New World Screwworm

New World Screwworm is a parasitic fly whose larvae (maggots) burrow into the host’s living tissue. This differs from other species of fly whose maggots feed on dead tissue. NWS is endemic in Cuba, Haiti, the Dominican Republic, and countries in South America. In early 2025 cases began spreading northward through Mexico. It spreads most quickly through infected animals carrying either flies or larvae, especially animals traveling from affected regions. NWS can affect all warm-blooded animals and most cases are in cattle, sheep and goats. NWS larvae are transmitted when a female fly lays eggs on an open wound. Some common wound examples include insect bites, animal husbandry wounds, wire cuts, and other injuries. The NWS flies also target the navel of newborn animals. NWS infested wounds often attract other female screwworms and many infestations on a single wound are possible.

New World Screwworm has not been confirmed in Minnesota at this time.

U.S. cases were first detected in Texas in June 2026. Additional cases can be found in the "National Cases Dashboard" section of this webpage, which displays the USDA's confirmed NWS cases. Anyone who suspects a case of NWS in Minnesota should contact the Board of Animal Health at either animalhealth@state.mn.us or by phone at 651-296-2942.

Minnesota Import Requirements for Dogs and Cats Entering from States with New World Screwworm (NWS) Infestations and Endemic Areas:

1. Animals from USDA-designated active NWS sites will not be allowed import to Minnesota. The Board of Animal Health will allow imports from states with USDA-active cases if they meet all import requirements outlined in this policy.
2. A Certificate of Veterinary Inspection (CVI) must be issued by an accredited veterinarian within 72 hours prior to transport. The CVI is valid for seven days from the date of issuance. The CVI must include the USDA-required certification attesting the animal has been inspected and determined to be free of NWS and that all applicable NWS import requirements have been satisfied.
3. Email a valid rabies vaccination certificate or pet passport to pet.travel.bah@state.mn.us no later than three days before the animal’s arrival in Minnesota.
4. An EPA- or FDA-approved NWS treatment must be administered to dogs and cats following the manufacturers’ dosing guidelines. The product name, dosage and date of treatment must be listed on the CVI and also emailed to pet.travel.bah@state.mn.us within five days of departure.
5. All animals will be quarantined for a minimum of five days upon arrival in Minnesota. Board of Animal Health staff will verify the quarantine is being followed and confirm quarantine release details.
6. Animals that do not meet import requirements will be quarantined for a minimum of 10 days and must be examined by a licensed veterinarian, who must confirm in writing that the animal is free of NWS and note the exam date.
7. Immediately notify pet.travel.bah@state.mn.us if any signs of NWS develop during quarantine.

Dogs and cats entering the U.S. may be subject to regulations from multiple federal agencies.

• USDA APHIS requires specific import certification for dogs arriving from NWS-affected countries.
• The CDC requires all dogs and cats to appear healthy upon arrival in the U.S.