PCR Slippage Across the ML ‐2 Microsatellite of the C ryptosporidium MIC 1 Locus Enables Development of a PCR Assay Capable of Distinguishing the Zoonotic C ryptosporidium parvum From Other Human Infectious C ryptosporidium Species

Summary C ryptosporidium are ubiquitous and significant enteropathogens of all classes of vertebrates and a major cause of human morbidity and mortality worldwide. Of the 24 recognized species, the zoonotic C ryptosporidium parvum and the host‐specific C ryptosporidium hominis cause the majority of cases of human cryptosporidiosis. Here, we report on structural and transcriptional variability between C .  parvum and C .  hominis at the MIC 1 locus, which encodes a microneme localized thrombospondin‐like domain containing protein previously demonstrated to be critical for host cell infection by C .  parvum . We demonstrate, using reverse transcription quantitative PCR with the aid of genomic data from the E u P ath DB site, that the transcribed product in C .  hominis is both truncated and significantly down‐regulated in the sporozoite. We hypothesize that C p MIC 1 may be a genetic factor involved in facilitating the wider host range of C . parvum in comparison with the specific host range of C . hominis . Furthermore, we show that the presence of a microsatellite ( ML ‐2) within the C .  parvum MIC ‐1 locus enables the development of a PCR marker that can rapidly distinguish the zoonotic C . parvum from C .  hominis and other significant human infectious C ryptosporidium species due to reproducible PCR slippage across the ML ‐2 microsatellite. Additionally, we demonstrate that this locus is tightly linked to the GP 60 locus, a locus commonly used in the genetic characterization of C . parvum and C .  hominis isolates. This marker should provide a robust and additional tool to aid in the rapid identification of C . parvum from other C ryptosporidium species.