Internal Medicine

0521779407-14 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:16

Malaria 943

■Severe falciparum malaria: cerebral malaria (altered mental status,

seizures, coma), renal failure, pulmonary edema, severe anemia,

hypoglycemia, metabolic acidosis

P. knowlesi can also cause severe acute illness with high-grade para-

sitemia.

tests

Basic Tests: Blood

■WBC typically normal or decreased, thrombocytopenia common,

anemia with progressive disease, hemolysis=elevated bilirubin

and LDH, decreased haptoglobin, increased reticulocyte count

■In severe disease: hypoglycemia, elevated BUN and creatinine,

metabolic acidosis, elevated liver enzymes, DIC picture (uncom-

mon)

Basic Tests: Other

■Urinalysis: hemoglobinuria, proteinuria with severe disease

■CSF in cerebral malaria: usually normal, protein may be slightly ele-

vated

Specific Diagnostic Tests

■Thick and thin blood smears: diagnostic tests of choice; Giemsa

staining (pH 7.2) preferred; increased sensitivity with thick smear;

thin smear used for determining parasite species (multiply

infected RBCs, parasitemia >1%, banana-shaped gametocytes=P.

falciparum; RBC enlargement, circulating schizonts=P. vivax or

ovale)

■To determine level of parasitemia, examine slides on high power

under oil immersion; for thick smear, count the number of asexual

parasites per 200 WBCs and calculate the number of parasites/mcl

assuming a WBC of 8,000/mcl; for thin smear, count the number

of parasitized RBCs among 1,000 RBCs and calculate the% infected

RBCs

■Other: acridine orange staining of centrifuged parasites in Quantita-

tive Buffy Coat (QBC), immunochromatographic assay for histidine-

rich protein 2 (HRP-2) of P. falciparum (ParaSight F assay, Becton

Dickinson); PCR amplification of parasite DNA or mRNA

differential diagnosis

■Extensive; includes typhoid fever, meningitis, encephalitis, brain

abscess, pneumonia, gastroenteritis, bacterial sepsis, hepatitis,

dengue fever, yellow fever, leptospirosis, viral hemorrhagic fever