Warble fly

Hypoderma bovis

Hypoderma bovis larvae young

Warble fly refers to several species of botfly (family Oestridae) that are parasitic on animals, including humans, in their larval stage. The most common hosts for these flies are cattle and deer, but they can also affect other mammals. The larvae of the warble fly are known as "warbles" and cause a condition in cattle known as "warble fly infestation" or "hypodermosis".

Life Cycle

The life cycle of the warble fly is complex and involves several stages. Adult flies lay their eggs on the legs of the host animal. Upon hatching, the larvae penetrate the skin of the host and migrate through the body. Eventually, they settle beneath the skin, usually along the back or sides of the animal, where they form large, palpable swellings known as warbles. After maturing, the larvae exit the host's body to pupate in the soil, completing their life cycle.

Impact on Livestock

Warble fly infestations can have a significant economic impact on livestock production. Infected animals may suffer from leather damage due to the holes created by the larvae when they exit the skin, reduced milk production, weight loss, and general ill health. The presence of warbles can also lower the value of hides and cause discomfort and irritation to the animals.

Control and Prevention

Control measures for warble fly infestations include the use of systemic insecticides and the application of pour-on insecticides to the back of cattle. Preventive measures focus on breaking the life cycle of the fly, such as treating animals before the larvae mature and exit the skin, and managing the environment to reduce fly populations.

Human Cases

Although rare, humans can also become hosts to warble fly larvae, a condition known as myiasis. This occurs when the larvae are accidentally transferred to humans, usually through contact with infested animals or contaminated materials. In humans, the larvae can cause painful swellings and, in severe cases, may require surgical removal.

Species

Several species of warble flies are known to affect livestock, including Hypoderma bovis and Hypoderma lineatum in cattle, and Oedemagena tarandi in reindeer. Each species has a slightly different life cycle and preferred host, but the general pattern of infestation and impact on the host is similar.