New World Screwworm in Horses: What to Know
Animal Care Team
Outbreak
The recent detection of New World Screwworm (NWS) in the United States has prompted renewed attention across the equine community. While this parasite has historically been controlled through coordinated programs, awareness and early response remain essential in protecting horses and limiting spread and Team Absorbine wanted to make sure horse owners are informed.
Description
NWS is a type of fly whose larvae can infest open wounds or moist areas of the skin. Unlike common flies that feed on surface debris, these larvae can affect healthy tissue, making prompt recognition and care especially important. For horse owners, this reinforces the role of routine observation and consistent wound management as part of daily care.
Identification
What do the flies look like? Adult New World Screwworm flies are close to the size of a common housefly or slightly larger, and have three distinct traits:
- Possibly the easiest identifying feature: large, bright orange eyes
- A metallic blue or green body
- Three dark, vertical stripes along the back (the thorax)
Take Action
The most important first step if NWS is suspected is immediate communication with a veterinarian and appropriate state animal health officials. Early reporting helps guide a coordinated response and reduces the risk of wider impact. It is not something to manage independently or delay.
Prevention
From a preventive standpoint, maintaining a clean environment and minimizing opportunities for flies to access wounds are key. Regular grooming, inspecting for cuts or skin irritation, and addressing even minor wounds promptly can help reduce risk. Using a proper first-aid wound care approach designed to support cleanliness and healing can be part of that routine. For horses routinely exposed to insects, fly control strategies such as environmental management and the use of EPA registered fly control products labeled for nuisance flies can support overall insect management.
It’s important to understand that prevention and early support are different from treatment of an active infestation. If larvae are present, veterinary care is required. Your veterinarian can guide next steps, including appropriate interventions and monitoring.
Staying informed, maintaining routine care practices, and acting quickly when concerns arise can help horse owners navigate emerging risks like NWS with confidence and clarity.
CDC Link:
https://www.cdc.gov/new-world-screwworm/about/index.html
