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91 Cards in this Set
- Front
- Back
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What class of parasites has a flat, oval or leaf-life body shape; an unsegmented body; lacks a body cavity; has a GI tract (but no anus), is hermaphroditic; and all species are parasitic?
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Class Trematoda (flukes)
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What class of parasites are flat, ribbon or band-like; have a segmented body; lack a body cavity; lack a GI tract; is hermaphroditic; and all species are parasitic?
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Class Cestoda (tapeworms)
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What are calcareous corpuscles?
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corpuscles present in the parenchyma of larvae and adults in the Class Cestoda
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What is a scolex?
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The "head" of a tapeworm.
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What are proglottids?
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Immature, mature, and gravid segments of a tapeworm.
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What is a strobila?
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A chain of proglottids constituting the bulk of the body of the adult cestode
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What is a blothrium?
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simple, longitudinal groove on the scolex, tow in number (in Pseudophyllidean tapeworms)
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What is an acetabulum?
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one of the four suction cups with a heavy muscular wall surrounding the head of cyclophyllidean cestodes; used to maintain position in the GI tract.
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What is a rostellum?
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Apical projection of the cestode scolex. May or may not bear hooks.
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What Order of cestodes are uterine pores present?
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Uterine pore is present in Pseudophyllidian cestodes - how they shed eggs.
The uterine pore is absent in Cyclophyllidian cestodes - eggs accumulate in the uterus |
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What is the basic tapeworm life cycle?
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Usually an indirect life cycle with one IH
Adults in SI of definitive host Eggs (Pseudophyllidea) or proglottids containing eggs (Cyclophyllidea) are passed in the feces Eggs ingested by IH and develop into larval stage (metacestode) DH ingests IH containing metacestode - develops into adult |
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The Order Pseudophyllidea (Pseudotapeworms) are primarily parasites of what hosts?
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Birds and fish (associated with aquatic food chain)
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What are characteristics of the Pseudotapeworms that are different from the real tapeworms?
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The scolex has two longitudinal slits called blothria
Possess both a genital and uterine pore Pores are centrally located Eggs are shed rather than proglottids Empty proglottids are shed in feces Eggs are yellow, operculated, contained a single-celled embryo and resemble eggs of Flukes 2 IH are required in the life cycle |
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What are the metacestode types of Pseudotapeworms?
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Egg in water --> coracidium develops in egg --> procercoid develops in first IH --> plerocercoid develops in second IH --> adult
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What are the two pseudotapeworms of importance?
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Diphyllobothrium latum and Spirometra mansonoides
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What is the broad fish tapeworm? It infects humans, bears, canines, felines, and any animal that eats fish, and is found in the host's small intestine.
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Diphyllobothrium latum
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What is the largest tapeworm found in humans? Can grow over 3 feet in length.
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Diphyllobothrium latum
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What is the life cycle Diphyllobothrium latum?
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Adult in host's small intestine lay eggs that are passed in the feces. In water, coracidium develops in the egg, hatches, and is ingested by the first IH (copepod). It develops to a procercoid in the first IH. A second IH (fish) ingests the first, and the procercoid develops to a plerocercoid in the fish's muscles. The DH ingests the fish, and the plerocercoid develops to an adult.
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How are humans most often infected by Diphyllobothrium latum?
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By eating raw or improperly cooked or pickled fish.
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What are the clinical signs of Diphyllobothrium latum?
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in the DH - mild catarrhal enteritis
in humans - can be asymptomatic, can develop abdominal pain, nausea, V/D, and weight loss. Possible vitamin B12 deficiency (B12 is necessary for hemoglobin synthesis; deficiency results in anemia - aka "Norwegian anemia") |
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What is the parasite also known as the zipper tapeworm? It occurs in the small intestine of dogs and cats.
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Spirometra mansonoides
it is called the "zipper tapeworm" because the proglottids often "un-zip" down the center |
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What is the metacestode of Spirometra mansonoides called?
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Sparganum
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What is the life cycle for Spirometra mansonoides?
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Adults occur in the SI of dogs and cats, and eggs are shed in feces. In water, the first IH (copepod) ingests the egg and a procercoid develops. A second IH (fish, frog, water snake, rodent) ingests the copepod and a plerocercoid develops in the muscles. Definitive hosts (dogs, cats) are infected by preying on the second IH. Pre-patent period = 10-30 days.
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What Order's eggs lack an operculum, contain a hexacanth embryo with 6 hooks, and have a membrane surrounding the embryo
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Order Cyclophyllidea - true tapeworms
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What Order's eggs are yellow, operculated, contain a single-celled embryo, and resemble fluke eggs?
