Sarcocystis fayeri-Induced Granulomatous and Eosinophilic Myositis in 2 Related Horses

Sarcocystis in horses from Rio Grande do Sul, Brazil: Molecular identification of Sarcocystis bertrami and Sarcocystis neurona in muscle tissues

Horses are intermediate hosts of Sarcocystis spp. capable of forming cysts in their musculature. This study aimed to detect sarcocysts and investigate the presence of nucleic acids from Sarcocystis spp. in samples of striated muscles from horses in the State of Rio Grande do Sul, Brazil, necropsied at the Veterinary Pathology Laboratory of the Federal University of Santa Maria. A total of 108 samples were collected from 24 horses and examined through direct examination. Microscopic tissue cysts were observed in three samples: tongue (2) and esophagus (1) from two animals. Extractions were performed on the found cysts and tissues, even though sarcocystosis detection was not present. DNA samples were subjected to Nested-PCR using Tg18s primers, and the amplified products were subjected to Restriction Fragment Length Polymorphism (RFLP) using DdeI and HpaII enzymes. DNA belonging to Sarcocystis spp. was amplified in tissues from 91.7% (22/24) of the equines, and 67.6% (73/108) of the samples tested positive in the Nested-PCR reaction. The tissues with the highest detection frequency were: diaphragm 92.3% (12/13), gluteal muscle 77.2% (17/22), and esophagus 66.7% (4/6). In RFLP, Sarcocystis spp. was detected in 21 tissues from 11/22 equines, and cysts, identified through nucleotide sequencing, were determined to be S. bertrami. S. neurona was identified in 11 samples from 7/22 animals, with co-infection detected in 5/22 cases. The high detection rate indicates a concerning circulation of the protozoan, particularly the zoonotic S. bertrami found in all tissues, which are commonly exported for human consumption.

Brazilian Horses from Bahia State Are Highly Infected with Sarcocystis bertrami

The protozoan Sarcocystis bertrami (syn. Sarcocystis fayeri) infects horses and has dogs as definitive hosts. Herein we aimed to detect S. bertrami in Brazilian horses destined for human consumption and to determine the frequency of infection in the examined animals. Muscle fragments from 51 horses were collected in a slaughterhouse in Bahia State during three different seasons of the year. Samples from six tissues from each animal were prepared for macroscopic and microscopic evaluation, using tissue grinding, squash and histology. Sarcocystis sp. was observed in 100% of the examined horses. Selected samples were processed for transmission electron microscopy (TEM). Species identification was confirmed using a PCR targeted to the mitochondrial cytochrome c oxidase subunit 1 gene (cox1). Histological examination revealed sarcocysts with variable sizes and shapes, and dispersed within the muscle fibers. When observed by TEM, the sarcocyst wall was wavy and covered by an electrodense layer. The villar protrusions were digitiform and bent. To our knowledge, this study is the first morphological and molecular confirmation of S. bertrami in horses in Brazil and South America.

Sarcocystis gigantea infection associated with granulomatous eosinophilic myositis in a horse

The only Sarcocystis species currently known to inhabit the fibers of skeletal and cardiac muscles in horses are S. fayeri, S. bertrami, and S. asinus. We describe herein the invasion of myofibers in a horse by S. gigantea, a sheep-specific species with low virulence in the original host. A hunter gelding was referred to a veterinary surgeon in Newmarket (UK). The anamnestic data reported that the horse had an initial history of swelling of the right forelimb with fluid on the front of the carpus and edema spreading up the forearm. Subsequently, 2 firm lumps were found on the left pectoral muscle adjacent to the axilla of the left forelimb. Histologic examination of biopsies from the lumps revealed multifocal granulomatous eosinophilic myositis associated with intact and degenerate encysted parasites, consistent with Sarcocystis spp. Based on amplification and DNA sequencing of the 18S rRNA gene obtained from formalin-fixed, paraffin-embedded tissue blocks, S. gigantea was identified. The presence of sarcocysts in equine skeletal muscles has been considered an incidental finding, and there are only sporadic associated reports of myositis. Our finding suggests that some Sarcocystis spp. have a wider intermediate host range than believed previously, and that Sarcocystis of other species (not considered horse-associated) can invade the muscle fibers of equids, leading to myositis.

Sarcocystis infection in red deer (Cervus elaphus) with eosinophilic myositis/fasciitis in Switzerland and involvement of red foxes (Vulpes vulpes) and hunting dogs in the transmission

