If a goat has a chronic disease that’s obvious, it’s easy to make a decision to cull that animal. However, if a goat is potentially harboring a disease without showing any clinical signs, farmers aren’t as likely to eliminate the animal because it appears healthy and remains productive.
Caprine arthritis encephalitis (CAE) is a goat disease that has forced many long-term goat breeders to make management changes. The virus responsible for CAE is closely related to the lentivirus that causes ovine progressive pneumonia in sheep. The word lentivirus is partly derived from “lentus,” the Latin word for slow, which is a good description for a virus that has a long incubation period.
This extended incubation period is what makes CAE so challenging for the producer. Animals become infected with CAE through the ingestion of colostrum or milk of infected animals. However, even after exposure to the CAE virus, the animal may not test positive or show signs of the disease for years. Many goat dairies test regularly for CAE, but a negative test isn’t a guarantee that an animal is negative. Various estimates indicate that CAE is present in as many as 75 percent of goat herds.
The test for CAE measures antibodies to the disease, and because not every goat that is infected with CAE is producing antibodies, it’s possible to get false negative results. The goat still has CAE, and will always have CAE, and it may test positive or show clinical signs in the future.
Although CAE manifests in several different ways, the most common clinical sign for positive goats is the arthritic form that appears in adult animals. Infected adult goats may exhibit clinical signs suddenly, or can live for several years before the disease affects them. In some goats, the arthritis is minor and almost unnoticeable. CAE in adult goats also causes chronic weight loss, pneumonia, hardened udder and loss of production.
In some cases, animals infected with CAE may harbor the virus but never show clinical signs. These animals shed the virus and are a potential source of infection within the herd. In a herd where CAE remains subclinical, or where animals don’t seem to be affected, the herd owner may eventually notice that animals aren’t producing well, and that the cull animals are younger than in the past.
There are several management steps to help keep CAE at bay, although there is no single method that guarantees a herd that’s free of the disease. First, newborn kids are isolated immediately after birth and not allowed to suck on the doe. All kids receive heat-treated colostrum (heated to 113 degrees for 60 minutes). Use a thermometer to check the temperature during heat treatment. If kids will be raised on goats’ milk, the milk should be pasteurized at 165 degrees for 15 seconds. Some producers add colorant to pasteurized goat’s milk so that workers on the farm don’t mistakenly feed unpasteurized milk.
All animals entering the herd should be tested for CAE prior to moving onto the farm. This step can make it difficult to increase the herd size or add outside animals, but it’s the only way to reduce the risk of introducing CAE. Once all the animals on a farm are on a regular testing schedule, and annual or biannual tests yield no positives for CAE, maintaining a closed herd is the best option to prevent future infection.
Although testing for CAE is not particularly costly, some producers elect not to test and rely on managing the herd for optimum nutrition and health. Some producers raise all young stock in a separate area, or even another farm, so kids and young does are not exposed to potential CAE carriers.
Many people who raise meat goats for the slaughter market have not been concerned about CAE because the disease is more prevalent in dairy goats. However, many meat-grade goats used to produce market kids are the result of dairy crosses, and thus are more likely to have CAE. Meat goats or meat goat crosses infected with CAE may never show clinical signs of disease, but may have reduced milk production, resulting in lower weaning weights and low gains for kids.
The author is a frequent contributor and freelance writer who farms and raises Great Pyrenees in south-central Pennsylvania. Comment or question? Visithttp://www.farmingforumsite.comand join in the discussions.