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.

Epidemiological, clinical and laboratory features of toxocariasis in school children from Aragua State, Venezuela.

Background: Toxocariasis is a widespread zoonosis caused by canine and feline Toxocara spp. In Venezuela, seroepidemiological studies in Aragua State have been carried out only in preschool children. The objective of this study was to determine the prevalence of anti-Toxocara spp. antibodies and identify clinical symptoms and risk factors of Toxocara spp. infection in school children in two municipalities of Aragua State of Venezuela. Methods: A cross-sectional field study with 259 children between 6 and 12 y of age was conducted in six schools in Aragua State. Immunoglobulin G antibodies against Toxocara spp. by enzyme-linked immunosorbent assay, haematology and eosinophil counts were detected in blood. Participating families filled in a questionnaire and studied children were clinically evaluated by paediatricians. Results: Anti-Toxocara spp. antibodies were detected in 14.3% of children. The seroprevalence in the schools studied ranged from 4.4% to 24.1%. Statistical associations with eosinophilia, decreased visual acuity, eyestrain, headache and paleness were found. Significant risk factors were contact with dogs, playing with dogs and playing with soil. Conclusions: The identification of risk factors and their association with infection suggest that the infection is a problem in the municipalities studied, so screening for toxocariasis in school children should be recommended.