Imported Haycocknema perplexum Infection, United States1.

We report an imported case of myositis caused by a rare parasite, Haycocknema perplexum, in Australia in a 37-year-old man who had progressive facial, axial, and limb weakness, dysphagia, dysphonia, increased levels of creatine kinase and hepatic aminotransferases, and peripheral eosinophilia for 8 years. He was given extended, high-dose albendazole.

Muscular Sarcocystosis in Sheep Associated With Lymphoplasmacytic Myositis and Expression of Major Histocompatibility Complex Class I and II.

Sarcocystosis is a protozoal disease affecting a wide range of animals. The aims of this study were to characterize the following in sheep: (1) the muscle pathology in Sarcocystis infection, (2) the inflammatory infiltrate and its relationship to severity of infection, and (3) immune markers expressed by parasitized muscle fibers and parasitic cysts. Skeletal muscle samples from 78 sheep slaughtered in southern Italy were snap frozen and analyzed by histopathology, immunohistochemistry, and immunofluorescence. Polymerase chain reaction (PCR) and sequencing were used for Sarcocystis species identification. All 40 muscle samples tested were PCR-positive for Sarcocystis tenella. Histologically, cysts were identified in 76/78 cases (97%), associated with an endomysial infiltrate of lymphocytes and plasma cells. The T cells were predominantly CD8+, with fewer CD4+ or CD79α+ cells. Eosinophils were absent. Notably, sarcolemmal immunopositivity for major histocompatibility complex (MHC) I and II was found in 76/78 cases (97%) and 75/78 cases (96%), respectively, both in samples with and in those without evident inflammatory infiltrate. The number of cysts was positively correlated with inflammation. In addition, MHC I was detected in 55/78 cyst walls (72%), and occasionally co-localized with the membrane-associated protein dystrophin. The findings suggest that muscle fibers respond to the presence of cysts by expression of MHC I and II. The possible role of MHC I and II in the inflammatory response and on the cyst wall is also discussed.

Low-Level Parasite Persistence Drives Vasculitis and Myositis in Skeletal Muscle of Mice Chronically Infected with Trypanosoma cruzi.

In chronic Trypanosoma cruzi infection, the cause of Chagas disease, life-threatening inflammatory diseases develop over time in the heart, esophagus, and colon of some patients. C57BL/6 mice infected with the myotropic Colombiana strain of T. cruzi model many of the immunological and parasitological features of human infection but succumb to chronic paralyzing myositis and skeletal muscle vasculitis, not cardiomyopathy or gastrointestinal disease. Here we show that T cell depletion in the chronic phase of this model increased tissue parasitism to acute-phase levels and induced neutrophilic skeletal muscle inflammation. Conversely, after daily treatment with the trypanocide benznidazole for 8 weeks during the chronic phase, viable parasites were no longer detectable, myositis completely resolved, vasculitis was ∼80% reduced, fibrosis was reduced, and myofiber morphology normalized. After the drug was discontinued, parasitism rebounded, and immunopathology recurred. The parasite load was statistically strongly correlated with the severity of inflammation. Thus, both T cell immunity and trypanocidal pharmacotherapy suppress to very low levels, but do not cure, T. cruzi infection, which is necessary and possibly sufficient to induce crippling chronic skeletal muscle myositis and vasculitis in the model.

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.

Using PCR-Based Sequencing to Diagnose Haycocknema perplexum Infection in Human Myositis Case, Australia.

We report a case of myositis in a male patient in Australia who had progressive weakness and wasting in his left lower limb. Although clinical, pathologic, and laboratory assessments were inconclusive, a new, nested PCR-coupled sequencing method enabled the unequivocal diagnosis of myositis caused by the enigmatic nematode Haycocknema perplexum.

High prevalence of chigger mite infection in a forest-specialist frog with evidence of parasite-related granulomatous myositis.

Amphibians are hosts for a wide variety of micro- and macro-parasites. Chigger mites from the Hannemania genus are known to infect a wide variety of amphibian species across the Americas. In Chile, three species (H. pattoni, H. gonzaleacunae and H. ortizi) have been described infecting native anurans; however, neither impacts nor the microscopic lesions associated with these parasites have been described. Here, we document 70% prevalence of chigger mite infection in Eupsophus roseus and absence of infection in Rhinoderma darwinii in the Nahuelbuta Range, Chile. Additionally, we describe the macroscopic and microscopic lesions produced by H. ortizi in one of these species, documenting previously undescribed lesions (granulomatous myositis) within the host's musculature. These findings highlight that further research to better understand the impacts of chigger mite infection on amphibians is urgently required in Chile and elsewhere.

Haycocknema perplexum: an emerging cause of parasitic myositis in Australia.

