Ongoing data on herd prevalence of paratuberculosis is crucial information for monitoring the success of a disease control programme. The provision of reliable figures on the prevalence of paratuberculosis is both difficult and expensive. In this presentation we demonstrate the use of abattoir surveillance combined with laboratory investigation for documenting the spread of paratuberculosis in farmed deer. Deer farming is a major industry in New Zealand with approximately 1.7 million deer being raised on pasture on 4200 farms. Bovine tuberculosis has been a major concern for the deer industry and a series of measures, including abattoir surveillance, are being used to successfully control this disease. However, abattoir surveillance revealed that the macroscopic and microscopic features of infections with Mycobacterium avium subsp. avium and M. avium subsp. paratuberculosis can be very similar to those caused by Mycobacterium bovis. Tissue samples from gut associated lymph nodes of suspect cases of bovine tuberculosis identified at slaughter have for the last 15 years been cultured for M. paratuberculosis as well as M. bovis. The findings from these examinations have provided an ongoing picture of paratuberculosis in farmed deer in New Zealand. Since the 1980s, over 1400 cases of M. paratuberculosis have been identified from samples collected from abattoirs as part of the bovine tuberculosis control programme. The large increase in the number of cases and infected herds over the last five years documents the spread and worsening problem of paratuberculosis in deer. Repeat isolations from herds indicate that some herds have been persistently infected for many years. A recently developed PCR test revealed that while the "bovine" strain of M. paratuberculosis was present in over 90% of the infected herds examined, the "ovine" strain was present in some herds. This highlights that both sheep and cattle are potential new sources of infection for deer.