Spirometra erinaceieuropaei

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Spirometra erinaceieuropaei
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Cestoda
Order: Diphyllobothriidea
Family: Diphyllobothriidae
Genus: Spirometra
Species:
S. erinaceieuropaei
Binomial name
Spirometra erinaceieuropaei
(Rudolphi, 1819) Mueller, 1937

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. [1] 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. [2] They have a complex life cycle that consists of three hosts, and can live in varying environments and bodily tissues. [3] Humans can contract this parasite in three main ways (ingestion of under cooked meat, contaminated water, or poultices contained contaminated flesh). [4] [5] Historically, humans are considered a paratenic host; however, the first case of an adult S. erinaceieuropaei infection in humans was reported in 2017. [6] [7] Spirometra tapeworms exist worldwide and infection is common in animals, but S. erinaceieuropaei infections are rare in humans. [8] [9] Treatment for infection typically includes surgical removal and anti-worm medication. [10] [11]

Contents

Morphology

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. [2] 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. [12] 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. [13] 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. [14] Eggs are typically ovoid in shape with tapered ends. [15] Finally, should the head and neck be severed from one or all of the proglottids, S. erinaceieuropaei can regenerate a new body. [14]

Life cycle

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. [3] [6] 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). [1] 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. [7]

Geographical distribution

Spirometra parasites are found worldwide. Most human cases are recorded from Southeast Asia; however, there are a significant number of animal cases in North America. [8]

Transmission to humans

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. [4] [5]

Historically, humans have been identified as paratenic hosts for larvae; however, the first recorded infection by an adult S. erinaceieuropaei was reported in Vietnam in 2017. For this case, a 23-year-old male was admitted to the hospital with fever, weight loss, and gastric discomfort. Parasite eggs were discovered in his feces and were original thought to be from flukes. As a result, the patient was prescribed anti-worm medication. Two days later, proglottids were viewed in the patients stool. The species of the worm was identified as S. erinaceieuropaei via morphological and molecular methods. The patient fully recovered and was released from the hospital several days later. [6]

Pathology

Infection of S. erinaceieuropaei is termed sparagnosis. [8] However, this term encompasses the entire genus Spirometra and is not specific to S. erinaceieuropaei. Sparagnosis due to S. erinaceieuropaei is rare. [9] Adults Spirometra typically infect dogs, cats and other carnivores. [16] They will reproduce in their intestines, and the eggs will be shed in their feces. [17] Although humans can get infected with this parasite, they cannot contract it from the feces of an infected cat or dog. [18] Sparagnosis refers specifically to the infection with Spirometralarvae and is endemic in animals but a rare condition for humans. [8] In humans, the larvae are typically found in subcutaneous tissues or muscle, and will form slowly growing masses. [16] 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. [19] These can include weakness, headache, seizures, numbness, tingling, or abnormal skin sensations. [16] Because the masses are typically slow growing, they often resemble tumors on radio graphs. [19] Additionally, larvae may create migratory lesions (also called wandering lesions) within tissue. These lesions are a large sign of infection. [19]

Diagnoses and treatment

Infection in humans can be detected via imaging, but because larvae may appear as a mass, most diagnosis occurs after surgical removal. [16] [8] [9] 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. Animals are usually treated with anti-worm medications, such as Praziquantel. [10] Surgical removal is the most common treatment in humans, as well as treatment by anti-worm medication such as Albendazole. [11]

Genomics

The genome of S.erinaceieuropaei recovered from a patient's brain in 2014, was sequenced and is available through the WormBase ParaSite website. [1] [9]

See also

Related Research Articles

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Diphyllobothrium is a genus of tapeworms which can cause diphyllobothriasis in humans through consumption of raw or undercooked fish. The principal species causing diphyllobothriasis is D. latum, known as the broad or fish tapeworm, or broad fish tapeworm. D. latum is a pseudophyllid cestode that infects fish and mammals. D. latum is native to Scandinavia, western Russia, and the Baltics, though it is now also present in North America, especially the Pacific Northwest. In Far East Russia, D. klebanovskii, having Pacific salmon as its second intermediate host, was identified.

Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or H. diminuta. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a neglected tropical disease.

<i>Taenia solium</i> Species of Cestoda

Taenia solium, the pork tapeworm, belongs to the cyclophyllid cestode family Taeniidae. It is found throughout the world and is most common in countries where pork is eaten. It is a tapeworm that uses humans as its definitive host and pigs as the intermediate or secondary hosts. It is transmitted to pigs through human feces that contain the parasite eggs and contaminate their fodder. Pigs ingest the eggs, which develop into larvae, then into oncospheres, and ultimately into infective tapeworm cysts, called cysticercus. Humans acquire the cysts through consumption of uncooked or under-cooked pork and the cysts grow into an adult worms in the small intestine.

Spirometra is a genus of pseudophyllid cestodes that reproduce in canines and felines, but can also cause pathology in humans if infected. As an adult, this tapeworm lives in the small intestine of its definitive host and produces eggs that pass with the animal's feces. When the eggs reach water, the eggs hatch into coracidia which are eaten by copepods. The copepods are eaten by a second intermediate host to continue the life cycle. Humans can become infected if they accidentally eat frog legs or fish with the plerocercoid stage encysted in the muscle. In humans, an infection of Spirometra is termed sparganosis.

<i>Taenia</i> (tapeworm) Genus of flatworms

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<i>Taenia saginata</i> Species of flatworm

Taenia saginata, commonly known as the beef tapeworm, is a zoonotic tapeworm belonging to the order Cyclophyllidea and genus Taenia. It is an intestinal parasite in humans causing taeniasis and cysticercosis in cattle. Cattle are the intermediate hosts, where larval development occurs, while humans are definitive hosts harbouring the adult worms. It is found globally and most prevalently where cattle are raised and beef is consumed. It is relatively common in Africa, Europe, Southeast Asia, South Asia, and Latin America. Humans are generally infected as a result of eating raw or undercooked beef which contains the infective larvae, called cysticerci. As hermaphrodites, each body segment called proglottid has complete sets of both male and female reproductive systems. Thus, reproduction is by self-fertilisation. From humans, embryonated eggs, called oncospheres, are released with faeces and are transmitted to cattle through contaminated fodder. Oncospheres develop inside muscle, liver, and lungs of cattle into infective cysticerci.

<i>Echinococcus granulosus</i> Species of flatworm

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<i>Echinococcus multilocularis</i> Species of flatworm

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<i>Dipylidium caninum</i> Species of flatworm

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<i>Hymenolepis nana</i> Species of flatworm

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<i>Taenia pisiformis</i> Species of flatworm

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<span class="mw-page-title-main">Eucestoda</span> Subclass of flatworms

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<span class="mw-page-title-main">Cestoda</span> Class of flatworms

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