First Report of Neutrophil Involvement of Exflagellated Plasmodium vivax Microgametes

Dear editor Malarial infections pass through multiple stages, beginning in the hepatic parenchymal cells where invading sporozoites mature into schizonts. On maturation, these schizonts rupture and release merozoites into the bloodstream, which, in turn, target erythrocytes, leading to the clinical manifestations of the disease [1]. Exflagellation is characterized by thin, flagella-shaped microgametes emerging from male malaria gametocytes; occurs in the midgut of the Anopheles mosquito; and has rarely been observed in peripheral blood specimens. Here, we present a case of Plasmodium vivax infection characterized by exflagellation of microgametes and accompanied by the unusual presence of exflagellated microgametes within the cytoplasm of peripheral leukocytes. To the best of our knowledge, this is the first report of neutrophil involvement of exflagellated Plasmodium. A pregnant 26-yr-old Pakistani woman presented with a fever >40°C lasting for 7 days. The patient, who arrived from Pakistan 10 days previously, had no medical history of malarial infection. She had been treated with non-steroidal anti-inflammatory drugs (NSAIDs), without improvement of symptoms, 4 days prior to her arrival at a local hospital. At presentation, the patient appeared acutely ill. Her blood pressure measured 90/50 mmHg, and body temperature was 37.2°C. Complete blood cell and differential counts revealed anemia with thrombocytopenia (white blood cell [WBC] 6.61× 10/L, hemoglobin 9.7 g/dL, platelets 64×10/L) and leukoerythroblastic changes (nucleated red blood cell [nRBC] 1/100 WBC). Peripheral blood smears were performed within 40 min of the blood draw and revealed P. vivax-infected erythrocytes (Fig. 1). Parasite density was determined to be 20887.6/μL. A malaria Pf/ Pv strip (Asan Pharmaceutical, Whasung, Korea) yielded a positive result for only P. vivax antibodies. Malaria nested PCRs (Eone Laboratory, Incheon, Korea) revealed P. vivax only. In addition, 15-20 μm filamentous microgametes containing round-to-ovalshaped chromatin structures were observed. Some microgametes were distributed outside of the RBCs, while others appeared exflagellated from the gametocyte. Some microgametes were observed within the cytoplasm of neutrophils. Neutrophils containing microgametes exhibited phagosomes within the cytoplasm and/or nuclear condensation and ruffled plasma membranes (Fig. 2). Quinine sulfate and clindamycin treatment were commenced, instead of primaquine, owing to the pregnancy. Two days later, another blood smear was performed immediately after collection. Schizonts and gametocytes remained in the blood; however, no microgametes were observed. Follow-up peripheral blood morphologic examinations were performed 9 days after initial diagnosis and showed no malarial parasites. Four days later, the patient underwent an abortion due to the death of the