Feline immunodeficiency virus associated myopathy in the adult cat

Primary pyomyositis and uveitis in a cat

A 6-year-old neutered male Siamese cat was referred for investigation of hindlimb ataxia and blindness of 2 weeks' duration. A swollen right hind limb, with no history of trauma, and no evidence of an external wound, was observed on physical examination. Ophthalmic examination revealed bilateral absence of the menace response and changes consistent with uveitis. Blood tests identified changes consistent with inflammation including serum amyloid A elevation. Infectious disease testing was negative. Degenerate neutrophils and bacterial cocci were detected on fine needle aspiration cytology of the affected limb. Thoracic radiography and abdominal ultrasonography identified no abnormalities. Primary pyomyositis was suspected and clindamycin was prescribed following Penrose drain tube placement. In addition, eye drops containing tobramycin, atropine, and prednisolone were administered. The clinical signs and serum amyloid A level were markedly improved after 5 days of treatment. Based on the medical history and lack of other findings, the uveitis was suspected to be secondary to the pyomyositis. The clinical signs resolved completely, and no recurrence was reported within a 6-month follow-up period. To the best of our knowledge, primary pyomyositis with uveitis has not been previously reported in cats.

Leishmania spp.-Infected Dogs Have Circulating Anti-Skeletal Muscle Autoantibodies Recognizing SERCA1

Leishmania spp. infection is associated with an inflammatory myopathy (IM) in dogs. The pathomechanism underlying this disorder is still elusive, however, the pattern of cellular infiltration and MHC I and II upregulation indicate an immune-mediated myositis. This study aimed to investigate the presence of autoantibodies targeting the skeletal muscle in sera of leishmania-infected dogs and individuate the major autoantigen. We tested sera from 35 leishmania-infected dogs and sera from 10 negative controls for the presence of circulating autoantibodies with indirect immunofluorescence. Immunoblot and mass spectrometry were used to identify the main target autoantigen. Immunocolocalization and immunoblot on immunoprecipitated muscle proteins were performed to confirm the individuated major autoantigen. We identified circulating autoantibodies that recognize skeletal muscle antigen(s) in sera of leishmania-infected dogs. The major antigen was identified as the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 1 (SERCA1). We also found that canine SERCA1 presents several identical traits to the calcium-translocating P-type ATPase of Leishmania infantum. In the present study, we defined circulating anti-SERCA1 autoantibodies as part of the pathogenesis of the leishmania-associated IM in dogs. Based on our data, we hypothesize that antigen mimicry is the mechanism underlying the production of these autoantibodies in leishmania-infected dogs.

The correlation between cardiac and skeletal muscle pathology in animal models of idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) represent a heterogeneous group of disorders in which skeletal muscle is inappropriately targeted by the immune system. IIMs are characterized by inflammation of muscle and varying degrees of muscle dysfunction. Extra-muscular manifestations may involve heart, skin, joints, lungs, and gastrointestinal tract. Cardiovascular involvement is a feared event because is one of the leading causes of mortality in IIM patients. As the myocardium shares many features with the skeletal muscle, it is supposed that it can be affected by the same inflammatory processes, which take place during the different forms of IIMs. However, the full extent of this link and the mechanisms behind it are still not fully understood. Animal models have greatly improved our understanding of IIM pathomechanisms and have proven to be a useful tool for discovering therapeutic drug targets. Here we report the evidence of heart muscle involvement in different animal models of spontaneous IIMs, assuming a common autoimmune mechanism and presenting them as study models for human pathology.

