While at the NIH, Cram contributed to the scientific study of pinworm and other parasites in humans, but her major contribution to parasitology and to science in general was her pioneering research into curbing the disease schistosomiasis (liver flukes), endemic to tropical regions. She made breakthrough discoveries regarding the life- and vector cycles of snails key to transmission of the often-fatal disease to humans, thus aiding in reducing the international health costs of the disease.[2] By the time of her retirement, Cram had produced over 160 papers and monographs on various subjects relating to animal parasitology, had become an international authority on helminthic diseases,[3][4] and was working in the NIH's lab on tropical diseases.