The Food and Drug Administration approved a medication targeting New World screwworm infestations in adult dogs and puppies on Thursday.
The Emergency Use Authorization was issued for Simparica TRIO (sarolaner, moxidectin, and pyrantel chewable tablets), the FDA said in an Aug. 13 statement. At present, most dogs in the United States are at low risk of exposure to New World screwworm (NWS) parasites because of their geographic location.
“However, dogs that live in, travel to, or return from areas where NWS infestations have been identified by state or federal animal health officials, as well as certain countries south of the U.S. border, should be closely monitored for signs of infestation, such as visible maggots or foul odors in wounds or body openings (eyes, ears, nose, mouth),” the FDA said.
Simparica TRIO was approved by the FDA to combat heartworm, fleas, and ticks in dogs and puppies in 2020.
After considering the available scientific evidence, the FDA decided it was “reasonable to believe” that the medication may be effective in treating NWS infestations in adult dogs and puppies. The agency judged that the medication’s potential benefits outweigh known and potential risks.
The FDA clarified that Simparica TRIO is not authorized to prevent NWS but only to treat infestations.
According to an FDA fact sheet, a study conducted in Brazil last year assessed the medication’s effectiveness in dogs infested with NWS larvae.
Dogs that received the medication were found to have expelled more live and dead larvae than those who did not receive the treatment.
The primary mechanism of action against NWS “appears to be live larval expulsion. Vomiting should be considered a drug-related adverse reaction,” the fact sheet said.
According to data from the Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), there have been a total of 46 animal cases of NWS infestations in the United States as of Aug. 16, all of them in domestic animals. Currently, four cases are active.
Thirty cases were identified in June, 14 in July, and two so far in August. Most infected animals are sheep, cattle, and goats, with a few dogs.
In its statement, FDA said that one of the active ingredients in Simparica TRIO, sarolaner, is from a class of antiparasitic drugs called isoxazolines that have been linked to neurologic adverse reactions, including loss of coordination, seizures, and tremors.
The medication will only be dispensed by prescription from a licensed veterinarian. The Emergency Use Authorization for Simparica TRIO will remain in effect until it is revoked or an NWS public health emergency declared by the Department of Health and Human Services is terminated. The medication is distributed by Michigan-based Zoetis Inc.
There are also import restrictions on pet dogs entering the United States. According to a July 27 APHIS update, all dogs, including U.S. origin dogs returning to the United States after traveling to Mexico, must meet APHIS requirements for NWS certification on entry or reentry.
In an Aug. 11 statement, the U.S. Department of Agriculture (USDA) announced that it had signed a memorandum of understanding with the Department of Homeland Security, reinforcing a whole-of-government commitment to protecting the country’s food and veterinary systems from threats such as NWS.
The memorandum “further aligns our animal health mission with DHS’s border, security, and inspection authorities, so we are better positioned to detect, assess, and respond to agricultural threats like New World screwworm,” Agriculture Secretary Brooke Rollins said in the statement.
In an Aug. 13 post on X, the official USDA account tracking NWS said that the department has conducted 204 drone flights since June 4 and monitored 24,212 animals for signs of infestation.
Field experts have submitted 80,986 flies from Arizona, California, New Mexico, and Texas so far, with none of them identified as NWS, the department said in an Aug. 11 X post.
