As a new dairy goat breeder, I’m concerned about caprine arthritis-encephalitis syndrome affecting my herd. How can I protect my goats from this specific infection and what are warning signs of the disease?
Caprine arthritic-encephalitis (CAE) virus was initially reported in the early 1980s from young goat kids with neurologic symptoms resulting from encephalitis, aka inflammation of the brain. Coincidentally, mature goats were also developing arthritis, which would result in some goats going lame. Any joint can be affected, but the carpal joint appears to be most commonly affected.
A warning sign of the disease, especially in kids, is lameness; however, this can be variable, with some goats appearing to experience discomfort, while others walk soundly despite considerable enlargement of the joints. In addition to the two aforementioned symptoms, described clinical features of CAE syndrome, indurative mastitis (hard udder), interstitial pneumonia and progressive weight loss, have also been reported. In kids, depression, head tilting, circling, leg paralysis, body temperature increases and even blindness might also be observed clinical symptoms. Affected kids are generally humanely euthanized but oftentimes die of secondary causes, such as pneumonia. With adult goats, chronic polyarthritis pain is usually an observable sign, along with synovitis and bursitis. Infected goats also lose body condition and show coarse, dull coats.
Differentiating infection from disease is vital. It is estimated that up to 85 percent of goats don’t show clinical symptoms but rather act as a reservoir of infection to the population at large. A subpopulation of goats (approximately 10 percent) actually demonstrate the aforementioned various clinical symptoms—i.e., disease.
Since the advent of the initial serum assay, there have been progressive developments, so that new generation serology tests use the ELISA (enzyme-linked immunosorbent assay) test, which has extraordinary accuracy (99.6 percent specificity and 100 percent sensitivity). With the ELISA, it’s recommended that all resident goats in the herd be tested to achieve a CAE-free population if that is the goal of the owner. Once this is accomplished, strict biosecurity is implemented, which means all incoming goats are tested twice 30 days apart, before adding them to the herd. Sometimes it might be impractical to remove all CAE-infected goats, so heat-treating colostrum and discontinuing use of common needles and instruments between goats is recommended as they are the most common means of spreading the virus.
More recent information has verified earlier reports of interspecies spread of CAE virus and a related virus in sheep, referred to as ovine progressive pneumonia virus. Together the group of viruses is referred to as the Small Ruminant Lentiviruses. This is important when goat producers comingle their goats with sheep, as it means that both populations of animals should be tested as one group of animals. No vaccine is available for either CAE virus or OPP virus; therefore, control is dependent on herd testing using a reliable laboratory and strict bio-security when adding new replacement animals. There is no serologic or clinical evidence that humans are susceptible to CAE virus.
This article was writted by Jim Evermann, professor of Infectious Diseases, Department of Veterinary Clinical Sciences and Washington Animal Disease Diagnostic Laboratory College of Veterinary Medicine at Washington State University, and was vetted by Dr. Lyle G. McNeal.
This article originally appeared in the July/August 2014 issue of Hobby Farms.
