Circumoval Precipitin Research Articles

A Review on the Immunological Techniques Use for Detection of Schistosoma spp Infection

Over 200 million people are suffering from the debilitating schistosomiasis, which has the greatest morbidity and mortality rates in African nations. Schistosomiasis continues to be a tropical disease that receives little attention from governments and healthcare Institutions while having a wide range of negative impacts on society's health and socioeconomic hardship. The establishment of precise investigation for both gut and urinary schistosomiasis is one of the crucial areas that are severely undeveloped. A review was conducted to highlight immunological methods used to detect Schistosomiasis. Databases from ScienceDirect, World Health Organization, and PubMed were used. Articles for which at least the abstract was available in English were selected for the present study. Relevant articles were screened, duplicates were eliminated, eligibility standards were followed, and qualified studies were reviewed. Techniques including Skin Reaction Test/Biopsy, Indirect Immuno-Fluorescence Test (IFT), Indirect Hemagglutination Test (IHAT), Circumoval Precipitin Test (Copt), Monoclonal Antibodies Test (Mabt), ELISA, and others were discussed. The challenges faced by these techniques were also highlighted. Among the techniques discussed, ELISA was found to be the most widely used as it is the most effective, easy to use, and could detect both chronic and acute Schistosomiasis

Diagnostic performance of parasitological, immunological and molecular tests for the diagnosis of Schistosoma mansoni infection in a community of low transmission in Venezuela

In Venezuela, areas endemic for schistosomiasis are of low transmission, with low parasite loads. Immunological tests often lack specificity and cannot differentiate past from present infections. Molecular tests are an alternative, although validation studies in endemic areas are needed. The aim of this study was to determine the performance of parasitological, immunological and molecular tests for the diagnosis of Schistosoma mansoni infection in low-transmission settings. A cross-sectional study was carried out in a rural community located in a schistosomiasis-endemic area of Venezuela to determine the prevalence and diagnostic performance of the Kato-Katz (KK) technique, Circumoval Precipitin Test (COPT), ELISA based on soluble egg antigen (ELISA-SEA) with and without treatment with sodium metaperiodate (ELISA-SEA-SMP), and PCR for amplification of the 121 bp highly repeated sequence of Schistosoma mansoni in faeces, urine and serum samples. The highest prevalence rates were obtained with ELISA-SEA (38.7%), COPT (33.3%), ELISA-SEA-SMP (31.5%), PCR on faeces (21.6%), and KK (17.1%), whereas PCR-based prevalence in urine was 6.2% and no positivity was detected in serum samples. Results showed that ELISA-SEA is the best method for the diagnosis of both current and former infections and that PCR on faeces is the best method for detecting recent transmission. The use of different tests that complement one another also allowed for a better diagnosis of Schistosoma mansoni infection, revealing a relatively high prevalence (33.8%) of schistosomiasis in a community of low transmission.

Proteomic and immunomic analysis of Schistosoma mekongi egg proteins

Schistosomiasis remains a global health problem. In the Mekong river basin, approximately 80,000 people are at risk of infection by Schistosoma mekongi. The parasite's eggs become entrapped in the host's organs and induce massive inflammation, contributing to the pathogenesis of schistosomiasis. In addition, egg antigens are important in circumoval precipitin tests (COPTs) and other diagnostic techniques. Little is known regarding the egg proteins of S. mekongi, and so we applied immunoblotting and mass spectrometry-based proteomic approaches to study these proteins and their antigenicity. A total of 360 unique proteins were identified in S. mekongi eggs using proteomic analyses. The major protein components of S. mekongi eggs were classified into several groups by functions, including proteins of unknown function, structural proteins, and regulators of transcription and translation. The most abundant proteins in S. mekongi eggs were antioxidant proteins, potentially reflecting the need to neutralize reactive oxidative species released from host immune cells. Immunomic analyses revealed that only DNA replication factor Cdt1 and heat shock protein 70 overlap between the proteins recognized by sera of infected mice and humans, illustrating the challenges of knowledge transfer from animal models to human patients. Forty-one immunoreactive protein bands were recognized by either mouse or patient sera. Phosphoglycerate kinase, fructose-1,6-bisphosphate aldolase and elongation factor 1 appeared to be interesting immunogens of S. mekongi eggs as these proteins were recognized by polyclonal IgMs and IgGs in patient sera. Our findings provide new information on the protein composition of S. mekongi eggs as well as the beginnings of a S. mekongi immunogen dataset. These data may help us better understand the pathology of schistosomiasis as well as natural antibody responses against S. mekongi egg proteins, both of which may be useful in including S. mekongi to other schistosoma diagnostic, vaccine and immunotherapy development.

