Deer can pass tuberculosis to humans, CDC warns

By Angela Betsaida B. Laguipo, BSNSep 30 2019

Tuberculosis or TB is a highly contagious infection that usually affects the lungs, but it can spread to other parts of the body, such as the spine and brain. Commonly caused by Mycobacterium tuberculosis, which can spread through the air from person to person. A person doesn’t know he or she is sick, as the bacteria can live in the host for years, without causing symptoms.

3D illustration of bacterium Mycobacterium tuberculosis. Image Credit: Kateryna Kon / Shutterstock

But, when the human’s immune system deteriorates, the bacteria can activate and cause serious signs and symptoms, including chronic cough, sometimes with blood, weight loss, fatigue, night sweats, and chills. Recently, the Centers for Disease Control and Prevention (CDC) has found that humans can acquire tuberculosis from hunting deer.

In a report published by the CDC, it says that in 2017, a 77-year-old Michigan hunter was diagnosed with pulmonary tuberculosis, caused by the agent Mycobacterium bovis. The hunter acquired the infection from an infected deer.

“The patient had rheumatoid arthritis and was taking 5 mg prednisone daily; he had no history of travel to countries with endemic tuberculosis, no known exposure to persons with tuberculosis, and no history of consumption of unpasteurized milk,” the CDC said.

The patient had hunted deer in the same location where two other hunters had acquired the infection more than 15 years earlier. The patient might have inhaled the infectious bacteria causing bovine tuberculosis while he removed the dead deer’s internal organs.

The National Veterinary Services Laboratories in Iowa performed whole-genome sequencing on the patient’s respiratory isolate, which was compared with M. bovis library, including about 900 wildlife and cattle isolates acquired since 1993. The agency found that the hunter had been exposed to a circulating strain of M. bovis, at some point through his hunting activities.

It is also possible that the hunter acquired the infection in the past and only had reactivation of infection as pulmonary disease in 2017. In the state, there had been reports of cases of the same type of TB strain in humans. In 2004, one infection occurred when a hunter injured a finder while field-dressing a deer. Another case occurred in 2002 when experts believe a hunter had inhaled the bacteria while he field-dressed a carcass.

The CDC concludes that exposure to the pathogen puts the hunters at risk for both active and latent infections. Latent infections mean that bacteria stays in the body until it becomes reactivated. This usually happens in people with a diminished immune response or those with compromised immune systems.

“To prevent exposure to M. bovis and other diseases, hunters are encouraged to use personal protective equipment while field-dressing deer. Besides, hunters in Michigan who submit deer heads that test positive for M. bovis might be at higher risk for infection, and targeted screening for tuberculosis could be performed,” the CDC warned.

“Close collaboration between human and animal health sectors is essential for containing this zoonotic infection,” it added.

What is bovine tuberculosis?

Bovine tuberculosis is a contagious disease caused by Mycobacterium bovis, which is commonly found in cattle and other animals such as elk, deer, and bison. It accounts for less than 2 percent of total tuberculosis cases in the United States.

The CDC reports that the illness has been eradicated from commercial cattle, but the bacteria may still linger in wild animals. Bovine tuberculosis, when present in humans, can affect the lungs, lymph nodes, and other parts of the body.

Though not all bovine infections progress to TB disease, those who develop TB may experience signs and symptoms like those infected with M. tuberculosis, including fever, cough, weight loss, and night sweats.

To prevent infection with the bovine tuberculosis pathogen, CDC suggests that people should avoid consuming unpasteurized dairy products, such as cheese and milk. For hunters, who are at risk of contact with body fluids and tissue of wild animals, like deer and bison, they are advised to protect themselves. If they suspect that they have been exposed to the bacteria, prompt medical attention is essential.