Schuffner's dots are seen in infection due to

Plasmodium vivax induces morphologic alterations in infected host erythrocytes that are visible by light microscopy in Romanowsky-stained blood smears as multiple brick-red dots.  These morphologic changes, referred to as Schüffner's dots, are important in the identification of this species of malarial parasite and have been associated by electron microscopy with caveolae vesicle complexes along the erythrocyte plasmalemma. Ref :https://en.wikipedia.org/wiki/Sch%C3%BCffner%27s_dots#:~:text=Sch%C3%BCffner's%20dots%20refers%20to%20a,Plasmodium%20ovale%20or%20Plasmodium%20vivax