USDA is suspending imports of live cattle from Mexico after the Mexican government confirmed a case of New World screwworm in the southern state of Chiapas.

Screwworms are flesh-eating parasites that enter hosts by laying eggs near open wounds, causing infection. 

The United States and several Central American countries eradicated the species several years ago, but the flies have crept northwards recently with new cases in Panama, Costa Rica, Nicaragua and Honduras, according to the Centers for Disease Control and Prevention. The last case on U.S. soil – a Florida deer in 2016 – was the first occurrence of the pest in decades.

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The U.S. buys feeder cattle – young cattle to be fattened for slaughter – from Mexico and the suspension will disrupt an increase in imports from the country. In 2022, the U.S. imported around $635 million of live cattle from Mexico, according to Census Bureau trade data. This had risen to more than $1.1 billion in 2023.

“An updated import alert will be issued with additional guidance once APHIS has implemented mitigations that would allow resumption of imports,” USDA’s Animal and Plant Health Inspection Service said in a statement.