Introduction to Parasites Flashcards

1
Q

What is a parasite?

A

An organism that lives in another and gets its food at the expense of the host

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2
Q

What parasitic disease causes the most deaths globally?

A

Malaria

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3
Q

What are the 3 classification of parasites?

A
  • Protozoa
  • Helminths
  • Arthropods
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4
Q

What are protozoa?

A
  • Microscopic, unicellular organisms

- Can be free-living or parasitic in nature

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5
Q

How are protozoa transmitted?

A
  • Protozoa that live in human’s intestines= fecal-oral route

- Protozoa that live in blood/tissue=arthropod route

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6
Q

What kind of infection is malaria?

A

Protozoan

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7
Q

Describe malaria.

A
  • Mosquito-borne disease caused by a parasite
  • Patient often experiences fever, chills and flu like symptoms
  • Left untreated they may develop sever complications and die
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8
Q

What is the name of the parasite involved in malaria?

A

Plasmodium spp

P. falciparum has the highest mortality rate

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9
Q

How is malaria diagnosed/

A

-Giesma stained blood fil shows infected red cells
-Thick and thin blood films
Variety of rapid diagnostic testing

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10
Q

Describe the life cycle of plasmodium spp.

A
  • Sporozoites are injected under the skin
  • They travel through th blood and enter the liver
  • They mature in the liver and re-enter circulation as merozoites
  • They invade RBC, multiply and lyse cells
  • Sexual form is then taken up by mosquito
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11
Q

How can the spread of malaria be controlled?

A
  • Insecticide treated mosquito nets
  • Prophylaxis
  • Malaria vaccine currently being researched
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12
Q

What kind of infection is amoebic dysentery?

A

Protozoal

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13
Q

What causes amoebic dysentery?

A

Entamoeba histolytica

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14
Q

What are the clinical signs of amoebic dysentery?

A
  • Diarrhoea with blood/pus
  • Intestinal and extra intestinal infections
  • Liver abscess in late disease
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15
Q

What would be found on microscopy of amoebic dysentery?

A

Cysts in formed stool

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16
Q

What do trophozoites do in amoebic dysentery?

A

Ingest red cells by throwing out pseudopodia

17
Q

What are nematodes?

A

Roundworms

18
Q

What are cestodes?

A

Tapeworms

19
Q

What are trematodes?

A

Flatworms

20
Q

How is enterobiasis diagnosed?

Nematode

A
  • Press adhesive sellotape against perianal region in the morning
  • Ova seen on microscopy
21
Q

Describe Ascaris lumbricoides.

A
  • Nematode
  • Ingested eggs hatch in the intestine
  • Larvae carried by circulation to lungs
  • Swallowed again
  • Adult worms develop in and inhabit small intestine
  • Ova seen in faeces by microscopy
22
Q

What symptoms are usually seen with Ascrais lumbricoides?

A
  • Often asymptomatic
  • Transient pulmonary symptoms in Loefler’s syndrome
  • Mass of worms may obstruct small intestine or common bile duct
23
Q

What are 2 examples of cestodes?

A
  • Taenia saginata (beef)

- Taenia solium (pork)

24
Q

What are the hosts in the Taenia spp?

A
  • Larval cysts ingested in meat (intermediate host)

- Adult tapeworm in human (definitive host)

25
Q

How is the taenia spp diagnosed?

A
  • Tissue cysts in humans infected with T solium- cysticercosis
  • Ova in stools on microscopy
26
Q

What is Echinococcus sp carried by?

Trematode

A

Dogs, wolves and foxes

27
Q

Describe the life cycle of Ecjinococcus.

A
  • Humans ingest eggs (dog faeces)
  • Eggs hatch and enter circulation
  • Hydatid cysts forms in liver
  • Surgical resection must involve whole cyst
28
Q

What is serology?

A

Detection of antibodies

29
Q

What diagnostic principles apply to parasitology?

A
  • Culturing is rarely possible
  • Blood films (thick/thin) for malaria
  • Serology
  • Identification of parasites in host tossue or excreta
  • Microscopy ate P,C and O in faeces
30
Q

What is helminth infection often accompanied by?

A
  • Eosinophilia

- Elevate IgE

31
Q

What can Schistosoma haematobium cause?

A
  • Haematuria

- Bladder cancer

32
Q

What are the 3 major species of Schistosomes?

A
  • S. haematobium (bladder)
  • S. mansoni (intestinal)
  • S. japonicum (intestinal)
33
Q

Describe infection of schistosomiasis.

A

-Eggs excreted in urine or faeces
-Miracidia released in fresh water
-Penetrate body of snail (intermediate host)
-Cercaria emerge from snails after 4-6 weeks
Penetrate human skin
-Migrate through lungs to liver
-Mature in liver into worms that migrate to mesenteric or bladder venules
-Lay eggs that cause inflammation in bladder or intestinal wall
Katayma fever- acute febrile episode

34
Q

What kind of parasite causes schistosomiasis?

A

Trematode