DFW Urban Wildlife

Anyone who has spent time observing Coyotes in North Texas knows these animals are particularly susceptible to a terrible disease known as sarcoptic mange.  This condition is caused by an infestation of Sarcoptes scabiei–a microscopic burrowing mite.  The disease is characterized by hair loss, itching, and secondary infections. A severe case of mange can result in a Coyote with crusty, scaly skin, and completely denuded of fur.

An infection of this magnitude is almost always a death sentence for the afflicted animal. A Coyote with severe mange is susceptible to secondary infections caused by excessive scratching, and it is vulnerable to cold weather exposure in winter. Tough and smart Coyotes can survive for years with mange, though living with this condition is certainly very difficult and unpleasant.

Mange is highly contagious, and an infection can be easily spread among other members of a Coyote family group.  Some Coyotes seem to be more prone to the disease than others.  It’s not clear why that would be the case, but some people suspect that warfarin–the active ingredient  in many kinds of rat and mouse poison–is the catalytic agent.

Warfarin is an anticoagulant that causes rodents that consume it to bleed out and die. As the rodent is weakened by the poison it will become easy prey for any predators that share the ecosystem.

When a Coyote eats a poisoned rodent, it too becomes poisoned–not necessarily with a fatal dose–but with one that is severe enough to compromise the Coyote’s immune system. It is thought that this may be the mechanism that increases the Coyote’s vulnerability to being infected with mange.

The danger of unintended secondary poisoning is why many people advocate against the widespread use of warfarin. It’s not just Coyotes that are affected by eating warfarin poisoned prey. All predators in the ecosystem are similarly vulnerable. Coyotes, Bobcat, Raccoons, foxes, skunks, owls, hawks, and eagles can all be affected by secondary warfarin poisoning. Often poisoned prey is inadvertently fed to offspring, robbing the young animals of a successful start in life.

At any level of progression mange looks to be a totally miserable condition.  It is difficult to see a Coyote in such a state and not feel a deep empathy. It’s very common for people who have encountered an afflicted Coyote to want to help the animal in some way.  But what can be done?

As it turns out, there are a couple of approaches that can be used in an attempt to treat wild Coyotes with mange, but each comes with a significant set of challenges. These techniques should only be attempted under the close supervision of an experienced and licensed wildlife rehabber.

The conventional approach to treating mange in wild Coyotes is by delivering baits laced with ivermectin. Ivermectin is a medicine used to treat parasitic infections (worms and arthropods) in mammals. It is relatively inexpensive and generally available without a prescription anywhere livestock supplies are sold.

But ivermectin is a powerful drug. It must be dosed and administered precisely. Adverse reactions are possible, and follow up treatments are required. Too much ivermectin and you may poison the animal you are trying to help. These factors–combined with certain specific Coyotes behaviors– make it very difficult to effectively medicate wild Coyotes.

Coyotes often defend a territory as a family group, which typically include anywhere from two to five individuals. This social behavior makes it extremely challenging to target individual Coyotes in the group for treatment. Fundamental to success is being able to positively identify individual Coyotes–this is seldom trivial. Even when properly identified, medicated baits left for one Coyotes can readily be consumed by another member of the family group. And because of the danger of overdosing, this kind of haphazard drug delivery is just not practical. A great deal of serendipity is required to get the right amount of medicine to the right Coyote.

Trail cameras can be used to help confirm which Coyote has been medicated, but this is not a foolproof technique. A missed trigger may leave gaps in the photographic evidence and make it ambiguous as to which Coyote actually took the medicated bait.

To complicate matters further, a followup treatment is required a few weeks later in order to address the mite’s lifecycle. Mite eggs are not affected by ivermectin treatments, so any that hatch after the initial treatment can reinfect the host animal if a followup dose is not received.

Timing is critical–the followup dose of ivermectin must be administered after any remaining eggs have hatched, but before the new generation of mites can lay eggs of their own. Much dedication and skill–plus a good deal of luck–is required to pull this off. It is a very difficult thing to do.

Recently a new medicine has become available that has the potential to be much more practical. Bravecto is more forgiving than ivermectin when it comes to dosing. That means multiple or unintended treatments are not as much of a concern as they are with ivermectin. Bravecto is also effective long enough to kill multiple generations of the mites that cause mange, so only one treatment is require to successfully treat a Coyote for the disease. Delivering Bravecto to an infected animal is still not trivial, but it is decidedly easier than the alternative.

The main obstacle to using Bravecto is that a prescription is required. So, in order to treat an afflicted Coyote, a licensed veterinarian must be recruited to the cause. A certain professional reluctance is understandable.

Being that it is so challenging to deliver medicine to wild Coyotes, one might wonder if trapping them and treating in captivity would be a better option. Unfortunately, it is not.

Coyotes are very clever, and they are very cautious. These characteristics make Coyotes extremely difficult to capture. Even when a skilled trapper is able to coax a struggling Coyote into a live-trap, the outcome is still unlikely to be positive. Being live-trapped is very stressful for Coyotes. The captured animal may injure itself trying to escape. Or, weakened by mange, an extended period of time in a trap my prove too much for a sick Coyote.

Further, Coyotes do not do well in captivity. They require specialized enclosures and handling techniques. When kept in cages, Coyotes pace endlessly looking for a way to escape. The level of stress they endure in an enclosure is not conducive to recovering from a disease like mange. And through it all, Coyotes kept in captivity must retain a healthy fear of humans if they are ever to be released back into the wild. In short, when attempting to treat a Coyote in captivity, the cure may prove to be worse than the disease.

Helping wild Coyotes with mange is possible. I’ve seen it accomplished with some level of success. But it is a full time job. The effort requires resources, patience, luck, and dedication that few of us are able to muster. And because the disease continues to exist in the ecosystem, the likelihood a reinfection is a real possibility. This is simply not a task for the faint of heart.

Further Reading

• The treatment of sarcoptic mange in wildlife: a systematic review