Plasmodium Vivax in Thick and Thin Films
Schüffner's dots in Thin Smear
Background Information of Plasmodium Vivax
Plasmodium Vivax is the most common and widely distributed protozoal parasite that infects humans, but fortunately it is the less virulent than Plasmodium Falciparum. P. vivax is carried by the female Anopheles mosquito, since it is only the female of the species that bite. The West Africans are almost safe from this infection as their RBCs do not posses Duffy Antigen which is the mode of RBC infection. It has an incubation period of 10-17 days and a periodicity of 48 hours
The hall mark of Plasmodium Vivax infection is enlarged RBCs that maybe round/oval but often adopting bizarre shapes due to parasitic activity. Presence of Schüffner's dots (golden brown/pinkish-red) scattered through out the RBC cytoplasm is a signature characteristic to this species.
The parasite within it is often wildly irregular in shape (described as "amoeboid"). Schizonts of P. vivax have ~20 merozoites within them. It is rare to see cells with more than one parasite within them. Merozoites will only attach to immature blood cell (reticulocytes) and therefore it is unusual to see more than 3% of all circulating erythrocytes parasitised.