A Comparison of Endogenous Development of Three Isolates of Cryptosporidium in Suckling Mice¹

Abstract

Suckling mice were used as a model host to compare the endogenous development of three different isolates of Cryptosporidium: one from a naturally infected calf, one from an immunocompetent human with a short-term diarrheal illness, and one from a patient with acquired immune deficiency syndrome (AIDS) and persistent, life-threatening, gastrointestinal cryptosporidiosis. After oral inoculation of mice with oocysts, no differences were noted among developmental stages of the three isolates in their sites of infection, times of appearance, and duration, morphology, and fine structure. Sporozoites excysted within the lumen of the duodenum and ileum, penetrated into the microvillous region of villous enterocytes, and developed into type I meronts with six or eight merozoites. Type I merozoites penetrated enterocytes and underwent cyclic development as type I meronts or they became type II meronts with four merozoites. Type II merozoites did not exhibit cyclic development but developed directly into sexual forms. Microgamonts produced approximately 16 small, bullet-shaped microgametes, which were observed attaching to and penetrating macrogametes. Approximately 80% of the oocysts observed in enterocytes had a thick, two-layered wall. After sporulating within the parasitophorous vacuole, these thick-walled oocysts passed through the gut unaltered and were the resistant forms that transmitted the infection to a new host. Approximately 20% of the oocysts in enterocytes consisted of four sporozoites and a residuum surrounded only by a single oocyst membrane that ruptured soon after the parasite was released from the host cell. The presence of thin-walled, autoinfective oocysts and recycling of type I meronts may explain why a small oral inoculum can produce an overwhelming infection in a suitable host and why immune deficient persons can have persistent, life-threatening cryptosporidiosis in the absence of repeated oral exposure to thick-walled oocysts.

Ultrastructural Details of Cryptosporidium parvum Development in Calf Intestine

“…Although in the last few years we have obtained many ultrastructural images of this Cryptosporidium in cultured MDCK cells (Rosales et al 1993b), chick embryos ) and in calf tissues (Mascaró et al 1993), we have never found, either in sporozoites or in merozoites cuts, micronemes arranged in parallel stacks or in zigzag patterns as so clearly described by other authors (Current & Reese 1986, Liebler et al 1986, Fayer et al 1990, Bonnin et al 1990, Rondanelli et al 1993). In our isolate the micronemes are never orderly (Fig.…”

Experimental respiratory cryptosporidiosis in immunosuppressed rats: a light and electron microscopy study

“…Our TEM and LM study documented all C. parvum developmental stages on the surface of the tracheal and bronchial epithelial cells without involvement of lung parenchyma (Meulbroek et al, 1991). These forms were morphologically similar to those described in the intestinal lumen (Vetterling et al, 1971;Pohlenz et al, 1978;Goebel & Braendler 1982;Pearson & Logan, 1983;Lefkowitch et al, 1984;Current & Reese, 1986;Meulbroek et al, 1991). Moreover, the epithelium bea ring the parasitic stages from rats sacrificed at the end of the study protocol did not show progressive histo logic changes, with appearance of an immature malpighian metaplasia, as recently reported by others (Roussel et al, 1995).…”

Electron Microscopic Observation of the Invasion Process of Cryptosporidium Parvum in Severe Combined Immunodeficiency Mice

“…Vacuolation has also been reported ultrastructurally in Cryptosporidium spp. (Vetterling et al, 1971;Current and Reese, 1986;Lumb et al, 1988;Ostrovska and Paperna, 1990). It is known that the vacuolation occurs as a result of secretion from the micronemes, rhoptries, and dense granules.…”