How to Get Rid of Heart Worms

Heartworms are parasites that literally strike fear in the hearts of mammals, particularly cats, dogs and even humans. These roundworms got their name by growing in the hearts of their hosts. They may stay there for several years, especially if the victim is less active and often lethargic.


If left untreated, these thread-like worms could grow up to 10 inches in length and cause fatal consequences. Heartworms go through several life stages before they turn into adults and suck the life out of your pet. Here’s how the infection evolves from a tiny mosquito bite to a life-threatening virus.

  • Transmission. Heartworms do not lay eggs. They produce thousands of little worms called microfilariae every day through live birth. These tiny organisms wait up to two years inside a mosquito before being transferred to an uninfected host.
  • Ecdysis. The microfilariae enter their new host through a mosquito bite. Then, they evolve and molt to the next larval stage at the point of entry.
  • Migration. After molting, the little roundworms make their way into your pet’s chest and abdomen and transform into an immature adult 45 to 60 days after the infection. Then, they enter the bloodstream and stay in the pulmonary artery after 30 to 60 more days.
  • Reproduction. Over the next three to four months, the adult worms are now about 20 to 30 cm in length and ready to mate. Afterwards, the adult females start producing microfilariae and begin the entire process once again.
  • Prepatent Period. This is the entire maturation stage of six to seven months, when the worms grow into adults and start spreading the disease.

When the destructive parasites are fully grown, they block blood circulation in the different chambers of the heart and large vessels near the lungs. As a result, the heart’s right ventricle and the large pulmonary artery leading to the lungs become enlarged as the worms take up all the space inside. Meanwhile, your little furry friend is losing appetite and weight, becoming listless as each day passes.


Heartworm infection is difficult to detect in animals with a sedentary lifestyle. The classic symptoms are more pronounced in active pets. In severe cases, dogs cough often, wear down easily, accumulate fluid in their abdomen, lose consciousness and eventually die from congestive heart failure. As for felines, they experience diarrhea, vomiting, blindness, coughing, drowsiness, anorexia, rapid heartbeats, syncope and sudden death.

There are several types of tests available to verify if the animal has microfilariae or not.

  • Direct Blood Smear. This manual procedure involves searching for microfilariae in the blood using an old-fashioned microscope.
  • Knott’s Test. This more advanced test rotates the blood in high speeds using a centrifuge to detect microfilariae in the blood.
  • Difil Test. Similar to the Knott’s test, this one concentrates the blood on a filter and uses Difil stain to break it down to find those little worms.
  • Antigen Testing. Using genetic engineering, this test identifies antigens or proteins that stimulate the generation of antibodies against heartworms in the bloodstream.
  • Antibody Testing. This immunological test overcomes the inability of antigen tests to detect male worms by focusing on the host’s immune response against the parasite.
  • X-rays. The pulmonary arteries are enlarged to confirm whether heartworms are present, although this procedure is more effective with cats than with dogs.
  • Echocardiography. This noninvasive procedure uses an ultrasound on the heart, though it is extremely difficult to use on the extremities of the pulmonary arteries.
  • Angiocardiography. This basically uses an x-ray machine to locate the worms after contrasting fluid is injected to the heart.


Eliminating heartworms in dogs has been easier and more successful compared to infection in other animals. Before a treatment can be prescribed, your pet needs to be evaluated first to determine potential risks. However, it becomes risky to get rid of these slimy dependents when the infection is already severe.

The objective is not just to expunge the bloodsuckers, but to do it with minimum complications and side effects. Patients with evidence of more severe heartworm disease may be healed successfully, but the possibility of complications and mortality is greater. By having your domesticated creatures checked up regularly, you prevent the disease from worsening. Here are some of the common treatments against heartworms used by veterinarians today.

  • Microfilariae Annihilation. Prioritize the elimination of the microfilariae before the worms become adults. If you went straight to the adult parasites, you risk blocking your pet’s arteries with their remains, which could induce massive complications. Additionally, the big worms would only be replaced by their babies, making the procedure useless.

It is best to give your cat or dog a monthly dose of an anti-parasitic drug that prevents heartworm, such as Heartgard or Triheart. If you want faster results, you could opt for milbemycin-based medication, such as Sentinel and Interceptor. They work like ivermectins, only more potent. However, they might cause shock to your pets if large numbers of microfilariae die at the same time.

Remember that you still need to wipe out the present adult worms, even after this preventative measure is complete. Administer the medication regularly about three months before treating the adult worms. After all, the big kahunas cause the disease, not their immature offspring.

  • Adulticide Therapy. Once you decimate the kids, the next step is to go after the adults. The only product available so far against full-grown heartworms is melarsomine dihydrochloride or Immiticide. Three doses of this drug is the safest option to take because the shock is less severe. Additionally, the gradual kill lessens the threat of clogging the animal’s arteries and blood vessels.

Compared to the old arsenic compound, Caparsolate, Immiticide has been found to be very effective and less risky. It is administered through a deep and painful intramuscular injection into your pet’s lower back muscles. The soreness resulting from this procedure may require pain relievers, but be careful because your pet might bite.

It is common to give the host two doses each day for two days. After the treatment, confine your feline or canine friend for a month of complete rest so their system can absorb the dead worms. Keeping them active during this time might transport the floating remains to the lungs and cause death.

  • Surgery. When all else fails, it is best to consult a vet for a more effective solution. This involves several tests to determine whether the patient should really have surgery. This is a very delicate procedure, but perhaps your only option if your pet’s condition isn’t improving.

Heartworms are a very common, but extremely serious disease that no pet owner should ignore. If you truly love your pet, the best way to show it is by never breaking its heart, literally and figuratively.

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Nicole Harding

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