Tapeworm Identification in the fat sand rat (Psammomys obesus obesus)

The identification of a tapeworm (Rodentolepis nana, formerly named Hymenol epis nana) infection in a research breeding colony of sand rats (Psammomys obesus obesus) was complicated because of the unexpected long length (less than or equal to 150 mm) of the worms. Other morphologic features that were consistent with this identification included the number (24), size (16 mum ), and shape of the hooks on the rostellum. No evidence of intermediate hos ts was found in the colony. Previous surveys of natural population,; of san d rats had not identified this tapeworm. However, a detailed search of the literature revealed that variation in the size of R, nana had been reported , thus supporting the final identification of the tapeworm. R nana is impor tant and interesting because of its zoonotic potential and because it is th e only tapeworm that is able to infect its definitive host without use of a n intermediate host. This report is presented to help clarify the ambiguity found in the laboratory animal literature about the differences in the siz e of R. nana among rodent species used in research.