Interconnected: Human and animal TB part of the same problem

Tuberculosis (TB) in humans cannot be eradicated unless TB in animals is also eliminated, as these two diseases are closely interconnected.
This is the central message the Animal TB Research Group at Stellenbosch University’s (SU) wants to convey on World TB Day.
World TB Day is observed annually on March 24 to raise awareness about TB and the efforts made to end this global epidemic. The date marks the day in 1882 when the bacterium causing TB was discovered and this year’s theme is “Yes! We can end TB!”
The main focus of the Animal TB Research Group, situated within SU’s Faculty of Medicine and Health Sciences (FMHS), is to break the transmission of TB that occurs between wildlife, livestock, and people.
In a video produced for World TB Day 2023, scientists examine the death of an elephant in the Kruger National Park (KNP) due to TB in 2016.
Prof Michele Miller, who leads the group, says the death of this elephant perplexed scientists. “Bovine TB (caused by the bacterium Mycobacterium bovis) was definitively diagnosed in the KNP in 1990, but this case was different. It turned out to the elephant suffered from human TB.”
This was the first time that scientists had identified a fatal case of human TB in an elephant. But how is it possible for wild animals to get infected with human TB?
“TB is often only thought of as a disease that affects humans, when in fact it is a multi-host disease,” explains Miller. Although animals are typically infected with Mycobacterium bovis and humans with Mycobacterium tuberculosis, reports increasingly found reverse infection from animals to humans and vice versa.
“In a wildlife park Mycobacterium bovis crosses the border from buffalo herds to goats and cattle, soil and water and subsequently to humans themselves. And people with a high TB burden who for example feed elephants in wildlife parks can spread human TB to these animals,” the scientists explain.
Origins
Bovine TB was introduced in South Africa when infected cattle were imported during the first European settlement. “Primarily, it has been a disease of domestic cattle and it is only since the 1990s that we’ve been really aware that it can spill over from domestic animals into wildlife,” says Dr Peter Buss, Veterinary Senior Manager in KNP’s Veterinary Wildlife Service.
Today animal TB in the KNP affects more than 20 species, including buffalo, kudu, lion, antelope, and elephants.
Economic implications
TB in animals not only have major health implications for South Africa, but also severely affects the economy. Many rural communities rely heavily on cattle as a food and milk source and agriculture focussed on livestock is one of the major contributors to the country’s gross domestic product (GDP).
Cattle affected by bovine TB will lose weight and produce less milk. And if any infection is detected, a farm will be placed under quarantine and the animals will be slaughtered with no compensation for the owner. This has a major effect on food sources.
Importance of research
Early detection of TB is extremely important for both economic and health reasons. “To do that, we have to be able to determine whether animals are infected by Mycobacterium bovis,” the scientists explain.
It has always been very difficult to diagnose bovine TB due to the limited tests that are available. Species-specific reagents (for instance for rhinos, elephants, and lions) are not commercially available.
Initially the group could only test animals after their demise, either due to natural causes or from clinical symptoms of TB, but their research has since enabled diagnosis in living animals, and in multiple species. This is done samples collected from anaesthetised animals, and testing it in SU laboratories for the presence of the TB pathogen.
“SU is taking testing to another level by looking at the epidemiology of the disease,” Buss comments.
TB One Health approach
The Animal TB Group highlights the importance of the further development of rapid and accurate diagnostic tools and of a “One Health” approach, which recognises the interconnection between human, animal and environmental health.
“We are saying that the TB problem is not a one-directional issue. If we don’t take care of the TB problem in our domestic animals and in our wildlife species, there will be overspill into humans and that will add to the total human TB burden,” they conclude.

[@adridave1]

😞 interesting and complicated. Educational.