All of 17 calves 1 to 21 days old and 23 of 24 1-day-old pigs inoculated orally with calf feces containing cryptosporidia oocysts became infected with cryptosporidia. Infectivity was maintained by discontinuous passage in calves, with storage in potassium dichromate solution for up to eight weeks between passages. Cryptosporidia shed in calf feces also were infectious for calves directly after collection, without storage in potassium dichromate (two calves). Infected calves and pigs shed cryptosporidia oocysts in their feces for several days (mean of 10 days). Those necropsied at this stage of infection had many cryptosporidia and partial atrophy of villi in their ilea. All of the pigs and 60% of the calves also had cryptosporidia infections in their large intestines at this stage. It was concluded that calf cryptosporidia can be transmitted via feces to calves and to pigs.
Abstract. Transmission and scanning elcctron microscopy of the ileal mucosae from 12 calves infected with Cryptosporidiurn sp. showed cryptosporidia free in the lumen and attached to epithelium. The attached parasites were interpreted to bc extracellular and adherent to the microvillous border of epithelial cells. Stages of the organism included crescentic-free merozoites, trophozoites. sehizonts, gametes and oocysts. Attached parasites were detected chiefly at villous tips and all stages were present o n a single villus. Attachment sites were characterized by absence or disintcgration o f microvilli. disorganization of the terminal web and development of a spccialized attachment zone. There were increased numbers of lysosomes and irregularities in the nuclear membrane of parasitized epithelial cells. It was concluded that cryptosporidia exist in bovine intestine as extracellular parasites and cause epithelial changes that in turn probably cause or contribute to diarrheal disease.Cryptosporidia are coccidia of the suborder Eimeriorina, family cryptosporidiidae and the genus Cryptosporidiurn [9]. They are reported to occur in reptiles (81, chickens [3], turkeys [19], geese [17], mice [21-231, rabbits [6, 241, guinea pigs (4, 24, 251, lambs 111, calves [ l , 11, 12, 14, 15, 16, 181, swine 161, monkeys 12, 71, and man [ l o , 131. These parasites are thought to be host specific. It is not known if cryptosporidia are pathogenic. In calves, however, they are commonly associated with diarrhea.The complete life cycle of this protozoan is not known. In guinea pigs, trophozoites, schizonts in their first (eight merozoites) and second (four merozoites) generation and gametes with electron dense polysaccharide granules were seen within intestinal epithelial cells (251. In calves, oocysts attached to epithelial cells were found 11, 151 and free merozoites in the ileal contents and oocysts in feces were seen [lS]. There is controversy as to whether these protozoa are attached to epithelial cells [8,20, 221 or whether they are intracytoplasmic [7,25].
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