Histological and Ultrastructural Appearance of Severe Sarcocystis Fayeri Infection in a Malnourished Horse

Abstract

Sarcocysts are highly prevalent in the musculature of horses (Equus caballus) in various regions; however, the systematics of Sarcocystis species in equids is confusing. 3 There are 4 reported species of Sarcocystis in equids: S. asinus, S. bertrami, S. equicanis, and S. fayeri. All utilize canids as definitive hosts; however, transplacental infection can occur. 2,4 The interrelationships and validity of the above species are unclear. Pathogenicity of infection is variable, ranging from mild to severe chronic illness in naturally and experimentally infected horses. 5-7 We describe the histologic and ultrastructural appearance of intense Sarcocystis fayeri infection in a malnourished horse. A 3-4-year-old mare was euthanized for humane reasons, having been in deteriorating condition for 2-3 months. At

Experimental Infection of Ponies With Sarcocystis Fayeri and Differentiation From Sarcocystis Neurona Infections in Horses

“…Cawthorn et al (1990) also found these electron-dense structures in another naturally infected horse from Canada. Specimens in this study were fixed in formalin, whereas Tinling et al (1980) and Cawthorn et al (1990) fixed specimens in glutaraldehyde. Whether these procedures used or the stage of the maturity of sarcocysts examined made the difference is unknown.…”

“…Horses with S. fayeri infections may exhibit no clinical sign, or they may have mild to severe chronic illness with anemia, muscle soreness, and malnourishment (Tinling et al, 1980;Fayer and Dubey, 1982;Cawthorn et al, 1990). In contrast, equine protozoal myeloencephalitis, caused by S. neurona infections, is 1 of the most important and severe neurologic diseases affecting horses (Dubey, Lindsay, Saville et al, 2001).…”

Sarcocystis fayeri in skeletal muscle of horses with neuromuscular disease

“…[19] Further, there have been 3 isolated cases with chronic progressive debilitating disease of undetermined cause described as weight loss, weakness, and lethargy on which S. fayeri was found in skeletal muscle. [15,30,31] Additionally, one of these cases had difficulty eating and swallowing and had ataxia or altered gait. [29] The results of the present study do not support S. fayeri as always being an incidental bystander.…”

“…Sarcocysts have been reported to be highly prevalent in musculature of horses. [8,16,21] Species identified in the muscle of equids include S. asinus, S. bertrami, S. equicanis, and S. fayeri; [8,15,16,27] with only one report of a single filly having S. neurona. [14] These species utilize canids as definitive hosts except for S. neurona which uses the opossum.…”

“…[9][10][11][12][13] Intracellular protozoans include Sarcocystis bertrami, S. equicanis, S. fayeri, S. asinus, S. neurona, and Trypanosoma evansi. [8,[14][15][16] Similar to other species, the presence of sarcocysts in equine skeletal muscle has been considered an incidental finding since muscle pathology has not been observed. [17] However, there have been sporadic reports of myositis in horses associated with Sarcocystis spp.…”