Answer to Case of the Week 784

Answer to the Parasite Case of the Week 784: Myiasis causing fly larva, most likely Cuterebra species. 

Thankfully, Rebecca Black and her colleagues were able to remove the larva from this poor kitty! 

As noted by Florida Fan and others, we don't have the posterior spiracles to make a definitive identification. However, based on the presentation, geographic location, dark color, and overall appearance, we can still make an identification of Cuterebra sp. third instar stage larva.

Note the dark color and small spines covering most of the body. 

If you are interested, you can read more about this infection in animals at the following excellent sites:

Cuterebra Infestation in Small Animals - Integumentary System - Merck Veterinary Manual

Companion Animal Parasite Council | Cuterebriasis

Genus Cuterebra - Rodent and Lagomorph Bot Flies - BugGuide.Net

The usual hosts of Cuterebra are rodents and lagamorphs. Flies lay eggs on vegetation or woody ground debris, often near the opening of rodent burrows. The eggs hatch to release a first instar stage larva when there is exposure to increased temperature, indicating the presence of a nearby host. The larva then enters host through any natural body opening such as the mouth or existing wounds. It will then migrate to the subcutaneous tissues and enlarges rapidly. It creates a pore from which it can breathe and eventually exit the host, usually in 3-6 weeks. 

As you all know, my interest is in human infections, and therefore I posted this case as both a pet lover and a human medical parasitologist. Cuterebra infections (cuterebriasis) can rarely occur in humans, and as with other forms of myiasis, removal of the larva is curative.

Thanks again to student veterinarian, Rebecca Black, for donating this case!