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Imported Non-Falciparum Malaria in Europe

A long latency period and low parasite density can delay diagnosis of non-falciparum malaria.

Most malaria deaths are caused by Plasmodium falciparum malaria, yet other malaria infections can also be severe. Investigators in Belgium recently completed a prospective study of patients with non-falciparum malaria seen between April 2000 and March 2005.

Of 98 single-species infections (identified by stained blood smear examination), 48 (49%) were P. vivax, 34 (35%) were P. ovale, and 16 (16%) were P. malariae. Sixty-two percent of the infections were in travelers, 18.5% in expatriates, and 19.5% in foreign visitors. All patients with P. ovale or P. malariae malaria had been infected in Africa; most patients with P. vivax malaria (67%), in Asia. The interval between leaving a malaria-endemic area and symptom onset was <4 months for 62%, 4–6 months for 20%, 7–12 months for 13%, and >12 months for 5%. Latency was longer in patients who had adhered to malaria chemoprophylaxis than in those who had not.

Signs, symptoms, and routine laboratory tests were not helpful in differentiating among the species. Thrombocytopenia was found in 62% of the patients. Eight of 48 P. vivax episodes represented relapses in patients who had previously received primaquine at the dose then standard. The parasite density was significantly lower in patients with P. ovale malaria and in those taking antimalarials. Nearly 25% of patients required hospitalization; no deaths or serious complications occurred. Rapid diagnostic tests performed poorly in identifying non-falciparum malaria, especially in patients with low parasite density.

Comment: Of the estimated 30,000 cases of travel-associated malaria annually, a quarter to more than half (depending on the clinic location) are caused by non-falciparum species. Microscopy remains the gold standard for diagnosing malaria but requires expertise unavailable in many laboratories. PCR assays may become available in the future to aid diagnosis.

— Mary E. Wilson, MD

Published in Journal Watch Infectious Diseases August 2, 2006

Citation(s):

Bottieau E et al. Imported non–Plasmodium falciparum malaria: A five-year prospective study in a European referral center. Am J Trop Med Hyg 2006 Jul; 75:133-8.

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