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PARA424 > lecture 5 > Flashcards

lecture 5 Flashcards

1
Q

what are the species within the genera Taenia, Echinococcus

A

Echinococcus granulosus and Echinococcus multilocularis

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2
Q

what hosts do the small taeniidae tapeworms (Echinococcus spp.) infect?

A

domestic dogs and other Canidae as definitive hosts

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3
Q

what is the accidental host of Echinococcus spp.?

A

humans

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4
Q

what disease does Echinococcus spp. cause in humans?

A

hydatid disease

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5
Q

what is the egg morphology of echinococcus spp.?

A

round egg that contains distinct rings, radial striations, and hooklets

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6
Q

what is the main feature of hydatid cyst?

A

protoscolices

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7
Q

how long is the echinococcus spp tapeworm?

A

3-6 mm long

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8
Q

what is the adult morphology of the echinococcus tapeworm?

A

consists of a scolex, neck, immature proglottid, mature proglottid, and gravid proglottid (only one segment of each)

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9
Q

what is the life cycle of E. granulosus?

A
  1. adult tapeworm is in the canine small intestine
  2. the gravid proglottid detaches and ruptures in the large intestine as it passes through the digestive tract. the eggs are released in the feces
  3. eggs are released on soil and are ingested by the intermediate host (sheep, cattle, pigs, horses)
  4. the oncosphere hatches in the intermediate host’s intestine, penetrates the gut, enters circulation, and reaches liver, lungs, or brain
  5. oncosphere transforms into a hydatid cyst (requiring months to mature) that is filled with millions of protoscolices
  6. when the herbivore is eaten by canine, the protoscolex, released from the hydatid cyst, develops into adult tapeworms in the canine’s small intestine
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10
Q

what is the life cycle of E. multilocularis?

A
  • its the same life cycle as E. granulosus but the definitive hosts are foxes, and to a lesser extent dogs, cats, coyotes, and wolves. the intermediate hosts are small rodents
  • larval growth (in the liver of the intermediate host) remains indefinitely in the proliferative stage, resulting in invasion of the surrounding tissues
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11
Q

how are humans part of the life cycle when they become an accidental host of E. granulosus/E. multilocularis?

A

ingest the eggs, resulting in the release of oncospheres in the intestine and the development of cysts in various organs. this is known as echinococois or hydatid disease

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12
Q

where does E. granulosus occur?

A

worldwide, more frequently in rural and grazing areas where dogs ingest organs from infected animals

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13
Q

where does E. multilocularis occur?

A

the northern hemisphere, including central Europe and the northern parts of
Europe, Asia, and North America

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14
Q

what form of echinococcus does E. granulosus cause?

A

cystic echinococcus

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15
Q

what form of echinococcus does E. multilocularis cause?

A

alveolar echinococcus

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16
Q

what stage of Echinococcus cestodes (tapeworms) is responsible for human echinococcosis?

A

the larval stage

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17
Q

what are the clinical aspects of Echinococcus granulosus?

A
  1. infection remains silent for years until cysts are large enough to cause symptoms in the affected organs (liver and lungs)
  2. rupture of the cysts can cause fever and anaphylactic shock, as well as cyst dissemination
  3. the infection can also affect the brain, bone, and heart
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18
Q

what are the clinical aspects of Echinococcus multilocularis?

A

affects the liver as a slow growing, destructive tumour, with abdominal pain, biliary obstruction, and occasionally metastatic lesions into the lungs and brain

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19
Q

what is the diagnosis for Echinococcosis?

A

ultrasonography and/or other imaging techniques supported by positive serologic tests

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20
Q

what is the treatment for Echinococcosis?

A

surgery followed by the drug of choice, which is albendazole

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21
Q

how does albendazole treat Echinococcosis?

A

causes degenerative alterations in the tegument and intestinal cells of the worm by binding to tubulin, which inhibits its assembly into microtubules

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22
Q

what are the two species under the family Hymenolepididae?

A
  1. hymenolepis nana - dwarf tapeworm
  2. hymenolepis diminuta- rat tapeworm
    - these two species are the ones that infect humans
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23
Q

what are the intermediate hosts of the family Hymenolepididae?

A

invertebrates

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24
Q

how is the Hymenolepididae family characterized?

