Species Loss Increases Disease in Humans
The next time someone asks you why wildlife and biodiversity should be protected, you can tell them this: because it might save you from getting a disease. Researchers in New York say they have identified a link between the loss of biodiversity and an increase in diseases like Lyme disease, West Nile Virus and hantavirus. For reasons yet to be fully understood, they say when species are lost from habitats, and others survive, it is the survivors that spread disease more. For example, in forested areas which lose opossums, white-footed mice numbers increase and so do populations of blacklegged ticks which carry the pathogen that causes Lyme disease.
In 2009 there were 30,000 new confirmed cases of Lyme disease in the United States. It is one of the more common infection diseases in North America. Most United States cases of Lyme disease occur in the Northeast and Great Lakes regions. White-tailed deer are also hosts for the ticks that carry the disease. Removal of natural predators has allowed some prey animal populations to flourish, such as white-tailed deer. Though the study did not investigate habitats with white-tailed deer and disease-carrying ticks, its insights still apply to those areas. “We knew of specific cases in which declines in biodiversity increase the incidence of disease. But we’ve learned that the pattern is much more general: biodiversity loss tends to increase pathogen transmission across a wide range of infectious disease systems. In a similar way, the protective effect of biodiversity is clear enough that we need to implement policies to preserve it now,” said ecologist Felicia Keesing, and first author of the study. (Source: eurekaalert.org)
Deer were spreading ticks to cattle in Texas, which cause disease in them. Fortunately the disease doesn’t spread from cattle to humans, but it does cause loss of cattle, which damages the local economy. Significant interventions have been made to kill ticks on the deer, without harming the deer, and have achieved good success rates, but these after the fact measures are much more difficult to put in place. If biodiversity is protected and land managed carefully to keep all the animals in an ecosystem at least somewhat in balance, diseases in animals should be held in check naturally. One of the study’s co-authors, Andrew Dobson said, “When biological diversity declines and contact with humans increases, you have a perfect recipe for infectious disease outbreaks.”
Species around the world are being driven towards and into extinction at at high rate. With biodiversity losses and a changing climate can anyone predict what will happen on the emerging infectious diseases front?
Image Credit: National Park Service