Malariae

Question 1

List & describe the 3 forms of Plasmodium in humans

Answer 1

• Shizont: Contain merozoites - ready to burst & infect other cells
• Trophozoite: Maturing parasite (ring form in most sp.)
• Gametocyte: sexual precursor cells that are transmitted into mosquito

Question 2

What methods are used to detect Plasmodium?

Answer 2

• 3x Thick film (screening): NOT fixed & stained in 10% Geimsa stain phosphate buffer (pH 7.2)
• 2x Thin film (confirmation): FIXED & in May-Grunwar & Geimsa (preferably pH 7.2)

Question 3

Why is it recommended to use alkalines stains?

Answer 3

High pH = see parasites better vs acidic stains (ph <6.8)

Question 4

Advantages and disadvantages of doing a thick films

Answer 4

Adv: concentrate = likely to detect Plasmodium organism
Dis: Organisms distorted = difficult to determine sp
=> Hence screening

Question 5

Advantages and disadvantages of doing a thin films

Answer 5

Adv: Better assessment = can speciate
Dis: Difficult to detect low density infections

Question 6

What are the 4 Plasmodium sp. and which are deadly & common

Answer 6

1. P. vivax: common
2. P. falciparum: common & deadly
3. P. ovale
4. P. malariae

Question 7

What are Shuffner’s dots

Answer 7

Morphologic alterations. Visible under light microscope when stained w/ Romanowsky stain = brick-red dots

Question 8

What’s the reason Plasmodium falciparum
causes parasitaemia?

Answer 8

• Invades reticulocytes & mature RBC = more paracitemia

Question 9

What reasons makes Plasmodium knowlesi to be pathogenic?

Answer 9

• 24h lifecycle (short)
• infects youn & mature RBC

Question 10

list 6 Risk factors for identification using morphology

Answer 10

• Poorly prepared/stained
• Deteriorated organisms
• Low # parasites
• Mixed infection
• Novel organism
• (Inexperience)

Question 11

List 3 additional testing methods & use/adv

Answer 11

• Rapid diagnostic test: screening before microscopy
• PCR (*standard techn): can detect multiple infections, sp. w/ similar morphology, low [parasites] in blood
• automated analysers:

Question 12

Plasmodium knowlesi
a) definitive host
b) Present in what area
c) often misdiagnosed w/ _ so need to confirm using [method]

Answer 12

a) D.host: macaque monkey
b) in: SE asia
c) P.falciparum & P.malariae. Confirmed by PCR & DNA sequ.

Question 13

Plasmodium cynomolgi
a) normal host
b) often misdiagnosed w/ _ so need to confirm using [method]

Answer 13

a) Macaca fascicularis
b) P.vivax. Confirmed by PCR

Question 14

Plasmodium brasilianum & P. simium is often misdiagnosed w/ _

Answer 14

P. vivax