Pesticide used to treat ear mite infections in Catalina Island foxes

DAVIS, Calif., Dec. 7 (UPI) -- Catalina Island foxes are a subspecies fox trapped on the California island for which they are named. Roughly half suffer from ear tumors. About a third of those tumors are malignant.

In two new studies -- both published in the journal PLOS ONE -- by scientists at the University of California, Davis found a link between the tumors and ear mite infections. Researchers also identified a potential treatment for the two ailments.

"We established a high prevalence of both tumors and ear mites, and hypothesized that there was something we could potentially do about it, which now appears to be significantly helping this population," lead study author Winston Vickers, an associate veterinarian with the UC Davis Wildlife Health Center at the UC Davis School of Veterinary Medicine, said in a press release.

After six months of treatment with an acaricide, a pesticide used to kill mites and ticks in dogs and cats, mite infection rates dropped from 88 percent. Inflammation and the prevalence of ear tumors also declined.

Wildlife managers have upped the use of acaricide treatments in island fox populations in recent years, and have seen mite infections slowly decline.

"Prior to treatment in 2009, approximately 90 percent of all pups handled had ear mites, whereas by 2015, mites were detected in only 15 percent of new pups," said study co-author Julie King, the conservancy's director of conservation and wildlife management.

But researchers say it's not yet clear how much of a dent the pesticide treatments will put in the long-term prevalence of ear tumors. Other fox subspecies relegated to the neighboring Channel Islands have similar ear mite problems but don't develop ear tumors -- which suggests Catalina foxes are genetically predisposed to tumors.

"Catalina foxes have an over-exuberant tissue reaction to the same stimuli -- the mites -- and that appears to lead to the tumors," Vickers said. "That's why we gravitate toward genetics in addition to other factors."