Placental infection with Plasmodium vivax: a histopathological and molecular study.

BACKGROUND Evidence of the presence of Plasmodium vivax in the placenta is scarce and inconclusive. This information is relevant to understanding whether P. vivax affects placental function and how it may contribute to poor pregnancy outcomes. METHODS Histopathologic examination of placental biopsies from 80 Papua New Guinean pregnant women was combined with quantitative polymerase chain reaction (qPCR) to confirm P. vivax infection and rule out coinfection with other Plasmodium species in placental and peripheral blood. Leukocytes and monocytes/macrophages were detected in placental sections by immunohistochemistry. RESULTS Monoinfection by P. vivax and Plasmodium falciparum was detected by qPCR in 8 and 10 placentas, respectively. Seven of the 8 women with P. vivax placental monoinfection were negative in peripheral blood. By histology, 3 placentas with P. vivax monoinfection showed parasitized erythrocytes in the intervillous space but no hemozoin in macrophages nor increased intervillous inflammatory cells. In contrast, 7 placentas positive for P. falciparum presented parasites and hemozoin in macrophages or fibrin as well as intervillous inflammatory infiltrates. CONCLUSIONS Plasmodium vivax can be associated with placental infection. However, placental inflammation is not observed in P. vivax monoinfections, suggesting other causes of poor delivery outcomes associated with P. vivax infection.