Life cycle
The adult Spirometra live in the small intestine of the definitive host—a dog, cat, raccoon, or other mammal—for up to 9 years, where they produce many eggs. When the host defecates, the unembryonated eggs leave the body in the feces and hatch when they reach fresh water. The eggs are eaten by copepods (crustaceans of the genus Cyclops), which are the first intermediate hosts. In the copepods, the eggs develop into procercoid larvae that live in the body cavity. The second intermediate hosts include fish, reptiles, or amphibians that consume the copepods. The larvae penetrate the intestinal tract of the second intermediate host, where they become plerocercoid larvae and proliferate to the subcutaneous tissues and muscles. The second intermediate host is eventually eaten by a definitive host predator, such as a dog, and the cycle begins again. Humans are accidental hosts in the cycle, becoming infected with the plerocercoid larvae by contact with or ingestion of the first or second intermediate hosts. The larvae migrate to the subcutaneous tissues in humans; however, no development takes place and the human is not capable of transmitting the disease. In S. proliferum, many larvae, rather than just a few, proliferate throughout the subcutaneous tissues of humans. Diagnosis
Sparganosis is typically diagnosed following surgical removal of the worms, although the infection may also be diagnosed by identification of eosinophilia or identification of the parasite in a tissue specimen. If such biopsy and excision procedures are not feasible, the antisparganum ELISA test may be used.
If untreated, ocular sparganosis can lead to blindness.In one case of brain infestation by Spirometra erinaceieuropaei, a man sought treatment for headaches, seizures, memory flashbacks and strange smells. Magnetic resonance imaging (MRI) scans showed a cluster of rings, initially in the right medial temporal lobe, but moving over time to the other side of the brain. The cause was not determined for four years; ultimately a biopsy was performed and a 1 cm-long tapeworm was found and removed. The patient continued to have symptoms. Transmission
The parasite is transmitted to humans in three different ways. First, humans may acquire the infection by drinking water that is contaminated with copepods housing Spirometra larvae. Second, humans may acquire the infection by consuming the raw flesh of one of the second intermediate hosts, such as frogs or snakes. For example, humans consume raw snakes or tadpoles for medicinal purposes in some Asian cultures; if the snakes or tadpoles are infected, the larvae may be transmitted to humans. Third, humans may acquire the infection by placing raw poultices of the second intermediate hosts on open wounds, lesions, or the eyes for medicinal or ritualistic reasons. If the poultice is infected with plerocercoid larvae, the human may become infected. According to Zunt et al., human infection most often occurs following ingestion of infected raw snake, frog, or pig, although contact with infected flesh of an intermediate host can also cause infection. The high prevalence in Korea may be explained by the ingestion of dog meat.