Long-term effect of mass chemotherapy, transmission and risk factors for Schistosoma mansoni infection in very low endemic communities of Venezuela

The prevalence of Schistosoma mansoni infection in Venezuela has changed from high to low due mostly to successful control activities, including mass chemotherapy and molluscicide applications. This study examined the impact of mass chemotherapy on S. mansoni transmission and risk factors for infection 12 years after administration of praziquantel in Venezuela. Two relatively isolated rural communities were studied, one with snail control (Manuare) and the second without (Los Naranjos). A cross-sectional survey of randomly selected households included 226 (Manuare) and 192 (Los Naranjos) consenting participants. S. mansoni prevalence was determined using a combination of coprological (Kato-Katz) and serological (circumoval precipitin test, alkaline phosphatase immunoassay and Western blot) tests. Data on epidemiological and socioeconomic risk factors were obtained through individual structured interviews. Univariate analysis and multivariate logistic regression models identified independent risk factors for infection. Water sites were examined for the presence of Biomphalaria glabrata snails. Only one participant was positive by coprology. The overall prevalences according to the combined tests were 32.7% in Manuare and 26.6% in Los Naranjos. Lower prevalences (12.7% in Manuare and 13.2% in Los Naranjos) were found in children <12 years of age representing those born after mass chemotherapy. Social demographic variables associated with infection in both communities were older age (>25 years), contact with specific water sites, and being a farmer/non-specialised worker. Mass treatment with praziquantel applied once to endemic communities led to an important and long-lasting sustained reduction of S. mansoni infections independent of the application of snail control. A degree of low active transmission of S. mansoni persisted in the treated areas which was associated with similar factors in both communities.

Detection of Schistosoma mansoni infection by TaqMan® Real-Time PCR in a hamster model

An experimental study in hamsters was performed to evaluate the capability for detecting Schistosoma mansoni DNA in serum and fecal samples during the pre and post-egg-laying periods of infection using TaqMan® Real-Time PCR system (qPCR), was compared with the circumoval precipitin test (COPT) and the Kato-Katz technique, especially among individuals with low parasitic burden. Twenty-four hamsters were infected with cercariae. Three hamsters were sacrificed per week under anesthesia, from 7days post infection (DPI) up to 56 DPI. A serum sample and a pool of feces were collected from each hamster. The presence of S. mansoni eggs in fecal samples was evaluated by Kato-Katz method and in the hamsters gutby histopathology. Detection of S. mansoni DNA was performed using qPCR and S. mansoni antibody using COPT. The first detection of eggs in feces by Kato-Katz method and S. mansoni DNA in feces by qPCR occurred 49 DPI. Nevertheless, S. mansoni DNA was detected in serum samples from 14 up to 56 DPI. COPT was positive at 35 DPI. The results not only confirm the reliability of S. mansoni DNA detection by qPCR, but also demonstrate that serum is a trustworthy source of DNA in the pre patent infection period.

