Genetic variability within isolates of Sarcocystis species infecting sheep from Egypt

In order to explain the exact role of sarcocystosis, principally Sarcocystis tenella, in losses of the Egyptian sheep industry, a precise confirmation about the existence of different Sarcocystis species infecting that economically important animal is needed. Therefore, this work aimed to molecularly identify, as well as illustrate the genetic variability within isolates of Sarcocystis spp. infecting sheep from Egypt. Tissue specimens were collected from sheep slaughtered at 3 Egyptian provinces; Cairo, Dakahlia and Damietta. DNA was isolated from the harvested bradyzoites after peptic digestion for the positive sarcocysts infected specimens, and then PCR amplification using the 18S rRNA gene was carried out. PCR products were subjected to gel electrophoresis. DNA from 600 bp gel bands was purified and sequenced. The revealed sequences were compared to their similarities on Genbank, and analyzed both clusterally and phylogenetically. Two Sarcocystis spp. were identified, the macroscopic cyst forming S. gigantea and the microscopic cyst forming S. tenella. Nine S. tenella sequences were analyzed, resulting in 3 polymorphic sites as well as 3 different haplotypes. Clustering of the nine obtained S. tenella sequences in addition to another 23 S. tenella sequences on Genbank revealed low nucleotide (0.001780) diversity as well as negative value of the Taijma neutral index which are indicators for population expansion. Alignment and Phylogeny results illustrated very close relationship between S. gigantea and S. moulei, a goat specific species which rarely reported in sheep, and in turn proposed the cross transmission of the later species between sheep and goats.