Bovine Johnes Disease

Disease Description - Johne’s Disease in Cattle Herds

Johne’s disease is caused by the bacterium Mycobacterium paratuberculosis. In Australia, there are two strains, one infecting sheep and the other infecting cattle. To date there appears to have been no significant spread between sheep and cattle and the diseases are considered separately for each species.

The Johne’s disease bacterium is very persistent, being able to survive for up to 12 months in the environment. Contamination of the environment must therefore be considered in any control program. In cattle, calves up to 30 days are very susceptible and readily infected if exposed to the Johne’s bacterium. They are still susceptible up to 12 months although they rarely become infected after the first year. In most cases, cattle are infected on their property of birth.

The most common method of spread is to the calf from its dam via bacteria on the udder. Calves can also be infected by cross suckling. Animals up to 12 months of age may pick up infection from contaminated pasture. Some calves may also be born infected. Because of the risk of infection, before as well as after birth, the progeny of infected cows are quite likely to be infected. Milk from infected cows is also considered a risk. Artificial insemination and embryo transfer is considered to be low-risk sources of contamination.

The most common form of spread from farm-to-farm is via an infected animal (one generally showing no clinical signs). Environmental spread has to be considered but is less common.

Features of the Disease

  • Long incubation before signs develop - from 12 months to 15 years (in most cases, 3–5 years). It also takes a long time for an animal infected as a calf to show up using the current tests.
  • Fall in milk yield.
  • Diarrhoea which can be acute, chronic or intermittent.
  • Loss of weight.
  • Emaciation.
  • Eventual death.
  • There may be several cases per year - up to 4% in very heavily infected herds. Production loss may be occurring in up to 5-10% of animals.

PIRSA Animal Health's Program

  • To implement control programs in infected, restricted and suspect status herds, that comply with the National Standard Definitions & Rules for Bovine Johne's Disease (BJD) control
  • To manage and promote the BJD Market Assurance Program (BJDMAP)
  • To prevent the introduction of BJD infected animals into South Australia
  • To extend the BJD Protected zone for the pastoral areas of South Australia
  • To promote industry involvement in policy and funding for BJD control
  • To provide program management.

Bovine Johne's Disease Market Assurance Program (BJDMAP)

This program is for cattle owners who wish to identify, protect and promote their herds as being of low risk of being infected with Johne's Disease. It is based on a testing regime and on the adoption of property and management factors that minimise the risk of the introduction of Johne's Disease into the herd. The assessment of these factors and the testing of stock are the responsibility of accredited veterinarians who are trained for the program and approved by the Chief Veterinary Officer in each state.

For information about the Australian program go to:
Johne's Disease Information Centre

For a list of herds and flock owners in Australia go to:
Guide to Assessed Herds and Flocks in Australia


Herd Status Description

All herds are assigned a status with regards to Bovine Johne’s Disease.

Non-Assessed Herd. A herd that is not known to be infected but in which there has not been enough testing to be confident that it is probably clean. This includes herds in the Market Assurance Program (MAP), which have not yet tested sufficient animals.

Monitored Negative Herd. This is a herd that has had one or more negative tests of an adequate sample of the herd and has implemented all of the other requirements of the Cattle Market Assurance Program.

Tested Negative Herd. This is a herd that has had one or more negative tests of all animals more than two years of age and which has implemented all of the other requirements of the Cattle Market Assurance Program.

Suspect Herd. This is a herd where information has been received that indicates that the herd might be infected and may therefore be a risk to other herds. It is in everyone’s interest that this suspicion be resolved as quickly as possible.

Contacts

Most rural veterinary practices have an accredited person who will be able to provide information or call Jeremy Rogers, Flaxley Research Centre, Ph (08) 8391 7138 or E mail: rogers.jeremy@saugov.sa.gov.au

A list of owners and cattle breeds currently in the Bovine Johne's Disease Market Assurance Program (BJDMAP) is kept by the Bureau of Resource Sciences, Canberra and is available at http://www.brs.gov.au/aphb/aha/jdmap/