Periparturient transmission of Cryptosporidium xiaoi from ewes to lambs

The mechanism for the maintenance of Cryptosporidium infection in sheep between yearly lambing periods is not clear. Previously, periparturient shedding of oocysts as the result of stress from lambing was suspected to be a mechanism for the initiation of Cryptosporidium infection in lambs, but this has never been verified by genotyping studies. In this study, fecal specimens from four age groups of sheep in Inner Mongolia, China were examined for Cryptosporidium spp. by PCR-restricted fragment length polymorphism and sequence analyses of the small subunit (SSU) rRNA gene, including 59 ewes 1 week before parturition, 154 ewes at parturition, 87 lambs of 3-4 weeks, and 75 lambs of 15-16 weeks. The Cryptosporidium infection rate in ewes at parturition (7.8%) was significantly higher than at 1 week before parturition (1.7%). Higher infection rates were found in lambs (18.4% and 26.7% for 3-4-week-old and 15-16-week-old lambs, respectively). Most (10/13) Cryptosporidium-positive ewes were shedding Cryptosporidium xiaoi, which was also the dominant species (15/16) in neonatal lambs of 3-4 weeks in age (15/16). The less common species in ewes, Cryptosporidium ubiquitum, was not found in lambs of 3-4 weeks but was the dominant species (14/20) in lambs of 15-16 weeks. The major zoonotic Cryptosporidium species, C. parvum (of the IIaA15G2R1 subtype), was only found in one lamb. These data support the occurrence of periparturient transmission of Cryptosporidium spp., especially C. xiaoi, from ewes to lambs.