New endemic foci of schistosomiasis infections in the Philippines

Schistosomiasis affects 28 provinces in the Philippines found along the southeastern part where there is continuous rainfall throughout the year. In 2002 and 2005 respectively, two new endemic foci were reported in the northernmost (Gonzaga, Cagayan) and central (Calatrava, Negros Occidental) parts of the country.This study conducted in March 2008–March 2009 confirmed the presence of the disease by determining its prevalence using four diagnostic tests – Kato-Katz, circumoval precipitin test (COPT), ELISA and ultrasonography. Oncomelania hupensis quadrasi was identified through snail surveys conducted in possible snail habitats in the seven new endemic villages. Animal surveys through stool examination confirmed the presence of schistosomiasis infection in animals in Gonzaga but not in Calatrava.Compared to Calatrava, Gonzaga demonstrated markedly higher prevalence of schistosomiasis using all four diagnostic methods. Proximity of snail habitats to human habitation including higher snail density and snail infection rate could be responsible for the high prevalence. Snail sites were more widespread in Gonzaga whereas those in Calatrava were confined only in areas not frequented by the general population except by farmers. GIS maps showing spatial distribution of snails in Gonzaga and Calatrava indicated differences in elevation among the snail sites.It is hypothesized that the snail intermediate host has been in these sites for sometime but discovered only lately. Migration of people from endemic provinces into Gonzaga and Calatrava brought in cases and in the presence of snail intermediate hosts, emergence of disease was just a matter of time.

Proteomic analysis of Schistosoma mansoni egg secretions

Schistosomiasis remains a largely neglected, global health problem. The morbid pathology of the disease stems from the host's inflammatory response to parasite eggs trapped in host tissues. Long term host/parasite survival is dependent upon the successful modulation of the acute pathological response, which is induced by egg antigens. In this study, using Multidimensional Protein Identification Technology, we identified the Schistosoma mansoni egg secretome consisting of 188 proteins. Notably we identified proteins involved in redox balance, molecular chaperoning and protein folding, development and signaling, scavenging and metabolic pathways, immune response modulation, and 32 novel, previously uncharacterized schistosome proteins. We localized a subset of previously characterized schistosome proteins identified in egg secretions in this study, to the surface of live S. mansoni eggs using the circumoval precipitin reaction. The identification of proteins actively secreted by live schistosome eggs provides important new information for understanding immune modulation and the pathology of schistosomiasis.

Detection of schistosomiasis cases in low-transmission areas based on coprologic and serologic criteria: The Venezuelan experience

Low and very-low intensities of infection hinder the diagnosis of schistosomiasis. Therefore, new parameters should be established in order to more accurately identify active cases and true infection prevalence, for the adequate implementation of a control program. After the survey and analysis of the epidemiological characteristics of five Venezuelan communities, we propose three criteria for the definition of a “schistosomiasis case”, based on different diagnostic methods: stool examination, ELISA-soluble egg antigen with sodium metaperiodate (SMP–ELISA), alkaline phosphatase immunoassay (APIA) and the circumoval precipitin test (COPT). Briefly, criterion I: persons with Schistosoma mansoni eggs in stools; criterion II: persons without eggs in stools, with positive COPT, without previous antischistosome chemotherapy in the last year; and criterion III: persons without eggs in stools, with negative COPT, with two positive immunoenzymatic tests (SMP–ELISA and APIA), and with no previous chemotherapy. The incorporation of serological tests to epidemiologic surveillance in areas of low-transmission tries to compensate the underestimation of prevalence based only on parasitological diagnosis.

Low transmission areas of schistosomiasis in Venezuela: consequences on the diagnosis, treatment, and control

Schistosomiasis low transmission areas as Venezuela, can be defined as those where the vector exists, the prevalence of active cases is under 25%, individuals with mild intensity of infection predominate and are mostly asymptomatic. These areas are the consequence of effective control programs, however, "silent" epidemiological places are difficult to trace, avoiding the opportune diagnosis and treatment of infected persons. Clinic and abdominal ultrasound have not shown to discriminate infected from uninfected persons in areas where besides Schistosoma mansoni, intestinal parasites are the rule. Under these conditions, serology remains as a very valuable diagnostic tool, since it gives a closer approximation to the true prevalence. In this sense, circumoval precipitin test, ELISA-SEA with sodium metaperiodate, and alkaline phosphatase immunoassay joined to coprology allow the identification of the "schistosomiasis cases". In relation to public health, schistosomiasis has been underestimated by the sanitary authorities and the investment on its control is being transferred to other diseases of major social and political relevance neglecting sanitary efforts and allowing growth of snail population. Some strategies of diagnosis and control should be done before schistosomiasis reemergence occurs in low transmission areas.

