. Biology of the laboratory mouse. Mice as laboratory animals; Mice; Animals, Laboratory; Mice. 354 BIOLOGY OF THE LABORATORY MOUSE. COCCIDIA Eimeria falciformis (eimer).—Mice are commonly infected with E. falciformis (Fig. 137). Although it has been listed as a coccidium of the rat (22), several workers (43) have shown that it cannot be trans- mitted to the rat nor can mice be infected with the rat coccidium, E. miyairii. Development involves the schizogony and the sporogony cycles. Infec- tion occurs by the ingestion of the mature oocysts, each of which gives rise to eight sporozoites which
. Biology of the laboratory mouse. Mice as laboratory animals; Mice; Animals, Laboratory; Mice. 354 BIOLOGY OF THE LABORATORY MOUSE. COCCIDIA Eimeria falciformis (eimer).—Mice are commonly infected with E. falciformis (Fig. 137). Although it has been listed as a coccidium of the rat (22), several workers (43) have shown that it cannot be trans- mitted to the rat nor can mice be infected with the rat coccidium, E. miyairii. Development involves the schizogony and the sporogony cycles. Infec- tion occurs by the ingestion of the mature oocysts, each of which gives rise to eight sporozoites which enter the epithelial cells of the digestive tract and there undergo schizogony. This occurs chiefly in the small intestine but may also occur in the large intestine (43) or in the stomach (31). The merozoites liberated from the schizonts may repeat the asexual cycle, or they may develop into microgametes and macrogametes. Fertilization results in the formation of a zygote which later develops into the oocyst. These occur in the feces and can readily serve for diagnosis. They are subspherical and measure i6^ito2ijubyii /i to 17 At. It is known that laboratory mice often may carry a mild infection of E. falciformis. Yet, Nieschulz and Bos (27) in studying the course of infection found that mice free themselves of an infection with E. falciformis within 26 days when prevented from acquiring reinfection. They suggest that the chronic condition of spontaneous infection is probably due to reinfection. E. falciformis is pathogenic, although in mild infections the hosts are not injured very severely. Of 50 mice which Nieschulz and Bos experi- mentally infected with the coccidium, 40 per cent died between the fourth and eighth day after the infection. They reported that the death was due chiefly to the breaking down of the intestinal epithelium by the schiozogony forms. Wenyon (43) states that in acute infections the organisms may cause acute enteritis. Cryptosporidium muris tyzzer, 1
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