LGR5 and cryptosporidiosis: The results indicated that C. parvum infection down-regulated the mRNA expression levels of the lgr5 and ki67 genes in mouse ileum tissues at half of the time points, reflecting that C. parvum infection possibly retarded the proliferation and renewal of intestinal epithelial cells to prolong the survival time of the parasites in intestinal cells, and then aggravated Cryptosporidium infection in intestine, in accordance with previous reports [37,38].