Cuterebra (rabbit or rodent botfly) is an opportunistic parasite found under the skin of small mammals. Pets can contract this infection in its 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, is clearly visible. If only one or two warbles are present, simple removal and wound care are all that is needed. However, with a mass infestation of Cuterebra, treatment becomes more complex, as the infection can move into sensitive organ tissue.
Symptoms of Cuterebra in Pets
Good news. Cuterebra is rare and is typically found on a pet's skin in very small numbers, most often just one. In fact, some veterinarians report seeing fewer than 10 cases in their office each year.
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, while petting your dog or cat. When the larva reaches its adult stage, it forms a small "breathing hole" in the skin. At this point, you may see a maggot-like worm peeking out from within the hole. The infection is short-lived, as the worm 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 to watch the cyst for infection. If you notice any of these symptom stages in your pet, notify your vet before trying to perform an at-home treatment.
Causes of Cuterebra
Watch for Cuterebra during late summer and early fall, particularly if you live in a rural setting with nesting rabbits and rodents. The female botfly lays her egg around this time, preferring rodent burrows—a curious distraction for cats and dogs. Since the larva needs a host to complete their lifecycle, a 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.
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 the host animal. 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 and give your pet an antibiotic to 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 and chewing off any bandages. A follow-up visit may be required to assure full healing.
Though rare, a mass infestation of botfly larvae may warrant a full clipping of your pet, a de-worming, and a medicated cleaning. Some animals with warble infestation (and infection) will spike a fever and need to be watched carefully following 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.
How to Prevent Cuterebra in Pets
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 helps them avoid areas where they might contract an infection. You can also locate potential rodent dens in and around your yard and try humane ways of relocating them like placing a glaring light or playing music near their hole. 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.
And while they pose no threat to people or animals, keep an eye out for the adult botfly as summer comes to an end. It has a very distinct look, and because of its large size, it's hard to miss.