Feline Heartworm Disease
Your eyes did not fool you. The title is correct. A landmark study was led by two Auburn University venterinary professors that proved immature heartworms cause lung disease in cats. Heartworms were long associated with only dogs.
Previously adult heartworms were believed to be the only dangerous kind. “This [study] redefines the diseases in cats and it emphasizes the need for prevention,” said Ray Dillion, the Jack O. Rash Chair of Medicine in Auburn University’s College of Veterinary Medicine. At the 2007 American College of Veterinary Intenal Medicine Forum in Seattle, Dillion presented the study. It was also published in a parasitology supplement to the scientific jouranl, Veternary Medicine.
Immature heartworms grow to only one or two inches long, yet they still cause Heartworm Associated Respiratory Disease. Heartworm infection is the same for cats and dogs. A mosquito carrying microscopic-size heartworm larvae bites into the animal. In cats, the heartworms will die three or four months after infection. By then, the larvae has disintergrated into the lungs and leaves the diseases to create lung tissue damage. This can occur even if the cat never has an adult heartworm. A six-month time span is usually associated with adult heartworms in dogs.
Other studies have focused on heartworms in cats. “But we now know that reasearch should have looked more at the lungs for answers,” said Byron Blagburn, a parasitologist and Auburn University professor. “This is due to thinking that the heartworms would affect cats just like dogs. They are more likely to infect dogs’ hearts, but cats’ lungs.”
In dogs, heartworms can live three to five years. The heartworms can grow to 16 inches long. The damage in dogs is obvious. Heartworms affect cats differently. They leave no evidence related to heartworms and cause serious lung disease. “Immature heartworms in cats are like juvenile delinquents and hit-and-run drivers,” Dillion said.
Serve inflammation occurs when immature heartworms die in the lungs. Cats the have asmthma-like symptoms of wheezing, coughing and breathing difficultly. Some cats will have the disease for the remainer of their lives.
Some researchers have found it hard to convince some veterinarians and pet owners that heartworms are a problem for cats. “Heartworms are very difficult to diagnose in cats and we hope to add new information to help veterinarians spot the diesease. Prevention is best, because there is no cure yet, other than treating the symptoms, ” said Blagburn.
Preventative products have been on the market fo years, but only three percent of cats have been on the medication. “Practitioners probably have seen the disease often in cats, but did not recognize it because the testing of blood samples from dogs is specific to adult heartworms only and are not useful in cats. Cats needing to go on heartworm prevention are not tested prior to the start of medications,” Dillion said.
Auburn Univeristy researchers now want to determine the disease’s long-term effects. “We also need to know how heartworms might interact with other lung diseases, allergies, asthma and other illnesses,” Blagburn said.
Dillion also conducted a study that found that both outdoor and indoor cats in the Southeast get heartworms. The South has a long breeding season for mosquitos, adding to the respiratory disease problem. Blagburn adds, “There is no better example of how beneficial research can be than this study.”
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