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(MUL Parasitology) > 06. Trematodes (Schisto) > Flashcards

06. Trematodes (Schisto) Flashcards

1
Q

What is an example of a blood fluke? where are they found?

A

Schistosoma - in blood vessels

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2
Q

What is an example of a lung fluke? where are they found?

A

Paragonumus - in lungs

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3
Q

Whta is an example of a liver fluke? Where are they found? (5)

A

Largel liver fluke - Fasciola hepatica, Fasciola gigantica
Small liver fluke - Opisthorchis, Chlonorchis, Dicrocoelium

Found in the liver

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4
Q

How many intermediate hosts does Schistosoma have

A

1

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5
Q

What causes Schistosomiasis?

A

human acitivities, water

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6
Q

What are other names for Scistosomiasis?

A

Bilharziasis
Snail fever
Katayama fever

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7
Q

What is common in the geographic areas where schistosomisis is found, in terms of human habits? (3)

A
  • Fresh surface waters are used for bathing or washing
  • waters are contaminated with human feces or urine
  • certain types of snails are present to host the intermediate stages of the parasite
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8
Q

What are the ways in which schisto are unusual trematodes? (4)

A
  1. They are called digeneic trematodes because they have 2 hosts (one intermediate and one definitive) rather than 3+
  2. They are dioecious rather than hermaphroditic
  3. They (the cercaria stage) infect their DH by directly penetrating the body surface rather than being eaten (the other ones it is by eating/drinking water, plants, animals (meat))
  4. They parasitize the intravascular niche (blood vessels, urinary bladder and hepatic portal system)
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9
Q

What kind of uses of water causes infection of schistosomes

A
  • Water used for recreational purposes

- Water used for washing vegetables, fruits, clothes, dishes, etc…

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10
Q

What is the intermediate host of S. mansoni?

A

Biomphalaria

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11
Q

What is the intermediate host od S. haematobium?

A

Bilinus

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12
Q

What is the intermediat host of S. japonicum?

A

Oncomelina

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13
Q

What kind of schistosomiasis is caused by S. mansoni?

A

Intestinal schistosomiasis

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14
Q

Where is the parasite S. mansoni found in infection?

A

the mesenteric vein and the portal venous system

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15
Q

What is the basic pathological lesion of S. mansoni?

A

egg granuloma in the liver and colon

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16
Q

What are characters of acute schistosomiasis?

A

fever
enlarged and tender liver
desentery
eosinophilia

17
Q

What are characters of chronic schistosomiasis?

A

asymptomatic intestinal or symptomatic hepatosplenic

18
Q

What kind of schistosomiasis is caused by S. haematobium?

A

urinary schistosomiasis

19
Q

Where is the parasite S. heamatobium found in infection?

A

the vesical and pelvic plexuses

20
Q

What is the main pathologic lesion of S. haematobium?

A

egg granuloma

21
Q

What is known as a major consequence of urinary schistosomiasis?

A

Squamous cell bladder carcinoma

22
Q

What kind of schistosomiasis is caused by S. japonicum?

A

Oriental schistosomiasis

23
Q

Where is the parasite S. japonicum found in infection?

A

inhabiting the superior and inferior mesenteric veins

24
Q

Which schistosome is the most pathogenic among the ones that can infect humans?

A

S. japonicum

25
Q

Who is infected by S. bovis and where in the world does this occur?

A
  • normally infecting cattle, sheep and goats in Africa

- parts of southern Europe and the Middle East

26
Q

Who is infected by S. rodhaini and where in the world does this occur?

A
  • normally infecting rodent and carnivores

- in parts of Central Africa

27
Q

What is Schistosomaisis’s rank in terms of socio-economic important?

A
  • second after malaria
28
Q

What age group is most often affected by schisto?

A

children under 14

29
Q

What are the symptoms of Schisto?

A
  • Amdominal pain, cough, diarrhea, fever, fatigue
  • Eosinophilia: high eosinophil and granulocyte (WBC) count
  • Skin symptoms: at the start if infection, mild itching and a paplar dermatitis of the feet and other parts after swimming in polluted streams containing cercaris
  • Hepatosplenomegaly: enlargement of both the liver and the spleen (S. mansoni, S. japonicum)
  • Genital sores: lesions that increase vulnerability to HIV infection. Lesions caused by schistosomiasis may continue to be a problem after control of the scistosomiasis infection itself. Early treatment, especially in children, which is relatively inexpensive, prevents the formation of the sores. (S. haematobium)
30
Q

How is a Schisto infection diagnosed?

A

Microscopic examination of:

  • stool - S. mansoni, S. japonicum
  • urine - S. haematobium
31
Q

What are the acute pathologies of Schisto?

A
  • Cercarial dermatitis

- Katayama fever

32
Q

What is Cercarial dermatitis?

A

Skin rash occurs upon massive penetration of skin by cercaria. This can lead to lesions at the site of penetrations

33
Q

What is Katayama fever?

A
  • It is a systemic hypersensitivity reaction against the migrating schistosomua. The disease, which consists of fever, fatigue and muscle pain starts a few weeks or even months after a primary infection
  • Most patients recover spontaneously after 2 to 10 weeks - The disease occurs after a primary exposure
34
Q

What are the chronic pathologies of schistosomiasis?

A
  1. Direct morbidity resulting from pathological changes and clinical manifestations induced by the deposition of eggs in tissues followed by the inflammatory immune reaction. This may cause hepatosplenomegaly, hepatic fibrosis, diarrhea and blood in the stool
  2. Additional morbidity such as anemia and growth retardation
35
Q

What is the pathology of hepatosplenomegaly?

A
  • It is a delayed type of hypersensitivity reaction resulting in severe pathology in the liver
  • It appears to be a necessary host protective response against the soluble egg antigens secreted by the entrapped egg which are hepatotoxic (toxic to the liver)
  • The granuloma consists mainly of a number of T and B lymphocytes, macrophages, eosinophils and other cells of the immune system
36
Q

Describe the immune response to Schosiosomiasis

A
  • Chronic morbidity in schistosomiasis is not due to the adult worms but the immune response of the host to the eggs trapped in tissues
  • The trapped eggs secrete a range of molecules stimulating the CD4+ T-cell (T-helper cell) resulting in the formation of the granulomatous inflammation
  • The T-helper cells secrete IL-13 and when it is bound to its receptor promotes the formation of the granuloma
  • Schistosomes are complex organisms and so is the immune aspect of the host-parasite relationships
  • Schistosomes have developed strategies to manipulate and/or escape the immune response of the host. For example, egg antigens supress cell-mediated immunity

(MUL Parasitology) (10 decks)

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