FELINE IMMUNODEFICIENCY VIRUS-ASSOCIATED MYOPATHY IN THE ADULT CAT

Human immunodeficiency virus (HIV-1) associated myopathy can be a debi litating disease in humans, leading to weakness, myalgia, and muscle w asting. Subclinical neuromuscular involvement is also common. A range of histologic lesions have been described in both forms that include b oth inflammatory and degenerative changes. The purpose of this study w as to determine whether a myopathy was present in adult cats experimen tally infected with feline immunodeficiency virus (FIV). Six specific pathogen-free, laboratory-housed cats were challenged intravenously wi th 1000 TCID50 of the Maryland isolate of FIV (FIV-MD) at 8 months of age. The highest serum creatine kinase values were seen at 18 months p ostinfection (mean 9838, SD 4805 U/L) compared to preinfection (mean 9 50, SD 374 U/L). Needle EMG studies revealed abnormal spontaneous acti vity in 2 cats. All FIV-MD infected cats exhibited at least one abnorm ality in muscle pathology. Of the 24 muscle samples, 15 (63%) had hist opathologic lesions. The predominant histologic abnormalities consiste d of perivascular and pericapillary lymphocytic infiltration, and myof iber necrosis, phagocytosis, and regeneration. Lymphocytic infiltratio n was graded 2+ or higher in 12 of 24 muscle samples (0 = negligible; 4+ = extensive). Immunohistochemical phenotypic lymphocyte labeling in all cats demonstrated only CD8+ lymphocyte staining. This report demo nstrates the presence of a FIV associated inflammatory myopathy in the adult cat. Several similarities are apparent in comparison to HIV-1 a ssociated polymyositis reported in humans. Future studies in the cat m ay thus prove useful in elucidating the pathogenesis of retrovirus rel ated myopathy in humans. (C) 1998 John Wiley & Sons, Inc.