Lameness, generalised myopathy and myalgia in an adult cat with toxoplasmosis

Case summary

A 2-year-old female neutered domestic shorthair cat presented with an 18-month history of intermittent lameness on all four limbs. The cat was markedly lame on all four limbs. There was alternation between toe-walking on the forelimbs with a hunched posture and using the dorsal aspect of the carpi to walk on. The cat would hiss repeatedly when walking and would lie down tentatively, appearing happier and less painful when lying. When not lying, the cat preferred to sit back on the hindlimbs and non-weightbear on the forelimbs (the so-called kangaroo stance). Physical examination detected pain on palpation of the calcaneus bone and Achilles tendon bilaterally, and general resentment to handling. Investigations revealed an elevated creatine kinase, a positive Toxoplasma gondii IgG titre, toxic neutrophilic inflammation within the Achilles tendon bursae, electromyography and nerve conduction velocity studies consistent with a diffuse muscular disease, and histopathology of the muscle consistent with a chronic and diffuse myopathy. Arthrocentesis samples and an antinuclear antibodies titre were normal. Prior treatment with meloxicam had been ineffective. A 6-week course of clindamycin was prescribed; an improvement was seen within 3 days and clinical resolution at 3 months. The cat remained clinically normal after 20 months.

Relevance and novel information

To our knowledge, there have been no previously published reports of histopathologically confirmed myopathy as a result of T gondii in cats. This report suggests toxoplasmosis should be considered as a differential diagnosis in cats with myopathies or lameness in the absence of other causes.

Evaluation of coexisting polymyositis in feline myasthenia gravis: A case series

Acquired myasthenia gravis (MG) is relatively uncommon in cats. In humans, MG may be associated with other immune-mediated disorders, in particular polymyositis (PM). In this study, we described in-depth electrodiagnostic findings and pathological changes in muscles of cats diagnosed with MG, and assessed the presence of concurrent PM. Six cats with confirmed acetylcholine receptor antibody seropositive MG, and two suspected cases with clinical signs and electrophysiological changes consistent with MG, were reviewed. All animals presented with severe typical signs of generalized weakness and/or fatigability, resembling late-onset MG in humans, in addition to regurgitation. Five cats presented a cranial mediastinal mass, with 3 confirmed as thymoma. Repetitive nerve stimulation revealed a decrement of the compound muscle action potential in all tested cases, starting from low frequencies of stimulation. Serum creatine kinase activity was increased in 6/8 cats. Muscle biopsies performed in 5 cats revealed varying degrees of mixed mononuclear cell infiltrates, positive for the leukocyte markers CD3/CD4/CD8 and CD11b. Further MHC-1/C5b-9 positive sarcolemmal deposits were identified in all tested cases, with or without thymoma. This study documents an association of MG and PM in cats, and provides further support for feline MG as a relevant animal model of human MG.

Digital flexor musculotendinous contracture in two Devon Rex cats

Clinical summary: A 13-year-old, spayed Devon Rex with unilateral digital flexor musculotendinous contracture of the forelimb was treated by surgical tenotomy. The condition improved transiently, but recurred rapidly and became bilateral. Histopathologic analysis of necropsy tissues resulted in a morphologic diagnosis of fibromyositis of the antebrachial muscles causing contracture and flexural deformity of the carpi and phalanges of both thoracic limbs. A search for similar cases yielded the clinical notes of a second cat, a 10-year-old, spayed Devon Rex, also with bilateral disease. This second case responded well to surgical tenotomy but tissue biopsies were not obtained to permit microscopic assessment of the underlying pathologic process. Relevance and novel information: Acquired and permanent contracture of the digital flexor muscles and/or tendons of the forelimbs is a rare and poorly described condition of cats. The very limited number of documented cases describing disease affecting one or more digits (but not the carpus) infers a causal link with onychectomy, but reported histopathologic changes have been limited to the tendons. The two cases described in this report suffered contracture of the carpus and all digits bilaterally, one without previous onychectomy and the other 9 years after onychectomy. There were novel histopathologic findings in the muscles of the one case for which biopsy material was available. Information gained from these two cases provides a new perspective for the investigation and treatment of future cases. Specifically, consideration should be given to an underlying immune-mediated myopathic process and a possible genetic predisposition in the Devon Rex breed. Currently, the poorly understood etiopathogenesis hinders our ability to definitively recommend treatment options, which might include corticosteroids and other forms of immunosuppressive therapy.

