The aim was to detect correlations of IgG antibodies against N. caninum in serum and colostrum samples from ewes, through the IFAT, and to evaluate the presence of this immunoglobulin in the serum of newborn lambs after colostrum ingestion. Blood samples from 162 ewes that did not show any disease in the general physical examination and from their newborn lambs, not more than five days postpartum, along with 162 colostrum samples and 182 blood samples from the neonates, were analyzed. In total, 27.8% (45/162) of the mothers were positive for anti-N. caninum IgG, among which antibodies were detected in the colostrum in 46.7% (21/45). All the ewes with positive colostrum had reactive offspring. The kappa agreement for the correlation between the serological tests on the ewes and the colostrum results was 0.558. This correlation increased as the antibody titers of the mothers increased, and reached 1.000 from the titer of 1:400 from the mothers. Comparison of the antibody detection results between the offspring's serum and colostrum showed a kappa agreement of 1.000. In conclusion, there was a good agreement regarding the detection of anti-N. caninum IgG between the colostrum samples and the lambs' serum; the use of colostrum forms a noninvasive alternative for diagnosing N. caninum in sheep herds.
Keywords: neosporosis; offspring; ovine; serology.