Many European shipping companies say they're unable to guarantee shipments will arrive before the new rules are in place on August 29.

Carriers across western Europe are suspending shipments to the U.S. so they can prepare for the end of the de minimis exemption and new requirements.

"The risk to public health in the United States from this introduction is very low," said HHS spokesperson Andrew Nixon.

The parasite — the larvae of the new world screwworm fly — can devastate cattle herds and is rife in parts of Central America.

The first case in years of New World screwworm infesting a human has been detected in the U.S. The infestation was detected in a person who had recently traveled to El Salvador and is being examined by the Maryland Department of Health and the U.