Abattoir surveillance of paratuberculosis in farmed deer in New Zealand

摘要

Continuing surveillance for paratuberculosis provides crucial information for monitoring the success of a disease control programme. However, surveillance can be difficult and expensive. In this paper we describe the efficient use of abattoir surveillance for documenting the spread of paratuberculosis in farmed deer. Deer farming is a major industry in New Zealand with approximately 2 million deer raised on pasture on 5000 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 (MAP) can be very similar to those of caused by Mycobacterium bovis. Tissue samples from gut associated lymph nodes of suspect cases of bovine tuberculosis identified at slaughter have for the last 20 years been cultured for MAP as well as M. bovis. The findings from these examinations have provided an developing picture of paratuberculosis in farmed deer in New Zealand. Since the 1980s, over 1550 cases of MAP 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 the "bovine" strain of MAP was present in 94 of the 98 infected herds examined, and the "ovine" strain was present in the remainder. This highlights that both sheep and cattle are potential new sources of infection for deer.