Flesh-Eating Screwworm Returns to the United States After 60 Years, Triggering Emergency Response in Texas

First Confirmed U.S. Case Since 1966 Raises Concerns for Livestock Industry

For the first time in six decades, U.S. authorities have confirmed the presence of the dreaded New World Screwworm, a flesh-eating parasite capable of causing severe injuries and death in livestock if left untreated.

The discovery was made in a three-week-old calf in South Texas, marking the first confirmed U.S. case since 1966 and prompting an immediate response from federal and state agricultural agencies.

Although officials emphasize that the risk to the general public remains low, the detection has raised significant concerns among ranchers, veterinarians, and livestock producers across the country.

The parasite’s return represents a challenge many experts believed had been eliminated from the United States generations ago.

What Is the New World Screwworm?

The parasite, known scientifically as New World Screwworm, is not actually a worm.

It is the larval stage of a fly.

The adult fly itself is relatively harmless.

The danger comes after the female lays eggs.

Unlike ordinary flies that deposit eggs on dead or decaying tissue, New World Screwworm flies target living animals.

Females lay eggs in:

• Open wounds
• Surgical incisions
• Umbilical areas of newborn animals
• Mucous membranes
• Minor skin injuries

Once the eggs hatch, the larvae begin feeding on living flesh.

This behavior makes the parasite particularly destructive.

Why the Screwworm Is So Dangerous

Most fly larvae consume dead tissue.

New World Screwworm larvae are different.

They actively burrow into healthy living tissue.

As they feed, they enlarge wounds and create deep lesions that can become infected.

The infestation causes:

• Severe pain
• Tissue destruction
• Secondary bacterial infections
• Weight loss
• Reduced productivity
• Death in severe cases

If untreated, the larvae continue feeding and growing until they mature.

The damage can become extensive, especially in young animals.

For newborn calves, the risk is particularly high because their healing umbilical cords provide an ideal entry point.

The Texas Case

According to the United States Department of Agriculture, the infected calf was discovered near La Pryor, approximately 30 miles from the U.S.-Mexico border.

The animal was only three weeks old.

Inspectors found screwworm larvae in the calf’s umbilical region.

The location immediately raised concerns because the parasite has been advancing northward through Mexico over the past year.

The discovery suggests that the screwworm’s geographic expansion has now reached the United States.

A Parasite Once Eradicated From the U.S.

The New World Screwworm was once one of the most devastating livestock pests in North America.

For decades, ranchers suffered major economic losses due to infestations.

The United States ultimately eliminated the parasite through one of the most successful pest-control programs in history.

The effort relied heavily on the Sterile Insect Technique (SIT).

This strategy involved releasing millions of sterilized male flies into affected areas.

Because female screwworms mate only once during their lives, mating with a sterile male prevents reproduction.

Over time, the population collapses.

The program successfully eradicated the screwworm from the United States in 1966.

Since then, control efforts have focused on maintaining a barrier farther south.

The new detection represents the first breach of that protection system in sixty years.

How the Parasite Spread Northward

Over the past year, authorities have monitored increasing screwworm activity in parts of Central America and Mexico.

The parasite gradually expanded its range northward.

Several factors may contribute to such movements, including:

• Livestock transportation
• Wildlife migration
• Environmental conditions
• Climate variability

As infestations moved closer to the U.S. border, agricultural agencies increased surveillance efforts.

The Texas case confirms that the threat has now crossed into U.S. territory.

Emergency Containment Measures

Federal and state authorities have moved quickly to contain the infestation.

Officials announced the creation of a 20-kilometer detection and quarantine zone surrounding the affected area.

The goal is to:

• Identify additional cases
• Prevent animal movement from affected zones
• Monitor local livestock populations
• Reduce opportunities for parasite spread

Veterinary teams are conducting inspections and surveillance throughout the region.

Early detection is considered essential because infestations can spread rapidly if left unchecked.

The Return of the Sterile Fly Strategy

The USDA plans to deploy one of its most effective historical weapons against the parasite.

Millions of sterile screwworm flies will be released into affected areas.

This technique has several advantages:

Environmentally Friendly

Unlike widespread pesticide use, sterile fly releases specifically target the screwworm population.

Proven Effectiveness

The method was responsible for the parasite’s original eradication from the United States.

Long-Term Population Suppression

Because female screwworms mate only once, sterile males can dramatically reduce future generations.

Agricultural experts widely regard the sterile insect technique as one of the greatest success stories in modern pest management.

Debate Over the Response

Not everyone agrees that current efforts are sufficient.

Brooke Rollins stated that USDA teams are already active in South Texas and urged ranchers to remain vigilant.

Meanwhile, Sid Miller criticized aspects of the federal response.

Miller argued that authorities reacted too slowly and placed excessive reliance on sterile-fly releases.

The disagreement highlights broader concerns about how aggressively officials should respond to the threat.

Despite differing opinions, both state and federal agencies agree that rapid containment is essential.

Potential Economic Impact

The livestock industry is watching developments closely.

A widespread screwworm outbreak could have significant consequences for:

Cattle Producers

Infested animals often require treatment, veterinary care, and additional labor.

Severe infestations can reduce herd productivity.

Beef Supply

Large-scale outbreaks could decrease cattle numbers and affect meat production.

Consumer Prices

Reduced supply could contribute to higher beef prices.

International Trade

Some trading partners impose restrictions when animal disease or parasite outbreaks occur.

While a single case does not guarantee major disruptions, officials are taking the threat seriously because of the potential economic consequences.

Can Humans Be Infected?

Yes, but human cases are uncommon.

The parasite occasionally affects people under specific circumstances, particularly when open wounds are exposed to egg-laying flies.

Human infections can be painful and require medical treatment.

However, public health officials emphasize that the overall risk to people remains low.

Most cases occur in livestock.

The current detection does not represent a major public health emergency.

What About Pets?

Dogs and other pets can also become infected.

Veterinarians recommend monitoring animals for:

• Unusual wounds
• Persistent sores
• Swelling
• Foul-smelling lesions
• Visible larvae

Prompt veterinary attention is important if an infestation is suspected.

Early treatment is typically very effective.

Is the Food Supply at Risk?

Officials stress that the current situation does not pose a food safety threat.

The screwworm parasite affects living animals before slaughter.

Routine meat inspection systems remain in place.

Consumers do not face increased risk from purchasing beef or other meat products due to the Texas case.

The primary concern involves animal health and agricultural economics rather than food safety.

Why This Discovery Matters

The return of the New World Screwworm to the United States after sixty years serves as a reminder that disease and pest control require continuous vigilance.

Even after successful eradication, biological threats can re-emerge when conditions allow.

The case also demonstrates how interconnected modern agriculture has become.

A parasite expanding through Central America and Mexico can eventually affect ranches in Texas.

For agricultural authorities, the goal is clear:

Contain the outbreak quickly and prevent the parasite from re-establishing itself in the United States.

Conclusion

The confirmation of a New World Screwworm infestation in a Texas calf marks the first U.S. case since 1966 and has triggered an aggressive containment effort by agricultural authorities.

The flesh-eating parasite, which feeds on living tissue and can cause severe damage to livestock, was once eradicated from the country through an innovative sterile-fly program.

Now, after decades of absence, officials are once again deploying that strategy to prevent a larger outbreak.

While risks to humans remain low and there is no food safety concern, the discovery is a significant development for the livestock industry.

Whether this remains an isolated incident or becomes a larger agricultural challenge will depend on how successfully containment measures work in the weeks and months ahead.