An Unusual Feature of Malaria: Exflagellated Microgametes of Malarial Parasites in Human Peripheral Blood / 대한임상미생물학회지

Exflagellation of the malaria parasite microgametocyte usually occurs in the gut cavity of Anopheles mosquitoes following an infective blood meal. Exflagellation is a very rare event in human blood. Due to its rarity, the appearance of this structure in a peripheral blood smear will easily create a diagnostic dilemma. We report a case of malaria with exflagellated microgametes in human blood that was initially mistaken for a double infection of Plasmodium and another blood flagellate. The patient was a 29-year-old Parkistani man presenting with fluctuating fever accompanied by chills and fatigue for 4 days. Initial peripheral blood smear examination showed a number of Plasmodium ring forms, trophozoites, and gametocytes. Additionally, several filamentous structures resembling blood flagellates were seen. With these features, an initial diagnostic impression of combined infection of malaria and blood flagellate was made. Later, we determined that these structures resembling blood flagellates were exflagellated microgametes of malarial parasite. Therefore, the knowledge that exflagellation may appear in human blood with Plasmodium species infection and being more familiar with differentiation of the morphologic features of other species infection can prevent further possible misinterpretation.

In vitro Observation on Effect of Nitric Oxide on Exflagellation of Plasmodium yoelii / 中国寄生虫学与寄生虫病杂志

Objective To observe the effect of nitric oxide (NO) on exflagellation of malaria parasite. Methods The level of parasitemia and gametocytemia in DBA/2 mice infected with Plasmodium yoelii 17XL was measured by scanning Giemsa-stained blood smears, and the NO level in culture supernatant of splenocytes was checked using Griess reaction. The mice were injected with different doses of NO donor (NOC5) on day 4 post-infection, and control mice were injected with NOC5 precursor. On day 6 post-infection, mice were injected with NOS inhibitor (L-NMMA), and control mice were injected with D-NMMA and PBS, respectively. Blood samples were collected from tail vein of mice before injection, 30 and 60 min after being injected with NOC5 and NOC5 precursor, 4 and 8 h after being injected with L-NMMA, D-NMMA, and PBS respectively. Exflagellation number of gametocytes in blood culture was counted under microscope. Results The NO level in culture supernatant of splenocytes from mice on day 4 and 6 post-infection was 16.5 mmol/L and 30.4 mmol/L, and exflagellation number was 11.33 and 0.66, respectively. The number of exflagellation in parasitized erythrocytes, obtained from mice on day 4 post-infection, was 5.33 and 2.66, respectively, 30 and 60 min after injection of 1 mg NO donor (NOC5), significantly lower than that of the control (P