USDA researchers used on-farm data to determine the prevalence of Cryptosporidium species in calves.

The prevalence of certain cryptosporidium species in calves may be related to age.

According to USDA research, C. parvum — the only crypto species infectious to humans — made up 85 percent of crypto infections in pre-weaned calves, but only 1 percent of infections in post-weaned calves.

Parasites once thought to be C. parvum in post-weaned calves may actually be a different species altogether — one that infects cattle, but not humans.