Myocarditis caused by Feline Immunodeficiency Virus in Five Cats with Hypertrophic Cardiomyopathy

Viral infections have been implicated as the cause of cardiomyopathy in several mammalian species. This study describes hypertrophic cardiomyopathy (HCM) and myocarditis associated with feline immunodeficiency virus (FIV) infection in five cats aged between 1 and 4 years. Clinical manifestations included dyspnoea in four animals, one of which also exhibited restlessness. One animal showed only lethargy, anorexia and vomiting. Necropsy examination revealed marked cardiomegaly, marked left ventricular hypertrophy and pallor of the myocardium and epicardium in all animals. Microscopical and immunohistochemical examination showed multifocal infiltration of the myocardium with T lymphocytes and fewer macrophages, neutrophils and plasma cells. An intense immunoreaction for FIV antigen in the cytoplasm and nucleus of lymphocytes and the cytoplasm of some macrophages was observed via immunohistochemistry (IHC). IHC did not reveal the presence of antigen from feline calicivirus, coronavirus, feline leukaemia virus, feline parvovirus, Chlamydia spp. or Toxoplasma gondii. The results demonstrate the occurrence of FIV infection in inflammatory cells in the myocardium of five cats with myocarditis and HCM.

Identification of Bartonella henselae in 2 cats with pyogranulomatous myocarditis and diaphragmatic myositis

Most cats infected with Bartonella henselae remain outwardly healthy carriers for years; however, self-limiting fever, transient anemia, neurologic dysfunction, lymphadenopathy, reproductive disorders, aortic valvular endocarditis, and neutrophilic myocarditis have been described in experimentally or naturally infected cats. Two cats in a North Carolina shelter died with pyogranulomatous myocarditis and diaphragmatic myositis. Bacteria were visualized in the lesions by Warthin-Starry silver impregnation and by B. henselae immunohistochemistry. B. henselae DNA was amplified and sequenced from the heart of 1 cat and from multiple tissue samples, including heart and diaphragm, from the second cat. This study supports a potential association between B. henselae and what has been historically described as "transmissible myocarditis and diaphragmitis" of undetermined cause in cats.

Pathological manifestations of feline immunodeficiency virus (FIV) infection in wild African lions

Feline immunodeficiency virus (FIV) causes AIDS in the domestic cat (Felis catus) but has not been explicitly associated with AIDS pathology in any of the eight free-ranging species of Felidae that are endemic with circulating FIV strains. African lion (Panthera leo) populations are infected with lion-specific FIV strains (FIVple), yet there remains uncertainty about the degree to which FIV infection impacts their health. Reported CD4+ T-lymphocyte depletion in FIVple-infected lions and anecdotal reports of lion morbidity associated with FIV seroprevalence emphasize the concern as to whether FIVple is innocuous or pathogenic. Here we monitored clinical, biochemical, histological and serological parameters among FIVple-positive (N=47) as compared to FIVple-negative (N=17) lions anesthetized and sampled on multiple occasions between 1999 and 2006 in Botswana. Relative to uninfected lions, FIVple-infected lions displayed a significant elevation in the prevalence of AIDS-defining conditions: lymphadenopathy, gingivitis, tongue papillomas, dehydration, and poor coat condition, as well as displaying abnormal red blood cell parameters, depressed serum albumin, and elevated liver enzymes and gamma globulin. Spleen and lymph node biopsies from free-ranging FIVple-infected lions (N=9) revealed evidence of lymphoid depletion, the hallmark pathology documented in immunodeficiency virus infections of humans (HIV-1), macaques, and domestic cats. We conclude that over time FIVple infections in free-ranging lions can lead to adverse clinical, immunological, and pathological outcomes in some individuals that parallel sequelae caused by lentivirus infection in humans (HIV), Asian macaques (SIV) and domestic cats (FIVfca).

