Ethnicity, parasitemia may predict severe falciparum malaria outcomes

Among adults from malaria-nonendemic countries, whites and Asians were more likely than blacks to develop severe falciparum malaria.

Patients with a history of clinical malaria were also at a significantly reduced risk for severe falciparum malaria, according to findings from a worldwide study.

Researchers evaluated 482 cases of malaria due to Plasmodium falciparum and 194 cases caused by non-falciparum parasites. Compared with black patients, Asians had an 8.05-fold higher risk (95% CI; 2.93-22.1-fold) of developing severe falciparum malaria; whites had an 8.20-fold higher risk (95% CI; 2.94-22.9-fold). Blacks also were less likely to have an unfavorable outcome from disease or a prolonged hospital stay.

There were six fatalities from falciparum malaria among patients in the study; none of those patients were black.

Patients with parasitemias of ≥2% were 12 times more likely to acquire severe falciparum malaria and stayed in the hospital 50% longer than patients with parasitemias <2%.

The researchers observed a reduced risk of severe falciparum malaria (OR 0.35; 95% CI; 0.15-0.80) among participants of all ethnicities with a history of clinical malaria.

Clin Infect Dis. 2009;48:871-878.

The recent article by Phillips et al provides evidence that, among travelers to malaria-endemic areas of the world, black patients may be more resistant to severe falciparum malaria. Asian and white patients show higher rates of susceptibility. Higher levels of parasitemia (≥2%) predicted severe falciparum malaria in the population. Malaria continues to threaten international travelers to many regions of the developing world. More than 1,000 American travelers a year become infected during trips, resulting in a small number of deaths. A majority of these infections occur in sub-Saharan Africa. Ethnicity of international travelers perhaps should be considered in developing malaria prevention strategies for persons entering malaria endemic areas during international travel. Malaria prevention methods currently rely on mosquito avoidance and anti-malaria chemoprophylaxis.

– Herbert L. DuPont, MD

Infectious Disease News Editorial Board member