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2016-08-24 / Columnists

Pets, Pets, Pets

The following is a tutorial about heartworm in dogs from the FDA and the American Heartworm Society. This information must be stressed because many owners confuse deadly heartworm with intestinal parasites, and fail to provide their dogs with monthly or other preventive meds:

What Is Heartworm; What Causes It? Heartworm is a serious disease that results in severe lung disease, heart failure, other organ damage, and death in pets. It is caused by a parasitic worm called Dirofilaria immitis, spread through the bite of a mosquito. The dog is the definitive host, meaning the worms mature into adults, mate, and produce offspring while living inside a dog. The mosquito is the intermediate host, meaning the worms live inside a mosquito for a short period in order to become infective. They are called “heartworms” because the adults live in the heart, lungs, and associated blood vessels of an infected animal. In the US, heartworm is most common along the Atlantic and Gulf coasts and along the Mississippi River, but has been reported in dogs in all 50 states.


LI Golden Retriever Rescue is collecting unwanted gold. LI Golden Retriever Rescue is collecting unwanted gold. Heartworm Lifecycle In Dogs: In an infected dog, adult female heartworms release their offspring, called microfilariae, into the dog’s bloodstream. When a mosquito bites the infected dog, the mosquito becomes infected with the microfilariae. Over the next 10 to 14 days, the microfilariae become infective larvae while living inside the mosquito. Microfilariae cannot become infective larvae without first passing through a mosquito. When the infected mosquito bites another dog, the mosquito spreads the infective larvae to that dog via the bite. In the newly infected dog, it takes between six and seven months for the infective larvae to mature into adult heartworms. The adult heartworms mate and the females release their offspring into the dog’s bloodstream, completing the life-cycle.

Inside a dog, a heartworm’s lifespan is five to seven years. Adult heartworms look like strands of cooked spaghetti, with males reaching about 4 to 6 inches in length and females about 10 to 12 inches. The number of worms living inside an infected dog is called the worm burden. The average worm burden in dogs is 15 worms, but that number can range from 1 to 250 worms.

How to Test for Heartworm: The most common test to check a dog for heartworms is called an antigen test. This blood test detects specific proteins, called antigens, which are released by adult female heartworms into the dog’s bloodstream. Usually, antigen tests can accurately detect infections with one or more adult female heartworms that are at least seven or eight months old, but the tests generally do not detect infections that are less than five months old.

There are also tests that detect microfilariae in a dog’s bloodstream. Microfilariae in the bloodstream indicate the dog is infected with adult heartworms (because only adult heartworms can mate and produce microfilariae). These can be detected in a dog’s bloodstream about six to seven months after it is bitten by an infected mosquito .

When to Test for Heartworm: Dogs older than six to seven months should be tested for heartworms before starting heartworm prevention. A dog may appear healthy, but on the inside, heartworms may be living and thriving. If a heartworm-positive dog is not tested before starting a preventive, the dog will remain infected with adult heartworms until it gets sick enough to show symptoms. Heartworm preventives do not kill adult heartworms. Also, giving a heartworm preventive to a dog that has an adult heartworm infection may be harmful or deadly. If microfilariae are in the dog’s bloodstream, the preventive may cause them to suddenly die, triggering a shock-like reaction and possibly death. Annual testing of all dogs on heartworm prevention is recommended. Talk to your veterinarian about the best time for your dog.

Heartworm Symptoms: In early stages, many dogs show few or no symptoms. The longer the infection persists, the more likely symptoms will develop. Active dogs, dogs heavily infected, or those with other health problems often show pronounced clinical signs.

Signs of heartworm disease may include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite and weight loss. As the disease progresses, pets may develop heart failure and a swollen fluid-filled abdomen. Dogs with large numbers of heartworms can develop a sudden blockages of blood flow within the heart leading to cardiovascular collapse.

Treatment For Heartworm Disease: The drug Immiticide is FDA-approved to kill adult heartworms in dogs. It contains arsenic and is given by deep injection into the back muscles of the dogs. Another drug, Advantage Multi for Dogs is FDA-approved to get rid of microfilariae in the dog’s bloodstream. This is a topical solution applied to the dog’s skin.

Treatment for heartworm is not easy on the dog or on the owner’s wallet. It can be potentially toxic to the dog’s body and can cause serious complications, such as blood clots to the dog’s lungs. Treatment is expensive because it requires multiple visits to the veterinarian, bloodwork, x-rays, hospitalization, and a series of injections with Immiticide.

Best Treatment Is Prevention! Products FDA-approved to prevent heartworms in dogs require a prescription. Most are given monthly, either as a liquid applied on the skin or as an oral tablet. Both chewable and non-chewable tablets are available. One product is injected under the skin every six months, and only a veterinarian can give the injection. Some heartworm preventives contain other ingredients effective against certain intestinal worms and other parasites (such as fleas, ticks, and ear mites). Year-round prevention is best! Talk to your veterinarian to decide which preventive is best for your dog.

* Help LIGRR Go for the Gold: Long Island Golden Retriever Rescue (LIGRR) is collecting unwanted gold (single earrings, broken items, pieces of chain) It’s a big win. You de-clutter your jewelry box, donate it to LIGRR and the money made will help the dogs win big. Call LIGRR at 516 578 3803 so that a volunteer can arrange to get your donation.

*For Adoption at Babylon Shelter (631- 643-9270) Lamar St. W. Babylon: “Polly” 16-305 is a Pit who appears to have been neglected and used to breed. She wants nothing more than to try to sit in your lap and be with people. “Smile” 6-291 is an adorable gray kitten who would love to find a home while she still is a kitten.

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