Heartworm and Your Pet
What is heartworm?
Heartworm disease is a serious and potentially fatal disease affecting dogs and cats. It is spread when a mosquito carrying young heartworms, known as microfilaria, bites a dog or cat, and passes the microfilaria into the pet's bloodstream. Microfilaria live mainly is the small vessels of the bloodstream and when fully developed they move to the heart and surrounding vessels where they grow to adults and start reproducing. The disease is not spread directly from pet to pet. An intermediate host, the mosquito, is required for transmission. Spread of the disease therefore coincides with mosquito season. Indoor cats can be exposed to heartworm too. 25% of cats diagnosed with heartworms are reported by their owners to be indoor only. This simply means that mosquitoes that come into the house are just as dangerous as the ones outdoors.
What do heartworms do?
Adult heartworms cause disease by clogging the heart and major blood vessels leading from the heart. This reduces blood supply to other places in the body, particularly the lungs, liver and kidneys, leading to malfunction of these organs. Pets infected with heartworms may not show any signs of disease for as long as two years and by the time signs are seen, the disease is well advanced. The signs of heartworm disease depend on the number of adult worms present, the location of the worms, the length of time the worms have been present, and the degree of damage to the heart, lungs, liver, and kidneys.
What are the signs?
The most obvious signs are a soft, dry cough, shortness of breath, weakness, nervousness, listlessness, and loss of stamina. All of these signs are most noticeable following exercise, when some dogs may even faint. Listening to the chest with a stethoscope will often reveal abnormal lung and heart sounds. In advanced cases, congestive heart failure may be seen and the abdomen and legs will swell from fluid build up. Severely infected dogs may die suddenly during exercise or excitement. Damage to the liver and kidneys may also be present, and some cats may experience weight loss and vomiting
How do you diagnose it?
In most cases, diagnosis of heartworm disease can be made by a blood test that can be run in the veterinary hospital or by a veterinary laboratory. For cats, there is not test that is 100% reliable, so a combination of tests must be used.
How do you treat Heartworm?
Dogs: Adult heartworm can be killed using an injectable drug that is given for two days. In more serious infections, these injections may be divided and given thirty days apart. The adult worms die in a few days and start to break down. As they do, they are carried to the lungs, where they lodge in the small blood vessels and are eventually reabsorbed by the body. This can be a dangerous period so it is essential that the dog be kept quiet and not be allowed to exercise for one month following treatment. The first week after the injections is critical because the worms are dying and a cough may be noticeable for up to eight weeks after treatment. Approximately one month later the dog is returned to the hospital to recieve a drug to kill the microfilariae.
There is some risk involved in treating dogs with heartworms, although fatalities are rare. Dogs diagnosed with advanced heartworm disease may have considerable damage to the heart, lungs, blood vessels, kidneys, and liver. A few of these cases will be so advanced that it will be safer to treat the organ damage rather than risk treatment to kill the heartworms. These dogs may also need lifelong treatment because of these damaged organs.
Cats: There is no drug approved for treating heartworms in cats. Treatment is provided for symptoms of heartworm disease to help the cat survive until the worms die, in about two years. Because of this lengthy illness, several months of treatment are needed.
Can Heartworm Disease be prevented?
There is excellent heartworm prevention available for both dogs and cats. Monthly prevention is recommended during heartworm season, and year-round prevention should be provided to pets living in warmer climates. Preventative products are safe, effective and easy to use., and are available in chewable tablets or topical ointments. Ask your veterinary team how to protect your pet today!
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