Important: Contact a Veterinarian Right Away for Suspected Screwworm
New World screwworm is a reportable disease in the US. If you think your pet, horse, or livestock may have screwworm, treat it as urgent and contact your veterinarian immediately.*
The risk to most owned animals remains low, but early detection matters.
Thrive Pet Healthcare continues to monitor updates from veterinary and animal health officials. We will update this page if there are new developments that may affect pet, horse, or livestock owners.
What Is New World Screwworm Now?
New World screwworm is a type of fly whose larvae can live in wounds or body openings in warm-blooded animals. Animals that may be affected include:
Cats
Cattle
Dogs
Goats
Horses
Sheep
Wildlife
Other livestock
Rarely, New World screwworm can also affect people.
Why Is New World Screwworm a Concern?
New World screwworm was eliminated from the US decades ago. In recent years, it has re-emerged after breaking through a long-standing containment barrier in Central America in 2023 and moving north. Since then, cases have increased across Central America and Mexico. Limited detections in the southern US have raised concerns among veterinarians and animal health officials. Because this parasite can cause serious wounds and illness, early detection and reporting are important.
Potential Signs of New World Screwworm Infection in Animals
Contact a veterinarian right away if you notice any of these signs:
A bad smell coming from a wound
Drainage, bleeding, or swelling
Head shaking, especially if the ears are affected
Low energy, loss of appetite, or behavior changes
Pain, licking, scratching, or chewing at one area
Visible maggots or larvae in or around a wound
Wound that is getting larger, deeper, or not healing
Even small wounds, scratches, tick bites, or surgical sites should be checked closely.
When to Call a Veterinarian
Call a veterinarian right away if your pet, horse or livestock has:
A wound that is getting worse
A wound that is not healing
A wound with a bad smell
Drainage, bleeding or swelling
Recent travel and a suspicious wound
Signs of pain
Visible maggots or larvae
Early care matters.
How to Lower Risk
Animal owners can help lower risk by:
Calling a veterinarian about wounds that are not healing
Checking animals closely after travel
Checking animals daily for wounds
Checking animal movement rules before travel
Keeping wounds clean and protected when possible
Reducing exposure to flies when possible
Staying current on veterinarian-recommended parasite prevention
Using veterinarian-recommended fly control when appropriate
What Not to Do
If you suspect screwworm:
Do not try to remove larvae yourself.
Do not try to treat a suspected case at home.
Do not ignore a wound with maggots, drainage, swelling, or a bad smell.
Do not move an animal with a suspicious wound unless a veterinarian or animal health official advises you to do so.
Do not stay silent if you suspect your pet has screwworm because this is a reportable disease, meaning that any cases must be reported to state health authorities.
A veterinarian should examine the animal and determine the right treatment plan.
What to Do If You See a Stray Animal, Wildlife, or Livestock with Symptoms
If you encounter a stray animal, wildlife, livestock, or an animal you do not own with a suspicious wound, do not touch the wound or try to treat the animal. Keep people, pets, and other animals away if you can do so safely. Contact local animal control, a veterinarian, or the appropriate state animal health agency for guidance.
Treatment for New World Screwworm
Treatment depends on the animal, the wound, and the species affected. A veterinarian should examine the animal and determine the right treatment plan. Treatment may include medication, wound care, and removal of larvae by a veterinarian. Do not attempt to treat suspected screwworm at home.
GUIDANCE FOR PET OWNERS
Dogs and cats may be at risk if they have open wounds, spend time outdoors, recently traveled, were recently rescued, or were transported from an affected area.
Areas to Check on Dogs and Cats
Check your pet’s skin and wounds daily. Pay close attention to:
Any wound, scratch, bite, tick bite, or surgical site
Ears
Eyes
Genital area
Mouth
Nose
Skin folds
Call your veterinarian right away if you see maggots or larvae, a bad smell, drainage, swelling, pain, or a wound that is getting worse.
Extra Prevention Tips for Pet Owners
Pet owners can also help by:
Checking pets closely after travel
Having recently rescued or transported pets examined if they have suspicious wounds
Keeping pets indoors or supervised outdoors in affected areas
Talking with their veterinarian before travel if their pet has an open wound
GUIDANCE FOR HORSE OWNERS
Horse owners should check horses daily for wounds, especially if horses travel for shows, events, breeding, or boarding.
Areas to Check on Horses
Pay close attention to:
Call a veterinarian right away if you notice larvae, drainage, swelling, a bad smell, pain, or a wound that is not healing.
Horse Travel Guidance
Horse owners who travel for shows, events, breeding, or boarding should check current animal movement requirements before traveling. Requirements may vary by state and may change as animal health officials respond to new developments.
GUIDANCE FOR LIVESTOCK OWNERS
Livestock owners should monitor animals closely, especially newborn animals and small ruminants.
Livestock Risks
Newborns may be at higher risk because the fresh umbilical cord can be a high-risk site for infection. Other areas to monitor include:
Males may also be at risk around the genital area. This area should be monitored closely because infection can worsen quickly.
Extra Prevention Tips for Livestock Owners
Livestock owners can also help by:
Calling a veterinarian before moving animals from an affected or restricted area
Keeping facilities and equipment free of sharp edges that may cause wounds
Monitoring newborn animals closely
Watching external identification device sites that penetrate the hide
FOR MORE INFORMATION
*This article is intended for educational purposes only and does not replace professional veterinary advice, diagnosis, or treatment. Always contact a veterinarian with questions about your pet’s health or if you suspect illness. Recommendations may vary based on your pet’s individual needs and location.