Animal models of retroviral encephalopathies: feline model

Human immunodeficiency virus infection in children and adults results in a progressive neurodegenerative disease consistent with a predominant subcortical mediated dementia. Techniques for developing a feline model of the early stages of lentiviral-associated neurodegeneration are presented. The behavioral, neurophysiologic, immunologic, virologic, and neuropathologic aspects of this model are also described.

Feline immunodeficiency virus infection: a valuable model to study HIV-1 associated encephalitis

Feline immunodeficiency virus (FIV), like human immunodeficiency virus (HIV)-1, is a neurotropic lentivirus and is associated with neuropathology in natural and experimental infections. FIV enters the brain early following experimental infection, and virus has been proposed to enter the brain via the blood-brain barrier and blood-CSF barrier, within infected lymphocytes and monocytes/macrophages. However the entry of cell-free virus or the direct infection of brain endothelial cells and astrocytes of the blood-brain barrier may also contribute to CNS infection. This review explores the role played by the FIV model in the elucidation of mechanism of lentiviral entry to the brain and viral interactions with the CNS, particularly in relation to lymphotropic lentiviruses.

From dog to man: the broad spectrum of inflammatory myopathies

The purpose of this review is to describe the various forms of inflammatory myopathy that occur spontaneously in dogs, and discuss the similarities and differences between inflammatory myopathy in dogs and humans. Some interesting muscle-specific autoantigens have recently been discovered in canine autoimmune myositis, and they are associated with specific forms of inflammatory myopathy. These autoantigens may now be investigated in humans. Furthermore, the association of distinct inflammatory myopathies with certain breeds of dogs point to important genetic components of inflammatory myopathy that can now be studied using dogs as both parallel disorders and animal models. Other canine myositides, associated with infectious and histiocytic diseases, may also be relevant to similar human disorders.

Complications musculaires de l’infection par le virus de l’immunodéficience humaine (VIH) à l’ère des trithérapies

Introduction of highly active antiretroviral therapy (HAART) has dramatically modified the natural history of HIV disease, but lengthening the survival of HIV-infected individuals has been associated with an increasing prevalence of iatrogenic conditions. Muscular complications of HIV infection are classified as follows: (1) HIV-associated myopathies and related conditions including polymyositis, inclusion-body myositis, nemaline myopathy, diffuse infiltrative lymphocytosis syndrome (DILS), HIV-wasting syndrome, vasculitis, myasthenic syndromes, and chronic fatigue; (2) iatrogenic conditions including mitochondrial myopathies, HIV-associated lipodystrophy syndrome, and immune restoration syndrome; (3) opportunistic infections and tumor infiltrations of skeletal muscle; and (4) rhabdomyolysis. These features are described in the present review.

Skeletal muscle involvement in human immunodeficiency virus (HIV)-infected patients in the era of highly active antiretroviral therapy (HAART)

Skeletal muscle involvement can occur at all stages of human immunodeficiency virus (HIV) infection, and may represent the first manifestation of the disease. Myopathies in HIV-infected patients are classified as follows: (1) HIV-associated myopathies and related conditions, including HIV polymyositis, inclusion-body myositis, nemaline myopathy, diffuse infiltrative lymphocytosis syndrome (DILS), HIV-wasting syndrome, vasculitic processes, myasthenic syndromes, and chronic fatigue; (2) muscle complications of antiretroviral therapy, including zidovudine and toxic mitochondrial myopathies related to other nucleoside-analogue reverse-transcriptase inhibitors (NRTIs), HIV-associated lipodystrophy syndrome, and immune restoration syndrome related to highly active antiretroviral therapy (HAART); (3) opportunistic infections and tumor infiltrations of skeletal muscle; and (4) rhabdomyolysis. Introduction of HAART has dramatically modified the natural history of HIV disease by controlling viral replication, but, in turn, lengthening of the survival of HIV-infected individuals has been associated with an increasing prevalence of iatrogenic conditions.

