ARKLE Veterinary Care
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HEARTWORM DISEASE & PREVENTION-What’s the big deal?
Indoor cats have been shown to have higher infection rates than outdoor cats, so all cats are at risk, even though it has taken us a long time to be able to learn about it. Diagnosis is very difficult in cats because most heartworm tests detect adult female heartworms (or the microfilaria they produce) and work best if there are at least 3 adult worms present. This is fine in dogs, who have high numbers of worms that usually produce lots of microfilaria. But in cats, adult heartworms do not give birth to microfilaria (“baby heartworms”) and adults, if they develop, are usually only 1 or 2 in number. Because cats are not the “normal” host for heartworms, the cat’s body tries to kill or wall off the immature heartworm as it travels through the body as a molting larva. While the cat’s body tries to isolate and destroy the heartworm they may form cysts in any part of the body and cause massive damage to the cat’s own tissues. This is why heartworm infections in cats can cause many different signs and be so difficult to identify. Signs may include circling, seizures, lethargy, vomiting, coughing, trouble breathing or sudden unexplained death. Cats cannot be treated for heartworms. Often, the cat will react so strongly to the immature heartworms that they develop a sometimes fatal lung disease called HARD (Heartworm Associated Respiratory Distress) Syndrome. This may be mistaken for asthma. At the present time there is no treatment for adult heartworms in the cat. The medications used in dog heartworm treatment make cats develop blood clots which plug blood vessels and kill the patient. 70% or more of cats treated for heartworms will die during treatment. In cats, treating to control the reactions to the heartworms is continued until it is likely that all the adult heartworms have died, usually in two or three years in most cats. For more information click on the MOSQUITO
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In many heartworm infections there is a particular stage of the heartworm called microfilariae, which circulate throughout the dog’s bloodstream. These tiny worms are only visible under a microscope. This stage is the baby heartworm produced by adult female heartworms living in your dog’s heart and large pulmonary arteries. These microfilariae are easily killed by many of today’s heartworm preventatives. When large numbers of these “baby heartworms” die, they can clog up the small vessels in major organs of your dog’s body, like the kidneys. Their death can also trigger abnormal clot formation in your dog’s circulatory system that leads to a condition called DIC, or Disseminated Intravascular Coagulation, which means your dog’s body can have thousands of “strokes” in every major organ from loss of circulation caused by the tiny clots triggered by the microfilariae. This can lead to a painful death. Why was my puppy or cat started on heartworm prevention without a test? Isn’t this dangerous? It takes a minimum of 6 months for an adult female heartworm to develop and begin producing the dangerous microfilariae in dogs. But dogs can get infected anytime they are bitten by a mosquito carrying the heartworm disease. So puppies are started on prevention as soon as they start going to the vet, usually at 6-8 weeks of age. Cats are not as good a host for the heartworms and so many of the life stages do not develop like they do in dogs. Cats rarely have enough adult female heartworms present to produce microfilariae. It is so uncommon, in fact, that heartworm testing before starting prevention is not required in cats. Why do I have to have a prescription from my veterinarian to get heartworm prevention? Because the potential exists for a dog or cat to have a fatal reaction to the medication if they are infected with some stages of the heartworm, and the medication is used to treat internal parasites, there is a legal requirement in this country for a veterinarian to examine your pet, run any needed tests and educate you, the pet owner, in how to best use this medicine to protect your pet’s health and safety. All drugs that have been shown to be safe and effective for the prevention of heartworm disease in dogs and cats are prescription only medications in the United States, just like medications a human physician might prescribe to treat or prevent the development of disease conditions for people, such as blood pressure medicine, drugs to control cholesterol levels or antibiotics for certain infections. Use of these drugs in any way other than intended could cause harm to the patient, and so is illegal. Top |
