Flesh-Eating Screwworm Is Spreading Again in Texas Ranch Country—And Ranchers Are Paying Close Attention

For many Texas ranchers, the word “screwworm” still carries the kind of weight usually reserved for drought, wildfire, or disease outbreaks.

Older ranching families remember the stories well. Livestock with unexplained wounds suddenly worsened. Calves weakened quickly. Wildlife suffered in silence. Routine cuts or branding injuries sometimes turned into serious problems almost overnight.

For decades, most Texans believed those days were gone.

Now, concern is growing again.

A recent case involving the deadly New World screwworm has ranchers, veterinarians, and wildlife managers paying close attention after confirmation that the flesh-eating parasite has resurfaced close enough to Texas to raise alarm throughout ranch country.

The concern, according to livestock experts, is not panic.

It is preparedness.

What Exactly Is a Screwworm?

Despite the name, a screwworm is not technically a worm.

According to the United States Department of Agriculture, the New World screwworm is the larval stage of a parasitic fly whose maggots feed on the living flesh of warm-blooded animals. Unlike common flies that target dead tissue, screwworm larvae invade open wounds and continue feeding on healthy living tissue, often causing severe infections, suffering, and in some cases death if left untreated. According to the USDA, livestock, deer, pets, wildlife, and even humans can potentially become infected. (aphis.usda.gov)

The parasite historically devastated livestock industries across the southern United States.

Before eradication efforts succeeded, ranchers routinely inspected cattle for wounds because seemingly minor injuries could quickly become dangerous. Branding marks, cuts from fencing, tick bites, and even navels on newborn calves reportedly created opportunities for infestation.

According to agricultural historians, the economic damage once reached staggering levels.

Why Ranchers Are Suddenly Concerned Again

The renewed concern comes after officials confirmed recent screwworm detections in Mexico close enough to trigger heightened monitoring and preparation efforts along the Texas border.

According to the USDA and the Texas Animal Health Commission, recent cases south of the border have prompted increased surveillance, movement restrictions, and renewed conversations about emergency response should the parasite move farther north. Officials continue emphasizing that no widespread outbreak currently exists across Texas, but ranchers are being encouraged to remain alert. (texasagriculture.gov, aphis.usda.gov)

That concern feels especially real in South Texas.

Because warm temperatures, heavy wildlife movement, and large cattle operations create conditions where ranchers understand problems can spread quickly if early warning signs go unnoticed.

According to livestock veterinarians, early detection matters enormously.

What Ranchers Are Watching For

The challenge with screwworm often begins with how deceptively normal it can look at first.

According to the USDA, infected animals may initially appear irritated, isolate themselves, or show unusual behavior around wounds. Ranchers may notice foul-smelling infections, movement inside wounds, swelling, drainage, or animals repeatedly licking and biting irritated areas. Livestock often lose condition quickly if infestations worsen. (aphis.usda.gov)

For wildlife managers, the concern extends beyond cattle.

Whitetail deer, exotic game, feral hogs, and other wildlife species could also become hosts if infestations spread, creating challenges that stretch far beyond ranch fences.

That possibility explains why many hunters increasingly pay attention as well.

Because a livestock problem can quickly become a wildlife problem.

Texas Beat Screwworm Before—But It Took Massive Effort

Many ranchers remember—or grew up hearing about—how the United States finally defeated screwworm decades ago.

According to the USDA, one of the largest insect eradication efforts in American history relied on releasing millions of sterile male flies into affected areas. Because female screwworm flies only mate once, breeding populations gradually collapsed when sterile males disrupted reproduction cycles.

The program worked.

By the 1960s and 1970s, screwworm had largely disappeared from the United States, with buffer efforts continuing farther south to reduce reinfestation risk. (aphis.usda.gov)

That success, however, never meant the threat vanished forever.

Which partly explains why current reports immediately grab ranchers’ attention.

The Bottom Line

The New World screwworm may sound like something from another era, but renewed detections south of the Texas border are reminding ranchers how quickly old livestock threats can return.

According to agricultural officials, Texas currently remains free from widespread infestation, but ranchers are being encouraged to watch livestock closely and report suspicious wounds quickly.

For families who make their living on the land, the concern is not about fear.

It is about staying ahead of problems before they become something much harder to stop.