Kit Fox Distemper Outbreak: How did the Deadly Disease Reach the Desert?

Camera Trap captures kit foxes near a den entrance | Courtesy California Energy Commission

A desert kit fox population suffering an outbreak of distemper near the Genesis Solar Energy Project was exposed to coyote urine in an attempt to repel the foxes from the site, according to documents released by the California Energy Commission. The deadly, highly contagious disease affects dozens of animal species, including coyotes. The virus is mainly spread through contact with infected bodily fluids, urine among them.

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Seven desert kit foxes have died of distemper since November near the project, located 25 miles west of Blythe and just north of Ford Dry Lake. Construction on the project has been suspended as the state Department of Fish and Game (DFG) investigates the outbreak. This is the first known occurrence of the disease in the desert population of kit foxes.

DFG veterinarian Deana Clifford has been leading the scientific investigation of the outbreak. She says that DFG has not so far considered coyote urine as a possible vector for the virus when I brought it up to her. "It actually hadn't occurred to us," she told me Monday. The hypothesis leading the speculation in the press and online is that a traveler may have walked an infected dog at the Wileys Well Rest Area, eight miles southeast of the project site on Interstate 10. Clifford points out, however, that another wildlife species is just as likely a "Patient Zero." "The virus can infect a wide variety of hosts," she said, "some of whom are native to the area. It does cycle through populations of wild animals. A badger could very well have brought the virus to the area."

Developing the Genesis Solar Energy Project requires that several populations of desert kit foxes (Vulpes macrotis) be removed from the project's footprint. Not legally considered as endangered or threatened, the foxes - the smallest member of the dog family in North America - serve as a keystone species due to their position near the top of the food chain. According to Monthly Compliance Documents filed with the California Energy Commission, biologists working with Genesis Solar attempted to "haze" kit foxes away from "Den 8," one of several labyrinthine dens on the project site, by using coyote urine to repel the kit foxes. Coyotes are the foxes' main predator.

After a delay in implementation which the project's Designated Biologist notes was caused by "problems getting supplies" of urine, the biologists applied about 1 milliliter of coyote urine to the soil just outside an entrance to Den 8. The Designated Biologist's report for the period from May 30 to June 5 reads, in part,

Den 8 is also showing continued activity, 2 adults have been observed. Hazing, using coyote urine was tried at 2 of the 6 openings. 30 drops were placed on the ground between two openings that were spaced about 1 foot apart... [C]ameras were placed on site to gather more information. Videos obtained showed one fox walking directly over the area with no reaction. Other videos showed fox laying within 25 feet of the area, showing no signs of stress.

Coyote urine is commonly used as a "natural" animal repellent. Collected from captive coyotes kept in pens, the urine is concentrated and bottled. A handful of wholesalers make up the industry, and they are rather reluctant to disclose, or even discuss, the facilities that provide their product. Once infected with distemper, animals can shed the distemper virus in their bodily fluids for two weeks or so before they become severely ill, raising the possibility that seemingly healthy coyotes might introduce the virus into collected urine supplies.

Coyote urine is regulated as a pesticide in the U.S. By law, coyote urine sellers are required to register their product with EPA and list the active ingredients. So-called "inactive ingredients" need not be listed and are generally considered trade secrets. Typically, the active ingredient in coyote urine is coyote urine, with liquid formulations reaching up to 97% or so. Whether the additional few percent is a preservative or some other material that might serve to kill the distemper virus is unknown, but it seems unlikely.

Inhalation of the virus is the primary means by which animals contract canine distemper. If an animal susceptible to distemper sniffs at a bit of infected urine while the virus is still viable - as with droplets of coyote urine on soil investigated by curious kit foxes - the virus enters the animal through the nasal tissues.

Little is known about the progression of distemper in desert kit foxes, though the few observed by DFG seem to progress through the final stages rapidly. In dogs, symptoms begin in earnest from two to three weeks after infection. Victims can suffer upper respiratory infections and pneumonia, fever and encephalitis, anorexia, and immune suppression.

Deceased desert kit fox on the Genesis Solar site | Photo courtesy California Energy Commission

I found no other mention of hazing with coyote urine in the compliance documents, given its apparent complete failure at repelling foxes. The elapsed time between that application and the first confirmed kit fox distemper deaths is far too long to offer a "smoking gun": five months rather than the three weeks it would likely take for kit foxes exposed to infected urine to become ill. There were, however, at least two kit fox mortalities near the project site in intervening months - one each in August and September - that were neither explained fully nor investigated: project biologists simply documented the mortalities and buried the foxes' remains where they were found. Though the biologists are skilled observers - their descriptions of fox cubs playing outside the dens lighten the deadeningly dull Compliance Reports - kit foxes are superbly stealthy. It seems plausible that a sick kit fox, a solitary animal except during breeding, might slink off unnoticed by human observers to die in solitude, infecting other foxes some weeks later as they scavenge its remains. The DFG's Deana Clifford says she knows of no other solar project where coyote urine has been used to haze kit foxes, adding another layer of coincidence.

Whether or not it arrived at the site in a squeeze bottle, the source of this outbreak may not be a mystery for long. Clifford has sent necropsy samples to virologists at Cornell University, who should be able to identify which strain of the virus is responsible. Identifying the strain may well provide the smoking gun, as different strains of the virus are found in different species of host animal. We may yet be able to pin this rash of kit fox mortalities on an ailing badger, or an unvaccinated rest area visitor.

Even if that's the case, however, DFG should ban the use of coyote urine to haze desert kit foxes away from their dens. Given coyote urine's murky supply chain and the consequent near impossibility of ensuring that any given sample is distemper-free, and given the apparent catastrophic toll distemper can take on desert kit fox populations, the stuff should never again be used around desert kit foxes.

Especially since it doesn't seem to work.

Chris Clarke is an environmental writer of two decades standing. Author of Walking With Zeke, he writes from Palm Springs regularly at his acclaimed blog Coyote Crossing and comments on desert issues on KCET weekly. Read his recent posts here.

About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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