Abstract
Three cyst-forming Sarcocystis species have been identified in horsemeat; however, there exists considerable confusion concerning their relationships. Here, 74% (34/46) of the examined tissue samples from horses contained sarcocysts based on examination by light microscopy (LM), and the organism was identified as Sarcocystis bertrami based on cyst structure. The S. bertrami cysts were microscopic (up to 6750 μm in length) and exhibited a striated wall with 2.0–5.1 μm villar protrusions (vps) under LM. Transmission electron microscopy (TEM) observations showed that the vps were tightly packed, similar to “type 11c”. Four genetic markers (18S, 28S, ITS1 and the mitochondrial cox1 gene) of S. bertrami were sequenced and analyzed. The 28S and ITS1 sequences are the first records for Sarcocystis in horses. The newly obtained sequences of the 18S and cox1 genes both shared the highest similarities with those of S. bertrami and S. fayeri obtained from horses. Phylogenetic analysis based on the 18S, 28S and cox1 sequences revealed that S. bertrami and S. fayeri formed an independent clade within a group comprising Sarcocystis spp. from ruminants and pigs. Therefore, S. bertrami and S. fayeri are considered to represent the same species of Sarcocystis in horses, and S. fayeri is a junior synonym of Sarcocystis bertrami.
Highlights
Four Sarcocystis species have been named in horses (Equus caballus) so far: S. bertrami Doflein, 1901 [1]; S. equicanisRommel and Geidel, 1975 [22]; S. fayeri Dubey, Streitel, Stromberg, and Toussant, 1977 [2]; and S. neurona Dubey, Davis, Speer, Bowman, de Lahunta, Granstrom, Topper, Hamir, Cummings, and Suter, 1991 [3]
S. bertrami and S. fayeri are considered to represent the same species of Sarcocystis in horses, and S. fayeri is a junior synonym of Sarcocystis bertrami
The prevalence of sarcocysts in Chinese horses was 73.9% (34/46), and it has been reported to be higher than 68.8% (22/32) in Turkish horses [21], 46.2% (55/119) in Moroccan horses [16], 62.2% (245/349) in British horses [5], and 13.2% (12/91) in Belgian horses [8], but lower than 93.0% (40/43) in Mongolian horses [9]
Summary
Four Sarcocystis species have been named in horses (Equus caballus) so far: S. bertrami Doflein, 1901 [1]; S. equicanisRommel and Geidel, 1975 [22]; S. fayeri Dubey, Streitel, Stromberg, and Toussant, 1977 [2]; and S. neurona Dubey, Davis, Speer, Bowman, de Lahunta, Granstrom, Topper, Hamir, Cummings, and Suter, 1991 [3]. Four Sarcocystis species have been named in horses (Equus caballus) so far: S. bertrami Doflein, 1901 [1]; S. equicanis. Mature sarcocysts of S. bertrami, S. equicanis and S. fayeri have been found in horses, and all of these species have dogs as their definitive hosts. The horse is considered an aberrant host of S. neurona. Ma et al.: Parasite 2020, 27, 1 because only schizonts have been identified in horses with certainty. There is currently considerable confusion concerning the validity of the three abovementioned cyst-forming Sarcocystis species in horses and other equids [4]
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