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Flesh-eating parasite drives state of emergency in Florida

Emergency rules laid out after screwworm discovered in U.S.; no detections in Florida yet

ORLANDO, Fla. – After being detected in the U.S. for the first time in years last week, the New World Screwworm (NWS) has sparked even more emergency rules in Florida.

In a release this week, state officials said that the NWS has been detected in Texas and New Mexico, putting the spread even closer to the Sunshine State.

Gov. Ron DeSantis originally declared a state of emergency back in February over severe winter weather impacting the agricultural industry in Florida, and that declaration was extended on Thursday thanks to the NWS reaching the U.S.

In response to the threat, Agriculture Commissioner Wilton Simpson issued an Emergency Rule last week to prevent people from bringing warm-blooded animals into Florida from designated infestation zones and “high-risk areas.”

(Left) New World Screwworms; (Right) Blowflies were sterilized in the 1950s to help eradicate screwworm infestations in Florida (Florida Department of Agriculture and Consumer Services/Florida State Archives)

But on Wednesday, Simpson expanded the emergency rule, prohibiting rescue dogs and cats from entering Florida if they came from states with confirmed NWS detections. He also provided the following statement:

“New World Screwworm remains an ever-changing situation, and Florida’s response will continue to evolve as the facts on the ground evolve. We will respond based on facts, not fear.

But we will also continue to be the most aggressive state in the nation when it comes to protecting our livestock, pets, wildlife, people, and agricultural economy from this threat.

As additional detections have been confirmed in Texas and New Mexico, we are strengthening what are already some of the strongest protections in the country to keep Florida prepared and protected.”

Florida Commissioner of Agriculture Wilton Simpson

WHAT ARE NEW WORLD SCREWWORMS?

Per experts, the NWS are maggots that often enter animals through open wounds, feeding on an animal’s living flesh. As a result, infestations can be fatal if not treated.

“The New World Screwworm — a destructive parasite that targets warm-blooded animals — was eradicated from the U.S. more than four decades ago," state officials announced. “Its return would pose a serious threat to livestock, wildlife, and domestic animals, particularly in states like Florida with warm climates and abundant animal populations.”

Experts state that screwworm eggs are deposited in a “shingle-like manner” at the edges of superficial wounds, with larvae feeding by burrowing into the wound like a screw — hence the name.

An illustration depicting a larvae infestation, showing how the "screwworm" burrows into its host (U.S. Department of Agriculture)

While the NWS had been present in the southwestern U.S. since at least 1842, it was first documented as a major problem in 1933 after shipments of infested animals came in from the region.

At the time, the federal government and the state of Florida began developing tactics to deal with the threat, such as education programs, special insecticides, and radiation to sterilize the insects.

450 sterile screwworm pupae in a typical paper box "bomb" to be dropped on a cattle ranch by plane in 1958 — just one of the methods to fight back against New World Screwworm infestations in Florida (Florida State Archives (Public Domain))

But in the meantime, producers lost out on tens of millions of dollars each year as the NWS ravaged livestock, data shows.

Eventually, the U.S. and Mexico worked together to push these infestations down to the southern borders of Mexico in 1986.

[RELATED: Millions of bioengineered mosquitoes may soon be released into Florida]

There was a brief reemergence in the Florida Keys affecting the endangered Key deer back in 2016, though the outbreak was ultimately eradicated.

However, Florida officials said that infestations have been spreading north from Panama since 2023, culminating in the discovery of NWS in a bovine in South Texas this week.

WHAT ARE THE NEW EMERGENCY RULES?

To prevent the NWS from infiltrating Florida again, Simpson’s emergency rule imposes temporary restrictions on the importation of warm-blooded animals originating from certain high-risk and infested areas.

The latest guidelines are as follows:

  • HIGH-RISK AREAS
    • All warm-blooded animals originating from a high-risk area and entering Florida must be accompanied by an Official Certificate of Veterinary Inspection (OCVI), valid for five days from the date of inspection, documenting that all animals listed have been inspected and found free of contagious and infectious diseases and pests, including NWS.
    • The OCVI must include the statement: “All animals listed on the OCVI have been inspected and are free from screwworm larvae infestation.”
  • COUNTIES WITH CONFIRMED NWS DETECTIONS AND SURROUNDING COUNTIES
  • RESCUE AND SHELTER ANIMALS
    • Rescue dogs, rescue cats, shelter dogs and shelter cats originating from states with confirmed NWS detections are prohibited from entering Florida until further notice.

Federal officials said that the USDA and Texas are implementing quarantines as necessary and working to release sterile NWS flies to fight potential population growth.

Meanwhile, signs of screwworm infestation in animals include the following symptoms:

  • Wounds in living animals infested with maggots
  • Blood-tinged discharge from the infested wounds
  • Foul odor
  • Discomfort
  • Depressed/no eating
  • Decreased milk production
  • Seclusion from rest of herd or flock

If you come across a suspected case of screwworms or have questions about potential infestations, you can call the FDACS at (850) 410-0900 or click here.


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