Sparganosis is a
parasitic infection
A parasitic disease, also known as parasitosis, is an infectious disease caused by parasites. Parasites are organisms which derive sustenance from its host while causing it harm. The study of parasites and parasitic diseases is known as parasitolo ...
caused by the plerocercoid
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
e of the genus ''
Spirometra
''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 th ...
'' including
''S. mansoni'', ''S. ranarum'', ''S. mansonoides'' and ''S. erinacei''.
[John, D.T. and Petri, W.A. Markell and Voge's Medical Parasitology. 9th edition. St. Louis: Saunders Elsevier, 2006.] It was first described by
Patrick Manson
Sir Patrick Manson (3 October 1844 – 9 April 1922) was a Scottish physician who made important discoveries in parasitology, and was a founder of the field of tropical medicine. He graduated from University of Aberdeen with degrees in Master ...
from China in 1882, and the first human case was reported by
Charles Wardell Stiles
Charles Wardell Stiles (May 15, 1867 – January 24, 1941) was an American parasitologist born in Spring Valley, New York. He was notable for working on a campaign against hookworm infestation in the American South, where it had been found to cau ...
from Florida in 1908. The infection is transmitted by ingestion of contaminated water, ingestion of a second intermediate
host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
such as a frog or snake, or contact between a second intermediate host and an open wound or
mucous membrane
A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
.
[Manson, P., Manson-Bahr, P., and Wilcocks, C. Manson's Tropical Diseases: A Manual of the Diseases. New York: William Wood and Company, 1921.] Humans are the accidental hosts in the life cycle, while dogs, cats, and other mammals are definitive hosts.
Copepods (freshwater crustaceans) are the first intermediate hosts, and various amphibians and reptiles are second intermediate hosts.
Once a human becomes infected, the plerocercoid larvae migrate to a
subcutaneous location, where they typically develop into a painful nodule.
[GIDEON, "Sparganosis." Date viewed February 26, 2009](_blank)
/ref> Migration to the brain results in cerebral sparganosis, while migration to the eyes results in ocular sparganosis. Sparganosis is most prevalent in Eastern Asia, although cases have been described in countries throughout the world. In total, approximately 300 cases have been described in the literature up to 2003. Diagnosis is typically not made until the sparganum larva has been surgically removed. Praziquantel
Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of helminthiasis, parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is us ...
is the drug of choice, although its efficacy is unknown and surgical removal of the sparganum is generally the best treatment. Public health interventions should focus on water and dietary sanitation, as well as education about the disease in rural areas and discouragement of the use of poultices.
Symptoms
Clinical presentation of sparganosis most often occurs after the larvae have migrated to a subcutaneous location. The destination of the larvae is often a tissue or muscle in the chest, abdominal wall, extremities, or scrotum, although other sites include the eyes, brain, urinary tract, pleura, pericardium, and spinal canal. The early stages of disease in humans are often asymptomatic
In medicine, any disease is classified asymptomatic if a patient tests as carrier for a disease or infection but experiences no symptoms. Whenever a medical condition fails to show noticeable symptoms after a diagnosis it might be considered asy ...
, but the spargana typically cause a painful inflammatory reaction in the tissues surrounding the subcutaneous site as they grow. Discrete subcutaneous nodules develop that may appear and disappear over a period of time. The nodules usually itch, swell, turn red, and migrate, and are often accompanied by painful edema.[Garcia, L., and Bruckner, D.A. Diagnostic Medical Parasitology. Herndon, VA: ASM Press, 2007.] Seizures, hemiparesis, and headaches are also common symptoms of sparganosis, especially cerebral sparganosis, and eosinophilia is a common sign. Clinical symptoms also vary according to the location of the sparganum; possible symptoms include elephantiasis
Elephantiasis is the enlargement and hardening of limbs or body parts due to tissue swelling. It is characterised by edema, hypertrophy, and fibrosis of skin and subcutaneous tissues, due to obstruction of lymphatic vessels. It may affect the genit ...
from location in the lymph channels, peritonitis
Peritonitis is inflammation of the localized or generalized peritoneum, the lining of the inner wall of the abdomen and cover of the abdominal organs. Symptoms may include severe pain, swelling of the abdomen, fever, or weight loss. One part or ...
from location in the intestinal perforation, and brain abscess
Brain abscess (or cerebral abscess) is an abscess caused by inflammation and collection of infected material, coming from local (ear infection, dental abscess, infection of paranasal sinuses, infection of the mastoid air cells of the temporal bone ...
es from location in the brain. In genital sparganosis, subcutaneous nodules are present in the groin, labia, or scrotum and may appear tumor-like.
Ocular
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and con ...
sparganosis a particularly well-described type of sparganosis. Early signs of the ocular form include eye pain, epiphora (excessive watering of the eye), and/or ptosis (drooping of the upper eyelid). Other signs include periorbital edema and/or edematous swelling that resembles Romana's sign in Chagas disease
Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by ''Trypanosoma cruzi''. It is spread mostly by insects in the subfamily ''Triatominae'', known as "kissing bugs". The symptoms change over the cou ...
