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Heartworm Infection

Heartworms are parasites transmitted by mosquito bites. These parasites take up residence in both the dog’s lungs and chambers of the heart and can live for over five years. Treatment for heartworms is very difficult for a dog and is not always successful, so prevention of heartworms is important.


Heartworm disease is caused by a roundworm known as Dirofilaria immitis. The adult female worm can be 9 to 16 inches long! There are over 70 species of mosquitoes that carry these heartworm larvae from an infected animal to a new animal host. Once in the new host, these parasites begin to grow into adult worms living in the blood vessels that support the canine’s lungs and heart placing a tremendous amount of stress on those organs. The growing inflammation results in severe complications depending on the amount of worms and how quickly the treatment kills the heartworms. Since the majority of larvae in the blood vessels develop into adult worms, dogs can be infected again and again.


The severity of heartworm infection depends on four things:

  1. Number of worms present;
  2. The immune system of the infected dog;
  3. Duration of the infection; and
  4. Activity level of the dog.

If all the heartworms are not killed from treatment and medication, the constant irritations they inflict lead to permanent scarring and reduced flexibility of the heart valves and infected blood vessels.  Small dogs do not tolerate heartworm infections or the treatments as well as large dogs.  This is due to the fact that small dogs have smaller heart chambers and blood vessels so they can only tolerate fewer worms and much less damage. 


SYMPTOMS: The severity of the symptoms depends largely on the affected canine’s activity level and the length of the infection; however, common signs of heartworm infection include:

  1. Coughing;
  2. Trouble breathing;
  3. Intolerant to exercise or walking;
  4. Lethargy;
  5. Discoloration of the skin – often blue or purple in color;
  6. Weight loss;
  7. Edema (fluid accumulation in the lower legs)
  8. Vision problems;
  9. Fainting;
  10. Nosebleeds; and
  11. Swelling of the abdomen.


Dogs that are sedentary show very few signs or possibly none at all; whereas active dogs like hunters or performance dogs show more dramatic signs of infection.  Most veterinarians use the antigen detection test to verify infection of heartworms – it is considered to be the most sensitive method available; blood tests and chest x-rays may also be used to diagnose heartworm infections in the canine.   





Year-round prevention is recommended by most veterinarians including The Companion Animal Parasite Council who are experts in parasitology and veterinary medicine.  No one knows when and where mosquitoes will be present, so your canine should get an annual heartworm check.  Most heartworm medications will also treat intestinal parasites that can also be transmitted throughout the year. 



However, once your dog has been infected with heartworms, your veterinarian will need to select the most appropriate and effective treatment. The best treatment for your canine will depend on several factors including if there are any other ongoing medical issues. 


The only drug available to kill heartworms is an arsenic compound given in a 2-dose or 3-dose protocol intravenously in the dog’s back, alternating sides between treatments.  Some dogs experience pain, swelling and soreness with movement or in rare instances, an abscess at the injection site. 


The 2-dose protocol is done 24 hours apart while the 3-dose treatment involves an initial injection followed by 2 more injections one month later, again 24 hours apart.  Many veterinarians prefer the 3-dose method because it is safer for the dog and more efficient in killing all parasites and the heartworms. 


Once the heartworms are dead, they can still cause some respiratory problems, especially if it is difficult to keep the dog quiet and inactive.  These respiratory problems can last for a few days to a few weeks.  Some canines experience coughing, spitting up blood, rapid or labored breathing, fatigue and fever.  Oxygen and anti-inflammatory drugs usually work well to alleviate these problems within 24 hours after treatment. However, the key is to keep the dog confined in a calm environment during the entire process as much as possible. Some dogs may need to be hospitalized.  Once effectively treated, the dog should be placed on heartworm preventative and tested after six months to make sure all the heartworms were killed.  If they do test positive for heartworm again, another round of treatment may be necessary. 


PREVENTION: There are several medications that are both safe and effective in preventing heartworm infection in your canine. Treatment should begin at 6-8 weeks of age. In dogs older than 6 months, it is necessary to do an antigen test to make sure they are not already infected before starting a preventative program; they should then be retested 6 months later to ensure the dog is not infected with heartworms.


When administering monthly heartworm medication, the most important factor is to do it the same time each month for continuous protection.  If a dosage is forgotten, it can have serious consequences for your dog.  Post a calendar on the refrigerator to mark the dates each month.  If a dosage is missed, call your veterinarian immediately for their recommendation on what to do next. Your dog depends on you to kill the life cycle of the heartworm.



Integrative Medicine



Not all animals can use all natural remedies; allergic reactions to oils and/or herbs and digestive problems are possible. A natural remedy is not a substitute for veterinary care.


Once your dog has been infected with heartworm, there are no Integrative Medicines solutions to manage or eradicate the infection. Only your veterinarian can provide the best and proper treatment for your infected dog. Once the infection is eradicated, integrative medicine can help with problems from any permanent heart damage.

There are herbal repellents that can help prevent your beloved friend from being bit by the mosquitoes that may be carrying the heartworm infection. Heartworm infections are best dealt with preventatively – avoid mosquito ridden areas and give your dog monthly heartworm medication year-round.


Heartworm Infections
– Canine Products to Help Heart Damage–
(Please note: These products below do NOT treat the heartworm infection, just the damage from the infection.)

(Reference: Veterinarians’ Desk Reference)

(Live Link)






Cats: ½ capsule sid
Dogs: 1 capsule/25 lb sid

Improves myocardial function; hawthorn may or may not be appropriate for cats with hypertrophic cardiomyopathy.


1 capsule per 20 lb bid or 1 scoop per 20 lb bid

Supports a calm nervous system.


Dogs: 1 capsule/25 lbs sid or bid (during therapy if needed)

Supports the liver, helps detoxification pathways.


Cats: 2 capsules sid
Small dogs: 1 capsule/10 lb bid

Supports the liver; help detoxification; contains anti-inflammatory CurcuVET.



Cats: ¼ tablet, sid
Dogs: ¼-1 tablet bid

Combination of antioxidants and herbs support liver function; contribute to the formation and use of superoxide dismutase.

Small Animal Antioxidant12

Cats: 1 capsule sid
Dogs: 2 capsules/25 lb sid

Antioxidants to reduce damage to heart.

Super EPAVET12

Cats: 1 gelcaps sid
Dogs: 2 gelcaps/25 lb sid

Anti-inflammatory; may help heal endothelial damaged by heartworms; may contribute anticoagulatory function to help prevent heartworm embolism after treatment.


To help you quickly find the right Integrative Medicine formulas and manufacturers to help treat your dogs, cats and horses, please refer to the Veterinarians’ Desk Reference
(Click Here)



March 2011(Always consult with your veterinarian to properly diagnose any health problems. Misdiagnosis and/or mistreatment -- including OTC and/or homeopathic products -- can lead to dangerous complications.)



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