A survey to estimate the herd level prevalence of paratuberculosis in the dairy herd of the United Kingdom

A study was carried out on randomly selected dairy cow herds in the UK to estimate the herd level prevalence of paratuberculosis. Dairy herds were selected at random and invited to participate in the study. A questionnaire was used to examine possible sources of bias behind participation in the study and possible associations between the presence of disease in the herd and management factors. A blood and a faeces sample were collected from all females of three years and older in the herd along with a bulk milk tank sample and a prescribed set of faecal and slurry samples from the farm unit. A commercially available enzyme-linked immunosorbant-assay (ELISA) was used to test for the presence of antibody to Mycobacterium avium subspecies paratuberculosis (Map) in the blood and bulk tank milk samples. Faecal samples were cultured for Map using a liquid based culture system and bulk milk samples were examined for the presence of Map by culture and polymerase chain reaction (PCR). A subsidiary study to determine the genetic variation of isolates of Map was carried out and blood samples were stored to form a DNA archive for possible further work. This paper gives an outline of the rationale and methodology used.