New World Screwworm: Information for Veterinarians
FDA’s Center for Veterinary Medicine will update this page as new information becomes available.
The FDA’s Center for Veterinary Medicine (CVM) is working with animal drug sponsors to identify potential products and seek to have them approved or otherwise authorized for the prevention or treatment of New World screwworm (NWS) myiasis.
The agency has multiple regulatory pathways and access mechanisms to facilitate the availability of animal drugs for NWS, summarized below. For more information, see: FDA Regulation of Animal Drugs.
Information on this page:
- Approval & Conditional Approval of Animal Drugs for NWS
- Emergency Use Authorization of Animal Drugs for NWS
- Extralabel Use of Animal Drugs for NWS
Approval & Conditional Approval of Animal Drugs for NWS
For detailed information about approval and conditional approval review processes, please consult the following resources:
- From an Idea to the Marketplace: The Journey of an Animal Drug through the Approval Process
- Conditional Approval Explained: A Resource for Veterinarians
The table below will be updated as the agency approves or conditionally approves drugs to treat or prevent NWS in animals.
Animal Drugs Approved or Conditionally Approved by FDA for NWS
| Product | Approval or Conditional Approval? | Indication(s) | Species Freedom of Information | Summary |
|---|---|---|---|---|
| Dectomax-CA1 (doramectin injection) injectable solution | Conditional Approval | Prevention and treatment of infestations caused by larvae of Cochliomyia hominivorax (myiasis), and prevention of reinfestation for 21 days in cattle. | Cattle | cNADA 141-616 |
| Exzolt Cattle-CA1* | Conditional Approval | Prevention and treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis) and treatment and control of cattle fever tick (Rhipicephalus microplus) in beef cattle 2 months of age and older and replacement dairy heifers less than 20 months of age. | Cattle | cNADA 141-617 |
| Credelio Quattro-CA1 | Conditional Approval | Treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis) in dogs and puppies. | Dogs | cNADA 141-619 |
*extralabel use of this animal drug is not permitted
Emergency Use Authorization of Animal Drugs for NWS
On August 18, 2025, the Department of Health and Human Services issued a declaration that enables FDA to issue Emergency Use Authorizations (EUAs) for animal drugs to treat or prevent infestations caused by NWS. For an overview of the EUA process, see: Summary of Process for EUA Issuance.
The table below will be updated as the agency issues EUAs for drugs to treat or prevent NWS in animals.
Emergency Use Authorizations Issued by FDA for NWS Animal Drugs
| Product | Indication(s) | Species | Links to additional information |
|---|---|---|---|
| Credelio (lotilaner) chewable tablets | Treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis) in dogs and puppies. | Dogs | |
| Credelio CAT (lotilaner) chewable tablets | Treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis) in cats and kittens. | Cats | |
| Ivomec (ivermectin) injectable solution | For prevention of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis) when administered within 24 hours of birth, at the time of castration, or at the appearance of wound in cattle, except for female dairy cattle producing milk for human consumption and calves that will be processed for veal. | Cattle |
Extralabel Use of Animal Drugs for NWS
Veterinarians may prescribe FDA-approved products for uses that are not on the label, in accordance with the existing regulations (21 CFR Part 530) including a valid veterinary/client/patient relationship. CVM encourages veterinarians to review these regulations. It is particularly important for food animal veterinarians to be aware of the additional requirements for extralabel use in food-producing animals including rules against extralabel use of drugs administered as medicated feed.
Extralabel use of FDA-approved animal drugs is limited to drugs with a new animal drug approval (NADA), which means it does not include conditional approvals, index listed products, or products with an emergency use authorization (EUA)
A small number of animal drugs have full FDA approval for non-NWS indications and conditional approval or an EUA for NWS. These animal drugs can be used in an extralabel manner because they have a full approval, even though conditionally approved or emergency use authorized drugs typically cannot be used in this way.
A helpful reference tool is: The Ins and Outs of Extra-Label Drug Use in Animals: A Resource for Veterinarians.