Malaria

Question 1

Malaria aetiology

Answer 1

Infection with protozoan Plasmodium:
Plasmodium falciparum (most common)
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae

Transmitted by the bite of a female Anopheles mosquito. The protozoa infect RBCs and grow intracellularly

Question 2

What are the risk factors for malaria

Answer 2

Travel to endemic area (Africa, South of the Sahara, Papua New Guinea (Oceania))
Lack of appropriate chemoprophylaxis
Absence of insecticide-treated bed net in an endemic area
Settled migrants returning from travel to an endemic area

Severe infection:
Low host immunity
Pregnancy
Age <5 years
Immunocompromise
Older age

Question 3

Who has innate immunity to malaria

Answer 3

Sickle cell trait
GP6D deficiency
Pyruvate kinase deficiency
Thalassaemia

Question 4

What are the symptoms of malaria

Answer 4

Fever (peak every 48h for falciparum)
Flu-like symptoms
Severe sweating
Shivering/rigors
Headache
Weakness
Myalgia
Arthralgia
Anorexia, diarrhoea, N&V, abdominal pain

Question 5

What features of malaria are characteristic of falciparum

Answer 5

Cerebral involvement: headache, disorientation, seizure, coma
Severe anaemia
Renal failure - anuria/oliguria
Hypoglycaemia
Pulmonary oedema
DIC/bleeding (gums, nose, venepuncture sites, haematemesis, melaena)
Hypovolaemia
Acidosis
Hyper parasitaemia

Question 6

What are the differentials for malaria

Answer 6

Dengue fever
Zika virus
Chikungunya virus
Yellow fever
Pneumonia
Influenza

Question 7

What are the signs of malaria on exam

Answer 7

Obs: Pyrexia, Hypotension (falciparum), Tachypnoea (malaria with acidosis)

General:
- Anaemia: SOB, pallor
- Rigors
- Jaundice (falciparum)
- Altered level of consciousness, confusion (falciparum)

Abdominal
- Hepatosplenomegaly

Question 8

What investigations should be done for malaria

Answer 8

Bedside: urinalysis (protein+, haem +), urinary bilirubin (raised)

Bloods:
- Thick/thin blood film x3 (Giemsa-stained): Intra-erythrocytic ring-formed parasites, Schizonts (falciparum), >2% parasite count = severe
- FBC: thrombocytopenia, anaemia, variable WCC
- U&Es: Usually normal or mildly impaired, renal failure if severe
- HIV serology
- ICT test: Detects histidine protein 2 found only in P. falciparum
- QBC: Orange stain on parasite nucleus
- Malaria antigen detection test: OptiMAL -IT (parasite LDH), Paracheck-Pf (plasmodial HRP-II)

Question 9

What is the management for malaria (non-falciparum, uncomplicated falciparum, mild falciparum, severe falciparum, parasite count >10%), hypnozoites

Answer 9

1. Immediate admission + notify Public Health England
2. Treatment depends on the strain, severity, tolerability, resistance
   Non-falciparum: Chloroquine
   Uncomplicated falciparum: Chloroquine phosphate (oral)
   Mild falciparum: ACT (Artemisinin Combination therapy)
   Severe falciparum: IM/IV Artesunate (parenteral)
   Parasite count >10%: Exchange transfusion

+ Primaquine (not G6PDD) for eradication of hypnozoites (dormant parasites in liver in vivax and ovale)

Question 10

What can be used for prevention/prophylaxis for malaria

Answer 10

Awareness of risk - geographical (high altitudes - different transmission), individualise e.g. pregnancy, season, accomodation
Bite prevention e.g. bite repellent, insecticide-treated nets (ITNs)
Chemoprophylaxis e.g. malarone, mefloquine, doxycycline (varies by region), Quinine (reduces but does not eliminate risk of infection)
Diagnose promptly and treat without delay

Question 11

What are the complications of malaria

Answer 11

cerebral malaria: seizures, coma
acute renal failure: blackwater fever, secondary to intravascular haemolysis, mechanism unknown
acute respiratory distress syndrome (ARDS)
hypoglycaemia
disseminated intravascular coagulation (DIC)
Metabolic acidosis
Severe anaemia (Red cell lysis, autoimmune haemolysis)
Septicaemia

Question 12

What is the prognosis for malaria

Answer 12

Children <5 are most vulnerable, with most deaths in the African region (95%)
Majority of deaths are from Plasmodium falciparum infection
Approximately 90% of travellers who acquire malaria will not become symptomatic until they return home
Malaria can progress from asymptomatic to death in 36-48 hours
Up to 80% of patients with cerebral malaria will recover with treatment, but mortality is still 15% to 20%

Question 13

What characterises severe malaria

Answer 13

Parasitaemia:
Children >2%
Adult >10%
Presence of one schizoint (cell full of parasites)