General information
New World screwworm (NWS) is a devastating pest. When NWS fly larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal. NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people.
NWS flies are attracted to open wounds, including tick bites, where they lay hundreds of eggs. The eggs hatch into larvae, which feed on living tissue to complete their life cycle. Newborn animals, animals that have recently given birth, or animals that have suffered an injury are most vulnerable. The flies may also be attracted to antler bases after shedding and mucous membranes.
The pest has been detected in Mexico and is a serious threat to our country. State and Federal agencies are collaborating to protect wildlife, domestic animals, and people from NWS.
Why does NWS matter to hunters?
- Reduced game populations: Deer and other species are vulnerable to NWS infestation, which can reduce the number of fawns that survive and grow into adults. Untreated infested animals will die, leading to smaller herds, fewer tags, and more restrictive seasons.
- Poor animal condition, even with treatment: NWS can compromise meat quality, cause deformities on hides and antlers, and stunt growth and reduce antler development.
- Restricted movement and disrupted hunting: Wildlife management organizations could require additional physical check stations for game inspection. Additional surveillance or control activities in hunting areas could lead to closed hunting areas and less game. State and Federal agencies may restrict live animal, meat, or carcass transport across county, State, and international lines to prevent spread and protect livestock and wildlife.
What should you look for?
- Larvae (maggots) on live or very recently dead animals, because NWS feeds on living tissue.
- Larvae (maggots) in wounds or other body openings, such as the nose, ears, genitalia, and the navels of newborn animals.
- Wounds that have bloody discharge and foul odor.
- Animals that are in pain, lethargic, or aggravated.
- Animals that isolate themselves.
What should you do if you see signs of NWS?
- Call your local Wildlife Services office at 866-4USDA-WS (866-487-3297) as soon as possible.
- Immediately wash your hands and gear with soap and water.
- Record the location (using GPS if possible).
- Take photos of the wounds and larvae if possible.
- DO NOT eat, handle, or transport the animal or meat.
Protect animals and people!
Because NWS can spread quickly to new areas on infested animals, reporting signs of NWS is critical. Hunters and outdoor enthusiasts can be part of the first line of defense. We need your help to look out for this serious threat to U.S. agriculture, wildlife, and people. Even information about suspected cases of NWS (like pictures/videos from trail cameras) is helpful. Share this information with your organizations and communities to spread awareness!
How to protect yourself:
- Make sure all wounds are clean and completely covered.
- Use a U.S. Environmental Protection Agency-registered insect repellent. Use clothing and gear that has been treated with 0.5% permethrin.
- Avoid sleeping outdoors and protect sleeping accommodations with screens or bed nets.
- Check all harvested animals and yourself for larve (maggots) after hunting.
- If you see or feel maggots (larvae) in or on a wound or other area of your body, contact your healthcare
provider immediately.