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Clinical Pathology > Introduction to parasites > Flashcards

Introduction to parasites Flashcards

1
Q

What is a definitive host?

A

Either habours sexual stage of parasite or adult stage. Majority of human parasitic infections.

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2
Q

What is an intermediate host?

A
  • Harbours the larval or asexual stages of the parasite

- Some parasites require two intermediate hosts in which to complete their life cycle

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3
Q

What is a parantetic host?

A

Host where the parasite remains viable without further development.

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4
Q

What is a direct lifecycle?

A

Only one host (definitive).

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5
Q

What is a simple indirect lifecycle?

A

One definitive host and one intermediate host.

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6
Q

What is a complex indirect lifecycle?

A

More than one intermediate host.

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7
Q

What is Ascaris?

A

Intestinal roundworm

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8
Q

What is the route of infection for Ascaris?

A

Faeco-oral - ingestion of eggs from contaminated water.

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9
Q

What kind of lifecycle does Ascaris have?

A

Direct - Human sheds eggs in faeces

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10
Q

What is the lung phase of Ascaris?

A

Loefflers syndrome - dry cough, dyspnea, wheeze, haemoptysis, eosinophilic pneumonitis

Larvae migrate from intestines to alveolae where they are then coughed up and swallowed.

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11
Q

What is the intestinal phase of Ascaris?

A

Malnutrition
Migration – into hepatobiliary tree and pancreas
Intestinal obstruction
Worm burden

Adult worm

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12
Q

What is the treatment/control of Ascaris?

A

Treatment

  • Albendazole
  • Benzimidazole
  • Prevents glucose absorption by worm
  • Worm starves-detaches-passed PR

Control

  • WHO “Action Against Worms”
  • Improve sanitation
  • Education
  • Community targeted deworming
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13
Q

What is the intermediate host of Schistosomiasis?

A

Freshwater snail

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14
Q

What is the clinical progression of schistosomiasis?

A
  • Swimmers itch
  • Katayama fever
  • Chronic Schistosomiasis
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15
Q

What is Katamaya fever?

A

Acute schistosomiasis

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16
Q

What are the signs/symptoms of chronic schistosomiasis?

A
  • Haematuria
  • Bladder fibrosis and dysfunction
  • Squamous cell CA bladder
  • Portal hypertension
  • Cirrhosis
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17
Q

How is schistosomiasis diagnosed?

A

Urinary

  • Terminal Stream Microscopy
  • Serology

Hepatic/Intestinal

  • Stool Microscopy
  • Rectal Snip Microscopy
  • Serology
18
Q

What is the treatment of schistosomiasis?

A
  • Praziquantel (parazinoisoquinoline derivative)
    40-60 mg/kg with food 3 doses 8-hourly
  • Mechanism unknown- increased ionic permeability tetanic contraction, detachment, death
  • Well absorbed, extensive 1st pass metabolism, inactive metabolites excreted in urine

Treatment of long term complications

19
Q

How can schistosomiasis be controlled?

A
  • Chemical treatment to kill snail intermediate hosts
  • Chemoprophylaxis
  • Avoidance of snail infested waters
  • Community targeted treatment, education and improved sanitation
20
Q

What kind of disease is caused by Echinococcus?

A

Hydatid disease

E. multilocularis - alveolar
E. granulosus - cystic

21
Q

What are the usual hosts of Echinococcus?

A

Sheep and dogs

Humans are accidental hosts

22
Q

What kind of lifecycle does Echinococcus have?

A

Simple indirect. Sheep is definitive host, dog is intermediate.

23
Q

What are the clinical features of hydatid disease?

A
  • Cysts: 70% liver, 20% lungs
  • May remain asymptomatic for years
  • Mass effect
  • Secondary bacterial infection
  • Cyst rupture- hypersensitivity
24
Q

How may hydatid disease be controlled?

A
  • Regularly worm dogs to reduce egg production
  • Hand hygiene
  • Safe disposal of animal carcasses/products of conception
25
Q

What are the four species of malaria and which causes the most infections?

A

P. falciparum - 70% of infections
P. vivax
P. ovale
P. malariae

26
Q

Which insect acts as a vector for malaria?

A

Anopheles mosquito

27
Q

What kind of lifecycle does malaria have?

A

Simple indirect. Anopheles definitive host, human intermediate host.

28
Q

What are the clinical features of malaria and what is their cause?

A
  • Fever & Rigors (alt. days with falciparum malaria, every 48hrs or 72hrs with benign malaria)
  • Cerebral malaria (confusion, headache, coma)
  • Renal failure (black water fever)
  • Hypoglycaemia
  • Pulmonary oedema
  • Circulatory collapse
  • Anaemia, Bleeding and DIC

Red blood cells bursting and releasing parasites.
Cyclical fever result of parasite lifecycle (not usually present in falciparum infection).

29
Q

How is malaria diagnosed?

A
  • Thick and thin microscopy
  • Serology - detection of Ag in blood
  • PCR - detection of malarial DNA
30
Q

How might malaria be controlled?

A
  • Insecticide spraying at homes
  • Larvicidal spraying on breeding pools
  • Filling in of breeding pools
  • Introduction of lavivorous species
31
Q

What kind of parasite is cryptosporidium?

A

Sporozoan

32
Q

What mode of spread does cryptosporidium use?

A

Faeco oral

33
Q

What kind of lifecycle does cryptosporidium have?

A

Direct - human host

34
Q

What are the clinical features of cryptosporidium

A
  • Incubation 2-10 days (usually 7 days)
  • Watery diarrhoea with mucus (no blood)
  • Bloating, cramps, fever, nausea, vomiting
  • Usually self-limiting (last up to 2 weeks)
  • Can be severe in:
    • very young
    • very old
    • immuno-compromised (60% HIV patients infected go on to chronic infection- can loose up to 25 litres fluid/day)
35
Q

Which animals may act as a reservoir for cryptosporidium?

A

Cattle, sheep, goats

36
Q

What is a vector?

A

An organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another.

37
Q

What is a reservoir?

A

Any person, animal, plant, soil or substance in which an infectious agent normally lives and multiplies. The reservoir typically harbors the infectious agent without injury to itself and serves as a source from which other individuals can be infected.

38
Q

What kind of parasite is Acariasis?

A

Intestinal nematode

39
Q

What kind of parasite is schistosomiasis?

A

Trematode

40
Q

What is the lifecycle of schistosomiasis?

A

Simple indirect

Clinical Pathology (65 decks)

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