|De marez, Tine|
Submitted to: BARC Poster Day
Publication Type: Abstract only
Publication Acceptance Date: 3/14/2001
Publication Date: 4/1/2001
Citation: De Marez, T., Dubey, J.P., Gasbarre, L.C. 2001. Primary immune responses in calves orally inoculated with canine-derived neospora caninum oocysts. BARC Poster Day. Interpretive Summary:
Technical Abstract: Neospora caninum (NC) has been identified as a major cause of abortion in cattle throughout the world. Recently, dogs were shown to be able to pass oocysts when fed the parasite, and thus can serve as a definitive host for this parasite. This finding has made it possible to study both horizontal and vertical parasite transmission in cattle. The aim of this study was to odefine immune responses in calves orally inoculated with NC oocysts isolated from dog feces. Seven calves were inoculated with approximately 10 x 103 NC oocysts, 3 calves served as sham-inoculated, uninfected controls. Before inoculation, all calves were serologically negative for anti-Neospora antibodies as determined in an IFA at a 1:25 dilution of bovine sera, and none of the calves demonstrated cells reactive to Neospora antigen in an in vitro lymphocyte proliferation assay. At slaughter 76 days and 82 days post infection all infected calves showed Neospora DNA in brain and spinal cord an indicated by PCR, while the 3 sham-inoculated calves were negative. Peripheral blood lymphocytes from inoculated calves showed a response to crude NC antigen extract as early as 1 week post inoculation and antigen specific cells were demonstrated in lymphoid organs after slaughter. Within 2 weeks of inoculation Neospora-specific antibodies were detected in the serum from inoculated calves but not from the uninfected calves. Analyses of lymphoid tissues from the calves indicate minor shifts in T-cell numbers in the NC-inoculated calves. Analyses of cytokine expression in these tissues are in progress. This information should help define how to protect cattle against this parasitic infection.