Back From the Vet: Caprine Arthritis & Encephalitis
CAE: What Do All These Letters Mean?
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If you have been in the goat industry for much time, it is highly likely that you have heard of CAE. Aside from being just another acronym to worry about, what exactly is it?
CAE stands for caprine arthritis and encephalitis, which is caused by a viral infection. This virus is very similar to the maedi-visna and ovine progressive pneumonia lentiviruses in sheep. In fact, it is suspected that these viruses can be shared among small ruminants. In goats, CAE is more commonly found in dairy breeds rather than meat or fiber goats. It is suspected that greater than 65% of goats test positive for the disease in industrialized countries like the US. There is evidence that the disease is less prevalent in developing countries. Due to it’s high prevalence, CAE can have a great impact on production.
Signs of this infection in goats include, unsurprisingly, arthritis and encephalitis. Adult goats affected by the virus more commonly show signs of polyarthritis, or arthritis in several joints. They can also show the more subtle signs of chronic pneumonia, and hard bag. Hard bag involves firming of the mammary tissue and decreased milk production due to the infection. While does with hard bag can still produce milk, their production will be low and their kids can do poorly. Adults with chronic pneumonia can appear simply as poor doers, not gaining well and being scruffy in appearance. In kids affected by the virus, they will show signs of neurological disease, resulting from the viral caused encephalitis. These neurological signs can be difficult to differentiate from conditions such as polioencephalomalacia, rabies, listeriosis, congenital malformations, trauma, and copper deficiency caused enzootic ataxia. Careful evaluation and testing by a veterinarian is necessary to ensure an accurate diagnosis.
Goats are most commonly infected as kids via ingestion of milk or exposure to other fluids from their virus-infected mothers. Transmission can also occur between adult goats through infected bodily fluids. Once infected, goats will be positive for the virus for the remainder of their lives. Although they can show signs of infection at a young age, many do not develop signs of disease for months to years later. These latent infections can result in a great loss in production. Carrier goats can be spreading the virus while not showing clinical signs, or appearing merely as poor doers or poor producers.
There is unfortunately no specific treatment for the caprine arthritis and encephalitis virus. Careful management of flocks is necessary to prevent the transmission or eradication the virus. When beginning a CAE control program, testing of all animals in the flock is necessary. Blood tests can be performed on all adult animals in the flock to detect antibodies to the virus. Tissue samples from deceased animals can also be submitted to be tested for the presence of the virus. Those animals that test positive can be separated from the negative animals or culled from the flock. Kids of positive does should be separated and fed pasteurized colostrum to decrease likelihood of transmission of the virus from their dams. In flocks implementing a management system, all new animals coming in to the flock should be tested for CAE. Producers should work closely with their veterinarian to develop the most effective management system for their flock.
Originally published in the November/December 2018 issue of Goat Journal and regularly vetted for accuracy.
Katie Estill, DVM, is a veterinarian consultant for Goat Journal, Countryside & Small Stock Journal, and Countryside Network. She works with goats and other large livestock at Desert Trails Veterinary Services in Winnemucca, Nevada.