New World Screwworm: A Texas Dairy Farmer’s Preparedness Guide
New World screwworm is a fly larva that infests living animals, and it has Texas producers paying attention. Here is a plain preparedness plan, with current status and rules left to the official agencies.
What is New World screwworm?
New World screwworm is a parasite whose fly lays eggs in wounds on warm-blooded animals. The larvae feed on living tissue, which is what makes it so damaging. It was eliminated from the United States decades ago, and its current status in Mexico and near the border is as reported by federal agencies, so check USDA APHIS for the latest.
Dairy cattle are not immune. Navels on newborn calves, wounds from fences, dehorning sites and teat injuries are places a fly might lay eggs.
Public health background on parasites is available from the CDC. Because the biology is so specific, vets are the best teachers here. A short conversation about what an infested wound looks like, and what to do and not do, is time well spent before it matters.
Why should a Texas dairy care?
Texas is closest to the risk because of its border and its warm climate. Even if you are in the cooler Panhandle, animal movement and trade can bring concerns to every region. A plan made in advance is easier than panic later.
The state's animal health agency, the Texas Animal Health Commission, will publish whatever rules apply, and the Texas Department of Agriculture covers broader state programs. Confirm both before making decisions.
If you have family or workers who also keep horses, dogs or backyard livestock, share the same message. The parasite does not care what species the wound is on, and early reports from any animal help the whole community.
What should daily animal checks include?
Make wound checks part of the routine. Look at navels, hooves, udders, dehorning sites, tags and any scrapes, and ask your crew to report anything unusual immediately. Fresh cows and calves deserve extra attention.
A few practical steps help, and your veterinarian can tailor them to your herd. Keep a simple log of who checked what, and make sure everyone knows who to call.
Calving season needs special attention. Newborns spend time on the ground and their navels are slow to dry, so make navel care part of the calving checklist and check again the next day.
- Inspect navels on newborn calves
- Check hooves, teats and any fresh wounds
- Report unusual wounds to your vet immediately
- Record findings in a daily log
How do you handle wounds and treatment?
Do not improvise. Wound care and any treatment products should be chosen with your veterinarian, who knows what is approved and what meets milk withdrawal requirements. The FDA regulates animal drugs, and withdrawal times matter for a dairy.
Keep wound supplies clean and stocked, and separate affected animals according to your vet's advice. The dairy herd care guide covers general herd health routines you can build on.
Ask your vet which wound products are labeled for dairy cattle and what the withdrawal times are. Do not use a product just because a neighbor swears by it, since the milk may need to be held out of the tank.
What about insects, movement and trade?
Fly control is part of a normal dairy program, and it helps here too. Manure management, clean bedding and trap placement reduce fly pressure. Extension specialists at Texas A&M AgriLife Extension can suggest options for your region.
Animal movement rules may change if the pest is found nearby. Ask where replacement animals have been, check health papers carefully and watch for new announcements. The beef cattle care guide has movement tips that also apply to dairies.
Pasture and dry lot cattle should get the same checks as the milking string. Heifers on rented grass are easy to forget, so build a rotation that puts eyes on them regularly.
Who should be in your call list?
Write down your veterinarian, the animal health commission and your extension office, and post it in the milk barn. If you suspect an infestation, call right away. Early reporting is how outbreaks stay small.
Over at farm.FM they keep a good sense of humor about farm life, and you can browse their dairy stories, farming stories and a farm.FM piece on screwworm and cattle. Humor is fine when the barn is quiet; when a wound looks wrong, put the phone to your ear.
How should you talk with the crew and your lender or buyer?
Brief everyone in plain terms: what it is, what to look for, who to tell. Keep the message short and repeat it, since a one-time talk is forgotten by the next shift. If you employ people who speak Spanish or another language, make sure the plan is available in it.
If the pest is found nearby and trade rules tighten, your milk buyer, lender and insurer may all ask questions. Keep your records tidy and your veterinarian informed. The farm finance basics guide helps you think through cash flow if movement restrictions affect your operation.
Sources and further reading
- USDA APHIS: animal and plant health
- Texas Animal Health Commission: animal disease rules
- Texas Department of Agriculture: state agriculture agency
- FDA: food and drug safety
- Texas A&M AgriLife Extension: Texas extension service
- USDA: U.S. Department of Agriculture
Ask locally: Call your herd veterinarian or the Texas Animal Health Commission if you see an unusual wound.