Canine circoviral hemorrhagic enteritis in a dog in Connecticut

Abstract

A 5-mo-old Bassett Hound-Labrador Retriever cross was autopsied following a bout of lethargy, inappetence, and bleeding gums. Mucous membranes were white, and the small intestine was blue-black; the colon contained black feces. The spleen was swollen, and multiple lymph nodes were enlarged and hemorrhagic. Microscopically, the small intestine had focal crypt cell necrosis and circumferential transmural vasculitis, the latter the cause of infarction and the blue-black coloration. Lymphocytes were necrotic in spleen and lymph nodes, and erythrophagocytosis was present in some nodes. Vasculitis was present in brain, meninges, lung, liver, and kidneys. Electron microscopy revealed aggregates of 15-18 nm round viral particles in damaged crypt cells and in the endothelium of small blood vessels. Electron-dense intracytoplasmic inclusions consisting of paracrystalline-arrayed virus were demonstrated in macrophages in medullary lymph node sinuses. These virions were identified as circovirus, which was confirmed by real-time PCR and sequencing.

Keywords: Mississippi; canine circovirus; canine shelter; crypt cell; hemorrhagic enteritis; vasculitis.

Figures 1–6.

Canine circoviral enteritis. Figure 1. The entire small intestine is discolored dark maroon to blue from numerous oval red-to-black infarcts. Colonic contents are maroon, a mixture of blood and feces. Stomach and pancreas are unaffected. Figure 2. Opened small intestine reveals numerous oval, dark maroon to black infarcts. Figure 3. Focal crypt cell necrosis in the small intestine. H&E. 600×. Figure 4. Small intestinal necrotic crypt, stained by the Lendrum method to show additional cellular detail. 600×. Figure 5. Hyaline degeneration of a small arteriole in the deep submucosa of the small intestine. H&E. 400×. Figure 6. Vasculitis in the cerebrum. Missing endothelial cells have been replaced by mononuclear leukocytes. H&E. 400×.

Figures 7–9.

Canine circoviral enteritis. Figure 7. Fibrinoid necrosis in a small pulmonary arteriole, surrounded by plasma cells and macrophages. H&E. 400×. Figure 8. Aggregates of virus, some arranged in rows, in a crypt epithelial cell. Bar = 100 nm. Figure 9. Circoviral particles in paracrystalline array in macrophage cytoplasm from an affected lymph node. Bar = 100 nm.