Since cats who have been infected shed oocysts only once (repeated shedding has only been seen in a laboratory setting in cats with severely compromised immune systems), sterilized cats in managed colonies that have the parasite are no longer producing the oocysts.
In other cases, a puppy or kitten becomes infected with coccidiosis, produces lots of oocysts of coccidia but never has clinical signs of disease such as diarrhea, loss of appetite, vomiting or failure to thrive.