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. Histopathological 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 co-infection with other Plasmodium species in placental and peripheral blood. Leukocytes and monocyte/macrophages were detected in placental sections by immunohistochemistry.Results. Mono-infection by P. vivax and P. falciparum was detected by qPCR in eight and ten placentas, respectively. Seven of the eight women with P. vivax placental mono-infection were negative in peripheral blood. By histology, three placentas with P. vivax mono-infection showed parasitized erythrocytes in the intervillous space but no hemozoin in macrophages nor increased intervillous inflammatory cells. In contrast, seven placentas positive for P. falciparum presented parasites and hemozoin in macrophages or fibrin as well as intervillous inflammatory infiltrates.Conclusions. P. vivax can be associated with placental infection. However, placental inflammation is not observed in P. vivax mono-infections, suggesting other causes of poor delivery outcomes associated with P. vivax infection