Malaria Flashcards
What is Malaria?
It is an infectious disease caused by members of the plasmodium family. Which are protozoa (single cells) parasites.
What is the commonest and dangerous member of the plasmodium family?
P. falciparum
What is the pathophysiology of Malaria?
- Infected mosquito bites and sporozoites (malaria spores) are transferred to the blood of the human.
- Sporozoites go to the liver where they can lie dormant as hipnozoites (only done in p. vivax and p. ovale variations) they asexually reproduce and mature into merozoites
- Metozoites move to the blood and invade RBC’s where they reproduce causing the RBC to rupture and more merozoites into the blood.
What are the risk factors for Malaria?
Travel to countries in which malaria is prevalent
What are the symptoms of malaria?
Non specific symptoms
- Fever
- Headache
- Malaise
- Myalgia
- Diarrhoea
- Cough
(Fever patterns are described but only occur if rupture of infected of RBCs is synchronized
Alternate days for P.falciparum, P.vivax, P.ovale
Every 3rd day for P.malariae
Most patients have no specific fever pattern)
- Anaemia (pallor, hepatospenomegaly, jaundice)
- Cerebral malaria is marked by diminished consciousness, confusion and convulsions progressing to coma and death - due to the reduced brain perfusion caused by schizonts adhering to the endothelial cells of capillaries = hypoxia to brain (P. Falciparum)
- If diagnosis is delayed, patient may present with jaundice, confusion and seizures
How long after exposure is p. falciparum likely to produce symptoms?
> 3 months
How long after exposure if p. vivax likely to produce symptoms?
Up to a year
What type of mosquito spreads malaria?
The female anopheles mosquitoes
What time of day do the mosquitoes usually spread the infection?
During the night
Why is it important to test for malaria over 3 days?
Because the merozoites reproduce every 48 hours (depending on the plasmodium species) and so it won’t be found in the blood unless its reproducing and the RBC is then rupturing.
When should you suspect malaria?
When someone has traveled to an area where malaria is present
What is the usual incubation period of the disease?
1 - 4 weeks after exposure but this varies depending on the species e.g p. vivax or ovale can lie dormant for months - years
How do you diagnose malaria?
Malaria specific blood film - to look at if there are any parasites, how many and what type.
How many blood samples do you need to request to exclude a diagnosis of malaria?
3 consecutive samples over 3 consecutive days as the sample may be negative on the days when the parasite is not released.
What type of blood smear would you do when diagnosing malaria?
- Thick film: sensitive but low resolution (difficult to intepret and speciate the parasite but have higher yield) but tells you if malaria is present
- Thin film: can identify morphological features and quantification of parasitaemia. Tells you type and parasite count (above 2% = severe).
