Ultrastructure of Sarcocystis spp. from donkeys (Equus asinus) in Egypt

Morphological and molecular characterization of a Sarcocystis species infecting donkeys from China

There is considerable confusion concerning the relationships among species of Sarcocystis found in donkeys and horses. Here, we describe a Sarcocystis species in Chinese donkeys (Equus asinus). Sarcocysts were found in 12 of 32 (37.5%) adult donkeys. By light microscopy, they were divided into two types, thin-walled and thick-walled. The thin-walled were macroscopic (up to 320 μm wide) and had short club-like protrusions (up to 2.7 μm long); the thick-walled were microscopic (up to 135 μm wide) and had villar protrusions (up to 5.4 μm long). Ultrastructures of the two types exhibited similar morphological characteristics, including bundled microtubules in the core of the villar protrusions penetrating diagonally into the ground substance, similar to wall type 11c. Three genetic markers, 18S rDNA, 28S rDNA, and mitochondrial cox1, obtained from the two morphotypes were sequenced and analyzed. The sequences of the three loci in the two morphotypes presented high intraspecific similarities of 97.2-99.5%, 97.8-99.6% and 99.0 - 99.9%, respectively. The most similar sequences in GenBank to the newly obtained 18S rDNA, 28S rDNA and cox1 sequences were those of Sarcocystis spp. in horses, with similarities of 90.0 - 97.5%, 94.7 - 95.1%, and 82.6 - 84.5%, respectively. Phylogenetic analysis using the three genetic markers indicated that the Sarcocystis sp. in donkeys formed an individual clade most closely related to a clade encompassing Sarcocystis spp. in horses. Further studies are needed for taxonomic identification of sarcocysts in donkeys because the Sarcocystis species in donkeys and horses are not successfully cross transmissible despite morphological similarities.

Sarcocystis bertrami in skeletal muscles of donkeys (Equus africanus asinus) from Southern Italy

Among the protozoa of the genus Sarcocystis (Apicomplexa; Sarcocystidae), Sarcocystis bertrami (syn. Sarcocystis fayeri) is an obligate intracellular parasite of donkeys and horses with worldwide distribution. Here, we report the detection of S. bertrami in naturally infected donkeys from southern Italy and describe their structure by light microscopy (LM) and transmission electron microscopy (TEM). Protozoal cysts were detected both morphologically and molecularly in skeletal muscles of 28.57% (40/140) donkeys. Mature cysts of S. bertrami were found in skeletal muscle measuring 31-102 μm long and 19-83 μm wide with radially striated thick cyst wall. The high prevalence of infected donkeys suggests that dogs, the definitive hosts of S. bertrami, are contaminating environment with environmentally resistant sporocysts. Considering the increased consumption of raw donkey meat results also suggest a potential risk for human health.

Ultrastructure of Sarcocystis bertrami sarcocysts from a naturally infected donkey (Equus asinus) from Egypt

There is considerable confusion concerning Sarcocystis species in equids. Little is known of Sarcocystis infections in donkeys (Equus asinus). Here we describe the structure of Sarcocystis bertrami-like from the donkey by light microscopy (LM) and transmission electron microscopy (TEM). Nineteen sarcocysts from the tongue of a donkey from Egypt were studied both by LM and TEM. By LM, all sarcocysts had variably shaped and sized projections on the sarcocyst walls, giving it a thin-walled to thick-walled appearance, depending on individual sarcocyst and plane of section. By TEM, sarcocysts walls had villar protrusions (vp) of type 11. The sarcocyst wall had conical to slender vp, up to 6 µm long and 1 µm wide; the vp were folded over the sarcocyst wall. The total thickness of the sarcocyst wall with ground substance layer (gs) was 1–3 µm. The vp had microtubules (mt) that originated deeper in the gs and continued up to the tip. The apical part of the vp had electron dense granules. The mt were configured into 3 types: a tuft of electron dense mt1 extending the entire length of the vp with a tuft of medium electron dense mt2 appearing in parallel, and fine mt3 present only in the villar tips. The gs was mainly smooth with few indistinct granules. All sarcocysts were mature and contained metrocytes and bradyzoites. Bradyzoites were approximately 11–15 × 2–3 µm in size with typical organelles.

Sarcocystis fayeri in skeletal muscle of horses with neuromuscular disease

Recent reports of Sarcocystis fayeri-induced toxicity in people consuming horse meat warrant investigation on the prevalence and molecular characterization of Sarcocystis spp. infection in horses. Sarcocysts in skeletal muscle of horses have been commonly regarded as an incidental finding. In this study, we investigated the prevalence of sarcocysts in skeletal muscle of horses with neuromuscular disease. Our findings indicated that S. fayeri infection was common in young mature horses with neuromuscular disease and could be associated with myopathic and neurogenic processes. The number of infected muscles and number of sarcocysts per muscle were significantly higher in diseased than in control horses. S. fayeri was predominantly found in low oxidative highly glycolytic myofibers. This pathogen had a high glycolytic metabolism. Common clinical signs of disease included muscle atrophy, weakness with or without apparent muscle pain, gait deficits, and dysphagia in horses with involvement of the tongue and esophagus. Horses with myositis were lethargic, apparently painful, stiff, and reluctant to move. Similar to humans, sarcocystosis and cardiomyopathy can occur in horses. This study did not establish causality but supported a possible association (8.9% of cases) with disease. The assumption of Sarcocysts spp. being an incidental finding in every case might be inaccurate.