Demographics of cattle positive for Mycobacterium avium subspecies paratuberculosis by faecal culture, from submissions to the Cork Regional Veterinary Laboratory

Abstract

The demography of bovine infections caused by Mycobacterium avium subspecies paratuberculosis (MAP) in Ireland is poorly defined. The objective of this study was to describe the demographics of cattle positive to MAP on faecal culture, based on submissions to the Cork Regional Veterinary Laboratory (Cork RVL) from 1994 to 2006. The study focused on all available faecal samples from adult cattle with non-responsive chronic diarrhoea that were submitted by private veterinary practitioners to Cork RVL for MAP culture. For each MAP-positive by faecal culture animal, data were collated from Cork RVL and Cattle Movement Monitoring Scheme (CMMS) records. Johne's disease (JD) was confirmed in 110 animals from 86 herds by the Cork RVL between 1994 and 2006, with a rate of positive cases between 15% and 18% over last four years of the study. Two breeds (Holstein/Friesian or Limousin) made up 78% of submissions. Movements were assessed for the 57 study animals with available movement information, 90% died within one year of the test and 26% tested positive in the herd they were born into. The study provides preliminary information about movement trends and demographics of animals with MAP positive submissions. Although the study area is restricted, it includes the most intensive (and economically-important) dairy region in Ireland. The demographics of JD infection from the study area are in agreement with international reports. Further work is required to determine demographic trends, incidence and prevalence of JD throughout Ireland. It is hoped this work may contribute to the development of a surveillance strategy for MAP by regional veterinary laboratories.

Figure 1

Number of submissions (Part A), animals (Parts B and C), and numbers of submissions/animals available within each part of analyses.

Figure 2

The total number of submissions to the Cork RVL for MAP faecal culture, and the number and percentage of submissions that were MAP-positive, by year between 1994 to 2006. Percentage positive from total are given from 1997 to 2006.

Figure 3

The location of the Cork Regional Veterinary Laboratory and of the 109 animals that were positive to MAP on faecal culture during 1994 to 2006. To ensure farm anonymity, the location of each study animal was represented at the centroid of the relevant district electoral division. The size of the circle reflects the number of study animals in each district electoral division.

Figure 4

The number of Holstein/Friesian and Limousin animals that were confirmed MAP-positive on faecal culture at Cork Regional Veterinary Laboratory, by year.

Figure 5

Network diagram of the relationships between MAP-culture positive animals (study animals) and test locations. The number beside each study animal (red dot) indicates the year of birth. The number beside each farm (blue dot) refers to the number of animals on that farm that tested positive. Arrows indicate the direction of movement of study animals. Three reference groups (A, B, C) highlight movement trends in the network, including the movement of multiple positive animals from a single infected herd (A), a study (positive) animal moving through farms before testing positive and moving to a factory or knackery (B; grey and black dots, respectively), and imported animals testing positive in Irish herds(C).