The efficacy of human schistosomicide treatment may depend on the rate of transmission

The efficacy of different treatment protocols in humans infected with Schistosoma mansoni at sites with different transmission conditions was evaluated by the disappearance of anti-worm intestine IgM antibodies in an indirect fluorescence antibody test (IgM-IFT) and anti-egg antibodies in the circumoval precipitin test (COPT). Patient sera coming from sites of active low transmission (ALT), active high transmission (AHT) and low interrupted transmission (LIT) from Venezuela were studied. Chemotherapy protocols were (1) ALT, 60 mg/kg praziquantel (Pzq60); (2) AHT, one dose of 40 mg/kg Pzq followed by one dose of 20 mg/kg oxamniquine for one group and one dose of 40 mg/kg Pzq alone for the other group; (3) LIT, one dose of 40 mg/kg Pzq repeated every 3 months up to three doses. Cure rates occurred mostly between 3 and 12 months with the exception of Pzq60-ALT where it was evident before 3 months. Higher cure rates were evident in both places of low transmission (ALT and LIT) and the lowest in the AHT regardless of the treatment protocol. Cure was more evident with COPT compared to IgM-IFT. The rate of serological cure appears then to depend on the previous state of transmission. The differential cure rate evaluated by both techniques is probably due to the persistence of antibodies against antigens in different stages of the parasite.

Development of a rapid, sensitive, dye immunoassay for schistosomiasis diagnosis: a colloidal dye immunofiltration assay

The colloidal dye immunofiltration assay (CDIFA) combines the concepts of the double-antigen sandwich assay, the Dot immunofiltration assay, and colloidal dye-linked antigen technique to produce a new dye immunoassay for antibody detection in schistosomiasis. The CDIFA consisted of soluble egg antigen (SEA) of Schistosoma japonicum coated onto nitrocellulose membrane, mounted on a flow-through test device to provide the assay capture matrix. SEA absorbed to a red colloidal dye, R-3, produced in China, served as the antigen–antibody complex detecting reagents. The results showed that the sensitivity of the CDIFA was 100% in 35 cases of acute schistosomiasis (35/35), 98% in 50 cases of chronic schistosomiasis (49/50). The specificity of the assay was 99.4% in 180 healthy individuals (179/180). The cross-reaction was 13.3% in 30 cases of paragonimiasis, 2.6% in 38 cases of clonorchiasis sinensis and 0% in 20 cases of hookworm infection, 20 cases of fasciolopsiasis and 16 cases of ascariasis. The results were similar to those detected by routine enzyme-linked immunosorbent assay (ELISA). In a field evaluation of the CDIFA kit, the positivity rate of the CDIFA was 97.5% in 157 cases of schistosomiasis, compared with 91.1% with the circumoval precipitin test (COPT). The dye-labeled SEA conjugate was stable at room temperature for at least 6 months. The results indicated that the CDIFA provided an economic, simple, rapid, robust test for the detection of schistosome infection, suitable for a wide variety of field applications without any instrumentation.