A
  • characterized by proglottids that are wider than they are long
  • mature proglottids contain a small number of testes (3 to 4)
  • gravid proglottids disintegrate in host and release eggs
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25
Q

what is the hymenolepis nana also known as?

A

dwarf tapeworm

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26
Q

what are the reservoir hosts of hymenolepis nana?

A

rodents

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27
Q

does hymenolepis nana need an intermediate host

A

not necessarily because an intermediate host to complete its life cycle

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28
Q

how many proglottids does the hymenolepis nana have? where do they live?

A

150-200 proglottids, and lives in the lumen of the small intestine

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29
Q

what is the scolex morphology of hymenolepis nana?

A

scolex has four suckers and a single row of hooks

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30
Q

what is the life cycle of the hymenolepis nana?

A
  1. eggs are immediately infective when passed with the stool and cannot survive more than 10 days in the external environment
  2. when eggs are ingested by an arthropod intermediate host, they develop into cycticercoids, which can infect humans or rodents upon ingestion and develop into adults in the small intestine.
  3. when eggs are ingested (via contaminated food or water or from hands contaminated with feces), the oncospheres contained in the eggs are released
  4. the oncospheres (hexacanth larvae) penetrate the intestinal villus and develop into cysticercoid larvae
  5. upon rupture of the villus, the cysticercoids return to the intestinal lumen, evaginate their scoleces, attach to the intestinal mucosa and develop into adults that reside in the small intestine producing gravid proglottids
  6. eggs are passed in the stool when released from proglottids through its genital atrium or when proglottids disintegrate in the small intestine
    - an alternate mode of infection consists of internal autoinfection, where the eggs release their hexacanth embryo, which penetrates the villus, continuing the infective cycle without passage through the external environment
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31
Q

hymenolepis diminuta are also known as…

A

the rat tapeworm

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32
Q

who is mainly infected by hymenolepis diminuta?

A

children

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33
Q

what is the scolex morphology of H. diminuta?

A

four suckers and no hooks

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34
Q

what are the reservoir hosts of H. diminuta?

A

many reservoir hosts, including dogs, cats and many rodent species

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35
Q

what is the life cycle of H. diminuta?

A
  1. eggs are passed out in the feces of the infected definitive host (rodents, humans)
  2. the mature eggs are ingested by an intermediate host (various arthropod adults or larvae), and oncospheres are released from the eggs and penetrate the intestinal wall of the host, which develop into cysticercoid larvae
  3. the cysticercoid larvae persist through the arthropod’s morphogenesis to adulthood
  4. H. diminuta infection is acquired by the mammalian host after ingestion of an intermediate host carrying the cysticercoid larvae
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36
Q

what is the life cycle of H. diminuta in humans (accidental host)?

A
  1. humans can be accidently infected through ingestion of insects in precooked cereals, or other food items, and directly from the environment
  2. after ingestion, the tissue of the infected arthropod is digested releasing the cysticercoid larvae in the stomach and small intestine. evagination of the scoleces occurs shortly after the cysticercoid larvae are released
  3. using the four suckers on the scolex, the parasite attaches to the small intestine wall
  4. maturation of the parasites occurs within 20 days and the adult worms can reach an average of 30cm in length
  5. eggs are released in the small intestine from gravid proglottids that disintegrate after breaking off from the adult worms. the eggs are expelled to the environment in the mammalian host’s feces
37
Q

what is the species under Family Dipylidiidae?

A

Dipylidium caninum - dog/cat tapeworm

38
Q

Dipylidium caninum is also known as…

A

the double-pored dog tapeworm

39
Q

what is the characteristic of Dipylidium caninum’s proglottid?

A

the proglottids of the adult have genital pores on both sides (hence the name douple-pore tapeworm)

40
Q

what is the intermediate host of Dipylidium caninum?

A

a flea

41
Q

what is the definitive host of Dipylidium caninum?

A

mainly cats and dogs

42
Q

the uterus of Dipylidium caninum breaks down into ___, each containing several eggs with oncospheres

A

egg capsules

43
Q

how are the egg capsules released from the proglottids of Dipylidium caninum?

A

the gravid proglottids break free and pass out in the feces

44
Q

what is the morphology of Dipylidium caninum scolex as an adult cestode?

