SEROLOGICAL RESPONSE OVER TIME TO RECOMBINANT NEOSPORA-CANINUM ANTIGENS IN CATTLE AFTER A NEOSPOROSIS-INDUCED ABORTION

Recombinant Neospora caninum tachyzoite antigens were evaluated in an enzyme-linked immunosorbent assay (ELISA) for recognition by serum ant ibodies (Ab) from Neospora-infected cattle, Serum samples were obtaine d every 2 to 3 weeks for 8 to 15 months from 10 cows with histories of Neospora-associated abortion, Serum samples were also obtained from o ffspring of these animals and from a large number of cows that had abo rted a fetus, due to infection by Neospora or other organisms, at vari ous times during gestation, All 10 cows had positive ELISA Ab titers t o both recombinant N. caninum tachyzoite antigens after abortion, duri ng subsequent gestation, and after parturition. In three cows, there w as a noticeable peak in Ab titers early in gestation, Calves born to N eospora-infected cows also had positive titers of Ab to the recombinan t tachyzoite antigens, and these titers remained elevated for at least 4 months after birth, A portion of the serum immunoglobulin in calves may have been derived from colostrum of infected cows, A calf born fr om a seronegative mother had a positive ELISA titer only after being f ed colostrum from a seropositive cow, However, precolostral titers in calves horn from Neospora-infected cows were high at birth, suggesting that the parasite was transmitted to the fetus via the placenta and i nduced a humoral immune response therein, The recombinant tachyzoite a ntigens were also useful for corroborating clinical diagnoses of Neosp ora-induced abortion, A significant difference (P < 0.05) between anti -recombinant antigen Ab titers in cows that aborted due to Neospora an d those in cows that aborted from other causes was found.