ABSTRACT
In this chapter “coccidiosis” means “clinical coccidiosis”. Generally speaking, if an infectious organism is present without causing clinical signs, the infection is said to be “subclinicai”. This implies that the organism’s presence is abnormal. Coccidiosis usually occurs only if an animal is subjected to heavy infection when its resistance is low. Low resistance can be related to age, immune status, nutrition, or stress. Signs of intestinal coccidiosis usually include diarrhea, with or without blood loss. Coccidiosis is a disease of young animals, and it therefore tends to coincide with stress-related diseases. Such diseases are multifactorial, involving whatever opportunist pathogens happen to be around at the time, including viruses, bacteria, and fungi. Adult animals are normally highly resistant to coccidiosis, as a result of active immunity. Some coccidia stimulate the rapid development of solid immunity, while others require repeated infections. All coccidial infections incur damage to epithelia, to which the normal response is hyperplasia.
