generation of students and physicians. Yet, although it is undisputed that multiple sclerosis (MS) is immune mediated, an autoimmune mechanism remains unproven. Immune-mediated tissue damage can also result from viral infections in which the host immune response is directed to viral rather than self proteins, or as a consequence of nonspecific or bystander immune responses that change the local cytokine environment. Increasing evidence suggests that poorly controlled host immune responses account for much of the tissue damage in chronic infections, and it has been postulated that a similar mechanism may underlie many chronic diseases with features suggestive of an infectious causative factor, including MS. A recent study suggesting that oligodendrocyte death accompanied by microglial activation is the primary event in new MS lesion formation, rather than lymphocyte infiltration, could change the current mindset almost exclusively focused on autoimmunity. This review presents the rationale for considering MS a single disease caused by one virus, as well as the anticipated pattern of a persistent central nervous system infection, the application of Koch's postulates to viral discovery in MS as the causative agent, and tissue culture-independent genotypic approaches to viral discovery in MS.

Katayama syndrome

Katayama syndrome is an early clinical manifestation of schistosomiasis that occurs several weeks post-infection with Schistosoma spp (trematode) worms. Because of this temporal delay and its non-specific presentation, it is the form of schistosomiasis most likely to be misdiagnosed by travel medicine physicians and infectious disease specialists in non-endemic countries. Katayama syndrome appears between 14-84 days after non-immune individuals are exposed to first schistosome infection or heavy reinfection. Disease onset appears to be related to migrating schistosomula and egg deposition with individuals typically presenting with nocturnal fever, cough, myalgia, headache, and abdominal tenderness. Serum antibodies and schistosome egg excretion often substantiate infection if detected. Diffuse pulmonary infiltrates are found radiologically, and almost all cases have eosinophilia and a history of water contact 14-84 days before presentation of clinical symptoms; patients respond well to regimens of praziquantel with and without steroids. Artemisinin treatment given early after exposure may decrease the risk of the syndrome.

Vaccines against the zoonotic trematodesSchistosoma japonicum,Fasciola hepaticaandFasciola gigantica

Schistosoma japonicum,Fasciola hepaticaandF. giganticaare digenetic trematodes and, therefore, possess similar life cycles. While schistosomiasis japonica has for a long time been recognised as a major disease of both humans and animals, infection with fasciolids has only been considered of relevance to animals. However, a number of recent reports indicate that fasciolosis is becoming a serious public health problem, especially in South America, Egypt and Iran (sporadic cases are also on the increase throughout Europe). Vaccines targeted at animals could play an important role in controlling these three diseases in animals and, by blocking transmission of infection, have a concurrent beneficial effect on disease in humans. Approaches towards identifying and producing vaccines against these parasites are similar and are discussed in this reveiw.

Conservation of CD4+ T cell-dependent developmental mechanisms in the blood fluke pathogens of humans

Schistosoma blood flukes are trematode parasites with a cosmopolitan distribution that infect over 200 million people globally. We previously showed that Schistosoma mansoni growth and development in the mammalian host is dependent on signals from host CD4+ T cells. To gain insight into the mechanisms that underlie this dependence, we sought to determine the evolutionary origins and limits of this aspect of the host-pathogen relationship. By infecting RAG-1-/- mice with a range of different schistosome species and strains, we tested several hypotheses concerning the time during Schistosoma evolution at which this dependence arose, and whether this dependence is specific to Schistosoma or is also found in other blood flukes. Our data indicate that the developmental dependence on CD4+ T cells previously described for S. mansoni is conserved in the evolutionarily basal species Schistosoma japonicum, suggesting this developmental adaptation arose early in Schistosoma evolution. We also demonstrate that the development of the more evolutionarily derived species Schistosoma haematobium and Schistosoma intercalatum are dependent on adaptive immune signals. Together, these data suggest that the blood fluke parasites of humans utilise common mechanisms to infect their hosts and to co-opt immune signals in the coordination of parasite development. Thus, exploitation of host-schistosome interactions to impair or prevent parasite development may represent a novel approach to combating all of the schistosome pathogens of humans.

Sigmoid colonic carcinoma associated with deposited ova of Schistosoma japonicum: A case report

We report a case of sigmoid colonic carcinoma associated with deposited ova of Schistosoma japonicum. A 57-year old woman presented with a 10-mo history of left lower quadrant abdominal pain and a 2-mo history of bloody stools. She had a significant past medical history of asymptomatic schistosomiasis japonica and constipation. A colonoscopy showed an exophytic fragile neoplasm with an ulcerating surface in the sigmoid colon. During the radical operative procedure, we noted the partially encircling tumor was located in the distal sigmoid colon, and extended into the serosa. Succedent pathological analysis demonstrated the diagnosis of sigmoid colonic ulcerative tubular adenocarcinoma, and showed deposited ova of Schistosoma japonicum in both tumor lesions and mesenteric lymph nodes. Three days after surgery the patient returned to the normal bowel function with one defecation per day. These findings reveal that deposited schistosome ova play a possible role in the carcinogenesis of colorectal cancer.

Functional epistasis on a common MHC haplotype associated with multiple sclerosis

Genes in the major histocompatibility complex (MHC) encode proteins important in activating antigen-specific immune responses. Alleles at adjacent MHC loci are often in strong linkage disequilibrium; however, little is known about the mechanisms responsible for this linkage disequilibrium. Here we report that the human MHC HLA-DR2 haplotype, which predisposes to multiple sclerosis, shows more extensive linkage disequilibrium than other common caucasian HLA haplotypes in the DR region and thus seems likely to have been maintained through positive selection. Characterization of two multiple-sclerosis-associated HLA-DR alleles at separate loci by a functional assay in humanized mice indicates that the linkage disequilibrium between the two alleles may be due to a functional epistatic interaction, whereby one allele modifies the T-cell response activated by the second allele through activation-induced cell death. This functional epistasis is associated with a milder form of multiple-sclerosis-like disease. Such epistatic interaction might prove to be an important general mechanism for modifying exuberant immune responses that are deleterious to the host and could also help to explain the strong linkage disequilibrium in this and perhaps other HLA haplotypes.

Human schistosomiasis

Schistosomiasis or bilharzia is a tropical disease caused by worms of the genus Schistosoma. The transmission cycle requires contamination of surface water by excreta, specific freshwater snails as intermediate hosts, and human water contact. The main disease-causing species are S haematobium, S mansoni, and S japonicum. According to WHO, 200 million people are infected worldwide, leading to the loss of 1.53 million disability-adjusted life years, although these figures need revision. Schistosomiasis is characterised by focal epidemiology and overdispersed population distribution, with higher infection rates in children than in adults. Complex immune mechanisms lead to the slow acquisition of immune resistance, though innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is mostly seen in travellers after primary infection. Chronic schistosomal disease affects mainly individuals with long-standing infections in poor rural areas. Immunopathological reactions against schistosome eggs trapped in the tissues lead to inflammatory and obstructive disease in the urinary system (S haematobium) or intestinal disease, hepatosplenic inflammation, and liver fibrosis (S mansoni, S japonicum). The diagnostic standard is microscopic demonstration of eggs in the excreta. Praziquantel is the drug treatment of choice. Vaccines are not yet available. Great advances have been made in the control of the disease through population-based chemotherapy but these required political commitment and strong health systems.