BY DOMINGO RAMIREZ JR. RICHLAND HILLS -- A popular retired police dog who received donations of more than $10,000 to cover expenses for medical problems has been euthanized, police said Tuesday.Hiko, a 10-year-old Belgian Sheepdog, was put down on Monday on the recommendation of the Richland Hills Police Department veterinary staff.For two years, Hiko had been suffering from a spinal cord infection and vertebrae problems.In 2007, about 200 residents donated more than $10,000 to save his life from the infection after Richland Hills funds for his care had been depleted.The money sent from donors around the North Texas region covered his treatments and surgery.Last year, the police department sent out personalized thank-you cards, signed with a paw print of Hiko.Hiko had joined the department in 2005 as a tracker and a drug detection dog.