Morphological and molecular identification of three species of Sarcocystis in reindeer (Rangifer tarandus tarandus) in Iceland

摘要

Six Sarcocystis species have previously been described from reindeer in Norway based on sarcocyst morphology and DNA sequencing. The aim of this study was to determine whether reindeer in Iceland, which descend from reindeer imported from Norway in 1787, also were infected with Sarcocystis, and to identify and genetically characterise any species present. Muscle tissue from the heart, diaphragm and/or oesophagus was collected from 36 reindeer in Iceland. Pieces of all tissue samples were examined histologically. Frozen/thawed samples of cardiac muscle, oesophagus and/or diaphragm from 11 of the 36 reindeer were also examined under a stereoscopic microscope and sarcocysts present were identified to species either in situ or under a light microscope. Two cysts of each species, originating from two different reindeer were randomly selected for DNA analyses. The complete ssu rRNA gene was amplified by the polymerase chain reaction (PCR) and sequenced. In addition, two sarcocysts that could not be classified by microscopic examination were selected for partial ssu rRNA gene sequence analysis. By histology, sarcocysts were found in the diaphragm and/or oesophagus of 8 of 36 (22.2%) animals. By examination of fresh tissue, sarcocysts of Sarcocystis rangi, S. tarandivulpes and S. hardangeri were found in the oesophagus of seven of nine (77.8%) animals, suggesting a high prevalence of Sarcocystis in the Icelandic reindeer population. Cyst morphology and the ssu rRNA gene sequence of each of the three species were identical to isolates of the same species from Norwegian reindeer. DNA sequencing was useful in order to identify cysts with an ambiguous morphology. This is the first record of these Sarcocystis species in reindeer outside Norway.