For decades, the United States has been free of the New
World screwworm, a devastating parasitic fly that once caused billions of
dollars in losses to the livestock industry. Thanks to a historic and highly
successful eradication program using the Sterile Insect Technique (SIT), the
pest was pushed back to a buffer zone in Central America. However, recent
developments in Mexico and a confirmed human case in the US have put the
nation's ranchers and public health officials back on high alert.
A Renewed Incursion and a Confirmed Human Case
The screwworm's slow, northward creep from Central America
into Mexico has been a cause for concern for some time, but the situation has
recently become more urgent. After a new case was reported just 370 miles from
the U.S.-Mexico border, the U.S. government announced sweeping new measures to
prevent the parasite's re-entry. These include building a domestic sterile fly
production facility in Texas and suspending live animal imports from Mexico.
Even with these precautions, the parasite has managed to
cross the border. The U.S. Department of Health and Human Services (HHS) and
the Centers for Disease Control and Prevention (CDC) recently confirmed the first human case of screwworm in the United States in over 50 years. The case was travel-associated, identified in a Maryland resident
who had returned from El Salvador. While officials stress that the public
health risk from this isolated case is very low, it serves as a stark reminder
of the threat the screwworm poses.
Economic and Animal Welfare Consequences of This Dangerous New Pest
The consequences of a full-scale screwworm outbreak in the
U.S. would be dire. The larvae of the screwworm fly, whose name comes from
their "screwing" motion as they burrow, feed on the living flesh of
warm-blooded animals. An untreated infestation can be fatal to livestock and
wildlife within a matter of days.
The economic fallout could be immense. Before its
eradication, the screwworm caused an estimated $20 million in annual losses to
the US livestock industry, which would translate to over $900 million today. A
widespread outbreak could lead to billions in lost revenue, not to mention the
immense suffering it would inflict on animals.
It would also necessitate a return to the labor-intensive
practices of constant animal inspection and wound treatment that ranchers
endured for decades. The good news is that agencies like the USDA are taking
decisive action and are working closely with their Mexican counterparts to
contain the pest and protect American agriculture.
A New Texas Facility to Combat the Screwworm Threat
But the screwworm is not eliminated easily with a consumer bug spray, as many
usual pests are.
In a major step to combat the screwworm's renewed threat,
the U.S. Department of Agriculture (USDA) is building a new sterile fly
production facility in Edinburg, Texas. This facility is strategically located
near the U.S.-Mexico border and is designed to produce up to 300 million
sterile flies per week. It will be the only U.S.-based facility of its kind and
will work in tandem with existing facilities in Mexico and Panama.
The flies produced here will be a key part of the Sterile
Insect Technique, which aims to overwhelm the wild screwworm population and
prevent it from becoming established within the United States.
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