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Serologic responses of cattle and other animals infected with Neospora caninum
J P Dubey1, D S Lindsay, D S Adams
1USDA, Livestock and Poultry Sciences Institute, Parasite Biology and Epidemiology Laboratory, Beltsville, MD 20705, USA.
Objective:
To examine cross-reactivity among Neospora caninum and closely-related apicomplexans.
Design:
Sera from animals were examined for antibody production to N caninum and cross-reactivity to Toxoplasma gondii.
Animals:
Cattle were experimentally infected with 3 tissue cyst-forming protozoan parasites N caninum, T gondii, and Sarcocystis sp, and calves were monospecifically inoculated with the intestinal coccidia, Eimeria bovis and Cryptosporidium parvum. Similar studies were done in laboratory rabbits inoculated with N caninum, T gondii, Hammondia hammondi, and Sarcocystis sp. Additionally, sera were obtained from ewes, lambs, goats, sows, cats, rats, and mice inoculated with N caninum tachyzoites.
Procedure:
The indirect fluorescent antibody (IFA) and ELISA antibody tests (cattle only) were used to examine reactivity to N caninum; the modified direct agglutination, Sabin-Feldman dye, and IFA tests were used to evaluate reactivity to T gondii.
Results:
Serologic cross-reactivity among N caninum, T gondii, and Sarcocystis sp was none or minimal by the IFA test. There was some reactivity to N caninum by the use of ELISA in cattle inoculated with Sarcocystis sp.
Conclusions:
The IFA test for N caninum was specific for the diagnosis of neosporosis in animals.