Animal models of myositis

Current animal models of human myositis include spontaneous, induced, and transgenic models. Although it is clear that none of these models possesses all the features of the human diseases, they may provide insight into the pathophysiologic mechanisms, and possibly the therapy, of inflammatory muscle disease. Because the human IIMs are phenotypically heterogeneous, but may be divided into more homogeneous subgroups based upon clinical or serologic features, it is possible that different pathogeneses are involved in different subgroups. It is unlikely that any single model would reproduce all features of the human disease. It may be possible, however, to gain insight into some subgroups of the human disease if certain animal models faithfully reproduce one or more subtypes or aspects of the IIMs. Because immunogenetic risk factors, and exposure to certain environmental agents important in triggering myositis in genetically susceptible persons, may be necessary components for human disease induction, transgenic approaches to humanizing murine immune systems and a better understanding of environmental risk factors will be productive avenues for future research. Additional investigations into the molecular basis of the human myositis syndromes and the pathogenesis of the spontaneous, induced, and transgenic animal models should ultimately allow for better understanding and therapy of these diseases.

Inflammatory myopathies

Inflammatory myopathies are the result of infiltration of inflammatory cells into striated muscle, with or without an association with an underlying cause. Two broad classifications are IIMs and secondary inflammatory myopathies associated with other diseases. Standard diagnostic criteria for inflammatory myopathy include the presence of weakness or loss of specific muscle group function, an increase in CK, EMG changes associated with muscle membrane instability, and histologic evidence of inflammation. Not all these criteria, however, must be present. Fresh-frozen biopsy from two proximal muscles is recommended for biopsy confirmation. IIM can either focally affect head or neck muscles or be more diffuse. MMM is an immune-mediated disease characterized by a humoral antibody produced against the unique type IIM and type I variant mvofibers of masticatory muscles of dogs, which causes inflammation and loss of function of the muscles of mastication. Idiopathic polymyositis can affect focal muscle groups (extraocular, laryngeal) or present as multifocal or diffuse involvement of skeletal muscle in the cat and dog. Familial canine DM is an inflammatory disease of the striated muscle, skin, and vasculature in young Collies, Shetland Sheepdogs (Shelties), and, rarely, Collie-crossbred dogs. Immunosuppressive therapy is the key to successful treatment. Protozoal parasitic myopathies are the most common cause of clinically relevant secondary inflammatory myopathies. The degree of systemic involvement is often the limiting factor to successful treatment. Early recognition of the clinical signs for proper diagnostic testing and institution of appropriate therapy can result in a rewarding outcome in treating inflammatory myopathies in the cat and dog.

The feline model of neuroAIDS: understanding the progression towards AIDS dementia

Feline immunodeficiency virus (FIV) is a neurotropic lentivirus that produces a protracted state of immunodeficiency and encephalopathy in the cat. Recent evidence has shown several similarities to the natural progression of human immunodeficiency virus infection (HIV-1) associated degenerative effects on the central and peripheral nervous systems. Similar to HIV-1, FIV-induced encephalopathy neurovirulence is strain dependent, results in progressive immunodeficiency and increasing early peripheral but not brain viral load, preferentially affects the developing nervous system, produces quantifiable behavioural and neurophysiological impairment that is not directly linked to neuronal infectivity, and induces neuronal injury and loss both in vivo and in vitro. This paper highlights the cumulative scientific body of evidence supporting the use of the feline model of neuroAIDS.

Influence of handling procedures on rat plasma creatine kinase activity

Ten-week-old Sprague-Dawley rats were held behind the front legs before and during anesthetic injection of sodium pentobarbital (group 1, 12 rats), or lifted by the base of the tail before and during injection (group 2, 12 rats). Creatine kinase (CK) values were higher (P = 0.004) in group 1 (median 564 IU/L) than in group 2 (median 272 IU/L). Handling rats by holding them behind the front legs may reduce the usefulness of CK activity as a measure of muscular disorders.