Anti-Neospora caninum antibodies in milk in relation to production losses in dairy cattle.

A comprehensive field study was carried out with the following objectives: (a) to assess the usefulness of individual and bulk tank milk analysis for determining Neospora caninum serostatus in individual cows and herds, and (b) to study the associations between N. caninum infection status (based on milk testing), and several productive and reproductive parameters in the animals. Antibodies were detected with a commercially available ELISA test (Bio K 192/5). Analysis of paired serum and milk samples from 1134 lactating cows on 38 farms revealed that 97.6% of the ELISA results were coincident, irrespective of whether serum or milk samples were used. Moreover, multiple linear regression analysis revealed that 86.0% of the variations in ELISA values in milk were due to variations in the serum. The measurement of antibodies in bulk tank milk was a good estimator of the herd level status of N. caninum infection, and enabled detection of infection in 94.7% herds with ≥10.0% seropositive cows and/or in all herds with >4% highly seropositive cows. The odds ratio for abortion in seropositive animals was 9.1 times higher than in seronegative animals. The infection serostatus was also a significant risk factor, as the odds ratio for abortion was even higher (12.0 times) in cows categorized as highly seropositive. ELISA values for the bulk milk from 387 randomly selected herds were negatively associated with average milk production. Moreover, milk production losses mainly occurred on farms categorized as highly positive (i.e. herds with ≥20.0% seropositive cows).

Epidemiology of neosporosis in dairy cattle in Galicia (NW Spain).

This comprehensive study of neosporosis in dairy cattle in Galicia (NW Spain) included: (1) a comparative study of three serological techniques for detection of Neospora caninum antibodies (direct agglutination, enzyme-linked immunosorbent assay and indirect immunofluorescence); (2) a cross-sectional serological survey in which 276 herds and 5,196 animals were tested; (3) a study of N. caninum antibody dynamics; (4) the isolation of viable tachyzoites of N. caninum. Data were analysed to determine the risk factors associated with the infection. A total of 219 herds (79.3%) and 816 heads of cattle (15.7%) were found to be seropositive. Seropositivity was higher on farms with dogs than on farms without dogs, and there was a negative correlation between the size of the herds and seroprevalence. Co-infection with Toxoplasma gondii increased the risk of seropositivity. Cows infected with N. caninum were 5.3 times more likely to abort than non-infected cows. The dynamics study showed an increase in anti-N. caninum antibody titres during the third trimester of pregnancy. Viable tachyzoites were isolated from brain samples. These results indicate that the economic impact of N. caninum is high in Galicia, and therefore, the inclusion of control measures for neosporosis in the official control health programmes is strongly recommended.