The Parasite You Have Never Heard Of Is Getting Closer and There Is Now an FDA Approved Treatment for Dogs

If you have never heard of New World screwworm, you are not alone. But veterinarians and animal health experts have been keeping a close eye on it, and now pet parents have one more reason to feel prepared rather than panicked. Elanco Animal Health recently announced that the U.S. Food and Drug Administration has given conditional approval to Credelio QuattroTM-CA1 for the treatment of New World screwworm infestations in dogs. This is the first time a companion animal product has received this type of FDA approval specifically for this parasite.

So what exactly is New World screwworm and why does it matter to dog owners? Unlike most flies, screwworms lay eggs in wounds or sores. When the larvae hatch, they feed on living tissue, which can cause serious and fast moving damage if left untreated. While the fly has not been detected in the United States yet, recent cases have been reported within a few hundred miles of the U.S.-Mexico border, mostly connected to cattle movement. That closeness is why animal health companies and regulators are preparing now instead of waiting.

Credelio Quattro-CA1 is a chewable tablet that combines four active ingredients to protect dogs against a wide range of parasites. In addition to New World screwworm, the Credelio Quattro family helps protect against fleas, ticks, heartworm disease, roundworms, hookworms, and tapeworms. For pet parents, that means fewer medications and simpler routines.

This new approval builds on earlier emergency authorizations from the FDA that allowed Credelio products to be used against screwworm in dogs and cats. The difference now is that Credelio Quattro-CA1 has gone through the FDA’s conditional approval process, which means it has been shown to be safe and is expected to be effective based on scientific evidence. That evidence includes a published study in which dogs naturally infested with New World screwworm larvae were treated with lotilaner, one of the key ingredients in Credelio Quattro-CA1. Within 24 hours, the treatment achieved complete effectiveness against the larvae. For a condition that can worsen quickly, that speed matters.

You will not see this product on shelves tomorrow labeled specifically for screwworm, but updated packaging is expected in 2026. The labeling will reflect conditions of use for both Credelio Quattro and Credelio Quattro-CA1, helping veterinarians and pet parents understand when and how the product can be used. For now, the takeaway for dog owners is not fear but preparedness. This approval means that if New World screwworm ever reaches the U.S. and affects pets, veterinarians will have FDA approved options ready. As always, the best step is to talk with your veterinarian about parasite prevention and what products make sense for your dog based on where you live and how you travel.