CDC Declares Screwworm Emergency as Colorado Issues Restrictions and Federal Response Expands

Since Mexico suspended U.S. live animal imports on June 10 following confirmed New World Screwworm detections in Texas and New Mexico, the response has moved from agricultural to federal public health territory.

The CDC's Emergency Activation

The Centers for Disease Control and Prevention activated a formal emergency response to New World Screwworm on Thursday, June 11, according to The Hill and Bloomberg. The Department of Health and Human Services confirmed the activation. This is the first time in decades the parasitic fly has been detected in U.S. cattle.

The Department of Agriculture is leading the animal-side response, per The Hill's reporting. The CDC's activation signals the outbreak has crossed into human health territory. The agency's own website warns that if you see or feel maggots in or on a wound, contact a healthcare provider immediately.

New World Screwworm is a parasitic fly whose larvae burrow into living flesh. It primarily targets warm-blooded livestock, pets, and wildlife, but human infection, while uncommon, is possible.

Colorado Acts Ahead of Its Own Detection

Colorado has NOT reported a confirmed case. The Colorado Department of Agriculture implemented its emergency rule on June 10 as a proactive measure, according to the Denver Gazette, citing the parasite's presence in neighboring states.

The rule is specific. Any warm-blooded animal entering Colorado from an infested zone must arrive with a Certificate for Movement from the originating state's animal health official, a Certificate of Veterinary Inspection, and a veterinary inspection within five days prior to movement. Animals with open wounds must be treated with an authorized product within 14 days before moving, unless they're slaughter-bound. In that case they must be slaughtered within 72 hours of arrival.

Pet owners are also affected. Dogs and cats face additional inspection protocols within five days before entering Colorado. Entry permits must be requested from the Colorado State Veterinarian's Office at 303-869-9130 within 48 hours of the move.

No animal confirmed to have screwworm myiasis may enter Colorado at all.

The Colorado Department of Agriculture stated in its press release: "Vigilance in monitoring for myiasis is critical, and early detection is key."

What the Threat Actually Is

The Denver Gazette's coverage is specific on the human risk angle, which Bloomberg and The Hill's reporting did not prominently address. The CDC's own guidance, quoted by the Denver Gazette, makes clear the parasite can infect humans through open wounds. It's rare, but real.

The USDA and CDC have both emphasized the U.S. food supply remains safe. New World Screwworm does NOT pose a food safety risk, according to Colorado's emergency rule documentation.

The Strongest Counterpoint

A fair concern from ranchers, pet owners, and interstate livestock traders is that these movement restrictions—certificates, inspections, 48-hour entry permit windows—impose real costs on people and businesses in states where no case has been confirmed. Colorado's emergency rule treats the entire infested zone as a source of risk, which means anyone moving animals from Texas or New Mexico faces new bureaucratic hurdles even if their animals are healthy and unaffected. Critics of broad preemptive restrictions would argue the regulatory burden falls on the compliant while doing little to intercept genuinely negligent actors.

The historical record on screwworm is the counterweight: the U.S. eradicated this parasite decades ago through an aggressive sterile insect technique program. Its return, if unchecked, could cost the livestock industry billions. The 1950s-era outbreak caused catastrophic losses before eradication efforts succeeded. Early containment is precisely how you avoid the heavier intervention later.

Where Things Stand as of June 11

Four confirmed cases exist in Texas and New Mexico as of the prior reporting. The CDC emergency activation is now live. Colorado has implemented emergency movement rules. Mexico's livestock import suspension remains in place.

What is NOT yet clear: how widely the CDC's emergency response will extend into human surveillance protocols, whether other border or neighboring states will follow Colorado's preemptive restriction model, and whether the USDA's sterile fly release program—the method used in the original eradication campaign—has been formally reauthorized or expanded as part of the federal response. Bloomberg's reporting noted cases are increasing but did not specify current confirmed totals beyond the Texas and New Mexico detections. That number is the key variable to watch.