Johne's Disease Article | Read Now

Johne’s Disease (JD) affects sheep, cattle and goats.

It is caused by different strains of the same bacterium called Mycobacterium avium paratuberculosis.

Infection significantly reduces animal productivity and always results in death.

It is spread through the environment and infected material.

Infected animals will not be identifiable for years.

The best form of protection for sheep is a one-off vaccination within 4 to 16 weeks of age.

What is Johne’s disease?

Johne’s Disease (JD) or ‘Paratuberculosis’ is a significant disease of concern in Australia that has devastating effects for infected sheep and cattle. Ovine Johne’s Disease (OJD) mainly affects sheep and goats, and Bovine Johne’s Disease (BJD) predominantly affects cattle but has been found to affect goats, deer and camelids. BJD and OJD are both caused by different strains of the same bacterium known as Mycobacterium avium paratuberculosis.

JD is a starving and wasting disease that results in death. Sub-clinical disease can prevent livestock from reaching their full potential for growth and milk production. This chronic and contagious disease is of significant concern to Australian producers due to its ability to remain latent for several years before expression, after which the damage has already been done.

Whilst BJD is more prevalent in dairy herds than in beef herds, producers should take proactive biosecurity measures to prevent infection. OJD is endemic in the Australian sheep flock and is more common in certain regions.

How is it spread?

The mycobacterium is spread to animals through infected materials or environments. It is hardy and can survive outside of an animal for 12 months or longer in ideal conditions (boggy, wet areas).

Animals can be infected at any age, however due to their feeding habits, young stock are more likely to become infected. Lambs and calves become infected whilst drinking from contaminated udders, or from contaminated feed or water. They can also become infected in utero, especially when the dam is showing signs of JD during pregnancy. Colostrum and milk from these dams may also pass on the bacteria.

Once an animal has become infected, the bacteria live and multiply in the intestinal walls. Infected animals excrete more bacteria in their manure, which continues to contaminate the environment.

Signs & Symptoms

Animals are mostly infected within 12 months of age and often do not show signs of clinical disease until they reach 4-5 years of age.

The mycobacterium that causes Johne’s Disease lives in the intestinal walls of livestock. While the bacterium is ‘growing’, it is present without being detected or causing production losses – these are called ‘carrier’ animals. Depending on bacterial activity, carrier animals will shed the bacteria, leading to contamination of the environment.

After 2-4 years, the animals’ inflammatory response to the Johne’s bacteria will have caused a significant and irreversible thickening of the intestinal wall, which interrupts normal absorption of food and water. The affected animal will be hungry and keep their appetite, but cannot physically absorb any nutrients. This results in sustained weight loss, until finally the animal enters the final stages of starvation and dies.

Clinical Signs – Cattle

Gradual weight loss even when appetite is standard or increased (wasting)
Chronic diarrhoea or scouring
Bottle jaw (fluid build-up leaving a soft swelling under the lower jaw)
Reduced milk production (dairy cattle)
Death

Clinical Signs – Sheep

Gradual weight loss even when appetite is standard or increased (wasting)
Chronic diarrhoea or scouring, but not routinely
Failed body condition recovery after weaning, followed by wasting
Body condition decline is severe (wethers)
Death

Disease progression and severity can be promoted by stress, particularly nutritional stress during lactation in females.

If the animal is ‘shedding’ bacteria, the disease can be diagnosed by blood tests. If they aren’t shedding any bacteria, the disease cannot be diagnosed definitively. Animals that are infected may not be shedding bacteria and could pass a blood test, so negative test results do not confirm absence of infection.

Disease progression and severity can be promoted by stress, particularly nutritional stress during lactation in females. Observable signs of infection tend to appear following a period of stress, whether that be calving, inadequate nutrition, or heavy milk production.

Preventing Johne’s Disease

There are several ways to reduce JD from infecting your animals, this differs between beef and dairy herds as well as flocks of sheep.

