This study describes the isolation of a Toxocara canis species-specific excretory-secretory (ES)
antigen and the development of an
enzyme-linked
immunosorbent assay (ELISA) based on this
antigen. Analysis of the ES
antigens of T. canis, Toxocara vitulorum, Ascaris lumbricoides and Necator americanus larval
antigen was performed by SDS-PAGE followed by western blotting. A 57 kDa T. canis-specific antibody fraction (TcES-57) was identified by western blotting and labelling with anti-Toxocara
antibodies (from experimental rabbits and human patients) and tracing with anti-human or anti-rabbit
peroxidase conjugate. No
protein fraction of 57 kDa was detected in ES or larval
antigens collected from T. canis, T. vitulorum, A. lumbricoides and N. americanus. Using TcES-57, a specific antiserum was produced in rabbits and a double sandwich ELISA was developed. This test was validated using known seropositive sera from
toxocariasis patients, sera from A. lumbricoides or N. americanus patients, and 50 serum samples from cats. These tests revealed that TcES-57
antigen is specific to T. canis
infection and does not cross react with sera of other related
infections. Thus, ELISA based on TcES-57
antigen was proven to be an effective tool in the diagnosis of
toxocariasis and studies on the role of T. canis in the epidemiology of human
toxocariasis.