New World Screwworm & Your Dog
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New World screwworm is a parasitic fly whose larvae infest the wounds of living animals, including dogs, and it has re-emerged as a concern in parts of the Americas. Any wound crawling with maggots is a veterinary emergency. Keep wounds clean and covered, check pets carefully after travel, and follow current dog-travel and import rules from USDA APHIS.
What is New World screwworm?
New World screwworm is the larval (maggot) stage of a specific fly, Cochliomyia hominivorax. Unlike ordinary maggots that feed on dead tissue, screwworm larvae burrow into and feed on the living flesh of warm-blooded animals, enlarging the wound as they grow.
The fly is drawn to open wounds and to moist areas like the nose, ears, and around the eyes, and even small cuts, tick bites, or surgical sites can attract it. After years of control in the U.S., screwworm has re-emerged in parts of Central America and Mexico, prompting heightened surveillance and stricter animal-movement rules. Because the situation and affected areas evolve, check USDA APHIS for the current status.
What wound signs should I check my dog for?
Screwworm infestation (a type of myiasis) tends to look and progress differently from a normal scrape. Watch for:
- A wound that seems to grow larger or deeper rather than healing
- Visible maggots in a wound, sometimes burrowed in so their heads point down
- A foul odor and bloody or serous discharge
- Pain, irritation, licking or biting at the site, and restlessness
- Wounds around the nose, ears, eyes, genitals, or navel (in young animals)
A wound with maggots is a true emergency, see your vet immediately. Don't try to fully treat it yourself; screwworm cases are also reportable, and your vet knows the required steps.
How do I protect my dog and prevent infestation?
Prevention centers on wound care and vigilance:
- Treat wounds promptly: clean even small cuts, tick-bite sores, and surgical sites, and keep them covered or protected when possible.
- Inspect your dog regularly, especially after time outdoors or travel to affected regions, checking ears, nose, and skin folds.
- Keep up parasite prevention and control flies around your animals.
- Seek prompt care for any non-healing or worsening wound.
Logging wounds, when they appeared, photos, and how they're healing, in Tavi helps you notice quickly if something isn't healing as it should, and gives your vet a clear timeline.
What are the dog-travel rules I should know?
Because screwworm spreads through the movement of infested animals, authorities have tightened inspection and import requirements for pets and livestock crossing certain borders, and these rules can change as the situation develops.
If you're traveling with your dog to or from affected areas, check the current requirements before you go through USDA APHIS and, for international trips, the destination country's rules and your veterinarian. You may need a health certificate and a wound inspection. Have your dog examined and any wounds treated before travel, and report any suspicious wound to a veterinarian right away, both for your dog's sake and to help prevent spread.
Frequently asked questions
Is New World screwworm dangerous to dogs?
Yes. Screwworm larvae feed on living tissue and can cause rapidly worsening, painful wounds that, if untreated, may lead to severe infection or death. Any wound containing maggots is a veterinary emergency. Prompt treatment usually resolves it, so the key is catching it early and getting your dog to a vet immediately.
What should I do if I find maggots in my dog's wound?
Treat it as an emergency and contact your veterinarian right away rather than attempting full treatment at home. Screwworm is a reportable condition, and your vet will remove the larvae properly, treat the wound, and follow required reporting steps. Keep your dog calm and prevent further licking or contamination on the way to the clinic.
Can screwworm affect people?
Screwworm can infest humans as well as animals, typically through open wounds, though it's uncommon where surveillance is strong. The same principles apply: keep wounds clean and covered and seek medical care for any wound with maggots. If your pet is affected, follow your vet's and public-health guidance and practice good hygiene.
Do I need special paperwork to travel with my dog?
Possibly. Movement rules and inspections have been tightened around affected regions and can change quickly, so check USDA APHIS and your destination's current requirements before traveling. You may need a health certificate and a wound check. Ask your veterinarian well ahead of your trip so there's time to complete any required exams or documents.
Tavi's guides are informational and not a substitute for professional veterinary advice, diagnosis or treatment. When in doubt, call your veterinarian. Sources: USDA Animal and Plant Health Inspection Service (APHIS); American Veterinary Medical Association (AVMA); Merck Veterinary Manual; Centers for Disease Control and Prevention (CDC)
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