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At Corey’s Canine Corner we are dedicated to providing accurate, reliable, fact-based, science-based information for dogs and the people who love them. You’ll hear from veterinarians and other experts in animal health and wellness. Trusted by pet owners. Approved by veterinarians.
New World Screwworm: What Pet Owners Need to Know
- As New World Screwworm returns to the headlines, many pet owners are hearing the name for the first time and wondering whether they should be concerned.
- We spoke with Dr. Sheldon Rubin, a longtime Chicago veterinarian, former president of the Illinois Veterinary Medical Association, former president of the Chicago Veterinary Medical Association and former president of the American Heartworm Society. Dr. Rubin built one of Chicago's largest veterinary practices, helped establish one of the region's largest veterinary emergency and specialty hospitals and educated pet owners through national media appearances, including on the Oprah Winfrey show during her years in Chicago.
- Dr. Rubin wants people to understand what the parasite is, where it's currently found and why good veterinary care remains the best way to protect pets. "I don't want to put out some kind of red flag," said Dr. Rubin. "But I do want people to understand what we're dealing with."
- What Makes Screwworm Different?
- Despite its name, New World Screwworm isn't actually a worm. It's the larval stage of a fly that's slightly larger than a common housefly, with bright orange eyes and a metallic blue-green body.
- The real danger begins when a female fly finds an open wound. That wound can be something obvious, like a recent surgical incision, or as small as a tick bite or irritated skin caused by allergies. "It could be as small as a tick bite wound," Dr. Rubin says. "Or any wound at all."
- The fly lays hundreds of eggs around the wound. Within a few days, those eggs hatch into larvae. Unlike most fly larvae, which feed on dead tissue, screwworm larvae burrow into healthy tissue.
- "They begin to burrow like a screw into live tissue - not dead tissue, live tissue," Dr. Rubin explains. "That's what makes these so unique." As the larvae tunnel deeper, they continue feeding, causing severe tissue damage if they aren't treated promptly.
- Should Pet Owners Be Concerned?
- Although screwworm has generated national attention, Dr. Rubin says it's important to keep the current situation in perspective.
- At the time of our conversation (August 2026), confirmed U.S. cases were concentrated along the Texas-Mexico border, with one reported case in New Mexico. The parasite has also been present in Mexico, Central America and South America. For pet owners in Illinois and much of the country, the immediate risk remains low.
- "It's unlikely at this point that we would even have to worry about this up here in the Chicago area," Dr. Rubin says.
- The greatest concern is for livestock producers and for people traveling with pets into affected areas. Dogs recovering from surgery, pets with untreated wounds or animals with skin conditions may be more vulnerable if exposed to the flies.
- The good news is that screwworm is treatable when caught early. "If a wound is found on them, it can be treated," Dr. Rubin says. "It doesn't mean it's the end of the life for the animal."
- Dr. Rubin also wants pet owners to know that screwworm isn't something pets spread to one another. "Screwworm is not infectious between animal to animal, or animal to person," he explains. "These animals only get infected by the adult female fly laying eggs on a wound."
- Prevention Starts With Good Veterinary Care
- One of the reasons Dr. Rubin isn't overly alarmed is that prevention is already part of good veterinary medicine.
- Several monthly parasite preventives now offer protection against screwworm larvae while also protecting pets against much more common threats like fleas, ticks and heartworm disease.
- "This year so far has been a major tick year," Dr. Rubin says. He notes that veterinarians are seeing more tick-borne disease than ever before, even in urban areas where dogs may never leave the city. Heartworm also remains a significant concern across much of the country.
- "Heartworm is easy to prevent and very difficult to cure," Dr. Rubin says.
- Rather than focusing only on the newest parasite making headlines, Dr. Rubin encourages pet owners to think about year-round parasite prevention as part of their pet's overall healthcare.
- Your Veterinarian Is Your Best Resource
- Throughout the conversation, Dr. Rubin repeatedly returned to one simple message: every pet is different, and every prevention plan should be based on that individual animal's age, health, lifestyle and travel habits.
- "I think the bottom line here is we should be taking our pets to the veterinarian at least once a year," Dr. Rubin says. "And if your pet is older, it should go twice a year."
- Routine wellness visits give veterinarians the opportunity to recommend the right parasite prevention, identify health concerns early and answer questions before small problems become larger ones.
- As Dr. Rubin puts it, "I always say your veterinarian is your pet's second-best friend."
- Keeping the Risk in Perspective
- For most pet owners, New World screwworm is something to be aware of - not something to fear.
- Scientists are once again using the same sterile-fly program that successfully eliminated the parasite from the United States decades ago, and veterinarians continue to monitor new cases closely.
- In the meantime, the advice for pet owners hasn't changed. Keep wounds clean, use veterinarian-recommended parasite prevention, schedule regular wellness visits and talk with your veterinarian before traveling to areas where screwworm is present.
- As Dr. Rubin reminds pet owners, "If you have a pet, you have a responsibility for that pet."
- Whether the concern is screwworm, ticks, heartworm or another parasite, that responsibility begins with prevention and a trusted veterinary team.
- For more information watch our discussion with Dr. Rubin here Or visit:
- www.screwworm.org www.USDA.gov