South African disease outbreak affects its mammal population

11/06/09 - One of the major issues facing South Africa's mammal population is the prevalence of diseases, according to Professor Wouter van Hoven, who spoke yesterday afternoon in the University of Rhode Island's Center for Biological Life Sciences.The director of the University of Pretoria's Center for Wildlife Management, van Hoven, presented a lecture addressing various diseases that have infected the wildlife of South Africa.

With a background in wildlife nutrition, van Hoven oversees graduate students working with various wild animals in South Africa's Kruger National Park. He said that sick animals are commonly seen in KNP and new diseases are still being found today.

"If you start digging in the guts of African wildlife, you find new diseases," van Hoven said.

While studying a rhino, he found Triplumaria corrugata, a new species of gastro-intestinal protozoan, an organism that causes disease.

Because wildlife and domestic animals are so incorporated into the lives of South Africans, diseases among animals are historically distributed in areas where people settled, van Hoven said.

He classified diseases commonly found in the wildlife in KNP into several categories, such as Transboundary Animal Diseases (TADs) and endemic diseases. TADs include Foot and Mouth disease, Theilerioses, Trypanosomosis and Tuberculosis (of animals, not humans). Anthrax was one of the major endemic diseases van Hoven discussed.

In regards to endemic cycles, van Hoven said that buffalo are the only permanently infected reservoir species of wildlife. He said that carrier buffalo shed little disease and that in young buffalo, high levels of antibodies provide extra protection against endemic diseases; however, by 6 months old, they become susceptible.

Diseases do not always visibly present themselves in the wildlife found in KNP, but species known as "sentinel," or indicator species, such as the impala, can be observed to detect for the presence of an endemic disease. Along with his researchers, van Hoven monitors endemics by observing impalas in the national park.

Foot and Mouth disease, for example, is a clinical disease van Hoven has come across in numerous impalas in KNP. Common visible symptoms include an abnormally arched back, the shifting of weight from one foot to the other and shaking hooves.

He said that shared resources, like water, spread diseases such as Foot and Mouth.

"Eighty-three percent of outbreaks of diseases in impalas occur during the dry season, from May to November," van Hoven said.

Another disease infecting the wildlife of KNP is Anthrax. This highly contagious bacterial disease is indigenous of wildlife in KNP and is affecting the region's domestic and wild animals. Animals infected with the anthrax bacteria, Bacillus anthracis, often die suddenly without presenting any symptoms, van Hoven said.

Animals that die from anthrax pose a danger to other wildlife and the national park itself. Resistant spores are released into the air and soil when an anthrax-infested carcass is opened, van Hoven said. He also said that these spores can remain in the soil for numerous years, therefore threatening to infect other living organisms.

He said that cycles of infection transfer from organism to organism in such cases. For example, when an animal dies from anthrax, blowflies gorge themselves on the carcass's bodily fluids and remnants before landing on nearby leaves where they defecate and re-gorge their meals, van Hoven said.

Although anthrax is very deadly, van Hoven said predators, such as lions, are less susceptible to it.

"If they're young, their heads swell, but they become immune to the anthrax bacteria after one to two infections," van Hoven said.

To control the spread of anthrax among the KNP's wildlife, van Hoven and his students take turns patrolling the park and report any sightings of dead animals. Any carcasses found to be infected are buried or burned.

Another prominent disease being observed in KNP's wildlife is Tuberculosis, caused by Mycobacterium Bovis. This strain of TB is different than that found in humans and is considered an exotic disease that causes a serious infection. It has affected kudu, baboons, lions, hyenas, leopards and buffalo in the park.

According to van Hoven, TB was first discovered in the Southern boundary of KNP in 1990 when a 2-year-old buffalo was identified as an infected animal. Since 1995, van Hoven has identified more than 200 positive cases of wildlife infected by this strain of TB.

Not only is it difficult to manage the spread of TB, but the disease is rapidly infecting the entire buffalo population in the park, van Hoven said.

"It's widespread throughout the park's buffalo population today," van Hoven said. "We decided against killing buffalo suspected of having TB because then we'd be killing all of them."

Junior biology major, Jessica Panciera, said that she found van Hoven's lecture very interesting and was surprised at the prevalence of TB among the buffalo population.

The last disease that van Hoven presented in his lecture was called Crocodile Pansteatitis. This disease was not discovered until van Hoven and his team began to investigate the cause of death of numerous crocodiles.

Last year, the bodies of 180 crocodiles were discovered in South Africa's Olifants River. The deaths were first attributed to the building of the Massinger dam, a structure built in the river. However, upon further inspection, Crocodile Pansteatitis was discovered.

Using a helicopter, the dead crocodiles were lifted off the ground and brought to a location where they were incinerated after blood samples were taken to confirm the presence of the virus.