Get vaccines, antibiotics, and other supplies delivered directly to your farm.
Wound getting worse instead of better? Call your veterinarian today — don't wait.
Maggots visible in a wound? Do not treat it yourself. Report it immediately (numbers below).
New wounds during fly season? Check daily for the first 5–7 days after branding, tagging, calving, or any injury.
New World screwworm (NWS), caused by the larvae of the fly Cochliomyia hominivorax, is no longer a hypothetical threat for U.S. producers — it's an active outbreak. As of June 22, 2026, USDA has confirmed 15 cases in the United States: 14 in Texas and 1 in New Mexico. The first U.S. detection in nearly 60 years was confirmed June 3, 2026, in a three-week-old calf in Zavala County, Texas.
Producers deal with flies every year. NWS is different. Instead of simply irritating cattle, the larvae feed on living tissue, turning a routine wound — from branding, castration, ear tagging, or injury — into a serious, potentially fatal animal health emergency. Left untreated, infestations cause severe tissue damage, secondary infection, and death.
The U.S. eradicated NWS in 1966 through a sterile-fly program. An outbreak that began moving north through Central America and Mexico in 2023 has now reached Texas and New Mexico, prompting active surveillance, quarantine zones, and a coordinated USDA-state response.
Total confirmed U.S. cases: 15 (14 Texas, 1 New Mexico) as of June 22, 2026
First detection: June 3, 2026 — calf, Zavala County, Texas
Affected species so far: Cattle, goat, dog
Texas quarantine/infested zone counties: Coke, Crockett, Edwards, Gillespie, Kerr, Kimble, La Salle, Schleicher, Sutton, Tom Green, Uvalde, Val Verde, Webb, and Zavala. Animals in these counties cannot move out of the zone without prior TAHC authorization. View the current zone map →
Response underway: USDA has activated a sterile fly dispersal facility at Moore Air Base in Edinburg, Texas, with aerial releases of sterile NWS flies now underway along the border and in affected counties.
This is an evolving situation. For the latest official case counts and quarantine updates, see screwworm.gov and the USDA APHIS newsroom.
NWS flies are attracted to any open wound or natural opening on an animal. Be especially vigilant around:
Branding, castration, and dehorning wounds
Ear tag placements
Cuts, abrasions, and tick bites
Navel areas on newborn calves
Animals recovering from injuries or processing
Cattle with heavy tick pressure
Once eggs are deposited, larvae hatch and begin feeding on living tissue immediately. Unlike a normal wound that gradually heals, screwworm infestations worsen over time. Close observation during and after processing, calving, transport, or any event that increases wound risk is critical for early detection — USDA and Texas officials are urging daily inspection of animals in and near affected areas.
Animals affected by screwworm may show:
Wounds that enlarge rather than heal
Bloody or foul-smelling discharge
Irritation around a wound site
Excessive licking or rubbing
Head shaking
Reduced appetite
Depression or lethargy
The single most important warning sign: a wound that appears to be getting worse instead of better.
Do not attempt to diagnose or treat suspected cases on your own.
If an animal has a wound containing maggots, or a wound that appears abnormal and continues to worsen, contact your veterinarian or state animal health official immediately. NWS is reportable and should be reported within 24 hours of suspicion.
Texas: TAHC Veterinarian on Call — 1-800-550-8242, or your TAHC Region Office
New Mexico / other states: Contact your state animal health official or local USDA Area Veterinarian in Charge
All states: screwworm.gov reporting guidance →
Early reporting is critical for containment and helps animal health officials respond quickly.
Monitor animals daily. Frequent, even daily, observation helps catch wounds before they become larger problems — especially for young animals, recently worked cattle, and animals recovering from injury.
Manage fly pressure. A strong fly control program reduces insect pressure herd-wide and supports overall health through fly season.
Treat and protect wounds promptly. Clean wounds immediately, monitor healing progress daily, and consult your veterinarian on appropriate treatment.
Plan processing activities carefully. Where possible, time branding, tagging, and castration around periods of lower fly activity, and increase monitoring frequency after any processing event during warm months.
No over-the-counter product replaces veterinary guidance or official treatment protocols — but the right products support daily wound management and fly control, including:
Find more animal health essentials in the FBN Store.
What is New World Screwworm? New World screwworm is the larval (maggot) stage of the fly Cochliomyia hominivorax. Unlike most flies, NWS larvae feed on living tissue rather than dead tissue, entering animals through open wounds or natural openings and causing painful, enlarging wounds.
Is New World Screwworm in the U.S. right now? Yes. USDA confirmed the first U.S. case in nearly 60 years on June 3, 2026, in Texas. As of June 22, 2026, there are 15 confirmed cases across Texas and New Mexico.
How do I know if my cattle have screwworm? Watch for a wound that's enlarging or not healing, foul-smelling or bloody discharge, visible larvae, excessive licking or head shaking, and reduced appetite. The clearest red flag is a wound getting worse over time rather than better.
What do I do if I find maggots in a wound? Don't treat it yourself. Contact your veterinarian or state animal health official immediately — in Texas, call the TAHC Veterinarian on Call at 1-800-550-8242. Reporting within 24 hours is required and critical to containment.
Does NWS affect the food supply? No. USDA and FSIS confirm NWS does not infest meat, fruits, vegetables, or other food products, and the U.S. food supply remains safe.
© 2014 - 2026 Farmer's Business Network, Inc. All rights Reserved. The sprout logo, “Farmers Business Network”, “FBN”, "Farmers First", “FBN Direct” , "F2F", and "F2F Genetics Network" are trademarks or registered trademarks of Farmer's Business Network, Inc.
FBN Direct products and services and other products distributed by FBN Direct are offered by FBN Inputs, LLC and are available only in states where FBN Inputs, LLC is licensed and where those products are registered for sale or use, if applicable. If applicable, please check with your local extension service to ensure registration status. Nothing contained on this page, including the prices listed should be construed as an offer for sale, or a sale of products. All products and prices are subject to change at any time and without notice and excludes CA mills tax and MN ACRRA fees. Terms and conditions apply.
ALWAYS READ AND FOLLOW LABEL DIRECTIONS. We do not guarantee the accuracy of any information provided on this page or which is provided by us in any form. It is your responsibility to confirm prior to purchase and use that a product is labeled for your specific purposes, including, but not limited to, your target pest, illness, or deficiency and its approval for use on your animal's species and that the usage of a product is otherwise consistent with federal, state and local laws. We reserve the right to restrict sales on a geographic basis in our sole discretion.
The above is provided for information purposes only and should not be used for the diagnosis or treatment of any condition. This information does not cover all possible variables, conditions, reactions, or risks relating to any topic, medication, or product and should not be considered complete. Certain products or medications may have risks and you should always consult your local veterinarian concerning the treatment of your animals.