Sheep Producers

Vaccination: The most effective form of protection against OJD is to vaccinate your sheep. All lambs must be vaccinated with Gudair within 4 to 16 weeks of birth, and this 1mL injection will protect them from OJD for their entire life. There is no other vaccine that will protect sheep from OJD, it is highly protective and is proven to reduce mortalities in infected flocks by more than 90%.
Buy protected stock: Sheep health declarations are an excellent way of ensuring any sheep you buy are protected against OJD. Ensure that all sheep you are purchasing have been treated with JD approved vaccines, have tested negative for JD or have consistent JD management practices on the property. Only purchase animals from properties of high levels of assurance of not coming from an OJD affected property.
Grazing management: Do not graze any weaned lambs on paddocks that have been grazed by older classes of sheep within the last 3 months. Fence off low areas where contaminated water may be. Once vaccinated, these areas can be grazed by young animals.
Culling: any sheep suspected of infection and any lambs born from ewes suspected of being infected must be culled.

Beef Producers

Biosecurity plan: Develop a biosecurity plan for your farm that identifies disease risk practices and sources (e.g. prescence or introduction of dairy cattle) and introduce strategies to mitigate the likelihood of the disease entering your system.
Avoid dairy cattle: Dairy cattle are far more likely to be infected with BJD than beef cattle, avoid the introduction (including agistment) or dairy-cross or dairy cattle unless they are guaranteed to be free of infection or Check Tested with assurance scores of 7 and above.
Buy healthy/clean animals: The most likely source of BJD infection for beef herds are infected cattle brought onto properties. Cattle health declarations are an excellent way of ensuring any cattle you buy are protected against BJD. Ensure that all animals you are purchasing are from properties with BJD prevention measures.
Culling: Any cattle suspected of infection and any calves born from cows suspected of being infected must be culled.
Vaccination: Note: this product has restricted use in Australia and is primarily targeted at controlling disease in known infected herds. Providing a lifetime of protection, you can vaccinate calves 3 weeks and older with 1ml of “Silirium” to protect them against BJD disease.

Dairy Producers

Clean calving areas: Reduce faecal contamination by strip grazing or fencing off grazed areas for calving animals. If calving indoors, ensure bedding is kept dry and clean to prevent calves from being infected by BJD.
Separate cows & calves: The longer a calf is left with its mother, the greater the likelihood of ingesting faeces and BJD infection. Remove calves from mothers and keep other JD carrier animals away from calves, including goats, sheep, deer and alpacas.
Keep environments clean: Young animals are most susceptible to the disease. It is essential to prevent the contamination of calf milk and the environment. This includes ensuring all people, vehicles and equipment are clean.
Regular testing & culling: Test for the presence of BJD every 1-2 years (or more often), any cattle suspected of infection and any calves born from cows suspected of being infected must be culled.
Vaccination: Providing a lifetime of protection, you can vaccinate calves 3 weeks and older with 1ml of “Silirium” to protect them against BJD disease. Note that this product has restricted use in Australia and is primarily targerted at controlling disease in known infected herds.

What if I suspect my animals have Johne’s Disease?

JD is a notifiable disease in Australia, meaning you must alert your state/territory department of primary industries and follow their immediate and structured action. A local veterinarian will need to be alerted to conduct a confirmed diagnosis.

Victoria: You must notify Agriculture Victoria within 7 days of identification and call the Emergency Animal Disease Hotline on 1800 675 888.

New South Wales: You must notify Local Land Services on 1300 795 299 or the Department of Primary Industries within 1 working day.

Tasmania: Call the Emergency Animal Disease Hotline on 1800 675 888.

South Australia: Call the Emergency Animal Disease Hotline on 1800 675 888.

Queensland: Biosecurity Queensland on 13 25 23.

Western Australia: Pest and Disease Information Service on 9368 3080.

References

Johne’s Disease | Meat & Livestock Australia

Johne’s Disease | Biosecurity Queensland

Johne’s Disease | Animal Health Australia

Johne’s Disease | NSW DPI

Bovine Johne’s Disease | Agriculture Victoria