Answer to Case 595

Answer toParasite Case of the Week 595:Plasmodium vivaxwith exflagellated microgametocytes. Free microgametes are seen.The following excellent description was written by Marc Couturier and Blaine Mathison, the contributors of this case.There are several features of this slide that are supportive forP. vivax.First, many of the infected cells are reticulocytes (which are larger than mature RBCs), whichP. vivaxandP. ovalehave predilection to infect. Second, the gametocytes are enlarged and fill almost the entire space within the parasitized RBC. Some of the infected RBCs also take the shape of neighbouring RBCs (distorted, pleomorphic); particularly in the areas where cells are dense. Third, the mature schizonts contained upwards of 18-20 merozoites with yellowish brown pigment present, which strongly points towardP. vivax, since the range of P. ovale tends to reach 14 merozoites at maximum. Fourth, some developing trophozoites were grossly amoeboid.Plasmodium ovaleusually demonstrates some amoeboid characteristics, but it is usually more exaggerated withP. vivax. Notice also none of the infected RBCs were fimbriated (which, when present supportsP. ovalebut the absence of which does not rule-out P. ovale).In the images provided, there was an absence of Sch üffner’s stippling. There were some parasitized cells that did display stippling (not shown), but the majority did not. It is important to remember that stippling can be helpful to support an identification, but the absence...
Source: Creepy Dreadful Wonderful Parasites - Category: Parasitology Source Type: blogs