introduction to parasites

Question 1

Describe the main groups of parasites and their life cycles.

Answer 1

Protozoa: Malaria, amoebic dysentry, leishmaniasis 
Helminths: 
-Nematodes: round worms
-Cestodes: tape worms
-Trematodes: Flat worms 
Arthropods

Question 2

Describe the common diseases caused by enteric and blood-borne parasites

Answer 2

protozoa:
MALARIA:
-vector-borne
-mosquitos deposit sporozoites under skin, travel to lungs and develop into Merozoites which enter the blood circulation and enter the RBCs, sexual forms taken up by mosquitos
LEISHMANIASIS:
-sand-fly bite
-cutaneous-skin ulcerations
-visceral- fever/weight loss
AMOEBIC DYSENTRY:
trophozoite: ingests Rbcs and spits out hot stool
cysts found in stool- 2 nuclei and 1 chromatid body
clinically: intestinal infection and liver abscesses
Helminths:
ASCARIS LUMBRICOIDES:
-nematode
-eggs hatch in intestine, move to lungs-adult worm, moves back to intestine
-may be asymptomatic-can block up SI or bile duct
TAENIA:
-cysts injected
-cestode
ECHINOCOCCUS:
-ingested as eggs- develop into cysts in the liver
-cestode
SCHISTOSOMATIASIS:
-trematode
-eggs-Miracidia- excreted in faeces- hatch in fresh water-taken up by snails (intermediate host) -cercaria leave snails and infiltrate blood- lungs to liver-develop into adult worms-enter mesenteric/bladder venues-hatch causing inflammation

Question 3

Define what is meant by the term ‘parasite’

Answer 3

An organism which lives within another organism and is eats off it

Question 4

Describe the diagnostic principles in parasitology

Answer 4

In stool samples:
-cysts
-ova 
-parasites
Cannot usually be cultured
Thick and thin blood samples for malaria
Serology

Question 5

Katayama fever

Answer 5

Febrile response 4-8 weeks after ova deposition in schistomatiasis