A subset of 57 liquid milk production holdings representing 3800 cows (9700 total cattle) were surveyed as part of an emerging pathogen prevalence study based on milk filter residue (MFR) analysis. 10% of MFR samples from clinically normal herds demonstrated Map DNA positive signals on IMS-PCR analysis. Epidemiological factors relevant to the development of a Map control programme were assessed. 49% of farmers clipped and cleaned cows' udders pre-calving. 61% of calvings were supervised. Post calving, 14% removed calves immediately, 16% allowed suckling >24 hours and 9% allowed communal suckling. 81% of farms fed an average of 4.6L of dam's colostrum in the first 24 hrs, and 88% fed 8.3L between 24 and 72 hrs. 25% of farms (14/57) used pooled colostrum in the first 24 hours and 88% fed pooled milk, while 51% of farms feed pooled milk mixed with colostrum. 25% of farms used milk replacer. 35% wash udders pre-milking all year, 35% pre-milking wash only during winter. 84% clip cows udders routinely.57% spread slurry on calf pasture, and 53% allow calves graze adult grazed pasture.9% of farmers purchase cattle from multiple farms, 14% use agents or marts and 8% had purchased imported animals. In 2003, 19% of farms had progeny of imported animals on their farm, and 28% had boundary contact with neighbouring cattle.32% of farms had common water sources. Rabbit faeces and water gave PCR positive Map signals on 41% and 33% of farms respectively. These findings disclose a serious challenge in terms of controlling the threat posed by Map imported into Irish dairy farms since 1994.