Inflammatory Myopathy in Horses With Chronic Piroplasmosis

Abstract

Horses affected by chronic piroplasmosis may develop poor performance and muscle atrophy. Here we investigate the pathological and immunopathological aspects of myopathy occurring in chronic equine piroplasmosis. The study included 16 horses serologically positive for equine piroplasms presenting with clinical signs and supporting serum biochemical evidence of a myopathy. Skeletal muscle was evaluated by histopathology, immunohistochemistry, indirect immunofluorescence, and molecular detection of piroplasms and inflammatory cytokines in skeletal muscle. Histologic lesions included muscle fiber atrophy (100% of cases), degenerative changes (13/16, 81%), and perivascular perimysial and endomysial lymphocytic infiltrates (81% of cases). In 15 cases (94%), muscle fibers had strong immunostaining for major histocompatibility complex classes I and II. T lymphocyte populations were mainly CD3+, CD8+, and CD4+ in equal proportions, with a lower number of CD79α+ cells. The serum from affected horses was tested by indirect immunofluorescence for binding of IgG, IgM, or IgA to sections of normal equine muscle to detect circulating autoantibodies against muscle antigen(s). In all cases, distinct sarcolemmal staining was detected in sections incubated with serum from affected horses, in contrast to sections incubated with phosphate-buffered saline or equine control sera. Reverse transcription polymerase chain reaction (RT-PCR) testing of muscles from affected animals revealed a significant increase of interferon-γ, interleukin-12, and tumor necrosis factor-α gene expression compared to healthy controls. Theileria equi or Babesia caballi was not detected in samples of affected muscle by RT-PCR. Thus, inflammatory myopathy associated with equine piroplasmosis may involve an autoimmune pathogenesis with upregulation of inflammatory cytokines that may cause myofiber atrophy and degeneration.

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

“…It can be speculated that Sarcocystis can induce muscle damage and trigger muscle inflammation at least in 2 different ways: (1) by a direct damage to the cell or (2) by a stimulation of an immune-mediated myopathy. 32 The direct role of Sarcocystis in inducing cell damage and thus possibly stimulating MHC I expression may be related to the perturbance of endoplasmic reticulum (ER) homeostasis, that is, ER stress. ER stress 34 is reported in response to intracellular parasitism 13 and in human inflammatory myopathies.…”

“…A scoring system was designed to assess the degree of fiber atrophy as follows based on assessment of 100 fibers at x200 magnification: mild (score 1), <10% atrophic fibers; moderate (score 2), 10% to 50% atrophic fibers; and severe (score 3), >50% atrophic fibers. 32 A scoring system was also defined for the number of lymphocytes and plasma cells based on light microscopy: no infiltration (score 0); mild infiltration (score 1), 5 to 25 lymphocytes/plasma cells per high-power field (HPF) (x400); moderate infiltration (score 2), 26 to 50 lymphocytes/plasma cells per HPF; and severe infiltration (score 3), more than 50 lymphocytes/plasma cells per HPF. 32 At least 10 fields at x400 magnification were evaluated for each section by 2 independent pathologists (T.B.P.…”

“…The inflammation score was obtained by summing the scores for lymphocytic inflammation, MHC I, and MHC II. 32 For evaluation of MHC I and II, fibers directly adjacent to the inflammatory infiltrate were avoided, since positive endomysial inflammatory cells can make evaluation of sarcolemmal positivity difficult. The positive staining for MHC I and II varied from a continuous staining throughout the sarcolemma to a discontinuous sarcolemmal pattern.…”

Theileria equi-Infektion bei 2 Pferden nach einem Wanderritt in Südfrankreich

“…Trotz der möglichen unerwünschten Wirkungen ist bei Pferden in nicht endemischen Gebieten eine Erregerelimination anzustreben. Zum einen kann nur so eine Übertragung des Erregers auf lokale Zeckenpopulationen und die langfristige Etablierung autochthoner Zyklen wirksam verhindert werden, zum anderen können chronische Piroplasmen-Infektionen zum Krankheitsbild der Polymyositis führen [19]. Bei chronisch infizierten Stuten ist auch eine diaplazentare Übertragung auf den Fetus möglich, was in Aborten oder der Geburt klinisch kranker Fohlen resultieren kann, die oftmals in den ersten Lebenstagen versterben [6].…”

Imidocarb Dipropionate Lacks Efficacy Against Theileria haneyi and Fails to Consistently Clear Theileria equi in Horses Co-infected with T. haneyi<b></b>

“…If ID fails to clear T. equi in co-infected animals, the global equine industry could face tremendous economic losses. Furthermore, persistent piroplasmosis can lead to reduced performance in horses used for athletic events or farming/traction purposes, even in the absence of other appreciable clinical signs [3,25]. The absence of any effective treatment for T. haneyi, and the lack of a consistently effective treatment for T. equi in co-infected horses, will significantly impact producers, farmers, and the international movement of equine athletes.…”