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Year 2 Clinical Pathology > Introduction to parasites > Flashcards

Introduction to parasites Flashcards

1
Q

What is a parasite?

A

An organism which lives in or on another organism (its host) and benefits by deriving nutrient’s at the others expense

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2
Q

Do parasites always cause disease?

A

No

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3
Q

What is a parasitic disease?

A

When a parasite derives all benefits from the association with a host and the host may either be harmed or may suffer the consequences of this association

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4
Q

What is meant by symbiosis?

A

A long term interaction between 2 different species

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5
Q

What are the 3 types of symbiosis?

A

1) Mutualism: an association in which both species benefit from the interaction
2) Parasitism: an association in which the parasite derives benefit and the host gets nothing in return but always suffers some injury
3) Commensalism: an association in which the parasite only is deriving benefit without causing injury to the host

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6
Q

What are the 3 classes of host?

A

1) Definitive host
2) Intermediate host
3) Paratenic host

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7
Q

What is a definitive host?

A

Either harbours the adult stage of the parasite or where the parasite utilizes the sexual method of reproduction, in the majority of human parasitic infections, man is the definitive host

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8
Q

What is an intermediate host?

A

Harbours the larval or asexual stages of the parasite

Some parasites require 2 intermediate hosts in which to complete their life cycle

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9
Q

What is a paratenic host?

A

Host where the parasite remains viable without further development

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10
Q

What are the 2 broad categories of parasite?

A

1) Protozoa (micro-parasites)

2) Helminths (macro-parasites)

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11
Q

What are the 4 types of protozoa?

A

1) Flagellates
2) Amoeboids
3) Sporozoans
4) Trypanosomes

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12
Q

What are the 2 types of helminths and what are there 2 sub types?

A

1) Nematodes (round worms)
a) intestinal nematodes
b) tissue nematodes
2) Platyhelminths (flat worms)
a) cestodes (tape worms)
b) trematodes (flukes)

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13
Q

What are the 3 types of parasite life cycle?

A

1) Direct
2) Simple indirect
3) Complex indirect

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14
Q

What is meant by a direct life cycle?

A

Only one host - that is the definitive host
Eg. bird sheds parasite eggs into the environment in faeces, eggs mature in environment and become infective, infective embryonated eggs are eaten by another bird when feeding

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15
Q

What is meant by a simple indirect life cycle?

A

Has 1 intermediate host aswell as a definitive host
eg. bird shed parasite eggs into the environment in faeces, snowbug eats eggs of parasite, egg hatch in snowbug and infective larvae develop within snow bug, bird eats snowbug and becomes infected

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16
Q

What is meant by a complex indirect life cycle?

A

Has more than one intermediate host aswell as a definitive host

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17
Q

Ascariasis is what kind of parasite?

A

Macro-parasite (Helminth) - intestinal nematode (ascaris lumbricoides)

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18
Q

Why is ascariasis such a problem?

A

1 adult worm can produce 200,000 eggs per day

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19
Q

How is ascariasis acquired?

A

Ingestion of eggs

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20
Q

Where is ascariasis most common?

A

Areas of poor hygiene, most common in SE easia

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21
Q

What is the life cycle of ascariasis?

A

Has a direct life cycle
Worm in human intestine, eggs shed into the environment in faeces, eggs are then ingested, they travel in the portal circulation to the lungs where they then hatch and the worms are they swallowed and enter the intestine

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22
Q

Lung migration in Ascariasis causes what syndrome (with what 6 symptoms)?

A

Loeffler’s syndrome - dry cough, dyspnoea, wheeze, haemoptysis, eosinophilic pneumonitis

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23
Q

What are the 4 consequences of the intestinal phase of ascariasis?

A

1) Malnutrition
2) Migration - into hepatobiliary tree and pancreas
3) Intestinal obstruction
4) Worm burden

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24
Q

How is ascariasis diagnosed? 2

A

Microscopy of egg in stool

Presence if worm in stool

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25
Q

What is the treatment of ascariasis?

A

Albendazole
Prevents glucose absorption by worm
Worm starves, detaches and passes PR

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26
Q

What 4 controls have been put in place to reduce cases of ascariasis?

A

WHO ‘Action Against Worms’
Improve sanitation
Education
Community targeted deworming

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27
Q

Shistosomiasis is what kind of parasite?

A

Macroparasite (helminth) - platyhelminth - trematode/fluke

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28
Q

What is schistosomiasis also known as?

A

Bilharzia disease

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29
Q

Where in schistosomiasis most common?

