Heartworm Disease a Threat to Millions of Untreated Dogs and Cats in U.S., Say Experts

According to a Nov. 17 press release, the American Heartworm Society (AHS) recently released new guidelines for diagnosing, preventing and managing heartworm infections in both dogs and cats. Although a cat's immune system is more resistant to heartworm infection and disease than a dog's, it takes far fewer worms in a cat to cause serious health problems. This is little comfort to cat owners, however, when looking at actual statistics. The AHS says that 61-90 percent of non-medicated cats exposed to heartworm larvae will become infected, but virtually 100 percent of non-medicated dogs exposed will become infected.

According to an article in online magazine "Dog Owner's Guide," heartworms are parasites that initially infect the right side of an animal's heart, through a vein. Once found primarily in southern climates, heartworm disease is now a concern of pet owners nationwide. Heartworm disease was discovered in dogs more than a hundred years ago; it was first documented in cats in the 1920s. It's since been found in wolves, coyotes, foxes and some other animals.

Heartworms go through several life stages before development into adults. The mosquito serves as the carrier from an infected animal to an uninfected one. The mosquito ingests the heartworm larva when it bites an infected dog or other animal and deposits the larva in an uninfected host. When the larva in the new host emerges as an adult, it travels through a vein to the right side of its host's heart and eventually reproduces. In a dog, adult heartworms can reach 14 inches in length; they live and reproduce in a dog's or cat's heart and pulmonary arteries. In severely infected animals, numerous worms grow and fill up the heart chamber.

Tom Nelson, DVM and president of the AHS, says the new heartworm prevention and treatment guidelines recommend that pet owners have their dogs and cats tested annually for heartworm and use a year-round heartworm preventative treatment. Individual veterinarians may have differing opinions on the need for annual testing if a pet is on a year-round prevention plan, however.

In cats, fewer than six heartworms can cause severe problems because a cat's heart and blood vessels are so small. An infected cat eventually develops respiratory stress, coughing or chronic vomiting. In a dog, says the AHS, it generally takes 25 to 50 worms to cause such severe problems. However, death from heartworm disease can be sudden in both dogs and cats.

The AHS and most veterinarians say that heartworm disease can be virtually eliminated in household pets if pet owners implement a year-round preventative treatment plan. Heartworm preventative medications, which can only be obtained through a veterinarian, work by wiping out the latter-stage larvae deposited by mosquitoes.

Sources:

Press release, "1-800-PetMeds Warns That More Than 118 Million US Pets Are Vulnerable to Heartworm Disease;" http://www.prweb.com/releases/2007/11/prweb569630.htm

Article; http://www.canismajor.com/dog/hartworm.html