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Order Pseudophyllidea - pseudotapeworms
Diphyllobothrium latum Spirometra mansonoides |
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What are some characteristics about the Order Cyclophyllidea (true tapeworms)?
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Terrestrial food chain
adults usually associated with the GI tract scolex has 4 suckers usually armed with hooks and may have a protrusible rostellum Reproductive organs and genital pore(s) located laterally no uterine pore uterus ends blindly and fills with eggs eggs released from proglottids in feces after it is shed and dries out |
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What is the general life cycle of the Order Cyclophyllidea (true tapeworms)?
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egg --> oncosphere --> metacestode --> adult
metacestode type depends on the tapeworm species (cysticercoid, cysticercus, strobilocercus, coenurus, hydatid cyst) |
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Dogs and cats are the definitive host of 4 tapeworm genera, what are they?
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Dipylidium caninum
Taenia species Echinococcus species Mesocestoides species |
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What is the double-pored, flea or cucumber seed tapeworm?
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Dipylidium caninum
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What are the DHs and IHs of Dipylidium caninum?
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DH = canines, felines, children (accidental host that ingests fleas)
IH = fleas or biting louse |
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Are the mature proglottids of Dipylidium caninum longer than wide, or wider than long?
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Longer than wide
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What pores does the proglottid of Dipylidium caninum have?
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2 lateral genital pores (one on each side) because it has 2 sets of reproductive organs.
no uterine pore in true tapeworms! |
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What is a special characteristic of Dipylidium caninum eggs?
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They occur in egg packets / baskets
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Describe the life cycle of Dipylidium caninum.
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Adults in SI shed gravid proglottids in feces that dehydrate, disintegrate and release eggs. Eggs ingested by flea larvae. Cysticercoids develop and persist in adult flea. Adult flea ingested by dog (or child). Cysticercoid released, scolex attaches to SI. Develops to adult tapeworm. Pre-patent period = 3 weeks.
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What is the metacestode type found with Dipylidium caninum?
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Cysticercoid
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What are the clinical signs associated with Dipylidium caninum infection?
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Usually considered non-pathogenic
Anal pruritus ("scooting") |
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How do you diagnose a Dipylidium caninum infection?
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gravid proglottids found on perianal area or in feces (resemble cucumber seeds)
centrifugal flotation in sugar solution (detection of eggs requires proglottid in fecal sample that was broken up or has disintegrated to release eggs) False negatives do occur |
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Describe the mature and gravid proglottids of the Taenia species.
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Longer than wide
single lateral genital pore on either side |
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Describe the two metacestodes found in Teania species.
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Cysticercus in most species - single fluid-filled cyst containing one protoscolex, semitransparent. Found in omentum, mesentery, serosal surfaces of organs.
Coenurus - single fluid-filled cyst; contains multiple protoscolices. Location varies with species. |
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Describe the life cycle of Taenia species.
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Adults in carnivore SI, proglottids containing eggs are shed in feces. IH (usually a herbivore or omnivore) ingests eggs. A cysticercus develops in IH tissues (or coenurus or storbilocercus in some species!). Carnivore DH ingests tissues of IH containing larval tapeworm. Adult develops in SI from larval protoscolex.
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What are the clinical signs of the metacestodes in the Taenia species?
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Cysticerci usually no clinical disease (but can result in condemnation of meat, organs for human consumption)
Coenurus depends on the location (can cause pressure atrophy and necrosis) |
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What two Taenia species have a public health significance?
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Taenia solium - man and pig cycle
Taenia saginata - man and cattle cycle humans are the DH! |
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What is the life cycle of Taenia solium?
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Adults in SI of humans. Proglottids shed in feces and release eggs. Pigs ingest eggs. Eggs hatches in pig intestines, larvae penetrate gut wall and enter blood. Cycticercus infective to man in 10 weeks. Humans eat cysticercus in undercooked pork. Cysticercus excysts and develops to adult in SI.
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What does the metacestode of Taenia solium (cysticercus cellulosae) cause in swine (pigs are the IH)?
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Swine measles or measly pork
Infected pigs are asymptomatic Causes condemnation of meat No method for ante-mortem diagnosis Prevent humans from defecating in pig pens! |
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What does the metacestode of Taenia solium (cysticercus cellulosae) cause in humans (humans are normally the DH)?
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Humans can also become IH if infected by ingestion of food contaminated with human feces. Cysticerci commonly found in the subcutaneous tissue, eye, and brain. Cysticerci that develop in CNS produce mental distrubances, clinical signs of epilepsy or loss of vision. This is called neurocysticercosis.
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What is the significance of Taenia saginata?
