Tuberculosis: Still a real possibility
Almost from his very first day on John’s dairy farm, Travis was one of John’s most dependable employees. A young, strong guy, he was always on time and was glad to take on extra milking duties. But lately, Travis hadn’t been looking nor acting very healthy.
A couple weeks ago, John noticed Travis had developed a cough. Hmm, he thought. Maybe Travis has caught what’s going around.
As the days went on, John noticed his employee’s cough wasn’t going away. He could hear Travis’ hacking spells over the loud buzz of the parlor’s milking equipment. He seemed tired and was losing weight. John assigned him work outside with the young calves, thinking some fresh air might help him kick this bug.
It finally reached the point that John convinced Travis to see the doctor. After a chest X-ray and a few tests later, a surprising diagnosis was made: tuberculosis. Travis thought, tuberculosis? Haven’t we eradicated tuberculosis? He started a lengthy antibiotic treatment that put him on the road to recovery.
When John heard Travis’ diagnosis, questions ran through his mind. Could this disease affect the health of his other employees, his family, and himself? After mentioning this to his veterinarian, questions arose about the health of his cattle. The veterinarian reminded him tuberculosis is something that’s still out there in cattle. It’s possible, but not common, that tuberculosis could even be passed from animals to people or vice versa.
John became a tuberculosis expert rather quickly. He found out that tuberculosis is a bacterial disease. Human tuberculosis is usually caused by the Mycobacterium tuberculosis strain, while cattle are usually affected by the Mycobacterium bovis strain. What’s more, these strains can cross over between cattle and people. In fact, Travis’ tuberculosis was caused by the M. bovis strain!
John also found out that tuberculosis wasn’t something most people knew much about. After all, only a handful of human tuberculosis cases are found each year in his state. His state’s livestock had been tuberculosis-free since before John was born.
But the story is different in other parts of the world. Tuberculosis rates are higher in both people and cattle in most countries outside North America. Human tuberculosis spreads more readily there (through inhalation of bacteria that’s been coughed out by infected people), and treatment is not often accessible. Tuberculosis in cattle and other species is much more common, too. Cattle strains frequently pass from animal to person when raw milk or uncooked infected meat is consumed. Travis had recently taken a mission trip abroad, and admitted to John that, yes, he frequently drank unpasteurized milk offered to him by his hosts.
Travis’ Mycobacterium bovis infection particularly worried John. Could his cows have transmitted tuberculosis to Travis? Could Travis have spread tuberculosis to his cows? If so, this could be something that could put him out of business.
John spoke with his state animal and public health officials. Right now, this was simply a case of human tuberculosis. The cows weren’t sick and he’d never had any cull animals identified as infected upon inspection. He wasn’t required to do anything with his cattle. He could let all this pass and go on with business as usual.
In the end, John couldn’t stand not knowing if his cattle could be a source of future problems for his employees and his family. He arranged for a whole-herd tuberculosis test of all his animals. He also encouraged his employees to get tested too. Several days later, John could breathe a sigh of relief as his herd – and employees – all tested negative.
This seemingly far-fetched scenario has only been somewhat modified from the experiences of a real dairy farm in our region. This dairy’s experiences were presented at last week’s South Dakota “One Health” meeting at the USD Medical School in Sioux Falls. The story helped the human and animal health professionals in attendance understand the real-world issues surrounding tuberculosis in people and animals.
Our human and animal health professionals in the US have reduced tuberculosis cases to a level where they’ve become more oddities than everyday events. But that’s not the case in many other parts of the world, making tuberculosis something that all of us have to stay on the lookout for.
Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached via e-mail at email@example.com or at 605-688-5171.