A significantly lower incidence of abortion was observed
in vaccinated compared to non-vaccinated cows,16 and 26% respectively (P = 0.01),with
a vaccine efficacy of 39%.However,the number of seropositive offspring remained simi-
lar in both groups.Overall,this field trial suggests that vaccination with live N. caninum
tachyzoites should be considered as an effective measure to reduce abortions caused by
neosporosis in naturally infected cows.