CAE: Caprine Arthritis Encephalitis
Caprine Arthritis Encephalitis, or "CAE", is a common disease of goats. 20-50% of blood samples tested at labs are positive. This disease is caused by a retrovirus that can "hide out" in certain parts of the body, may or may not be detected by the immune system, and may or may not cause symptoms. It causes symptoms in about 15% of infected goats. The signs include mastitis (udder infection), encephalitis and neurologic symptoms, and arthritic swollen joints. Some animals die from this disease, and in others it shortens their lifespan and productivity.
The virus lives in white blood cells. White blood cells are present throughout the body in milk, blood, saliva, nasal and eye discharge, any infected areas or skin, etc. Although colostrum and milk are the main routes of transmission, goats can also be infected by reusing needles, being in close contact, shared feeders or water buckets. Sheep can be infected with the disease as well, so if you have sheep on the property, they should be tested for the sheep version of the disease, called Ovine Progressive Pneumonia ("OPP"). This has all been experimentally confirmed. So, if you find you have a positive goat, the goat must be separated from your herd to minimize the risk of the remaining members of the herd from being infected. It is MUCH easier and safer to remove any positive animals from your property altogether.
CAE is very difficult to detect through testing due to the virus being present in small amounts or not stimulating an immune response by the goat. This means that testing does not always detect positive goats. This is why, even though we keep a herd that tests negative yearly, we still practice strict CAE prevention protocols. A goat that tests negative for 4 years could test positive the 5th year and been infected the entire 5 years.
On the other hand, it seems that there are many reports of some goats testing positive who are not really positive, but the test is being set off by another, unrelated infection. This makes testing very controversial since there seems to be many "gray areas" in whether or not goats are truely positive.
There are 3 tests available to test for CAE:
1. AGID - This is the oldest test and is not as sensitive as the newer ELISA test.
2. ELISA - This is a newer test that tests for antibodies to CAE produced by the immune system of the goat. Available at many labs including Biopryn labs. Requires a serum sample (2ml of blood in a red top tube). Accuracy of these tests DOES rely on the lab processing it correctly. Trusted labs are University labs, WADDL, and Biopryn. This is the same test used for OPP in sheep.
3. PCR - This test tests for the DNA of the virus itself. Because this is a more advanced test, it is more expensive. Available at the Colorado State University Veterinary Diagnostic Lab. Requires a whole blood sample (1ml blood in a purple/lavender top tube). The virus may not always be present in a blood sample, it may be hiding out in only certain parts of the body.
It is recomended testing be done at least yearly - more often if your goats are exposed to goats from outside farms. Any new goats should be tested immediately and quarantined as far as possible from your herd for at least 1 month with no sharing of equipment.