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Principles of Disease-Megan > Introduction to Parasites > Flashcards

Introduction to Parasites Flashcards

1
Q

What is a parasite

A

An organism that lives in another organism (host) and gets its food at the expense of this host
They are simple organisms but more complex than bacteria and consist of a wide range of pathogens

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2
Q

Where can parasites cause infections

A

Tropics
Subtropics
Temperate climated

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3
Q

What parasitic disease causes the most deaths globally

A

Malaria

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4
Q

What are the three main groups of parasites

A

Protozoa
Helminths (worms)
Arthropods

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5
Q

What type of organisms are classified as protozoa

A

Malaria
Amoebae
Flagellates

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6
Q

What type of organisms are classified as helminths (worms)

A

Roundworms
Tapeworms
Flukes

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7
Q

What type of organisms are classified as arthropods

A

Lice
Ticks
Mites

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8
Q

What are protozoa

A

Microscopic one celled organisms
Can be free-living or parasitic in nature
Can multiply in humans

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9
Q

How can protozoa be transmitted

A

Fecal-oral route

Arthropod vector

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10
Q

Why type of protozoa use the fecal-oral route transmission

A

Protozoa that live in a human’s intestine

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11
Q

Why type of protozoa use the arthropod vector transmission

A

Protozoa that live in the blood or tissue of a human

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12
Q

What are roundworms also known as

A

Nematodes

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13
Q

What are tapeworms also known as

A

Cestodes

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14
Q

What are flatworms also known as

A

Trematodes

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15
Q

How can a definitive diagnosis be made

A

From the identification of parasites in the host tissue or excreta should be obtained
Using microscopy to identify the different stages (i.e. parasites, cysts and ova) in the faeces

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16
Q

Why should serology be used instead of a culture

A

Culture is rarely possible

Serology can be useful to detect antibodies (e.g. when parasite is located in deep tissue sites

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17
Q

Give examples of protozoan infections

A

Malaria
Amoebic Dysentery
Leishmaniasis

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18
Q

What is malaria

A

A mosquito-borne disease (uses Anopheles mosquito as its vector) caused by a parasite

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19
Q

What do patients with malaria normally experience

A

Fever
Chills
Flu-like illnesses
If left untreated they may develop severe complications and die

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20
Q

How many types of the plasmodium species are there which can cause malaria

A

4

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21
Q

Which plasmodium species has the highest mortality rate for malaria

A

P. falciparum

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22
Q

What types of blood films will be used for malaria

A

Thick and thin giemsa stained blood films will show the infected red cells

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23
Q

What are parasite infected red blood cells called

A

Parasitaemia

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24
Q

Describe the life cycle for malaria

A

Sporozoites are injected under the skin by the mosquito
This travels through the blood and will enter the liver where it matures and re-enters the circulation as merozoites
They invade red cells, multiply and lyse to reinvade more red cells

25
Q

What happens to the crescent shaped gametocytes produced in the malaria life cycle

A

They are taken up by the mosquito

26
Q

How can malaria be prevented

A

Use of insecticide treated mosquito nets (ITNs)

Prophylaxis

27
Q

How many cases of amoebic dysentery are there a year

A

200-400 million cases/yr

100,000 deaths/yr

28
Q

What is amoebic dysentery

A

An infection which causes diarrhoea with blood/pus

The trophozoite ingests red cells by removing pseudopodia (‘hot stool’)

29
Q

When are the symptoms of amoebic dysentery most common

A

During an infection by Entamoeba histolytica

30
Q

What can be seen under a microscope in amoebic dysentery

A

Cysts formed in the stool

31
Q

What does Entamoeba histolytica cause clinically

A

Intestinal and extra-intestinal infections

Liver abscess filled with reddish-brown pus in late disease

32
Q

How many Leishmaniasis species are there

A

Several

33
Q

What can the Leishmaniasis species cause

A

Cutaneous or muco-cutaneous Leishmaniasis

Visceral Leishmaniasis

34
Q

What can Cutaneous or muco-cutaneous Leishmaniasis cause

A

Skin or mucosal ulceration

35
Q

What can visceral Leishmaniasis cause

A

Fever
Weight loss
Hepato-splenomegaly

36
Q

What is the Leishmaniasis species infection caused by

A

Sand-fly bite

37
Q

How can a Leishmaniasis species infection be diagnonised

A

Through the histology of biopsied materials

38
Q

Give examples of nematodes

A

Enterobiasis

Ascaris lumbricoides

39
Q

How does enterobiasis present and where is it mainly found

A

1cm
Threadlike
Found in children

40
Q

How can enterobiasis be diagnosed

A

By pressing adhesive sellotape against the perianal region in the morning
By seeing ova under a microscope

41
Q

How do ascaris lumbricoides work

A

Through their ingested eggs which hatch in the intestines
The larvae are carried through circulation into the lungs and swallowed again causing adult worms to develop in and inhibit the small intestine

42
Q

How can ascaris lumbricoides be diagnosed

A

Ova can be seen in faeces by microscopy

43
Q

State some features of ascaris lumbricoides

A

Largest nematode in the human intestine measuring between 15-35 cm in length
Often asymptomatic but can cause transient pulmonary symptoms (Loefller’s syndrome).
Mass of worms can obstruct the small intestine or common bile duct

44
Q

Where can cestodes be found

A

Taenia saginata (beef) Taenia solium (pork)

45
Q

How does cestodes enter taenia saginata (beef) and taenia solium (pork)

A

Larval cysts are ingested in the meats which act as intermediate hosts

46
Q

What is the adult tapeworm caused by larval cysts definitive host

A

Humans

47
Q

What are tissues cysts in humans infected with T. solium called and how do they occur

A

Cysticercosis

Through the ingestion of T. solium eggs

48
Q

How can T. solium be diagnosed

A

Ova in stools on microscopy

49
Q

What is the echinococcus species (tapeworms) carried by

A

Dogs
Wolves
Foxes

50
Q

How does the echinococcus species enter the human body

A

Humans ingest eggs through dog faeces
The eggs hatch and enter circulation
A hydatid cyst forms in liver

51
Q

How must the cyst caused by the echinococcus species be removed

A

Surgical resection which must remove the whole cyst

52
Q

What is Trematodes Schistosomiasis and how many species are there

A

A type of helminths

3 main ones

53
Q

What are the three main species of Schistosomiasis

A

S. haematobium (bladder)
S. mansoni (intestinal)
S. japonicum (intestinal)

54
Q

Where are Schistosomiasis found in high quantities

A

Fresh water

55
Q

What is important for the Schistosomiasis life cycle

A

Snails

56
Q

Describe the Schistosomiasis life cycle

A

The Schistosomiasis eggs (ova) are excreted in urine or faeces
Miracidia is released in freash water
They penetrate the body of a snail, which acts as an intermediate host
Cercaria emerge from the snails after 4-6 weeks
They then penetrate human skin causing swimmer’s itch and migrate through the lungs to the liver.
In the liver they mature into worms (schistosomes) which migrate to mesenteric or bladder venules to lay eggs which cause inflammation in the bladder or intestinal wall

57
Q

What is the most severe kind of schistosomiasis

A

Schistosoma japonicum

58
Q

What does schistosoma haematobium cause

A

Haematuria

Bladder cancer

59
Q

What is a helminth infection normally accompanied by

A

Eosinophilia

Elevated IgE

Principles of Disease-Megan (41 decks)

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