Climate change is reshaping the agricultural landscape, introducing new challenges for U.S. livestock producers such as the threat of the New World screwworm (Cochliomyia hominivorax), a parasitic fly that could expand its range into the United States. While the U.S. eradicated screwworm in 1966 through the sterile insect technique, the pest’s recent detection in Mexico and its potential northward spread due to climate change underscore the need for vigilance.
What Is the New World Screwworm?
The New World screwworm is a parasitic fly that severely threatens warm-blooded animals, including livestock, pets, wildlife, and humans. Unlike other flies, screwworm larvae infest living tissue. After adult females lay eggs in wounds or openings on an animal’s body, the larvae hatch and burrow into the host’s flesh, feeding on live tissue. This infestation can lead to severe infections, tissue damage, and, if untreated, death.
Screwworms can infest many animals, including cattle, sheep, goats, dogs, and wildlife. Infestations spread quickly, causing significant economic losses due to reduced productivity, treatment costs, and even animal fatalities. Beyond the immediate impacts, a widespread outbreak would disrupt economies and necessitate costly eradication efforts.
The Current Geographic Spread
New World screwworm is endemic to parts of the Caribbean and South America. Its range has expanded northward recently, with cases reported in Costa Rica, Nicaragua, Honduras, Guatemala, and most recently, Mexico. In Chiapas, near the Guatemalan border, screwworm was detected in a cow, signaling its alarming progression toward the U.S. border.
New World screwworm is endemic to parts of the Caribbean and South America. Its range has expanded northward recently, with cases reported in Costa Rica, Nicaragua, Honduras, Guatemala, and most recently, Mexico. In Chiapas, near the Guatemalan border, screwworm was detected in a cow, signaling its alarming progression toward the U.S. border.
The Economic and Health Implications for U.S. Livestock Producers
Reintroducing screwworm into the U.S. would pose severe risks to livestock health and productivity. Infestations lead to:
- Reduced Productivity: Livestock experience weight loss, decreased milk production, and reproductive challenges.
- High Mortality Rates: Untreated infestations can result in the death of affected animals.
- Increased Costs: Producers face higher costs for treatment, wound management, and preventive measures.
- Trade Restrictions: An outbreak could lead to significant disruptions in livestock trade, which have long-term economic consequences for rural economies.
USDA’s Efforts to Prevent Screwworm Spread
The U.S. Department of Agriculture (USDA) and its Animal and Plant Health Inspection Service (APHIS) are committed to preventing screwworm reintroduction. Key strategies include:
- Biological Barrier in Panama:
- APHIS partners with the Panama-United States Commission for the Eradication and Prevention of Screwworm (COPEG) to maintain a biological barrier in Panama.
- Sterile male screwworm flies were released in the Darien Province to compete with wild males, gradually reducing the population.
- Surveillance and Technical Support:
- APHIS collaborates with Central American governments to monitor and manage outbreaks, providing resources to remove screwworm from newly affected areas.
- Trade Restrictions:
- Currently, importation of animal commodities from or transiting Mexico is restricted to safeguard U.S. livestock.
What Livestock Producers Can Do
U.S. livestock producers are on the frontlines of fighting screwworm infestations. Producers can protect their herds and contribute to broader prevention efforts by remaining vigilant and proactive. Here are some key signs:
- Draining or enlarging wounds
- Signs of discomfort or agitation
- Creamy white eggs near the edges of wounds
- Visible larvae in wounds
If you suspect an infestation, immediately isolate the affected animal and contact your veterinarian.
Search for an accredited veterinarian.
Implement Wound Management Practices
Effective wound care can prevent infestations:
- Treat cuts, scratches, and other injuries promptly.
- Use fly repellents and maintain clean, dry living conditions to reduce fly activity.
- Regularly inspect newborn animals, especially around the umbilical cord stump.
Report Suspicious Cases
Timely reporting is essential to containing outbreaks. If you suspect NW screwworm, immediately notify your state veterinarian or local animal health authorities.
Stay Informed
Keep up with updates from APHIS and other agricultural organizations regarding screwworm detections, restrictions, and preventive measures.
Collaboration and Vigilance Are Key
The fight against New World screwworm requires a coordinated effort among producers, veterinarians, and government agencies. While APHIS continues to lead eradication and prevention efforts, livestock producers are indispensable in protecting their animals and livelihoods.
New World screwworm is a persistent and dangerous threat, exacerbated by climate change and other factors. The recent detection in Mexico underscores the importance of vigilance among U.S. livestock producers. By monitoring animals, managing wounds effectively, and staying informed, producers can protect their herds and help prevent the reintroduction of this devastating pest.
Together, through proactive measures and collaboration, we can keep screwworm at bay and ensure the U.S. livestock sector’s continued health and prosperity.