Genetic characterisation of six Sarcocystis species from reindeer ( Rangifer tarandus tarandus) in Norway based on the small subunit rRNA gene

Abstract

Six Sarcocystis species, i.e. Sarcocystis grueneri, Sarcocystis rangi, Sarcocystis tarandivulpes, Sarcocystis hardangeri, Sarcocystis rangiferi and Sarcocystis tarandi have previously been described from reindeer based on sarcocyst morphology. In order to validate and expand the species descriptions , the complete small subunit (ssu) rRNA gene was sequenced and used to genetically characterise the six species. The aim was to reveal possible genetic variation in the ssu rRNA gene within each Sarcocystis species, between the species from reindeer, but also between the reindeer species and related Sarcocystis species characterised in other studies. Muscle tissue from the heart and diaphragm was sampled from 18 adult semi-domesticated reindeer at a field abattoir in northern Norway. Sarcocysts were excised from the tissue and classified into one of the six known Sarcocystis species based on their morphology. Two cysts of each of the six species from two different animals were randomly selected for further DNA analyses. The complete ssu rRNA gene was amplified by the polymerase chain reaction (PCR) and subsequently sequenced. The complete ssu rRNA gene sequences were used to compare the six species with each other and with other previously sequenced Sarcocystis species retrieved from GenBank. There was little sequence variation between two isolates of the same species, but the six species differed from each other by insertions, deletions and single nucleotide polymorphisms (SNPs), mainly located in variable regions of the gene. The identity between the six species from reindeer was approximately the same as when other Sarcocystis species using a different intermediate host were compared with each other. This study supported previous findings of reindeer being the intermediate host for at least six Sarcocystis species and the results also indicated the existence of certain nucleotide positions within the ssu rRNA gene that are unique to Sarcocystis species with a canine definitive host.