Heartworm Disease and What to Do About It

What Are Heartworms?

Heartworms are parasitic, spaghetti like worms that live in the hearts of animals, where they reproduce and wreak havoc on the animals' health. They typically affect dogs and cats, and spread from one animal to another through mosquito bites. Infestation is highly fatal and is possible virtually any place where there are mosquitos. It is important that all dog owners take measures in preventing their pets from becoming infected with heartworms.

What Do Heartworms Do?

Heartworms are transmitted when they are microscopic babies, or microfilariae. These microfilariae are sucked up from their existing host animal by a mosquito, inside which they will mature for a couple of weeks. Once they've molted to the infectious larval stage, they will migrate to the mosquito's head and wait to be injected into subsequent animals the mosquito bites.

Once an infestation is secured, the microfilariae will live off the matter of the animal while they travel throughout its body. Ultimately, they will grow to up to 10" in length and finally lodge in the heart and lungs. Here, adults, they will reproduce, birthing thousands of microfilariae per day, which will circulate throughout the animal's body damaging much of the tissue they pass through. Some of these will be transfered to the next animal by mosquito. The heart-residing adult worms will eventually kill the current host animal through congestive heart failure.

What Are the Signs / Symptoms?

Until the heartworms mature to adults, which takes about 6 months, dogs typically will not show any signs of infection. There are rare cases when a stray worm ends up hitting a nerve, or something to a similar effect, and will cause anomolies in the dog's behavior or physiology, such as blindness, seizures, spasms, etc.

Impaired lung, kidney, and liver functions are part of the main payload of the infection, and the dog will gradually show signs of losing its overall health. Early symptoms are exercise related coughing and becoming exhausted easily. Advanced symptoms include extreme weight loss, and fainting, followed ultimately by fatal heart failure.

Treatment of Heartworm Infection

A veterinarian can detect heartworms with very good accuracy with a simple blood test. A positively tested dog will first undergo treatment for the adult worms, typically with an arsenic-based compound, so as to immediately stop the reproduction. Once the adult worms have died, the dog will be assigned a long resting period so that his body can properly absorb and do away with the dead worm debris. Then the microfilariae are dealt with in a subsequent treatment.

In the most unfortunate cases, it might be necessary to have the adult worms surgically removed. Your vet will be able to tell you whether or not simple medication will be enough.

Heartworm Prevention

It is a disease much easier to prevent than to treat, and much cheaper. A typical heartworm prevention regimen will be a simple monthly medication commonly administered in the form of a chewable tablet like Sentinel and will cost about $90 a year.

Prior to putting your dog on heartworm prevention, he must be tested for existing heartworms. Your vet will automatically do this. The reason is if the dog is positive, he may experience dangerous reactions to the preventative medication. This is why missing a dose should require another heartworm test before resuming the preventative medicine in case the dog has acquired heartworms during the margin of time he was unprotected.

Who Should Get Heartworm Protection for Their Dogs?

The heartworm larvae will thrive in temperatures above 50°F where mosquitos exist. As such, there are only a few places in the world where heartworms will not be a problem, e.g., Antarctica, Siberia, etc. Dog owners living in regular climates have the fundamental responsibility of providing their dogs with heartworm protection.

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