molecular analysis of sarcocystis spp. isolated from sheep (ovis aries) in babol area, mazandaran province, northern iran

background: to differentiate sarcocystis macro-cyst-forming species in slaughtered sheep in babol area, mazandaran province, sequence analysis of 18s rrna gene was performed. methods: overall, 150 slaughtered sheep were examined macroscopically in slaughterhouse, babol and intra-abdominal and diaphragm muscles tissues infected with macro-cyst of sarcocystis spp. were collected in 2013. one macro-cyst was isolated from the infected muscles of each sheep. the partial 18s rrna gene was amplified by pcr and sequenced afterward. results: the rate of infection with macro-cyst producing sarcocystis spp. was 33.3% (50 / 150). the partial 18s rrna gene of sarcocystis species was amplified at the expected pcr product size (~1100 bp) from all 50 macroscopic cysts samples. from 30 sequences dna samples, 20 samples (66.7%), six (20%) and four (13.3%) isolates were identified as s. gigantea , s. moulei and sarcocystis spp., respectively. eight and thirty-four variations in nucleotide position were seen in partial sequence of the18s rrna gene of s. gigantea and s. moulei . conclusion: sheep can be considered as an alternative intermediate host for s. moulei . furthermore, multiple alignments showed some variations in the consensus sequences of the isolates obtained in the current study compared with previously published isolates. to understand better the genetic diversity among sarcocystis species complete sequences of the18s rrna gene or sequence analysis of other genetic loci would be beneficial.