A two-year-old male castrated rabbit in the USA is housed in an outdoor hutch for the warm spring and summer months. The owner noticed an area of matted fur on the side of the rabbit’s neck that seems painful. Otherwise the rabbit is acting bright and alert, passing normal droppings and has a good appetite. The matted fur around the area is clipped and beneath it is found a subcutaneous swelling with a small hole at its tip.
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What word best describes this condition?
Myiasis, defined as the infestation of living animals with dipteran fly larvae. The larva embedded in the neck of this rabbit is most likely a Cuterebra spp. (order Diptera, family Cuterebridae), also called the rabbit botfly.
Adult Cuterebra flies are large and do not bite or suck blood.
The females lay eggs around the openings of animal nests and burrows or on plants and stones in these areas.
The larvae enter the host through the mouth or nares during grooming, or through open wounds.
The larvae then migrate to subcutaneous locations along the dorsum, axillary, inguinal and ventral cervical areas, where they pupate and form a breathing hole to the surface.
For the most part, other than local pain and inflammation, rabbits are systemically unaffected by Cuterebra infestation.
However, some rabbits can present for lameness, or are weak, anorectic and/or dehydrated.
Larvae can be up to 25 × 10 mm (1 × 0.4 inches) in size and have black cuticular spines, which give them their characteristic dark appearance.
First, a thorough physical examination should be conducted to ensure that no more larvae are present on the rabbit.
Mild sedation or general anaesthesia may be required for larval removal.
After preparing the area for surgery, the air hole should be gently expanded with haemostat tips.
The larva should then be pulled through the widened opening. There are anecdotal reports of larval rupture causing anaphylaxis in the host, so care must be taken to remove the larva in one piece.
After larval removal, the area should be thoroughly flushed with sterile saline and debrided as needed.
Oral analgesics and antibiotics should be prescribed.
If the swelling does not resolve or if it worsens, surgical excision of the affected tissues may be necessary.
The owner should be advised that the best prevention is to limit exposure of the rabbit to flies, either by keeping the rabbit indoors during the fly season or installing a protective screen over the hutch.
