Coccidia, more commonly known as coccidia, are protozoa that live in the cat's intestine, the most common are Isospora felisand Isospora Rivolta, which form an ocyst. Others are, for exampleCryptosporidium parvum. Isospora is commonly associated with large cat households and poor hygiene. Most of the infections are not treated or even aware of their existence, because they do not necessarily show symptoms in an adult cat and cats eventually overcome the infection on their own. 

 

However, symptomatic cats are treated with an antibiotic meant for pigs (Baycoxine vet) for three days, after which there is a two-week break and the cats are medicated again. The stool is examined two weeks after the last medication to make sure that the medication has worked. 
The cleaning of the environment and litter boxes is also enhanced during medication.