Diseases shared by animals and humans
Zoonosis is not a word that springs readily into the average person's mind, but one that is increasingly being discussed by wildlife vets and ecologists. A zoonosis is a disease that is shared by humans and animals but is usually more common in animals; an anthropozoonosis is a disease that humans can give to animals. The SARS virus which crossed from poultry to humans is an example of a zoonosis that the entire world has become familiar with.
The World Health Organisation has estimated that about 75 percent of the new diseases that have affected humans over the last 10 years have come from animals or animal products. Anthropozoonoses are of special concern to people who work with great apes, especially chimpanzees. Diseases like measles and polio readily spread to primates, and can cause huge fatalities.
Countries involved in great ape conservation have considered a programme that evaluates the health of any person that is due to work with the primates so as to prevent humans transmitting fatal diseases to these endangered animals. With the new conservation concept of integrating conservation areas with human settlements and also the concept of transfrontier parks, veterinarians are increasingly worried about how diseases will cross the wildlife/livestock interface.
One disease of special concern is bovine tuberculosis (BTB). This disease is found in the majority of buffalo herds in the Kruger National Park (KNP), and as the fences come down with the neighbouring Limpopo National Park, the disease is likely to spread into Mozambique. The bacterium that causes BTB can infect cattle (the species that introduced BTB to buffalo originally).
This has implications for meat exports, but also for human health. People infected with HIV/Aids or in poor physical condition are more likely to catch ordinary tuberculosis. They can also contract the bovine form if they drink unpasteurised milk, or have close contact with infected cattle. It has been estimated that there are about 20,000 people living in the LNP currently, and they have cattle, goats, sheep, pigs, dogs and cats.
Several diseases have been identified for further monitoring including brucellosis, foot and mouth disease, corridor disease, canine distemper, rabies and African swine fever. Brucellosis is also caused by a bacterium, and causes economic losses to livestock owners. To remove brucellosis from a herd of animals infected individuals must be removed - it cannot be treated reliably with drugs in livestock.
Humans infected with the disease get fever, chills, sweats, weakness, pains and aches which last three to six months. Humans can be treated with antibiotics in the acute stage. Foot and mouth disease is a viral disease that is spread by inhaling or eating something contaminated with the virus. Livestock located next to foot and mouth infected wildlife can be vaccinated against the disease, but usually cannot then be exported.
Rabies can be spread between carnivorous animals and dogs, which can then pose a threat to humans. Rabies is also a viral disease and is usually spread through a bite. Canine distemper is a highly contagious viral disease that is fatal if left untreated. It affects domestic dogs, but in the Serengeti where the Masai people's dogs come into contact with wildlife a strain of the disease has also been fatal to wild dogs, jackals, lions, leopards and hyenas.
Corridor disease or East Coast fever is a protozoan disease transmitted by tick bites. Fatalities are common, but dipping animals to remove ticks can decrease the incidence of the disease. In order to address the issue of animal and human health, a Memorandum of Understanding has been signed by South African National Parks, the Peace Parks Foundation and the University of Pretoria's Onderstepoort Veterinary Institute.
The Hans Hoheisen research facility near Orpen Gate in Kruger, now the International Centre of Excellence in Biodiversity Research and Information, will spend the next five years promoting research into veterinary matters including zoonoses. Another networking initiative arose from the World Parks Congress in Durban 2003.
AHEAD - Animal Health for the Environmen and Development - have formed a special working group for the Great Limpopo Transfrontier area. The group, which contains role players from many wildlife and social fields, has had five working group meetings with a sixth scheduled for August or September. The group has facilitated about US$350,000 over several years for addressing disease issues and related training in and around the Limpopo National Park.