 In 1920 Cram started working as a zoologist for the USDA's Bureau of Animal Industry (BAI), where she was noted as an authority on the parasites of poultry, and eventually gained the position as Head of Parasites of Poultry and Game Birds.In 1936, Cram left the BAI to take a position at the Zoology Lab of the National Institutes of Health (NIH) where her major contribution to parasitology was her pioneering research into the curbing of the helminthic (produced by worms) disease Schistosomiasis.Cram had produced over 160 papers and monographs on various subjects relating to animal parasitology and had become an international authority on helminthic diseases.