Haycocknema perplexum is a rare cause of parasitic myositis, with all cases of human infection reported from Australia. This case involved an 80-year-old Queensland wildlife carer, who presented with muscle weakness, mild eosinophilia and creatine kinase elevation. This case supports an association with native animal contact and highlights the debilitating nature of this infection.

Sarcocystis caninum and Sarcocystis svanai n. spp. (Apicomplexa: Sarcocystidae) Associated with Severe Myositis and Hepatitis in the Domestic Dog (Canis familiaris).

There are several reports of Sarcocystis sarcocysts in muscles of dogs, but these species have not been named. Additionally, there are two reports of Sarcocystis neurona in dogs. Here, we propose two new names, Sarcocystis caninum, and Sarcocystis svanai for sarcocysts associated with clinical muscular sarcocystosis in four domestic dogs (Canis familiaris), one each from Montana and Colorado in the USA, and two from British Columbia, Canada. Only the sarcocyst stage was identified. Most of the sarcocysts identified were S. caninum. Sarcocysts were studied using light microscopy, transmission electron microscopy (TEM), and polymerase chain reaction. Based on collective results two new species, S. caninum and S. svanai were designated. Sarcocystis caninum and S. svanai were structurally distinct. Sarcocystis caninum sarcocysts were up to 1.2 mm long and up to 75 µm wide. By light microscopy, the sarcocyst wall was relatively thin and smooth. By TEM, the sarcocyst wall was "type 9", 1-2 µm thick, and contained villar protrusions that lacked microtubules. Bradyzoites in sections were 7-9 µm long. Sarcocysts of S. svanai were few and were identified by TEM. Sarcocystis svanai sarcocysts were "type 1", thin walled (< 0.5 µm), and the wall lacked villar protrusions but had tiny blebs that did not invaginate. DNA was extracted either from infected frozen muscle biopsies or formalin-fixed paraffin-embedded sections. Dogs were either singly infected with S. caninum or multiply co-infected with S. caninum and S. svanai (the result of a mixed infection) based on multilocus DNA sequencing and morphology. BLASTn analysis established that the sarcocysts identified in these dogs were similar to, but not identical to Sarcocystis canis or Sarcocystis arctosi, parasites found to infect polar bears (Ursus maritimus) or brown bears (Ursus arctosi), respectively. However, the S. caninum sequence showed 100% identify over the 18S rRNA region sequenced to that of S. arctica, a parasite known to infect Arctic foxes (Vulpes lagopus).

Oncological approach with antihelminthic chemotherapy and wide resection in the treatment of musculoskeletal hydatidosis. A review of 10 cases with mean follow-up of 64 months.

The objective of this retrospective study was to evaluate clinical outcomes, local recurrence and complication rates of antihelminthic chemotherapy and wide resection in patients with muscle or bone hydatidosis. The authors treated 10 patients (6 females, 4 males) between 2004 and 2012: 8 with muscle and 2 with bone hydatidosis. The mean age at surgery was 42.5 years (range, 11-66 years). All patients were treated with wide resection and pre- and postoperative chemotherapy with albendazole. The mean follow-up was 64 months (range, 28-120 months). All patients achieved satisfactory clinical outcomes. There were no local recurrences. Surgical complications were seen in 3 patients (30%) : one superficial infection, one deep infection, and one hematoma. Two (20%) required additional surgery. An aggressive oncological approach, consisting of antihelminthic chemotherapy and wide resection, can provide favorable clinical outcomes and prevent local recurrence in patients with musculoskeletal hydatidosis. Potential complications of aggressive surgery should be preferred to potential morbidity of local and systemic dissemination.

MANAGEMENT OF ACUTE RENAL FAILURE WITH DELAYED HYPERCALCEMIA SECONDARY TO SARCOCYSTIS NEURONA-INDUCED MYOSITIS AND RHABDOMYOLYSIS IN A CALIFORNIA SEA LION (ZALOPHUS CALIFORNIANUS).

A 3-yr-old captive-born California sea lion (Zalophus californianus) developed Sarcocystis neurona-induced myositis and rhabdomyolysis that led to acute renal failure. The sea lion was successfully managed with fluid therapy, antiprotozoals, antibiotics, anti-inflammatories, antiemetics, gastroprotectants, and diuretics, but developed severe delayed hypercalcemia, a syndrome identified in humans after traumatic or exertion-induced rhabdomyolysis. Treatment with calcitonin was added to the management, and the individual recovered fully. The case emphasizes that animals with rhabdomyolysis-induced renal failure risk developing delayed hypercalcemia, which may be life threatening, and calcium levels should be closely monitored past the resolution of renal failure.

Integral approach to evaluation of the pathogenic activity of Trypanosoma cruzi clones as exemplified by the Mexican strain.

