In the Middle Ages, fleas carried by rats were responsible for spreading the Black Plague. Today in East Africa, they remain important vectors of plague and many other diseases, including Bartonellosis, a potentially dangerous human pathogen.
Research by Hillary Young, assistant professor in UC Santa Barbara's Department of Ecology, Evolution and Marine Biology, directly links large wildlife decline to an increased risk of human disease via changes in rodent populations. The findings appear today in the Proceedings of the National Academy of Sciences Early Online Edition.
With an East African savanna ecosystem as their research site, Young and her colleagues examined the relationship between the loss of large wildlife defaunation and the risk of human disease. In this case, they analyzed Bartonellosis, a group of bacterial pathogens which can cause 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. "This spike in disease risk results from explosions in the number of rodents that benefit from the removal of the larger animals."
The researchers discovered this effect by using powerful electric fences to experimentally exclude large species like elephants, giraffe and zebra from study plots in Kenya. Inside these plots, rodents doubled in number. More rodents meant more fleas, and genetic screens of these fleas revealed that they carried significantly numbers of disease-causing pathogens.
The study was concentrated in an area where rodent-borne disease is common and sometimes fatal. According to Young, these rodent outbreaks and associated increases in disease risk may be exacerbating health problems in parts of Africa where diminishing wildlife populations are rife.
"This same effect, however, can occur almost anywhere there are la
|Contact: Julie Cohen|
University of California - Santa Barbara