Does this rhino have tuberculosis? Now there is a simple test

The survival of white rhinos hangs in the balance. As well as poaching, habitat loss and climate change, they are also threatened with bovine tuberculosis (bTB), caused by Mycobacterium bovis (M. bovis). Cattle imported to South Africa in the 1880s brought bTB to South Africa. In the Kruger National Park, the infection was first identified in buffalo herds in the 1990s and has since been detected in 15 other species, including rhinos, cheetahs and lions¹.

“It’s now endemic,” says Sven Parsons, a research veterinarian with Afrivet. “It is well established in many species.”

The presence of M. bovis in wildlife populations adds another challenge to conservation programmes, which heavily depend on animal relocation. “The Kruger National Park has historically exported rhinos to repopulate other protected areas or enhance the genetic diversity of other populations,” says Parsons, who conducted this work while at the University of Stellenbosch in South Africa. “Being able to declare an animal free of infection plays a very important part in these efforts.”

Until recently, conservationists lacked suitable tools for assessing the bTB status of rhinos. But a unique collaboration between wildlife researchers in South Africa and Mabtech, a Swedish biotechnology company specializing in monoclonal antibodies, has brought a solution.

The challenge of bTB detection

South Africa’s national and private game parks, along with the expansion of wildlife ranches, have increased the risk of bTB transmission between livestock and wildlife.

“It’s a multi-host disease,” says Michele Miller, a wildlife veterinarian and expert in animal infectious diseases at the University of Stellenbosch, who lives and works in the Kruger National Park. “If it’s not identified and managed, it can spread to other species — including other wild animals, domestic animals and potentially even to humans if they come into contact with infected animals and don’t take suitable precautions.”

It is difficult to know how bTB affects the overall health of wild rhinoceros. Evidence suggests they are infected for many years before developing any clinical signs of the disease. But infection does create a significant challenge for conservation efforts.

“In the Kruger National Park, quarantine is currently imposed on rhino populations,” says Parsons. “That means rhinos can’t be moved to other locations without testing, to ensure they do not spread the disease elsewhere.”

Rhinos at the park are held in secure pens while they undergo bTB testing over a three-month period. Only if the animal has negative test results can it be safely relocated. But methods of detecting the infection in other species have been deemed unreliable for rhinoceros.

A blood-based assay

Miller and Parsons set out on a mission to develop alternative screening tools that could easily and reliably detect bTB in rhinoceros. They looked towards the interferon-gamma release assay (IGRA), a blood test initially developed to diagnose bTB in cattle. It works by measuring the levels of interferon-gamma (IFN-γ), a molecule released by certain immune cells, after stimulation with M. bovis proteins in a blood sample.

“The approach is fairly standard,” says Parsons. “It’s a very established diagnostic protocol.”

The IGRA relies on high-quality matched pairs of capture and detection monoclonal antibodies, which bind to different parts of IFN-γ.

“Monoclonal antibodies are versatile tools used to capture and detect small molecules originating from the body,” says Niklas Ahlborg, an immunology expert and senior advisor at Mabtech. “They have several applications but are often used to measure compounds in the blood.”

Mabtech specializes in the development of immunoassays for detecting or measuring specific compounds produced by the immune system. While the company had monoclonal antibody pairs available for detecting IFN-γ in several different species, these were mainly for animals used in research; it did not have specific antibodies for rhinoceros. However, given the evolutionary conservation of many proteins, it was possible that a kit developed for a closely related species might be effective.

“Rhinos fall into the same taxonomic category as horses,” says Miller. “So that seemed like our best option.”

Miller and Parsons explored the Mabtech equine IFN-γ ELISA Pro kit for use as part of a potential IGRA assay for diagnosing M. bovis infection in white rhinoceros². After reading their publication, Mabtech contacted the researchers to offer support.

“They were very eager to help us,” says Miller. “In particular, when we were testing the antibodies for the rhinoceros assay, there was an additional step that was necessary. They went the extra mile and performed that step for us, helping standardize and ensure the high quality of the reagents we were working with.”

It turned out that rhinos were only the start. Miller has discovered that Mabtech’s cow kit can be used to detect bTB in African buffaloes³, and its domestic cat kit can be used in cheetahs⁴ and lions⁵. Josephine Chileshe, who helped Miller and Parsons develop the test as part of her PhD, is endeavouring to develop a similar diagnostic test for bTB in Canadian bison.

“In many wildlife projects, we often have to make our own reagents in-house, which is a costly and time-consuming process,” says Miller. “Using a validated test with commercially available reagents and stringent quality control increases our confidence in the results.”

Fruitful collaboration

Partnerships between academics and companies in niche fields like wildlife health can be challenging due to limited commercial opportunities.

“Our experiences of working with Mabtech have been very positive,” says Parsons. “They’ve been very eager to help us, not just by providing kits, but also offering their hands-on expertise.”

This remarkable collaboration highlights the crucial role that cutting-edge diagnostics play in preserving the biodiversity of South Africa and beyond. Thanks to the development of these simple and reliable blood tests for btB, scientists and veterinarians can now easily detect the infection in various wildlife species, supporting conservation initiatives around the world.

“From a purely academic perspective,” Parsons concludes, “working from the molecular level all to the way through to an ecological level is very rewarding.”