Two More Texas Screwworm Infections Found in Animals Far Apart, USDA Says

The USDA confirmed on June 8, 2026, that two more New World Screwworm infections have been found in Texas animals — one in a calf in La Salle County and another in a dog in Andrews County. These cases are hundreds of miles apart, raising serious concerns about how widely this flesh-eating parasite may have already spread. The total confirmed case count now stands at four, and federal officials are racing to contain the outbreak before it devastates the U.S. cattle industry.

Key Takeaways

• The USDA confirmed four total New World Screwworm cases in Texas as of June 8, 2026, with infections spread across Zavala, La Salle, and Andrews counties.
• The geographic distance between cases — some hundreds of miles apart — signals a potentially wider spread than initially feared.
• New World Screwworms were eradicated from the U.S. in the 1960s using a sterile fly release program; that same strategy is being deployed again.
• The U.S. cattle herd is already at its smallest size in 75 years, making this outbreak especially dangerous for ranchers and beef prices.
• Canada has temporarily halted livestock imports from Texas in response to the outbreak.
• DOGE-driven federal budget cuts have weakened the USDA’s capacity to respond quickly to agricultural emergencies like this one.
• Humans can be infested by screwworms, particularly those with open wounds, though no human cases have been reported in the current outbreak.
• Ranchers should inspect animals daily, report suspicious wounds immediately, and contact their local veterinarian or USDA office at the first sign of infestation.

What Are Screwworms and How Dangerous Are They?

New World Screwworms (Cochliomyia hominivorax) are parasitic flies whose larvae feed on the living flesh of warm-blooded animals. They are not just dangerous — they can be lethal if left untreated.

The adult female fly lays eggs at the edge of an open wound, even a small scratch or tick bite. Within 12 to 24 hours, those eggs hatch into larvae. The maggots then burrow deeper into living tissue, feeding as they go. The name “screwworm” comes from the way the larvae drill into flesh in a corkscrew motion. A single untreated infestation can kill a large animal within days.

Key facts about screwworm danger:

• Larvae release enzymes that break down tissue, enlarging the wound rapidly
• Infested wounds attract more flies, compounding the infestation
• Animals can carry dozens to hundreds of larvae in a single wound
• Death can occur within 7 to 14 days without treatment
• The fly thrives in warm climates, making the Texas-Mexico border region especially vulnerable

This is not a minor pest problem. This is an agricultural emergency.

Can Screwworms Spread to Humans?

Yes, screwworms can infect humans, though it is uncommon. People with open wounds, compromised immune systems, or who spend significant time outdoors in affected areas face the highest risk.

No human cases have been reported in the current Texas outbreak. However, public health officials stress that anyone with an untreated wound in an affected area should seek medical attention promptly. Infants, elderly individuals, and people recovering from surgery are considered most vulnerable.

The condition in humans is called myiasis. It requires prompt medical treatment, typically the manual removal of larvae by a healthcare provider, sometimes combined with antiparasitic medications.

How Do Screwworms Infect Livestock?

Screwworm flies target any warm-blooded animal with an open wound. The infection process is fast and aggressive.

Here is how it unfolds:

1. An adult female screwworm fly detects the scent of blood or tissue fluid from a wound.
2. She lays a cluster of 10 to 400 eggs at the wound’s edge.
3. Eggs hatch within 12 to 24 hours.
4. Larvae burrow into living tissue and feed for 5 to 7 days.
5. Mature larvae drop to the ground, pupate in soil, and emerge as adult flies within 7 days.
6. The new adult flies repeat the cycle.

This rapid lifecycle — egg to adult in as few as 21 days — is what makes screwworms so difficult to contain once they establish a foothold. Even routine injuries like castration wounds, branding marks, or tick bites create entry points.

Where in Texas Have These Recent Infections Been Found?

The USDA confirmed the first New World Screwworm case on June 3, 2026, in a three-week-old calf in Zavala County, in south Texas near the Mexican border. A second case followed shortly after in another calf about 5.6 miles from the first.

Then, on June 8, 2026 — the same day the headline “Two more Texas screwworm infections found in animals far apart, USDA says” broke nationally — federal officials confirmed two additional cases: one in a calf in La Salle County and another in a dog in Andrews County.

