For decades, New World screwworms were considered a problem of the past in the United States. However, recent detections in the Southwest have brought renewed attention to this dangerous parasite and the risks it poses to livestock, wildlife, and household pets. While the average dog owner in Colorado is unlikely to encounter a case, understanding the threat and knowing what warning signs to watch for can help protect your canine companion.
The New World screwworm is not actually a worm at all. It is the larval stage of a fly known as Cochliomyia hominivorax. Unlike many fly larvae that feed on dead tissue, New World screwworm larvae burrow into and consume healthy, living tissue. Female flies are attracted to open wounds, cuts, scratches, surgical sites, tick bites, and other skin openings where they lay their eggs. Once the eggs hatch, the larvae begin feeding on the surrounding tissue, causing extensive damage if left untreated.
How New World Screwworms Affect Dogs
Recent cases have confirmed that dogs can become infected. Although the overall risk remains relatively low for most pet owners, veterinary experts encourage vigilance, particularly for dogs that spend significant time outdoors or frequently come into contact with livestock, wildlife, or unmanaged animal populations.
One of the challenges with screwworm infestations is that they often begin with a wound that may seem minor. Pet owners should regularly inspect their dogs for cuts, scrapes, insect bites, and other skin injuries. Warning signs can include wounds that fail to heal, swelling, drainage, a foul odor, excessive licking or chewing at a specific area, lethargy, loss of appetite, and visible larvae within a wound. Because the larvae continue to burrow deeper into living tissue, infections can worsen rapidly.
The severity of an infestation depends on how quickly it is identified and treated. Left unchecked, the larvae can cause significant tissue damage and create secondary infections that further complicate recovery. This is why routine health checks and prompt veterinary care are so important, especially for dogs that spend time outdoors in rural or agricultural environments.
Prevention and When to Contact Your Veterinarian
Prevention begins with good pet care. Regularly checking your dog for injuries, promptly cleaning and treating wounds, and keeping up with routine parasite prevention products can all help reduce risk. Veterinary experts have noted that some monthly flea and tick preventatives may also provide protection against screwworm larvae. Dogs that spend time on ranches, farms, or rural properties should receive especially thorough inspections after outdoor activities.
If you suspect a screwworm infestation, immediate veterinary attention is critical. Experts strongly advise against attempting to remove larvae or treat the wound at home. A veterinarian can properly remove the larvae, clean and disinfect the wound, administer appropriate medications, and determine whether additional treatment is needed. Early intervention can dramatically improve outcomes and help prevent more serious complications.
At Peak Legacy Ranch, we understand the importance of animal health and responsible stewardship. While New World screwworm remains uncommon in Colorado, staying informed is one of the best ways to protect the dogs that are part of our families, ranches, and outdoor lifestyles. By monitoring wounds, maintaining preventative care, and acting quickly when something seems wrong, pet owners can help ensure their dogs stay healthy and safe.
