COCCIDIA. 233 



SPOROZOA. 



This class of Protozoa gets its name from the method of reproduction 

 sporulation. These parasites rarely show binary fission. While 

 the sporozoa are found within cells, in the tissues and in internal cav- 

 ities, as intestine and bile ducts, yet it is as inhabitants of the blood that 

 they have their greatest importance for man -these are known as 

 Haemosporidia. A sporozoon may be either naked or amceboid or be 

 covered with a distinct cuticle. 



NOTE. Sporozoa are divided into two subclasses the Telosporidia and the Neo- 

 sporidia. In the former the vegetative activity of the protozoon goes on to full growth 

 at which time the reproductive activity commences. With the Neosporidia, 

 however, the growth and reproduction go on at the same time. 



Among the Telosporidia we have the orders Gregarinaria, Coccidiaria, and 

 Haemosporidia 



Gregarines are chiefly parasites of arthropods and worms and are not known 

 for man or the higher vertebrates. 



The subclass Neosporidia is practically of no importance in human parasitology, 

 only the order Sarcosporidia having been reported for man. From an economic 

 standpoint, however, the order Myxosporidia is of great importance Nosema being 

 the cause of pebrine, a disease destructive to the silkworm. In this the eggs of an 

 infected N. bombycis may be infected. 



Coccidiaria. 



The parasites of the order Coccidiaria are almost exclusively found in the intes- 

 tines and in the organs connected with it. In the vegetative stage it lives within an 

 epithelial cell, which it destroys. Afterward it falls into the lumen lined by this 

 epithelial cell and sporulates, either by the method of schizogony or sporogony. 



Owing to their egg-like shape, coccidia have often been considered as the ova of 

 intestinal parasites, and vice versa. Upon swallowing an oocyst with its contained 

 sporozoites the membrane of the oocyst is digested in the duodenum and the sporo- 

 zoites liberated. They enter epithelial cells, as of intestine, and reproduce by 

 schizogony. After a varying number of nonsexual cycles sporogony commences, 

 sporonts being produced instead of schizonts. The female sporont is fertilized by 

 the microgamete which is an elongated body provided with two flagella. These 

 microgametes are formed from the male sporont and when thrown off from the 

 periphery they enter (usually a single one) the macrogamete. After fertilization a 

 resistant membrane is formed and the term oocyst is used. Within the oocyst 

 are found smaller cysts, the sporocysts, in which the sporozoites are formed. 



The cycle is very similar to that of malaria except that no arthropod host is 

 required for the sexual cycle. The spores which are formed in schizogony are known 

 as merozoites. 



Merozoites may best be distinguished from sporozoites by the presence of a 

 nuclear karyosome, this being absent in sporozoites. In Eimeria we have the 

 oocyst containing four sporocysts with two sporozoites in each sporocyst while in 

 Isospora we have an oocyst containing two sporocysts with four sporozoites in each. 



Eimeria stiedae. This sporozoon is usually known as the Coccidium cuniculi 