Andrews County sits in far west Texas, near the New Mexico border. La Salle County is in south Texas. The distance between these new cases and the original Zavala County detections spans hundreds of miles. That geographic spread is what has alarmed both federal officials and ranchers statewide.

The USDA has established a 12-mile quarantine zone around the initial detection site and has increased surveillance across the region. But the wide spread of confirmed cases suggests containment will be far more complex than a localized response.

Are Some Animal Species More Vulnerable to Screwworms?

All warm-blooded animals are susceptible, but livestock — particularly cattle, sheep, goats, and deer — face the greatest risk because of their frequent exposure to wounds through normal ranching operations.

Most vulnerable animals include:

• Cattle: Especially calves, which have thinner skin and are more likely to sustain wounds during birth
• Sheep and goats: Shearing wounds and foot rot create easy entry points
• White-tailed deer: A major wildlife host that can spread the fly across wide geographic areas
• Dogs and other pets: The Andrews County case confirms that companion animals are not immune
• Horses and mules: Particularly at risk near the Mexican border

Wildlife hosts like deer are a serious concern because they move freely across quarantine zones, potentially carrying the fly far beyond controlled areas.

How Do Screwworms Differ from Other Livestock Parasites?

Most livestock parasites — like internal worms, lice, or ticks — are chronic problems that weaken animals over time. Screwworms are different because they kill quickly and attack from the outside.

The urgency with screwworms is unmatched. A rancher who misses a wound for three days may lose the animal.

What Happened During Previous Screwworm Outbreaks in Texas?

New World Screwworms were once a devastating and routine presence across the American South. Before eradication, the USDA estimated the parasite cost U.S. livestock producers hundreds of millions of dollars annually.

The breakthrough came in the 1950s when entomologist Edward Knipling developed the sterile insect technique. Scientists raised screwworm flies in large numbers, sterilized the males using radiation, and released them into the wild. Sterile males competed with fertile males for mating. Since females mate only once, a mating with a sterile male produces no offspring. Over time, the population collapsed.

By the late 1960s, New World Screwworms were eradicated from the continental United States. A barrier zone maintained in Central America has kept them out ever since — until now.

The current outbreak follows detections of screwworms in Mexico in late 2024. The fly’s northward movement was predictable. What was not acceptable was the federal government’s sluggish response to a known, approaching threat.

How Is the USDA Tracking and Responding to These Infections?

The USDA’s Animal and Plant Health Inspection Service (APHIS) is leading the federal response. Officials have confirmed they are deploying the same sterile fly release strategy that worked in the 1960s.

Current USDA response measures include:

• A 12-mile quarantine zone around the original Zavala County detection site
• Increased surveillance across south and west Texas
• Plans to release sterile male flies over affected areas
• Coordination with Texas state agricultural officials
• Enhanced border inspection protocols

The agency has stated it is confident in its ability to eradicate the pest again. But confidence alone does not substitute for resources. And that is where a serious problem begins.

How DOGE Cuts Undermined the Federal Response

Here is the uncomfortable truth that the Trump administration does not want to discuss: the federal government’s ability to respond to agricultural emergencies like this one has been deliberately weakened.

The Department of Government Efficiency — DOGE — pushed sweeping cuts to federal agencies in 2025, including significant reductions to USDA staffing and program budgets. APHIS, the very agency responsible for tracking and containing screwworms, saw personnel losses and budget constraints that have slowed its capacity to respond at the speed this outbreak demands.

Texas Agriculture Commissioner Sid Miller has publicly criticized the federal response as too slow. He has advocated for poison bait as a faster solution — a controversial approach that carries real risks to non-target species, including endangered wildlife. That Miller is even floating such an option signals how frustrated state officials are with Washington’s pace.

When you gut the agencies designed to protect farmers and then act surprised that a known threat crossed the border and spread hundreds of miles before being contained, that is not bad luck. That is the predictable consequence of bad policy.

The Trump administration has failed American farmers here. The U.S. cattle herd is already at its smallest size in 75 years. Beef prices are at record highs. And now, a parasite that was eradicated more than 60 years ago is back — partly because the federal infrastructure meant to keep it out was deliberately undermined.

