How heartworm is contracted and spread -
 
 

Heartworm is transmitted via an infected mosquito, a dog cannot get heartworm from being in the presence of a dog who does have it. It is always passed via a mosquito who bites an infected animal then another animal.   Due to this heartworm cases are much more prevalent in areas where there is an abundance of mosquitos.  Our area is extremely prone to mosquitos and therefore heartworm infections.  Our rescue treated a dozen cases last year - that was approximately 25% of our rescued dogs.

The Infection - When a mosquito bites an infected animal, the larvae (microfilariae) of a heartworm is introduced into the mosquito.  During the next 28 days, the microfilariae molt within the mosquito and enter the third larval stage.  Then when a mosquito bites the dog, this larva is injected into the dog’s skin.  After this initial bite, it takes approximately 6 months for the larvae to turn into adult heartworms and be present in the heart and lung vessels.  This is what the test given by your vet is testing for.  So your dog would need to have been infected 6 months prior to the vet visit to show  positive on a heartworm test.

These adult heartworms obstruct blood flow and elicit an inflammatory response in the lungs of the dog that can result in significant damage to the heart and lungs.  If you were to see a dog in the advanced stages of heartworm, just walking across a room can cause breathing normally caused by running several miles.

Once the adult heartworms are hosting in your dog, they produce more baby heartworms (microfilaria) which circulate in the dog’s bloodstream – which can now be picked up by a hungry mosquito to be passed to yet another dog.

The treatment for heartworms -
 

First and foremost, most cases of heartworms are treatable.  Only the severe cases that have effected more organs than the heart and lungs are not.  If your dog tests heartworm positive, your vet should be able to determine if treatment is an option.  Treatment consists of two injections of immitricide in the lumbar region of the dog's back.  These injections kill the adult heartworms in the dog's organs.  The dog stays at the veterinarian hospital to be given these injections as only one injection can be given per day.  The dog is also awake for these injections.

The dog then has to be leash walked with no sudden movements for 6 weeks.  It is extremely important that the dog is kept from any exercise - no running, no jumping, etc.  This is because a sudden movement can separate an adult heartworm in pieces which can then cause a clot in the heart - killing the dog.  Also, the injections cause the adult heartworms to move from the heart to the lungs.  Here is where they die and must over time dissolve.  Thus, the dog doesn't have the same lung capacity until the heartworms dissolve and the body disposes of them.  After the 6 weeks the dog returns to the vet for a dose of liquid ivermectin.  This can be given by mouth or in a vaccine.  This dose of ivermectin kills the baby heartworms floating in the bloodstream.  The dog can now return to a normal activity level.

30 days after the liquid ivermectin the dog should start receiving a monthly heartworm preventative.
6 months after the adult heartworm injection treatment, you should retest your dog for heartworms.   If the dog shows up negative, any type of preventative medication can be utilized -  daily, monthly or 6 months.

Preventative medications -
 

Prevention – Our area calls for dogs to be taking heartworm preventative medications year round.  Today there are several types of heartworm preventatives – daily, monthly and 6 month.  Administration of these drugs must be diligent.  Dogs should be tested prior to taking heartworm medications as giving heartworm medications to an infected dog can be dangerous to their health.  What preventative you choose depends on your lifestyle – THAT you choose one can save your dog’s life.