Fatal malaria infection in travelers: novel immunohistochemical assays for the detection of Plasmodium falciparum in tissues and implications for pathogenesis.

Plasmodium falciparum is a significant cause of morbidity and mortality in travelers to areas where the parasite is endemic. Non-specific clinical manifestations may result in failure to recognize malaria until autopsy, when it is often too late to obtain whole blood for microscopic evaluation. The use of immunohistochemical (IHC) assays in the detection of three P. falciparum antigens, histidine rich protein-2 (HRP-2), aldolase, and Plasmodium lactate dehydrogenase (pLDH), was evaluated in formalin-fixed paraffin-embedded autopsy tissues from five travelers to malaria-endemic areas, whose deaths were initially suspected to have been caused by other bacterial or viral hemorrhagic fevers. The HRP-2 assay was specific for P. falciparum, whereas the aldolase and pLDH assays also reacted with P. vivax. Immunostaining patterns were predominately cytoplasmic and membranous. P. falciparum antigens were detected in a variety of organs but were most abundant in the blood vessels of brain, heart, and lung tissues.