An outbreak of New World screwworm fly is devastating cattle in Mexico. Now it’s 60 miles from Texas and could send beef prices past record highs

In the past 18 months, tens of thousands of cases have been reported in Mexico, but not so close to the border.

Cattle populations hits low as threat looms

A possible infestation could not come at a worse time for ranchers or consumers. The U.S. cattle herd is currently at a 75-year low. U.S. farms were estimated to have just 86.2 million head of cattle in 2025, the lowest number since 1951.

That’s affected by the record-high prices cattle are fetching, along with consolidation in the cattle sector, drought, and rising costs to raise new cattle. From 2017-2022, the number of cattle operations in the U.S. declined by 17%, according to the USDA.

Texas ranchers currently make up about 15% of the entire U.S. cattle herd, occupying roughly 125 million acres.

Protecting U.S. cattle from diseases

The New World screwworm is a particularly nasty parasite (beware of detailed descriptions ahead). The maggots lay eggs in open wounds and mucous membranes, then feed on the blood of their hosts with tiny mouth hooks. If left untreated, they can kill a full-grown cow in less than two weeks. Occasionally, the parasites can infect humans; mainly those who have open wounds and are living in unhygienic conditions. This is very rare and usually not dangerous.

U.S officials take the threat of screwworm seriously. As Mexico reported infestations were moving north last summer, the USDA closed the border to livestock trade. That was a notable action, as Mexico accounted for 62% of U.S. live cattle imports between 2020 and 2024.

“The protection of our animals and safety of our nation’s food supply is a national security issue of the utmost importance,” U.S. Secretary of Agriculture Brooke L. Rollins said at the time. “Once we see increased surveillance and eradication efforts, and the positive results of those actions, we remain committed to opening the border for livestock trade. This is not about politics or punishment of Mexico; rather it is about food and animal safety.”

The last time there was an outbreak in the U.S. was in 1976 in Texas. More than 1.4 million cattle, along with thousands of other animals, were affected. A similar infestation today would cost the Texas economy an estimated $1.8 billion, according to reporting in the Texas Standard.