In 1920, Cram entered government service as a zoologist for the USDA Bureau of Animal Industry (BAI), where she became noted as a world authority on the parasites of poultry, and eventually rose to the position of Head Scientist for the investigation 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 in Bethesda, Maryland, where she remained until her retirement in 1956.