COCCIDIA 511 



The coccidium has a complicated developmental history, and 

 infection only seems possible in one of the stages. In order to study 

 the life -cycle the parasite must be placed under suitable conditions, 

 and an infusion of rabbits' faeces, kept at the ordinary temperature, 

 is perhaps as good a cultivating medium as any, the changes being 

 watched by means of interlamellar films. Reproduction may be 

 either asexual or sexual, and may be endogenous, within the host, 

 or exogenous, outside the host. In the asexual cycle, division of 

 the protoplasm and nucleus of the coccidium takes place and the 

 cyst comes to contain large numbers of spores (Fig. 58, A). The 

 cyst-wall then ruptures, the spores are liberated, pass into other 

 intestinal or hepatic cells and reproduce the coccidium once more 

 (Fig. 58, A). In the sexual cycle, the protoplasm of some coccidia 

 remains undivided with a single nucleus and the cyst has a weak 

 spot, known as the micropyle ; these are the female cells or macro- 

 gametes (Fig. 58, B). In other coccidia, the protoplasm having 

 attained maximum growth, divides into a mass of actively motile 

 thread-like bodies, the male elements or microgametes. The cyst- 

 wall then ruptures and the microgametes, penetrating the micropyle 

 of the macrogametes, fertilize them. In the fertilised macrogamete, 

 which is a zygote known as an " oocyst " and is non-motile, the 

 micropyle closes and the cyst is discharged with the faeces of the 

 animal. On damp ground, the nucleus and protoplasm divide 

 into four spherules. Each spherule becomes elongated, and again 

 divides into two somewhat crescent-shaped bodies, around each 

 pair of which a new, somewhat spindle-shaped capsule forms (Fig. 

 58, D). In this condition the parasite is very resistant, and may 

 remain alive for six months, undergoing no further change unless 

 introduced into another animal. If a young rabbit swallows with 

 its food these crescentic spores, the enclosing capsule is dissolved, 

 and each crescent becomes a rounded amoeboid mass, and this 

 again divides up into many crescentic spores. These spores are 

 apparently motile, and enter the epithelial cells of the intestine, 

 gall-bladder, and bile-ducts, where a process of growth and 

 differentiation occurs, and the fully developed parasite is ultimately 

 reproduced. 



Coccidial disease, or, as it is sometimes termed, psorospermosis, 

 is occasionally met with in animals, as the sheep, and a wasting 

 disease of young pheasants due to coccidia has been described by 

 McFadyean. 1 Coccidiosis also occurs in grouse and poultry, due 

 to Eimeria avium ; in the latter causing " scour," which may be 

 attended with considerable loss. 



1 Journ. Comp. Path, and Therapeut., 1895. 



