discussed include: severe pneumonia or adult respiratory distress syndrome (ARDS), coma
and meningoencephalitis, acute abdomen, dysentery and severe gastrointestinal fluid losses,
fulminant hepatitis, and tropical fever.
MALARIA
Malaria is caused by four different species of the plasmodium parasite(Plasmodium falciparum,
P. ovale, P. vivax, and P. malariae), withP. falciparumas the predominant cause of mortality (8).
Data from 1997–2002 collected through the GeoSentinel global sentinel surveillance identified
malaria in 3.7% of all returning travelers seeking medical care (9). The majority of the cases
were caused byP. falciparum(60%) followed byP. vivax(24%) (9). Patients with falciparum
malaria were more likely to have traveled to sub-Saharan Africa (89%), with the majority (80%)
presenting within four weeks of their return. Among patients withP. falciparummalaria, 60%
were hospitalized with 2.4% diagnosed with cerebral malaria and 2.3% with severe
complicated noncerebral malaria. There was a 9% case fatality rate among those with severe
malaria. The case fatality rate for US travelers with falciparum malaria from 1966–1987 was
3.8% (10), and for 1985–2001 was 1.3% (11). Several important features are noted among those
patients who died from their infection. These include: insufficient or inappropriate malaria
chemoprophylaxis (90%) and delay in diagnosis and/or effective therapy (40%). Both features
highlight the preventable aspect of these deaths (10). In a more recent series, cerebral malaria
was the most common complication (48%) followed by renal failure (44%), acute respiratory
distress (32%), anemia (21%), disseminated intravascular coagulation (DIC) (11%), and splenic
rupture (5%) (11). Deaths were considered preventable in 85% of cases and were commonly
attributed to patient-related decisions/actions and/or contributing medical errors (11). In
2006, 1564 cases of malaria diagnosed within the United States were reported to the Centers for
Disease Control (CDC) (12). Diagnoses included:P. falciparum(39.2%), P. vivax(17.6%),
P. malariae(2.9%),P. ovale(3.0%), two or more species (0.6%), and unreported or undetermined
(36.6%). Six of the infections were fatal and were caused byP. falciparum(5) orP. malariae(1).
The current recommendations for malaria prophylaxis take into consideration regional
antimalarial drug resistance (13). There is no universally effective regimen, as evidenced by
P. falciparum mefloquine resistance on the Thai-Burmese and Thai-Cambodian borders,
falciparum malaria in US troops in Somalia despite their prophylaxis with doxycycline or
mefloquine, and reports of chloroquine-resistantP. vivaxin Indonesia (14–18). And so, as a
result of our population’s increasing travel to malaria-endemic areas as well as oftentimes
inadequate adherence to prescribed chemoprophylaxis, it is increasingly likely that today’s
critical care physician will encounter patients with malaria. How then, does one make this
critical diagnosis in a timely manner?
Unfortunately, there are no historical or physical findings pathognomonic for malaria.
Therefore, malaria cannot be ruled out by history or physical examination alone (11,19,20).
Falciparum malaria often presents without the classic features of cyclical fever, chills, and
diaphoresis (21). More common, is a nondescript febrile illness without apparent pattern.
Other presenting features may include severe anemia, thrombocytopenia, central nervous
system (CNS) dysfunction, such as coma or seizures, and pulmonary edema (13,22).
When the diagnosis of malaria is suspected, examination of Giemsa or Wright-stained
peripheral blood thick and thin smears should be performed. Thick smears are more sensitive
(larger volume of blood), but are also more difficult to interpret. Thin smears aid in species
identification, and higher percentage parasitemias may be evident even to the novice.
Nonetheless, peripheral smears are best reviewed by experienced microscopists. Because
nonimmune persons may be symptomatic even at very low parasitemia levels, CDC guidelines
recommend at least three peripheral blood smears (with smears repeated every 12 to 24 hours
for a duration of 48 to 72 hours) (23). In 2007, the US Food and Drug Administration (FDA)
approved a rapid assay for the diagnosis of malaria (Binax Now^1 Malaria Test, an ELISA-
based assay with both global plasmodium andP. falciparum–specific antibodies adsorbed to a
test card). Venous blood or blood from a peripheral stick is applied to the test card, and within
15 minutes a negative or positive result is apparent. However, serial thick and thin smears are
still recommended (although a negative rapid assay, even if falsely negative, likely excludes
significant parasitemia). A positive assay should also be followed by examination of the
324 Wood-Morris et al.