World Tuberculosis (TB) Day is annually celebrated today (March 24) with the hope of raising awareness about the disease and the efforts made to eradicate the global epidemic.

In celebration of the day, the Animal TB Research Group at Stellenbosch University wants to send the message that TB in animals and humans are interconnected. They emphasise that the disease in humans cannot simply be eradicated without the disease in animals also being eliminated.

The group is focused on this year’s theme: Yes! We can end TB! and have dedicated their efforts to breaking the transmission of TB that occurs between wildlife, livestock, and people.

KNP elephant killed by TB

The death of an elephant in the Kruger National Park (KNP) in 2016 takes centre stage in the group’s video that has been produced for World TB Day 2023.

In it, scientists – led by Prof Michele Miller – examine the death of the elephant. She explains how the death perplexed scientists: “Bovine TB (caused by the bacterium mycobacterium bovis) was definitively diagnosed in KNP wildlife in 1990, but this case was different. It turned out that the elephant suffered from human TB.”

This was the first time that scientists had identified a fatal case of human TB in a wild African elephant and the question was asked: How is it possible for wild animals to get infected with human TB?

“TB is often thought of as a disease that only 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 TB, reports have increasingly found reverse infection from animals to humans and vice versa.

“Infected wildlife populations, such as in KNP, can result in the spread of mycobacterium bovis across boundaries between parks or reserves to livestock in communities, and subsequently to humans. These bacteria can also contaminate soil and water and infect other species. In areas where there is a high human TB burden, such as South Africa, people may discard food or other waste which could be picked up by an elephant, which may spread human TB to these animals,” the scientists explain.

The origin of bovine TB

Bovine TB was introduced to South Africa when infected cattle were imported by early European settlers. “Primarily, it has been a disease of domestic cattle and it

was only since the 1990s that we’ve been really aware that it can spill over from domestic animals into wildlife in KNP,” says Dr Peter Buss, veterinary senior manager in KNP’s veterinary wildlife service.

It is said that currently, animal TB in the KNP affects more than 20 species, including buffalo, kudu, lion, antelope, rhinoceros and elephant.

What are the economic implications?

The group states that TB in animals not only has major health implications for South Africa, but that the disease also severely affects the economy. Many rural communities rely heavily on cattle as a food and milk source and agriculture focused on livestock is one of the major contributors to the country’s gross domestic product.

“Cattle affected by bovine TB will lose weight and produce less milk. If any infection is detected, a farm will be placed under quarantine and the animals may be slaughtered without compensation for the owner. This has a major effect on food security and livelihoods,” they explain.

Research and why it is important

The group states that the 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 stress.

Due to the limited tests available for wildlife, it has always been very difficult to diagnose bovine TB, while species-specific reagents (such as rhinoceros, elephants, and lions) are not commercially available.

The group could usually test animals only 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 using samples collected from anaesthetised animals, and testing them in the university’s laboratories.

“Stellenbosch University is taking testing to another level by looking at the epidemiology of the disease,” Buss comments.

‘One health’ approach

The Animal TB Research Group highlights the importance of further developing rapid and accurate diagnostic tools and of a ‘one-health’ approach, which recognises the interconnection between human, animal and environmental health.

“The TB problem is not a one-directional issue. If we don’t take care of the TB problem in our domestic animals and wildlife species, there may be overspill into humans and that will add to the total human TB burden,” they conclude.