A rare rat-borne disease is killing dogs in New Jersey following this year’s warm winter, experts say. Leptospirosis, a bacterial disease most commonly spread through rat urine, has left at least two dogs in Bergen County dead and sickened several others, NJ.com reported. “It’s an elevated number for the time of year. Typically, in the winter you don’t see it as much,” said Tracey Horyczun of BluePearl Veterinary Partners in Paramus. “The only thing that comes to mind is that it was a warmer winter.” The sick pooches are believed to have slurped water contaminated with urine from infected wildlife while on walks over the winter with their owners. Two of the five dogs treated at BluePearl died. The other three survived after being treated at Bergen County Veterinary Center. The condition of three more pups in the care of Oradell Animal Hospital wasn’t clear. Leptospirosis causes sudden fever, sore muscles, lack of appetite, diarrhea and other symptoms in dogs and can be passed through squirrels. If left untreated, leptospirosis can cause severe damage to a pet’s organs and become fatal. The disease can also be transferred from one dog to another but is rare in humans. In December, one man died and two others became severely sick from leptospirosis, officials said. The cases were within a one-block radius of each other in the Concourse section of the Bronx. In 2009, a small outbreak of leptospirosis was reported in Brooklyn that left several dogs dead and dozens hospitalized.