Blame the mosquitoes first, but dog owners share responsibility for Alabama having the highest rate of heartworm disease in the nation in 2013, the American Heartworm Society reported Wednesday. Alabama veterinary hospitals and animal shelters each diagnosed an average of 90 heartworm-positive dogs in 2013, compared to 31 per site in 2010. Those gloomy numbers easily topped No. 2 Louisiana’s figure of 81 heartworm-positive dogs per clinic. The good news for Louisiana is that the state was first in heartworm disease three years earlier—the last time the study was conducted—when it had 105 heartworm-positive dogs per clinic. The Wilmington, Del.-based American Heartworm Society stressed that heartworm disease is easily preventable when dogs and cats receive a monthly medication. “We know that far too many pets in Alabama are affected with heartworm disease,” said Chris Rehm, DVM, an American Heartworm Society board member who practices in Mobile, Ala. “However, we also know that veterinarians and pet owners have the power to prevent this deadly disease.” Heartworm disease is spread by mosquitoes and is found in all 50 states, but the threat tends to be worse in warm-weather locations, especially the Southeast. The top 10 states on the 2013 list were, in order, Alabama, Louisiana, Mississippi, Texas, Arkansas, South Carolina, North Carolina, Tennessee, Georgia and Oklahoma. Louisiana, Mississippi and Texas topped the chart in 2010, with Alabama at No. 7. More than 4,500 veterinary practices and shelters participated in the 2013 study, contributing data from 3.5 million patients. Veterinarians who completed a questionnaire noted that the increase in heartworm cases in their states could be explained by the fact that too many pet owners did not administer heartworm preventives on time and as directed. “Heartworm disease is a deadly, but preventable, disease,” Dr. Rehm said. “That’s why the American Heartworm Society recommends that pets be tested for heartworm each year and that dogs and cats be put on preventive medicine for heartworm year-round.” Preventing the disease runs less than 10 percent of the cost of treating it, the American Heartworm Society stated. A dog cleared of heartworms can still suffer permanent damage to organs and the circulatory system, the organization warned. No approved treatment medication exists for cats.