New World Screwworm: What Show Families Need to Know

New World screwworm is a fly whose maggots eat living flesh. It lays its eggs in open wounds on any warm-blooded animal, and it is now in the United States. The first U.S. case was confirmed in Texas in June 2026, and by October cases had turned up in livestock in Texas and New Mexico. If you show cattle, pigs, lambs or goats, three things matter today:

• Look at every animal for wounds at every feeding.
• Know your state’s rules before you haul.
• If you ever find maggots in a wound, call your veterinarian that day.

I wrote this for show families anywhere in the country, with a section at the end for anyone headed to the Texas shows this winter.

What makes screwworm different

Most maggots you will ever see around a barn feed on manure and dead tissue. Screwworm maggots eat living tissue. The female fly lays a mass of eggs at the edge of a wound. The maggots hatch, burrow in and feed, and the wound gets bigger and deeper instead of healing. When they finish, they drop to the ground and turn into pupae in the soil, and a new fly comes out to find the next wound.

That matters for your fly plan. Screwworm does not breed in manure or wet bedding, so the barn cleanup in our fly control article will not stop it. Keep doing that work for house flies and stable flies, but know that screwworm is a wound problem.

It spreads two ways: by the fly itself, and by animals that carry an infested wound when they are moved.

Where it is now

As of late October 2026, USDA has confirmed screwworm in domestic animals in Texas and New Mexico, and in one wild elk in West Texas. Texas draws quarantine zones, which it calls infested zones, around confirmed cases and changes them often. The picture changes week to week, so check the latest at screwworm.gov, USDA’s screwworm site, and with your state animal health agency.

What it looks like on a show animal

Watch for:

• a wound that drains, smells like something rotting, or keeps getting bigger;
• maggots in a wound, or clusters of creamy white eggs at its edge;
• an animal that acts irritated, rubs at a spot or keeps shaking his head.

Any fresh wound is a target. In a show barn, that means:

• fresh ear tags, ear notches and tattoos;
• nicks from clipping or shearing;
• halter and chain rubs;
• fight wounds when pigs are mixed;
• castration, docking and dehorning wounds;
• the navel of a newborn;
• around the nose, the eyes and the genitals.

If you find it

• Call your veterinarian that day. Screwworm is a reportable disease, and your vet will report it to the state.
• Do not dig out the maggots or treat the wound yourself.
• Keep the animal apart from the others and on your place. Do not haul it anywhere.
• If you can, loosely cover the wound with clean gauze to keep more flies off it until your vet gets there.

In Texas, you can also call the Texas Animal Health Commission at 1-800-550-8242.

Preventing it at home

• Check every animal for wounds at every feeding, morning and night.
• Make fewer wounds during fly season. Talk with your vet before you tag, castrate, dock or dehorn, and plan the timing of those jobs with your vet if you are anywhere near a zone.
• Protect the wounds you cannot avoid. FDA has authorized a short list of products to prevent and treat screwworm, and which one fits depends on your species. Use the one your veterinarian recommends.
• Keep up the rest of your fly control, for the flies that do breed in the barn.

Hauling and showing

• Know where your county stands. In Texas, animals cannot leave an infested zone without authorization from the Texas Animal Health Commission. That means an inspection and a screwworm movement certificate before you load.
• Know where you are going. Each state sets its own entry rules for animals from affected areas, such as a recent health certificate or an entry permit.
• Check each show’s health requirements as soon as they are posted, and again before you leave. They can change between entry day and show day.
• Look your animals over at the show, and again when you get home.

The Texas Pork Producers Association keeps screwworm resources for exhibitors.

People can get it too

Screwworm can infest people as well. If you find a wound on yourself that will not heal, or that seems to have something moving in it, see a doctor right away.

Questions show families ask about screwworm

What is New World screwworm?

A fly that lays its eggs in open wounds on any warm-blooded animal. Its maggots eat living flesh, so the wound grows instead of healing. It was confirmed in the United States in June 2026.

Can show pigs, cattle, lambs and goats get screwworm?

Yes. Any warm-blooded animal can, including pets and people. Fresh wounds are the risk: ear tags and notches, clipping and shearing nicks, castration and docking, fight wounds and the navels of newborns.

Where is screwworm in the United States right now?

As of October 2026, USDA had confirmed cases in livestock in Texas and New Mexico, plus one wild elk in West Texas. It changes often, so check screwworm.gov and your state animal health agency.

What does screwworm look like on an animal?

A wound that drains, smells like rot or keeps getting bigger, with maggots in it or creamy white eggs at its edge. The animal often acts irritated or keeps shaking his head.

What should I do if I find maggots in a wound?

Call your veterinarian that day. Do not dig out the maggots or treat the wound yourself. Keep the animal apart from the others and on your place, and let your vet report it.

Can I haul my animals to a show from a screwworm zone?

Only with authorization. In Texas, animals leaving an infested zone need an inspection and a movement certificate through the Texas Animal Health Commission, and the state you are hauling to may have its own entry rules. Check the show’s health requirements early.

Can people get screwworm?

Yes. If you have a wound that will not heal, or that seems to have something moving in it, see a doctor right away.