A report in Scientific American indicates that the decline of the red fox population over the past few years coincides with a rise in cases of Lyme disease.
More ticks = More cases of Lyme disease
Data from five states shows that the loss of the red foxes along with an increase in the population of rodents has resulted in an increase in cases of Lyme disease.
As coyotes have taken over their ranges in North America, the red fox populations are plummeting, and researchers have found one surprising result: The drop is fueling the spread of Lyme disease.
Lyme disease cases have increased enormously in recent years: From 1997 to 2007, the number of cases increased by 380 percent in Minnesota, 280 percent in Wisconsin and 1,300 percent in Virginia. Researchers used to think the increases were due to increasing deer populations, since deer are an important host to the disease-causing bacteria. However, the new data show these increases were independent of deer population levels.
Where there once was an abundance of red foxes, there is now an abundance of coyotes, according to researchers at the University of California in Santa Cruz.
Lyme disease, which affects horses, humans and other animals, is caused by a bacteria spread by ticks. The ticks pick up the bacteria from infected mice or deer, and if they bite a human, we can get the disease too. If caught early, it can be treated with antibiotics to kill the bacteria.
Lyme disease progresses in three stages: The first causes itching, chills, fever and headache for the first few weeks; second, an infected person starts having muscle pain and joint aches; third, these muscle and joint issues can continue for years after the initial infection, causing abnormal movement, weakness and speech problems.
Data from five states was used to make mathematical models of the disease's spread. In their models, the researchers saw that the loss of the red foxes would result in an increase in Lyme disease, even with deer populations remaining steady.
The red fox feeds on small mammals such as mice, shrews and chipmunks, animals that, like deer, can play host to the Lyme-disease-carrying ticks. As the red fox population declines, as it has been for the past 30 years, researchers have seen increases in the populations of these small mammals.
The foxes have been outcompeted by growing populations of coyotes in the regions, which are becoming the top predators in areas where mountain lions and wolves have gone extinct. The coyotes are more dangerous to the foxes, lowering their numbers, the researchers said.
According to the research, as the number of foxes has decreased, the population of small rodents has increased and with them there has been an increase in the population of Lyme-disease-carrying ticks which attach themselves to horses and people, infecting them with the disease.