Screwworm (fly), a parasitic fly known for its screw-shaped larvae, which infest open wounds. The screwworm is a serious pest of livestock and certain domestic and wild animals. It is found in subtropical and tropical climates from the extreme southern United States to Argentina.
Caribbean Islands with Screwworm: Dominican Republic, Haiti, Jamaica, Trinidad & Tobago
Please note: APHIS VS has special requirements for all dogs imported or returning to the United States of America from countries affected with screwworm. Pet and other types of dogs (commercial, breeding, etc.) that are returning, and/or are presented for US entry, from countries or regions where screwworm is known to exist, may enter the US if they meet the following requirements:
- The dog must be accompanied by a certificate signed by a full-time salaried veterinary official of the region of origin stating that the dog has been inspected for screwworm within 5 days prior to shipment to the United States.
- The certificate must state that the dog is either free from screwworm or was found to be infested with screwworm and was held in quarantine and treated until free from screwworm prior to leaving the region.
Aruba: Aruba requires additional certification statements for New World Screwworm, which have been added to the health certificate.
Dogs traveling from countries or regions where screwworm is known to exist may enter the United States if they are accompanied by a certificate signed by a full-time salaried veterinary official of the region of origin stating:
- The dog has been inspected for screwworm within 5 days prior to shipment to the United States; and
- The dog is either free from screwworm OR
- The dog was infested with screwworm, held in quarantine, and treated until free from screwworm prior to leaving the region.
High-Risk Rabies Caribbean Islands (Cuba, Haiti, Dominican Republic)
+Important Update+
As you may have heard, USDA confirmed the presence of New World Screwworm (NWS) in the United States on June 3, 2026. Because this parasite poses a significant threat to the health and welfare of any warm-blooded animal—and in rare cases, even humans—we want to ensure you have clear, practical information to help you safeguard the animals in your care.
Your animals’ wellbeing is our top priority. The following information is intended to help you recognize potential concerns quickly and take prompt action.
What is New World Screwworm?
New World Screwworm (NWS) is the larvae (maggots) of the parasitic fly Cochliomyia hominivorax. NWS does not spread from animal to animal or from animals to people. Rather, infestation occurs when a fly lays eggs on an animal and the maggots enter through any break in the skin—including surgical sites, tick bites, umbilical areas, mucous membranes, and body openings.
Because NWS larvae feed on living tissue, untreated wounds can rapidly worsen, causing severe pain, infection, and potentially death within days to weeks. Early detection is critical for protecting your animals.
What signs should I look for?
You are already observing your animals daily for signs of animal health. These daily observations can make a vital difference in catching problems early.
Carefully observe your animals for any unusual changes, especially open wounds. Possible signs of infestation include:
- Visible maggots in wounds or body openings (nose, ears, mouth, genitals)
- Bloody discharge or foul, decaying odor from wounds
- Behavioral signs of pain or distress such as irritability, depression, head shaking, reduced appetite, or isolation
How can I reduce the risk to my animals?
If you are located near confirmed NWS cases, take extra precautions:
- Avoid non-essential veterinary or husbandry procedures that cause wounds or breaks in the skin
- Ensure all staff are trained to recognize early signs of NWS
Proactive monitoring supports early identification and helps prevent unnecessary suffering.
What do I do if I suspect I may have an affected animal?
If you suspect NWS in any animal—domestic or wildlife—contact your veterinarian immediately. USDA teams are working diligently to limit the spread, and rapid reporting greatly improves our ability to respond.
While awaiting veterinary assistance:
- Isolate the affected animal(s)
- Minimize stress and prevent further injury
Your prompt action can significantly reduce pain, prevent complications, and protect other animals.
Is treatment available?
Yes, NWS can be treated, but immediate intervention is essential. Animals undergoing treatment will require quarantine, and environmental treatment may also be necessary. Your veterinarian will guide you through each step to ensure the best possible outcome for your animals’ health and welfare.
Where can I get more information?
USDA maintains several helpful resources:
screwworm.gov – Central source for U.S. Government regarding New World Screwworm
New World Screwworm Fact Sheet1 – Facts vs myths about New World Screwworm
Current status2 – USDA website updated with latest confirmed detections
Further questions?
For further questions regarding how NWS may affect your facility or animals, please reach out to your Attending Veterinarian or email screwworm@usda.gov . If you have any questions for Animal Care, please reach out to your Animal Care inspector or contact the main office at animalcare@usda.gov or 970-474-7478.
USDA APHIS Animal Care
Program Support Unit A1
Animal and Plant Health Inspection Services
2150 Centre Ave., Building B, 3W11, Fort Collins, CO 80526
p: 970-494-7478 | e: AnimalCare@usda.gov