What Dairy Producers Need to Know About the New World Screwworm
For more than 60 years, the New World screwworm has been considered a problem of the past in the United States.
Now, it's back on the radar.
Recent detections closer to the U.S. border have renewed concerns across the livestock industry, prompting producers, veterinarians, and animal health experts to prepare for the possibility of the parasite moving north. While the screwworm hasn't become widespread in U.S. dairy herds, awareness and early detection are critical to keeping it that way.
In a recent episode of the Uplevel Dairy Podcast, Dr. Mike Catangui of MWI Animal Health joined Peggy Coffeen to explain what the New World screwworm is, why dairy producers should be paying attention, and the practical steps farms can take to protect their herds.
What Is the New World Screwworm?
Despite its name, the New World screwworm isn't actually a worm.
It's the larval stage of a fly.
Adult female flies lay eggs in open wounds or areas where tissue is exposed. After hatching, the larvae burrow into living flesh, feeding on healthy tissue rather than dead tissue like many other fly larvae.
That feeding behavior causes significant pain, tissue damage, secondary infections, and, if left untreated, can become life-threatening.
Dr. Catangui explains that newborn calves are especially vulnerable because their healing umbilical cords provide an ideal location for flies to lay eggs. Surgical sites, dehorning wounds, and other injuries can also become points of infestation.
Why Dairy Farms Should Be Paying Attention
While the New World screwworm has not become an everyday concern for U.S. dairy producers, today's dairy operations create conditions where vigilance is essential.
Large numbers of calves are born every day.
Animals move between farms, sale barns, and state lines.
Employees work with cattle throughout every stage of production.
Because of that movement, early detection becomes one of the industry's greatest defenses.
Dr. Catangui emphasized that producers purchasing cattle from affected regions or areas near outbreaks should work closely with their veterinarians and carefully inspect animals before introducing them into the herd.
Biosecurity remains one of the best tools producers have for preventing disease and parasite introduction.
Early Detection Can Make All the Difference
One of the biggest takeaways from the conversation is that producers should know what normal healing looks like.
If a wound appears unusually inflamed, continues to enlarge, develops unexpected drainage, or contains moving larvae, immediate veterinary attention is critical.
The New World screwworm is a reportable animal disease.
That means suspected cases shouldn't simply be treated on the farm. Veterinarians and state animal health officials need to be notified so appropriate testing and response measures can begin quickly.
Rapid reporting protects not only individual farms but the entire livestock industry.
Prevention Starts with Good Animal Health Practices
There is no single solution for preventing screwworm infestations.
Instead, prevention relies on a combination of good management practices.
Keeping wounds clean, monitoring newborn calves, minimizing fly pressure, maintaining strong biosecurity protocols, and working with a veterinarian to develop parasite control strategies all help reduce risk.
Dr. Catangui also discussed how products that control external parasites can become valuable tools as part of an overall herd health program.
Every operation is different, so producers should work with their veterinary team to determine which products and management practices best fit their herd.
The Industry Has Defeated Screwworm Before
Although renewed concerns are understandable, Dr. Catangui also shared an encouraging reminder.
The United States has successfully eliminated the New World screwworm before.
One of the most remarkable animal health success stories involved the Sterile Insect Technique, where sterile male flies were released to interrupt the parasite's life cycle and ultimately eradicate it from the country.
Today's veterinary infrastructure, surveillance systems, and communication networks provide producers with even more resources than were available decades ago.
The key is remaining proactive rather than reactive.
Biosecurity Is Everyone's Responsibility
Protecting the dairy industry doesn't happen through one producer alone.
It requires veterinarians, nutritionists, consultants, animal health companies, regulators, and producers all working together.
When suspicious cases are identified quickly, reported appropriately, and managed effectively, the risk of widespread outbreaks decreases dramatically.
As Dr. Catangui emphasized, awareness is one of the most valuable tools producers have.
Knowing what to look for—and acting quickly when something doesn't seem right—can make a significant difference.
The New World screwworm serves as an important reminder that biosecurity should never become an afterthought.
While the parasite remains a relatively low risk for many producers today, staying informed and maintaining strong herd health practices are essential to protecting both individual operations and the dairy industry as a whole.
By working closely with veterinarians, monitoring animals carefully, and responding quickly to potential concerns, dairy producers can help keep this historic threat from becoming tomorrow's problem.
To hear the complete discussion, stream now on Apple Podcasts or Spotify, or watch the full conversation on YouTube.
