Malaria

Question 1

What is the pathogenesis of malaria?

Answer 1

Generally;

• Female Anopheles mosquito bites.
• Sporozoites pass through skin ⇒ enter blood
• Enter hepatocytes ⇒ multiply as schizonts and release as merozoites
  
  • ​Form latent hypnozoites (stay there for years ⇒ relapse)
• Days ⇒ rupter hepatocytes ⇒ enter blood
• Enter RBC ⇒ form **trophozoites ⇒ schizonts** ⇒ haemolysis (and release of loads of merozoites from schizonts) & cytokine release (fever)

Question 2

What are the most common species that cause malaria?

State their incubation period & fever periodicities

Answer 2

• **P. falciparum - 48hr **(deadliest)
  
  • Incubation 7-10d
  • Fulminating disease (nasty)
  • Africa
• P. vivax - 48hr
  
  • Incubation 10-17d
  • ‘Benign tertian malaria’
  • May form hyponozoites
  • SE asia
• P. ovale - 48hr
  
  • Similar to P. vivax but quicker recovery
  • May form hyponozoites
  • SE asia
• P. malariae - 72hr
  
  • Incubation 18-40dMay ‘lie low’ in blood to recrudesce 1-52yr
  • May cause GN
• P. knowlesi (monkeys..)

Question 3

What is pathophys of fever periodicity?

Answer 3

Reflects synchronus rupture of mature schizonts releasing merozoites (haemolysis & cytokine release)

DOES NOT rule out any type of malaria

Question 4

Define malaria paroxysms

Answer 4

1. Shivering for <1h (“i feel so cold”)
2. Hot stage for 2-6h (T~41C)
   
   • Flushed
   • Dry skin
   • +/- headache, nausea, vomiting
3. Sweating for 2-4hr as temp falls

Question 5

What are protective factors to malaria?

Answer 5

• Sickle cell trait
• Hereditary elliptocytosis (melanesian ovalocytosis)
• G6PD deficiency
• Some HLA B53 alleles enable T cells to kill parasite-infected hepatocytes in non-Europeans

Question 6

How would Falciparum malaria classically present?

Outline signs, complications

Answer 6

90% within 1 month with flu-like prodrome;

• Headache, malaise, myalgia, anorexia
• → Fever peroxysms +/- faints

Signs include;

• Anaemia (haemolysis)
• Thrombocytopenia
• Jaundice
• Hepatosplenomegaly

Grim signs (CHAAC);

• Cerebral malaria; coma/ convulsions
• Hypoglycaemia
• ATN renal failure
• Acidosis (lactic)
• Chronic illness

Question 7

How would you diagnose malaria?

Answer 7

• Serial thin & thick blood film
  
  • 3 thick films over 72hrs to exclude malaria with confidence
• FBC
  
  • ​Thrombocytopenia [? spleen?]
  • Anaemia
• **Blood culture **to rule out sepsis
• Urinalysis
  
  • Haemoglobinuria
  • Proteinuria
  • Casts
• U&E; renal failure
• ABG
  
  • Metabolic (lactic) acidosis
• Glucose; hypoglycaemia

Memorise;

• Blood film, count & culture
• Urinalysis&E (U&E)
• ABGlucose