New guidelines that include year-round prevention and testing for heartworms in cats and dogs across the United States was announced by the American Heartworm Society on June 2, 2005, at the ACVIM conference in Baltimore. Guidelines include multifaceted testing for cats because negative antibody tests are not conclusive, and a separate set of instructions for preventive maintenance, said Tom Nelson, DVM, society president. He explained that the change in guidelines, described as fundamental, were prompted by low compliance figures, high incident rates of heartworm in areas not typically considered to be endemic – including California – and the fear that if heartworm disease reaches the wild canid population there will be no way to eradicate it.

Heartworm has been identified in 30 different species, including ferrets, coyotes and seals and was recently diagnosed in four otters at the Fort Worth Zoo, according to Heartworm Society members.

To protect cats and dogs, regardless of region or activity level, the Society now supports year-round prevention and testing, Nelson explained. “Any area where a dog is on prevention, cats should be on prevention,” Nelson said. Despite misperceptions, heartworm is a problem across the country, a fact that is attributed to a mobile society, low compliance levels (studies show that only 75 percent of prescribed doses are given) and the prevalence of irrigation systems and golf courses that create conducive environments for mosquitoes. A Merial study conducted in 2001 reported that many states, including Arizona and Oregon, are reporting higher incidences of heartworm disease and that Indiana was one of the top 10 states where heartworm is reported. Merial is repeating the study but no publication had been released at press time.

Information about cats may come as a surprise to many veterinarians, Nelson added. “We were taught in school that when it occurs in cats it’s a freak of nature,” he said. “Veterinarians as a whole do not understand heartworm in cats. I was one of those nonbelievers but it’s out there. We just don’t recognize it.”

Symptoms in cats often mimic asthma or allergic bronchitis. And while there is no cure, testing and prevention is recommended so that owners are prepared with steroid treatment if acute respiratory distress syndrome-like symptoms are noted, Nelson said.

In addition to increasing compliance, yearly prevention will reduce the potential for the transmission of internal parasites from pets to people, which affects between three and six million people every year, Nelson said. He noted that in 1995, 160 people underwent surgical procedures to remove suspected carcinomas that turned out to be heartworms