A

Africa

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30
Q

What kind is the life cycle of schistosomiasis?

A

Simple indirect lifecycle with freshwater snails as the intermediate host

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31
Q

Describe the life cycle of schistosomiasis?

A

Eggs are shed in human stools or urine, the eggs hatch and the organism infects freshwater snails by penetrating snail tissue, organism matures in snail then released into water and penetrates human skin
Pass into human circulation, migrate to portal blood in liver and mature into adults which migrate to the mesenteric venules of the bowel/rectum (laying eggs that circulate to the liver and shed in stools) and venous plexus of the bladder.

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32
Q

What are the 4 stages of disease following schistosomiasis infection?

A

1) Swimmers itch (at sight of entry)
2) Katayama fever (can last a couple of weeks)
3) Chronic schistosomiasis (can persist for years)
4) Effects of eggs in distant sites: spine, lung

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33
Q

What are the 3 main effects of urinary schistosomiasis (S. haematobium)?

A

1) Haematuria
2) Bladder fibrosis and dysfunction
3) Squamous cell CA bladder

34
Q

What are the 2 main effects of hepatic/intestinal schistosomiasis?

A

1) Portal hypertension

2) Liver cirrhosis

35
Q

How is urinary schistosomiasis diagnosed? 2

A

1) Terminal stream microscopy

2) Serology

36
Q

How is hepatic/intestinal schistosomiasis diagnosed? 3

A

1) Stool microscopy
2) Rectal snip microscopy
3) Serology

37
Q

What is the treatment of schistosomiasis? 2

A

1) Praziquantel (parazinoisoquinoline derivative)

2) Treatment of long term complications

38
Q

What 4 procedures are put in place to try and control schistosomiasis?

A

1) Chemical treatment to kill snail intermediate hosts
2) Chemoprophylaxis
3) Avoidance of snail infested waters
4) Community targeted treatment, education and improved sanitation

39
Q

Hyatid disease is caused by what kind of parasite?

A

Macroparasite (helminth) - platyhelminth - cestode - tapeworm. Echinococcus sp.

40
Q

What are the hosts in the life cycle of parasite causing hyatid disease?

A

Human is an accidental host

Usual hosts are sheep and dogs

41
Q

Where is hyatid disease found?

A

All over the world wherever sheep are farmed

42
Q

What is the usual lifecycle of the hyatid disease parasite (not involving humans)?

A

Dog has adult worm in intestines and sheds eggs in faeces
These are ingested by a sheep, they hatch and the organism penetrates the sheep intestinal wall and travels to the liver or lungs where it forms a hyatid cyst. Cyst in sheep is ingested by a dog and cycle continues

43
Q

How does a human become the definitive host in hyatid disease?

A

If a human is in contact with a dog or dog faeces they can ingest the eggs

44
Q

What are the clinical effects of hyatid disease? 4

A

1) Cysts form: 70% in liver, 20% in lungs
2) May remain asymptomatic for years
3) Secondary bacterial infection
4) Cyst rupture causing hypersensitivity

45
Q

How is hyatid disease diagnosed? 2

A

1) Imaging (to show cysts)

2) Serology

46
Q

What 3 processes aim to control hyatid disease?

A

1) regularly worm dogs to reduce egg production
2) hang hygiene
3) safe disposal of animal carcasses/ products of conception

47
Q

What type of parasite causes malaria?

A

Plasmodium

Microparasite (protozoa) - sporozoan

48
Q

What are the 4 species of plasmodium that cause malaria, which is most common?

A

1) P. falciparum
2) P. vivax
3) P. ovale
4) P. malariae

49
Q

Roughly how many people are infected with malaria each year?

A

300-500 million people

50
Q

How many deaths are caused by malaria each year?

A

1-3 million deaths per year, mainly in young children

51
Q

What is different about the lifecyle of malaria?

A

It uses vector transmission

Anopheles mosquito acts as the vector

52
Q

Where is malaria most common?

A

Africa

53
Q

What is the plasmodium life cycle causing malaria?

A

Organism infected mosquito takes a blood meal from a human injecting the organism
This travels to liver cells where it replicates until the cell bursts and the organism then infects RBCs, it can continue in a cycle in which it replicates in RBCs causing them to burst and release further organisms to infect further RBCs.
It can also form gametocytes in RBCs which are ingested by another aedes mosquito when it takes a blood meal to form a new organism

54
Q

What is the basic clinical effect of the malaria parasite?

A

It ruptures red blood cells, blocks capillaries and causes an inflammatory reaction

55
Q

What are the 7 possible clinical effects of malaria?

