498 Coccidia in the Intestines. 



iiit; to environment. The oocysts are very resistant ami can remain alive after putre- 

 factive processes lasting for three months (Defjoix). After oocysts have been in- 

 gested their membrane is dissolved by the digestive juices, particularly by the pan- 

 creatic juice (according to Ziiblin in 6 to <S hours), they are set free and then form 

 the lively motile sporozoites which penetrate into the intestinal epithelia and assume 

 a roundish form, being then found betvceen the cell margin and the nucleus. They 

 enlarge gradually and become schizontes, which multiply asexually (schizogony) by 

 forming numerous spindle-shaped merozoites. After the dissolution of the infected 

 epithelial cells these get into the intestinal lumen and invade new epithelial cells; 

 the process of schizogony is repeated several times; some merozoites situated in 

 epithelial cells then change into macrogametes ami nuerogametes. After the latter 

 havG become free they penetrate into macrogametes with active motility, fertilize 

 these and form again an oocyst (sporogony). Whether asexual multiplication may 

 also occur outside of an animal host is not known, but Ziiblin believes that it is 

 possible. 



The infection is spread by the water of pools and marshes, 

 also probably by feed which has come in contact with infected 

 water. (Zschokke claims that the coccidia tirst i^-et into snails 

 and that the latter infect the water or feed.) The possibility 

 of infection in the barn is suggested by the fact that isolated 

 cases also occur in winter in infected regions, also by the occur- 

 rence of coccidiosis among other species of animals which are 

 not pastured, and by an observation of Ziirn that calves became 

 infected which had been confined permanentlj^ to the barn. 

 Damp and dirty barns undoubtedly are particularly dangerous. 



Three young cattle, experimentally fed on material containing sporozoites fell 

 sick after three weeks with the symptoms of acute intestinal catarrh, with diarrhea 

 and few coccidia in the feces, but without any blood. These symptoms lasted three 

 days (Guillebeau). The disease cannot be transferred by non-sporozoitic oocysts. 

 Ziiblin did not succeed in infecting rabbits with coccidia from cattle that were 

 suffering from red dysentery. 



The susceptibility is greatest in youth, up to the second 

 year of life, but older cattle likewise contract the disease, al- 

 though more rarely. The great rarity of the disease among 

 calves less than six months old may be explained by the fact 

 that these animals are usually not pastured. Isolated cases 

 have, however, been observed among calves three to six weeks 

 old (Ziirn, Bugge, Waringsholz & Sieg). 



Pathogenesis. The sporozoites escaped from the ingested 

 oozytes, wander with the intestinal contents toward the anus and 

 penetrate into the epitlielial cells of the crypts of Lieberkiilm of 

 the large intestine, particularly into those of the rectum. They 

 multiply rapidly by schizogony and the epithelial cells of the 

 surrounding glands and those of the mucosa in general are in- 

 vaded by autoinf ection ; in this manner an increasing area 

 of the mucosa becomes affected; the usual localization of the 

 changes in the large intestine is attributed by Ziiblin to a com- 

 paratively slow solution of the oocyte membrane and to a rapid 

 passage of the contents of the small intestine into the 

 large intestine. It is, however, remarkable that the small in- 

 testine is also profoundedly affected in young calves and that 



