Pre- and post-treatment immunodiagnostic evaluation in human schistosomiasis mansoni

Abstract

Schistosomiasis control seems to be different in countries were low parasitic burden and asymptomatic clinical patients are the features of majority of cases. Immunological methods must substitute the traditional coprologic techniques used for some decades in the Control Program. Circumoval Precipitin Test (COPT), intradermal test and ELISA with soluble egg antigen (SEA) are evaluated for using as tools for seroepidemiologic studies. COPT and ELISA were performed after treatment to known their utility when impact of chemotherapy must be assessed. One hundred sixty five persons were followed up 3, 6, 9 and 12 months after treatment. The mean sensitivity of COPT studied by age groups was 95.6% which is very important considering that 88.4% of the studied population excreted less than 100 eggs/gr of feces, while sensitivity of intradermal test was 58.2%. Children showed the highest reactivity to COPT. When treatment is effective, COPT reactivity progressively diminish until become negative one year later. In the non cure group, the COPT reactivity diminished but never below 20%. ELISA-SEA did not modify one year after treatment. Effort should be made to isolate fractions of eggs of Schistosoma mansoni whose antibodies disappear after treatment.

Laboratory diagnosis of Schistosomiasis in areas of low transmission: a review of a line of research

“…The gold standard diagnostic test: the circummoval precipitine test (COPT) -Based on the low sensitivity obtained (Mott & Cline 1980) by the classical Kato-Katz (Katz et al 1972) in areas of low transmission, the COPT (Oliver-González 1954) revealed the best performance, reaching a range of sensitivity of 92-100% and specificity of 96-100% (Spencer et al 1991, Alarcón de Noya et al 1992a). Purified S. mansoni eggs were incubated with patients sera for 48 h at 37°C.…”

“…Additionally, it is the only test based on the detection of antibodies that correlates with parasite activity (Hillyer et al 1979). Antibodies against the excretory-secretory antigens released by eggs, starts to decline three months after successful chemotherapy (Alarcón de Noya et al 1992a).…”

“…In countries as Venezuela, in which approximately 80% of the individuals harbor light infections (elimination of < 100 eggs/g of feces), with mild morbidity, being the majority of the population asymptomatic, the detection of infected individuals is difficult (Alarcón de Noya et al 1999). Under this condition, the sensitivities of the stool examination by Kato-Katz and the available serological methods based on the detection of circulating antigens decrease to 60% also (Alarcón de Noya et al 1992a, El-Morsmedy et al 1996. Tests based on the detection of antibodies have been improved and so far these are the best tools in epidemiological and clinical screenings (Alarcón de Noya et al 1997).…”

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

“…The COPT, in spite of its high sensitivity and specificity, and its correlation with oviposition, remains only as a confirmatory diagnostic test, because it is very laborious and depends on ongoing life cycle . COPT value decreases slowly after treatment, becoming negative from six months to one year after effective chemotherapy (Alarcón de Noya et al 1992a).…”

The Last Fifteen Years of Schistosomiasis in Venezuela: Features and Evolution

“…COPT continues to be our gold standard technique due to its high sensitivity, specificity and correlation with active cases (Alarcón de Noya et al 1992d). The COPT prevalence in cross-sectional studies is shown in Table III.…”