1) due to infection with protozoa Plasmodium (P. falciparum, P. vivax, P. ovale, P. malariae) 2) vector is bite of Anopheles mosquito 3) infection with P. falciparum causes most severe disease 4) P. ovale and P. vivax can stay dormant in body for years and cause disease relapses even after apparent cure.
Signs and Symptoms
1) malaise 2) fatigue 3) headache 4) chest and abdominal pain 5) muscle aches 6) fever 7) nausea and vomiting 8) orthostatic hypotension 9) jaundice 10) palpable spleen 11) pulmonary edema 12) renal failure 13) mental status changes (including coma) 14) seizures (P. falciparum)
Characteristic Test Findings
Laboratory – 1) increased bilirubin 2) mild anemia and thrombocytopenia 3) hypoglycemia 4) lactic acidosis 5) diagnosis is by visualizing asexual parasite in peripheral blood smear under Romanowsky’s stain
1) intraerythrocyte organisms 2) rosetting of RBCs 3) “knobs” on RBC membrane owing to cytoadherence
1) female mosquito regurgitates during blood meal 2) organism travels to liver with asexual reproduction inside hepatocyte 3) hepatocyte ruptures and organisms reenter bloodstream and enter RBCs (clinical disease now evident) 4) organism consumes almost all hemoglobin, reproduces sexually, and ruptures the RBC (within 72 h) and more RBCs are infected, etc.
heterozygosity for sickle cell, glucose-6-phosphate deficiency, and thalassemia confer some resistance
1) one billion people infected worldwide 2) 2-3 million deaths yearly 3) in USA occurs in travelers to endemic regions and in immigrants
1) chemoprophylaxis for travel to endemic arease – mefloquine or atovaquone are first choices (1 week before until 4 weeks after exposure) 2) for mild cases and nonfalciparum etiology – chloroquine 3) for more severe cases and P. falciparum cases – quinidine or mefloquine 4) eradication of mosquitoes and larvae
Tips for USMLE
1) classic malarial paroxysms are episodic fever spikes, chills, and rigors 2) there is no rash 3) there is no photophobia or neck stiffness