FDA-authorized and approved animal drugs for New World screwworm

Over the past year, the FDA has issued a series of emergency use authorizations (EUAs) and conditional approvals for drugs to prevent and treat New World screwworm (NWS) infestations in livestock, companion animals, exotic species, and wildlife.

Veterinarians who suspect NWS should immediately contact their state animal health official or USDA. Contact information can be accessed through this USDA contact page.

In Texas, suspected livestock cases should be reported directly to the Texas Animal Health Commission (TAHC) in their closest area office. The USDA's National Veterinary Stockpile has also relocated NWS treatment supplies to Texas, where they are available through TAHC.

Below is a roundup of the drugs currently authorized, conditionally approved, or otherwise available for the prevention and treatment of NWS.¹

Dogs

Credelio Quattro-CA1 (Conditional Approval)

• Indicated for the treatment of infestations caused by NWS (Cochliomyia hominivorax) larvae (myiasis) in dogs and puppies.

Credelio (FDA Emergency Use Authorization)

• Indicated for the treatment of infestations caused by NWS larvae (myiasis) in dogs and puppies.

NexGard (FDA Emergency Use Authorization)

• Indicated for the treatment of infestations caused by NWS larvae (myiasis) in dogs and puppies.

Cats

Credelio CAT (FDA Emergency Use Authorization)

• Indicated for the treatment of infestations caused by NWS larvae (myiasis) in cats and kittens.

NexGard COMBO (FDA Emergency Use Authorization)

• Indicated for the treatment of infestations caused by NWS larvae (myiasis) in cats and kittens.

Cattle

Dectomax-CA1 (doramectin injection) (Conditional Approval)

• Indicated for the prevention and treatment of infestations caused by NWS larvae (myiasis) and prevention of reinfestation for 21 days.

Exzolt Cattle-CA1 (fluralaner topical solution) (Conditional Approval)

• Indicated for the prevention and treatment of infestations caused by NWS larvae (myiasis) and for the treatment and control of cattle fever tick (Rhipicephalus microplus) in beef cattle 2 months of age and older and replacement dairy heifers younger than 20 months.
• Extralabel use is not permitted.

Ivomec (ivermectin injection) (FDA Emergency Use Authorization)

• Indicated for the prevention of NWS infestations when administered within 24 hours of birth, castration, or the appearance of a wound.

Dectomax/Dectomax-CA1 (doramectin injection) (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations in lactating dairy cows, dry dairy cows, replacement dairy heifers, and dairy cattle 20 months of age and older, except calves intended for veal.

Horses

Dectomax/Dectomax-CA1 (doramectin injection) (FDA Emergency Use Authorization)

• Indicated for the prevention of NWS infestations in horses 1 year of age and older.

F10 Antiseptic Wound Spray with Insecticide (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations.

F10 Antiseptic Barrier Ointment with Insecticide (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations.

Negasunt Powder (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations.
• Extralabel use is not permitted.

Sheep

Negasunt Powder (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations.

Dectomax/Dectomax-CA1 (doramectin injection) (FDA Emergency Use Authorization)

• Indicated for the prevention of NWS infestations in sheep, except lactating sheep.

Goats

Negasunt Powder (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations.

Swine

Negasunt Powder (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations.

Dectomax/Dectomax-CA1 (doramectin injection) (FDA Emergency Use Authorization)

• Indicated for the prevention of NWS infestations.

Deer

Dectomax/Dectomax-CA1 (doramectin injection) (FDA Emergency Use Authorization)

• Indicated for the prevention of NWS infestations.

Exotic, zoo, and wildlife species

F10 Antiseptic Wound Spray with Insecticide (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations in minor species of hoofstock, raptors and other wild birds, pet birds, and captive wild, exotic, and zoo mammals.

F10 Antiseptic Barrier Ointment with Insecticide (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations in minor species of hoofstock, raptors and other wild birds, pet birds, and captive wild, exotic, and zoo mammals.

Negasunt Powder (FDA Emergency Use Authorization)

• Indicated for the prevention and treatment of NWS infestations in captive wild, exotic, and zoo mammals.

What the FDA wants veterinarians to know

On June 5, 2026, FDA's Center for Veterinary Medicine published a Dear Veterinarian letter with guidance that all practitioners using these products should review. The key points²:

• No product currently has full FDA approval for NWS. All authorized products are either conditionally approved or operating under an EUA. FDA reviewed data on animal safety, effectiveness, and food safety before authorizing each one.
• EUA products carry specific obligations. Veterinarians prescribing an EUA product must inform clients that it is authorized for emergency use but not FDA-approved. Practitioners are responsible for discussing risks, benefits, and available alternatives. For food-producing animals, clients must be informed of any applicable withdrawal times.
• Record keeping is required for EUA products. Veterinary facilities must maintain records, including client and patient information, product details (doses, lot number, co-administered drugs), and the specific EUA condition being treated. Each product's Letter of Authorization contains specific requirements.
• Use only authorized products, and only when medically necessary. FDA has noted that antiparasitic resistance in NWS has developed over time in some countries. Misuse, overuse, or use of non-authorized products risks undermining the effectiveness of antiparasitic drugs against NWS and other parasites. Unauthorized products have also not been reviewed for safety or food residue concerns.
• Extralabel use rules still apply. Extralabel use is only permitted for products with full FDA approval, not for conditional approvals or EUAs. A handful of products carry full approval for non-NWS indications alongside a conditional approval or EUA for NWS, and those may be used extralabel. Veterinarians should review 21 CFR Part 530 for full requirements.
• Report adverse events. FDA asks veterinarians to report any adverse events, including lack of effectiveness, to the product sponsor or directly to FDA.

Questions can be directed to FDA's Center for Veterinary Medicine at [email protected]. For region-specific risk guidance, contact your state veterinarian.

References

1. New World Screwworm: Information for Veterinarians. FDA. June 5, 2026. Accessed June 8, 2026. https://www.fda.gov/animal-veterinary/safety-health/new-world-screwworm-information-veterinarians#Approval
2. Dear Veterinarian Letter: Use of FDA-Authorized Animal Drugs Against New World Screwworm Myiasis. News release. FDA. June 5, 2026. Accessed June 8, 2026. https://www.fda.gov/animal-veterinary/product-safety-information/dear-veterinarian-letter-use-fda-authorized-animal-drugs-against-new-world-screwworm-myiasis