A dairy cow on a farm near Listowel, Perth County, has contracted rabies.
"The cow was most likely in contact with a rabid wild animal, such as a skunk or fox," said Dale Lyttle, senior public health inspector.
It is the third case in Perth County since 2015.
Rabies vaccine was distributed in rural areas of North Perth earlier this year.
The local health unit is currently working with the farm to determine potential human exposure.
Drinking pasteurized milk from a rabid cow is not considered dangerous.
Rabies has been detected in Perth County skunks last year and again in January.