FDA publishes four more screwworm drug authorizations, adding an over-the-counter wound spray and ivermectin shot for cattle

Every bottle of CLiK Extra sold for New World screwworm now has to carry a website address and a QR code that link to an FDA fact sheet, and if Elanco uses a sticker to add them, it cannot cover up safety information^[1]. Those are two of the conditions in an emergency use authorization (EUA) the Food and Drug Administration (FDA) issued Aug. 7 and made public in the Federal Register on Oct. 15, along with three others^[1].

Two of the four are livestock products a producer can buy without a prescription: Elanco’s dicyclanil wound spray for cattle, sheep, goats, swine and camelids, and Bimeda’s Bimectin ivermectin injection for beef cattle^[1]. The other two, from Zoetis and Sergeant’s Pet Care Products, are for dogs and cats^[1].

What the Oct. 15 notice authorizes

FDA issued the four authorizations on Aug. 7, Aug. 13, Aug. 27 and Sept. 3, and each took effect on its issue date^[1]. The notice reprints the letters in full but not the fact sheets that go with them^[1].

CLiK Extra (dicyclanil topical suspension), Elanco. The spray is a topical insect growth regulator containing 65 mg of dicyclanil per milliliter^[1]. FDA authorized it for over-the-counter use “on or around wounds for the prevention of infestations” by screwworm larvae in sheep, cattle, goats, swine and camelids, and in captive and captured cervids, American bison, bighorn sheep and Sonoran pronghorn^[1]. The letter notes that CLiK Extra “is not FDA-approved for any indication”^[1].

Bimectin (ivermectin) injection, Bimeda. Bimectin is already approved under ANADA 200-447 for internal and external parasites in cattle, swine, reindeer and American bison, but not for screwworm^[1]. The EUA lets it be dispensed over the counter for a subcutaneous dose given within 24 hours of birth, at castration, or when a wound appears^[1]. It applies to cattle “except for female dairy cattle producing milk for human consumption and calves that will be processed for veal,” which the letter shortens to “certain cattle”^[1]. The authorization also covers the same drug sold by three distributors under the names IVERMAX, Ivermectin and Vetrimec 1%, and no other private labels^[1].

Simparica TRIO, Zoetis, and CAPSTAR, Sergeant’s. These cover screwworm in dogs and puppies (Simparica TRIO, by prescription) and in dogs, puppies, cats and kittens (CAPSTAR, over the counter)^[1].

The CLiK Extra letter shows the conditions that come with an EUA. Distributors have to pass the authorization letter and fact sheet down the supply chain and keep lot and shipment records^[1]. Advertising has to say the product is not approved for screwworm, and the companies may not imply it is^[1]. Elanco must report manufacturing defects to FDA within 3 days and serious adverse events within 15 days^[1].

Why FDA says the approved products are not enough

Two screwworm drugs for cattle already hold conditional approval. Intervet, Inc. won conditional approval for Exzolt Cattle-CA, a fluralaner topical solution, on Dec. 4, 2025, and Zoetis received a supplemental approval for Dectomax-CA1 doramectin injection on March 23, 2026^[3].

In a footnote to the Bimectin letter, FDA explains why it still counts neither as an “adequate and available” alternative. The injectable is ruled out because “there are insufficient quantities to meet the demands of a widescale incursion of NWS into the United States”^[1]. The topical is a different drug class, is labeled only for cattle 2 months and older, and requires a prescription, which FDA says “could delay administration”^[1]. The CLiK Extra letter makes a similar case: “Cattle are at particular risk of infestation by NWS,” and a topical in a different drug class adds another option^[1].

The Exzolt label shows what that prescription product involves on the ranch. It is restricted to use by or on the order of a licensed veterinarian, covers beef cattle 2 months and older and replacement dairy heifers under 20 months, and carries a 98-day slaughter withdrawal, shortened to 44 days only if cattle stay at or above 60 degrees Fahrenheit after treatment^[3]. It is not for dairy females 20 months or older, dairy calves or veal calves^[3].

In the field: which herds each product reaches

Cow-calf operations. Bimectin’s three timing windows line up with routine work: processing newborn calves, castrating bull calves and treating wounds^[1]. Because it is over the counter, a producer does not need a vet’s order to keep it on hand for that purpose, though use has to follow the fact sheet^[1].

Dairies. Bimectin’s exclusion of milking females leaves dairies relying on other authorizations. The one aimed at them is the May 19 EUA for Dectomax/Dectomax-CA1, which covers lactating dairy cows, dry cows and replacement heifers 20 months and older, except calves headed for veal^[2]. The same authorization covers prevention in horses a year and older, swine, sheep other than lactating ewes, and deer^[2].

Sheep, goats and hogs. CLiK Extra is the broadest of the new livestock authorizations by species^[1]. The letter says no products are approved to treat or prevent screwworm in sheep, goats, swine, camelids, cervids, bison, bighorn sheep or pronghorn^[1].

Earlier authorizations. By this report’s count, FDA’s five Federal Register notices since December 2025 have announced 15 screwworm EUAs. The first two, issued in October and November 2025, were Elanco products for dogs and cats^[8]. The April notice added three Boehringer Ingelheim authorizations, including prevention in “certain cattle,” and a Health and Hygiene product for cattle, horses, minor hoof stock and birds^[7]. In June, FDA published a second Health and Hygiene authorization and an Elanco authorization covering cattle, swine, goats, sheep, horses and donkeys^[9].

Policy and process: one declaration, three agencies

All of these authorizations rest on one decision. On Aug. 18, 2025, the Secretary of Health and Human Services (HHS) determined that screwworm posed “a significant potential for a public health emergency” with the potential to affect national security, and declared that circumstances justified emergency use of animal drugs against it^[4]. The Commissioner of Food and Drugs had asked for the declaration so FDA could issue the EUAs^[4]. Each authorization stays in force until that declaration is terminated or FDA revises or revokes it^[1].

The drug work runs alongside USDA’s border and fly programs. On July 24, USDA set a phased reopening of southern ports for cattle, starting with Douglas, Ariz., on Aug. 24, with every animal inspected for screwworm^[6]. At that point the nearest active case to Douglas was about 325 miles away, detected July 22^[6]. Commodity Hill covered that plan in earlier coverage of the Douglas port reopening. USDA said Santa Teresa and Columbus, N.M., would be considered after it judged how the first reopening went^[6].

The Environmental Protection Agency (EPA) has a piece of the response too. In March, it published a USDA Agricultural Research Service application to register NovoFly, a genetically engineered screwworm strain whose female embryos die during rearing, so facilities produce only males that are then sterilized by irradiation before release^[5]. USDA told EPA that rearing males only “effectively doubles the output” of the traditional sterile insect technique^[5]. The same application explains the gap the FDA authorizations are meant to fill: because screwworm was eradicated from the United States long ago, “many of the products historically applied to animals are no longer available”^[5]. USDA put the cost of an outbreak in Texas at $1.8 billion^[5]. EPA waived comment on a companion Section 18 emergency exemption and took comments on the full registration through April 27^[5].

What to watch

• More EUA notices. FDA has published five batches since December 2025, and says any reissued authorizations will be posted on its screwworm page for veterinarians^{[1, 2, 7, 8, 9]}.
• Fact sheets. Dosing and withdrawal instructions for the emergency uses are in the fact sheets, which have to accompany every unit sold^[1].
• New Mexico ports. USDA has given no date for Santa Teresa or Columbus, and said the timeline depends on Mexico meeting Action Plan milestones^[6].
• The HHS declaration. No end date is set, and when it ends, every authorization tied to it lapses^{[1, 4]}.