New World screwworm (NWS) is a devastating pest. It can cause serious, often deadly damage to animals and people in areas where the pest spreads. While NWS is present in parts of South America—where infections in animals and people continue to occur—it was eradicated from the United States decades ago. In recent years, NWS has moved northward through Central America and Mexico.
USDA is leading an aggressive national, One Health response to keep NWS out of our country.
Thanks to strong surveillance and response programs, the current risk to livestock, other animals, and people in the United States remains very low. Ongoing surveillance in animals shows no evidence of NWS in the United States.
Stopping the Spread
U.S. Readiness
Planning and preparing for an outbreak of NWS is essential to protect public health, animal health, agriculture, the environment, our food supply, and the economy.
With the support of industry, State, and Tribal partners, the United States remains vigilant against and fully prepared for possible screwworm incursions. As part of our five-pronged plan to defeat screwworm, we are supporting robust response activities in Mexico and Central America to push the pest back, and we have teams in place along the U.S. border to bolster our defenses and stay ahead of it. If screwworm crosses into the United States, we are ready to act quickly and aggressively to eliminate it.
Mass production and targeted dispersal of sterile flies remain critical components of our effective response.
Sterile flies are one of the most important tools we have for eradicating screwworm. USDA is investing heavily in new and existing sterile fly infrastructure to ramp up production and expand our domestic response capacity.
With these investments, production will approach approximately 500 million sterile flies per week—the same amount we used to eradicate NWS from the United States decades ago.
Track Status of Sterile Fly Production and Dispersal Facilities
Screwworm is not currently present in the United States—and we intend to keep it that way.
USDA has intensive surveillance and monitoring systems in place along the U.S.-Mexico border to detect screwworm. We also have strict trapping, surveillance, and movement protocols established in Mexico, and we work closely with our counterparts there to ensure the protocols are followed.
Across the Federal Government, we're driving innovation to win the fight against screwworm.
Science and collaboration are critical to our success. USDA has committed up to $100 million toward breakthrough technologies through the NWS Grand Challenge, which will solicit new ideas to help combat the pest. We're also pursuing extensive research to bolster our response strategies and ensure we have all the tools we need to detect, control, and eliminate this pest.
The U.S. Government is using all resources at our disposal to stop screwworm.
USDA has established a dedicated New World Screwworm Directorate within APHIS focused on coordinating and implementing the Secretary’s plans. We are collaborating closely with the U.S. Centers for Disease Control and Prevention, U.S. Department of the Interior, and numerous other agencies to ensure a unified Federal response.
What You Need To Know
Producers
- New World Screwworm | USDA
- NWS Photo Gallery | USDA
- New World Screwworm Story Map | USDA
Recorded Webinars
- Webinar for Animal Industry | USDA
Veterinarians
Animal Health Officials
- Emergency Management: New World Screwworm | USDA
- Standard Operating Procedure for Possible Detections of NWS in Animals | USDA
- Foreign Animal Disease Investigation Guide: New World Screwworm | USDA
- New World Screwworm: Information for Veterinarians | FDA
- New World Screwworm: Be Aware and Prepare (factsheet) | USDA
Recorded Webinars and Training
Wildlife Professionals
Healthcare Providers
Public Health Officials
- CDC - DPDx - New World Screwworm
- Laboratory Diagnosis of New World Screwworm (en Español)
- Telediagnosis of New World Screwworm
- Clinical Overview of New World Screwworm (en Español)
- Interim Considerations for Advanced Readiness and Preparedness for New World Screwworm (NWS) Infestations in Humans (available on 1CDC Data Platform (1CDP), must register to access)
Clinical or Diagnostic Assistance
- For clinical inquiries and patient management-related questions, contact parasites@cdc.gov or 404-718-4745. Direct after-hours inquiries to CDC’s Emergency Operations Center at 770-488-7100.
- For diagnostic assistance for suspected human cases, contact dpdx@cdc.gov.
Drug Manufacturers
Travelers
New World screwworm (NWS) myiasis is a serious parasitic disease that can affect all warmblooded animals, including people. Recently, cases of NWS myasis have been reported in countries where it had previously been eliminated, including Belize, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, and Panama. Travel to or from NWS-affected countries—particularly areas with active animal or human cases—can significantly increase the risk of infestation.
Human Health
People traveling to NWS-affected countries should:
- Clean and cover wounds.
- Avoid bug bites by using insect repellent and wearing loose-fitting, long-sleeved shirts and pants, socks, and hats.
- Sleep in a room with screened windows, or under a bed net, or inside a screened tent.
- Avoid spending time where livestock or other infested animals are located.
For more information on specific locations, visit CDC's Travelers’ Health website.
Traveling With Pets or Service Animals
To prevent the spread of NWS into the United States, pets and service animals arriving from NWS-affected countries must meet specific USDA and CDC import requirements:
Pet Owners
- New World Screwworm | USDA
Traveling Internationally With Pets or Service Animals
To prevent the spread of NWS into the United States, pets and service animals arriving from NWS-affected countries must meet specific USDA and CDC import requirements:
Hunters
- New World Screwworm | USDA
- New World Screwworm: A Threat to Wildlife (Information for Hunters) (en Español (1010.51 KB)) | USDA
- New World Screwworm Story Map | USDA
- NWS Photo Gallery | USDA
General Public
Report Suspected Cases of Screwworm
Contact your veterinarian right away if you see any suspicious wounds, maggots, or infestations in your animals or herd. Animal health professionals report suspected cases to the State animal health official and APHIS Area Veterinarian in Charge.
Contact your healthcare provider if you think you may have screwworm. Healthcare providers report suspected cases to the local or State health department.