On Dec. 4, 2025, Merck Animal Health announced the U.S. Food and Drug Administration (FDA) has granted a conditional approval for EXZOLT™ CATTLE-CA1 (fluralaner topical solution). This innovative product is in the newest class of parasiticides known as isoxazolines.

The pour-on solution is effective for the prevention and treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis). It is also conditionally approved for the treatment and control of cattle fever tick (Rhipicephalus microplus).

EXZOLT CATTLE-CA1 was granted conditional approval based on demonstration of safety and a reasonable expectation of effectiveness when administered according to label directions based on global studies conducted by Merck Animal Health in recent years.

EXZOLT CATTLE-CA1 is a pour-on that delivers the active ingredient fluralaner to act systemically against infestations. It is approved for use in beef cattle two months of age and older, and in replacement dairy heifers under 20 months. It is not approved for use in bulls intended for breeding (one year of age and older), dairy calves, and veal calves. There is a 98-day meat withdrawal period.

Merck Animal Health recently received market authorization in Mexico for this product for the prevention and treatment of New World screwworm to help control the spread of the parasite and protect cattle.