The Idaho State Department of Agriculture has issued an administrative order imposing stricter entry requirements for warm-blooded animals entering the state, following confirmed detections of New World screwworm in Texas and New Mexico.
The first confirmed U.S. case was reported on June 5 in Zavala County, Texas, marking an alarming development for livestock producers and pet owners across the country. New World screwworm — a parasitic fly whose larvae burrow into the living tissue of warm-blooded hosts — poses a serious threat to cattle, horses, goats, poultry, and companion animals such as dogs, cats, rabbits, and birds. In rare circumstances, the pest can also affect humans.
Idaho officials moved quickly to protect the state’s agricultural industry and animal populations by establishing a new layer of documentation requirements on top of existing importation rules.
What the New Order Requires
Under the administrative order, any warm-blooded animal moving into Idaho from a state that has been designated as a New World screwworm-infested zone must carry two documents: a Certificate of Veterinary Inspection issued no more than five days before the animal is moved, and a movement permit obtained from the state of origin.
Animals originating from a state where the pest has been detected, but located outside a formally designated infested zone, face a slightly less restrictive requirement — they still need a Certificate of Veterinary Inspection issued within the same five-day window, but are not required to obtain a movement permit.
All existing importation regulations under IDAPA 02.04.24, the state’s rules governing animal imports, remain in effect and are not replaced by the new order — only supplemented where the order applies.
New World screwworm is classified as a mandatory reportable disease, meaning any suspected case identified by a veterinarian or producer in Idaho must be reported to state animal health officials immediately.
State Officials Urge Caution for Livestock and Pet Owners
ISDA Director Chanel Tewalt said the state had been monitoring the pest’s potential spread northward. “Idaho has been preparing for the possibility of New World screwworm reaching the United States, and we are well-positioned to respond,” she said.
Idaho State Veterinarian Scott Leibsle specifically called on pet owners to think carefully before traveling with animals in affected areas. “ISPA is specifically urging pet owners to avoid traveling with their companion animals in states where NWS has been identified,” Leibsle said.
New World screwworm was eradicated from the United States decades ago through a sustained federal program using sterile insect releases, but the pest has persisted in parts of Central America and South America. Recent detections in Mexico and now Texas and New Mexico have put western and southwestern livestock states on alert.
For Idaho’s agricultural economy — anchored by cattle ranching, dairy operations, and diverse livestock production across Magic Valley and surrounding regions — an unchecked screwworm introduction could carry significant consequences. The insect’s larvae feed on the living flesh of host animals, causing severe wounds that can be fatal if untreated. Early detection and movement restrictions are considered the most effective tools for preventing the pest from spreading to new areas.
What Comes Next
Idaho producers and pet owners planning to bring animals into the state from Texas, New Mexico, or any other area where New World screwworm activity is identified should contact a licensed veterinarian well in advance to secure the required Certificate of Veterinary Inspection within the five-day movement window. Anyone who suspects a screwworm infestation in an Idaho animal is required by law to report the case to the Idaho State Department of Agriculture.
State officials indicated they will continue monitoring the situation closely and may adjust the administrative order as the geographic scope of the infestation changes. Producers and livestock owners are encouraged to check the ISDA’s official guidance for the most current list of designated infested zones before scheduling any animal movements across state lines.
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