Infestations
The fly will lay eggs on the foreleg of the affected cattle. These will be ingested by licking, and be swallowed. Internal cycle involves the passing oesophagus muscles and spinal cord before subcutaneous re-emerging.
When they re-emerge, the larvae cause many swellings ("warbles") under the skin, causing some harm to animals, but not as a general disease. It doesn't burrow into the flesh, but stays under the skin (hence, its scientific name Hypoderma). Nevertheless, when accidentally destroyed by pressure, the larvae can cause large purulent swellings.
From the subcutaneous swelling, the warble will bore through the skin when coming out of the bovid. When there many such punctures they render the hide valueless.
The migrating larvae can cause damage to meat as the tunnels they make fill with a substance known as butcher's jelly. Infestations also may seriously reduce the profitability of livestock production because they commonly injure the health of infected animals to the extent that weight gain and growth rates suffer. Milk yields may decline too, but in adult cows infestations generally are limited by immunity arising from the first infection while the animal is young.
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