Diphyllobothrium mansonoides
Encyclopedia
Diphyllobothrium mansonoides (also known as Spirometra mansonoides) is a species of tapeworm (cestodes) that is endemic to North America. Infection with D. mansonoides in humans can result in sparganosis
. Justus F. Mueller first reported this organism in 1935. D. mansonoides is similar to D. latum and Spirometra erinacei. When the organism was discovered, scientist did not know if D. mansonoides and S. erinacei were separate species. PCR analysis of the two worms has shown the two to be separate but closely related organisms.
The scolex is the head of the cestode, and it functions as a holdfast organ that is specialized to attach to intestines using a variety of mechanisms.
Posterior to the scolex is the neck, which is an unsegmented, poorly differentiated region. The neck is where asexual reproduction
of proglottid segments occurs. Proglottid segments are individual sets of reproductive organs that compose the rest of the cestode body.
The most posterior section of the cestode body consists of multiple strobila, each being made up of several proglottids. There are 3 stages that proglottids go through in their maturation. The first proglottid stage is the immature stage, characterized by functional reproductive organs. The immature stage is the most anterior proglottid, and consists of anywhere between 200 to 300 proglottids. The mature proglottid is located medially to the other proglottids, and is reproductively functional and hermaphroditic. The most posterior proglottid is the gravid stage, and it is packed with eggs. These eggs are eventually released from the gravid proglottid either through a pore in the proglottid or by disintegration of the proglottid.
Cestodes also have sensory organs in the scolex that detect tactile stimulation. The sensory organs are attached to longitudinal nerves that run along the body and are attached to organs.
and along the Gulf Coast. D. mansonoides is found in freshwater. The eggs, coracidia and copepods (1st intermediate hosts) inhabit freshwater. The plerocercoids are found in the muscles of hosts. The adult stage is found in various organs (CNS
, eye, muscles, etc) of the definitive host (cat, dog, birds, and other mammals).
is a fuzzy coat that absorbs host enzymes and inhibits host proteases.
. Sparganosis is the development of plerocercoids in tissues. There are several routes of human infection:
A biopsy
of the infected area is conducted to identify the pathogen. Surgical removal of the tapeworm is usually the best method. However, drugs like praziquantel
can be administered to treat the infection.
A study was conducted on free-range Florida panthers on the effectiveness of anthelmintic treatment. In the study, the intensity of infection of S. mansonoides increased 6 months after treatment instead of decreasing.
Sparganosis
Sparganosis is a parasitic infection caused by the plerocercoid larvae of diphyllobothroid tapeworms belonging to the genus Spirometra. First described by Manson in 1882, the infection is transmitted by ingestion of contaminated water, ingestion of a second intermediate host such as a frog or...
. Justus F. Mueller first reported this organism in 1935. D. mansonoides is similar to D. latum and Spirometra erinacei. When the organism was discovered, scientist did not know if D. mansonoides and S. erinacei were separate species. PCR analysis of the two worms has shown the two to be separate but closely related organisms.
General Characteristics
Cestodes have a dorso-ventrally flattened shape. Cestodes are segmented worms, and their bodies are divided into three distinct regions: the scolex, the neck, and the strobila.The scolex is the head of the cestode, and it functions as a holdfast organ that is specialized to attach to intestines using a variety of mechanisms.
Posterior to the scolex is the neck, which is an unsegmented, poorly differentiated region. The neck is where asexual reproduction
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
of proglottid segments occurs. Proglottid segments are individual sets of reproductive organs that compose the rest of the cestode body.
The most posterior section of the cestode body consists of multiple strobila, each being made up of several proglottids. There are 3 stages that proglottids go through in their maturation. The first proglottid stage is the immature stage, characterized by functional reproductive organs. The immature stage is the most anterior proglottid, and consists of anywhere between 200 to 300 proglottids. The mature proglottid is located medially to the other proglottids, and is reproductively functional and hermaphroditic. The most posterior proglottid is the gravid stage, and it is packed with eggs. These eggs are eventually released from the gravid proglottid either through a pore in the proglottid or by disintegration of the proglottid.
