Cuterebra in cats causing upper respiratory signs | VETgirl Veterinary Continuing Education Videos
In this VETgirl online veterinary continuing education video, we discuss cuterebriasis and how it can cause upper respiratory signs in cats. The rabbit bot fly, or Cuterebra, is a large non-biting fly that is less species-specific than other flies and has been associated with infestations in both the cat and dog. Female flies deposit their eggs on blades of grass around rabbit burrows, waiting for their primary host, the rabbit, to pass through. Occasionally, these eggs may instead be picked up on the fur of indoor/outdoor cats (or other animals such as dogs, foxes, etc.). The eggs hatch in response to body heat, and the larvae migrates into the oronasal passages. The larvae then continues to migrate throughout the body, eventually emerging typically through the skin, where the larvae continues to mature. (The larvae can also emerge elsewhere in the tissue, such as the cornea, nares, etc.). Cuterebriasis is most common in hot humid summer months, and presents with vague clinical signs. When the larvae migrates through the oronasal passages in the cat, clinical signs of secondary inflammation, congestion, and difficulty breathing can occur. Other symptoms in cats include unilateral or bilateral nasal discharge, excessive sneezing, coughing, gagging, fever, epistaxis, or even neurologic symptoms such as ataxia or seizures.
Diagnosis of cuterebriasis can be difficult and is based primarily on clinical symptoms, or direct visualization as a pinpoint “bump” with a central opening (where a Cuterebra larvae may be partially sticking out). A thorough oral exam is recommended and localized regions of oropharyngeal swelling or ulceration may be seen. Typically, sedation is necessary. When clinical symptoms are evident, treatment is warranted. In some cases, the parasite itself can be manually removed, but in most cases, treatment includes a parasiticide (e.g., ivermectin).
Due to the risk of anaphylaxis as the Cuterebra larvae dies, steroids and diphenhydramine are recommended. Often times these are first given as injections, followed by another week or two of prednisolone. In some cases, secondary bacterial infections are treated with antibiotics. Other supportive care, such as fluids or supplemental oxygen, may also be needed. Generally the prognosis is good, with clinical symptoms resolving within a week. Prevention is by keeping cats indoors, especially during hot humid summer months.