Eloise B. Cram was born in Davenport, Iowa, the daughter of Ralph Warren Cram, a prominent journalist, and his wife Mabel LaVenture Cram. She graduated Phi Beta Kappa from the University of Chicago in 1919, and earned her PhD from George Washington University in 1925.
In 1920, she went to work as a zoologist for the U.S. Department of Agriculture's Bureau of Animal Industry (BAI). Dr. Cram became a world authority on the parasites of poultry, and eventually rose to the position of Head, Parasites of Poultry and Game Birds. In 1936, she left the BAI for a position at the Zoology Lab of the National Institutes of Health, where she remained until her retirement in 1956.
Her most noted contribution to parasitology and to science in general was her pioneering research into curbing the often-fatal disease schistosomiasis (liver flukes), which is endemic to tropical regions. She made breakthrough discoveries regarding the life- and vector cycles of snails that are key to transmission of the disease to humans. She published more than 160 scholarly papers and monographs on various subjects relating to animal parasitology. In 1955, the year before her retirement, she served a term as the first woman president of the American Society of Parasitologists.