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More common in 3rd world countries
Called beef measles or cysticercosis in cattle cycsticerci in striated muscle (heart, tongue, diaphragm, masseters) results in beef condemnation for human consumption human ingests cysticerci in undercooked or raw beef. Pre-patent period = 3 months |
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What does the metacestode of Taenia saginata (cysticercus bovis) cause in cattle (cattle are the IH)?
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cysticerci are initially semitransparent
they become opaque/white as fibrous connective tissue surrounds them infective in 10-12 weeks after egg is ingested remain infective in cattle for 9 months then calcify cause no clinical signs in ruminant! |
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What is the Taenia species where the DH are dogs and wild carnivores, and the IH are sheep and goats?
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Taenia ovis
metacestode = cysticercus ovis |
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What is the Taenia species where the DH are dogs and wild carnivores, and the IH are sheep, other ruminants, and pigs? The cysts are known as "waterballs".
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Taenia hydatigena
metacestode = cysticercus tenuicolis |
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What is the most common taeniid tapeworm of dogs in the US? IH are rabbits, hares and rodents.
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Taenia pisiformis
metacestode = cysticercus - develops in liver and peritoneal cavity of rabbits |
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What is the Taenia species where the DH is a cat and IH are rodents?
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Taenia taeniaeformis
no clinical signs associated with infection metacestode = strobilocercus (develops in rodent liver after rodent eats feces of infected cat) |
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What is the Taenia species also known as the Gid Worm and causes neurological signs of blindness, circling, and head-pressing (condition known as "Gid" or "Staggers")?
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Taenia multiceps
DH = canines IH = sheep, goats, cattle metacestode = coenurus - larva develops in brain Humans can also be an IH - become infected by ingesting eggs from feces of infected dogs. |
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Describe Echinococcus proglottids.
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Too small to be observed grossly.
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What is the Echinococcus metacestode?
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Hydatid cyst.
E. granulosus - unilocular hydatid cyst E. multilocularis - mutlilocular hydatid cyst |
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Describe the life cycle of Echinococcus granulosus.
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DH = domestic and wild canines
IH = sheep, cattle, swine, moose, caribou, kangaroos, humans Adults in SI of DH. Gravid proglottids containing eggs are shed in the feces. Eggs ingested by IH. Oncosphere hatches, penetrates gut wall into blood, carried to viscera. Usually lodges in capillary beds of liver or lungs. Develops into an unilocular hydatid cyst that produces protoscolices. The protoscolices develop to adults if ingested by DH. |
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Describe the life cycle of Echinococcus multilocularis.
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DH = foxes, dogs, cats
IH = voles, lemmings, cattle, horses, swine, humans Multilocular (alveolar) hydatid cyst is formed in the liver of IH that ingests eggs from feces of infected canines. Cysts can "bud" scolices from both internal and external surfaces. External budding not contained by host connective tissue. Progressive proliferation with invasion of host tissues similar to a neoplasm. Secondary cysts can develop at other sites if protoscolices metastasize. Hydatid cyst really infiltrates the host tissues - really impossible to remove. |
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What is the public health importance of Echinococcus species?
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They are zoonotic. Humans can be an IH by ingesting eggs from feces of pet dog of fox.
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What are the clinical signs caused by an Echinococcus infection?
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Clinical signs depend upon size and location of hydatid cyst. A growing hydatid cyst can cause pressure atrophy and necrosis of surrounding tissue. Hydatid cyst can leak or rupture and cause an allergic reaction to hydatid fluid. Metastasis of infection and development of secondary hydatid cysts can occur.
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What is the parasite that has proglottids similar to sesame seeds, infects wild and domestic canines and felines, and has an unknown life cycle with two IH's?
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Mesocestoides species
Two IH's - first is unknown, probably oribatid mites. Second is an amphibian, rodent, reptile or bird. DH = wild or domestic canines and felines Dogs and cats can be both DH and/or second IH |
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Describe the scolex of the adult Mesocestoides.
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Scolex has 4 suckers and a rostellum with no hooklets.
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Describe the mature or gravid proglottids of Mesocestoides species.
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Small, resemble sesame seeds
many proglottids will be in feces contain a single set of reproductive organs 1 medially located genital pore parauterine organ - prominent structure that is centrally located, thick-wall and barrel shaped, contains a number of eggs |
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What species has a parauterine organ?
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Mesocestoides species
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What are the larval metacestode stages found with Mesocestoides species?
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1st IH - cysticercoid
2nd IH - tetrathyridium Tetrathyridium - elongated larva with solid body and invaginated scolex with 4 suckers |
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What species has tetrathyridium as one of their metacestodes?
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Mesocestoides species
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Describe the life cycle of Mesocestoides species.
