The FDA has authorized the emergency use of a spray against the larvae of the fly Cochliomyia hominivorax.

The FDA has granted emergency use authorization for the veterinary product CLiK Extra, intended for the prevention of screwworm infestations, specifically the New World screwworm. The product is a dicyclanil suspension for topical application and is applied to wound areas, including surgical incisions and sites sustained by livestock animals during birthing. The authorization covers cattle, sheep, goats, swine, camelids, as well as a range of wild species, including the American bison, bighorn sheep, and pronghorn.

It is important to note that the product is intended exclusively for prophylaxis. In the event that a wound is already infested with larvae or if infestation occurs after application, the manufacturer (Elanco) recommends using alternative treatment methods. A specific feature of this fly species is that, unlike most other parasites, its larvae feed on the living tissues of the host, burrowing deep into the wound. This leads to its enlargement, the development of an odor that attracts more insects, and the rapid death of the livestock animal without proper care.

This emergency measure was a response to the detection of an infestation case in a three-week-old calf in Zavala County, Texas. According to the regulator, the benefits of using the product in the current circumstances outweigh the potential risks. Although the parasite was eradicated in the U.S. decades ago, the current situation requires vigilance on the part of livestock producers and veterinary specialists.

This measure is part of a series of emergency authorizations issued by the FDA since August 2025. Previously, the agency approved a number of other products, including ointments, powders, and injectable preparations for various animal species, including horses, dogs, and cats. The choice of a specific product depends on the goals — prophylaxis or treatment — and the type of animal.

Specialists remind that the parasite can also pose a threat to humans if eggs enter open wounds or mucous membranes, although such cases are extremely rare. If an infestation is suspected, veterinarians should contact the USDA or local public health authorities rather than attempting to manage the problem on their own.