Red foxes used to be a common animal in North America, especially in the Northeastern U.S. But coyotes have largely killed and chased them away. The unexpected result of this ecological shift: Lyme disease is increasing dramatically.
The red fox feeds on small mammals, such as white-footed mice, short-tailed shrews and Eastern chipmunks, all of which transmit Lyme disease bacteria to ticks. Although scientists had once blamed a burgeoning deer population for the spread of ticks that carry Lyme disease, researchers at the University of California, Santa Cruz, now believe the decline of the red fox is largely responsible.
“A new top predator has entered the northeast and has strong impact on the ecosystem,” says researcher Taal Levi. “Foxes often don’t build dens when coyotes are around. (Our study) found that where there once was an abundance of red foxes there is now an abundance of coyotes.”
The loss of red foxes means an increase in the abundance of the smaller animals that serve as hosts for bacteria-carrying ticks. Red foxes may have once kept those populations under control.
Ticks pick up the Lyme disease bacteria when they bite infected mice and later infect other animals including humans. Levi says tick nymphs, about the size of a sesame seed, carry the bacteria and are so small that many people who contract Lyme disease never know they’ve been bitten.
Lyme disease can be treated with antibiotics if discovered early but if the disease persists, it can cause serious muscle and joint pain.