Fig (XIV)
14.
OOC HBF 오 sch 10 Small piece of the epithelial lining of the gut of an infected Grouse Chick, showing various stages in the life-history of Eimeria (Coccidium) avium, parasites of different ages being present. par, Parasite. spz, Sporozoite or primary infecting germ. sch, Schizont or dividing form. mz, Merozoite or daughter germ., Female Coccidium. 8, Male parasite. oöc, Mature female, ready for fertilisation, with oöcyst wall formed round it. plies (Figs. 14 sch, mz, 15 E-H) therein, at the expense of the host-cell. The epithelial cells of the lining layer, or mucous membrane as it is called, are thus destroyed (Fig. 14). Coccidian parasites from the duodenum invade the cæca or "blind-guts," [GROUSE and further asexual multiplication (schizogony) (Figs. 14 mz, 15 E-H) of the parasite occurs in the epithelium of the cӕca. The daughter forms are known as merozoites (Figs. 14 mz, 15 G-H). The presence of the parasite in the intestinal walls leads to inflammation of the intestine (enteritis), and that occurring in the cæcum has sometimes been termed perityphlitis.
Sooner or later a limit is reached, on the one hand to the power of the grouse-chick to provide nourishment for the parasites, and on the other hand to the multiplicative capacity of the parasites themselves. The Coccidium then begins to reproduce sexually by processes known as gametogony and sporogony (see Fig. 15). Many small male parasites (Figs. 148, 15 18, JỠ, K♂) are produced, together with larger food-containing female Coccidia (Figs. 14, 15 19, J♀, k♀.) The male and female parasites conjugate (Fig. 15 L) and then encyst (Fig. 15 m), afterwards emerging into the cavity of the gut, and giving rise to the cysts found in the cæcal contents (Fig. 15 M-P), and in the cæcal droppings on the moors (Fig. 15 Q-s).
So far as the grouse-chick is concerned, the formation of Coccidian cysts means either recovery or death. If the infection of the parasites has been a heavy one, and multiplication of the parasite has proceeded apace, then the destruction of the intestinal epithelium has been so great that death of the grouse-chick results. If, on the other hand, the epithelium of the intestinal wall has not been so much destroyed fewer Coccidian parasites having been presentthen the gut-epithelium may slowly regenerate and the young bird gradually recover and improve in condition after the Coccidian oöcysts have been passed out with the cæcal droppings.
It is of great interest and importance to note that bacteria are present in the gut of grouse, particularly in the cӕca. Some of these bacteria are injurious to the birds if they reach the internal organs of the bird's body. The young Coccidian parasites may act as inoculating needles, and introduce the bacterial micro-organisms into the epithelial cells of the gut walls. Further, the lesions, resulting from the destruction of the mucous membrane by the Coccidia, allow of the inlet of bacteria which, by way of the blood or lymph channels, may be spread through the internal organs of the body.
As before mentioned, should the Coccidian cysts not be swallowed by other birds, they may remain dormant for lengthy periods (several months), for the cysts are remarkably well adapted for resisting the GROUSE] vicissitudes of life outside the body of the host. Sometimes grouse partially recover from coccidiosis and become chronics, thus serving as reservoirs of oöcysts and spores, B A T R S C D SPOROGONY E SCHIZOGONY G ま GAMETOGONY- K H ↓ ↓ the Coccidian cysts on the moors, and it has been shown experimentally as well as in nature that these cysts pass undigested through the bodies of the maggots and the flies, both of which may aid in spreading the disease.
Coccidiosis is not confined to grouse among birds. It is also a fatal disease among pheasants, fowls, and pigeons.