Comparative histopathological study and analysis of parasite load in different muscle groups were carried out in BALB/c mice during the acute phase of Chagas disease. Activities of C104 clone of T. cruzi strain TPAP/MX/2002/Albarrada and the parental strain were compared. Panoramic 2D-microscopy imaging of sample surface was used and quantitative analysis of parasitism and pathologic damage was performed. The infection rates in various muscle groups were as follows: myocardium=abdominal muscles=lumbar muscles=femoral muscles<--diaphragm for the clone and myocardium¬abdominal muscles=lumbar muscles=femoral muscles-->diaphragm for the parental strain.

Decay-accelerating factor 1 deficiency exacerbates Trypanosoma cruzi-induced murine chronic myositis.

INTRODUCTION: Murine infection with Trypanosoma cruzi (Tc) has been used to study the role of T-cells in the pathogenesis of human inflammatory idiopathic myositis. Absence of decay-accelerating factor 1 (Daf1) has been shown to enhance murine T-cell responses and autoimmunity. METHODS: To determine whether Daf1 deficiency can exacerbate Tc-induced myositis, C57BL/6 DAF(+/+) and DAF(-/-) mice were inoculated with 5 × 10(4) trypomastigotes, and their morbidity, parasitemia, parasite burden, histopathology, and T-cell expansion were studied in the acute and chronic stages. RESULTS: DAF(-/-) mice had lower parasitemia and parasite burden but higher morbidity, muscle histopathology, and increased number of CD44(+) (activated/memory phenotype) splenic CD4(+) and CD8(+) T-cells. CONCLUSIONS: An enhanced CD8(+) T-cell immune-specific response may explain the lower parasitemia and parasite burden levels and the increase in histopathological lesions. We propose that Tc-inoculated DAF(-/-) mice are a useful model to study T-cell mediated immunity in skeletal muscle tissues.

Granulomatous myositis associated with a novel alveolate pathogen in an adult southern leopard frog (Lithobates sphenocephalus).

Since 1999, infections with an incompletely characterized alveolate protozoan variously reported as a Dermocystidium-like organism, a Perkinsus-like agent, and Dermomycoides sp. have been associated with mortality events in tadpoles of ranid frogs from the USA. However, disease or mortality events due to this organism have not been described in post-metamorphic animals. We describe infection with a morphologically similar protozoan presenting itself as a leg mass in a free-ranging adult southern leopard frog Lithobates sphenocephalus. Using histological examination, we found a mass within skeletal muscle; this mass was composed of macrophages with intracytoplasmic, thick-walled, 4 to 6 µm in diameter, spherical basophilic protozoal organisms that exhibited green autofluorescence with epiflorescence illumination. Using transmission electron microscopy, organism cell walls were found to have electron-dense plates that, when viewed by scanning electron microscopy, were reminiscent of the thecal plates of dinoflagellates. Additional morphologic and molecular phylogenetic research is needed to resolve the taxonomic status of this organism.

Parasitic infections and myositis.

Infectious myositis may be caused by a wide variety of bacterial, fungal, viral, and parasitic agents. Parasitic myositis is most commonly a result of trichinosis, cystericercosis, or toxoplasmosis, but other parasites may be involved. A parasitic cause of myositis is suggested by history of residence or travel to endemic area and presence of eosinophilia. The diagnosis of parasitic myositis is suggested by the clinical picture and radiologic imaging, and the etiologic agent is confirmed by parasitologic, serologic, and molecular methods, together with histopathologic examination of tissue biopsies. Therapy is based on the clinical presentation and the underlying pathogen. Drug resistance should be put into consideration in different geographic areas, and it can be avoided through the proper use of anti-parasitic drugs.

Eosinophil deficiency compromises parasite survival in chronic nematode infection.

Immune responses elicited by parasitic worms share many features with those of chronic allergy. Eosinophils contribute to the inflammation that occurs in both types of disease, and helminths can be damaged or killed by toxic products released by eosinophils in vitro. Such observations inform the widely held view that eosinophils protect the host against parasitic worms. The mouse is a natural host for Trichinella spiralis, a worm that establishes chronic infection in skeletal muscle. We tested the influence of eosinophils on T. spiralis infection in two mouse strains in which the eosinophil lineage is ablated. Eosinophils were prominent in infiltrates surrounding infected muscle cells of wild-type mice; however, in the absence of eosinophils T. spiralis muscle larvae died in large numbers. Parasite death correlated with enhanced IFN-gamma and decreased IL-4 production. Larval survival improved when mice were treated with inhibitors of inducible NO synthase, implicating the NO pathway in parasite clearance. Thus, the long-standing paradigm of eosinophil toxicity in nematode infection requires reevaluation, as our results suggest that eosinophils may influence the immune response in a manner that would sustain chronic infection and insure worm survival in the host population. Such a mechanism may be deployed by other parasitic worms that depend upon chronic infection for survival.