A

the scolex has a rostellum with four rows of hooks, along with four suckers

45
Q

what is the life cycle of Dipylidium caninum?

A
  1. gravid proglottids are passed intact in the feces or emerge from the perianal region of the host. subsequently they release typical egg packets. on rare occasions, proglottids rupture and egg packets are seen in stool samples
  2. following ingestion of an egg by the intermediate host, an oncosphere is released into the flea’s intestine
  3. the oncosphere penetrates the intestinal wall, invades the insect’s hemocoel (body cavity), and develops into a cysticercoid larva
  4. the adult flea harbours the infective cysticercoid
  5. the vertebrate (definitive) host becomes infected by ingesting the adult flea containing the cysticercoid
    - the dog is the principal definitive host for Dipylidium caninum. other potential hosts include cats, foxes, and humans
46
Q

what is the life cycle of Dipylidium caninum in humans?

A
  1. humans acquire infection by ingesting the cysticercoid contaminated flea. This can be transmitted by close contact between children and their infected pets.
  2. in the small intestine of the vertebrate host the cysticercoid develops into the adult tapeworm which reaches maturity about 1 month after infection
  3. the adult tapeworms reside in the small intestine of the host, where they attach by their scolex
  4. they produce proglottids (or segments) which have two genital pores
  5. the proglottids mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool.
47
Q

what are the two species under the Order Pseudophyllidea?

A

Diphyllobothrium latum & Spirometra mansonoides (Diphyllobothrium mansonoides)

48
Q

what is the distribution of Pseudophyllidea?

A

worldwide

49
Q

what are the scolex characteristics of order Pseudophyllidea?

A

scolex contains two grooves (a.k.a bothria)

50
Q

what are the bothria of Pseudophyllidea?

A

the slit-like adhesive organs. these pinch the intesinal wall to hold the cestode in place in the gut

51
Q

Pseudophyllidea: male and female genital openings are ___ and located ____ in the mature proglottid (not a common genital pore)

A

separate

mid-ventrally

52
Q

the __ __ do not separate from the remainder of the worm but rather remain _____ and __ __ into the gut through a uterine pore and are passed in the feces.

A
  • gravid proglottids
  • attached
  • shed eggs
53
Q

life cycles of Pseudophyllidea are complex involving __ or more hosts

A

3

54
Q

what are the three hosts of Pseudophyllidea?

A
  1. first intermediate host: copepod
  2. second intermediate host: fish/amphibian
  3. definitive host: fish-eating mammal
55
Q

where is Pseudophyllidea most prevalent?

A
  • in the northern hemisphere

- human infections are common in the Great Lakes region of North America and in Northern Europe, particularly Finland

56
Q

what is the common name for Diphyllobothrium latum?

A

the broad fish tapeworm

  • broad, indicated that the proglottids are wider than long
  • fish, indicates that the definitive host is infected by eating raw or poorly cooked fish
57
Q

what are the definitive hosts of Diphyllobothrium latum?

A

bears, dogs, foxes, mink, raccoons, walruses, seals, and humans

58
Q

what are common second intermediate hosts of Diphyllobothrium latum?

A

fish in the great lakes

59
Q

why are bears common definitive hosts of Diphyllobothrium latum?

A

because of their fish-eating habits

60
Q

why are dogs and cats defintive hosts of Diphyllobothrium latum?

A

because sometimes they’re fed scraps of fish

61
Q

how do humans become infected by Diphyllobothrium latum?

A

by eating raw or undercooked fish

62
Q

what are the three common types of fishes that humans eat that contain Diphyllobothrium latum?

A
  • gefilte fish (Scanadanavian)
  • sushi and sashimi (Japanese)
  • cerviche (Latin American)
63
Q

what are the egg characteristics of Diphyllobothrium latum?

A
  • oval or ellipsoidal and range in size from 55 to 75 micrometers by 40 to 50 micrometers
  • there is an operculum (lid) at one end that can be inconspicuous, and at the opposite end is a small knob that can be barely discernible
  • eggs are passed in the stool unembryonated
64
Q

what is the scolex morphology of Diphyllobothrium latum?

