Prevalence of antibodies to Leptospira hardjo in bulk tank milk from unvaccinated dairy herds in the south-west region of Poland.

Bulk tank milk samples were collected from 309 randomly selected dairy cattle herds from the south-western region of Poland in 2010-2011. Samples were tested for antibodies against Leptospira hardjo using DAS-ELISA. Herd level seroprevalence of antibodies against this serovar was low (3.2%). Sample value related to positive control value (S/P ratio) results were highest in herds with 51-100 and 101-500 animals, being 4.6 and 4.1% respectively. The S/P ratio of positive samples indicated a low percentage of infected animals in positive herds.