How to Treat Cuterebra in Pets

This pesky parasite can invade your pet's skin

Close-Up Of A Dog While Burrowing In A Forest
Audrius Peseckis / EyeEm / Getty Images

Pets can contract cuterebra in their larval stage—often called "warbles"—when chasing and hunting small rodents and digging or sniffing near a rodent's den. Pet owners usually notice these revolting creatures as a new bump on the skin of their dog or cat. Then, upon further examination, a burrowed maggot, or worm, may be visible. The most common presentation is one or two warbles present in the skin of your pet. In this case, your vet will remove them and treat the wound. However, it is important to know that in rare or more severe cases, warbles can cause severe diseases particularly in the central nervous system (CNS) or eye area. Rare cases of severe systemic disease and illness have also been reported.

What Is Cuterebra?

Cuterebra refers to rabbit or rodent botfly, which is an opportunistic parasite that spends part of its life burrowing and growing under the skin of small mammals. Good news: Cuterebra is not common and is typically found on a pet's skin in very small numbers, and most often just as a single location. In fact, some veterinarians report seeing fewer than 10 cases in their office each year.

Cuterebra, a genus of botfly
First instar larva of Cuterebra, a genus of botfly. Fly, parasite. Image courtesy CDC/Dr. George Healy. Smith Collection / Gado / Contributor / Getty Images

Symptoms of Cuterebra in Pets

On initial infection, you may not see anything out of the ordinary residing on your pet's skin. However, as the larva matures, a small bump may be apparent and can often be felt, usually on the head or neck area. Eventually, cuterebra form a small "breathing hole" in the skin. At this point, you may see a maggot-like worm peeking out from within the hole. The worm causes local inflammation and infection and eventually exits it's host once fully mature, leaving behind an empty cyst. Sometimes the whole process goes unnoticed until this point, but still, it is important if you see a bump on your pet or suspect a cuterebra not to wait and to bring them to a vet.

Causes of Cuterebra

Watch for cuterebra during late summer and early fall, particularly if you live in areas with nesting rabbits and rodents. The female botfly lays her egg around this time, preferring rodent burrows—which are a curious distraction for cats and dogs. Since the larva needs a host to complete their lifecycle, an outdoor cat or dog that happens to be in the right place at the right time may be chosen.

The eggs of the botfly attach to an animal host as it passes by, and they hatch in response to the animal's body heat. Once hatched, larvae enter the body through the mouth or nose, during self-grooming, or through an open wound. The larvae then migrate (or warble) to specific areas on the body under the skin to complete their larval cycle. Roughly 30 days later, the parasite exits the animal host to pupate on the ground and become an adult fly.

Treatment

If you come across cuterebra on your pet, do not panic and don't remove it yourself! Squeezing the skin or using tweezers can cause the larva to break and may initiate an infection or allergic reaction in your pet. Remember, this is not an emergency situation, however, a vet visit is required for safe removal and to assure a full recovery.

At your vet's office, a professional will remove the larva properly (it can be up to 1-inch long at maturity). Your vet may flush and dress the open wound. Your vet may need to sedate your pet in some cases and they may prescribe antibiotics to help prevent a secondary infection. Often, you will be sent home with an E-collar (or head cone) to keep your pet from licking the wound which causes infections. A follow-up visit may be required to assure full healing.

Some animals with warble infestation (and infection) will spike a fever and need to be watched carefully following the extraction of the parasite. In rare cases, IV fluids and antibiotics are given until a full recovery is made. And don't wait! Animals with preexisting health conditions could die from any parasite infestation, if not treated promptly.

treating cuterebra in pets illustration
Illustration: The Spruce / Yifan Wu

How to Prevent Cuterebra

Very little can be done to prevent cuterebra from infesting your pet. However, watching your dog or cat when they are outside and not allowing them to roam free or stick their paws or faces in holes or bushy areas can be helpful. You can also locate potential rodent dens in and around your yard and prevent your dog or cat from accessing them by keeping cats indoors only or only allowing your pet access to certain parts of the yard. In the summer, it is important to check your animals each night for any inconsistencies in their skin. Aside from warbles, animals can contract ticks, as well.

While they pose no threat to people or animals, keep an eye out for the adult botfly as summer comes to an end.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.