Spirometra erinaceieuropaei

Spirometra erinaceieuropaei is a tapeworm that infects domestic animals and humans. In humans, infection is called sparganosis. S. erinaceieuropaei’s distribution is cosmopolitan, meaning that it can be found nearly anywhere the parasite can complete its lifecycle.^[1] This species is closely related to Spirometra mansonoides, and few morphological differences exist between the two. One difference is that the uterus of S. mansonoides is a “U” shape, but in S. erinaceieuropaei the uterus consists of two sections that resemble horns. The life cycle of both species is very similar.^[2]

In 2014, a British man was found to have been infected by the tapeworm from an unknown cause (possibly a traditional frog meat poultice) while in China.^[3] The parasitic worm was recorded on successive MRI scans of his brain, moving location by about 5 cm before doctors realized it was alive. The 50-year-old first visited doctors in 2008 suffering from headaches, seizures, and memory loss, and complaining that his sense of smell had changed. The 1-cm, ribbon-shaped larval worm was removed during a surgical procedure and the man recovered.^[4]

Genomics

The genome of S. erinaceieuropaei recovered from the patient's brain was sequenced in 2014 and is available through the WormBase ParaSite website.^[5]

Life Cycle

The worm has an interesting lifecycle. The adult worm lives in the small intestine of cats and dogs, where it may grow as long as 1.5 m. Eggs from the worm are passed with the host feces, when they develop into a procercoid larva. This larva may be directly ingested by humans or may enter intermediate hosts which include frogs, birds, snakes, rats, and mice and become a plerocercoid larva. When cats, dogs, foxes, or wolves eat the intermediate host, the worm completes its lifecycle becoming an egg-producing adult. Because humans would normally ingest the worm at the procercoid stage and are not usually eaten by cats and dogs, the human is a dead-end host.^[6]

Pathology

Although humans can get infected with this parasite, they cannot contract it from an infected cat or dog. People cannot get infected by ingesting the eggs, which is what the pet would be shedding. They would have to eat the procercoid stage, which is found in the intermediate hosts. If the meat of an intermediate host, such as chicken, is undercooked and it happens to be contaminated by the parasite, the person can get infected.^[7]

Diagnoses and Treatment

An easy way to determine if an animal is infected with any type of tapeworm is seeing the proglottids in the feces. These are the white segments that break off from the parasite. To determine the type of species, a fecal sample under the microscope to see the eggs would be the best way. The eggs of any Spirometra species are oval in shape with a distinct operculum at one pole. The treatment for S. erinaceieuropaei is the drug praziquantel, which is typical for tapeworm infections.^[8]

See also

• List of parasites (human)

References

• Web Atlas of Medical Parasitology