Coccidia are small one celled organisms, that multiply in the abdominal tracts of dogs( and other species);mostly in puppies less than 6 months of age, or adult dogs who's health/immune system, is fragile or run down.
The puppy then will grow a natural immunity to the effects of coccidia; the puppy, when adult may carry the coccidia, will shed the cyst in his feces, but have no ill effects.
Puppies, exposed to these feces, and ingesting them will then take on the coccidia.
Since puppies have first no immunity to coccidia, the organism will invade the little one, and will parasitize the intestines.
The most common sign is diarrhea, either mild, or severe, with blood and mucus, or not; it all depends on the severity of the infection.
In severe cases the puppy will also vomit, loose his appetite, dehydrate, and then may die.
A microscopic fecal exam by a veterinarian will detect the cysts confirming a diagnosis.
Coccidiosis is very contagious, especially among young puppies.
Stress can also play a role in the development of coccidiosis; as for an example : the switch from breeder to new home.
But coccidiosis can be treated effectively. If your puppy has diarrhea, do not delay to go to your vet.
To prevent a coccidiosis infection, or to keep it under control , remove all fecal material, thorough sanitation, clean water and bedding.
Keep insects and rodents away, because they are excellent carriers of coccidia.
Don't worry about yourself: Coccidiosis is "host specific" and therefore, canine/cat species of coccidiosis does not infect humans.