The Illinois Department of Agriculture is investigating reports of distemper in dogs, including two sold at suburban pet stores, officials said Tuesday.

There is one confirmed case of the disease that can be deadly for dogs, said state veterinarian Dr. Mark Ernst of the Illinois Department of Agriculture. That case was in the Chicago area, but state officials would not confirm the exact location. The dog has not died from the disease, state officials said.

There have been two other reports of distemper, and state officials are investigating, Ernst said. Ernst said canine distemper is very rare, but he could not provide an estimate of the number of cases Illinois typically sees each year.

The Humane Society of the United States issued a statement last week indicating two puppies purchased in the Western suburbs were diagnosed with the disease. A dog bought in December is under the care of a veterinarian and one purchased in January has died, according to the Humane Society report.

However, Ernst said those cases remain under investigation and he will have more information at a later date.

“We’re trying to whittle it down and confirm the source. It may be very difficult to get down to the absolute source because we are moving backwards over a period of time,” Ernst said.

The one confirmed case involves a dog that had been vaccinated, he said.

Ernst said the disease, which does not affect humans, can come from many sources, though it is not common.

“It is not a disease that you can specifically say comes from filthy conditions. It’s just a matter of one dog (being) infected,” said Ernst. It can spread among animals much like illness spreads to humans through schools and day-care centers, he said.

The disease is difficult to treat and can be debilitating for dogs that survive. Often animals that recover have lasting neurological effects, causing them to twitch or have seizures, Ernst said. Symptoms of distemper include fever, loss of appetite, eye and nasal discharge, or respiratory distress and diarrhea. Those who suspect their dogs have the disease are asked to inform the Illinois Department of Agriculture.

“If they are showing any signs of respiratory illness you need to have the animal checked out by a vet,” Ernst said.

bslodysko@tribune.com