Cryptosporidium is a leading infectious cause of diarrhea around the world associated with waterborne outbreaks, community spread, or zoonotic transmission. The parasite has significant impact on early childhood mortality, and infection is both a consequence and cause of malnutrition and stunting. There is currently no vaccine, and treatment options are very limited. Cryptosporidium is a member of the Apicomplexa, and, as typical for this, protist phylum relies on asexual and sexual reproduction. In contrast to other Apicomplexa, including the malaria parasite Plasmodium, the entire Cryptosporidium life cycle unfolds in a single host in less than three days. English et al. establish a model to image life cycle progression in living cells and observe, track, and compare nuclear division of asexual and sexual stage parasites. The authors propose that the parasite executes an intrinsic program of three generations of asexual replication, followed by a single generation of sexual stages that is independent of environmental stimuli. This defines a Cryptosporidium life cycle matching Tyzzer's original description and inconsistent with the coccidian life cycle now shown in many textbooks. The image shows a fluorescence micrograph of the ilium of an experimentally infected mouse, stained for parasites (red), host actin (green) and DNA (blue).

Image Credit: Muthugapatti Kandasamy, Adam Sateriale, and Boris Striepen