Caprine arthritis-encephalitis, caused by a retrovirus, is a relatively new disease of goats first diagnosed in 1974. In spite of this, CAE is now considered as one of the most important disease affecting the goat industry in the United States. All breeds of goats are susceptible to CAE, however, serological surveys indicate that the disease is most common among the dairy goat breed. CAE virus is transmitted naturally in the neonatal period from an infected adult goat to the kid through consumption of colostrum and milk. There is evidence to suggest that CAE can also be transmitted directly from goat to goat possibly through saliva, nasal secretions, urine, or feces.
Under natural conditions, the CAE virus is associated with two disease syndromes. The encephalitis form is most commonly encountered in kids 2 to 4 months of age and is characterized by paralysis that may or may not progress to seizures or death. The arthritic form is most common, and is seen in adult goats 1 to 2 years of age. Affected goats gradually lose weight and develop a poor hair coat and enlarged joints, particularly the carpal, hocks, and stifle. Early in the course of the disease, affected animals may show progressive and sometimes shifting, leg lameness, however, as the disease progresses, affected goats may walk on their knees and refuse to rise. A presumptive diagnosis can be made based on the history and clinical findings, taking into consideration the age of the animal and disease pattern. Serological tests are available for diagnosis and screening of herds.
There are no known treatments for any of the clinical forms of CAE. Animals with mild cases of the arthritic form can be made more comfortable by providing regular, correct hoof trimming, providing easily accessible feed and water, and by long-term use of oral non-steroid anti-inflammatory drugs to relieve pain (aspirin at the dose of 10 to 20 mg/kg every 8 to 12 hours and phenylbutazone at a dose of 10 mg/kg once a day). Goats with advanced cases of the arthritic form, unable to extend the legs and forced to walk on their flexed knees, should be humanely euthanized.
Before a control program can be instituted, the incidence of infection in the herd should be established using the serological test. If a herd is negative for CAE, it can be kept free of CAE by managing it as a closed herd and only introducing new genetic stock that has been tested free of CAE. Periodic herd test for CAE should be performed to monitor the herd's status. In an infected herd, culling should be considered. Kids should be removed from their dams before they are able to stand and suckle, and should be fed pasteurized goat colostrum and raised on pasteurized milk or milk replacer. Kids should also be kept separate to avoid contact with adults.