Dr. Markus Hofmeyr
Veterinary Services, South African National Parks, Skukuza, Mpumalanga, South Africa
The veterinary field within wildlife parks in South Africa is filled with practical and academic challenges. As a veterinarian in the South African National Parks, you are a member of a multidisciplinary team consisting of scientists, wildlife managers and state authorities, who all have to take part in the final decision making and implementation of disease control plans. This inherently makes the final plan of action in dealing with emerging diseases, such as bovine tuberculosis (BTB) in wildlife, difficult because of limited knowledge of the disease and practical, scientific, emotional and ethical issues often conflicting with each other.
Bovine tuberculosis in the African buffalo (Syncerus caffer) in the Kruger National Park (KNP) will be used as an example of challenges facing wildlife veterinarians.
The first positive diagnosis of BTB in an African buffalo in the KNP was made in July 1990. A 2-yr-old buffalo bull was destroyed in the south west of KNP by Dr. Roy Bengis and presented with generalized TB on postmortem and cultured positive for Mycobacterium bovis (M. bovis). Earlier suspect cases (before 1990) were also found during routine carcass examinations during culling operations but no definitive culture diagnosis was made. The disease probably entered the KNP during the 1950s when there were no fences between the southern boundary of the park and cattle farms. Buffalo had direct contact with BTB-infected cattle in the neighbouring farming areas. The disease has become endemic in the KNP ecosystem with the African buffalo becoming a true maintenance host. With the contamination of the environment by this maintenance host, a number of “spill-over” infections have occurred in other species, notably kudu, lion, cheetah, leopard, spotted hyaena, genet, baboon and warthog.
Since 1990 a number of surveys have been conducted throughout the KNP, the most recent (during 2000) using an antemortem test during non-lethal random sampling of all herds north of the Olifants River. The disease has spread progressively north with the highest incidence currently in herds south of the Sabie River, medium to high prevalence in the areas between the Sabie and Letaba rivers, medium to low incidence in the herds between the Letaba and Shingwedzi Rivers, and no or very low incidence in the herds north of the Shingwedzi river.
Various strategies have been proposed to control and even eradicate the disease, but none have been implemented due to the lack of consensus on any one strategy between biologists, park veterinarians, state veterinarians and the management of the SAN Parks.
Currently there is a multifaceted approach to deal with the BTB problem within KNP, this in the absence of a single strategic plan:
1. A disease-free buffalo breeding project to breed buffalo calves free of both endemic and exotic diseases and translocate these to other National Parks outside the BTB and Foot & Mouth controlled areas of the greater KNP area.
2. Continuous biannual monitoring of the buffalo herds north of the Letaba river using a non-lethal sampling method to track the spread of the disease and try and reduce the incidence in the low-prevalence herds by removing positive reactors.
3. Continued research on the infectious process of BTB in buffalo. An infectious model was completed in 2000/2001 and a longitudinal study of BTB in the buffalo population in the central Kruger National Park is ongoing.
4. Ongoing vaccination studies using BCG vaccine, the first phase of the controlled experiment was concluded in 2001 and the free-range experiment will take place in 2002 and 2003 and it is ultimately hoped that the vaccine could help control the disease.
5. Liaison with other research projects dealing with similar problems.
Considerable effort has gone into debating and monitoring the BTB situation, but, to date, there has not been a single accepted practical solution on how to control and eradicate the disease within the KNP ecosystem. The understanding of BTB in buffalo and other wildlife species is improving but a final practical control method may still be years away. This implies that BTB may have to be accepted as part of an evolving ecosystem confined by modern boundaries.