Cuterebrosis in Cats

Botflies, flies that are of the genus Cuterebra, are found in the Americas, where they are obligatory parasites of rodents and rabbits. The botfly proliferates by laying eggs on blades of grass or in nests, where they hatch, releasing maggots that crawl onto the skin of passing animals. The small maggots then enter a body orifice, migrate through various internal tissues, and ultimately make their way to the skin, where they establish themselves within the skin, creating a warble (a small lump in the skin). The mature maggots, which may be an inch long, then drop out of the rodent or rabbit host and pupate in the soil.

Cats become infected with a botfly larva when they come into contact with a blade of grass that has a maggot on it. The movement of the cat against the blade of grass stimulates the maggot to crawl onto the cat. The maggot then crawls around on the cat until it finds an orifice in which to enter.

In the northern U.S. the disease is seasonal, with most cases occurring in late summer and early fall when the adult flies are active. Seasonality is less determined in areas with warmer temperatures, where flies are active through longer periods of the year.

Symptoms and Types

Cuterebra infection may be detectable by warbles below the surface of the skin, or your cat may show signs associated with the larvae migrating within their tissues. Symptoms can include respiratory signs, neurological signs, opthalmic (eye) lesions, or the aforementioned maggots under the skin.

Respiratory symptoms:

• Cough
• Fever
• Shortness of breath

Neurological symptoms:

• Dizziness
• Circling
• Paralysis
• Blindness
• Lying down

Opthalmic symptoms:

• Lesions (caused by the larvae in the eyeball)

Skin symptoms:

• Lump in the skin containing the maggot, also called a warble; there will be a raised opening in the lump so that maggot may breathe

Causes

The most likely place for your pet to acquire this parasite is in an environment where the botfly flourishes: grassy areas where there are adequate populations of rodents and rabbits. But, even pets without access to the outdoors, such as newborn kittens, can be infected from larvae brought home on the mother's fur.