Fig. 73.—So-called swarm cysts (endogenous sporulation or schizogony) of the Coccidium of the rabbit. The daughter forms are called merozoites. (After R. Pfeiffer.)
The oöcysts[176] are thick-walled, somewhat flattened at one pole, where a large micropyle is present. Four egg-shaped spores (sporocysts) are formed within, each about 12 µ to 15 µ long and 7 µ broad (fig. 72). The oöcysts are voided with the fæces. Sporogony takes, in nature, about three days in the excrement. Fæcal contamination of the food of rabbits results, and coccidian oöcysts are swallowed. Under the influence of the pancreatic juice of a new host, the sporozoites (fig. 72, a—c) are liberated from the spores and proceed to attack the epithelium and multiply within it, as in the case of Eimeria avium. From the gut, infection spreads to the liver, where multiplication of the parasite goes on actively, resulting in the formation of the whitish coccidial nodules, which may be very conspicuous (fig. 74). Proliferation of the connective tissue may occur around the coccidial nodules, which then contain large numbers of oöcysts in various stages of development. It is said that the oöcysts in the older nodules do not seem to be capable of further development. Schizogony (fig. 73) and gametogony in all stages can be found in both liver and gut.
Young rabbits often die of intestinal coccidiosis before infection of the liver occurs. The repeated schizogony of Eimeria stiedæ in the gut is sufficient to cause death.
Fig. 74.—Eimeria stiedæ. Section through coccidian nodule in infected rabbit’s liver. × 55.
The disease of cattle popularly known as “red dysentery” is also ascribed to the action of Eimeria stiedæ. The fæces of infected cattle show blood clots of various sizes and in severe cases watery diarrhœa is present. Acute cases end fatally in about two days. Numerous oöcysts, considered to be those of Eimeria stiedæ, occur in the fæces, and there is a heavy infection of the gut, especially the large intestine and rectum, all stages of the parasite being found in the epithelium. It is suspected that cattle contract the disease by feeding on fresh grass contaminated with oöcysts. The disease is recorded from Switzerland and from East Africa.