5 Parasites

Question 1

Define: parasite.

Answer 1

An organism which lives in or on another organism and benefits by deriving nutrients at the other’ s expense.

Question 2

Differentiate between symbiosis, mutualism and commensalism.

Answer 2

S: Close, long term interaction.
M: Both species benefit.
C: Parasite derives benefit without harming host.

Question 3

What are the three classes of host?

Answer 3

Definitive: harbours adult stage/parasite sexually reproduces
Intermediate: harbours laval/asexual stages of parasite
Paratenic: parasite remains viable without further development

Question 4

What are the four types of protozoa (micro-parasites)?

Answer 4

Flagellates.
Amoeboid’s.
Sporozoa.
Trypanosomes.

Question 5

What are the two types of helminths (macro parasites)? What are the two subdivisions of these?

Answer 5

Platyhelminths (flatworms): cestodes (tapeworms), trematodes (flukes).
Nematodes (round worms): intestinal and tissue.

Question 6

Which parasite causes ascariasis? How is it acquired and where is it found? What type of host is the human?

Answer 6

Ascaris lumbricoides.
Ingestion of eggs (faeces).
S.E. Asia
Definitive.

Question 7

Ascariasis migrates to two places in the body - where? What does it cause there?

Answer 7

Eggs to Lung: Loefflers syndrome - cough, wheeze, heamoptysis, eosinophilic pneumonitis
Worms to Intestines: malnutrition, obstruction

Question 8

How is ascariasis diagnosed, treated and controlled?

Answer 8

Observation in stool.
Albendazole (prevents glucose absorption - starves+detaches).
Control: sanitation, edu, deworming

Question 9

What is schistosomiasis caused by? Where is it found? What is the intermediate host?

Answer 9

aka bilharzia
Schistosoma.
Fresh water lakes in Africa.
Snails.

Question 10

What does schistosomiasis cause in the body?

Answer 10

Swimmers itch, Katayama fever.

Question 11

Schistosome haematobium migrates to the urinary system - what does it cause there?

Answer 11

Haematuria. Bladder fibrosis. Squamous cell CA.

Question 12

Which types of Schistosoma cause portal hypertension and liver cirrhosis?

Answer 12

S. mansoni
S. intercallatum
S. japonicum
S. mekongi

Question 13

How is schistosomiasis diagnosed, treated and controlled?

Answer 13

Urinary + stool microscopy.
Praziquantel (increases worm ionic permeability + dies).
Kill snails, chemoprophylaxis, avoidance, sanitation.

Question 14

What is hydatid disease caused by? Where is it found? What is the usual host (we are accidental)?

Answer 14

Echinococcus.
All over the world
Sheep and dogs.

Question 15

Echoinococcus granulosus.
E multilocularis.
What type of hydatid disease does each cause?

Answer 15

Cystic.

Alveolar.

Question 16

What does hydatid disease do to the body?

Answer 16

Cysts -70% liver, 20% lungs.
May remain asymptomatic.
Mass effect.
Secondary bacterial infection.
Rupture - hypersensitivity.

Question 17

How is hydatid disease diagnosed and controlled?

Answer 17

Imaging, serology.

Deworming, hand hygiene, safe carcass disposal.

Question 18

What is malaria caused by? Where is it found? What type of host is the human?

Answer 18

Plasmodium: falciparum, vivax, ovale, malariae.
Equatorial areas.
Definitive.

Question 19

What are the clinical complications of malaria? (9).

Answer 19

Fever, rigors. 
Cerebral malaria. 
Renal failure. 
Hypoglycaemia. 
Pulmonary oedema.
Circulatory collapse. 
Anaemia.
DIC.

Question 20

How does malaria cause its clinical effects?

Answer 20

Ruptures red cells, blocks capillaries and causes inflammatory reaction.

Question 21

How is malaria diagnosed and controlled?

Answer 21

Microscopy, serology, PCR.

Insecticide in homes, larvicide and filling in of breeding pools. Bed nets. Chemoprophylaxis.

Question 22

What is cryptosporidiosis caused by? Where is it found? Which animals act as a reservoir?
How is it spread?

Answer 22

Cryptosporidium: parvum and hominis.
Worldwide.
Cattle, sheep, goats.
Faecal-oral route.

Question 23

What does cryptosporidiosis cause?

Answer 23

Watery diarrhoea with mucus.

Bloating, cramps, fever vomiting.

Question 24

How does cryptosopridiosis affect different people?

Answer 24

Usually self-limiting (2wks).

Severe in young, old, immunocompromised.

Question 25

How is cryptosopridiosis diagnosed and controlled?

Answer 25

Faeces acid fast staining.

Hygiene, isolation, filter/boil water. Pasteurisation.

Question 26

How is cryptosopridiosis treated in most patients?

Answer 26

Rehydration and nitazoxanide.

Question 27

What are the commonly used anti-protozoal treatments?

Answer 27

Metronidazole.
Pentamidine.
Nitazoxanide.
Pyrimethamine.

Question 28

What are the commonly used anti-helminthic treatments?

Answer 28

Albendazole.
Mebendazole.
Ivermectin.
Praziquantel.

Question 29

Name a flagellate:

Answer 29

Giardia.

Question 30

Name an ameboid:

Answer 30

Entamoeba.

Question 31

Name three sporozoa:

Answer 31

Plasmodium.
Toxoplasma.
Cryptosporidium.

Question 32

Name a trypanosome:

Answer 32

Leishmania.

Question 33

Name two cestodes:

Answer 33

Taenia.

Echinococcus.

Question 34

Name a trematode:

Answer 34

Schistosoma.

Question 35

Name a intestinal nematode:

Answer 35

Ascaris.

Question 36

Name 3 tissue nematodes:

Answer 36

Wucheria.
Onchocerca.
Loa loa.

Question 37

How is cryptosporidiosis treated in the immunocompromised (4).

Answer 37

Puromycin (kills parasite).
Nitazoxanide.
Octreotide (reduce cramps + freq).
HAART if HIV +ve.