Description

• Acute or chronic infection transmitted to humans by Anopheles spp. mosquitoes
• Most morbidity and mortality is caused by P. falciparum; it is responsible for 216 million cases annually, including 655,000 deaths, the majority of which occur in children <5 years in sub-Saharan Africa.
• Nonimmune individuals are most susceptible to rapid progression to severe disease.
• System(s) affected: Lymphatic; Immunologic; Vascular; Hematologic; Renal; Cerebral

Epidemiology

• Most US cases (>99%) are imported. Very rare cases reported from local transmission after introduction, transfusion transmission, and congenital transmission.
• ~1,500 cases and 5 deaths per year in the US.
• Cases imported to the US: 58% P. falciparum; 19% P. vivax; 2% P. malariae; 2% P. ovale; 1% mixed; 18% unknown

• Predominant age: All ages
• Predominant gender: Male = Female

Risk Factors

• Traveling and/or migration from an area where malaria is endemic (most from sub-Saharan Africa)
• Rarely, blood transfusion, mother-to-fetus transmission, and autochthonous transmission

Genetics
Unknown genetic predilection, but inherited conditions may affect disease severity and susceptibility (glucose-6-phosphate deficiency, sickle cell disease or trait, and hereditary elliptocytosis)

General Prevention

• Mosquito avoidance measures: Insect repellent, clothing that covers most of the body, mosquito nets treated with permethrin, air conditioning, and avoiding outdoor activity dusk to dawn (1)[A]
• Malarial chemoprophylaxis when in endemic area:
  • Mefloquine: Begin at least 2 weeks before arrival and continue for 4 weeks after leaving area. Adults, 250 mg (1 tablet) weekly; children ≤9 kg, 5 mg/kg; children >9–19 kg, 1/4 tablet weekly; children >19–30 kg, 1/2 tablet weekly; children >30–45 kg, 3/4 tablet weekly; children >45 kg as adult:
    • Caution: Mefloquine-resistant areas
  • Atovaquone/Proguanil: Begin 1–2 days before arrival and continue for 1 week after leaving area. Adults, 1 adult tablet daily; children 5–8 kg, 1/2 pediatric tablet daily; children >8–10 kg, 3/4 pediatric tablet daily; children >10–20 kg, 1 pediatric tablet daily; children >20–30 kg, 2 pediatric tablets daily; children >30–40 kg, 3 pediatric tablets daily; children >40 kg, 1 adult tablet daily
  • Doxycycline: Begin 1–2 days before arrival and continue for 4 weeks after leaving area. Adults, 100 mg daily; children, 2 mg/kg up to 100 mg daily (not for children <8 years old)
  • Chloroquine: Begin 1–2 weeks before arrival and continue for 4 weeks after leaving area. Adults, 300 mg base (500 mg salt) weekly; children, 5 mg base/kg weekly up to 300 mg:
    • Caution: Chloroquine-resistant areas
  • Primaquine: Begin 1–2 days before arrival and continue for 1 week after leaving area; adults 30 mg/d; children, 0.5 mg/kg/d up to adult dose:
    • For use only in areas predominantly endemic for P. vivax
    • Caution: Glucose-6-phosphate dehydrogenase deficiency must be excluded prior to first use.

Pathophysiology

• Malarial parasites digest red cell proteins and make the RBC membrane less deformable, causing hemolysis, increased splenic clearance, and anemia.
• Red cell lysis stimulates release of cytokines and TNF-α.
• P. falciparum induces human RBCs to secrete a protein that makes RBCs stick to the intravascular surface of small blood vessels, causing obstruction and end-organ ischemia.

Etiology

P. falciparum, P. malariae, P. vivax, P. ovale, and P. knowlesi in parts of Southeast Asia

Commonly Associated Conditions

Bacterial co-infections are not common but can sometimes occur.