Determination of prevalence of Sarcocystis spp. by using gross examination, impression smear and digestion methods in muscles of slaughtered sheep in the old slaughterhouse of Tabriz, North of Iran

Sarcocystosis is a zoonotic infection commonly known in domestic animal and cause abortion, stillbirth and neonatal death in domestic animals. Four species of sarcosystosis regularly affect sheep, namely S. tenella (synonym ovicanis) and S. arieticanis, which have a sheep-dog cycle, and S. gigantea (synonym ovifelis) and S. medusiformis, which have a sheep-cat cycle. S. tenella is quite virulent in lambs and acutely causing encephalomyelitis in mature sheep and chronically debility with enormous numbers of cysts in muscles. S. gigantea cysts are very large and only sarcocystis of sheep that is visible with the naked eye. An economic loss due to total or partial elimination of carcasses in meat inspection is very important in our country. The aim of present study was to determine the prevalence of sarcocystosis in slaughtered sheep in the old slaughterhouse of Tabriz, north of Iran. The striated muscles such as masseters, tongue, esophagus, heart, diaphragm and ocular musculature of 80 sheep sampled for further study. All the muscles were dissected and sectioned 2 to 3 mm slices and observed carefully for probable macroscopic cysts. The sections were then examined by the impression smear (Dob smear) and digestive methods. 26 out of 80 sheep (32.5%) were diagnosed as being infected. Four out of sheep (15.4%) were diagnosed as being infected with macroscopic cysts. The cysts were oval in shape, 1 to 3 mm in length and white in color with thin wall that located under the epimysal layer. Fourteen out of 26 (53.84%) and 19 out of 26 (73%) were diagnosed as positive for Sarcocystis spp. by impression smear method and digestion method respectively. Among the three methods used in the present study (gross examination, impression smear and digestion methods), the digestion method was the useful to diagnose microscopic cysts and had higher sensitivity than the other methods. In this study the infection rate increased with age. In this study ocular muscles sarcocystosis was firstly diagnosed in ruminants in Iran.