Zimbabwe at risk of Zoonotic TB in humans

THE removal and vandalism of perimeter fences separating wildlife reserves from grazing areas for domestic animals as well as human habitats in most communal areas in Zimbabwe, poses a risk of transmission for Bovine Tuberculosis, a renowned Veterinary expert has said.

In 2019, President Emmerson Mnangwga announced that government would erect perimeter fences around national parks as part of measures to reduce human-wildlife conflict which if left unchecked, could lead to the uncontrolled spread of Zoonotic diseases such as Bovine Tuberculosis also known as Zoonotic TB.

A Zoonotic disease or zoonosis according to the American Centre for Diseases Control (CDC), is an infectious diseases of humans caused by a pathogen that can jump from a non-human to a human and vice versa. Zoonotic Tuberculosis or Bovine Tuberculosis (BTB), has over the years been endemic in wildlife, mainly the African Buffalo in the Southern African region, including Zimbabwe. Sabinet African Journals estimates the Buffalo population in Zimbabwe to be around 48,200.

In Zimbabwe, Zoonotic TB was first identified in Buffaloes in Gonarezhou National park in 2008. However, recent data from the Zimbabwe Parks and Wildlife Management Authority (ZIMPARKS) shows that the disease is no longer just endemic in Buffaloes, but has spread amongst other wildlife species. In 2022, ZIMPAKRS reported that two female lions had succumbed to Tuberculosis in Hwange National Park.

Though not highly reported or talked about, Zoonotic TB is equally fatal and according to the World Organisation for Animal Health (WOAH), it is slow and takes months or years to reach the fatal stage in animals. However in humans, an estimated 12,000 people die every year, while 147,000 new cases of zoonotic TB are recorded in people globally, according to the World Health Organisation (WHO). The African region carries the heaviest burden on Zoonotic TB, followed by the South-East Asian region. Zoonotic TB is caused by Mycobacterium bovis and is believed to have originated from domesticated cattle.

In an interview with HealthTimes, Dr Canaan Tinashe Hodobo, the Head of Molecular Biology at Zimbabwe’s Central Veterinary Laboratory, said while the quantum of Zoonotic TB cases in Zimbabwe could not be established at the time of the interview, the increased interaction of humans and wildlife was fertile breeding ground for Zoonotic TB.

The disease can be transmitted through respiratory secretions or the ingestion of contaminated food or water. The removal of fences between wildlife and domestic cattle in Zimbabwe has created a porous interface, increasing the risk of transmission. This means that the bacteria causing bTB can pass from buffaloes to cattle and potentially to humans. NB: there have been recent efforts to rehabilitate the game fences,” said Dr Hodobo.

“In 2008, the first isolation of bTB in buffaloes was reported in Gonarezhou National Park. The interface between wildlife, domestic animals, and humans plays a crucial role in the spread of zoonotic diseases. However, the origins and detailed history of zoonotic TB in Zimbabwe remain unclear.”

He added that BTB was not confined to African buffaloes or wildlife only as cattle, and other domesticated animals were more likely to carry the bacteria responsible for bovine tuberculosis.

Risk Factors for Zoonotic TB

While the most common route of transmission of M. bovis to humans is through contaminated food (mainly untreated dairy products or, less commonly, untreated meat products), airborne transmission also poses an occupational risk to people in contact with infected animals or animal products, including farmers, veterinarians, slaughterhouse workers and butchers.

Dr Hodobo cautioned citizens against consuming meat that has not been screened for infections at the laboritories.

“Zoonotic TB can be transmitted from animals to humans through close contact, such as handling or consuming infected animals or their products. Human-animal interaction, particularly in areas where livestock and wildlife coexist, increases the risk of transmission. It is not safe for humans to consume meat from an animal that has bovine tuberculosis at the time of slaughter. The bacteria can survive in meat and pose a significant risk of transmission through ingestion. Therefore, it is advisable to avoid such meat,” said Dr Hodobo.

In other parts of Africa such as Masai communities of Kenya and Tanzania in East Africa where the drinking of unpasteurised milk and eating of blood from livestock is a revered tradition, the incidence of Zoonotic TB is high according to studies. Eating undercooked meat or raw meat also increases the risk of Zoonotic TB infection.

Zimbabwe’s lab capacity to screen for Zoonotic TB

Dr Hododo said there is capacity of local abattoirs and meat production companies to screen carcasses or animals for bovine tuberculosis.

“There is deliberate surveillance through inspection going on in abattoirs in the presumed High-risk areas. Inspection is basically visual during antemortem and postmortem inspections, i.e., checking for TB symptoms and lesions.

“However, the capacity of local laboratories to screen for Zoonotic TB in animals is limited. There are plans to enhance the capacity of local labs for disease screening, including Zoonotic TB, as part of the One Health program, but such plans are not explicitly stated. The Directorate of Veterinary Services (DVS) is raising awareness of Zoonotic TB. Through the agricultural show and any exhibition opportunities. There is deliberate surveillance going on in abattoirs in the presumed High-risk areas. The people also generally encouraged to consume boiled meat.”

To address Zoonotic diseases such as Bovine TB and the possibility of resistance to TB treatment and Antimicrobial Resistance (AMR) in general, Zimbabwe has started developing its 2.0 One Health AMR National Action Plan the (NAP) 2023-2027, to replace the previous NAP (2017-2021). The process is being led by the Ministry of Health and Child Care (MoHCC), Ministry of Lands, Agriculture, Fisheries, Water, Climate and Rural Development and the Ministry of Environment with support from the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO. Updating NAP will help determine the necessary interventions to address AMR, leaning on a comprehensive “One Health” approach and promoting cooperation and coordination between sectors at the national level.

Research on Zoonotic TB in Zimbabwe

Dr Hodobo said while the prevalence and incidence of Zoonotic TB in Zimbabwe have not been clearly determined, further research and studies are needed to understand the current status of bovine tuberculosis in the country.

Stop TB Partnership Zimbabwe official and Jointed Hands Welfare Organisation (JHWO) Executive Director, Dr Donald Tobaiwa said there is need for more research around Zoonotic TB in Zimbabwe.

“You find that Zoonotic TB is bigger than we think. It is more than just animal and human interaction but can go as far as affecting human, animal and plant health. There is need for more research around the subject so that we come up with an in-depth study that could influence policy,” said Dr Tobaiwa.

In 2014, the WHO’s End TB strategy was adopted by the World Health Assembly as part of the newly established Sustainable Development Goals (SDGs). These goals aim for a 90 percent reduction in deaths caused by tuberculosis deaths by 2030, compared with 2015 levels. However, to meet the international goal passed by the World Health Assembly to effectively end TB as a public health threat by 2030, the world cannot ignore zoonotic TB.

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