Heartworm and Your Pets

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Please keep your pet on heartworm prevention

Heartworm and Your Pets

I want to share with you today the IMPORTANCE of heartworm prevention.  In the last month I have heard from so many people (friends and clients) that their pet has been diagnosed with heartworm positive results.  That really scares me and it should scare you too.  It only takes one mosquito bite to give your pet heartworms.  A yearly blood test, performed by your dog’s veterinarian, is the only accurate way to detect heartworm infection.

It is important to understand that heartworm infections are not detectable until about six months after a dog has been bitten by a heartworm-infected mosquito. (This is why it’s not possible to have a heartworm test performed monthly and give the preventative only if an infection is found.) Blood tests generally will not detect heartworms in a dog until the larvae have matured into adult worms, which takes about six months following initial infection. Symptoms, such as coughing, lethargy and difficulty breathing, will not show up until the infection is advanced.

The life of the heartworm


Microfilariae are actually microscopic larvae. They live in the blood of most heartworm-infected dogs. Microfilariae are ingested by a mosquito that feeds on an infected animal, where they molt twice over a period of about 2 weeks and develop into infective larvae.


There are two main phases of growth in the larval stage. In the first, the infective larvae are passed from the mouth parts of the mosquito to your pet’s skin, then burrow into your dog’s tissue through the bite wound. In about one to three days, the larvae mature into the second phase during which they migrate through your dog’s tissue for several weeks.

Juvenile worm

In about two months after initial infection, the larvae undergo a final molt and become juvenile (sexually immature) worms. Juveniles range from 1 to 3 cm in length. They enter your dog’s vascular system, and move from there to your dog’s heart and lungs in as early as 70 days after initial infection. Once arriving, they mature to adulthood.

Adult worm

Heartworms generally mature into mating adults in the pulmonary artery — or the artery responsible for moving blood from the right ventricle of the heart to the lungs. This artery can become clogged with both live and dead worms, resulting in any number of health issues, including but not limited to infection, clogging of the arteries, and various heart malfunctions — even death.

An infected dog will typically be carrying microfilariae within 6 to 7 months after first being infected by the initial mosquito bite. And the cycle continues.

Heartworm Treatments


The current Canine Guidelines for the treatment of heartworm recommend starting dogs on heartworm preventative immediately, regardless of whether you intend to proceed with Immiticide treatment. “The logic for this approach is to kill susceptible heartworm larvae and thus prevent re-infection of the dog, while allowing less susceptible juvenile worms, the opportunity to develop into more susceptible adult worms [Immiticide won’t kill juvenile worms]. . . . Administration for two to three months should result in reduced antigenic mass [the part that causes a reaction], which in turn may reduce the severity of pulmonary thromboembolism [less chance of a reaction to the Immiticide treatment].”


There are three conventional methods of treating heartworm: a “fast kill” method using Immiticide (melarsomine); a “slow kill” method using Heartgard (ivermectin); and a surgical method, where the worms are surgically removed from the arteries. In addition, there are so-called holistic treatments, such as Paratox homeopathic or herbal preparations.

In each case, and indeed even if no treatment is done, there is a risk of the dog dying from a pulmonary embolism caused by worm die-off. In addition, there is risk while the worms are present of damage to the heart, the arteries, and the rest of the body, due to inflammation and immune reaction.

When deciding which method to use, you need to take into account the age of your dog, his level of activity, and the severity of the infestation.

New research has shown that it is also important to treat for Wolbachia, a parasite that lives symbiotically with the heartworms and may be responsible for much of the damage that they cause, both from inflammation and from pulmonary emboli, no matter what other form of treatment you decide to do.

Cost of Conventional Heartworm Treatment

Conventional heartworm treatment is expensive. The typical protocol for treatment includes bloodwork and x-rays to measure the infection load, antibiotics to kill the parasites that live in the heartworms, pain medication and sedatives, in addition the actual Immiticide, which kills the heartworms. The full treatment protocol generally takes three to four months and costs between $1,000 and $2,000, depending on individual vet fees. Low-cost or charity clinics may offer the treatment for up to 50 percent less than traditional veterinary clinics.

Cost of Slow-Kill Heartworm Treatment

For owners who can’t afford the conventional treatment, the slow-kill treatment method may be an option. Instead of an intensive killing process, the slow-killl method uses monthly Ivermectin doses and quarterly antibiotics. This process can take up to two years to completely kill the heartworms. In the end, the cost may be the same as the conventional treatment, but will be spread out over several months at a cost of approximately $50 per month. However, not all dogs are good candidates for the slow-kill method, so never start your dog on this protocol without supervision from your veterinarian.



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