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Tuberculosis Found in North Dakota Beef Herd

Breana Kiser, Agriculture and Natural Resource Agent

1-31-19 TB in NDAs you have probably heard, an investigation is underway by state veterinarians in North Dakota after a rare strain of bovine tuberculosis (TB) was identified in a beef cow herd. The current discussion in cattle circles about bovine tuberculosis certainly brings up mixed emotions. Producers always are concerned when situations are discovered that impact individual herds of cattle.

“In late 2018, we were notified that two adult beef cows originating from the herd tested positive for Mycobacterium bovis at out-of-state slaughter plants,” State Veterinarian Dr. Susan Keller says. “The National Veterinary Services Laboratory in Ames, Iowa, confirmed the TB diagnosis in the cows.”

The herd in Sargent County was later tested by state and federal veterinarians. Five more cows were found to have confirmed TB cases. There are more tests being conducted. According to officials, it was the first time this strain of TB had been found in the U.S. The type of TB is similar to cases identified in Mexican cattle.

Bovine tuberculosis is a cattle disease caused by the organism, Mycobacterium bovis (M bovis). Tuberculosis (TB) has been a major disease of humans for centuries (human strain, M tuberculosis). That bacteria is spread primarily between people. The clinical condition caused by the two tuberculosis strains are similar. This short summary is focused on the zoonotic strain found in cattle, M bovis. This bacteria can be a significant disease risk and can be transmitted to people from cattle by the inhalation of the bacteria or by drinking unpasteurized milk. In rare circumstances people can acquire the disease by eating undercooked meat from infected animals.

Bovine tuberculosis is still found worldwide but many countries have greatly reduced or even eliminated the disease from their cattle herds. Testing usually only occurs for sales or shows that cross state borders. Most cattlemen in the Mid-Atlantic region have gotten more lax regarding TB as the Eastern States have been free of this disease for a number of years. Unfortunately, despite getting very close to totally eliminating this disease in US cattle, we never quite got there in the early 1990's. Since that time there has been a steady increase in the geographic locations where the disease can be found. 

Cattle primarily shed the bacteria from nasal secretions, feces, or milk. On occasion, the bacteria can be found in urine, semen or vaginal secretions. The bacteria can survive for months in the environment under favorable conditions. Cold, dark, and moist conditions promote the organism's survival while dry, warm, sunny conditions promote the organism's inactivation. The disease is a chronic debilitating disease, characterized by weight loss, weakness and a low grade fever. The lymph nodes, especially in the head and upper air way, become enlarged, caseous, or at times calcified. In the US most animals are asymptotic and are found via testing and culling of test positive animals or control programs in exposed herds. The other common detection method is via surveillance by federal inspectors from slaughter house specimens.

At this time there is no effective vaccine and no cost effective, practical way to successfully treat infected animals. Animals known to be infected are humanely euthanized and their remains must be disposed of properly. Accurate records and traceable animal ID's are needed as a positive test triggers an investigation back to the home farm. It is extremely important to all Ag stakeholders that the source of infected animals is found and controlled as quickly as possible. Quick, accurate response and trace-backs are necessary for public health, access to domestic and foreign markets, and herd profitability. Excellent biosecurity as well as strategic testing and eradication programs will also help in the longer term goal to ultimately eliminate the disease from US cattle.

Keller said possible risk factors were not found in the Sargent County operation as there were no other cattle from Mexico found in the area, the cattle had been purchased privately and not from a large-scale sales barn and there were no employees from Mexico involved in the family business.

Keller said perhaps it's a factor that's too often overlooked that humans can spread tuberculosis to cattle or other animals.

There were no other cattle herds in the Sargent County area that had direct contact with the herd, Keller said.

She added that animals which test negative may move to slaughter, but other movements are not allowed. Cattle with the disease are put down. Meat from animals that pass inspection is safe to consume, she said.

There is a nationwide bovine tuberculosis eradication program, a cooperative state-federal effort. But because of the federal government shutdown, Keller said federal funding and field staff "are currently limited in their ability to assist."

 

 

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