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.

Chronic IPO (CIPO) is typically primary, caused by intestinal leiomyositis, and causes intermittent gastrointestinal signs and weight loss. The aetiology of CIPO remains poorly understood but may represent an immune-mediated destruction of intestinal smooth muscle cells of CIPO in the dog using immunosuppressive corticosteroid therapy.