07/06/2026
We’ve had several clients ask about the New World Screwworm (NWS), so we wanted to share some information to help everyone understand what to watch for. Since this parasite has been present in parts of Central and South America for many years, we’re using an educational image from one of those regions to show what an infestation can look like.
Image courtesy of Prof. Victor Lima, Federal University of Sergipe, Brazil.
The image shows lesions caused by New World Screwworm (Cochliomyia hominivorax) larvae developing in the abdominal region of a dog.
****How does an infestation happen?****
A female New World Screwworm fly is attracted to a fresh wound, even one as small as a tick bite, surgical incision, or minor scratch. She lays her eggs along the edge of the wound. Once the eggs hatch, the larvae begin feeding on living tissue—a key difference between New World Screwworms and the maggots we’re more familiar with, which typically feed on dead tissue.
Over the next 4 to 12 days, the larvae grow while burrowing deeper into the wound, causing it to become larger and more severe.
Once fully developed, the larvae leave the animal, burrow into the soil, and pupate. About a week later, adult flies emerge and continue the life cycle.
****What are the signs?****
Infested wounds often have:
* A wound that rapidly enlarges or deepens
* Bloody or watery discharge
* A strong, foul odor
* Pain and irritation
* Visible larvae within the wound
The odor and drainage may also attract other fly species, leading to secondary maggot infestations.
Early intervention is critical.
This post isn’t meant to cause alarm—it’s meant to help pet owners recognize the signs and seek veterinary care as early as possible. Prompt treatment can significantly reduce tissue damage and improve outcomes.
Please check your pets regularly, especially if they have any recent wounds, and contact your veterinarian immediately if you notice a wound that’s worsening quickly or suspect an infestation.
Remember: Unlike the “normal” maggots we commonly encounter, New World Screwworm larvae feed on healthy, living tissue, making rapid diagnosis and treatment essential.
