PCR-RFLP analysis of the SSU rRNA gene of Cryptosporidium spp. in stool specimens collected from the same household. Lane 1, specimen from the index child on 3 May 2005; lane 2, specimen from the sibling on 10 May 2005; lanes 3 to 5, specimens from the household dog on 12, 17, and 25 May 2005; lane 6, 100-bp molecular size ladder; lane 7, specimen from the index child collected during the third episode of cryptosporidiosis (on 26 September 2005); lane 8, positive control for C. canis; lane 9, positive control for C. parvum; lane 10, positive control for C. hominis. Notice that the upper SspI band in C. canis is smaller than those in C. parvum and C. hominis. The upper area shows SspI RFLP products, whereas the lower area shows VspI RFLP products. The fragment of ∼200 bp in the SspI lanes of C. canis was present in PCR products of C. canis but absent in C. hominis or C. parvum PCR products. It is also not seen in VspI RFLP products.