Malaria

Question 1

Presentation

Answer 1

Malaria
Cyclic fever at 48-72 hour intervals
Shaking chills
Soaking sweats
Anemia (hemolytic)
Splenomegaly; Typically after >4 days of symptoms
Agitation
Hyperventilation
Bleeding
History of exposure in malaria-endemic area
Patients are often asymptomatic between attacks

Question 2

Symptoms suggesting an alternate diagnosis include

Answer 2

Rash
Lymphadenopathy
Neck stiffness
Photophobia

Question 3

Complications

Answer 3

Cerebral malaria
Severe hemolytic anemia
Renal failure
ATN
Noncardiogenic pulmonary edema

Question 4

Pathogenesis

Answer 4

Plasmodium has 2 hosts and multiple distinct forms during its complex life cycle
Infection results in lysis and agglutination of RBCs
Rupture of RBCs correlates with fever spikes
Lysis occurs in a synchronized fashion (all RBCs lyse at the same time

Question 5

Pathogenesis
P. falciparum

Answer 5

Most common and most deadly species
Occasionally causes death within 24 hours of symptom onset
Malignant tertian malaria
Irregular fever spikes (36-48 hours)
Cerebral malaria
Lysed RBCs occlude capillaries in brain
No hypnozoite stage

Question 6

Pathogenesis
P. vivax and P. ovale

Answer 6

Benign tertian malaria
48 hour fever spikes
“Tertian” because you count day 1 and day 3, although fevers actually 48 hours apart
Hypnozoite stage

Question 7

Pathogenesis
P. malariae

Answer 7

72 hour fever spikes
Recrudescence
Symptoms recur from low levels of organisms in RBCs
No hypnozoite stage

Question 8

Pathogenesis Transmission

Answer 8

Anopheles mosquito

Question 9

Evaluation

Answer 9

Blood smear
Giemsa- or Wright-stained thick and thin blood films
Trophozoites and schizonts visualized within RBCs
Diagnosis of strain is essential to guide treatment!

Rapid antigenic tests; too expensive for developing world

Normocytic, normochromic anemia on CBC

Question 10

Treatment

Answer 10

Drugs
Chloroquine
Kills erythrocytic forms of all susceptible Plasmodia species
P. vivax, ovale, and malariae are sensitive
P. falciparum can be resistant
Retinopathy associated with long-term use

Primaquine; use for P. vivax/ovale to kill latent hypnozoites

For chloroquine-resistant P. falciparum use
Mefloquine
Quinine
Artemether
Atavaquone-proguanil (Malarone)
Pyrimethamine/sulfadoxine
Pyrimethamine is a dihydrofolate reductase inhibitor also used in toxo

for severe infections, IV quinidine

Question 11

Prevention

Answer 11

Kill mosquitoes
Bed nets, long-sleeved clothes, DEET or other repellent
Chemical prophylaxis for travelers

Question 12

Immunity

Answer 12

HbS heterozygote (sickle cell trait); protection against P. falciparum
Absence of Duffy (Fy) antigen on RBC; protect against P. vivax; most common in blacks