Mexico confirms 2nd New World screwworm case in border state

Another case of a flesh-eating parasite has been detected in a Mexican state that shares a border with the United States.

The report of New World screwworm in the state of Nuevo León, which shares a small stretch of border with Texas, marks the second case of the parasitic fly larvae there in about two weeks.

Mexico’s agriculture ministry reports the infected cow came from the south of Mexico, and the larvae were either dead or dying thanks to mandatory treatment to prevent the spread of the deadly parasite.

That treatment is part of Mexico’s new protocols that the country hopes will convince the United States to reopen the border to cattle. The U.S. Department of Agriculture closed the border to livestock in May to block the screwworm’s spread, affecting ranchers across northern Mexico who raise their cattle for export.

The first case of New World screwworm in Mexico was found in the south of the country, near the Guatemala border, in November of last year. Since then, Mexico has accumulated thousands of cases.

The vast majority have been in southern Mexico, far from the U.S.-Mexico border. The two cases in the border state of Nuevo León were both detected before the larvae had developed into flies, according to Mexico, meaning the incidents near the border appear to be contained.

But the northern detection of the parasite could hamper Mexico’s efforts to reopen the U.S.-Mexico border, leaving ranchers in states like Sonora — which has not had any reporters of the parasite — struggling financially as they try to figure out what to do with cattle that was bred to be exported to the United States.

The New World screwworm primarily affects cattle but can spread to any warm blooded animal. The United States eradicated the pest in the 1960s.