State officials announce emergency rule to prevent spread of parasitic screwworm into Colorado

The New World Screwworm was recently found in Texas and New Mexico. Now, state officials have announced an emergency rule to prevent the spread of the parasite into Colorado.

According to the Centers for Disease Control and Prevention, New World Screwworms are a species of fly that feeds on the flesh and tissue of warm-blooded animals and people. The CDC warned that the maggots are particularly devastating to livestock health.

"NWS flies are attracted to wounds and body openings like the nose, eyes, ears, and mouth, where they lay eggs. The eggs hatch into maggots (larvae) that eat live tissue, causing a worsening, often painful and foul-smelling wound," the CDC said.

The insect is threatening the U.S. cattle industry for the first time since the 1960s. They were eliminated in the U.S. by introducing sterile male flies, but they have been moving north through Central America for the last few years.

Due to recent cases in Texas and New Mexico, the Colorado State Veterinarian proposed an emergency rule to control the spread into Colorado. The new rule states animals with NWS myiasis are not allowed to enter Colorado. Violations can result in orders to return animals to their place of origin or in the animals being quarantined at the place that received them. The Commissioner of Agriculture warned that violations could also result in legal action.

According to the Colorado Commissioner of Agriculture, the following restrictions are now in place:   

• Animals from an infested zone must enter Colorado only with approval and a Certificate for Movement from the state animal health official in the state of origin.
• Movement certificates must be submitted with a Certificate of Veterinary Inspection.
• Animals must be inspected by an authorized veterinarian/official within 5 days prior to movement.
• Animals with open wounds without myiasis must be treated with an authorized product within 14 days prior to movement. (Slaughter-bound animals are exempt from treatment but must be slaughtered within 72 hours.)
• An entry permit must be requested from the Colorado State Veterinarian's Office at (303) 869-9130 within 48 hours of movement.
• Upon arrival in Colorado, animals must be inspected by an authorized veterinarian or official.
• Standard interstate movement requirements, as listed through CDA's Animal Import Tool, must still be met.

Pet owners also need to follow inspection protocols for cats and dogs. Animals originating from states with NWS infestation zones must be inspected and examined for screwworm within 5 days before entering Colorado. Any animals with screwworm must be treated before they're allowed to be moved.

The Colorado State Veterinarian's Office says it's holding an informational webinar on Thursday to cover the new changes. The event is free to attend and open to the public. It begins at 6 p.m., and those who want to participate can register at ag.colorado.gov/events or directly via Zoom.