This article is from the Canine Medical Information FAQ, by Cindy Tittle Moore with numerous contributions by others.
(Adapted from email discussion with Ron Mandsager,
Coccidiosis is caused by protazoal parasites of either Eimeria spp. or
Isospora spp. Crowding, poor sanitation, or stress may facilitate its
Symptoms depend on the species of protozoa, the infective dose, and
the amount of damage caused. They can range from mild diarrhea to
severe, bloody diarrhea with subsequent dehydration and anemia.
Following infection, the affected animal may become a carrier.
Coccidiosis is a cause of diarrhea in puppies. It may result in death
Treatment consists of supportive therapy once disease develops. Drug
therapy is ineffective - all of the available agents are
coccidiostatic agents; they can prevent infection, but will not treat
an established infection. Good sanitation is essential in preventing
coccidiosis. Most disinfectants are ineffective against coccidian
oocytes, but boiling water and 2% formaldehyde are effective if they
reach the oocyte. Scrupulous cleanliness is the best preventive,
although it is no guarantee against Coccidiosis.
Because coccidia is an environmental contaminant that produces an
opportunistic infection, stress of any kind, such as vaccination, may
be all that it needs to manifest. Adult dogs are carriers, and the
coccidia oocysts are pretty resilient to most common disinfectants.
Coccidiosis may be a major problem in an unclean environment, but may
crop up a well run operation as well. An adult carrier will serve as a
potential source of infection to puppies. The fact that a kennel has
problems with coccidia is not itself a scathing indictment of the
kennel - it's just a fact of life that has to be dealt with.