Histopathology and molecular identification of Sarcocystis species forming macrocysts in slaughtered sheep and goats of Duhok, Iraq

This study aimed to identify Sarcocystis species isolated from macroscopic sarcocysts of naturally infected sheep and goats using histopathological and molecular studies. A total of 260 macrosarcocyst samples were randomly collected from 1,337 infected sheep and goats slaughtered at different abattoirs in Duhok province, Iraq, from May 2021 to June 2022. The macroscopic cysts, which were found in the esophagus, diaphragm, and abdominal muscles, were classified into fat and thin cysts. Histopathological examination of the observed fat and thin cysts showed a thick eosinophilic wall, several internal septa-forming compartments enclosing numerous bradyzoites, and mild mononuclear inflammatory cells infiltrating around the cysts. The 18 Subunit ribosomal RNA (18S rRNA) and 28 Subunit ribosomal RNA (28S rRNA) genes of Sarcocystis spp. were amplified by polymerase chain reaction (PCR) from 200 macrosarcocysts samples. Molecularly, the DNA sequencing results obtained from fat macrocysts of sheep and goats were found to be identical to Sarcocystis gigantea, and from thin cysts of sheep proved to be similar to Sarcocystis medusiformis, while from thin macrocysts of goats were found to be identical to Sarcocystis moulei. Alignment and phylogenetic analysis observed a very close relationship between identified species of Sarcocystis and other Sarcocystis DNA sequences of sheep and goats across the world. To our knowledge, this is the first histopathological and molecular study for identification of Sarcocystis spp. isolated from different macroscopic forms of sarcocysts of sheep and goats in Iraq.