Botflies (Cuterebriasis) in Cats

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Last updated on
4 min read

Key takeaways

Botflies are large, bee-like insects, whose larvae cause cuterebriasis in cats. 

  • Cuterebriasis occurs when botfly larvae grow to maturity in a cat’s skin, resulting in large, soft swellings
  • Skin swellings due to cuterebriasis are most commonly found around the head and neck and may be painful and cause reddened or irritated skin
  • Cats with skin swellings benefit from prompt veterinary attention
  • While not usually fatal, larval migration may result in blindness, seizures, or respiratory difficulty, which requires immediate veterinary attention
  • Diagnostics include a physical examination, diagnostic imaging, and bloodwork to identify the larvae
  • Treatment is removal of the larvae from the skin and supportive care
  • Unless neurological symptoms, such as seizures, are present, the prognosis is usually good
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A closer look: Botflies (Cuterebriasis) in Cats

There are multiple species of botfly throughout North and South America. Botflies are most active in the spring and summer months.

Botfly larvae range from 1-2 cm in length, and look like ribbed slugs. Younger larvae are white, and they darken as they grow older. Larval development occurs over a month, after which the larvae drop out of the host’s pores into the environment to continue their life cycle.

Most botfly larvae reside within the skin, producing a soft lump that typically does not bother the host. Cats with skin lumps require non urgent veterinary attention.

Botfly larvae may burrow through various organs such as the eye, brain, or lungs while migrating through their host’s body. This may result in seizures, blindness, or respiratory infections. Cats presenting with serious symptoms benefit from immediate veterinary attention.

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Risk factors

Botflies are common in cats, particularly outdoor cats. Indoor cats are rarely susceptible to cuterebriasis, as the infectious larvae are primarily found in the soil.

Botflies are most common in central and southern America, and cuterebriasis is more common during spring and summer months.

If a botfly larva’s migration passes through nerves, lungs, eyes or another organ, more serious symptoms can manifest.

Possible causes

Botflies lay eggs in soil, vegetation, and grass, which can become caught in the fur of a passing cat. The eggs hatch on the animal’s fur, producing botfly larvae that travel into their host’s body, usually through an opening such as an injury, mouth, or nostril. The parasites then migrate through their host’s body to the skin, where they form a pore to reside within while they mature. In some cases, this migration path may pass through nerves or organs such as the lungs, eyes, or brain.

Main symptoms

The most obvious symptom of cuterebriasis is a large, soft swelling in the skin. This swelling may be painful, and the skin surrounding the area may be red and irritated.

Testing and diagnosis

A physical examination is typically sufficient to find and identify larvae, however other diagnostic tests including bloodwork and diagnostic imaging may be indicated, particularly if larvae migration through internal organs is suspected.

Steps to Recovery

To treat cuterebriasis, the larvae are removed from the skin, and any associated wounds receive appropriate cleaning and care. Anti-parasite medication targets infection of internal organs. Treatment removes larvae but does not prevent reinfection, making recurrence possible.

Prognosis is usually good, however it is more guarded in cases where neurological symptoms present. While rare, euthanasia is sometimes considered when more severe symptoms are present.


The most effective method of preventing cuterebriasis is keeping a cat indoors, where they cannot pick up any eggs.

Routine deworming protocols, keeping a clean and sanitary living place, and periodically bathing an outdoor pet may also prevent maggots from developing.

Are Botflies (Cuterebriasis) in Cats common?

Botflies are common in cats.

Typical Treatment

  • Larvae removal
  • Symptomatic treatment as required


Karen A. Moriello - Writing for Merck Veterinary Manual
Lindsay A. Starkey - Writing for Today's Veterinary Practice
No Author - Writing for Companion Animal Parasite Council

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