This little guy (Ornage, is his name) is a rescued stray kitten that came to us with what appeared to be an abscess on his right shoulder.
When the area was cleaned and clipped we found the distinct deep hole of a cuterebra larvae’s home.
A Cuterebra is an opportunistic parasite, a large fly whose larvae (small worms) infest the skin of rodents, squirrels, rabbits, dogs and cats. The adult fly is seldom seen. They are large and do not feed on or bite animals. These flies also go by the name of a Bot Fly.
The female deposits eggs around animal burrow and on plants, rocks and other objects. The eggs stick on an animal host as the host passes by, and then the eggs hatch in response to the body heat of the animal. After hatching, the larva migrates through the nose, mouth or skin wound and burrow under the skin.
The larvae make a small hole in the skin to breathe. This is when the parasite is usually discovered; a noticeable lump in the skin with a small hole. The tip of the larvae will often be visible deep in the hole.
Cuterebra larva can grow up to 1 inch long and ½ inch in diameter. After about a month, the mature larva emerges from the cyst and burrows into the soil to pupate. After a variable pupation period, the adult fly emerges.
After a thorough examination of the hole on Ornage’s shoulder Dr. Bos found that the larvae had already exited. This usually occurs 30 days after entering the host. It will then pupate on the ground and become and adult fly.
What to Watch For
- Lump or mass under the skin often found on the head or neck
- Open area in center of lesion
Diagnosis of cuterebra larva is based on physical exam findings and visualization of the larva.
Removal of the cuterebra larva can sometimes result in serious side effects. For this reason, removal by a veterinarian is strongly recommended. The larva must be removed in one piece. If the larval body is ruptured during the extraction process, the cat may develop serious complications such as severe allergic reactions or anaphylaxis. For this reason, the breathing hole is typically enlarged by using surgical scissors or a scalpel blade. After the hole is enlarged, the larva is safely removed with a forceps or hemostat, and the area is flushed and cleaned with disinfectant. Antibiotics may be prescribed.
Home Care and Prevention
Home removal of cuterebra larva is not recommended due to the potential for serious reactions. After removal, the wound should be kept clean and allowed to heal.
The best way to prevent cuterebra larval migration is to limit access to rabbit and wild rodent nests or burrows by keeping your cat indoors. If this is not possible, frequent checks of your cat’s skin may help remove cuterebra larva early in their development.