A healthy goat before CAE...
Same goat, 12 months after previous picture.
CAPRINE ARTHRITIC ENCEPHALITIS - THE SILENT KILLERCaprine Arthritic Encephalitis (CAE), discovered by researchers at Washington State University over 20 years ago, is a viral infection in goats which can cause encephalitis in kids and chronic joint disease in adults.
The elusive nature of CAE complicates the goat raiser's ability to control the disease. Goats can be infected with CAE their entire lives and never display visible symptoms. The disease is more often seen in adult goats. Encephalitic seizures usually kill infected kids quickly.
Adults with visible signs of CAE often have over-sized knobby knees that are swollen in appearance. Sitting down is painful, so they don't wear the hair off their knees. Smooth knee pads can be an indication of CAE infection. Hard udders, sometimes without any milk at all, and fatal pneumonia are symptomatic of CAE. Progressive crippling arthritis is displayed in older adults. Caprine Arthritic Encephalitis is a retro-virus; in other words, antibodies created by the CAE-positive goat are not effective in attacking the virus. The presence of antibodies indicates infection but not immunity to the disease. AIDS in humans is also a retro-virus. While CAE is restricted to goats (caprines), other ruminants have their own species' versions of retro-viruses. Unlike Caseous Lymphadinitis (CL), another infectious disease found in some goats, CAE is not contagious to human beings.
Researchers at Washington State University found that 80% of the dairy goats which they tested carried the virus, while a smaller percentage displayed clinical (visible) symptoms of the disease. However, CAE is not unique to dairy goats, although it has been most commonly associated with dairy breeds in the past. With the appearance of the Boer goat into the United States and the cross-breeding frenzy which has occurred as breeders try to create an improved slaughter animal, CAE is showing up in many breeds in which it had not previously been found to exist.
The most direct infection route is from mother to kid through infected colostrum, body fluids, and milk. In order to maintain CAE-free herds, dairy-goat breeders often take kids from the dam at the moment of birth . . . never allowing her to touch them . . . and bottle-raise the kids on either pasteurized milk or milk replacer. The virus is directly connected to the production of white blood cells, so any body secretions which contain these cells are potential sources of infection for other members of the herd.
All tests currently available evaluate antibodies. Since not all CAE-infected goats have produced antibodies, "false negatives" are possible. A goat infected with CAE but who has not produced antibodies will test negative but still can shed the virus and infect other goats. If the goat has produced antibodies, it has the virus, will test positive, and will shed it to other herd members.
Complicating the matter even more, it is also possible to have negative kids out of a positive dam. Further, a dam who has given birth to twins can produce one offspring which tests positive and another that tests negative. . . out of the same litter. Kids under six months of age are extremely difficult to test accurately for CAE, so most laboratories recommend waiting until the offspring are eight months to one year old.
CAE testing is done on blood samples drawn from suspect goats either by a veterinarian or by the goat producer. Some laboratories, such as Pan American Veterinary Laboratories in Austin, Texas (1-800-856-9655), provide collection tubes for about $1.00US each and accept ice-packed shipments of blood vials for analysis. CAE tests cost about $5.00 US per blood sample, and the results are normally available in seven to ten days. The same blood sample can also be tested for other caprine diseases, like CL and Johne's Disease, for a few additional dollars. Eight to ten cc's of blood per animal is adequate for testing. Washington Animal Disease Diagnostic Laboratory (WADDL) is another reputable facility for testing. WADDL can be reached at Post Office Box 2037, Pullman, Washington 99165-2037 USA.
Several types of CAE tests exist and have varying degrees of accuracy. The ELISA test is generally recognized as the most reliable, displaying a sensitivity to CAE of up to 95.2%; the AGID test has produced results as low as 56%. These figures may be misleading, as many variables can affect the percentage results.
Since many meat goats will be slaughtered young and humans are not at risk, why should meat-goat producers be concerned about having CAE in their herd? There are three very good reasons for maintaining a disease-free herd:
The long-term health of the herd directly affects sales and, therefore, profits. CAE-infected does produce up to 25% less milk than non-infected dams . . . assuming that they have milk at all. In production meat-goat herds, multiple births are desired, so milk production is important in raising marketable kids. Just as mastitis is not a desired condition, so is CAE. Less milk = smaller kids = reduced profit. Producers of breeding stock must offer disease-free herd sires and dams. Buyers will not pay top dollar for infected animals and will often require testing of animals prior to purchasing them. If the producer is shipping out-of-state or out-of-the-country, it is highly likely that these tests are required by animal health regulations. CAE is incurable at this time.
When buying animals to add to your herd, routinely quarantine them for a minimum of two weeks before putting them with your other goats, not just for CAE-testing purposes but also to evaluate them for shipping fever, soremouth, pinkeye, and a host of other illnesses to which goats are susceptible. Increased interest in goats world-wide, and particularly in the United States, means that lots of goats are being shipped every day. Producers who do not quarantine new purchases are asking for problems. Keeping a "closed herd" in an expansive market is difficult, so follow these minimal precautions.
Producers running hundreds or thousands of head obviously cannot afford individual testing. So be alert for knobby knees, and perform random testing annually and before kidding.
Goats can carry CAE their entire lives and never show an outward sign of it. These silently-infected animals can test negative for the antibody until stress or some other factor activates it. Don't let this incurable disease catch you off guard. Follow these simple, inexpensive steps to keep CAE out of your herd , and the entire meat-goat industry will benefit.