Inclusion Body Myositis in Spring Peepers (Pseudacris Crucifer)

Abstract

Abstract. In 2000, 2 adult captive spring peepers (Pseudacris crucifer) from the same zoological park were humanely euthanized. Histologically, both frogs had degeneration, atrophy, and necrosis of striated myofibers of the tongue admixed with chronic lymphohistiocytic inflammation. One frog had similar lesions in the skeletal muscles of the body wall. Several degenerate and necrotic myofibers contained single, eosinophilic, intranuclear inclusion bodies. Ultrastructural examination of the inclusions revealed nonenveloped, icosahedral, virus-like particles averaging 20-24 nm in diameter. This is the first reported case of inclusion body myositis in frogs and is believed to be due to parvoviral infection.In January 2000 an approximately 2-year-old, female, captive spring peeper (Pseudacris crucifer) (peeper A) was humanely euthanized. It was housed at a zoological park in the Midwestern United States. It had a clinical history of progressive, bilateral, lipid keratopathy. One week before death the peeper had stopped eating and had become lethargic. At necropsy the skin of the ventrum was red. The corneas of both eyes were completely opaque. The liver was black, and the gall bladder was distended. In October 2000 another female, approximately 3-year-old spring peeper (peeper B) from the same zoological park was also euthanized. Gross lesions were not evident at necropsy. Both peepers were originally wild caught in April 1998 in Ohio and were housed together in a 25.0-ϫ 50.0-cm glass aquarium with other wild caught spring peepers and Western Chorus frogs (P. triseriata).Both peepers were submitted whole and fixed in 10% neutral buffered formalin. Tissues were collected, embedded in paraffin, sectioned at 5.0 m, and stained with hematoxylin and eosin (HE). Histologically, many striated myofibers of the tongues of both peepers were hypereosinophilic, markedly swollen, and fragmented-to-fibrillated and had loss of cross-striations. Multifocally, the remaining myofibers were atrophic and surrounded by fibrous connective tissue. There were low numbers of lymphocytes, plasma cells, and macrophages dissecting between degenerate and necrotic myofibers. Several degenerate and necrotic myofibers contained large, eosinophilic, intranuclear inclusion bodies (Fig. 1). Sections of panniculus muscles from peeper B had multifocal myodegeneration and myonecrosis admixed with lymphocytes, plasma cells, and macrophages. There were similar large, eosinophilic, intranuclear inclusion bodies within myofibers. Edema fluid and fibrous connective tissue separated the degenerate myofibers.In addition to the glossitis, peeper A also had bilateral thickening of the corneal stroma by cholesterol clefts, mineral deposits, macrophages, and foamy macrophages. Diffusely, hepatocytes were swollen and had many intracyto- plasmic, clear, smooth-marginated vacuoles. Multifocally, glomerular tufts contained few foamy macrophages and had clear vacuoles and clefts within glomerular mesangial cells. The skin of peeper A had moderate, multifocal, orthokera...