Molecular and enzymatic characterisation of Schistosoma mansoni thioredoxin

Defense against oxidative damage can be mediated through glutathione and/or thioredoxin utilising systems. Here, we report the identification and characterisation of a thioredoxin from Schistosoma mansoni. The predicted protein has similarity to previously characterised thioredoxins including conservation of the redox active site. Recombinant six-histidine tagged schistosome thioredoxin had insulin reduction activity and supported the enzymatic function of thioredoxin reductase and thioredoxin peroxidase. By Western blotting, all mammalian stages of the schistosome lifecycle expresses thioredoxin. Thioredoxin is present in egg secretory products and antibodies against the recombinant protein produce the circumoval precipitin reaction. This is the first identification of defined antigen producing this reaction. Furthermore, thioredoxin is a novel egg immunogen as it elicits an antibody response in schistosome-infected mice. The most significant IgG production against thioredoxin occurs after parasite oviposition commences. These observations suggest that thioredoxin participates in processes vital to the parasite and may facilitate the passage and survival of eggs across inflamed host tissues.

Development of a rapid, simple dipstick dye immunoassay for schistosomiasis diagnosis

In order to develop a rapid, simple immunodiagnostic assay for schistosomiasis, soluble egg antigen (SEA) of Schistosoma japonicum was conjugated with a blue colloidal dye (D-1) produced in China and used to detect antibodies in the sera of schistosomiasis patients. The antigen–antibody complex was captured by anti-human IgG absorbed onto a nitrocellulose membrane dipstick by means of immunochromatography. The results showed that the sensitivity of the dipstick dye immunoassay (DDIA) was 96.7% in 30 cases of acute schistosomiasis (29/30) and 94.1% (79/84) in 84 cases of chronic schistosomiasis. The specificity of the assay was 96.7% in 60 healthy subjects. Cross-reactions were observed in 10.0% of 20 cases of clonorchiasis and in 70.0% of 20 cases of paragonimiasis. The results were similar to those detected by routine ELISA. In a field evaluation of the DDIA kit, the positive rate of the DDIA was 96.7% in 121 cases of schistosomiasis, compared with 90.1% with the circumoval precipitin test (COPT) . The antigen conjugated with dye was stable at room temperature for at least 6 months. The results indicated that the dipstick dye immunoassay provided high sensitivity and good specificity for the detection of schistosomiasis and the assay was rapid, simple and cheap, and did not need any equipment. It was more useful for screening target populations for selective chemotherapy than other immunoassays.

Seroepidemiology of schistosomiasis in Puerto Rico: evidence for vanishing endemicity.

The current study summarizes our findings of anti-schistosome egg antibody by the circumoval precipitin test for two different populations in Puerto Rico. One group, exclusively males more than 40 years of age and from all municipalities on the island, was from the Veterans Administration Hospital for the period 1988-1997. The second group resided southeast of San Juan, around the municipality of Caguas and adjacent municipalities east of Caguas, was of both sexes and mostly until 1997 of undetermined ages for the period 1993-1997. Results reveal a yearly decrease in testing requests from the Veterans Administration Hospital from 148 in 1988 and 1989 with 16% positive to three in 1996 through 1998 with none positive. This decrease in testing requests was because of a decrease of suspicion of schistosomiasis in this group. The other patient population from the Caguas region showed a gradual but continuous decrease in seropositive individuals from 21% in 1993 to 12% in 1996, with precipitous decrease to 5% in 1997 and only 1% in 1998. Moreover, there were four patients from which at least two serum samples were obtained one or two years apart and tested. In each instance the more recently obtained sample had lower antibody reactions than the first as reflected in lower percentages of positive egg reactors. The fact that they were treated with praziquantel after the first testing also suggests that the infected population was being eliminated through chemotherapy. These combined results suggest the elimination of infections with Schistosoma mansoni in the traditionally high prevalence regions east of San Juan in the absence of any proactive control efforts in Puerto Rico. Because of the rapid urbanizing of Puerto Rico, the one identifiable control effort is economic development and well being.

