Internal Parasite Prevention Month: Heartworms

You may be thinking that heartworm season for our pets isn't for a few months still, and what are those crazy people at Central Veterinary Services doing talking about these creatures in January? Well, January is Internal Parasite Prevention Month so we figured we would share a bit about some common internal parasites that are found in Manitoba!

If there is anything us Manitobans know best it is how mosquitoes can sure suck the fun out of summer, and while these bloodthirsty insects can drive humans away from hitting the beach and attending backyard barbecues they also pose a potentially fatal problem for our dogs, cats and ferrets.

The mosquito plays a crucial role in the heartworm life cycle, and soon you'll understand why. Adult female heartworms living in an infected dog, coyote, fox, raccoon, or wolf produce microscopic worms known as microfilariae which circulate in the infected animals bloodstream. When a mosquito takes a blood meal from an infected host it also picks up these microfilariae. The microfilariae then molt into their "infective stage" within the mosquito (this takes ~10-14 days). Then when the mosquito carrying the "infective stage" larvae takes a blood meal from an unsuspecting dog, cat, or other susceptible host the larvae of the heartworm enter through the bite location. Once within their new host it takes the larvae up to 6 months to molt into adult heartworms. 

Heartworms are long, slender parasites. As adults they are found in the right ventricle of the heart, and in the pulmonary artery where they can obstruct blood vasculature. The classic symptoms of a pet who has adult heartworms include decreased exercise tolerance, right-sided heart enlargement, and fluid accumulation in the abdomen. These common symptoms are caused by the reduced blood flow on the right side of the heart, but these symptoms do not appear until the heartworms are well-established. 

 Image from www.valleydaleanimalclinic.com

Image from www.valleydaleanimalclinic.com

The earlier this disease is detected, the better the chances the pet will recover. There are few, if any, early signs of canine heartworm disease, and this is why us at Central Veterinary Services recommend annual testing for all of our canine patients prior to starting a preventative medication in the spring (~May 30th). This test (known as the 4Dx Snap Test by IDEXX) is run in clinic, and requires a very small blood sample. If a test that takes a small blood sample, and only 8 mins wasn't neat enough — this test also checks your pets blood for Lyme disease, Anaplasmosis and Ehrlichiosis (which are diseases that can be transmitted by ticks — thats a BONUS)! If this test shows up positive other tests may be recommended by your veterinarian to check the stage of the disease. Depending on the stage of the disease the treatment may differ.

Feline heartworm disease is known to be much more dangerous than its canine counterpart for two reasons. First, diagnosis is difficult and findings may be inconsistent. A cat with heartworm disease may present with signs of respiratory distress (due to worms/larvae in the pulmonary arteries), but test negative on the antigen and antibody tests we have in clinic. Chemistry blood panels, and radiographs of the chest may also be inconclusive. Second, there is no approved treatment for feline heartworm disease, therefore the only way to protect our cats from heartworm disease is to have them yearly on heartworm prevention (this includes indoor cats since mosquitoes do get inside the house). Ask you veterinarian at your cats next appointment about how affordable prevention is!

Due to the strength of the medications needed, treatment of canine heartworm disease is usually not the cheapest. This is why prevention is a much better option for pet owners! Central Veterinary Services offers a few options for heartworm prevention — ask your veterinarian at your next appointment which one would be recommended for your pet. Heartworm prevention medications are highly effective, but it is still recommended that your dog or cat be tested annually incase a dose is missed, or given late. Even if you give the medication to your pet at the appropriate time, he or she could spit it out, vomit it up, or even rub off the topical medication without you knowing therefore causing it to be ineffective. Testing is the only way to know for sure if your pet needs treatment for heartworm disease.

Isolated and rare cases of human heartworm infection have been reported, however, the heartworm is generally not considered a risk to human health. 

If you have any questions about heartworm disease, or any other internal parasites don't hesitate to call us at 204-275-2038. One of our Veterinarians, or Registered Veterinary Technologists would be happy to assist you. 

Resources:

  • https://www.heartwormsociety.org/pet-owner-resources/heartworm-basics 
  • http://www.petsandparasites.org/dog-owners/heartworms/