A

1) Fever & Rigors
2) Cerebral malaria (confusion, headache, coma)
3) Renal failure (black water fever)
4) Hypoglycaemia
5) Pulmonary oedema
6) Circulatory collapse
7) Anaemia, bleeding, DIC

56
Q

Returning traveller with a fever is diagnosed as what until proven otherwise?

A

Malaria

57
Q

What 3 processes are carried out in the diagnosis of malaria?

A

1) Thick and thin microscopy
2) Serology - detection of Ag in blood
3) PCR - detection of malarial DNA

58
Q

What 6 processes are carried out which aim to control malaria transmission?

A

1) Insecticide spraying in homes
2) Larvicidal spraying on breeding pools (for aedes mosquito)
3) Filling in of breeding pools
4) Larvivorous species introduced in to mosquito breeding areas
5) Use of insecticide impregnated bed nets
6) Chemoprophylaxis

59
Q

Cryptosporidiosis is caused by what organism (and what kind)?

A

Cryptosporidium parvum and hominis

A micro-parasite (protozoa) - sporozoan

60
Q

How is cryptosporidiosis spread?

A

Faecal-oral route

Human to human spread with animal reservoir (cattle, sheep, goats)

61
Q

Where is cyptosporiodosis most common?

A

World-wide distribution (esp. temperate and tropical)

62
Q

What is the life cycle of cryptosporidiosis?

A

Direct life cycle with no intermediate hosts

Human sheds eggs in faeces which infect water and food, human ingests eggs

63
Q

What is the clinical effect of cryptosporidiosis? 3

A

(Incubation 2-10 days - usually 7)
Watery diarrhoea with mucus (no blood)
Bloating, cramps, fever, nausea, vomiting
Usually self limiting (lasts up to 2 weeks)

64
Q

In which 3 types of people can cryptosporidiosis be severe?

A

1) Very young
2) Very old
3) Immuno-compromised

65
Q

Which people are at risk of human to human spread of cryptosporidiosis? 5

A

1) Regular users of swimming pools
2) Child care workers and parents
3) Nursing home residents/carers
4) Healthcare workers
5) Travellers

66
Q

Which people are at risk of animal-human spread of cryptosporidiosis? 4

A

1) Backpackers, campers, hikers
2) Farm workers
3) Visitors to farms/petting zoos
4) Consumers of infected dairy products

67
Q

How is cryptosporidiosis diagnosed?

A

Faeces sample

1) Acid fast staining
2) Ag detection by EIA

68
Q

How is cryptosporidiosis treated in symptomatic patients? 2

A

1) Rehydration

2) Nitazoxanide

69
Q

How is cryptosporidiosis treated in the immune-compromised? 4

A

1) Paromomycin (to kill parasite)
2) Nitazoxanide (effectiveness is unclear)
3) Octreotide (reduce cramps and frequency)
4) HIV patients, HAART should be quickly initiated

70
Q

How is human to human spread of cryptosporidiosis controlled? 4

A

1) Hand hygiene
2) Filter or boil drinking water
3) Isolate symptomatic pts in healthcare setting
4) Ensure symptomatic children are kept away from school

71
Q

How is animal-human spread of cryptosporidiosis controlled? 2

A

1) Pasteurise milk and dairy products

2) Boil or filter drinking water if camping

72
Q

Name 5 commonly used anti-protozoal treatments?

A

1) Metronizadole
2) Pentamidine
3) Nitazoxanide
4) Pyrimethamine
5) Anti malarials

73
Q

Name 4 commonly used anti helminthic treatements?

A

1) Albendazole
2) Mebendazole
3) Ivermectin
4) Praziquantel

74
Q

Giardia lambila is what kind of protozoa?

A

Flagellate

75
Q

Entamoeba and acanthamoeba are what kind of protozoa?

A

Amoeboids

76
Q

Plasmodium, Cryptosporidium, cyclospora, isospora and toxoplasma are what kind of protozoa?

A

Sporozoans

77
Q

Trypanosoma and leishmania are what kind of protozoa?

A

Trypanosomes

78
Q

Taenia, echinococcus and hymenolepis are what kind of platyhelminth?

A

Cestodes

79
Q

Schistosoma, fasciola, fasciolopsis and paragonimus are what kind of platyhelminth?

A

Trematode

80
Q

Ascaris, trichuris, necator and ancylostoma are what kind of nematode?

A

intestinal nematode

81
Q

Wuchereria, brugia, onchocerca and loa loa are what kind of nematode?

A

tissue nematode

Year 2 Clinical Pathology (64 decks)

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