Evaluation of alkaline phosphatase immunoassay and comparison with other diagnostic methods in areas of low transmission of schistosomiasis

The alkaline phosphatase immunoassay (APIA) is an antibody detection technique which permits the diagnosis of schistosomiasis using a butanolic extract preparation from adult worms. APIA has demonstrated high sensitivity and specificity in previous reports with well characterized human sera. Its potential as a diagnostic tool for epidemiological surveillance was assessed in comparison with three other diagnostic tests: stool examination, ELISA with soluble egg antigen (SEA) and the circumoval precipitin test (COPT). APIA was 100% specific in an area without Schistosoma mansoni transmission and had 89% sensitivity in an endemic area where 69% of the infected subjects excreted less than 100 eggs/g of faeces. It was found to be less sensitive in children under 5 years of age who were positive by the COPT test. APIA can be applied as an initial screening test, based on its high sensitivity, specificity, absence of cross-reactivity with intestinal parasites and the fact that it is a technique suitable for use in epidemiological surveillance.

Characterization of Schistosoma japonicum specific egg antigen recognized by circumoval precipitin (COP) producing monoclonal antibodies

In order to analyze the antigens concerned with circumoval precipitin (COP) reactions, four monoclonal antibodies (18-4-1, 56-8-38, 85-16-1, 48-39-2) were obtained from spleen cells of mice infected with Schistosoma japonicum. All four gave positive COP reactions against S. japonicum eggs. All except 18-4-1, however, also reacted with S. mansoni eggs. Monoclonal antibodies 18-4-1 and 48-39-2 reacted specifically with schistosome egg antigens but not with antigens derived from adult schistosomes and 10 other species of helminths in enzyme-linked immunosorbent assay (ELISA), suggesting that these antibodies have high specificity and would be useful for characterization of the antigens concerned with COP reactions. The egg antigens recognized by antibodies 18-4-1 and 48-39-2 were identified by immunoblotting. Antibody 18-4-1 reacted only with S. japonicum egg antigens of mol. wt. 330 and 360 kDa, while 48-39-2 reacted with S. japonicum egg antigens of mol. wt. ranging from 58 to 265 kDa and with S. mansoni egg antigens of mol. wt. 62 kDa. The epitope recognized by 18-4-1 can be regarded as carbohydrate and peptide, whereas that recognized by 48-39-2 appears to be only carbohydrate. The COP antigens characterized by antibodies 18-4-1 and 48-39-2 have not been identified so far, on the grounds of differences in their specificity and molecular weight from those in previous reports.

The immunopathology of human Schistosomiasis-III. Immunoglobulin isotype profiles and response to praziquantel.

Immunoglobulin (Ig) isotype (IgG, IgG1, IgG2, IgG3, IgG4, IgM, IgD and IgE) levels were investigated, both pre- and post-treatment with praziquantel (PZQ), in 43 adults and children chronically infected with Schistosoma mansoni, by means of a two-site, isotype-specific immunoenzymometric assay. The patients were classified as responders (R) or non-responders (NR) on the basis of their circumoval precipitin test (COPT) results 12 months after treatment. In comparison with controls, pre-treatment R children showed significantly higher levels of IgG, IgG1, IgG4 (p < 0.001) and IgE (p < 0.01); and diminished IgG2 (p < 0.05), while NR children showed significantly elevated levels only of IgE (p < 0.05). Twelve months after therapy, R children maintained significantly lower levels of IgG2, but showed significantly decreased levels of IgG, IgG1, IgG4, and IgE, while the Ig isotype profile of NR children was unaltered. Adult R and NR showed similar isotype profiles before chemotherapy, with the exception of significantly elevated IgM levels in R. Twelve months after therapy, R adults showed significantly decreased levels of IgG, IgG1, and IgG4, while NR adults showed only diminished IgG4 levels. These results reveal different Ig isotype profiles in untreated adults and children chronically infected with S. mansoni. The results further show that the pre-treatment Ig isotype profile may be significantly modified after an effective R to chemotherapy, accounted for by down regulation of the IgG1 isotype in association with negative seroconversion of the COPT in R patients. The COPT reaction has been associated with the highly specific egg glycoprotein antigen omega 1, which shows a significant reduction in reactivity six months after treatment. IgG1 may thus play a main role in the response against the omega 1 antigen.

