The Cuterebra Parasite

The ‘Other’ bug under the skin. In the summer months, we all worry about mosquitoes and black flies. Our dogs and cats have to worry about these insects as well as fleas and ticks. Recently we have been seeing a not-too-common parasite that gets under the skin of dogs and cats and can cause some big lumps. This parasite is called a Cuterebra and there is nothing cute about it. The cuterebra is the larval (baby) form of a fly called a Bot Fly. This fly lays eggs around the rabbit and small rodent burrows and if our dogs and cats go digging for these animals, the eggs stick to their skin. Once on the skin, the eggs hatch and burrow under the skin where they start to grow. When they reach a certain stage they need to breathe air so a hole is created in the skin and you can actually see the larva breathing under the pet’s skin.

As the larva gets bigger, the lump under the animal’s skin gets bigger as does the hole. When the larva has reached full size (about 2.5 cm) it falls out of the hole and completes its life cycle eventually forming a new Bot fly.

We see pets with these breathing holes and can remove the growing larva before it causes problems for the pets. These larvae are not contagious to other dogs or humans but are just ugly.

If you find your dog or cat has a new lump, it is best to get it checked and if there is a cuterebra larva inside, it can be removed before it causes many problems.

Written by: Dr. David Kerr, DVM