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Idaho adds requirements for animal entry in response to U.S. New World screwworm cases

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Idaho adds requirements for animal entry in response to U.S. New World screwworm cases

Jun 10, 2026 | 5:50 pm ET
By Abigail Gerstein
Idaho restricts animal entry in response to U.S. New World screwworm cases
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Idaho agriculture officials declared stricter restrictions for animal entry after New World screwworm cases were reported in the U.S. last week. (Photo by Preston Keres/USDA)

The Idaho State Department of Agriculture instated additional state entry requirements for animals on Wednesday following detections of New World screwworm — a flesh eating parasite — in Texas and New Mexico.

The parasite, first confirmed in the U.S. on June 3, would pose a serious threat to Idaho’s livestock industry, should it spread to the state. The screwworm’s larvae burrow into, and feed on, the living tissue of warm-blooded animals, with the potential to cause severe wounds, pain and bleeding.

The agriculture department’s Wednesday administrative order requires a Certificate of Veterinary Inspection granted, at most, five days before arrival for all warm-blooded animals entering Idaho from states with New World screwworm infestations.

For animals arriving from a designated screwworm-infested zone, the state agriculture department has mandated that a copy of the movement permit from the state-of-origin allowing the animal to depart must be presented. As of Wednesday, the U.S. Department of Agriculture has only declared screwworm-infested zones in southern Texas.

State officials are also encouraging Idahoans to refrain from taking their pets to states with New World screwworm cases to help mitigate the spread of the disease.

“Dogs and cats are just as susceptible to the pest as livestock, but pet owners may be less aware of the importance of thoroughly inspecting their pets for fly larvae that are very small and easy to miss,” said Scott Leibsle, Idaho state veterinarian. “Owners who do decide to travel with their pets to states affected by NWS will be required to get a health certificate, from a veterinarian in that state, within 5 days of their return to Idaho.”

Idaho Department of Agriculture Director Chanel Tewalt
Chanel Tewalt serves as the director of the Idaho Department of Agriculture. (Photo courtesy of Idaho State Department of Agriculture)

Spurred by significant losses of cattle to the screwworm, the USDA began efforts to combat the parasite in the 1950s and achieved full eradication in 1986.

Cases recurred in Florida in 2016, but the screwworm was dispelled by early 2017.

The consequences of a outbreak of the New World screwworm among cattle is especially serious for Idaho, as cattle and dairy production are the largest two sectors of the state’s agriculture industry.

“Idaho has been preparing for the possibility of New World screwworm reaching the United States, and we are well-positioned to respond,” said Chanel Tewalt, the state’s Department of Agriculture director. “We are coordinating closely with USDA officials and our counterparts across the West.”