Fig. 1.

Cryptosporidium parvum life cycle. a The excystation of a single oocyst releases four infective sporozoites. Using gliding motility as a means of locomotion, the sporozoites ultimately reach the microvilli of the intestinal epithelial cells. b The parasite remains in the microvillar region inside a parasitophorous vacuole in the plasma membrane of the host. c The sporozoites develop into spherical trophozoites. d Trophozoites undergo merogony, to form Type-I meront, consisting of 8 merozoites. Meront ruptures and infective merozoites are released to infect other nearby cells. e Type-II meront formed from a type-I meront contains four merozoites, but instead of continuing the infection cycle, each merozoite now undergoes gametogony, giving rise to either a (f) microgamont or a (g) macrogamont. h Each micro or macro gamont ultimately gets fertilized to produce a zygote. The zygote, after undergoing sporogony, produces an oocyst containing four sporozoites. It is covered with either a thick or a thin wall. i The thick-walled oocyst is released into the intestinal lumen eventually being excreted out, ready to infect a new host (j) The thin-walled oocyte, on the other hand, can re-infect the same host in a process called autoinfection. (Adapted with modification from CDC, Atlanta, GA, USA. https://www.cdc.gov/dpdx/cryptosporidiosis/index.html). The figure was created with the help of Adobe Illustrator 2020 software