Feline heartworm disease is caused by the parasite Dirofilaria immitis. Heartworms thrive in areas of the United States, Latin America, Asia and Europe where mosquitoes are most prevalent. Warm, humid climates, such as those in the southeastern United States, are ideal. The disease is carried by a mosquito that draws blood from a heartworm-infected dog. The mosquito acts as an intermediate host, then regurgitates the larvae on a cat. Generally, affected cats do not infect other cats-the disease must pass from a dog to a mosquito to a cat. Both indoor cats and outdoor cats are at risk.
Logically, it seems the best solution for curing cats of heartworm disease would be to kill the worms. Unfortunately, when a worm dies and begins to deteriorate, small pieces of it can clog the arteries, resulting in pulmonary embolism and death. Caparsolate (thiacetarsemide), the drug that has been used to treat dogs for many years, can also be used for cats but the mortality rate of cats on Caparsolate is about the same as those not treated. Owners are usually given medication to administer for certain symptoms. An operation is a last resort. William P. Barclay, DVM, partner and chief of surgery of the Cat Hospital in Illinois, says he will consider surgery only when the patient has seven to 12 worms and he knows the cat will not survive on its own.
Prevention is the best way to keep heartworms out of a cat’s life. The sole preventive on the market, Heartgard by Merck, is available only from licensed veterinarians. A monthly treatment, Heartgard kills heartworm larvae. It can be given alone or mixed with food, and comes in two formulas based on the cat’s weight. The cost is about $3 a month.
If your cat exhibits one of the following symptoms-coughing, gagging, labored breathing, repeated vomiting, lack of appetite, weight loss, lethargy, central nervous system disorders, blindness or heart murmur-talk to your veterinarian. You may want to get your cat tested or start it on a preventive medicine.