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Clinical Pathology > Theme 1: Lecture 5- Parasites > Flashcards

Theme 1: Lecture 5- Parasites Flashcards

1
Q

What is a parasite?

A
  • an organism which lives in or on another organism (its host) and benefits by deriving nutrients at other expense
  • does not necessarily cause disease
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2
Q

What is a host?

A

an organism which harbours the parasite

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3
Q

What does symbiosis mean?

A

living together; close, long term interaction between two species

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4
Q

What is mutualism?

A

an association in which both species benefit from the interaction

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5
Q

What is parasitism?

A

an association in which the parasite derives benefit and the host gets nothing in return but always suffers some injury e.g ticks feed on animal blood and can also pass on infections to hosts such as lyme disease

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6
Q

What is commensalism?

A

an association in which the parasite only is deriving benefit without causing injury to the host

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7
Q

What are the 4 classes of hosts?

A
  1. definitive host
  2. reservoir host
  3. intermediate host
  4. paratenic host
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8
Q

What is a definitive host?

A
  • where the parasite reaches its mature form and is capable of reproduction
  • either harbours adult stage of parasite or where parasite sexually reproduces
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9
Q

What is a reservoir host?

A

an animal or species infected by a parasite which serves as a source of infection for humans or other species

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10
Q

What is an intermediate host?

A
  • harbours the larval or asexual stages of parasite
  • often acts as a vector of parasite to reach its definitive host
  • host harbours parasite that grows but not to the point of reaching sexual maturity
  • some parasites require two intermediate hosts to complete their life cycle
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11
Q

What is a paramedic host?

A

host where the parasite remains viable without further development

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12
Q

What are the three main types of parasites and their subdivisions?

A
  1. phylum protozoa
    - flagellates
    - ameoboids
    - sporozoans
    - trypanosomes
  2. Platyhelminthes and phylum nemathelminthes
    - flat worms (flukes and tapeworms)
    - round works (nematodes)
  3. phylum arthropoda
    - ectoparasites (lice & mites)
    - blood sucking arthropods
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13
Q

How are protozoa sub-classified?

A
  • flagellates —> giardia lambda, trichomonas vaginalis
  • amoeboids —> entamoeba sp
  • sporozoans —> plasmodium sp, cryptosporidium sp, toxoplasma sp
  • trypanosomes —> trypanosome sp, leishmania sp
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14
Q

What are helminths?

A
  • large multicellular organisms
  • macroparasites
  • ‘worms’
  • adults generally visible by eye
  • adults cannot multiply in humans
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15
Q

What are protozoa?

A
  • micro- parasites
  • single celled organisms
  • can be free-living or parasitic in nature and multiply in humans
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16
Q

How are helminths divided?

A
  1. platyhelminths
    - cestodes (tape worms) e.g taenia sp.
    - trematodes e.g schistosoma sp.
  2. nemates
    - intestinal nematodes
    - ascarias sp.
    - tissue nematodes
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17
Q

What is a platyhelminths?

A

flat worm

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18
Q

What is a nematode?

A

round worm

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19
Q

What are ectoparasites?

A
  • broadly include blood sucking arthropods and those that burrow into skin
  • arthropods are important transmitters of infections
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20
Q

How are ectoparasites divided?

A
  • insects
  • lice
  • mites - scabies sp.
  • arachnids (ticks)
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21
Q

What are the two types of lice parasites?

A
  • pediculus humaus capitus (head lice)

- pthiris pubic (pubic lice)

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22
Q

What are the 3 types of life cycle of a parasite?

A
  1. direct
  2. simple indirect
  3. complex indirect
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23
Q

What is the difference between direct and simple indirect lifestyles?

A

direct- the simple parasite lives their lifespan and reproduces within one host
indirect - the complex parasite lives in many hosts

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24
Q

What is ascariasis and what is it caused by?

A
  • macroparasite: intestinal nematode
  • caused by ascaris lumbricoides, species of roundworm
  • acquired by ingestion of eggs
  • more than 1 billion people affected worldwide
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25
Q

What are the clinical effects of ascariasis?

A
  • lung migration (loefflers syndrome)- dry cough dyspnoea, wheeze, haemoptysis, eosinophilic pneumonitis
  • intestinal phase - malnutrition, malabsorption, migration, intestinal obstruction, worm burden
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26
Q

How do we treat ascariasis?

A

albendazole

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27
Q

How does albendazole treat ascariasis?

A

prevents glucose absorption by worm

worm starves, detaches, passed out

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28
Q

What is schistomiasis?

A
  • macro-parasite (helminth–> platyhelminth—> trematode/fluke)
  • a.k.a “bilharzia”
  • snails are intermediate host
  • causes chronic disease resulting in bladder cancer and liver cirrhosis
29
Q

What are some examples of schistosomas (flukes)?

A
  • S. haematobium
  • S.mansoni
  • S. intercallatum
  • S.japonicum
  • S.mekongi
30
Q

What are the possible symptoms of schistosomiasis?

A
  • often asymptoatic
  • symptomatic acute infection / katayama syndrome
  • rash, fever, headache, myalgia and respiratory syndrome
  • often with eosinophilia and hepato/splenomegaly
  • swimmers itch
  • katayama fever (rash, eosinophilia)
  • chronić schistosomiasis (can persist for years)
31
Q

What systemic effects/ further risks to schistosomiasis cause?

