The Dr. McDonald Column — Screw Worms Are Where I Started

By Dr. Steve McDonald 

What drove me to be a vet? It all started when I was 13. My great-grandfather had a ranch in Young County. He owned about 400 head of cattle, all Hereford, and about a dozen head of horses. He calved in the fall, hopefully after frost.

Earlier calving, or a late frost, insured that the newborn calves would be infested with screw worms, the maggots of tropical flies that ate living flesh.

They would set up housekeeping in the fresh, raw navels of the baby calves and snack away. The adult flies couldn’t survive the winter in North Texas, but would ride the southern winds from Mexico every spring, arriving by early June at the latest.

If conditions were right, meaning a strong southwesterly wind, the flies might arrive by mid-April. A couple of days of this wind was all it took to bring on an early fly season. It was horrible. The cattle would have to be gathered and the babies would have to be treated on their navel with a vile-smelling concoction that would kill the maggots.

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