Syrian hamster infected with Leishmania infantum: a new experimental model for inflammatory myopathies.

Idiopathic inflammatory myopathies (IIMs) are inflammatory disorders of unknown origin. On the basis of clinical, histopathological, and immunological features, they can be differentiated into three major and distinct subsets: dermatomyositis; polymyositis; and inclusion-body myositis. Although a few animal models for IIM are currently available, they lack several characteristic aspects of IIMs. The aim of our study was to examine skeletal muscle involvement in an experimental animal model of visceral leishmaniasis, a disseminated infection caused by the protozoan parasite Leishmania infantum, and to compare features of associated inflammation with those of human IIM. Syrian hamsters infected intraperitoneally with amastigotes of L. infantum were killed at 3 or 4 months post-infection, and the skeletal muscles were studied. Focal inflammation was predominantly observed in the endomysium and, to a lesser extent, in perivascular areas. Degenerating muscle fibers were also found, as well as myonecrosis. Immunofluorescence with confocal laser scanning microscopy was used to characterize the phenotype of inflammatory infiltrates and the distribution of MHC class I and II in muscle biopsies. The infiltrating inflammatory cells consisted mainly of T cells, and CD8(+) T cells were found in non-necrotic muscle fibers that expressed MHC class I on the sarcolemma. In addition to T cells, several macrophages were present. The model we are proposing closely resembles polymyositis and may be useful in studying certain aspects of this disease such as the role of T cells in muscle inflammation and myocytotoxicity, while also providing novel therapeutic targets.

Leishsmania (Leishmania) amazonensis infection: Muscular involvement in BALB/c and C3H.HeN mice.

Recent studies have provided some insights into Leishsmania (Leishmania) amazonensis muscular infection in dogs, although, muscular disease due to leishmaniasis has been poorly documented. The aim of our study was to evaluate involvement of Leishmania in muscular infection of two distinct mouse strains (BALB/c and C3H.He), with different genetic backgrounds. BALB/c mice, susceptible to Leishmania infection, showed, at the beginning of infection, a great number of infected macrophages among muscle fibers; however, in C3H.He resistant mice, muscle fibers were less damaged than in BALB/c mice, but some parasitized macrophages could be seen among them. A follow up of the infection showed an intense inflammatory infiltrate mainly composed of infected macrophages in BALB/c muscles and the presence of amastigotes within muscle fibers; while C3H.He mice exhibited a moderate inflammatory infiltrate among skeletal muscle fibers and an absence of amastigotes. Total destruction of muscles was observed in BALB/c mice in the late phase of infection (day 90) while C3H.He mice showed a process of muscle repair. We concluded that: (1) the muscles of BALB/c mice were more affected by leishmaniasis than those of C3/H.He mice; (2) Leishmania amastigotes are capable of infecting muscular fibers, as observed in BALB/c mice; (3) as inflammatory infiltrate is less intense in C3H.He mice these animals are capable of restoring muscular fibers.

Chronic myositis in an Australian alpaca (Llama pacos) associated with Sarcocystis spp.

An alpaca (Llama pacos), born and raised in Australia, was presented with multiple subcutaneous abscesses. Histological findings indicated a severe necrotizing and histiocytic myositis and cellulitis associated with central caseation and multiple sarcocysts. Ultrastructural examination supported the diagnosis; however, cyst wall characteristics were not consistent with the 2 known species found in alpacas. While seroconversion in camelids is reported to be near ubiquitous, myositis is rare, and this is the first case reported outside of the Americas.

Bacterial, fungal, parasitic, and viral myositis.

Infectious myositis may be caused by a broad range of bacterial, fungal, parasitic, and viral agents. Infectious myositis is overall uncommon given the relative resistance of the musculature to infection. For example, inciting events, including trauma, surgery, or the presence of foreign bodies or devitalized tissue, are often present in cases of bacterial myositis. Bacterial causes are categorized by clinical presentation, anatomic location, and causative organisms into the categories of pyomyositis, psoas abscess, Staphylococcus aureus myositis, group A streptococcal necrotizing myositis, group B streptococcal myositis, clostridial gas gangrene, and nonclostridial myositis. Fungal myositis is rare and usually occurs among immunocompromised hosts. Parasitic myositis is most commonly a result of trichinosis or cystericercosis, but other protozoa or helminths may be involved. A parasitic cause of myositis is suggested by the travel history and presence of eosinophilia. Viruses may cause diffuse muscle involvement with clinical manifestations, such as benign acute myositis (most commonly due to influenza virus), pleurodynia (coxsackievirus B), acute rhabdomyolysis, or an immune-mediated polymyositis. The diagnosis of myositis is suggested by the clinical picture and radiologic imaging, and the etiologic agent is confirmed by microbiologic or serologic testing. Therapy is based on the clinical presentation and the underlying pathogen.

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.