Development of Human and Calf Cryptosporidium in Chicken Embryos

Abstract

Cryptosporidium is a newly recognized, zoonotic protozoan that produces short-term, flu-like, gastrointestinal illness in immunocompetent humans and prolonged, severe, diarrhea in immunocompromised individuals. Successful completion of the life cycle, from sporozoite to infective oocyst, of isolates of Cryptosporidium from humans and calves was demonstrated in endoderm cells of the chorioallantoic membrane (CAM) of chicken embryos maintained at 37 C. The human and calf isolates of Cryptosporidium were morphologically and developmentally indistinguishable when grown in chicken embryos. The human isolate also completed its entire life cycle in the CAMs of chicken embryos maintained at 35 C and 41 C. Oocysts recovered from endoderm cells of infected CAMs produced heavy infections in suckling mice. The timing, presence, and morphology of developmental stages in CAM cells during the first eight days after inoculation of sporozoites were similar to those in enterocytes of mice inoculated with oocysts. The method described is safe and convenient for cultivating and studying Cryptosporidium in a bacteria-free environment; the system also lends itself to well-established procedures for evaluating antiprotozoan drugs.

Ultrastructural Details of Cryptosporidium parvum Development in Calf Intestine

“…This isolate can be cultivated in MDCK cells (Rosales et al 1993a) and in mouse peritoneal macrophages (Martinez et al 1992), does not grow as well in chick embryos as does other C. parvum isolates (Current & Long 1983), and the enzymatic studies revealed the absence of detectable hexoquinase (Entrala & Mascaró 1997). To further characterize potential strain differences, it will be necessary to use standard methodologies to compare different isolates of C. parvum, at the ultrastructural as well as the immunological and enzymatic levels.…”

Replication and Distribution of Toxoplasma gondii in the Small Intestine after Oral Infection with Tissue Cysts

“…It is possible that viable parasites released into the intestinal lumen are blocked from infecting new epithelial cells by mucus production or antibody responses; however, this should not be the case, as parasites are capable of infecting host cell monolayers after moving through a mucus-like substance (Matrigel) and parasite-specific IgA responses are observed later during infection (5,44). Indeed, luminal spread is utilized by related protozoan species, including Cryptosporidium parvum and Eimeria species (43,45,46). However, unlike these examples, there is currently no evidence for an alternative stage of T. gondii that may increase the survival of parasites while within the intestinal lumen.…”

Ultrastructure of cryptosporidial life cycle in chicken host cells

“…Current and Long (1983) observed by Nomarski interference contrast microscopy the entire life cycle stages in the chorioallantoic membranes of chicken embryos infected with Cryptosporidium. They noted that sporogony was completed while the parasites were within the endodermal cell.…”

“…The morphological structures of each stage were similar to those reported previously in other animals and humans. Some workers (Current and Long, 1983;Tzipori, 1983) report that cryptosporidia originating from the human and calf are morphologically and developmentally indistinguishable. Each of the life cycle stages developed within a parasitophorous vacuole surrounded by a parasitophorous membrane which appeared to be derived from microvilli of the host cell as observed by several workers (Hampton and Rosario, 1966;Vetterling et al, 1971;Pohlenz et al, 1978a;Iseki, 1979;Bird and Smith, 1980;Goebel and Braendler, 1982;Pearson and Logan, 1983).…”

“…They noted that sporogony was completed while the parasites were within the endodermal cell. According to Current and Long (1983), there are two types of unsporulated oocysts, thin-and thickwalled. In both types sporogony takes place within the host cell, but whilst sporozoites are released from the thin-walled oocyst inside the host (autoinfective) the thick-walled sporulated oocyst is discharged outside the host and is a transmissious stage.…”