PROGRESS TOWARD THE DEVELOPMENT OF SEROLOGICAL TESTS FOR DIAGNOSIS OF COCCIDIOSIS IN CHICKENS

 

J.B.Molloy1, C. Constantinoiu2, G. Richards3,
J-M.L. Hewitson1, A.G. Bruyeres1, G. Coleman2 and W.K. Jorgensen1

1Emerging Technologies, Department of Primary Industries and Fisheries.
Yeerongpilly, Qld. 2School of Veterinary Science, University
of Queensland, St. Lucia, Qld.
3Eimeria Pty Ltd, Melbourne, Australia
(medichick@ava.com.au)

Vaccines comprising attenuated strains of each of the seven species of Eimeria that cause coccidiosis in Australian chickens have been shown to be effective in preventing acute disease. Improved diagnostic tests are now required for monitoring vaccine efficacy, epidemiological studies and for the implementation of effective control strategies. As a first step toward developing species-specific serological tests we have investigated the chicken antibody response to infection. Birds infected with the E. tenella vaccine strain produced parasite-specific antibodies between 16 and 30 days post-infection. Experiments with parasite antigens prepared from heavily parasitized gut linings harvested from birds sacrificed at varying times post-infection suggested that the antibodies were directed exclusively against gametocyte antigens. Immunostaining infected gut sections confirmed this observation. Merozoites, gametocytes and oocysts were all present in the sections but antibodies bound only to gametocytes. Monoclonal antibodies that recognize E. tenella gametocytes epitopes have been developed and characterized by immunofluorescent and immunoperoxidase staining of parasitized tissue and purified gametocytes and in Western blots. Implications for the development and application of species-specific serological tests for coccidiosis are discussed.