PRESENTATION OUTLINE
SPIROMETRA Erinaceieuropaei
SPIROMETRA Erinaceieuropaei is a parasitic tapeworm that infects domestic animals and humans. The medical term for this infection in humans and other animals is sparganosis. Morphologically, these worms are similar to other worms in the genus Spirometra. They have a long body consisting of three sections: the scolex, the neck, and the strobilia. They have a complex life cycle that consists of three hosts, and can live in varying environments and bodily tissues. Humans can contract this parasite in three main ways (ingestion of under cooked meat, contaminated water, or poultices contained contaminated flesh).
Historically, humans are considered a paratenic host; however, the first case of an adult S. erinaceieuropaei infection in humans was reported in 2017. Spirometra tapeworms exist worldwide and infection is common in animals, but S. erinaceieuropaei infections are rare in humans. Treatment for infection typically includes surgical removal and anti-worm medication.
Adult Spirometra are typically large worms with long bodies consisting of three distinguishable body sections: the scolex, the neck, and the strobilia. Overall body length can reach up to several meters; however, this can vary depending on host species as well as other factors. The scolex is the spoon shaped anterior portion of the worm and consists of the head with attachments. Instead of hooks and distinct suckers (like most tape worms), S. erinaceieuropaei have two bothria.
Bothria are grooves on the scolex that contain weak muscles that perform a sucking action. The neck is unsegmented and located between the scolex and the rest of the body. The proglottids make up the remainder of the body (everything after the neck), and together are termed the strobilia. As proglottids mature, they develop two sets of reproductive organs, one male and one female. Each proglottid is capable of reproducing via self fertilization.
Eggs are typically ovoid in shape with tapered ends. Finally, should the head and neck be severed from one or all of the proglottids, S. erinaceieuropaei can regenerate a new body.
Diagnostic Features and Laboratory Diagnosis
Infection in humans can be detected via imaging, but because larvae may appear as a mass, most diagnosis occurs after surgical removal. Diagnosis in animals is typically done by characterizing eggs in fecal matter. Since most tapeworm infections within the genus Spirometra have similar egg morphology, species characterization is not typical.
There are three ways in which humans have become infected in the past: 1) Eating raw or under cooked snakes, frogs, and other four footed animals; 2) drinking contaminated water containing infected copepods; and 3) using raw snake or frog flesh in poultices that come in contact with intact human skin (Spirometra larvae have been shown to penetrate skin and cause infection in this manner.) This method was more prevalent in parts of Asia where poultices were used due to superstition.
Diphyllobothroid tapeworm under the genus Spirometra is the causative agent. Humans can be infected through the consumption of contaminated water or meat from intermediate hosts or through topical application of raw, contaminated poultices to eyes and open wounds.
Pathology and Symptomatology
Infection of S. erinaceieuropaei is termed sparganosis. However, this term encompasses the entire genus Spirometra and is not specfic to S. erinaceieuropaei. Sparganosis due to S. erinaceieuropaei is rare. Adults Spirometra typically infect dogs, cats and other carnivores. They will reproduce in their intestines, and the eggs will be shed in their feces. Although humans can get infected with this parasite, they cannot contract it from the feces of an infected cat or dog. Sparganosis refers specifically to the infection with Spirometra larvae and is endemic in animals but a rare condition for humans. In humans, the larvae are typically found in subcutaneous tissues or muscle, and will form slowly growing masses.
Sometimes infection in humans can also involve genitourinary tract, pleural or abdominal cavity, and scrotum. Infection can also involve the central nervous system, but this is even less common. When the central nervous system is involved, symptoms may occur as many as twenty years after infection. These can include weakness, headache, seizures, numbness, tingling, or abnormal skin sensations. Because the masses are typically slow growing, they often resemble tumors on radio graphs. Additionally, larvae may create migratory lesions (also called wandering lesions) within tissue. These lesions are a large sign of infection.
Skin and soft tissue swelling was the most common symptom, followed by central nervous system lesions.
The incubation period is not well-defined, and the parasite may live up to 20 years in the human body. In subcutaneous sparganosis, an incubation period between 1 day and several months has been estimated. In the case presented here, the time and the source of infection remain unclear. The consumption of reptile or amphibian meat was denied. However, the consumption of possibly undercooked chicken or wild boar meat as a source cannot be excluded. The molecular sequence of the isolated sparganum did not provide clues to the locality where the infection was possibly acquired, because there were no sequence differences to Japanese, Chinese, or Korean isolates. Most likely, however, the infection was acquired in Japan, because the patient frequently visited her home country.
The plerocercoid may migrate to any part of the body, but preferred infection sites are the breast, abdomen, scrotum, legs, and central nervous system. The most serious complication is neurosparganosis, which develops in 3.2% of patients. In a recent analysis of parasitic encephalopathies, cerebral sparganosis was seen in 15.4% of cases in China. Pain is often caused when the parasite, which reaches lengths of several centimeters (sometimes up to 18–50 cm) moves in the subcutis or dies. In the case presented, the localization of the helminth was typical, but pain was not reported. It remains unclear whether a possible immunosuppression caused by the breast cancer led to a more rapid development or migration of the parasite or fewer symptoms because of a comparatively undisturbed development.
The S. erinaceieuropaei life cycle is complex and consists of three hosts. The life cycle starts when eggs are discharged via feces from the definitive host. When discharged, the eggs are immature until they reach a fresh water source. Once in fresh water, the eggs hatch to become first stage larvae (coracidia). From here, coracidia are ingested by crustaceans (copepods), which become the first intermediate host. Inside the first intermediate host, the coracidia develop into procercoid larvae; however, this is still considered the first larval stage. Next, copepods are eaten by fish, reptiles, or other amphibians that become the second intermediate host. Inside the second intermediate host, the larvae will burrow into the intestinal tract where they develop into plerocercoid larvae (the final larval stage).
In the final larvae stage, S. erinaceieuropaei migrate to subcutaneous tissues and/or muscles. Finally, the second intermediate host is eaten by a definitive host. A couple of weeks later, S. erinaceieuropaei mature into adult tapeworms and the life cycle continues. Adult tapeworms can survive up to 30 years in their definitive host (typically dogs and cats). The secondary intermediate host can also be eaten by other animals such as primates, pigs, mice, birds, and even humans. These animals become the paratenic hosts.
Animals are usually treated with anti-worm medications, such as Praziquantel (tapeworms in dogs and cats - digestive system). Surgical removal is the most common treatment in humans, as well as treatment by anti-worm medication such as Albendazole (diagnosis and treatment of human spragnosis).
Infection of humans may be prevented by avoiding eating under-cooked frog or fish, and avoiding drinking infected water.
