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2. Foundations of Medicine PoD > Intro to Parasites > Flashcards

Intro to Parasites Flashcards

1
Q

what is a parasite

A

a parasite is an** organism that lives in or on another organism** (host) and derives its nutrients at the expense of this host, very wide range of parasites globally, they can be vectors of infection or cause infection themselves, predominantly a problem of resource-poor countries

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2
Q

Vector

A

an organism which acts as an intermediate host for a parasite, the vector transmits the parasite to the next host

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3
Q

Classification of parsites

3 classes and examples

A
  • protozoa e.g. malaria, amoebae, flagellates
  • helminths (worms) e.g. roundworms, tapeworms, flukes
  • ectoparasites e.g. lice, ticks, mites
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4
Q

How are parasites classified - broadly

A
  • cellular structure
  • life cycle
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5
Q

How are many parasites spread

A

by vectors

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6
Q

What are parasites predominantly a problem of

A

Resource - poor contries (equator/tropical regions)

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7
Q

what are protozoa

A
  • microscopic, single-celled organisms
  • can be free-living or parasitic in nature
  • able to multiply in humans
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8
Q

how are protozoa transmitted

A
  • protozoa that live in a human’s intestine => faecal-oral route
  • protozoa that live in the blood or tissue of humans=> insect vector
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9
Q

Give an example of and explain protozoan infection

A

Malaria: mosquito-bourne disease caused by Plasmodium parasite
* patient often experiences fever, chills and flu-like illness
* Left untreated they may develop severe complications and die

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10
Q

How many plasmodium species are there and which is the deadliest

A

5 plasmodium species- P. falciparum has the highest mortality

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11
Q

Give some fun maleria facts :)

A
  • causes the largest burden of death among all parasitic diseases
  • present throughout the tropics and subtropics
  • preventable disease
  • recognition and appropriate treatment saves lives
  • the complex life cycle of the parasite makes eradication very challenging
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12
Q

Lifecycle of maleria

A
  1. Sporozoites injected by mosquito
  2. Travel through blood and enter liver
  3. Mature in liver and re-enter circulation as merozoites
  4. Invade red cells, multiply and lyse cells - invade more red cells
  5. Sexual forms taken up by mosquito
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13
Q

What can show plasmodium infected red cells (parasitaemia)

A

Specially stained blood film

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14
Q

Is maleria a preventable disease

A

yes

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15
Q

What makes eradicating maleria very challenging

A

The complex lifecycle of the parasite

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16
Q

protozoal infections- amoebic dysentery

A
  • causes bloody diarrhoea
  • entamoeba histolytica invade gut wall
  • microscopy: cysts in formed stool
  • clinically= intestinal and extra-intestinal infections, liver abscess in late disease
  • faecal-oral route of transmission for amoebae
  • Causes infection in variety of body systems - can causes complications such as abscesses if left untreated
17
Q

2 examples of protozoa

A
  • Malaria (plasmodium)
  • entamoeba histolytica
18
Q

types of helminths

A
  • nematodes- roundworms
  • cestodes- tapeworms
  • trematodes- flatworms
19
Q

nematodes

enterobius vermicularis

A
  • Cause enterobiasis (pinworm)- 1cm, threadlike, found in children
  • Cause anal itch, especially at night
  • Diagnosis= Press adhesive sellotape against perianal region in the morning
  • Ova seen on microscopy
  • faecal-oral route of transmission
20
Q

Ascaris lumbricoides

neamatode

A
  • ingested eggs hatch in the intestine - Ova seen in faeces by microscopy
  • largest nematode in humans- adults 15-35 cm
  • Often asymptomatic- may cause failure to thrive in children
  • Mass of worms may obstruct small intestine or common bile duct
21
Q

What is the route of transmission for nematodes (roundworms)

A

fecal-oral

22
Q

Explain ascaris infection (neamatode) further

A
  • very common globally
  • Leads to developmental delay in children
  • Severe complications can arise as a result of bowel obstruction
23
Q

cestodes (tapeworms)

type of helminth

A
  • Long, segmented “tapeworms”
  • Larval cysts ingested (intermediate host)-Eating raw or undercooked meat
  • Adult tapeworms in human (definitive host)
  • Ova in stools on microscopy
  • Product of poor sanitisation/hygine
24
Q

3 types of cestodes

A
  • Taenia saginata (beef)
  • Taenia solium (pork)
  • Echinococcus
25
Q

Echinococcus

tapeworm

A

-Echinococcus sp. - carried by dogs, wolves, foxes
-Humans ingest eggs (dog faeces)
-Eggs hatch and enter circulation
-Hydatid cyst forms in liver- Surgical resection must involve whole cyst

26
Q

What is a route of transmission for cestodes (tapeworms)

A

eating raw/undercooked meat

27
Q

Most common tapeworms

2

A

Beef and pork

28
Q

Pork tapeworm cycts

A

can form outside the gut and cause problems, especially in the brain

29
Q

trematodes

A
  • also known as “flukes” or “flatworms”
  • different species cause human infection in various body sites: blood/lung/liver/pancreas/intestines
  • cause schistosomiasis
30
Q

Schistosomiasis

explain

A

**Three major species of schistosomes: S. haematobium (bladder), S. mansoni (intestinal), S. japonicum (intestinal)
Cases occur near affected fresh water - snails important in life cycle

31
Q

How are trematodes (flukes) transmitted

A

By contact with freshwater where the snail intermediary host is present

32
Q

Complications of trematode infections (schistomiasis)

A

Liver failure and bladder cancer if left untreasted

33
Q

Summarise key points about helminths (worms)

A
  • Heavy burden of disease, especially in resource-poor settings
  • Most are transmitted by faecal-oral route but some use an intermediary host/vector
  • Include: roundworms, flatworms and tapeworms
34
Q

Ectoparasites

A
  • parasites which live outside the body
  • most are insects or arachnids
  • many are vectors of infection
  • Include: flea, tick, lice
35
Q

Definitive diagnosis

A

identification of parasites in host tissue or faeces/urine, e.g. blood microscopy for parasites- thick and thin blood films for malaria

36
Q

enteric pathogens

A

stool microscopy for the following- Ova, cysts and parasites

37
Q

What are signs of helminth (worm) infection

A
  • Eosinophilia
  • Elevated IgE
38
Q

Indirect testing (for parasites)

A
  • Serology (immune testing)
  • Rapid diagnostic tests
39
Q

Diseases caused by enteric and blood-bourne parasites

A
  • Enteric (e.g. roundworms): giardiasis, amoebiasis, cyclosporiasis, and cryptosporidiosis
  • Blood-bourne: African trypanosomiasis, babesiosis, Chagas disease, leishmaniasis, malaria, and toxoplasmosis

2. Foundations of Medicine PoD (28 decks)

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