April 6th, Podcast
The return of the New World screwworm isn’t just a livestock issue. It’s a statewide economic and land management concern that could impact cattle operations, wildlife populations, and the $12 billion Texas hunting economy.
On a recent episode of Landowner Insider, I sat down with Dr. T.R. Lansford, Assistant State Veterinarian for Texas, to break down what landowners need to understand, and how to prepare. Here’s what matters most.
What Is the New World Screwworm?
At a basic level, screwworms are fly larvae, but not like the ones most people are familiar with. Unlike common maggots that feed on dead tissue, New World screwworms feed on living flesh, making them uniquely dangerous to livestock, wildlife, and even humans.
The process starts when a female fly lays eggs in open wounds, fresh branding or castration sites, umbilical cords on newborn animals, or damaged tissue and mucous membranes. Within hours, larvae hatch and begin feeding, causing rapid tissue damage and compounding health issues.
Why Screwworms Are a Serious Threat
The real concern isn’t just animal health. It’s the economic ripple effect.
Direct animal losses. Even with treatment, infestations can lead to death loss (historically around 7% in managed herds), severe stress and reduced productivity, and long-term health complications.
Decreased market value. Even if an animal survives, tissue damage creates scar tissue, high-value cuts like ribeye can be compromised, and sale prices drop significantly.
Increased labor and management costs. Operations must shift to frequent, often daily, inspections, more intensive handling, and increased treatment protocols. As Dr. Lansford noted, modern ranches simply don’t have the same manpower or horse infrastructure that existed decades ago to manage outbreaks at scale.
Why This Threat Is Bigger Today Than in the Past
Screwworms were eradicated in the U.S. in 1966, but today’s environment creates much higher risk exposure.
Wildlife populations have exploded: the Texas whitetail population has grown from roughly 500,000 historically to about 5.3 million today, alongside an increased presence of feral hogs and exotic species. Wildlife can’t be easily monitored or treated, making them a major risk vector.
The hunting economy is also at risk. Texas now has a roughly $12 billion annual hunting economy, and a widespread infestation could dramatically impact deer populations, exotic game operations, and lease values and land income streams.
Where Things Stand Right Now
As of now, active infestations are confirmed in Mexico, with the closest cases roughly 180 miles south of Texas. Sterile flies are already being deployed near the border. Experts believe it’s not a question of if, but when, Texas sees an incursion.
How Screwworms Spread
Contrary to popular belief, screwworms aren’t highly mobile on their own. They spread primarily through animal movement such as trucks, trailers, and infested livestock transport. Once established, they rely on open wounds and warm environments, ideally in the 70s to 80s degrees Fahrenheit.
What Landowners Should Be Doing Now
This is where preparation matters most.
- Increase monitoring. The most important tool, as Dr. Lansford put it: “The most important thing we can put on an animal is eyes.” Inspect livestock frequently, ideally daily, and watch for unusual wounds, drainage, behavioral changes, and a strong odor, which is a key indicator.
- Control other parasites. Anything that creates skin irritation increases risk, including flies (horn flies, heel flies), ticks, and lice. Integrated pest management is critical to prevent entry points.
- Treat wounds immediately. Common risk scenarios include branding, castration, dehorning, and tagging. Use approved insecticides (permethrin-based products) and preventative treatments where applicable.
- Plan for increased handling. Operations may need to shift toward bringing cattle closer to facilities, more frequent feeding and observation, and adjusting herd management practices.
- Report suspicious cases early. Early detection is critical to containment. If detected early, authorities can deploy sterile flies and infestations can be contained or eradicated quickly.
What Happens If Screwworms Reach Texas?
Expect regional quarantine zones, increased inspections, movement protocols for livestock, and additional costs for producers. However, movement will still be possible with inspection and treatment. The goal is containment, not shutdown.
Human Risk: Should You Be Concerned?
Screwworms can affect humans, but risk is tied to open wounds and exposure, and U.S. healthcare access significantly reduces danger. This is a concern, but not a reason for panic.
The Bottom Line
The New World screwworm represents a long-term management challenge, not a short-term event. This is a high-impact, low-frequency threat, and early detection and management are critical. Landowners who prepare now will be in the best position. As Dr. Lansford emphasized, this is the “new normal” for the foreseeable future.
Stay Informed
For more resources, visit the Texas Animal Health Commission, Texas A&M AgriLife Extension’s New World Screwworm page, and ScrewwormTX.org.
Watch the Full Episode
This article is based on a recent Landowner Insider conversation with Dr. T.R. Lansford.
Work With Mock Ranches
If you own or manage ranch or hunting land in Texas, staying ahead of risks like this protects both your operation and your land value.
Explore current listings and landowner resources at mockranches.com.
