The New World screwworm (NWS) is a devastating pest that was eradicated from the United States in 1966. Unfortunately, it’s now making a troubling resurgence in Mexico, just 70 miles from the U.S. border. Its reappearance has ranchers and veterinarians on high alert.
What Is New World Screwworm?
The New World screwworm is the larval stage of a fly species that feeds on the living tissue of warm-blooded animals. Unlike other maggots that consume dead tissue only, NWS larvae burrow into wounds, causing severe damage to living flesh. Infestations can lead to pain, infection, and even death in livestock, pets, and wildlife.
Adult screwworm flies are best identified by their metallic blue-green bodies and orange eyes. Their larvae, however, are the real threat, burrowing deeper into wounds as they feed.
The most common signs of infestation in animals include agitation, foul-smelling wounds, and visible maggots. Left untreated, animals may stop eating, isolate themselves, and eventually succumb.
Rising Cases in Mexico Raise Alarm
Historically, NWS has been restricted to warmer climates, as it cannot survive prolonged exposure to cold temperatures. However, the southern U.S., including Texas, Florida, and parts of the Southwest, remains vulnerable.
To date, no NWS cases have been detected in livestock in the U.S. Recent reports from Mexico show a 53% increase in cases, with more than 5000 infestations recorded by mid-August. Most of these have been in cattle, though dogs, horses, and sheep have also been affected.
Before its earlier eradication, the pest cost the U.S. livestock industry over $100 million annually. A new outbreak could lead to significant livestock losses, trade embargoes, and expensive eradication campaigns.
What to Do Next
The USDA has implemented a five-point plan, including ongoing monitoring as well as the construction of a sterile fly dispersal facility in Texas. Once operational, the facility is expected to produce more than 100 million sterile flies daily, a key step in controlling the pest’s population.
In addition, the FDA recently approved Dectomax-CA1, the first drug specifically designed to prevent and treat NWS infestations in cattle. This injectable solution provides 21 days of protection and is now available to ranchers under the advice of a veterinarian.
Cattle ranchers are advised to regularly inspect their livestock for the signs of NWS, and to consult their veterinarians about how to best mitigate risk. Other preventative measures, like delaying procedures that cause wounds (like branding or castration) or treating umbilical cords in newborn animals, can further reduce the likelihood of infestation.
By leveraging new technologies and leaning on classic preventative measures, the U.S. can work to keep these harmful pests at bay.