[Increase of analytical sensitivity of FasciDIG system for the diagnosis of Fasciola hepatica].

Abstract

Introduction: fasciolosis is an endemic disease in cattle in Cuba and there is an increase in the number of reported human cases in recent years. The coproparasitological diagnosis of fasciolosis has low sensitivity and is hard-working; for that reason, it is important to use immunoenzymatic methods mainly those that can detect this parasite antigens in the feces. A system for antigen detection called FasciDIG, with a reported sensitivity of 10 ng/mL has been developed in "Pedro Kouri" Institute of Tropical Medicine.

Objective: to increase the sensitivity of FasciDIG through some modifications to this diagnostic method.

Methods: two foul dilutions (concentrations of antigen 1 000 ng/mL- 1.95ng/mL in H20 Tween-20) were evaluated in a simulated system using FasciDIG and modified FasciDIG. The FasciDiG was modified using the secondary antibody obtained from rabbit against excretory-secretory antigens of Fasciola hepatica combined with biotin and then adding commercial conjugated extravidine peroxidase. Feces were collected from the rectum of 96 animals for slaughter and were evaluated by both methods, FasciDig and modified FasciDig. Kappa index was calculated between both assays.

Results: the detection limit for the FasciDIG was 3.9 ng/mL whereas the modified FasciDIG detected up to 1.95 ng/mL. The agreement index calculated between the two tests was 0.6238 corresponding to an index of substantive or good agreement.

Conclusions: the modified method is more sensitive than FasciDIG and it can supplement the diagnosis of fasciolosis. The number of analyzed samples should be increased and the sensitivity and specificity should also be determined using the serial conic-cup sedimentation technique as the gold standard.