A case-control study of Nocardia mastitis in Ontario dairy herds.

A case-control study was conducted to identify milking hygiene and udder therapy factors associated with a diagnosis of Nocardia mastitis in dairy herds from which milk samples are submitted to the Ontario Ministry of Agriculture and Food, Veterinary Laboratory Services, Guelph laboratory. The data were collected by telephone interview from 31 case and 31 control herds.After analytical control for confounders, blanket dry cow therapy and a dry cow antibiotic product were associated with a diagnosis of Nocardia mastitis in a herd, whereas another dry cow antibiotic product had a sparing effect.In comparison to mastitis pathogens susceptible to dry cow antibiotic therapy, Nocardia species were isolated infrequently from milk specimens submitted to the Guelph mastitis laboratory.