What Every Pet Owner Needs to Know About Heartworm

The term ‘heartworm’ just makes me squirm in my seat. Luckily the positivity rate for heartworm in dogs in Ontario is quite low in comparison to the number of dogs there are.  From 2012—2017 two veterinary labs in Ontario saw an average of 225 cases per year.

Nonetheless, heartworm is extremely serious and can be life threatening.  The topic is worth taking a deeper dive into so here are 5 things that every pet owner should know about heartworm.

1. Mosquitos transmit heartworm
   Mosquitos can carry an organism called Dirofilaria immitis, meaning the larvae of heartworm. The larvae is placed inside your dog’s skin after a mosquito bite. The worms move from the skin tissues to the bloodstream after maturing over 50-70 days.  They then move to the blood vessels in the lungs, where they become fully mature.  The larvae move from eggs, to juveniles, then to full mature adults after a process between 6-9 months.
2. The symptoms of heartworm in dogs:
   -Dry, persistent cough
   -Lethargy – loss of interest in walks or being active
   -Weight loss/lack of interest in food
   -Difficulty breathing
   -Bulging ribs from a build-up of fluid in the lungs

3. Heartworm treatment
   Treatment can be complicated, depending on the severity of the heartworms in your dog. The treatment can be very harsh on the dog as well.  Injections of a drug can be given to kill heartworms. This is a very strong drug so must be monitored and the dog is ordered to rest during this long process. Some dogs may need antibiotics, pain medications, special diets and heart medications, sometimes for the remainder of their lives.
4. How to test for heartworm
   Blood tests are used to test for heartworm in dogs. There are 2 different things to look for in the bloodstream:
   Heartworm Proteins: An antigen test is used to detect these. These heartworm proteins are released by female heartworms into the bloodstream.
   Microfilariae: Only adult heartworms can mate and produce microfilariae, so this is an indicator of heartworm in a dog.
5. Heartworm prevention
   The best treatment for heartworm is prevention! There are a few preventative measures you can take.  Products can be administered monthly to a dog either as a topical liquid or an oral tablet. There is also another option to inject a product under the skin every 6 – 12 months.