Ultrastructural and molecular characteristics of Setaria species based on sequence analysis of genomic and mitochondrial gene markers in cattle (Bos taurus) and buffaloes (Bubalus bubalis) from Iran

The aim of the present study was to investigate the ultrastructural characteristics and genetic diversity of Setaria parasites from cattle (n=696) and buffalo (n=522) from Khuzestan province of Iran and to compare them with available data from other countries/regions by sequences analysis of the 12S rDNA and the mitochondrial cytochrome C oxidase subunit I (cox1) genes. Based on SEM (Scanning Electron Micrographs) and light microscopy, all the isolated worms were identified as Setaria labiatopapillosa. Our results showed that 12.3% of cattle were infected with Setaria spp., while no infection was found in buffaloes. The maximal prevalence was observed in cattle younger than one year old. The prevalence rate was not influenced by the season of the year or gender. Comparison of the obtained sequences from Setaria with sequences of Setaria spp. from GenBank confirmed that all samples belong to the species S. labiatopapillosa. The phylogenetic tree constructed using cox1 and 12S rDNA genes of several other filarial nematodes showed that the Khuzestan isolates share a common branch with S. labiatopapillosa from other regions. Intra-specific variation was observed in 12S rDNA but not in cox1. In conclusion, our results indicating that S. labiatopapillosa is the main species involved in the spread of setarial infection in south-west of Iran and the identified worms corresponded mostly to worms that reported previously throughout other continents.