Johne’s Disease

Johne’s Disease (JD) is a chronic wasting disease caused by the bacterium Mycobacterium paratuberculosis. Two strains are dominant in Australia. One is considered as sheep-associated and the other cattle-associated. However, it is now recognised that both strains can infect both species as well as goats, alpacas and deer.

There are several ways Johne’s bacteria can spread. Most commonly it is spread from infected cows to the calf through faeces, colostrum and milk. The bacteria can survive for over 12 months if the conditions are suitable, so the disease can spread through infected environments as well as between farms through movement of infected animals or vehicles, manure and water.

Clinical signs of JD include progressive weight loss, emaciation in older animals despite having a good appetite, and in some cases, animals may develop diarrhoea and bottle jaw. Diagnosis of JD requires assistance and testing from a veterinarian.

Dairy cattle 

In South Australia, PIRSA along with local veterinarians and farm managers look after the Dairy ManaJD program where producers have a certificate which describes their Dairy Assurance Score (DAS).

Over 70% of the SA dairy herds are tested and maintain negative herds with a DAS of 7 or above. The DAS is based on:

• Number of known infections
• Number of negative tests on the herd, and
• Other management factors.

Each herd gets a DAS based on full herd individual blood test results. It is compulsory to declare the DAS of dairy cattle offered for sale in South Australia.

For further information about Johne’s Disease and the DAS, visit the PIRSA website.

Beef cattle 

The Johne’s Beef Assurance Score (J-BAS) is a tool available to cattle producers to minimise the risk of Johne’s Disease. J-BAS is a guide and producers should always ask further questions about JD in the herd or property of interest, rather than relying on the score alone.

South Australian beef herds have traditionally had low incidence of Johne’s Disease. However, there is a high risk of introducing JD to South Australia through purchase of cattle from areas with higher incidence.

Producers should consider the following when purchasing cattle:

• Determine the level of risk of introducing JD to your herd that you are willing to accept
  • The lowest risk cattle come from herds which have the highest assurance and have been veterinarian approved
  • The highest risk cattle are from herds with poor biosecurity practices, significant history of trading cattle in areas with higher JD prevalence and no herd testing.
• Develop a biosecurity plan and ensure the animals you purchase are in line with your desired biosecurity practices
• Is it important to you to have a tested negative status (JBAS score 7 or 8) for your herd?
  • Discuss your options with your vet or PIRSA animal health officer
  • Consider testing any cattle introduced to your herd – this will require repeated annual testing for at least seven years to gain confidence that the cattle are not infected

For further information about Johne’s Disease, particularly for JBAS certification, visit the PIRSA website.

 

Pestivirus

Pestivirus, also known as bovine viral diarrhoea virus (BVDV), causes abortion, ill thrift in young animals, diarrhoea and increases susceptibility to respiratory disease. Cattle infected by Pestivirus can develop ulcerations on their lips and noses which can strongly resemble Foot-and-Mouth Disease (FMD).

The virus is spread by direct contact from transiently infected or persistently infected (PI) carrier animals to their herd mates. Transmission is by direct contact with an infected animal or its secretions.

For more information about Pestivirus, visit the PIRSA website.

 

Theileria

Theileria are protozoan parasites carried by ticks. When ticks feed on cattle, the parasite enters the blood stream and infects the red and white blood cells of cattle. This disease reduces the ability of the blood to carry oxygen, causing anaemia and weakness and may lead to the collapse of the animal. Theileria is found primarily in high rainfall areas of South Australia.

For more information about Theileria, visit the PIRSA website.