Raising goats? Be mindful of health threat

Sarah Mills-Lloyd
While it is rare for humans to become infected with Caseous lymphadenitis (CLA), the likelihood of human infection will increase due to occupational exposure and consumption of raw goat milk.

Wisconsin is known as America’s Dairyland. It is widely accepted Wisconsin is the leader in the dairy cow industry, but not everyone knows Wisconsin leads the nation in milk goat animals.

According to a United States Department of Agriculture National Agriculture Statistics Survey State Agriculture Overview as of January 2019, Wisconsin has 72,000 head of milking goats. Most of the milk from these animals is used for making award-winning cheese that appeals to consumers across the nation.

If you are thinking about expanding or diversifying into dairy or meat goats, you need to consider the health status of the animals you purchase.

Caseous lymphadenitis (CLA) caused by the bacteria Corynebacterium pseudotuberculosis generally causes an abscess to form around the head and neck area. Although less common, this organism can also cause an internal abscess to form in the lungs, and may be present in goat milk which may cause a high somatic cell count.

The most common form of CLA, the subcutaneous abscess, can infect other animals in the herd. The infectious material from the abscess can be transmitted by direct contact with an infected animal or through contaminated objects such as board slats on feeders, equipment, or flies. The disease may also be spread through the herd via infected colostrum.

According to Michigan State University, “the prevalence of CLA in the commercial goat herds may be as high as 30 percent.” Animals infected with the internal form of CLA may have weight loss leading to a diminished average daily gain and lower milk production. In meat animals, the presence of internal CLA is a common reason for carcass condemnation at slaughter.

Corynebacterium pseudotuberculosis can survive for months in the soil and environment.

Testing options

If you are concerned about CLA, two testing options exist for a diagnosis of CLA. According to the American Institute for Goat Research at Langston University, “there are many causes of an occasional abscess, so do not panic and cull the goat; you should culture and identify the cause.” A sample from an individual animal’s abscess may be submitted through your veterinarian for a bacterial culture, which will identify the causative CLA organism.

If you would like to determine the herd status or screen an incoming group of animals, it is best to use serologic (blood) testing. The serologic tests are good at determining the prevalence—the proportion of a population who have or had a specified disease in a given time frame—of the disease; however, interpretation of the serologic test results should be interpreted with a level of caution. It is best to consult with your veterinarian after results have been finalized.

A CLA vaccine is available. There has been anecdotal evidence shown for the reduction of abscesses in a vaccinated herd with endemic CLA; however, the vaccine alone is not enough to eradicate the disease in a herd.

It is important to note, vaccinated animals will test positive on any serologic (blood) test; therefore, it is important to work with your veterinarian to develop a strategic plan to eliminate the disease, if present. Maintaining or establishing a closed herd is the best preventative strategy.

CLA is a chronic condition for goats. If purchasing new animals, perform a screening diagnostic test for the disease and quarantine new additions. Separate animals with active CLA lesions from healthy animals until healed, and disinfect equipment and pens. Developing and implementing farm biosecurity protocols are key to preventing and limiting the spread of CLA. 

It is rare for humans to become infected with CLA. However, the likelihood of human infection will increase due to occupational exposure and consumption of raw goat milk. The Wisconsin Department of Health Services discourages human consumption of unpasteurized milk due to the high potential for transmission of zoonotic diseases.

Mills-Lloyd, DVM is the University of Wisconsin-Madison Division of Extension Agriculture Agent—Specializing in Dairy and Livestock for Oconto County.

Sarah Mills-Lloyd