Federal health officials believe the disease spread may have started with prairie dogs being infected with monkeypox by a Gambian rat at a Villa Park, Ill., pet distributor.

South Milwaukee pet distributor SK Exotics purchased some of the prairie dogs and moved them to Wisconsin, and two pet stores in the Milwaukee area purchased them.

Mike Hoffer, owner of Hoffer TropicLife, said he got a shipment of 10 prairie dogs from SK Exotics on May 5 but didn't sell any once his staff noticed they were sniffling. Seven of them were euthanized Wednesday and the others died earlier of a respiratory ailment, he said.

He said he has been selling prairie dogs at a rate of about 20 to 25 a year over the last decade.

"They're cute," Hoffer said. "They fall into place someplace between a guinea pig and a rabbit. I think people are maybe blowing it out of proportion."