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The Cuterebra in Dogs and Cats

Cuterebra is the scientific family name of the North American rabbit or rodent botfly.

Most of the general public are not aware of what a cuterebra is or have had a pet that has been lucky enough to avoid being infected by one. As an RVT of 18 years, I myself have only been a whiteness to a handful of cases until I was affected close to home. I recently rescued a kitten living outside on its own that at first glance had an infected wound on its chest. With no other wounds on his body, only a discharge from the eyes, I found it peculiar until I discussed the case with one of my veterinarians. One of his rule outs was a cuterebra infection, which became a scary reality when a cuterebra larva was removed from the open wound on my kitten’s chest.

After this experience, I decided to do further research. Dogs and cats act as accidental hosts for cuterebra larval development within their tissues.

You may be thinking, how can my pet become infected? Dogs and cats become accidentally infected when investigating rabbit or rodent burrows, where adult botflies deposit their eggs. After hatching, the larvae will enter the body through an opening, like the nose or mouth, or through a skin wound. The larvae, after several days, will migrate to the tissues where they encyst, and development is continued. As the larvae grows it becomes a noticeable swelling beneath the skin. A small breathing hole, or cyst, will be visible on the face, neck or trunk over the larvae and will enlarge when the larvae is mature and ready to leave between 3-8 weeks after entering the tissues. The cyst may cause a serious or purulent discharge that is 3-5mm in diameter.

The larvae may migrate to the brain tissue, in cats, and symptoms could include lethargy, seizures, blindness, abnormal vocalization or gait, and abnormal or no reflex responses. Violent sneezing attacks may also occur weeks before other clinical signs. The larvae may also migrate to the respiratory system tissues causing difficult breathing in cats. Occasionally no symptoms are evident until the larvae have migrated from the body and the empty cyst becomes infected or develops into an abscess.

Treatment varies with when the infection is identified. The less mature larvae can be removed by surgically opening the cysts that have formed in the skin. Mature larvae are dark, thick, and heavily spined. These can be removed with forceps from the cyst opening. The tissues are then flushed, debrided, and left to heal by granulation. In some cases, surgical closure of the tissue may be needed. If the larvae have already migrated out, the above procedure is followed, and antibiotics prescribed. Larvae that have migrated to body tissues must be surgically removed. With any of these treatments, it is highly recommended to visit your veterinarian for proper and safe removal of the larvae.

For those of you wondering if my kitten survived this infection, the answer is yes! The prognosis, of course, is worse if your pet is infected with multiple larvae or if they have migrated to a nerve, other sensitive tissues or organs. I hope sharing my experience has not frightened you but left you more empowered against these parasitic flies.

Written by: Jackie Lane, RVT

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