Dive Brief:
- The United States has paused imports of cattle from Mexico after a positive detection of New World screwworm, a flesh-eating pest that can be fatal to animals and in some cases humans.
- Authorities identified an infected cow at a livestock inspection checkpoint close to the border of Guatemala. Given the northward movement of screwworm, the U.S. Department of Agriculture said it is “restricting the importation of animal commodities” — live cattle and bison — that originated or were transported through Mexico, effective immediately.
- The suspension of Mexican cattle could affect U.S. beef production and prices. The pest, which gets its name from the way it burrows into wounds like a screw, last appeared in Florida in 2016 and marked the first U.S. outbreak in decades.
Dive Insight:
The U.S. has relied on live cattle imports from Canada and Mexico to fill in the gaps from years of herd declines. In 2023, imports of cattle from Mexico increased 43% to 1.25 million head following a record low year. That represented about 3.7% of the U.S. calf crop.
The USDA’s Animal Plant and Health Inspection Service moved forward with a temporary pause in cattle imports from Mexico pending further information from the country’s veterinary officials regarding the size and scope of the screwworm infestation. The agency said it is working with regional partners to prevent the pest from entering the U.S.
The deadly fly larvae, which can burrow into warm-bodied animals as well as humans, is endemic to countries in the Caribbean and South America, with cases spreading northward into Honduras, Costa Rica and now Mexico.
Since 2006, APHIS has worked with Panama to maintain a barrier zone to prevent the spread of screwworm into Central and North America. However, cases have exploded north of the barrier over the past two years as more land is converted to farming and more cattle are transported into the region.
In recent months, APHIS has stepped up its efforts with impacted countries to "push this pest out of newly affected areas,” Dr. Rosemary Sifford, chief veterinary officer of the United States, said in a statement.
“With this latest find in Mexico, we will further intensify this work to protect American agriculture and reestablish the barrier in Central America,” she added
Screwworm detections in Panama jumped from an average of 25 cases per year to more than 6,500 cases in 2023, according to the USDA. APHIS is investing nearly $110 million to combat detections and keep the pest from spreading into North America.
A Florida Newworld Screwworm outbreak in 2016 marked the first time the pest was found in the U.S. in decades. The pest was removed through an eradication campaign involving the release of 154 million sterile flies.
The name screwworm refers to the maggots’ feeding behavior, burrowing into wounds like a screw being driven into wood, according to the USDA. The fly larvae can cause extensive damage to host tissue with their sharp mouth hooks, and the wounds can become larger as more screwworms hatch.
