Abstract
Diagnosis of Echinocuccus multilocularis infection in definitive host by detection of coproantigens was performed in experimentally infected dogs. A sandwich enzyme-linked immunosorbent assay (ELISA) using rabbit polyclonal antibodies against excretory/secretory (ES) antigens of E. multilocularis adult worms and murine monoclonal antibody, designated EmA9, against somatic antigens of the adult worms was used for the detection of coproantigens. The specificity of the test was evaluated using feces of animals infected with Taenia taeniaeformis, T. crassiceps, Trichuris vulpis and Toxocara canis. No cross-reaction was observed. Sensitivity was evaluated from results of a serial twofold dilution of E. multilocularis antigen. The low limit of detection was 4 ng E. multilocularis antigen g-1 of feces. Detection of coproantigens using EmA9 in feces of three dogs experimentally infected with E. multilocularis was carried out almost daily until autopsy. Coproantigens were detected as early as 3-5 days postinfection (PI) and increased steadily until autopsy on day 21 PI. Anthelmintic treatment of one dog on day 17 PI by praziquantel resulted in the disappearance of the antigens from feces. Thus, an accurate diagnosis could be made using this method. Detection of circulating antibodies was performed in parallel with the coproantigen test. Antibody levels of two dogs increased steadily from day 8 PI until 21 PI, but antibody levels of one dog which was teased with praziquantel were apparently high throughout the experimental infection. From these results, detection of coproantigens using EmA9 is a more effective diagnostic method than detection of circulating antibodies because of the capability of the actual status of infection in the host. In addition, freezing and subsequent heating of the feces did not influence the sensitivity of coproantigen detection by ELISA, which prevent accidental infection, by which fecal samples before the test is performed.
Key words: Echinocuccus multilocularis; coproantigen; monoclonal antibody; immunodiagnosis; dog; ELISA.