Federal regulators moved quickly on June 11 to authorize an emergency treatment for the New World screwworm in dogs and cats, the latest in a series of rapid government responses since the flesh-eating parasite made its first confirmed appearance in the United States in years.
The Food and Drug Administration cleared generic nitenpyram, manufactured by Felix Pharmaceuticals, for use in treating screwworm infestations in dogs, puppies, cats, and kittens weighing at least two pounds and older than three weeks of age. The authorization was granted on an emergency basis, reflecting the urgency regulators have attached to containing the pest before it can establish a wider foothold.
A parasite that was supposed to be gone
The New World screwworm was officially eradicated from the United States in 1966 through a targeted biological strategy centered on releasing sterile male flies into the wild. Those males mated with females, producing infertile eggs, and the population eventually collapsed. The approach was considered one of the more successful pest eradication campaigns in American agricultural history, and the screwworm had rarely been detected in the country since.
That changed this month. A confirmed case in a calf in Texas was announced on June 3, marking the parasite’s return to American soil. Multiple additional cases in animals have since been identified, prompting regulators to accelerate their response across both livestock and companion animal categories.
Months of preparation behind the authorization
The speed of the FDA’s response was not accidental. The agency had spent nearly a year preparing for the possibility that the screwworm might cross into the United States, monitoring the pest’s northward movement through Mexico and other parts of Latin America in the years leading up to the confirmed Texas case. That preparation produced a pipeline of authorizations ready to deploy the moment the threat became domestic.
By the time nitenpyram received its emergency clearance on Thursday, the FDA had already issued emergency authorizations for ten drugs and granted conditional approval to three others for use against screwworm. Among the earlier approvals was an injectable treatment cleared in mid-May to prevent and treat infestation in dairy cattle, swine, horses, sheep, and deer.
Health Secretary Robert F. Kennedy Jr., in a statement accompanying Thursday’s announcement, framed the pet drug authorization as both a practical and strategic measure, arguing it places an accessible and fast-acting option in the hands of pet owners while reinforcing the government’s broader effort to prevent the parasite from spreading further.
Why speed matters with screwworm
The screwworm poses a particularly serious threat because of how it operates. Unlike many parasites, it targets living tissue rather than dead matter, with larvae burrowing into open wounds or body orifices of warm-blooded animals including livestock, wildlife, and pets. Left untreated, infestations can be fatal. The speed of reproduction and the severity of the damage make early detection and rapid treatment essential to any containment strategy.
The arrival of screwworm in the continental United States after nearly six decades of absence represents a significant agricultural and animal health challenge. Regulators appear aware that the window for effective containment is narrow, and the pace of emergency authorizations suggests the government is treating this as a time-sensitive crisis rather than a manageable background concern.
