HOUSTON – The U.S. Food and Drug Administration has authorized the emergency use of an over-the-counter drug to treat New World screwworm infestations in dogs and cats as officials work to contain the parasite’s spread in Texas, New Mexico and other affected areas.
The FDA announced Thursday that it issued an Emergency Use Authorization for generic Nitenpyram Tablets, allowing the drug to be used to treat New World screwworm infestations, known as myiasis, in dogs, puppies, cats and kittens that are at least 4 weeks old and weigh at least 2 pounds. The authorization marks the first generic animal drug approved for use against the parasite.
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Federal officials said most dogs and cats in the United States remain at low risk for infection, though the risk is higher for animals that have recently been in areas with confirmed screwworm cases.
New World screwworm flies lay eggs in open wounds or mucous membranes. The larvae hatch within hours and burrow into living tissue, feeding on flesh and causing potentially severe injuries.
If left untreated, infestations can be fatal.
According to the FDA, nitenpyram works quickly and can kill most screwworm larvae within hours of the first dose. Pet owners are advised to administer a second dose six hours later. The agency said veterinarians may still need to remove remaining larvae and provide wound care because the medication does not prevent reinfestation.
The tablets are available over the counter in two dosage strengths, 11.4 milligrams and 57 milligrams, with dosage based on an animal’s weight. The FDA said the medication should not be given to pets weighing less than 2 pounds.
“Preventatives that they take already can help prevent those flies from causing the issue,” said Dr. Elizabeth Topliff at Southside Place Animal Hospital.
They include:
- Credelio (lotilaner chewable tablets) for dogs
- Credelio CAR (lotilaner chewable tablets for cats and kittens
- NexGard (afoxolaner chewable tablets) for dogs
- NexGard COMBO (afoxolaner chewable tablets) for cats
The authorization comes as states take additional steps to prevent the parasite from spreading.
In Florida, Agriculture Commissioner Wilton Simpson announced this week that the state is expanding emergency restrictions following additional screwworm detections in Texas and New Mexico. Under the updated emergency rule, rescue dogs, rescue cats, shelter dogs and shelter cats originating from states with confirmed New World screwworm detections are prohibited from entering Florida until further notice.
Florida also extended a temporary moratorium on imports of warm-blooded animals from counties with confirmed detections and surrounding counties while requiring additional inspections and treatment documentation for some animal movements.
The parasite was eradicated from the United States decades ago, but recent detections in Texas and New Mexico have triggered a large federal and state response. The FDA said it has issued multiple emergency authorizations and approvals for animal drugs intended to prevent or treat screwworm infestations as agencies work to contain the outbreak.
Officials continue to urge pet owners, veterinarians, livestock producers and animal shelters to monitor animals closely for wounds that are slow to heal or show signs of larvae infestation and to report suspected cases promptly. However, the risk for pets in Harris County remains low.
“I think here in Houston, right now, we shouldn’t be too worried about it,” said Dr. Topliff.
“While we have shared information internally with staff and discussed potential public messaging should things escalate, with less than 10 cases confirmed in the entire state, and none close to Harris County, we don’t want to cause any unnecessary panic at this time,” added BARC Animal Shelter Manager Jarred Mears.