Rat Tapeworm, Hymenolepis diminuta

The rat tapeworm (Hymenolepis diminuta) is a species of parasitic worm that is classified within the Platyhelminthes phylum. It affects mammals throughout the world, but does not often affect humans. It can reach an average body length between 7.8 and 23.6 inches. The segments and eggs of this species are slightly larger than those of the dwarf tapeworm, which shares its genus.

The life cycle of the rat tapeworm begins when an arthropod consumes the eggs of the species. The digestive fluids of this intermediate host break down the egg and release oncospheres that penetrate through the intestinal lining and develop. Once a rodent, or human, ingests the arthropod, the cysticercoids that were present in the intermediate host develop into worms that will mature and breed within the intestine or bile duct of the definitive host, which is most often a rat. The eggs that the hermaphroditic adult worms produce are released in the feces, continuing the cycle of the species.

One study conducted on a Tenebrio molitor beetle showed that the presence of rat tapeworm cysticercoids might affect an intermediate host’s ability to hide. The study focused on a rat and an infected beetle. The beetle was found to be slower than beetles that were not infected. It was also found to have a high stress level at the time of infection.

Humans found to be infected with a rat tapeworm often show no signs of infection, although some hosts may experience itching, pain, irritability, and eosinophilia. Despite the lack of data supporting a treatment, cases are typically treated with the drug praziquantel, which is known to effectively kill parasites. However, one case was cured by using niclosamide.

Image Caption: Hymenolepis diminuta scolex. Credit: Centers for Disease Control and Prevention/Wikipedia