Neospora caninum infection is one of the significant cause of losses in the cattle reproduction (abortion, resorption and repeat breeding, born congenitally infected calves with clinical symptoms of neosporosis or clinically normal but persistently infected calves). Even one animal, who is a source and reservuar of protozoon (single reactor) determined the stability of infection within the herd. In 2007 forty seven cattle herds were examined in the screening study to bovine neosporosis. Sera were obtained from 25 small herds (“M”, n> 20≤ 50), 11 medium (“Ś”, n>50<150) and large herds (“D”, n≥ 150) respectively. Four hundred and seventy six serum samples were examined for the presence of N. caninum antibodies by an ELISA (Idexx, Cherd Check, USA). Results were considered positive at a cut-off level of s/p ≥ 0,5. The antibody concentration was established for each of examined herds as a mean value of individual results. Of the 476 serum samples investigated, 27,73% (132/476) were confirmed to be positive. However et least one seropositive animal was identified in approximately 80% of all herds, for the herd-level. The number of seropositive reagents respectively to all examined animals was 45/241 within D, 41/110 within Ś and 46/125 within M herds. The minimum recorded number of positive results obtained in the single herd was 0 and the maximum was 10.

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