, lacrimation, orbital cellulitis, exophthalmos (protrusion of the eyeball), and/or an exposed cornea ulcer. The most common sign at presentation is a mass lesion in the eye. If untreated, ocular sparganosis can lead to blindness.
In one case of brain infestation by ''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 ...
'', a man sought treatment for headaches, seizures, memory flashbacks and strange smells. Magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
(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
A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...
was performed and a 1 cm-long tapeworm was found and removed. The patient continued to have symptoms.[The Guardian newspaper: Man's headaches due to tapeworm living in his brain for four years, 21 November 2014]
/ref>
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 poultice
A poultice, also called a cataplasm, is a soft moist mass, often heated and medicated, that is spread on cloth and placed over the skin to treat an aching, inflamed, or painful part of the body. It can be used on wounds, such as cuts.
'Poultice' ...
s 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. 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
Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of m ...
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 worm's 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.
Life cycle
The adult ''Spirometra'' live in the small intestine
The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the p ...
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 Procercoid is the first larval stage of some tapeworms, which usually develops inside the body cavity of copepods. Flatworm in this stage is not enclosed in a protective cyst, but is infectious. Procercoids resemble their adult forms in pathways of ...
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
The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...
test may be used. In theory, a pre-operative diagnosis could be made by identification of exposure history and a painful, migratory, subcutaneous nodule. Sparganosis usually presents as a single nodule, while other cestode infections such as cysticercosis typically present as multiple nodules. Preoperative diagnosis, however, is rare.
CT and MRI scans are especially useful for diagnosis of cerebral sparganosis, as they reveal lesions in the brain. Through a retrospective analysis of 25 cases of cerebral sparganosis from 2000 to 2006, Song et al. found a number of characteristic signs that could be used in the future to diagnose cerebral sparganosis without performing an excision or tissue biopsy. The most characteristic finding was the "tunnel sign" on MRI images, showing the migrating track of the worm, while the most common finding was multiple conglomerated ring-shaped enhancements, seen as bead-shaped, usually with 3 to 6 rings. These findings led Song et al. to suggest that clinical history, ELISA, and either MRI or CT scans could be sufficient to make a sparganosis diagnosis. These lesions, however, are sometimes mistaken for tuberculosis lesions. In one case cerebral sparganosis was not diagnosed for four years, during which scans showed a cluster of rings moving from the right to the left side of the brain; ultimately the worm was found on biopsy.[
]
Prevention
Because sparganosis is a rare infection, public health strategies have not made its prevention a priority. Public health strategies focusing on providing basic access to clean water may help to reduce future sparganosis infections. In their retrospective study of 25 cases of cerebral sparganosis, Song et al. found that 12 patients (48%) had eaten raw or uncooked frog or snake that was infected with sparganum, 5 patients (20%) had applied an animal's flesh as a poultice to an open wound, 4 patients had drunk contaminated water, and the cause of infection was not known for 4 patients. As a result of these findings, Song et al. conclude that health education about sparganosis and the importance of food sanitation should be implemented in all rural endemic areas.[ It has been recommended that water consumed in endemic areas should be boiled or treated to prevent ingestion of Cyclops or Spirometra larvae. Especially in areas where ponds or ditches provide potential habitats for infected copepods, public health strategies should include education campaigns about how to identify drinking water that could potentially be infected. Strategies should warn people against ingesting the raw flesh of the intermediate hosts, such as snakes and frogs, and against using them as poultices.]
Management
One treatment for sparganosis is praziquantel, administered at a dose of 120 to 150 mg/kg body weight over 2 days; however, praziquantel has had limited success. In general, infestation by one or a few sparganum larvae is often best treated by surgical removal.
DNA analysis of rare worms removed surgically can provide genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
information to identify and characterise each parasite; treatments for the more common tapeworms can be cross-checked to see whether they are also likely to be effective against the species in question.[
]
Epidemiology
Sparganosis is endemic or potentially endemic in 48 countries, and although rare, cases have been described in Asia, Africa, Australia, South America, and the United States. The majority of cases occur in Southeast Asia and Eastern Africa. Ocular sparganosis is especially prevalent in China and Vietnam. The highest numbers of cases occur in Korea and Japan. As of 2003, only seven cases of sparganosis had ever been described in Europe.
History of discovery
Diesing first named the Sparganum genus of cestodes in 1854. Patrick Manson
Sir Patrick Manson (3 October 1844 – 9 April 1922) was a Scottish physician who made important discoveries in parasitology, and was a founder of the field of tropical medicine. He graduated from University of Aberdeen with degrees in Master ...
first reported sparganosis and the species ''Sparganum mansoni'' in China in 1882, while making the post-mortem examination of a man in Amoy, China.[Fantahm, H.B., and Stephens, J.W.W., and Theobald, F.V. The Animal Parasites of Man. New York: William Wood and Company, 1916.] The first case of sparganosis in the United States was reported by Stiles in 1908; this was a case of infection by ''Spirometra proliferum''. Mueller first described ''Spirometra mansonoides'' in the United States in 1935.
References
External links
{{Helminthiases
Parasitic infestations, stings, and bites of the skin
Helminthiases