Mexico's active screwworm cases down 57% since mid-December, ministry says

MEXICO CITY, Jan 8 (Reuters) - Mexico's active cases of New World screwworm, a flesh-eating parasite that has kept the U.S.-Mexico border closed to Mexican livestock, have fallen 57% since mid-December, the country's agriculture ministry said on Thursday.

• Active cases dropped to 492 as of January 7, from 1,145 registered on December 10, the ministry said, overwhelmingly concentrated in a handful of states.

• Construction for a factory to breed sterile flies in Chiapas state is 48% complete and is on track to start operating in the first half of this year, the ministry said, when it will produce some 200 million flies per week.

• The flies will be released into the wild, so when sterile males mate with wild females, no offspring are produced and the population collapses over time.

• The screwworm outbreak, which has moved northward through Central America and deep into Mexico, has strained relations with the United States, Mexico's biggest trading partner.

• The U.S. has kept its border mostly closed to Mexican cattle imports since May.