Warmer temperatures expected to bring increase in parasitic fly’s activity
U.S. Rep. Gabe Vasquez (D-NM) led a letter this week from congressional lawmakers asking top federal agricultural officials to report on their efforts to curb the spread of a parasitic fly through Mexico, and prevent its penetration into U.S. herds.
The New World screwworm is named for the maggot’s behavior of burrowing into flesh and causing serious or fatal wounds in animals. Last year, it advanced northward through Mexico after being mainly contained in Central America for several decades. Before U.S. officials declared the fly eradicated in the 1960s, the wounds from parasites would kill wild and domestic animals, sometimes at a rate of one-in-five animals in an infected herd.
The April 13 letter, addressed to U.S. Department of Agriculture Secretary Brooke Rollins, requests a formal briefing to update members of the House Agriculture Committee on the federal response to “numerous cases” of New World screwworm reported near the border, as fly activity is expected to rise with warmer temperatures.
To date, more than 20,000 cases have occurred, mostly in Mexican livestock, according to federal data, including three active cases in the northern state of Nuevo León.
USDA did not respond Wednesday to Source NM’s request for comment on the letter.
Last July, the USDA closed ports of entry to livestock to prevent the fly’s advance, which has cost the largest crossing in New Mexico more than $1 billion.
To combat the outbreak, agriculture officials in the U.S. and Mexico in recent weeks have dropped 100 million sterile male flies in active cases near the Texas-Mexico border and broke ground on a new facility to ramp up their production by November 2027. Since the flies have a lifespan of about 21 days, sterile flies can significantly curb screwworm numbers by ensuring eggs go unfertilized.
Vasquez, in the letter, requested an update on the status of sterile fly production and dispersal around Texas, a description on how $100 million to address the problem is being spent and which criteria USDA will use to possibly reopen the border crossing for livestock.
The letter stated that an outbreak would worsen grocery prices, noting that domestic cattle herd declines have already raised the cost of beef.
“Any outbreak in the U.S. would be devastating to livestock producers and push cattlemen and women near the border to liquidate their herds, which would compound the herd contraction that we’ve seen across the country,” the letter said.
In addition to Vasquez, six other Democratic members of Congress signed the letter, representing California, Georgia, Kansas, Maryland, Minnesota and Nevada.
The letter followed the April 10 announcement of the northernmost active New World screwworm case: an infested dog reported in Nuevo León, Mexico about 88 miles south of the Texas border.
The detection prompted a warning from Texas Agriculture Commissioner Sid Miller, who urged additional sterile fly production and more awareness for early detection. Miller criticized the federal response, saying, “the reality is the spread of the New World screwworm has not been successfully contained to date.”
He urged Texans to be familiar with the signs of infestation such as rapidly worsening, foul-smelling skin wounds with visible maggots or eggs.
“There is zero margin for delay when it comes to screwworm. Early detection is the difference between containment and a full-blown crisis that could devastate herds and livelihoods,” he said in the statement.
