Heartworms

Heartworms are spread through the bite of an infected mosquito.

When a mosquito feeds on the blood of an infected dog, the mosquito ingests the microfiliaria ("baby" heartworm) and can then pass the microfilaria on to any other animal it bites.

Once injected into a susceptible dog by the mosquito, the microfilaria mature into adult heartworms and begin producing additional microfilaria, which circulate in the dog's blood.

It takes 3 to 6 months for adult heartworms to develop in a dog after an infected mosquito bites it.

Heartworms can occur in all breeds of dogs. They have been found in dogs of all sizes and ages. Heartworms can occur in short-haired or long-haired dogs and can infect a dog whether it is indoors or outdoors. Whenever a dog is bitten by a mosquito, there is the potential for infection.

Adult heartworms live in the right side of the heart. They are 6-14 inches in length, and several hundred individual heartworms may be present in one dog!

Heartworms impair blood circulation, resulting in damage to the heart, lungs, liver, and kidneys. Serious damage to these organs may occur even before an owner begins to see outward symptoms of heartworm disease.

Signs of heartworm disease include
difficulty breathing,

coughing,

tiring easily,

listlessness,

loss of weight,

a bloated abdomen, and
fainting.

Heartworms are present in both the United States and Canada.

Treatment can be successful, especially when the disease is detected early.

However, heartworms can cause damage to the heart and lungs even before they are detected and treatment is often not without side effects.

Therefore, prevention is recommended because it is safe, effective and easy to use.

HEARTWORMS CAN BE PREVENTED!!!!

Your veterinarian will likely recommend a heartworm test, to make sure you dog is not already harboring heartworms before starting on the heartworm preventive medication.

There are many different heartworm preventive medications available. Common examples are Heartguard Plus, Interceptor and Revolution. Your veterinarian will help you determine which one is best suited for your dog. Most of them, at the current time, are administered on a monthly basis.

Your veterinarian may recommend that your dog receives the heartworm preventive medication all year long, regardless of the climate. There are several reasons for this:

Mosquitoes can survive the winter inside your home. A mosquito which is carrying heartworm disease is as much of a threat to your dog in the winter as in the summer. Only one bite can infect your dog.

Year-round prevention eliminates the possibility of infection during the “off-season”. A year-round prevention program eliminates the possibility of contracting heartworm disease because no “off-season” will exist.

It will be more convenient to “stay on schedule” by giving the medication every month, making it less likely for you to forget to give the medication.

Most of the available heartworm preventatives also aid in the prevention of intestinal parasites, such as roundworms and hookworms, which can be transmitted to your dog at any time of the year.

Year-round prevention provides protection for dogs that travel to warmer climates during the winter, even if they live in an area where mosquitoes are uncommon in the winter months.

Your veterinarian may also recommend periodic blood tests for heartworms for your dog, even if your dog is receiving heartworm preventive medication year-round. Reasons for this include:

The heartworm preventive medication may be vomited or spit out by your dog without your knowledge, thereby, exposing your dog to heartworm disease.

Either by accident or oversight, you may forget to give the monthly preventive for one or more months, leaving your dog exposed to heartworm disease.

None of the routine heartworm tests are able to detect immature or early heartworm infestation. Your dog may have had an undetectable infection at the time of his/her last heartworm test, and therefore, could have a dangerous infection. Heartworm preventives WILL prevent new infections of heartworms, but they CANNOT prevent the progress of pre-existing heartworm infection.

Treatment Of Heartworm Disease:

If your dog has already been diagnosed with heartworm disease by testing testing positive on a blood test for heartworms, you will need to decide whether or not to treat your dog for heartworm disease.

The first step is evaluating the overall physical condition of your dog. In order to do this, your dog's veterinarian will need to do a routine blood screen.

Your dog's veterinarian may also recommend a radiograph (x-ray) of your dog's chest to evaluate the heart and blood vessels, looking for signs of damage to these vessels caused by the heartworms.

Treatment for heartworms involves injections of a drug called Immiticide, which will kill the adult heartworms living within your dog's heart.

There are currently two protocols used for treating with Immiticide:

The first protocol is used only in dogs which are in stable physical condition and showing no outward signs of disease. This protocol involves giving two injections of Immiticide into the lumbar (back) muscles of dog. The injections are given 24 hours apart.

The second protocol involves three injections of Immiticide in the lumbar (back) muscles. The second injection is given 1 month after the first, with the third injection given 24 hours after the second. This method tends to kill the heartworms more slowly, resulting in few complications. Dogs which are already showing signs of disease are likely to require this protocol. Some veterinarians prefer this protocol for all patients.

Concurrent use of anti-inflammatory medications, pain medications and antibiotics (especially doxycycline) may be recommended for your dog also.

The anti-inflammatory medications help to decrease the reaction to the dying heartworms and control complications which can occur as a result.

Pain medications are often used to control the pain involved with giving the Immiticide injections.

Antibiotics (such as doxycycline) are used to control complications caused by Wohlbachia organisms which live inside the heartworms. Wohlbachia are rickettsial organisms (similar to bacteria) which are believed to contribute to the complications which can occur as the heartworms die.

Heartworm preventive medication must also be given to your dog to prevent new heartworm infections. Your veterinarian may recommend starting this medication before treatment or may prefer to wait until after your dog has completed the heartworm treatment.

Heartworm Disease and Ivermectin:

For those dogs which have a positive heartworm test but no signs of disease, using ivermectin monthly is an alternative to heartworm treatment.

However, this medication does not kill adult heartworms. It does seem to shorten their lifespan, and it will keep your dog from getting new heartworms.

Ivermectin will also kill any microfilaria ("baby" heartworms) which are produced. This effectively sterilizes the adult heartworms and keeps your dog from being a source of infection for other dogs.

This may be a viable alternative to you if your dog has heartworm disease and you cannot afford treatment with Immiticide. However, it is important to remember that this medication does not kill the adult worms and your dog may remain positive for heartworms for as long as 2 years. In a 2 year time span, damage caused by heartworms can be significant.

Ivermectin is the active ingredient found in many of the commonly used preventive medications, such as Heartguard Plus.