In the Western hemisphere, the most common cause of infection is drinking contaminated water. Hosts, reservoirs, and vectors
Definitive hosts of Spirometra include dogs, cats, birds, and wild carnivores, while humans are accidental hosts. First intermediate hosts include copepods and other fresh-water crustaceans, while second intermediate hosts include birds, reptiles, and amphibians. The intermediate hosts are also the reservoirs of Spirometra. There are no vectors of Spirometra. Incubation period
The incubation period of Spirometra is 20 days to 3 years. Morphology
The sparganum larvae are white, wrinkled, and ribbon-shaped. They range from a few millimeters in length to several centimeters. The anterior end can invaginate and bears suggestions of the sucking grooves that are present in the scolex of the mature worm. The absence of a scolex or protoscolex in Spirometra is a key difference in differentiating between Taenia solium and Spirometra. The worms body is also characterized by a stromal network of smooth muscle. In general, plerocercoids in the East (S. mansoni) are described as larger and more delicate than those in the West.The eggs of S. mansonoides provide an example of the general morphological characteristics of Spirometra eggs. S. mansonoides eggs resemble the eggs of D. latum, with some specific differences. S. mansonoides eggs measure 57-66 µm by 33-37 µm, which is smaller than the eggs of D. latum. The eggs of S. mansonoides are also ellipsoidal and have a conical, prominent operculum.
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.