Cryptosporidium occultus sp. n. (Apicomplexa: Cryptosporidiidae) in rats

•We propose establishing C. parvum VF383/C. suis-like as a new species, C. occultus.•Cryptosporidium occultus appears to be adapted to rats.•Cryptosporidium occultus is not infectious for calves or pigs.•Infection caused by C. occultus is localized in the colon.•Oocysts of C. occultus are distinguishable from those of C. suis. Cryptosporidium parvum VF383 has been reported in humans, domesticated ruminants, and wild rats worldwide and described under several names including Cryptosporidium suis-like, based on its close phylogenetic relationship to C. suis. Unlike C. suis, however, it has never been detected in pigs. In the present work, C. parvum VF383 originating from wild brown rats was not infectious for piglets or calves but was infectious for laboratory brown rats, BALB/c mice, and Mongolian gerbils. The prepatent period was 4–5 days for all rodents. The patent period was longer for rats (>30 days) than other rodents (