Red deer (Cervus elaphus) carcasses showing grey-greenish discolouration have been increasingly observed in the canton of Grisons, Switzerland. We investigated whether Sarcocystis infections were associated with this pathology, and whether wild and domestic canids were involved in their transmission. Meat from affected red deer (n = 26), faeces and intestines from red foxes (Vulpes vulpes) (n = 126), and faeces from hunting dogs (n = 12) from the region, were analysed. Eosinophilic myositis and/or fasciitis were diagnosed in 69% of the deer, and sarcocysts were observed in 89% of the animals. Molecular typing targeting a ~700bp variable region of the 18S rRNA gene revealed Sarcocystis hjorti in 73%, S. venatoria/S. iberica in 54%, S. linearis/S. taeniata in 12%, S. pilosa in 8% and S. ovalis in 4% of the deer samples. No inflammatory changes were observed in red deer carcasses with normal appearance (n = 8); however, sarcocysts were observed in one sample, and S. hjorti, S. venatoria/S. iberica or S. silva DNA was detected in five samples. Sarcocystis oocysts/sporocysts were observed in 11/106 faecal and 6/20 intestinal fox samples, and in 2/12 canine samples. Sarcocystis tenella (n = 8), S. hjorti (n = 2), S. gracilis (n = 2), and S. miescheriana (n = 1) were identified in foxes, and S. gracilis (n = 2), S. capreolicanis (n = 1) and S. linearis/S. taeniata (n = 1) in dogs. This study provides first molecular evidence of S. pilosa and S. silva infection in red deer and S. linearis/S. taeniata in dogs and represents the first record of S. ovalis transmitted by corvids in Central Europe. Although Sarcocystis species infecting red deer are not regarded as zoonotic, the affected carcasses can be declared as unfit for human consumption due to the extensive pathological changes.

Fatal Sarcocystis cruzi-induced eosinophilic myocarditis in a heifer in Uruguay

Sarcocystis spp. are causative agents of bovine eosinophilic myositis and/or myocarditis, which are chronic subclinical myopathies that are occasionally responsible for condemnation at slaughterhouses. Sarcocystis cruzi is a protozoan parasite of worldwide distribution transmitted by canids, most commonly associated with subclinical infection in cattle. Although S. cruzi infections can rarely lead to fatal systemic disease, fatal cardiac cases with confirmation of the etiologic diagnosis have not been reported, to our knowledge. We describe herein an unusual case of S. cruzi-induced fatal bovine eosinophilic myocarditis. A 22-mo-old, Holstein-Hereford heifer, in a group of 110 cattle on pasture, manifested growth retardation and died in February 2017. Autopsy revealed myriad yellow-green 1-3-mm coalescing foci, surrounded by fibrosis, affecting ~75% of the ventricular myocardium. Pulmonary edema, ascites, and hydrothorax were consistent with chronic congestive heart failure. Histology revealed severe eosinophilic, granulomatous, necrotizing myocarditis, with multinucleate giant cells, fibrosis, and mineralization. Numerous thin-walled protozoan cysts resembling Sarcocystis spp. were present in the necrotic foci and within the sarcoplasm of adjacent cardiomyocytes. PCR and sequencing of the 18S rRNA gene revealed 99.9-100% homology with S. cruzi. Sarcocystosis can be a rare cause of fatal myocarditis in cattle.

Polyphasic Rhabdomyositis in California Sea Lions (Zalophus Californianus): Pathology and Potential Causes

A myositis syndrome has been recognized for more than a decade in California sea lions (CSLs; Zalophus californianus) but a detailed description of the lesions and potential causes of this condition is lacking. The tissues of 136 stranded CSLs with rhabdomyositis were examined. Rhabdomyositis was considered incidental in 67% (91/136) of the CSLs, and a factor contributing to the animal stranding (significant rhabdomyositis) in 33% (45/136). Of the 91 cases with incidental rhabdomyositis, lesions consisted of a few small foci of lymphohistiocytic inflammation. Of the 45 cases with significant rhabdomyositis, 28 (62%) also presented with major comorbidities such as leptospirosis (2 animals) and domoic acid toxicosis (6 animals), whereas 17 (38%) had severe polyphasic rhabdomyositis as the only major disease process associated with mortality. In these animals, most striated muscles had multiple white streaks and diffuse atrophy. Microscopically, there was myofiber necrosis surrounded by lymphocytes and histiocytes admixed with areas of myofiber regeneration, and/or moderate to severe rhabdomyocyte atrophy usually adjacent to intact Sarcocystis neurona cysts. At the interface of affected and normal muscle, occasional T lymphocytes infiltrated the sarcoplasm of intact myocytes, and occasional myofibers expressed MHCII proteins in the sarcoplasm. S. neurona antibody titers and cyst burden were higher in animals with significant polymyositis antibody titers of (26125 ± 2164, 4.5 ± 1.2 cysts per section) and active myonecrosis than animals with incidental rhabdomyositis antibody titers of (7612 ± 1042, 1.7 ± 0.82 cysts per section). The presented findings suggest that S. neurona infection and immune-mediated mechanisms could be associated with significant polyphasic rhabdomyositis in CSLs.

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.

Immune-Mediated Muscle Diseases of the Horse

In horses, immune-mediated muscle disorders can arise from an overzealous immune response to concurrent infections or potentially from an inherent immune response to host muscle antigens. Streptococcus equi ss. equi infection or vaccination can result in infarctive purpura hemorrhagica (IPH) in which vascular deposition of IgA-streptococcal M protein complexes produces ischemia and complete focal infarction of skeletal muscle and internal organs. In Quarter Horse–related breeds with immune-mediated myositis, an apparent abnormal immune response to muscle antigens results in upregulation of major histocompatibility complex class (MHC) I and II on muscle cell membranes, lymphocytic infiltration of lumbar and gluteal myofibers, and subsequent gross muscle atrophy. Rarely, an inflammatory event results in myositis with subsequent systemic calcinosis characterized by a pathognomonic hyperphosphatemia and high fatality rate. This review presents an overview of these immune-mediated myopathies and highlights clinical and pathological features as well as the suspected pathophysiology.

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.