Fly-Strike Emergency

Jul 10, 2011 by

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WARNING: This article is not for the faint of heart or weak of stomach. This article is for the good of rabbits everywhere since fly strike happens both indoors and outdoors.

Fly strike can happen anywhere and anytime when the weather is warm enough to hatch fly eggs. Even the cleanest household can have a fly slip in when someone comes through the door. If that household also happens to have a rabbit with an open cut, a newly removed tooth, a messy bottom, or food gunked to him, he can become a victim of the ordinary house fly or other fly species. The more restricted a rabbit is in movement, the more likely he is to be a target.

Flies don’t need to lay eggs on the messy or injured area; that is merely what attracts them. The eggs look like tiny patches of off-white mush laid on the regular fur where they can stick. When the eggs hatch, the maggots automatically gravitate to the appropriate area where they begin to burrow in and, literally, eat their victim alive. The tiniest cut can provide access beneath the skin where they begin to burrow and eat deeper and deeper. If not found and flushed out before getting too deep, there may be no hope. Between tissue damage and infection, they cause serious harm to their victim and are potentially life threatening.

Inspect your rabbit thoroughly and regularly. If egg patches are found, a flea comb can help remove them. Vinegar also helps kill the eggs, but do not rely totally on this. Removal is the key.

The maggots themselves are tiny white worms (the larval stage of the fly) and there can be hundreds of them. You may have seen such wiggling masses on garbage. If you see them on the surface of your rabbit, be assured they are also under the surface. You can frequently tell where they are by a rippling motion under the skin.

Every single maggot must be removed and killed or it will burrow back inside at the first opportunity. Watch carefully for the smallest sign of movement anywhere on the animal’s fur or near the area of the maggots’ entrance. The rabbit should also be thoroughly checked for additional patches of eggs that may not have yet hatched. Be sure to follow all of this with an immediate trip to your veterinarian. A thorough veterinary exam, possibly more flushing, and antibiotics will be needed any time maggots have been found on your pet.

Cuterebra

Bot flies are not usually found indoors so a rabbit getting exercise outside is more susceptible than one kept strictly indoors. However, do not discount the possibility of one getting to an indoor rabbit, especially if you open windows on nice days. Unlike house flies, bot flies do not require the attraction of food, blood, or feces. They are attracted directly to the rabbit himself.

A bot fly looks like a bee (yellow with black stripes,) but it has a curved body that appears to be stinging its victim. There is no stinger. This extension of the fly is merely the tube for laying its eggs on the targeted area. Eggs look like separate, tiny yellow seeds stuck to the tips of individual hairs and are laid one egg at a time. Warm moisture (such as an animal licking himself) will pop open the egg hatch and release the larva to burrow inside its victim. If removal of all eggs cannot be accomplished, warm vinegar should pop the egg hatches and kill the larvae. One kind of bot fly attracted to rabbits in the wild will also lay eggs near rabbit habitat, on leaves or stems of normal vegetation. These eggs hatch when a rabbit brushes against them. When the eggs hatch, cuterebra prefer the area around the rabbit’s neck or under the jaw where they burrow under the skin to eat flesh and grow.

maggots

Unlike other fly maggots that are small and white, cuterebra look like something out of a science fiction movie. They start out white but grow to reticulated black shells covering a slug type body tapered at both ends. They grow in size much larger than the adult bot fly and can be up to one inch long and H inch wide. A larva this size does considerable damage and where one is found, several others may also be present. Because they burrow under the skin as newly hatched larvae, the entrance hole, called a warble, is small and not easily seen. Since the skin is traumatized, the area around the entrance is slightly raised like a bump with inflamed edges. The edges of the hole, if visible, may be blackish. The small hole remains open for emerging when the larval stage of growth is complete. As the cuterebra grow, the area where they have burrowed resembles a tumorous growth and is called a warble tumor. All you may see or feel is the lump.

A rabbit who is having trouble breathing should be checked immediately for any of these lumps. At this stage, death could be imminent and rushing your rabbit to the vet will be the only way to save him. Trying to pull out the enlarged cuterebra on your own could rupture the larva causing toxins to enter the already infected area. The cuterebra may also be deep enough to require surgical removal by your veterinarian.

Treat Fly Strike as an Emergency

If not found in time, the result of fly strike is death. It is far better to carefully examine your companions on a regular basis to avoid such horrendous situations. Inspect the neck for cuterebra holes or yellow bot eggs and then all over (particularly underneath) your rabbit for mushy white fly eggs or larvae. Even low risk rabbits should be immediately examined if they exhibit unusual behavior such as seizure, stupor, or just simple low energy. If you think your rabbit may have fly eggs and you aren’t sure you’ve removed them all, visit your vet as quickly as possible. Regular fly eggs hatch quickly so they must be removed immediately. Cuterebra eggs hatch when moisture touches them. If you find maggots on your pet or cuterebra holes, time is of the utmost importance in getting your pet to the veterinarian. Your rabbit’s life depends on it.

Joy Gioia

House Rabbit Journal Spring 2000: Volume IV, Number 3

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