Examination of plasmodium parasites in bone marrow puncture fluid for the diagnosis of imported-malaria in patients from the Yunnan Province, China

Background: Some suspected malaria individuals who have returned to Yunnan from Africa have been delayed antimalarial treatment due to not detection out Plasmodium infection in their peripheral blood. Methods: The fever patients with a history of exposure to malaria endemic areas and suspected malaria episodes accepted the detection of the Plasmodium infection in bone marrow fluid by microscopy and gene testing. Results: Plasmodium in bone marrow fluid were found in all of five patients, including four patients with Plasmodium negative and one patient with Plasmodium falciparum positive in peripheral blood. The proportion of found ring stage, large trophozoites, schizonts, and stage III-V gametocytes accounted for 28.3%, 38.3%, 4.8%, 11.5%, 16.5% and 0.8%, respectively. The erythrocyte count and hemoglobin concentration of the five cases post-treatment merely increased to the lower end of the normal range. Platelet count returned to the normal range, increasing by 466%, 378%, 252%, 168% and 35%, respectively. There were four to five B-cell antigenic epitopes along pLDH peptide chains of the infected strains in the five cases. Of note, the sequence of “211-EEVEGIFDR-220” was only detected in P. vivax strain, whereas the sequence of “207-LISDAE-213” was unique for P. falciparum strain. Conclusion: Examination of the Plasmodium in bone marrow puncture fluid could make up for the missed diagnosis of malaria that solely relies on peripheral blood.