A research by University of California, Santa Barbara, states that decline in wildlife increases risk of diseases.
According to the research team led by Hillary Young, assistant professor in UC Santa Barbara's Department of Ecology, Evolution and Marine Biology, large wildlife decline is directly related to increased risk of human diseases through changes in rodent populations.
For the research, the team studied the East African savanna ecosystem. They analyzed the relationship between the loss of large wildlife, 'defaunation,' and the risk of human diseases. The group examined Bartonellosis, a set of bacterial pathogens that can lead to endocarditis, spleen and liver damage and memory loss.
"We were able to demonstrate that declines in large wildlife can cause an increase in the risk for diseases that are spread between animals and humans," said Young in a press release. "This spike in disease risk results from explosions in the number of rodents that benefit from the removal of the larger animals."
Young and her team used powerful electric fences to keep large species like elephants, giraffe and zebra away from study areas in Kenya. Inside these plots, rodents doubled in number. They explained that more rodents meant more fleas, and genetic screens of these fleas showed that they carried significantly higher numbers of disease-causing pathogens.
Young stated that rodents are the reason for increases in disease risk. This could worsen the health problems in parts of Africa where deteriorating wildlife populations are common.
"This same effect, however, can occur almost anywhere there are large wildlife declines," Young said. "This phenomena that we call rodentation -- the proliferation of rodents triggered by large wildlife loss -- has been observed in sites around the world."
"The result is that we expect that the loss of large animals may lead to a general increase in human risk of rodent borne disease in a wide range of landscapes," Young said.
"In this study, we show the causal relationship between disturbance and disease is alarmingly straightforward," she added. "We knock out the large members of ecosystems, and the small species, which generally interact more closely with humans, dramatically increase in number, ultimately brewing up more disease among their ranks.
The study gives ecosystem managers more reason to protect large and at-risk wildlife species. According to Young , even large animals like the elephants are an important part of the biodiversity and play a role in stopping the spread of diseases.
The findings appear today in the Proceedings of the National Academy of Sciences Early Online Edition.