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Adults in SI release gravid proglottids into the feces. 1st IH believed to be a coprophagous mite which ingests egg that develops into a cysticercoid. 2nd IH believed to ingest 1st IH where cysticercoid develops into a tetrathyridium. The tetrathyridium is infective to the DH. Pre-patent period in dogs is 16-46 days.
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What is special about the reproduction of Mesocestoides species?
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They can reproduce asexually in the small intestine. If all adults are not eliminated by anthelmintic treatment, they can repopulate the gut. Can be difficult to clear infection.
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What species causes Canine Peritoneal Larval Cestodiasis (CPLC)?
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Mesocestoides species
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How does Canine Peritoneal Larval Cestodiasis (s)CPLC) occur?
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The dog acts as an IH
Mesocestoides larvae in peritoneal cavity Tetrathyridia can multiply asexually Large numbers can occur in peritoneal cavity |
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What clinical signs does Canine Peritoenal Larval Cestodiasis cause?
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Episodic, non-specific GI signs that develop over time:
ascites, anorexia, V/D, weight loss, depression, fever, abnormal body position (front legs down, rear legs up), abdomen painful and distended |
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What would you see on abdominal radiographs and ultrasound in a CPLC case?
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Rads: generalized loss of detail consistent with free abdominal fluid; groung glass appearance
U/S: free abdominal fluid with hyperechoic material; small, anechoic, cystic and septate structures in cavity |
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How do you diagnose CPLC?
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Abdominocentesis (false negatives can occur if larvae is walled off in pockets)
Examine abdominal fluid: cloudy with flocculent material with tapioca-like consistency. Cytology - mixed inflammatory exudate with tetrathyridia containing calcareous corpuscles |
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What are the 3 species of equine cestodes?
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Anoplocephala magna (biggest)
Anoplocephala perfoliata Paranoplocephala mamillana (smallest) |
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What are the DH and IH hosts of equine cestodes?
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DH = intestine of horses
IH = free-living mites |
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What are common features of equine cestode adults and proglottids?
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Large, unarmed scolex with 4 suckers
Proglottids wider than long with 2 sets of reproductive organs |
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What are features of equine cestode eggs?
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Hexacanth embryo
embryophore with pyriform apparatus |
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What species has eggs with a pyriform apparatus?
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The equine cestodes
Anoplocephala magna Anoplocephala perfoliata Paranoplocephala mammillana And the ruminant cestodes Moniezia species Thysanosoma actinoides |
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What is the size and location of Anoplocephala magna?
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Located in the horse SI
Largest horse tapeworm (1-3 feet long) Relatively harmless |
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What is the size and location of Anoplocephala perfoliata?
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Located in the cecum and ileocecal valve of horses
2-3 inches long Has two lappets below scolex Associated with colic |
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What horse tapeworm is associated with colic?
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Anoplocephala perfoliata
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What is the size and location of Paranoplocephala mamillana?
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Located in the horse SI
Less than 2 inches long Relatively harmless |
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Describe the life cycle of equine cestodes.
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Adults in intestine that shed gravid proglottids in the feces. Eggs ingested by oribatid mite (IH). Cysticercoid develops in mite and becomes infective in 2-4 months. Horse ingests mite. Cysticercoid protoscolex attaches to host intestine and develops to adult. Pre-patent period = 4-6 weeks.
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What are the species of ruminant cestodes?
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Moniezia species: M. benedeni - cattle; M. expansa - sheep and goats
Thysanosoma actinoides - sheep and cattle |
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What are the hosts of ruminant cestodes and where are the cestodes located?
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DH = ruminants
IH = forage mite Located in SI |
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Describe ruminant cestode adults.
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Unarmed scolex (no hooks or rostellum)
2 sets of reproductive organs per proglottid Proglottids wider than long |
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Describe ruminant cestode eggs.
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Square to tetrahedral
contain a pyriform apparatus |
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What is the life cycle of ruminant cestodes?
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Indirect between ruminant and mite. Adults in SI shed mature segments containing eggs in feces. Eggs released when segment disintegrates. Eggs eaten by mites and develop to infective cysticercoid larva in 1-4 months. Mite is ingested with forage and larva is released and develops into an adult.
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Are ruminant cestodes pathogenic?
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No.
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Describe Thysanosoma actinoides adults.
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Fringed tapeworm
About 12 inches long Segments are short (wider than long) Obvious fringe on caudal edge of each proglottid |
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What parasites have egg baskets?
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Dipylidium caninum
Thysanosoma actinoides |
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Where are adult Tysanosoma actinoides found?
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SI, bile and pancreatic ducts
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What are lesions seen with Thysanosoma actinoides infection?
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Bile duct hyperplasia and fibrosis
Liver condemnation at slaughter |
