How do bot fly and warble fly larvae affect large mammals?

Bot fly and warble fly larvae (family Oestridae) are internal parasites that significantly impact large mammals, causing physical damage and economic losses.123

Mechanisms of Infestation

• Skin Penetration: Species like the cattle grub (Hypoderma lineatum and H. bovis) deposit eggs on the host's legs. Upon hatching, larvae burrow through the skin and migrate through subcutaneous tissues for several months before settling under the skin of the back to form a "warble" or cyst.123
• Ingestion: Some larvae, such as those of the horse bot fly (Gasterophilus), are ingested when a host licks its hair. These larvae attach to the lining of the stomach or intestine, deriving nourishment from the alimentary canal for nearly a year.3
• Nasal and Tissue Infestation: Other species deposit larvae in the nostrils, which can lead to severe conditions like "blind staggers" in sheep. The human bot fly (Dermatobia hominis) utilizes other insects to transport eggs to a host, where larvae penetrate the skin.3

Impact on Hosts

These infestations cause significant harm, including the reduction of meat, milk, and hide quality, and can lead to secondary infections or nervous conditions.13