Haematology (Blood borne parasites) Flashcards
(36 cards)
What is parasitism?
A form of symbiosis where the parasite benefits form the relationship at the expense of the host
What are the main groups of endoparasites that affect humans?
Protozoa and helminth worms
What is malaria? What is it transmitted by?
- A potentially fatal infectious disease
- May be transmitted by female mosquitoes of the genus Anopheles
Other than through mosquitoes, how may malaria be passed on?
Transfusion
Transplanation of infected bone marrow
Placental transmission (congenital malaria)
Where is malaria common?
Tropical and sub-tropical areas
How many deaths are there each year from malaria?
1-3 million
mainly of yound children in sub-saharan africa
Infection with what parasite causes 80% of cases?
P. falciparum
What is the receptor for P. falciparum?
Glycophorin A/B/C
Describe the process of red cell invasion by malarial merozoite
1) Merozoite in the blood attach to receptors on RBC surface
2) Merozoite re-orientates so that the apical pole is directed towards the RBC surface
3) Tight junction forms between merozoite and RBC surface accompanied by initial deformation of RBC membrane
4) Entry of merozoite coinciding with formation of parasitophorous vacuole
5) Closure of RBC and parasitophorous vacuole membranes
6) Junction between RBC membrane and parasitophorous vacuole severed releasing merozoite into cell where it transforms into young trophozoite
Describe what happens after the merozoite becomes the trophozoite?
- ‘Feeding stage’
- Ingests 80% of haemoglobin and other contents of the RBC
Name some other forms of malaria forming parasites
P. falciparum
P. vivax
P. ovale
P. malariae
What is the incubation period between infection and onset of clinical symptoms for P. flaciparum?
7-14 days
What are the common symptoms in all species?
- Fever
- Sweating
- Headache
- Weakness
- Dizziness
- Nausea
- Anaemia
What are some symptoms unique to P. falciparum?
- Neurological imbalances
- Muscle spasms
- Pulmonary oedema
- Jaundice/liver failure
- Hypoglycemia
- Diarrhoea
- Circulatory collapse
What is a potentially life threatening consequence of malaria?
Haemolytic anaemia
How are RBCs destroyed during malaria?
1) The reiculoendothelial system removes parasitised RBCs by extravascular phogocytosis
2) Red cell parasites removed in spleen by ‘pitting’
- Pitting is removal of parasite and part of the red cell membrane
- Reduces lifespan of RBCs
What happens to the spleen as the result of this increased activity?
Splenomegaly
Name some other things that happen to RBCs due to malaria
1) Release of pro-inflammatory cytokines by immune system (e.g TNF-alpha) can result in dyserythropoiesis (abnormal RBC development)
2) Erythropoiesis suppressed by formation of haemozoin (heme that has converted by parasite)
What is blackwater fever?
A complication of malaria infection in which red blood cells burst in the bloodstream (hemolysis), releasing hemoglobin directly into the blood vessels and into the urine, frequently leading to kidney failure.
What can occur to WBCs as a result of malaria?
- Neutrophilia
- Eosinophilia or eosinopenia
- Atypical lymphocyte morphology
Can be see in the recovery phase
What commonly occurs to platelets during malaria?
- Increased activation
- Increased clearance by spleen
- Reduced lifespan
Results in thrombocytopenia
By what 3 mechanisms may blood coagulation occur in malaria?
1) Cytokine storm in response to infection activating clotting mechanisms
2) Alterations to the membranes of infected cells reveal coagulation promoting phospholipids
3) Adherence of parasitised cells to deep tissue capilary endothelium
Reduced synthesis and increased activation of coagulation factors have what effect on prothrombin time and activated partial thromboplastin time?
Mild elevations in PTT and APTT
What is the most common lab detection method for malaria?
Light microscopy of Romanowski-stained blood films