How Quickly Can Screwworms Spread Between Animals?

Screwworms can spread rapidly, especially in warm weather. Adult flies can travel several miles on their own, and wildlife hosts like deer can carry infested wounds across much larger distances.

The fact that confirmed cases in the current outbreak are hundreds of miles apart — as noted in the USDA’s June 8 announcement that two more Texas screwworm infections were found in animals far apart — suggests the fly may have been present in Texas longer than the initial June 3 detection indicated.

Entomologist Edward Burgess has noted that increased surveillance may be revealing cases that were already there, rather than documenting a sudden rapid spread. Either way, the picture is troubling: the parasite is more widespread than anyone initially hoped.

What Treatment Options Exist for Screwworm Infections?

Treatment must begin immediately once an infestation is identified. Every hour matters.

Standard veterinary treatment protocol:

1. Restrain the animal safely
2. Clip hair or wool away from the wound
3. Manually remove all visible larvae using forceps
4. Flush the wound thoroughly with an approved insecticidal solution
5. Apply a wound treatment approved for screwworm control (such as coumaphos-based products)
6. Re-examine the wound every 24 to 48 hours for new larvae
7. Report the case immediately to the USDA and your state veterinarian

There is no vaccine for screwworm. Prevention and early detection are the only real defenses. Ranchers should conduct daily visual inspections of all animals, especially those with recent wounds.

How Do Farmers Protect Their Animals from Screwworm?

Prevention is the most powerful tool a rancher has. The USDA recommends a proactive approach, especially in affected counties.

Practical prevention steps for ranchers:

• Inspect all animals daily, paying close attention to wounds, navels on newborns, and areas around ears and eyes
• Schedule surgical procedures (castration, dehorning, branding) during cooler months when fly activity is lower
• Treat all wounds promptly with approved wound dressings
• Work with your veterinarian to establish a screwworm monitoring protocol
• Report any suspicious wound to your state veterinarian or USDA APHIS immediately
• Keep records of all animal health checks for regulatory purposes

If you are a rancher in Texas right now, daily checks are not optional. They are essential.

What Economic Impact Do Screwworm Infections Have on Ranchers?

The financial stakes could not be higher. Before eradication in the 1960s, screwworms caused losses estimated in the hundreds of millions of dollars annually across the U.S. livestock industry.

Today, the context is even more precarious. The U.S. cattle herd is at its smallest size in 75 years. Beef prices are already at record highs. Canada has temporarily halted livestock imports from Texas. If the outbreak spreads significantly, ranchers face:

• Direct livestock losses from animal deaths
• Increased veterinary costs for treatment and monitoring
• Potential loss of export markets
• Reduced herd values due to quarantine restrictions
• Higher operational costs for daily inspections and wound management

For small and mid-size ranching operations already operating on thin margins, even a modest outbreak could be financially devastating. This is not just a Texas problem. It is a national food security issue.

How Does the Sterile Fly Program Work — And Can It Succeed Again?

The sterile insect technique is one of the most successful pest eradication programs in agricultural history. It worked before, and the USDA believes it can work again.

Here is the process:

1. Screwworm flies are raised in large numbers at a USDA facility
2. Male pupae are exposed to low-level radiation, rendering them sterile
3. Sterile males are released by aircraft over affected areas — in the millions per week
4. Sterile males compete with wild fertile males for mating with females
5. Females that mate with sterile males produce no viable offspring
6. Over multiple generations, the wild population declines and collapses

The key is scale and speed. The program requires releasing enough sterile flies consistently over a wide enough area to overwhelm the wild population. That takes resources, logistics, and sustained federal commitment — all things that have been strained by recent budget cuts.

The USDA has stated it has invested heavily in tools to eliminate screwworms and is confident in its ability to eradicate the pest. But confidence must be backed by funding, staffing, and political will. All three are in shorter supply than they should be right now.

What Needs to Happen to Get Back on Track

The path forward is clear, even if the political will to walk it is not.

