Q. How do animals get heartwoms?  A. Mosquito bites! 

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 parasitic worm called Dirofilaria immitis. The worms are spread through the bite of a mosquito.

It takes about seven months once a dog is bitten by an infected mosquito for the larvae to mature into adult heartworms. They then lodge in the heart, surrounding blood vessels and begin reproducing.

When a dog is first infected with heartworms, there are no visible or detectable signs. The changes in dogs begin during the final mold of the heartworm larvae; it is then that the mature larvae arrive in the right ventricle and neighboring blood vessels.

Within days, the artery lining is damaged. The body responds by inducing inflammation of the artery, called endarteritis, and other inflammation in the area to try to heal the damage.  Unfortunately, the heartworms cause damage at a rate faster than the body can heal.

Over time, the arteries develop certain characteristics that are typical of heartworm disease; often these changes can be seen  on x-rays. The vessels become tortuous and dilated. Blood clots and aneurysms are a common side effect, and complete blockage of small blood vessels can occur. Due to the inflammation, blood vessel obstruction and fluid accumulation, your pet will begin to cough. They may display exercise intolerance, nosebleeds and shortness of breath, as well as a type of pneumonia secondary to the increase in lung inflammation (called pulmonary essinophillic granulomatosis).

How can you help control mosquitoes?

Aggressive mosquito control is important as an aid in preventing heartworms and additionally in the prevention of other mosquito born diseases. Be sure you do your best to avoid exposure to yourself and your dogs.

Reduce exposure to mosquitoes by avoiding and cleaning up standing water where mosquitoes breed. Remember, even when you don’t see mosquitoes they may be present. Environmental control is always important. Here are some things you can do to help prevent mosquitoes in your area:

  • Reduce exposure to mosquitoes by avoiding and cleaning up standing water where mosquitoes breed. Remember that even when you don’t see mosquitoes they may be present. Environmental control is always important.
  • Keep dogs and cats indoors and protected from mosquitoes during peak mosquito feeding periods around sunrise and sunset.
  • In high mosquito population areas consider screening in exercise areas. This is a common procedure in people’s backyards in much of the Southern states around pools and patios.
  • Be sure all kennels and shelters are protected using a mosquito screen over openings.
  • Citronella spray misters can be used to control mosquitoes safely but the citronella smell can be unpleasant.
  • Consider using systemic or topical mosquito repellents when dogs are outdoors. DEET is extremely effective for humans but is toxic to pets and should not be used on dogs or cats.
  • Permethrin containing topical products are effective and safe in dogs but cannot be applied to cats.

Facts about heartworm disease and prevention:

  • Heartworm disease is caused by a parasitic worm called Dirofilaria immitis, which is transmitted by mosquitoes.
  • Heartworms can grow up to 12 inches long and can live for up to seven years in a dog’s heart, lungs, and blood vessels.
  • Heartworm disease is widespread in the United States and is present in all 50 states.
  • The symptoms of heartworm disease can include coughing, fatigue, weight loss, and difficulty breathing. However, many dogs show no signs of the disease until it has progressed to a severe stage.
  • Treatment for heartworm disease can be costly and risky, and it may not always be successful. Prevention is the best approach to keeping your dog healthy and safe. There are several different heartworm preventatives available on the market, including monthly tablets, topical treatments, and injections. Some of the most commonly used preventatives include:
    • Heartgard: a monthly chewable tablet that prevents heartworm disease and treats roundworm and hookworm infections.
    • Revolution: a monthly topical treatment that prevents heartworm disease and also protects against fleas, ticks, ear mites, and some types of worms.
    • ProHeart: an injectable medication that provides six months of protection against heartworm disease.

Speak with your veterinarian about which heartworm preventative is right for your dog. By taking this important step, you can protect your pet from the serious and potentially deadly consequences of heartworm disease. By protecting your pet, you are also protecting the pets in your community by limiting the spread should a mosquito bite your dog.

If you have any questions or concerns, you should always visit or call your veterinarian — they are your best resource to ensure the health and well-being of your pets.

Also see: Heartworm Disease Facts