Flies and their larvae (maggots) can cause several disorders in rabbits including Myiasis and Fly Strike. However, warbles is caused by a specific fly species and its larvae-the Cuterebra. Quite different from normal house flies, the Cuterebra only lay a single egg underneath the skin which takes up residence in the rabbit and begins its life cycle.
This pocket where the larva lives will have a small air hole that the larva uses to breathe. This lump under the skin is commonly found on the neck area but can be found anywhere on the rabbit's body. The larvae will grow and the breathing hole becomes larger giving the larva enough room to emerge and fall out. The larva eventually grows into an adult fly where it can again reproduce on the next unsuspecting victim.
Flies can invade a rabbit's skin from open wounds and will search out places that are unclean. Outdoor rabbits are particularly susceptible to invading flies and their larvae. Moist areas are also searched out by flies which include the rectal area of a rabbit.
Rabbit owners who suspect their rabbit has been invaded by the Cuterebra fly larvae should not try to remove the larva. The sac in which the larva is confined is filled with deadly toxins that if ruptured, can transfer into the rabbit's system leading to severe illness and even death. The warble will need to be removed by an experienced veterinarian who may anesthetize the rabbit before the procedure.
The area may appear to have a layer of crust which when cleaned away, the hole becomes quite visible. The skin is cut above the sac and the larva becomes visible and is removed. If the warble wasn't removed fully intact, antibiotics may need prescribed. Owners will also need to familiarize themselves with the types of antibiotics that are unsafe for rabbits.
Prevention is important in keeping rabbits safe from pests and parasites. A rabbit's cage and environment should be cleaned thoroughly on a regular basis. During grooming sessions, check your rabbit for any wounds or unclean areas that may invite flies to lay their eggs. The rectal area may need trimmed from fur especially if the rabbit is overweight and cannot self-groom properly.
Any time an owner notices a lump underneath their rabbit's skin, a veterinarian should be consulted as soon as possible. If left untreated, these open wounds caused by the maggots or larvae can lead to infections and possibly the death of the rabbit.
THE RABBIT HANDBOOK, by Karen Gendron, copyright 2000.
RABBITS FOR DUMMIES, by Audrey Pavia, copyright 2003.