Malaria plasmodium species

Question 1

P falciparum - key point

Answer 1

Malignant - drives majority of severe malaria and disease burden

Tertain fever [3rd day/48hrs]

Ubiquitous and drives most cases and deaths in sub-Saharan Africa

‘Neat’ pathogen
Normal sized RBCs
Accole forms and multiple parasites
Banana shaped gametocytes

Question 2

P falciparum - epidemiology

Answer 2

All malarious zones
Foci of transmission in South America
Ubiquitous in sub-Saharan Africa - most cases and deaths

Question 3

P falciparum - clinical

Answer 3

7-14 days incubation
48hr intra-erythrocytic growth cycle:
-Tertian fever, irregular onset, due to asynchronous rBC cycle

No infection relapses

Drug resistance [ACT]
Diagnostics and Hrp2 deletions [false negative RDTs]

Vast majority of invasive disease, with var encoded PfEMP1 protein facilitating sequestration

Readily cultured in vitro

Question 4

P falciparum - lab and micro

Answer 4

Neat pathogen
No RBC enlargement

Can see multiple parasites per cell
Double chromatin dots [headphones]
Maurer’s clefts [uneven, fewer]
Schizont not filling cell, with 15-20 merozoites
Gametocytes ‘banana’/crescent

Question 5

P falciparum - spot associations

Answer 5

Severe malaria and cerebral malaria, PAM, and severe anaemia
Vessel sequestration and PfEMP1 [encoded by var genes]
ACT resistance - SE Asia but creeping into Africa
RDT false negatives
No relapses

Normal sized RBCs, accole forms, headphones, Maurer’s clefts, banana gametocytes

Question 6

P vivax - key points

Answer 6

Benign
Tertian fever [3rd day/48hours]
Widest distribution [but lower incidence]
Partial Duffy antigen dependence limits Africa’s burden

Can relapse, hyponozoites

‘Messy’ pathogen
Large RBC

Question 7

P vivax - epidemiology

Answer 7

All malarious zones
Exists in more temperate zones, widest distribution
Partially limited by the Duffy blood group

Question 8

P vivax - clinical

Answer 8

12-17 day incubation
Benign - low mortality
48hr intra-erythrocytic growth cycle - tertian fever

Relapses occur - relates to hyponozoites stages requiring radical cure

Duffy antigen aids RBC invasion

Control measures not as effective against P vivax [day biting species]

Cannot culture in vitro

Question 9

P vivax - lab and micro

Answer 9

Prefers larger RBCs and reticulocytes
Schuffner’s dots [even, coarser]
Schizont fills cell, 15-20 merozoites - pigment-rich
Gametocyte large, fills cell
Can see plasticity and unusual shaped RBCs

Question 10

P vivax - spot associations

Answer 10

Benign relapsing malaria
Hypnozoites
Partial Duffy antigen dependence
Night and day biting mosquitoes
All malarious zones, widest distribution, neglected

Larger RBCs, Schuffner’s dots, Schizont and gametocytes fill cell, plasticity phenomenom

Question 11

P ovale - key points

Answer 11

Limited to tropics
Tertian fever
Mixed infections
Can relapse
Neat pathogen, oval shape and fimbriation can be seen
Divided in to P ovale curtisi and P ovale walkeri

Question 12

P ovale - epidemiology

Answer 12

Limited to tropics
Widespread in Africa, present in Asia/Oceania
Absent in South America

Question 13

P ovale - clinical

Answer 13

12 -17 days incubation
Benign low mortality
48hrs intra-erythrocytic growth cycle - tertian fever

Relapses occur, hypnozoites stage

Low parasitaemia typical

Commonly mixed infections

RDTs fail with Curtisi
Nested PCR fail with Walkeri

Question 14

P ovale - lab and micro

Answer 14

Neat - RBC large, oval shape, fimbriation
James’ dots [even, corasen over development]
Schizont not filling cell with 8-10 merozoites
Gametocyte not filling cell
Low parasitaemia common

Question 15

P ovale - spot association

Answer 15

Benign malaria
Absent in South America
Mixed infections

James’ dots, low parasitaemia

Question 16

P knowlesi - key points

Answer 16

Zoonotic, macaques primary host
Can cause severe disease
SE Asia with foci in Malaysia
Quotidian fever [daily]

Question 17

P knowlesi - epidemiology

Answer 17

Zoonotic malaria
SE asia
Hot - long and pig-tailed macaques, with human infection rare
Limited by macaques [host], mosquito species [leucosphyrus], and Duffy blood group

Question 18

P knowlesi - clinical

Answer 18

8-12 day incubation
High fatality rate [10% progress to severe]
Fast growth cycle in blood -24-27 hours
Human invasion uses the DARC receptor [Duffy antigen positive]
Can be cultured in vitro

Question 19

P malariae - key points

Answer 19

Benign malaria
Quartan fever [4th day/72hours]
Can form chronic malaria presenting years to decades later [renal, spleen]
Mixed infections
Commonly misidentified - can mimic falciparum and vivax
Daisy head schizont
Older smaller RBCs

Question 20

P malariae - epidemiology

Answer 20

All malarious zones
Rare

Question 21

P malariae - clinical

Answer 21

Incubation 18-40 days
Benign
72 hour growth
Persistence - chronic malaria [not a latent hypnozoite stage]
Renal and splenic pathologies
Low parasitaemia

Question 22

P malariae - lab and micro

Answer 22

Old smaller RBCs
No dots [Ziemann’s dot can be faintly seen]
Bird’s eye ring
Band forms
Schizont fills cells, 8-10 merozoites and ‘daisy head’
Gametocyte fills cell, no enlargement - dense scattered pigment