“Do I Really Need to Test for Heartworm?”

We often get asked, “Do I really still need to test for heartworm?” The answer is yes, and here is why. Despite Ontarian’s excellent yearly compliance with providing their dog’s heartworm preventatives, the source of infection remains. It is because of two reasons.

Every year dogs are being adopted and brought here from places like the U.S.A. and Cuba where heartworm is prevalent. It is estimated that Canadian’s adopt tens of thousands of dogs from around the world each year, which means we are also adopting the diseases that come with them (including heartworm).

Wildlife is hosts for heartworm infection as well and for obvious reasons do not receive preventative medications or treatments. It leaves our pets at continued risk of acquiring heartworm.

Heartworm Transmission (courtesy: American Heartworm Society)

Adult female heartworms living in an infected dog, fox, coyote, or wolf produce microscopic baby worms called microfilaria that circulate in the bloodstream. When a mosquito bites and takes a blood meal from an infected animal, it picks up these baby worms, which develop and mature into “infective stage” larvae over 10 to 14 days. When the infected mosquito bites another dog, cat, or susceptible wild animal, the infective larvae are deposited onto the surface of the animal’s skin and enter the new host through the mosquito’s bite wound. Once inside a new host, it takes approximately six months for the larvae to develop into sexually mature adult heartworms.

Heartworm Testing

We recommend what is called a 4Dx Snap Test (run in-clinic or at the laboratory) to be performed each year. Using a small blood sample, it tests for the body’s response to heartworm as well as tick-borne diseases (including Lyme Disease) which if positive, indicates an infection. As the treatment for heartworm disease is different than the prevention, it is important that we rule out a heartworm infection before giving our dogs the monthly medication. While we have confidence in the products that we recommend, much like anything in life, there are no guarantees. We recommend yearly testing to ensure our dogs are safe. Instead of assuming the product has worked 100% and that clients have not given the medication late, missed or late doses, etc. If dogs are left untreated, heartworm infection can cause irreversible heart disease greatly shortening the life of your pet.

As with anything, we are happy to answer any questions or concerns you may have regarding heartworm testing and prevention.

Please feel free to call us at 613-394-4811, or email us at info@hillcrestanimalhospital.ca.

Written by: Sarah Tremblay, RVT