A
  • undernutrition due to suppression of appetite and inflammation - mediated cachexia
  • anaemia
  • hepatic fibrosis and oesophageal varices
  • renal failure
  • bladder tumours
  • increased risk of transmission of HIV
  • poor birth outcomes in material infection
32
Q

What is a serodiscordant couple?

A

one is HIV+ and one is not

33
Q

How long is the infective incubation period for schistosomiasis?

A

14-84 days

34
Q

What are the two main locations that schistosomiasis will effect?

A
  • urinary system

- hepatic/intestinal

35
Q

What is the treatment of schistosomiasis?

A

praziquantel

36
Q

What is chemoprophylaxis?

A

using drugs to prevent disease, causes resistance

37
Q

Where does S. haematobium cause schistosomiasis?

A
  • urinary
  • haematuria
  • bladder fibrosis and dysfunction
  • squamous cell CA bladder
38
Q

Which types of schistosomiasis cause hepatic/intestinal disease?

A
  • S.mansoni
  • S. intercallatum
  • S. japonicum
  • S. Mekongi
39
Q

What is hydatid disease?

A
  • macroparasite (platyhelminth–> cestode/tapeworm—> echinococcus sp)
  • usual host are sheets and dogs, humans are accdiental
  • caused by echinococcus sp
40
Q

What are the clinical effects of hydatid disease?

A
  • cysts: 70% in liver, 20% in lungs
  • may remain asymptomatic for years
  • cyst rupture: hypersensitivity
  • secondary bacterial infection
41
Q

What is the treatment for Hyatid disease?

A

albendazole and praziquantel

42
Q

What is malaria?

A
  • micro-parasite

- protozoa —> sporozoan—> plasmodium sp

43
Q

What are the 4 human species of plasmodium?

A
  1. P.falciparum
  2. P.vivax
  3. P. ovale
  4. P. malariae
    + P. knowlesi (monkey species)
44
Q

What are the clinical effects of malaria?

A
  • parasites rupture red cells, block capillaries, cause inflammation reaction
  • fevers and rigors
  • confusion —> headache—> coma
  • renal failure (black water fever)
  • hypoglycaemia
  • pulmonary oedema
  • circulatory collapse
  • anaemia, bleeding and DIC
45
Q

If a returning traveller has a fever, what condition is assumed until prove otherwise?

A

malaria

46
Q

What is the erythrocytic cycle of plasmodium?

A
  • 24 hrs: P.knowlesi
  • 48 hrs: P.falciparum, P.vivax, P.ovale
  • 72 hrs: P.malariae
47
Q

What are the treatments of malaria?

A
  • antimalarials
  • oral chloroquine
  • proguanil, primaquine
  • supportive therapy - management of seizures pulmonary oedema, acute renal failure and lactic acidosis
48
Q

What is the most dangerous type of malaria?

A

falciparum malaria - caused by plasmodium falciparum

49
Q

What are the vectors of malaria?

A

anopheles - a genus of mosquitos

50
Q

What is cryptospordiosis caused by?

A
  • cryptosporidium parvum and hominis

- micro-parasite, sporozoan

51
Q

How does cryptospordiosis spread and what is its main symptom?

A
  • human to human spread with animal reservoir (cattle, sheep, goats)
  • faecal-oral spread
  • causes diarrhoeal disease
52
Q

What is the incubation period in cryptospordiosis?

A

2-10 days

53
Q

What are the effects of cryptosporidiosis?

A
  • watery diarrhoea with mucus (no blood)
  • bloating, cramps, fever, nausea, vomiting
  • usually self limiting (resolves on its own)
  • can be severe in very young, old and immunocompromised
54
Q

How do we treat cryptosporidiosis?

A
  • symptmatic: rehydration, nitazoxanide

- paramomycin (kills parasite)

55
Q

What causes trichomoniasis?

A

trichomonas vaginalis

56
Q

What is trichomonas?

A

flagellated protozoan

57
Q

How is trichomoniasis transmitted?

A

sexually

58
Q

What is the incubation period of trichomonas?

A

5-28 days

59
Q

What symptoms do men and women display if infected with trichomoniasis?

A

men - asymptomatic
women - smelly vaginal discharge, dysuria and lower abdominal discomfort, punctuate haemorrhages on cervix “strawberry cervix”

60
Q

How does trichomonas vaginalis multiply?

A

binary fission

61
Q

How do we treat trichomonas?

A
  • metronidazole

- treat partner simultaenously

62
Q

What is auto infection and which parasite can cause it to occur?

A
  • eggs can hatch in GI tract and reinfect

- can occur with strongyloidiasis

63
Q

What is strongyloidiasis hyper infection?

A

rare but fatal disease escalated from strongyloidiasis, usually seen in immunocompromised patients

64
Q

What drug is used to treat strongyloidiasis?

A
  • thiabendazole
  • invermectin (hyper infection)
  • albendazole
65
Q

What is giardiasis and how is it transmitted?

A
  • flagellated protozoan

- faecal oral transmission

66
Q

What are the symptoms of giardiasis?

A

severe diarrhoea, malabsorption, abdominal pain, bloating, nausea, vomiting

67
Q

How do we diagnose giardiasis?

A

identification of cysts or trophozoites in faeces

68
Q

What is the treatment for giardiasis?

A

metronidazole/ tinidazole

69
Q

How do we prevent giardiasis?

A

no vaccine available, hygiene measures, boiling water

Clinical Pathology (57 decks)

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