What federal and state officials must do:

• Restore USDA APHIS staffing and budget capacity immediately
• Accelerate the sterile fly release program with adequate scale and frequency
• Expand the quarantine zone as new cases are confirmed
• Increase cross-border coordination with Mexico on screwworm surveillance
• Provide direct financial support to ranchers affected by quarantine restrictions
• Establish a transparent, public-facing tracking system for confirmed cases

Congress must also hold the administration accountable for the staffing cuts that weakened the federal response infrastructure. When DOGE slashed agency budgets in the name of efficiency, it created real inefficiency — the kind measured in dead cattle and panicked ranchers.

This Is What Happens When You Defund Agricultural Protection

The story of two more Texas screwworm infections found in animals far apart is not just a pest control story. It is a story about what happens when a government decides that the agencies protecting farmers, food supplies, and public health are expendable.

New World Screwworms were beaten once before. American scientists and federal workers eradicated a devastating parasite through decades of careful, sustained, science-based effort. That victory was not an accident. It was the result of investment, expertise, and institutional commitment.

The Trump administration’s embrace of DOGE-driven cuts has put that legacy at risk. Ranchers in Texas are paying the price right now. And if this outbreak is not contained quickly, American consumers will feel it too — in beef prices, in export disruptions, and in the slow erosion of the agricultural security that working families depend on.

Here is what you can do:

• If you are a rancher or livestock owner in Texas, begin daily animal inspections today and contact your veterinarian immediately if you find a suspicious wound.
• If you see an animal with an unusual wound, report it to USDA APHIS at 1-800-414-8809.
• Contact your U.S. Representative and Senators and demand they restore USDA funding and hold the administration accountable for its slow response.
• Stay informed. Follow USDA APHIS updates at aphis.usda.gov and share accurate information with your community.

American farmers deserve a federal government that has their backs. Right now, too many of them are on their own.

Frequently Asked Questions

What is a New World Screwworm?
A New World Screwworm is a parasitic fly (Cochliomyia hominivorax) whose larvae feed on the living flesh of warm-blooded animals. The fly lays eggs in open wounds, and the hatched larvae burrow into tissue, causing severe injury or death if untreated.

How many screwworm cases have been confirmed in Texas in 2026?
As of June 8, 2026, the USDA has confirmed four cases: two calves in Zavala County, one calf in La Salle County, and one dog in Andrews County.

Are screwworms dangerous to humans?
Yes, screwworms can infect humans, a condition called myiasis. People with open wounds or weakened immune systems are most at risk. No human cases have been reported in the current Texas outbreak.

How were screwworms eradicated from the U.S. before?
The USDA used a sterile insect technique, releasing millions of radiation-sterilized male flies to compete with wild males. Females that mated with sterile males produced no offspring, causing the wild population to collapse. The U.S. was declared screwworm-free in the late 1960s.

Why are the new Texas cases hundreds of miles apart?
The geographic spread likely reflects a combination of fly movement, wildlife host travel, and possibly the parasite being present longer than initially detected. Increased surveillance is also revealing cases that may have existed before the first official confirmation.

What should ranchers do right now?
Ranchers should inspect all animals daily, treat any open wounds immediately with approved products, and report suspicious wounds to USDA APHIS at 1-800-414-8809 or their state veterinarian.

Has Canada stopped importing Texas livestock?
Yes. Canada temporarily halted livestock imports from Texas in response to the confirmed screwworm outbreak.

How did DOGE cuts affect the federal response?
DOGE-driven budget reductions in 2025 cut USDA staffing and program resources, including within APHIS — the agency responsible for tracking and containing screwworms. This weakened the federal government’s capacity to respond quickly to the outbreak.

What is the sterile fly release program?
It is a pest control method where screwworm flies are raised in captivity, male pupae are sterilized using radiation, and the sterile males are released by aircraft over affected areas. Sterile males mate with wild females, producing no viable offspring, which gradually collapses the wild population.

What is the economic risk of this outbreak?
The U.S. cattle herd is at its smallest size in 75 years and beef prices are at record highs. A significant screwworm outbreak could cause direct livestock losses, increased veterinary costs, export market disruptions, and financial hardship for ranchers already operating on thin margins.