Effect of chemotherapy on immune response to egg antigens of Schistosoma mansoni in chronically infected children from areas of low transmission.

In an attempt to identify antigenic molecules from Schistosoma mansoni eggs, a serological study was performed on children of a Venezuelan town (Caraballeda) in which the transmission of schistosomiasis had been interrupted two years prior to sera sampling. Infected children received treatment with Praziquantel and, based on the disappearance of eggs in the stools plus negativization of the circumoval precipitin test (COPT) one year after treatment, they were classified as either responders or non-responders to chemotherapy. Western blots of soluble egg antigen (SEA) with a very sensitive chemiluminescent substrate were performed. Sera from responder children recognized a 25 kDa band of SEA which diminished significantly after treatment. This was less frequent in non-responder children. When the sera of responder and non-responder children were compared before treatment, we found that the recognition of the 40 and 41 kDa proteins could be predictive of response to chemotherapy. All these antigens, used in ELISA-type techniques, might be of importance in the evaluation and follow-up of large scale schistosome control programmes.

Schistosome circulating anodic antigen in serum of individuals infected with Schistosoma japonicum from The Philippines before and after chemotherapy with praziquantel

The presence of the schistosome circulating anodic antigen (CAA) in serum of patients infected with Schistosoma japonicum from The Philippines has been investigated using an enzyme-linked immunosorbent assay ( elisa). Serum samples were tested from 48 patients who excreted S. japonicum eggs, 9 individuals with a negative stool examination, and 20 controls with both a negative stool and a negative circumoval precipitin test. No false positive result was detected for the unequivocally negative controls. CAA could be demonstrated in 72·9% of the egg-excreting patients. A positive correlation between parasite burden (eggs per gram of faeces) and antigen level (CAA titre) was found (Spearman's ϱ = 0·48, P < 0·001, n = 48). Four of 18 sera from the egg-negative individuals were positive in the elisa. In view of the fact that anti-worm antibodies were also detected in these 4 sera, those reactions suggest active infection not detected by stool examination. In serum from patients treated with praziquantel, a significant drop in CAA titre was seen within 5 d after treatment (Wilcoxon's x T = −2·23, P = 0·0258, n = 21). In conclusion, the detection of CAA by elisa in S. japonicum infection can give valuable information in both individual diagnosis and therapeutic drug monitoring, as well as in epidemiological studies or disease control programmes.

New approaches for the control and eradication of schistosomiasis in Venezuela.

Schistosomiasis in America with the exception of Brazil, behaves as a chronic mild disease with few clinical manifestations due to low parasite burden. These features restrict the clinical and parasitological diagnosis. The most commonly used stool examination method, Kato-Katz, becomes insensitive when the majority of individuals excrete less than 100 eggs/g of feces. In view that antigen-detecting techniques have not been able to reveal light infections, the antibody detecting assays remain as a very valuable diagnostic tool for epidemiological surveillance. The Venezuelan Schistosomiasis Research Group (CECOICE) has designed a mass chemotherapy strategy based on sero-diagnosis. Since blood sampling is one of the important limiting factors for large seroepidemiological trials we developed a simple capillary technique that successfully overcame most of the limitations of blood drawing. In this sense, ELISA seems to be the most adequate test for epidemiological studies. Soluble egg Schistosoma mansoni antigen (SEA) has been largely used in Venezuela. The sensitivity of ELISA-SEA in our hands is 90%, moreover its specificity reach 92% when populations from non-endemic areas but heavily infected with other intestinal parasites are analyzed. The Schistosomiasis Control Program is currently carrying out the surveillance of endemic areas using ELISA-SEA as the first screening method, followed by the Circumoval Precipitin test for validation assay. The results with these two serological techniques allowed us to defined the criteria of chemotherapy in populations of the endemic areas. On the search of better diagnostic technique, Alkaline Phosphatase Immunoenzyme Assay (APIA) is being evaluated in field surveys.