Sarcocystis miescheriana Infection and its Frequency in Pigs in Japan

Abstract

Slaughtered pigs were examined for Sacrocystis infections and the causative organisms were identified as S. miescheriana in Japan for the first time by the morphological examination of cysts, bradyzoites and sporocysts in addition to the developmental stages in dogs. Of 100 fattened and 200 older culled breeding pigs slaughtered in Saitama Prefecture from March 1983 to March 1984, 17 culled pigs were positive for S. miescheriana, whereas none of the fattened pigs were positive. Sarcocystis cysts measured an average of 393.4×126.5μm and bradyzoites an average of 15.49×3.92μm. The cyst wall was radially striated and measured an average of 4.48μm in thickness. Prepatent period was 9 to 10 days and patent period ranged 50 to 83 days according to the storage term of infected meat in a refrigerator at 5°C. Sarcocysts in musculature survived for 30 days, when refrigerated at 5°C. Sporocysts measured an average of 12.0×9.4μm and have a single large, coarse, granular residuum together with four sporozoites. Young gametocytes were seen on days 1 and 2 after ingestion, macrogametes and zygotes on day 3, and unsporulated oocysts on day 5. Most of oocysts were sporulated on day 7. Most of these developmental stages of the parasite were found in lamina propria of the villi of the small intestine of dogs. The developmental stages were parasitic in about the anterior two thirds of the small intestine although the parasite population in each region fluctuated with the progress of development.