A

2 slit-like grooves

65
Q

what is the Diphyllobothrium latum’s life cycle?

A
  1. immature eggs are passed in feces. under appropriate conditions, the eggs mature and yield oncospheres which develop into a coracidia
  2. after ingestion by a suitable freshwater crustacean, the coracidia develop into procercoid larvae
  3. following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae
  4. the plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection
  5. after ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms which will reside in the small intestine
  6. the adults of the Diphyllobothrium latum attach to the intestinal mucosa by means of the two bilateral grooves (bothria) of their scolex
  7. immature eggs are discharged from the proglottids and are passed in the feces
66
Q

Spirometra mansonoides is a cestode found in ____ (location)

A

North America

67
Q

what is the name of the human disease caused by Spirometra mansonoides?

A

sparganosis

68
Q

what are the definitive hosts of Spirometra mansonoides?

A

dogs, cats, birds, and wild carnivores

69
Q

what is the accidental host of Spirometra mansonoides?

A

humans

humans are NEVER the definitive host

70
Q

what are the first intermediate hosts of Spirometra mansonoides?

A

copepods and other fresh-water crustaceans

71
Q

what are the second intermediate hosts of Spirometra mansonoides?

A

fish, reptiles, amphibians, birds and rodents.

72
Q

the intermediate hosts of Spirometra mansonoides are also _____ of Spirometra

A

reservoirs

73
Q

the Spirometra mansonoides adult tapeworm is morphologically similar to ______

A

Diphyllobothrium latum

74
Q

most human cases of sparganosis are recorded from _____ countries

A

Southeast Asian

75
Q

Sparagonis is endemic in ____ throughout North America; human cases from this area are rare

A

animals

76
Q

what is the Spirometra mansonoides life cycle?

A
  1. adult members live in the intestines of dogs and cats
  2. eggs are shed in feces and embryonate in the environment
  3. eggs hatch in water and release coracidia, which are ingested by copepods
  4. the coracidia develop into procercoid larvae in the copepod intermediate host
  5. second intermediate hosts, including fish, reptiles, amphibians, birds, and rodents, ingest infected copepods and acquire procercoid larvae
  6. the procercoid larvae develop into plerocercoid larvae in the second intermediate host
  7. the cycle is completed when a predator (dog or cat) eats an infected second intermediate host
77
Q

how do humans acquire sparganosis?

A
  • by either drinking water contaminated with infected copepods or consuming the flesh of an under-cooked second intermediate host
  • once a human becomes infected, the plerocercoid larvae migrate to a subcutaneous location
78
Q

migration to the brain (of sparganosis) results in ____ _____

A

cerebral sparganosis

79
Q

migration to the eye (of sparaganosis) results in ___ ____

A

ocular sparganosis

80
Q

how long can Spargana live in the human host for

A

up to 20 years

81
Q

what is the drug of choice for most tapeworm infections?

A

praziquantel

82
Q

what other drugs besides praziquantel, can be used for tapeworm infections?

A

niclosamide and albendazole

83
Q

what does the drug specifically target in tapeworm infections?

A

the adult worm

84
Q

anthelmintic drugs essentially kill the tapeworm and the eggs inside of it with ___ dose

A

one

85
Q

what is the mode of action of praziquantel?

A
  • involve the increase membrane permeability of calcium ions; this includes contraction of the parasites resulting in paralysis in the contracted state
  • majority of adult tapeworms are then digested and are not found in the feces; partially digested pieces of tapeworms may be seen in the stool
86
Q

what is the difference between niclosamide and praziquantel

A

niclosamide is used specifically to treat cestodes unlike praziquantel that can be used for cestode and trematode infections

87
Q

what is niclosamide’s mode of action?

A

thought to block ATP production by uncoupling oxidative phosphorylation in the tapeworm

88
Q

what are the characteristics of the drug, Albendazole?

A
  • broad spectrum, effective against adult cestodes, trematodes, and nematodes
  • a member of the benzimidazole compounds
  • first line of treatment against Echinococcus granulosus
89
Q

what does benzimidazole do?

A

binds beta-tubulin, preventing its polymerization with alpha-tubulin to form microtubules. the loss of microtubules leads to reduced uptake of glucose and depletes the glycogen stores of the parasite

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