CHAPTER XV 

 THE LIFE CYCLE OF THE COCCIDIA 



TECHNICAL SUGGESTIONS 



The most readily available species for the study of the life cycle 

 of a coccidian are Eimeria stiedce and E. verforans from the rabbit, 

 the former from the liver and the latter from the intestine. By some 

 writers the two are considered identical and the following laboratory 

 outline is applicable to either. 



Infections may be detected by examining the feces of laboratory 

 rabbits, even if acute cases are not available. The oocysts may be 

 concentrated by breaking up the feces in water, sedimenting repeat- 

 edly, and straining out the coarser particles. They are then cultured 

 to the infective stage in Petri dishes under a thin layer of 4 per 

 cent potassium bichromate solution to prevent mold. Andrews, 1926, 

 comminuted heavily infected feces in 1 per cent chromic acid, cultured 

 for a week or so, strained out the coarsest particles of feces through 

 cheesecloth and then through batiste, and finally floated up the 

 oocysts by saturation with sodium chloride. If acute cases are 

 available the animal may be killed and the oocysts recovered by scrap- 

 ing the infected mucosa, thoroughly shaking the scrapings to remove 

 the oocysts, and then centrifuging gently for one or two minutes so that 

 the oocysts are thrown down while the cell debris remains suspended. 

 Freshly recovered oocysts as well as those which have undergone 

 development to the infective stage should be preserved in 10 per 

 cent formalin for class study. 



Others should be administered, in food or by drenching, to young 

 rabbits, in which acute cases of coccidiosis may be induced for further 

 study. For critical work Andrews administered known numbers of 

 the oocysts by means of a stomach tube. Portions of the diseased 

 liver or intestine, dependent upon the species of parasite, should be 

 fixed in saturated corrosive sublimate solution and in picro-formol, 

 sectioned, and stained in hsemotoxylin and eosin. 



In lieu of rabbit material young chickens often afford an abundant 

 supply of Eimeria avium. Myriapods of the genus Lithobius com- 

 monly harbor Eimeria schubergi, but it is generally associated with 

 other forms which may confuse the study of it. English sparrows 

 commonly yield a species of Isospora and others of this genus are 

 readily obtainable from cats, dogs, foxes, and various other mammals. 



CHARACTERISTICS OF THE COCCIDIA 



The Coccidia are cell-infesting Sporozoa which typically 

 reproduce intracellularly by asexual spore formation (schizogony) 



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