Laboratory diagnosis of Schistosomiasis in areas of low transmission: a review of a line of research.
After 57 years of successful control of schistosomiasis in Venezuela, the prevalence and intensity of infection have declined. Approximately 80% of the individuals eliminate less than 100 eggs/g of stools, therefore morbidity is mild and the majority are asymptomatic. The sensitivity of Kato-Katz decreases to approximately 60%. Available serological methods for the detection of circulating antigens only reach a 70% of sensitivity. Tests based on the detection of antibodies by immunoenzymatic assays have been improved. The circumoval precipitine test has shown a high sensitivity (97%), specificity (100%), and correlation with oviposition, being considered the best confirmatory diagnostic test. Additionally to the classical immunoenzymatic assays, the development of the alkaline phosphatase immunoassay, allowed to reach a 100% specificity with an 89% sensitivity. Recently, we have developed a modified ELISA in which the soluble egg antigen is treated with sodium metaperiodate (SMP-ELISA) in order to eliminate the glycosilated epitopes responsible for the false positive reactions. The specificity and sensitivity reaches 97% and 99%, respectively. Synthetic peptides from the excretory-secretory enzymes, cathepsin B (Sm31) legumain (Sm32) and cathepsin D (Sm45), have been synthesized. The combination of two peptides derived from the Sm31 have been evaluated, reaching a sensitivity of 96% when analyzed independently and with a 100% specificity. Antibodies raised in rabbits against peptides derived from the Sm31 and Sm32 are currently evaluated in two different antigen-capture-based assays. The development of a simple, cheap and reliable test that correlates with parasite activity is a major goal.
Noya
O
O
Sección de Biohelmintiasis, Instituto de Medicina Tropical, Universidad Central de Venezuela, Caracas, Venezuela. noyaoo@yahoo.com
Alarcón de Noya
B
B
Losada
S
S
Colmenares
C
C
Guzmán
C
C
Lorenzo
M A
MA
Bermúdez
H
H
D000818:Animals; D000947:Antigens, Helminth / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005189:False Positive Reactions; D005243:Feces / Q000469:parasitology; D006801:Humans; D012550:Schistosoma mansoni / Q000276:immunology; D012552:Schistosomiasis / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D012698:Serologic Tests; D014687:Venezuela
D000947:Antigens, Helminth