Detection of Circovirus in Foxes with Meningoencephalitis, United Kingdom, 2009-2013

Abstract

A fox circovirus was identified in serum samples from foxes with unexplained neurologic signs by using viral metagenomics. Fox circovirus nucleic acid was localized in histological lesions of the cerebrum by in situ hybridization. Viruses from the family Circoviridae may have neurologic tropism more commonly than previously anticipated.

Keywords: United Kingdom; brain; cerebrospinal fluid; circovirus; cyclovirus; encephalitis; foxes; meningoencephalitis; neurologic disease; random amplification; serum; viruses.

Figure 1

Histopathologic features of brain tissue from foxes with possible virus-induced neurologic disease. A) Multifocal, randomly distributed areas of severe encephalitis and meningitis in the cerebrum (original magnification ×40). B) Detail of encephalitis in the cerebrum (original magnification ×200). Gray and, to a lesser extent, white matter of the cerebrum showed randomly dispersed areas of astrocytosis, gliosis, and infiltration with lymphocytes and plasma cells. Blood vessels in affected areas show perivascular cuffing with distention of Virchow-Robin spaces with up to 10 layers of lymphocytes and plasma cells (arrow). C) Detail of white matter in the cerebellum (original magnification ×400). Axons in affected white matter showed degeneration, characterized by formation of spheroids, shrinkage, and fragmentation; axon sheaths containing microglia or macrophages; and presence of gitter cells in surrounding neuropil. Cerebellum was mildly affected, and meninges, especially of the cerebrum, were frequently distended with lymphocytes and plasma cells. D) Detail of gray matter of cerebrum (original magnification ×400). Individual neuronal cell bodies were frequently surrounded by up to 5 glial cells (i.e., sattelitosis) and showed margination of Nissl substance, hyperchromasia, degeneration, and necrosis. Tissue sections were subjected to conventional hematoxylin and eosin staining.

Figure 2

Detection of fox circovirus–specific transcripts in brain tissue of foxes with neurologic disease showing in situ hybridization of cerebrum with fox circovirus replication initiator protein gene–specific probe (original magnification ×200). A) Negative control fox VS7100012. The serum sample from this fox was negative for circovirus, and the animal did not exhibit signs of neurologic disease. B, C) Affected foxes VS7100005 and VS7100003, respectively. Both animals had neurologic disease, and their serum samples were positive for fox circovirus (see Table 1 for more information regarding these foxes). Black arrows indicate mononuclear cells in perivascular cuffs, blue arrows show inflammatory infiltrates in the neuropil, and red arrows point to staining in neuronal somata in cerebral gray matter of circovirus–positive animals with neurologic disease.