Understanding chronic arthritis of goats

By Henrylito D. Tacio

 

The livestock industry is one of the fastest growing agricultural sectors in the Philippines and other parts of Asia.  It is a vital industry linked to millions of jobs in related industries. However, the health and growth of this industry are being threatened by the emergence of animal diseases.

 

One animal disease that is getting attention among goat raisers is the caprine arthritis encephalitis (CAE), a viral infection of goats which may lead to chronic disease of the joints. It sometimes also causes encephalitis in kids less between two and six months old.  This disease was first diagnosed in goats in 1974. Since that time, it has been diagnosed in North America, Europe, Kenya, Peru, Australia, and New Zealand.

 

According to the Taiwan-based Food and Fertilizer Technology Center for the Asian and Pacific Region, the disease was introduced into the Philippines through the importation of 54 goats from the United States (bought from Texas) in 1998.

 

A serious disease for the goat industry, CAE adversely affects health, production and life expectancy in both dairy and meat-type goats.   CAE has a long incubation period lasting from a few weeks to many months.  Infection usually lasts for life.

 

CAE is caused by a virus that doesn’t infect only goats but sheep as well.  The CAE virus is intimately associated with white blood cells; therefore, any body secretions which contain white blood cells are potential sources of virus to other goats in the herd,” warns the Washington Animal Disease Diagnostic Laboratory (WADDL) of the Washington State University.

 

Primarily, the CAE virus is transmitted to kids via colostrum in the first few feedings after birth.  Blood (examples: contaminated instruments and open wounds) is regarded as the second most common way of spread. “Contact transmission between adult goats is considered to be rare except during lactation,” WADDL assures.

 

In a milking herd, shared milking machines, milk contaminated hands or towels can also increase the risk of spreading the disease.  In a meat herd, transmission can occur via needles, tattooing instruments or dehorning equipment.  Other possible methods of transmitting the disease include head butting to the point of drawing blood, eye-licking, biting, snorting and coughing, and urinating too near another goat’s race. 

 

Gail Bowman, coordinator for the International Boer Goat Association for the Northwestern United States who has contacted extensive research on the disease, found out that the risk of infection during sexual contact between the animals is possible in the exchange of saliva, estrus mucus, urine, semen, and nasal secretions.

 

The Merck Veterinary Manual claims that only 30 percent of infected animals develop a disease.  There are three different forms of the disease: arthritis, mastitis, and encephalitis.  Symptoms of arthritis include lameness, weight loss despite a normal appetite, poor hair coat, and reduction of milk yield.   Arthritis is mainly visible on the carpal joints and may also involve the tarsal joints.

 

Mastitis, on the other hand, is characterized by a hard, hot and probably uneven udder with a dejected look and blood in milk.  Signs of encephalitis include weakness, coordination disorders, and paralysis of hind limbs.  Among kids between two and four months, there is complete paralysis.  Lung involvement results in chronic pneumonia.

 

Since not all goats that become infected with CAE virus progress to disease, it is important to test goats routinely for infection by means of a serology test which detects viral antibodies in the serum.  Bowman cautions, “However, CAE virus infection may not be serologically testable for months or years, and some infected animals that can transmit the disease may never show clinical symptoms at all.”

 

A concern among Filipino consumers is whether it is alright to drink milk containing the CAE virus.  The WADDL assures, “There is NO evidence that the CAE virus is transmissible to humans.  However, there are other serious human pathogens which have been transmitted through raw milk.”

 

Chris Cyr, of the Indiana Animal Disease Diagnostic Laboratory of Purdue University, and Bowman have listed the following recommendations to help control CAE virus in goat herds:

 

1. Remove kids from their dams immediately after birth to prevent contact with nasal secretions and nursing. “Be sure to prevent the does from licking their kids,” Bowman adds.  “Then take the kids inside and wash them in warm water, in a clean sink.”

 

2. Feed kids only pasteurized milk and heat treated colostrum.  CAEV can be inactivated by heating colostrum at 56 degrees C (133 degrees F) for 60 minutes.  Temperatures lower than this failed to prevent disease transfer.  Using cow’s milk and colostrum is acceptable if it is also heat treated and pasteurized to prevent other neonatal infections.

 

3. Establish a serologic surveillance program.  “Testing every 6 months appears sufficient in small herds with low seroprevalence,” Cyr says.

 

4. Separate all possibly infected animals from uninfected animals by a double fence with at least 10 feet between the fences.  “Do not use common feeder, waterers or salt blocks,” Bowman points out. 

 

5. When possible do not breed infected animals to uninfected animals.  “If negative and positive animals are mated, use a single hand-mating allowing minimal oral contact,” Bowman suggests.

 

6. Avoid transmission by disinfecting equipment. — ###

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