In 1899, American zoologist Charles Wardell Stiles identified progressive pernicious anemia seen in the southern United States as being caused by the hookworm A. duodenale.
In the 1920s, hookworm eradication reached the Caribbean and Latin America, where great mortality was reported among people in the West Indies towards the end of the 18th century, as well as through descriptions sent from Brazil and various other tropical and sub-tropical regions.