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After a case of New World screwworm was found this month in a dog living in New Mexico, a veterinarian in the state reached out to the VIN News Service with a concern – not about the parasite, per se, but about how new restrictions on animal travel might catch some pet owners unawares.

"I'm worried people are going to get blindsided flying with their animals to other states!" wrote Dr. Nicholas Hopkins, a practitioner in Albuquerque.

The confirmed arrival of screwworm in the United States in early June has resulted in restricted animal movement between states and from affected areas. The confirmed detections — 20 total, in cattle, sheep, goats and a dog — have occurred in nine Texas counties and one in New Mexico. As such, Texas and New Mexico state officials have placed strict rules on animal travel from "infested zones," a space of 20 kilometers (12.5 miles) in all directions from the site of detection. Other states, wanting to keep the parasite out, have implemented their own safeguards, as well.

The adult screwworm fly typically has a flight radius of about six to 12 miles. The main way the pest gets around, however, is not by wing but by host. Its territory expands when an animal carrying screwworm eggs or larvae in a skin break or wound moves from where it was infested.

The movement might be by the host's volition, as happens with free-roaming wildlife. Or it results from human activity, such as a pet owner taking their dog on a summer road trip, or livestock transported over great distances — often across state lines — as part of the process of raising them for eventual slaughter.

Controlling disease and pests during ordinary animal transport is something states have been regulating for decades, and veterinarians play a key role. Veterinarians have the option to pursue accreditation by the U.S. Department of Agriculture, which gives them the authority to write travel certificates for international or interstate travel, called Certificates of Veterinary Inspection. (For livestock shows and competitions, such certificates might be needed for intrastate travel, as well.) Requirements for livestock and pets vary by state.

Veterinarians examine the animal or animals and, if they are healthy, certify that they are free from relevant diseases. The health certificate permits the animal to travel within a specified number of days.

According to the USDA, 67,569 U.S. veterinarians are accredited. About half of them are authorized to write health certificates for all animal species. The other half is authorized to write health certificates only for dogs, cats and select other species.

The current screwworm travel restrictions build upon this existing system but with several key differences.

The Texas Animal Health Commission (TAHC) has established nine infested zones around the recently detected cases. Livestock may not be moved outside of the infested zones without permission from the commission. 

To obtain permission, livestock, and in some cases, companion animals, must be inspected and granted a movement certificate by a "NWS Certified Inspector." To become an inspector, a person must have a relevant background — as a veterinarian, veterinary technician, livestock deputy, animal control officer or other career approved by the TAHC — and have completed a four-hour online training by the TAHC and Texas A&M AgriLife. The candidate must score 94% or higher on a final exam.

Texas veterinarians who are USDA-accredited are automatically qualified to conduct screwworm inspections without extra training. However, screwworm movement certificates in infested zones are distinct from the certificate of veterinary inspection that USDA-accredited veterinarians write under normal circumstances for animals leaving the state.

Multiple animals can be listed on a single screwworm movement certificate if the inspection is completed at the same time, TAHC told VIN News in an email, as long as they're the same species.

"If the premises has 10 cows, five sheep, and two pigs, there would be three certificates," an agency representative wrote, by way of example.

New Mexico has implemented similar restrictions for its one infested zone. While the single case of screwworm in New Mexico has been deemed inactive by the USDA, as has one in Texas, both states nevertheless require that animals being moved outside of the infested zone be inspected by an authority. In New Mexico's case, this is the New Mexico Livestock Board. 

If an animal is moving from a Texas or New Mexico infested zone to another state, it might need two certificates — a screwworm movement certificate and a certificate of veterinary inspection required by the destination. The requirements vary, depending on the destination state.

For example, Louisiana, which neighbors Texas to the east, requires that all animals from screwworm-affected states have an official certificate of veterinary inspection dated no more than seven days before the animal enters Louisiana, according to an order issued on June 5 by the state veterinarian, Dr. Daniel Myrick.

Those traveling with animals that originate from or travel through an infested zone have further requirements to meet. In addition to following their own state's transport rules, they must obtain a permit from the Louisiana Department of Agriculture and Forestry's Office of Animal Health and Food Safety, as well as a health certificate that states, "All animals were individually inspected and found free of evidence of NWS infestation."

VIN News confirmed that the following states have established screwworm-specific rules for livestock and/or pets: Alabama, Colorado, Florida, Georgia, Idaho, Indiana, Michigan, Montana, New York, North Carolina, Oklahoma, Tennessee, Washington and West Virginia. While some of the orders cite possible penalties for violation, none appears to specify how the rules will be enforced.

The list is not necessarily comprehensive, and more states may enact animal entry requirements in the days ahead. Anyone heading out of state with an animal from a screwworm-affected state should check for travel orders in their destination state or states. Such orders typically are issued by a jurisdiction's state veterinarian or Department of Agriculture.