Botfly Warbles in Rabbits and Rodents

By Phyllis O’Beollain

Botfly season will soon be upon us (let’s hope the botflies will NOT) Warbles are the larval stage of the botfly, which typically infects rodents and rabbits. Twenty-six species of botflies occur in the U.S. and Canada, although they are also found in Mexico as well as the tropics. These are not your normal houseflies; botflies are large (20 mm or more), dark blue or black, and have fine, dense hairs on the face and thorax.

In the northern U.S. the disease is seasonal; most cases occur in late summer and early fall when the adult flies are most active. In warmer climates the flies are active for most of the year. Botflies lay their eggs on the pet itself; these eggs then hatch and release maggots which either crawl to and enter a wound or other body opening, or are ingested into the pet during grooming. The nose, mouth, rectal area, or minute skin abrasions are all means for entering the pet. The larvae then migrate through the internal tissues to an area under the pet’s skin, making a small hole in the skin so they can breathe. At this point there is a noticeable lump in the skin (the warble) with a small hole; in small pets this is common found on the neck area. Sometimes the tip of the larva will be visible deep in the hole. NEVER squeeze the skin in hopes of getting the larva out. The sac in which the larva is confined is filled with deadly toxins; if ruptured these toxins will enter the pet’s bloodstream, causing severe illness and death. The warble will need to be removed by an experienced veterinarian who may anesthetize the pet before the procedure. Left untreated, the open wounds caused by the larvae can lead to infections and possibly the death of the pet. Any lump underneath your pet’s skin must be evaluated as soon as possible by your veterinarian.

After removal, antibiotics will likely be prescribed to prevent any secondary infections; the secondary infections can have a negative impact on the pet worse than the original attack by the warbles, so make sure to give the medications as prescribed.

While warbles below the skin’s surface are usually the first sign noticed by the pet owner, symptoms associated with larvae migration include respiratory and/or neurological signs or opthalmic (eye) lesions. Prevention is the key in keeping your rabbits and other small pets safe from botflies. Keep their housing and environment scrupulously clean. Check your pet daily for wound or unclean areas that attract flies to lay their eggs. The fur in your pet’s private area may need to be trimmed, especially if the pet is very fuzzy, overweight or disabled and unable to properly groom themselves.

Taken from Botfly warbles in rabbits and rodents – Dayton small pets |