Cuterebra Infestations in Dogs

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Your dog may become exposed to many parasites in her environment with the onset of warmer weather. One of those parasites is the larva of the Cuterebra fly that may cause a wound or sore on your dog's skin. Your dog is most likely to be affected by Cuterebra in the summer and fall, the most active egg-laying time for the adult fly.

What Is Cuterebra?

The Cuterebra fly is a large non-biting fly that looks like a bee and lays its eggs on rocks or vegetation located near the openings of rabbit or rodent burrows. Some reports have suggested that eggs can be found in garden mulch that has been obtained near such areas. The rabbit or wild rodent are the fly's normal hosts, and they can pick up these eggs on their coats and ingest them during grooming. Dogs may be exposed in the same manner: by contacting the eggs as they pass near rabbit or rodent burrows in their environment. Eggs hatch once they are exposed to the warm body temperatures of their new dog host. Then, the newly-hatched larvae invade the host body, often through the mouth, nasal passages, or an external wound.

The larva migrates to an area under the skin of the pet, typically on the head, neck, or trunk. A cyst or thick capsule is created under the dog's skin as the larva grows. A circular breathing hole may appear as an open wound with matted hair. There is often fluid drainage from the opening and the dog may lick or scratch the area excessively.

Signs of Cuterebra in Dogs

Most dogs with Cuterebra will present to their veterinarian for an open wound or draining sore. If the dog has long fur, the owner may notice an area of matted hair that appears to irritate the pet, causing excessive grooming at the site. Occasionally, the area may appear as a lump or swelling which is also referred to as a warble (the other common name for a Cuterebra cyst). Owners may actually observe the caterpillar-like larva sticking it's head out from the open hole periodically to breathe, much like a swimmer coming up for air.

Treatment of Cuterebra in Dogs

Treatment for cuterebriasis should be performed by your veterinarian. It is important not to squeeze the swelling or cyst because it may damage the larva and release harmful chemicals into your dog's circulation. If the larva is ruptured during removal, it can cause serious complications including allergic reactions and anaphylaxis. Your veterinarian may administer local anesthesia at the site of the cyst or capsule and enlarge the breathing hole so the larva can be removed in one piece. Your dog can experience repeated and chronic infections if any part of the larva is left behind. Even with complete and appropriate removal, healing may be slower than expected because the tissue in that area is quite traumatized.

Prevention of Cuterebra Infestation in Dogs

Limit your dog's exposure to areas around rabbit and wild rodent nests or burrows to avoid Cuterebra infection. Check your dog's coat and brush her regularly in an effort to remove eggs or larvae early in their development.

How Do I Know if Cuterebra Flies Are Found Where I Live?

If you live in the United States, you can be certain that some type of Cuterebra fly lives nearby. Cuterebra flies, also known as New World skin bot flies, are found throughout North and South America. There are over 72 different species of these flies that each target a specific host animal such as rabbits or deer.

Can I Catch Cuterebriasis from My Dog?

Humans can be infested with Cuterebra larvae but not directly from their dogs. You may become exposed to the larvae in the same manner as your pet: by contacting soil or mulch that is found near rabbit or rodent burrows. Wounds created by larvae under the skin do occur rarely in people, and these follow the same path as infestations in dogs. They are considered "accidental" infestations because they are caused by Cuterebra that target wild animals for their hosts. There is one specific Cuterebra fly that does target humans specifically, but it is only found in South America.

 
Photos of Cuterbra infection and Cuterbra Larva ©GunDogDoc.com

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