Cestodes also have sensory organs in the scolex that detect tactile stimulation. The sensory organs are attached to longitudinal nerves that run along the body and are attached to organs.
Distribution
D. mansonoides is typically found in the southern US. It is especially common in FloridaFlorida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
and along the Gulf Coast. D. mansonoides is found in freshwater. The eggs, coracidia and copepods (1st intermediate hosts) inhabit freshwater. The plerocercoids are found in the muscles of hosts. The adult stage is found in various organs (CNS
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, eye, muscles, etc) of the definitive host (cat, dog, birds, and other mammals).
Digestion/Metabolism
Cestodes have no digestive tract, and instead, they absorb nutrients along their tegument, which contains microvilli and glycocalyxes. The microvilli are used to absorb nutrients. The glycocalyxGlycocalyx
Glycocalyx is a general term referring to extracellular polymeric material produced by some bacteria, epithelia and other cells. The slime on the outside of a fish is considered a glycocalyx. The term was initially applied to the polysaccharide matrix excreted by epithelial cells forming a...
is a fuzzy coat that absorbs host enzymes and inhibits host proteases.
Life cycle
- The adult dog or cat drops eggs, which hatch between 9 to 120 days. The coracidium exit the egg through the operculumOperculumOperculum may refer to:*Operculum , a stiff structure resembling a lid or a small door that opens and closes**Operculum , a lid on the shell of some gastropods**Operculum , a lid on the orifice of some bryozoans...
, a cap in the egg.
- The coracidium is ciliated and swims around in the water, where it is ingested by a copepod.
- The coracidium then sheds its ciliated epithelium, penetrates the midgut wall of the copepod, and develops into the infective procercoid after 18 days.
- The copepod is the 1st intermediate hostIntermediate hostA secondary host or intermediate host is a host that harbors the parasite only for a short transition period, during which some developmental stage is completed. For trypanosomes, the cause of sleeping sickness, humans are the primary host, while the tsetse fly is the secondary host...
.
- The procercoid cause the copepod to be sluggish, making it susceptible to be ingested by a 2nd intermediate host, often a frog, snake, or mammal.
- The procercoid penetrates the gut wall and enters the muscles or connective tissues. The procercoid then develops into the plerocercoid.
- The 2nd intermediate host is then eaten by either the definitive host (the bobcat) or a secondary definitive host (a dog or cat). The adult penetrates the intestinal wall and enters the muscles, where it absorbs nutrients.
- Humans can acquire the parasite by ingesting an infected copepod from drinking contaminated water or by eating infected secondary definitive hosts. Therefore, humans can act as 2nd intermediate hosts or paratenic hosts.
Disease and Treatment
Infection with Diphyllobothrium mansonoides results in sparganosisSparganosis
Sparganosis is a parasitic infection caused by the plerocercoid larvae of diphyllobothroid tapeworms belonging to the genus Spirometra. First described by Manson in 1882, the infection is transmitted by ingestion of contaminated water, ingestion of a second intermediate host such as a frog or...
. Sparganosis is the development of plerocercoids in tissues. There are several routes of human infection:
- When a human mistakenly eats or drinks the procercoid-containing copepod, becoming the 2nd intermediate host.
- When a human ingests the plerocercoid-containing 2nd intermediate host (frog or snake). The human then becomes the paratenic host.
- When a human uses the 2nd intermediate host as a poulticePoulticeA poultice, also called cataplasm, is a soft moist mass, often heated and medicated, that is spread on cloth over the skin to treat an aching, inflamed, or painful part of the body. It can be used on wounds such as cuts...
on the skin, vagina, or eyes.
A biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
of the infected area is conducted to identify the pathogen. Surgical removal of the tapeworm is usually the best method. However, drugs like praziquantel
Praziquantel
Praziquantel is an anthelmintic effective against flatworms. Praziquantel is not licensed for use in humans in the UK; it is, however, available as a veterinary anthelmintic, and is available for use in humans on a named-patient basis....
can be administered to treat the infection.
A study was conducted on free-range Florida panthers on the effectiveness of anthelmintic treatment. In the study, the intensity of infection of S. mansonoides increased 6 months after treatment instead of decreasing.