What vets need to know about New World screwworm (NWS)
New World screwworm (NWS) is a parasitic fly that causes serious disease (myiasis) in livestock, pets, wildlife, occasionally birds, and in rare cases, people. It is most often detected in cattle, swine, horses, small ruminants, and dogs. Although NWS was eradicated from the United States and Central America decades ago, it has resurged and was recently detected as far north as Mexico. In May, U.S. Secretary of Agriculture Brooke L. Rollins suspended live cattle, horse, and bison imports from Mexico through U.S. ports of entry along the southern border as an additional measure to protect U.S. agriculture.
As an accredited veterinarian, your vigilance in detecting and reporting possible infestations of NWS is critical to preventing an outbreak in the United States.
What to Look For
NWS flies are attracted to wounds and mucous membranes. Animals that have recently given birth, suffered an injury, or had a surgical procedure, such as dehorning or branding, are most vulnerable. Even tick bites can attract NWS flies. Look for:
Maggots in wounds or other body openings, such as the nose, ears, and genitalia or the navel of newborn animals
Wounds that have bloody discharge and foul odor
Wounds that become deeper and larger as the maggots grow and feed on living tissue
Animals that are showing signs of pain including depression, irritability, not eating, and isolating themselves from other animals or people
Immediately Report Signs of NWS
Immediately report any suspicious wounds, maggots, or infestations to your State Animal Health Official and U.S. Department of Agriculture (USDA) Area Veterinarian in Charge.
Please encourage your clients to report signs of NWS to you immediately. The earlier we identify NWS, the faster we can stop this devastating pest from spreading.
Resources for Accredited Veterinarians
For more information on what to look for and how to report any possible detections, check out these resources:
