Heartworm disease is a serious disease that results in severe lung disease, heart failure, other organ damage, and death in pets, mainly dogs, cats and ferrets. It is caused by a worm-like parasite called Dirofilaria immitis that are spread from animal to animal from the bite of a mosquito. The adult heartworms live in the heart, lungs and associated blood vessels of an infected animal. The adult heartworms reproduce in the heart and produce microfilaria (immature heartworms) that are transported to other dogs from a mosquito bite. The microfilaria are in the mosquito for a short period of time and then spread to other pets by a bite from the mosquito. The microfilaria then mature, become adults and continue the life cycle.
Heartworm disease is not contagious to other dogs, so a dog cannot catch the disease from being near an infected dog. Heartworm disease is only spread through a bite from a mosquito.
In the United States, heartworm disease has been documented in each of the 50 states, but it is most common along the Atlantic and Gulf coasts from the Gulf of Mexico to New Jersey and along the Mississippi River and its major tributaries.
The most common test that a veterinarian uses to check for heartworms is an antigen test. This blood test detects for specific proteins, called antigens, which are released by the adult female heartworms into the dog’s bloodstream. This antigen test can accurately detect infections with one or more adult female heartworms that are at least seven or eight months old, but it doesn’t detect infections that are less than five months old.
Other tests are available to detect microfilariae in the dog’s bloodstream. Microfilariae in the bloodstream indicate that the dog is infected with adult heartworms. These adult heartworms are producing microfilariae that are circulating in the blood, so when they are found it has been at least 6 or 7 months since the dog was infected.
Dogs older than 6 or 7 months of age must be tested before starting on the heartworm preventitive. A dog may appear healthy on the outside, but on the inside the heartworms may be living and thriving. The heartworm preventitive does not kill the adult heartworms. Also giving the preventative can be harmful and deadly. If the microfilariae are in the bloodstream, the preventative may cause the microfilariae to die and cause a shock-like reaction and possibly cause death in some dogs.
The severity of the disease is directly related to the number of worms that are in the dog. The first clinical sign may be that your dog may tire a lot faster than normal. There may be a cough present with later signs being associated with trouble breathing and heart problems.
If your dog has heartworms, we can treat it. However, we must use an arsenic base product that is not easy on the dog or the owner’s pocketbook. The treatment can be potentially toxic to the dog’s body and can cause serious complications such as life-threatening blood clots to the dog’s lungs. The treatment is expensive and requires multiple visits to your veterinarian.
There are many FDA approved products on the market that prevent heartworm disease. They kill the microfilariae as they are injected into the bloodstream from the mosquito bites. They all require a prescription from your veterinarian. Most are either given orally or topically. Here at the clinic we require that the animal be tested first before we will dispense the heartworm prevention. It is best to keep your dog on preventative year round, but talk to your veterinarian to see what he thinks is best for your dog.