Malaria

Question 1

describe malaria life cycle

Answer 1

1. mosquito bites malaria infected human
2. ingested gametocytes reproduces sexually = ookinete, which mature to oocyst
3. mosquito bites- oocyst ruptures and SPOROZOITES released
4. sporozoites migrate to liver where they mature to schizonts
5. merozoites released from liver, infect RBCs, produce more merozoites,

Question 2

What are the parasite spp?

Answer 2

• Plasmodium falciparum
• Plasmodium vivax
• Plasmodium malariae
• Plasmodium ovale

Question 3

what is the malarial vector?

Answer 3

• Anopheles farauti

Question 4

Describe lifecycle of plasmodium

Answer 4

• Female anopheline mosquito becomes infected when it feeds on human blood containing gametocytes, the sexual forms of the malarial parasite
• Development in the mosquito takes from 7-10 days, and results in sporozoites accumulating in the salivary glands which are inoculated into the human blood stream
• Sporozoites disappear from human blood within half an hour & enter the liver. After some days, merozoites leave the liver & invade RBCs, where further asezual cycles of multiplication take place, producing schizonts.
• Rupture of the schizont releases more menozoites into the blood & causes fever (periodicity depends on the species of parasite)
• P vivax & P. ovale may persist in liver cells as dormant forms, hypozoites, capable of developing into menozoites months or years later. Thus the first attack of clinical malaria may occur long after the patient has left the endemic area, and the disease may relapse after treatment if drugs that kill only the erythrocytic stage of the parasite are given
• P falciparum & P malariae have no persistent exo-erythrocytic phase, but recurrence of fever may result from multiplication of parasites in red cells which have not been eliminated by treatment & immune processes

Question 5

manifestations- when do p. vivax and p ovale relapse

Answer 5

can relapse after months and years due to hypnozoite forms remaining dormant in the liver.

Question 6

describe the pathology of malaria

Answer 6

• Red cells infected with malaria are prone to haemolysis. This is most severe with P. falciparum, which invades red cells of all ages but especially young cells; P vivax & P. ovale invade reticulocytes & P. malariae normoblasts, so that infections remain lighter. Anemia may be profound & is worstened by dyserythropoiesis (defective development of RBC), splenomegaly & depletion of folate stores.
• In P. falciparum malaria, red cells containing trophozoites adhere to vascular endothelium in the brain, kidney, liver, lungs & gut. As a result, these vessels become congested, resulting in widespread organ damage which is exacerbated by rupture of schizonts, liberating toxic & antigenic substances

Question 7

what are the clinical features of malaria?

Answer 7

Clinical features of malaria are non-specific & the diagnosis must be suspected in anyone returning from an endemic area who has features of infection.

• Headache
• Weakness
• Myalgia
• Arthralgia
• Pallor
• Hepatosplenomegaly
• Seizures
• Anorexia
• Altered LOC
• Nausea & vomiting
• Diarrhoea
• Abdominal pain

Question 8

what are the laboratory findings in malaria?

Answer 8

• Hypoglycemia 5%
• Lactate >5mmol/L
• Serum creatinine >265 mmol/

Question 9

diagnostic tests

Answer 9

Light microscopy- geimsa stained thicka nd thin films- 3 times over 3 days
+ HRP-2antigen detection- fast feild stable kit

Question 10

Tests you must order

Answer 10

urinalysiss
FBc
serum LFTs
blood glucose

Question 11

Treatment of malaria

Answer 11

Quinolones (chloroquine resistance in p.falciparum and p.vivax)
Antifolates
artemisinin derivatives
antimicrobials- tetracyclines, clindamycin