Two new cases were found in Texas in a calf and a dog hundreds of miles apart, the USDA announced Monday.

The U.S. Department of Agriculture has announced that it suspects that the the New World screwworm fly has arrived in south Texas.

The New World screwworm lays its eggs in open wounds and burrows into skin. While human infections are rare, the insect poses an existential threat to cattle farming and dairy production. And it is now in Texas.

Here’s why farmers and scientists are concerned over the New World screwworm’s unwelcome return to the United States.

A sample collected from a three-week-old calf from Zavala County with an umbilical lesion was identified and confirmed as NWS by the U.S. Department of Agriculture's National Veterinary Services Laboratory. TPWD officials said it marked the first case to have originated in the United States in about a decade.

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