What causes bovine tuberculosis (BTB)?
BTB is a bacterial disease caused by Mycobacterium bovis.
How does bovine tuberculosis differ from human TB?
BTB and human TB are different species of the genus Mycobacterium. Mycobacterium tuberculosis is the tubercle bacillus that causes Tb in humans, only occasionally spilling over into animals species like baboons and monkeys for instance, while the bovine type of tubercle bacillus, is pathogenic to man as well as animals.
Although the prime hosts of bovine tuberculosis are cattle and other Bovidae, humans can become infected when there are ready opportunities for contact with infected animals or drinking infected milk. Infection with the bovine bacillus is a zoonosis and this bacillus rarely spreads from man to man.
Which species are affected?
So far the disease has been diagnosed in the following species: buffalo, rhino, lion, leopard, warthog, baboon, cheetah and kudu.
Are some species more susceptible?
Animals that live in herds and/or prides (social animals) seem to be more susceptible because of the close contact.
Which species are most affected?
Buffalo and lion.
How is the disease transmitted?
The organism is expectorated in large numbers in sputum and is expelled in smaller numbers in droplets that can be inhaled directly from the infective animal during coughing.
How long does the organism survive in the environment?
Mycobacteria are rapidly destroyed when exposed to the harsh African climate. They are not, however, eliminated at such a rate that they do not constitute a hazard to other species as the rate of disappearance from the environment is measured in weeks rather than hours. A recent study determined the longevity of the bacteria in the open as four weeks in summer and six weeks in winter in moist shady condition. Such bacteria may be found in exudates, faeces and carcass material that has contaminated soil, water, grass or plants.
How many buffalo are infected?
The prevalence rate as determined during a survey in October 1998 was 33,8 % in the Southern Region, 14,6 % in the Central District and 1,5 % in the Northern and Far Northern Region.
If humans can contract bovine tuberculosis, are tourists not at risk?
Because tourists do not get into close contact with the main carriers (buffalo), this disease is not seen to pose any threat to them.
What is KNP management doing about the disease?
So far, the disease has only been monitored without any active intervention. A programme has been initiated to breed disease-free buffalo. The programme involves capturing pregnant BTB-free buffalo cows in the far-northern areas of the KNP and accommodating them in quarantine bomas under tick-free conditions at Skukuza. The calves from these cows are weaned at an age of 4-6 months to assure them free of foot-and-mouth disease. They then undergo various diagnostic tests and a separate quarantine period away from the cows to determine their disease status.
What happens to the disease-free calves?
The disease status of a calf will determine its destination: a disease-free calf (the ideal) can go to any national park or game reserve; a Corridor disease positive calf can only go to Vaalbos and Highveld, while foot-and-mouth diseased calves would have to be sold to farms within the Red line.
The other national parks such as Dongola, Marakele and Highveld need the buffalo to optimise their conservation and tourism potential. It is further essential to have buffalo populations in other national parks, to enable restocking of the KNP should the buffalo population need to be replaced.
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Susi Anderson
African Insight 