170 THE ANIMAL PARASITES OF MAN 



stippling (Maurer's dots) ; (4) the gametocytes, or sexual forms, are 

 crescentic in shape. 



]. W." W. Stephens (1914) has described a new malarial parasite of 

 man ; it is called Plasmodium tenne. It is very amoeboid, with scanty 

 cytoplasm and much chromatin, sometimes rod-like or irregular. 

 The parasite was described from a blood-smear of an Indian child. 

 The creation of a new species for this parasite has been criticized by 

 Balfour and Wenyon, and by Craig. 



Plasmodium relictum, Sergent, 1907. 



Syn. : Plasmodium prcecox, Grassi and Feletti, 1890 ; Plasmodium danilewskyi, 

 Gr. et Fel., 1890 ; Hcemamceba relicta^ Gr. et Fel., 1891 ; Proteosoma grassii, 

 Labbe\ 1894. 



Hsemamceboid, pigment-producing, malarial parasites are often found in birds. 

 Like the human malarial parasites they have been variously named. Labbe created 

 the genus Proteosoma for them, and this name is still often used as a distinctive one 

 unofficially. The correct name is stated to be either Plasmodium relictum or 

 P. pracoX) or possibly even P. danilewskyi, assuming that there is only one species. 

 The nomenclature of the malarial parasites is most confused. The avian malarial 

 parasites are transmitted by Culicine mosquitoes. 



The organism was discovered by Grassi in the blood of birds in Italy, and causes 

 a fatal disease in partridges in Hungary. Sparrows are affected in India, and it 

 was this Plasmodium in which Ross first traced the development of a malarial 

 parasite in a mosquito. The parasite may be transmitted from bird to bird by 

 blood-inoculation, canaries being very susceptible. 



The principal stages of the avian plasmodium closely resemble those of the 

 malarial parasites of man. In its earliest stage P. relictum is unpigmented, 

 but soon the trophozoite grows and becomes pigmented, meanwhile displacing 

 the nucleus of the avian red-blood corpuscle, a characteristic feature, distinguish- 

 ing it from Halteridium. Schizonts are formed, each of which gives rise to 

 about nine merozoites in the circulating blood. Sexual forms or gametocytes also 

 occur in the blood. These develop in Cule.r fatigans, C. pipiens and C. nemor- 

 osus. Ookinetes or vermicules are formed in twelve to fifteen hours in the 

 stomach of the mosquito, and in one to two days well-developed round oocysts may 

 be seen. In three to four days sporoblasts have formed within the oocysts and 

 young sporozoites begin to develop. 'In nine to ten days the oocysts are mature, 

 being filled with sporozoites. The oocysts then burst and the sporozoites travel 

 through the thoracic muscles to the salivary glands of the Culicine. 



Neumann, experimenting with canaries, found that Stegomyia jasciata could 

 transmit the infection, but less efficiently than species of Culex. 



THE CULTIVATION OF MALARIAL PARASITES. 

 The successful cultivation of malarial parasites in vitro was first 

 recorded by C. C. Bass and by Bass and Johns (191 2). : Since then, 

 J. G. and D. Thomson, 2 and McLellan (1912-13), Ziemann 3 and others 

 have repeated the experiments. 



1 Journ.Exptl. Med. y xvi, p. 567. 



2 Annals Trop. Med. and Parasitol. , vi, p. 449; vii, pp. 153, 509. 



3 Trans. Soc. Trop. Med. and Hyg., vi, p. 220. 



