Biosecurity
Livestock Diseases

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, 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 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.

Johne’s disease in sheep (also referred to as Ovine Johne’s Disease or OJD) is an infectious, incurable wasting disease caused by the bacteria Mycobacterium paratuberculosis.

OJD usually enters a flock through new infected sheep which are introduced (including strays), the consumption of pasture or drink water contaminated by faeces from infected sheep/other susceptible species, or co-grazing with infected cattle or other species infected with Johne’s disease such as goats and alpacas.

Clinical signs of OJD are not easily detectable as they are insidious and progressive. Infected sheep progressively lose weight and are malnourished which usually leads to death or euthanasia up to eight months after clinical signs are first observed. The most common sign of OJD is a distinct ‘poor’ tail end of the mob.

Due to long incubation periods, healthy looking animals can spread the disease bacteria before being clinically affected. The level of disease is influenced by management practices, environment, rainfall and stocking rates. This disease is more common in high rainfall, high stocking environments.

The SA Sheep Industry Fund support the South Australian OJD Management Program. This program is managed by PIRSA and aims to reduce the economic impact of OJD by:

• Encouraging producers to voluntarily investigate and manage Johne’s disease in their flocks
• Encouraging the declaration of OJD risk for all sheep sold or entering SA by using the National Sheep Health Declaration
• Improving industry awareness of OJD risks and its management through education
• Promoting low-risk trading and management practice

Producers can investigate and monitor OJD in their flock by requesting an inspection when consigning sheep to Thomas Foods International (TFI) abattoirs, or through on-farm testing by a private veterinarian or PIRSA staff.

For more information about OJD, visit the PIRSA website

For more on the OJD management program, visit the PIRSA website

Lice in sheep causes major economic loss to the industry by reducing the quality and quantity of wool and increasing the cost of labour and chemical treatments.

Most new lice infestations start from contact with other lousy sheep, which may be purchased (including rams), stray sheep from other mobs or properties.

C auses of continuing infestations include split shearings and treating ewes with lambs at foot or pregnant ewes due to lamb within 6 weeks of treatment, and failure to eradicate lice on a previous treatment.

In the early stages of an infestation louse numbers increase very slowly and it may take many months for the infestation to become obvious. When introducing purchased or returning strays to a mob, careful inspection and regular monitoring will prevent new infestations, save production loss, reduce residues and save costs.

For more information including management options, visit the PIRSA website or LiceBoss.

Footrot is a contagious bacterial disease in sheep caused by the bacterium Dichelobacter nodosus (D. nodosus). Footrot causes inflammation of the interdigital skin and potential underrunning of the hoof.

In South Australia, footrot is a notifiable disease.

Any suspicion of infection must be reported immediately.

Footrot can cause significant economic loss to producers by reducing fertility, wool growth, growth rates and limiting market opportunities through sheep sales.

Controlling and eradicating footrot can be costly and time consuming however the long-term benefit of eradication far outweighs the cost.

For more information, visit the PIRSA website.

Ovine Brucellosis (OB) is a venereal disease in sheep which can lead to infertility, increased lambing periods, abortions and weak lambs.

Transmission occurs during mating and ultimately affects the reproductive organs, particularly in rams. Producers should be aware of the OB status of any rams they are purchasing as the disease is incurable and will result in the animals being culled.

For more information, visit the PIRSA website