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Opportunistic Parasites - What is a Cuterebra Parasite?

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First instar larva of Cuterebra, a genus of botfly. Credit: CDC/ Dr. George Healy

First instar larva of Cuterebra, a genus of botfly.

Credit: CDC/ Dr. George Healy
Question: Opportunistic Parasites - What is a Cuterebra Parasite?
A Cuterebra parasite is an opportunistic parasite found under the skin of small mammals. This parasite is the larval stage of the Cuterebra fly, who uses animal hosts to complete its life cycle. Learn more about this parasite, most commonly seen in summer and fall, in this FAQ.
Answer: Cuterebra fly species are also known as botflies, and they are opportunistic in that they use the small mammals (dogs, cats, rabbits, squirrels, etc.) to complete their life cycle.

The adult files are large and do not feed on or bite animals. Eggs are deposited around animal burrows and on plants, rocks and other objects. The eggs stick on the animal host as the host passes by, and then the eggs hatch in response to the body heat of the animal. The hatched larvae enter the body through the mouth or nose during grooming, or less commonly, through an open wound in the animal.

The larvae then migrate to specific areas on the body 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 larve will often be visible deep in the hole. Roughly 30 days later, the parasite exits the animal host, pupates on the ground, and becomes an adult fly.

It is very important to NOT squeeze the skin in hopes of getting the larva out. This can cause the larva to break apart, and cause the host animal to have a chronic infection or perhaps an anaphylactic reaction.

If you suspect your pet has a Cuterebra parasite, please contact your veterinarian as soon as possible for proper removal and treatment of any secondary infections.

Related Reading:
For more information and photos of this parasite, please see the following sites:

Cuterebra Infestation in Small Animals: Introduction
Online Merck Veterinary Manual
Photos of adult fly and pupa
From University of Minnesota
Protect your pet against Fly Strike (Myiasis)
From University of Minnesota

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