Recognition of Cyclic Transmission of Sarcocystis muris by Cats

Abstract

Sarcocystis muris, obtained from laboratory and house mice, was transmitted experimentally to cats. When cysts in the skeletal muscle of mice were ingested by cats, bradyzoites developed directly into gametes in the intestinal mucosa of the cats. After five to 11 days, infectious sporulated sporocysts (8.5 x 10.3 mum) were shed by cats for up to three months. After ingestion of the sporocysts, S. muris multiplied first in the livers and then in the skeletal muscle of mice. Cysts in skeletal muscle attained a length of 5-6 mm and were visible to the naked eye. With heavy infections the cysts outlined major muscle groups. Lesions in mice were apparently the result of degeneration or rupture of cysts, with myositis and sometimes muscle necrosis, leading to locomotor impairment in heavy infection. S. muris required approximately 76 days of development in mice before becoming infectious for cats. S. muris is perpetuated by an obligatory two-host cycle (mouse-cat). Both cats and mice could be infected repeatedly. Rats, hamsters, and guinea pigs did not become infected.

The coccidian parasites (Protozoa, Apicomplexa) of carnivores

“…Duszynski and Speer (1976) Ruiz and Frenkel (1976) were unable to infect the Norway rat, golden hamster, or guinea pig with 5. muris.…”

“…First-generation meronts and merozoites (tachyzoites) in liver of house mouse. Second-generation meronts (sarcocysts) containing metrocytes and merozoites (bradyzoites) in striated muscles of house mouse but not in myocardium (Ruiz and Frenkel, 1976 Sebek (1975), for instance, found it in 5% of 383 wildM. musculus in Czechoslovakia.…”

“…The oocysts have apparently not been described in detail. Ruiz and Frenkel (1976) found them in infected cats and said that they persisted in the lamina propria for an indefinite number of days. Beginning 5-6 days after inoculation, they contained 2 sporulated sporocysts.…”

“…According to Ruiz and Frenkel (1976), the firstgeneration meronts occur in the liver of house mice 11-17 days after the feeding of sporocysts from the cat. These meronts contain tachyzoites with a central nucleus; they did not give their number, but in a photomicrograph of a liver section they published there was a wheel of 28 tiny tachyzoites with what appeared to be a residuum, so the true number of tachyzoites per meront must have been much greater.…”

The Pathoparasitology of Nonhuman Primates: A Review

“…The reader is referred to the definitive works published recently outlining the intricacies of the life cycle of this unique and interesting parasite [190,302,303,743].…”