What’s the Deal with Screwworms?
- ZISK
- 5 days ago
- 1 min read
Last week, U.S. Secretary of Agriculture Brooke Rollins announced the suspension of imports of live cattle, horses, and bison across the U.S. southern border due to the rapid northward spread of New World Screwworm (NWS) in Mexico. Producers are understandably concerned and are asking how worried they should be.
How is the Screwworm different than other fly maggots?
The NWS differs from other fly species because its larvae can burrow or “screw” themselves into the healthy tissue of any warm-blooded animal. During its roughly 20-day lifecycle, an adult female fly can lay up to 3,000 eggs into tiny, inconsequential scratches or even healthy mucus membranes, such as those of the eye or vulva. Recent surgical sites for castration or dehorning and newborn calves’ navels can also be infested. As these maggots migrate through otherwise healthy tissue, they can cause pain, production losses, and even death.
What does Screwworm infestation look like?
The most obvious sign is a wound that is not healing properly, but is rather getting larger and deeper. The wound may be accompanied by the smell of rotting flesh and a bloody discharge. Maggots may be visually evident.
May 27, 2025
Comments