262 



PLASMODIUM, HAEMOPROTEUS AND LEUCOCYTOZOON 



4 for P. cynoniolgi and P. inui (Bano, 

 1959). 



Cultivation : Various species of 

 Plasniodiiun have been cultivated in fluid 

 media (Trager, 1947; Anfinsen el al. , 

 1946; Geiman el al. , 1946) and in avian 

 embryos and tissue culture (see Pipkin 

 and Jensen, 1958 for a review). 



HUMAN MALARIA 



The following discussion of human 

 malaria is necessarily brief. Further 

 details and references can be found in any 

 textbook of human parasitology and, in 

 more detail, in Boyd (1949) and Mac- 

 donald (1957). 



Man has 4 recognized species of 

 Plasmodium . P. falciparum (Welch, 

 1897) Schaudinn, 1902 is the cause of ma- 

 lignant tertian, aestivo-autumnal or fal- 

 ciparum malaria. Paroxysms of chills 

 and fever occur every other day (i. e. , on 

 days 1 and 3, which accounts for the name 

 "tertian"). The ring forms are about 

 1/6 to 1/5 the diameter of a red blood 

 cell. The schizonts and merozoites 

 ("segmenters") rarely occur in the peri- 

 pheral circulation, but are found in 

 clumped erythrocytes in the viscera. The 

 schizonts are usually compact and 

 rounded, with coarse, blackish pigment. 

 The segmenters occupy 2/3 to 3/4 of the 

 host cell and form 8 to 32 merozoites. 

 The host erythrocyte is not enlarged but 

 contains reddish clefts known as Maurer's 

 dots and may also have bluish stippling. 

 The macrogametes and microgametocytes 

 are crescent- or bean-shaped, with pig- 

 ment granules clustered around a central 

 nucleus or scattered except at the poles. 

 The microgametocytes have pale blue cyto- 

 plasm and a relatively large, pink nucleus 

 when stained with Giemsa's stain. The 

 macrogametes have darker blue cytoplasm 

 and a more compact, red nucleus. 



Plasmodium fif ax (Grass i and Feletti, 

 1890) Labbe', 1899 is the cause of benign 

 tertian or vivax malaria. Paroxysms 



occur every other day as in falciparum 

 malaria. The ring forms are about 1 '3 to 

 1/2 the diameter of the host cell. The 

 schizonts are highly active and sprawled 

 out irregularly over the host cell, with 

 small, brown pigment granules usually 

 collected in a single mass. The host cell 

 is enlarged, pale, and contains red dots 

 known as Schuffner's dots. The segment- 

 ers nearly fill the host cell and produce 

 15 to 20 or occasionally up to 32 irregu- 

 larly arranged merozoites. The macro- 

 gametes and microgametocytes are 

 rounded, 10 to 14fi in diameter (i. e. , 

 larger than normal erythrocytes), and have 

 fine, brown, evenly distributed pigment 

 granules. The microgametocytes have 

 pale blue cytoplasm and a relatively large, 

 pink nucleus when stained with Giemsa's 

 stain. The macrogametes are slightly 

 larger, with darker blue cytoplasm and a 

 small, red nucleus. 



Plasmodimn malariae (Laveran, 1881) 

 Grassi and Feletti, 1890 is the cause of 

 quartan or malariae malaria. This species 

 also occurs naturally in chimpanzees in 

 West Africa (Garnham, 1958). Paroxysms 

 occur every 3 days (i. e. , on days 1 and 4). 

 The ring forms are similar to those of P. 

 vivax. The schizonts are more compact 

 and rounded or are drawn out in a band 

 across the host cell; their pigment gran- 

 ules are blacker and coarser than those of 

 P. vivax. The host cell is not enlarged 

 and does not contain Schuffner's dots. The 

 segmenters nearly fill the host cell and 

 produce 6 to 12 (usually 8 or 9) merozoites 

 arranged in a rosette. The macrogametes 

 and microgametocytes are rounded and 

 smaller than those of P. vivax. They do 

 not quite fill the host cell and contain 

 blacker and coarser pigment granules. 



Plasmodium ovale Stephens, 1922 is 

 a rare species which causes a tertian type 

 of malaria. Its ring forms are similar to 

 those of P. vivax. The schizonts are 

 usually round, with brownish, coarse, 

 somewhat scattered pigment granules. The 

 host cell is oval, often fimbriated, not 

 much enlarged, and contains Schuffner's 

 dots. The segmenters occupy 3/4 of the 

 host cell and produce 8 to 10 merozoites 



