Preparing for Potential Emergence of New World Screwworm in the U.S.
The USGS National Wildlife Health Center (NWHC) is supporting the Department of the Interior’s (DOI) preparedness planning for New World screwworm (NWS), a re-emerging parasitic disease that is spreading north from Central America.
What is New World Screwworm?
New World screwworm is a fly (Cochliomyia hominivorax) that lays its eggs in the wounds of living warm-blooded animals. Within 12-24 hours the eggs hatch into larvae (maggots) which burrow into the wound to feed, creating a larger wound and leading to illness and death if left untreated. The flies primarily affect livestock but can also infect people and wildlife.
New World screwworm was once native to the southern United States and Central America but was eradicated in the US in 1966 by the targeted release of sterilized male flies (sterile insect technique). Females only mate once in their lifetime, so mating with sterilized male flies results in unfertilized eggs which reduces the population over time.
However, starting in 2023, NWS detections in Panama began to increase and it has now reached south-central Mexico. New World screwworm has the potential to significantly impact agriculture and vulnerable wildlife species if it re-establishes in the U.S. The U.S. Fish and Wildlife Service National Wildlife Refuge System is urging DOI personnel in southern states, particularly those that border Mexico, to be on alert for NWS in wildlife.
What is NWHC doing for NWS?
Early detection and rapid response are critical to controlling the spread of the parasite. To help prepare for the possibility of NWS re-emergence in the U.S., NWHC is developing two products to inform decision-making: a wildlife-focused risk assessment and an annotated bibliography on potential impacts of this disease to North American wildlife.
The risk assessment is focused on providing partners the information needed to make decisions regarding surveillance strategies in wildlife and, ultimately, informing prevention and mitigation strategies. The annotated bibliography will summarize scientific reports of NWS in wildlife and will serve as a plain-language reference to help wildlife professionals, land managers, and policymakers quickly access key information. While this document does not replace the need to consult original studies for a deeper understanding, it is intended to provide a useful starting point for making informed decisions surrounding NWS management and response.
The NWHC is also available for consultation to help wildlife partners navigate this emerging threat in wildlife. If you have a question regarding NWS in wildlife, please contact our Epidemiology Team at NWHC-epi@usgs.gov.
For additional information about NWS myiasis (the disease caused by NWS), see:
Animal disease: New World Screwworm (USDA)
Human disease: Clinical Overview of New World Screwworm | New World Screwworm | CDC
The USGS National Wildlife Health Center (NWHC) is supporting the Department of the Interior’s (DOI) preparedness planning for New World screwworm (NWS), a re-emerging parasitic disease that is spreading north from Central America.
What is New World Screwworm?
New World screwworm is a fly (Cochliomyia hominivorax) that lays its eggs in the wounds of living warm-blooded animals. Within 12-24 hours the eggs hatch into larvae (maggots) which burrow into the wound to feed, creating a larger wound and leading to illness and death if left untreated. The flies primarily affect livestock but can also infect people and wildlife.
New World screwworm was once native to the southern United States and Central America but was eradicated in the US in 1966 by the targeted release of sterilized male flies (sterile insect technique). Females only mate once in their lifetime, so mating with sterilized male flies results in unfertilized eggs which reduces the population over time.
However, starting in 2023, NWS detections in Panama began to increase and it has now reached south-central Mexico. New World screwworm has the potential to significantly impact agriculture and vulnerable wildlife species if it re-establishes in the U.S. The U.S. Fish and Wildlife Service National Wildlife Refuge System is urging DOI personnel in southern states, particularly those that border Mexico, to be on alert for NWS in wildlife.
What is NWHC doing for NWS?
Early detection and rapid response are critical to controlling the spread of the parasite. To help prepare for the possibility of NWS re-emergence in the U.S., NWHC is developing two products to inform decision-making: a wildlife-focused risk assessment and an annotated bibliography on potential impacts of this disease to North American wildlife.
The risk assessment is focused on providing partners the information needed to make decisions regarding surveillance strategies in wildlife and, ultimately, informing prevention and mitigation strategies. The annotated bibliography will summarize scientific reports of NWS in wildlife and will serve as a plain-language reference to help wildlife professionals, land managers, and policymakers quickly access key information. While this document does not replace the need to consult original studies for a deeper understanding, it is intended to provide a useful starting point for making informed decisions surrounding NWS management and response.
The NWHC is also available for consultation to help wildlife partners navigate this emerging threat in wildlife. If you have a question regarding NWS in wildlife, please contact our Epidemiology Team at NWHC-epi@usgs.gov.
For additional information about NWS myiasis (the disease caused by NWS), see:
Animal disease: New World Screwworm (USDA)
Human disease: Clinical Overview of New World Screwworm | New World Screwworm | CDC