The California Department of Food and Agriculture says so far, two horses in Placer and Yuba Counties tested positive for West Nile virus.
As a result, one of the horses was euthanized.
Horse owners are urged to have their animals vaccinated to make sure they are protected as much as possible against the disease.
To help prevent the disease which is carried by mosquitoes you can carry some basic precautions such as draining standing water and cleaning water containers at least weekly.
And you should schedule pasture irrigation to minimize standing water.
Mosquitoes become infected with the virus when they feed on infected birds.
Mosquitoes then spread the virus to horses.
