Understanding CAE
(Caprine Arthritic Enchephalitis)
by Marilyn Grossman

CAE can manifest itself in many ways. The most common is enlarged knees and hocks. Over time, the infected goats develop lameness, often crawling around on their knees. Goats lose condition and usually have poor hair coats as chronic wasting ensues. As the arthritis worsens, hind limbs often become weak and sway. Another common symptom is chronic pneumonia. Another is chronic mastitus. Some does will freshen with a hard udder that usually softens within a few weeks of freshening, but the does remain low milk producers. Bucks can retain fluid at the poll. All of these symptoms become progressively worse as a goat ages. Infected goats may exhibit any combination of these symptoms. And sometimes they exhibit no symptoms at all.

Testing for CAE
There are 2 methods of testing available for CAE. The most readily available test, AGID, is less sensitive and has about a 60% accuracy. The ELIZA test is much more accurate. Washington State University is the only lab that uses goat antigen (other labs use sheep) in their ELIZA method, and reports a 95.2% accuracy. Information on their testing procedures can be obtained by calling 509-335-9696.

However, the test is measuring antibodies produced by the goat, and does not test for the virus itself. Goats can carry the virus without producing antibodies. Usually, some stressor activates the production of antibodies. Stressors can be: a difficult kidding, a serious injury or illness, changing homes, inclement weather, poor quality feed, etc. As with us humans, what is stress to one is not necessarily stress to another. This is how you can get a "false" negative result on a CAE test.

It is highly unlikely that an animal that tests positive could test negative at a later time. They only exception is when testing young animals. Feeding heat treated colostrum from does producing CAE antibodies can cause a kid to test positive, then the kid can test negative after several months have passed after weaning. Therefore, it is more reliable to wait until a kid is past 6 months old to perform the test.

Transmission
This is the hard part. CAE is passed through white blood cells. White blood cells are in body secretions (milk, blood, saliva, urine) in varying concentrations. It is most concentrated in colostrum, followed by milk, blood, and to a much lesser degree, saliva and urine. There is much speculation on just how infectious it is, and under what circumstances it is transmitted. The only certainty at this time is that when a kid nurses a CAE positive doe, the kid then becomes CAE positive.

There are many ways that are strongly believed to be probable means of infection: head butting that causes scurs to break and bleed, open wounds, sharing needles, adult animals drinking milk, milking a negative animal after milking a positive animal, a kid swallowing uterine fluid in a long, difficult kidding. Lateral transmission (casual contact) is more speculative. This would be: sharing feed troughs and water buckets, body secretions on hay or straw, milk on the ground either spilled or from a leaking orafice.

The key on lateral transmission is the amount of contact the animals have with each other. I read an article in the UCN by Dr. Lauren Acton, DVM. She likens lateral transmission to a box of marbles. Marbles with wet paint on them would be the positive does and the clean ones would be the negative does. Now consider how many marbles are in the box and what percentage have wet paint on them. Roll the marbles around in the box and see how many of the clean marbles end up with wet paint on them compared to how many had the wet paint to begin with. A good argument for avoiding over-crowding!

Prevention Program
Kid rearing is the most important means of controlling CAE. Kids should be taken from their dams at birth and fed heat-treated colostrum. Heat treatment is done by heating colostrum to 133 - 138 and hold at this temperature for one hour. I use a Presto Kettle filled with water. I heat the colostrum to 135 and put in pre-heated pint jars. When the water in the kettle is at 138, I put the jars of colostrum into the kettle, cover with the lid, and hold for one hour, stirring about every 10 minutes. (Kids need a minimum of 2oz of colostrum per pound of body weight within the first 24 hours of life) Then feed pasteurized goat milk until weaning. Milk can be pasteurized by heating to 165 and holding for 15 seconds.

It is best to have one person responsible for kid care. We all get over-tired during kidding season. Confusion as to which colostrum has been heat-treated, which bucket of milk has been pasteurized can be the downfall of a prevention program. When in doubt, re-do. One wrong feeding can undo all of the other work you've done.

Head butting is unavoidable, especially during breeding season. Put extra care into disbudding your kids to reduce the likelihood of scurs. Use a separate needle for each injection for each goat. Avoid over-crowding. Goats that are in continual contact with each other increase the likelihood of transmission by the less viable means.

Eradication
Each of us must decide what measures we will take to control CAE. Clearly, it is advisable to buy from herds with a CAE prevention program. Some people house their positive goats away from the negative ones. Some people cull any goat that tests positive. Some people maintain a closed herd….that means no new goats, no shows, no fairs, no contact with outside goats. Others exercise caution by hand raising kids and limiting their goats' exposure to other goats. There are many different management styles for controlling CAE due to the speculative nature of transmission.

Very few (personally, I don't know of any) people have herds that every goat tests negative year after year. America simply has a high incidence of CAE in its goats. The more precautions you take, the more likely it is you will have a lower incidence of CAE in your herd.