In a country isolated from the rest of the world, in which horse importation is strictly prohibited, local horses have tested positive for antibodies against a virus previously undetected in equids on the island: Several horses residing at a single stable in northern Iceland tested positive for borna disease virus (BDV) antibodies.

Several of the positive horses showed clinical signs of borna disease—specifically, neurologic problems, said Sigridur Björnsdóttir, DVM, PhD, study author and veterinary officer for equine health and welfare in Iceland. However, veterinarians could not conclude definitively that BDV was the source of the neurologic problems, she added, as other diseases could not be ruled out.

Borna disease is a rare and potentially fatal equine disease most commonly identified in central Europe. In the study, Björnsdóttir and colleagues explained, "The clinical signs in horses usually start with disturbances in feed intake, fever, and various degrees of somnolence. Later, ataxia (incoordination) and other gait disturbances, more severe somnolence, and finally paralysis of extremities and head develop. Other mental changes are also common, such as depression, coma, and excitations."

Researchers don't yet know the virus' transmission routes; however, previous research has suggested reservoir hosts—such as wild birds, rodents, and insectivores—are likely involved, the team noted