Caprine Arthritis Encephalitis (CAE), also known as Caprine retrovirus (CRV), or “big knee”, is a serious disease of goats worldwide.
Goats can be infected by CAE at any age and will remain infected for life. Symptoms may not become apparent for months to years after infection.
Clinical Signs
CAE can cause a wide range of symptoms which vary depending on the age of the goat. Mature goats will develop arthritis and bursitis in multiple joints causing them to become enlarged and painful (hence the name "Big Knee"). The condition is chronic and steadily gets worse. Affected goats develop lameness, a rough coat, and gradually lose weight. Pneumonia is also seen in some infected goats (mainly adults), resulting in progressive weight loss and respiratory distress. Other signs can include mastitis, paresis, or paralysis.
Encephalitis affects young kids two weeks to five months old. Animals with encephalitis will show signs of lameness, incoordination, progressive paralysis and finally death. Although, this form of CAE is uncommon in Tasmania.
Antibiotics are ineffective against all forms of CAE and there are no other treatments other than palliative care. Management practices that minimise transmission are extremely important in areas where there is increased risk.
Transmission of Infection
The virus is shed in all bodily secretions and blood. The main method of spread is from doe to kid via the milk or colostrum, so that kids are infected soon after birth.
Spread of infection can also occur via close contact between adults, especially in intensively managed herds such as dairy herds. Adults can be exposed through:
The disease is less common under extensive grazing conditions used for meat and fibre production, and feral goat populations.
While CAE is considered a disease of goats, certain sheep breeds have been infected by the virus, and as such, sheep could potentially be at risk of infection.
Veterinarians can diagnose CAE through blood or milk testing and can advise on management strategies and programs to limit the spread of CAE.
Market Impacts
CAE infection results in welfare issues, production losses and can limit export opportunities. Understandably, many buyers require evidence of freedom from CAE.
Goat producers interested in CAE control are encouraged to access the National Kid Rearing Plan on the Farm Biosecurity - Goats web site, and consult with their local private veterinarian.
Goat MAP, the Australian Market Assurance Program for Goats, managed by Animal Health Australia (AHA), helps producers identify and promote their low risk of CAE and Johne’s disease. As a part of Goat MAP, CAEMAP helps to organise industry’s approach to control CAE in Australia. More information on the program can be found on the Animal Health Australia website.