Apr 23 2015

Heartworm, fleas and ticks … Oh my! – Is your pet protected?

Spring is in the air! The sun is (somewhat) shining and we all couldn’t be happier to arise from our cold weather hibernations and habits. Now that the temperatures are changing it’s time to face reality – creepy crawly season is back and it’s time to get your pet protected!


heartworm_2009Heartworm disease is spread through mosquitos. For us in Ontario, this is a concern throughout the summer
months and why we use prevention from June through to November. The lifecycle of the heartworm begins when a female mosquito bites an infected dog and ingests the microfilariae (consider them the baby heartworms) during a blood meal. The microfilariae develop further for 10 – 30 days in the mosquito’s gut and then enter its mouthparts. At this stage, they are infective larvae and can complete their maturation when they enter a dog. The infective larvae enter the dog’s body when the mosquito bites a dog. They migrate into the bloodstream and move to the heart and adjacent blood vessels, maturing to adults, mating and reproducing microfilariae within 6 – 7 months.


Heartworm Testing

Here at the Usher Animal Hospital, we test all dogs for heartworm disease prior to starting them on any sort of preventative. As long as compliance has been met giving the medication for the required amount of time (typically June – November), we do not require subsequent testing to be done.

Heartworm testing requires a small blood sample be taken with one of our technicians. The sample is sent out to our reference laboratory and results are reported by next day. Our heartworm tests not only screen for heartworm disease, but we also screen for common tick-borne diseases as well.



Fleas can be a year-round issue, depending on where you live. However, in Ontario the summer tends to be our typical flea season.  There are four stages to the flea lifecycle:

Flea eggs are whitish and about 0.5 millimeter (mm) (1/32″) in length. They are unlikely to be seen without a magnifying glass. Adult fleas lay eggs after taking a blood meal. The eggs are initially laid on the dog’s skin but fall off into the environment to continue their life cycle. Flea eggs constitute approximately 50% of the total flea population. Eggs may hatch in as little as 14 to 28 days, depending on environmental conditions. High humidity and temperature favor rapid hatching.

Flea larvae are about 2-5 mm (1/8″ to 1/4″) in length. They have a whitish body and a black head. They feed on organic debris found in their environment and on adult flea feces. They dislike bright light and move deep into carpet fibers or under furniture, organic debris, grass, branches, leaves and soil. Flea larvae prefer warm, dark and moist areas. Outdoors, larval flea_controldevelopment occurs only in shaded, moist areas where flea infested pets spend a significant amount of time. Our climate-controlled homes offer an ideal environment for the flea larvae to thrive.

The flea pupae produce a protective silk-like cocoon that is sticky. It quickly becomes coated with grime and debris, which acts as a useful camouflage. With warmth and humidity, pupae become adult fleas in 5-10 days. The adults do not emerge from the cocoon unless stimulated by physical pressure, vibrations, carbon dioxide or heat. This is important since once fleas emerge from the cocoon they can only exist for a few days unless they are able to feed. Pre-emergent adult fleas can survive within the cocoon for up to 9 months. During this time they are resistant to insecticides applied to the environment. This is important to remember because adult fleas may emerge from their pupae into the environment a considerable time after you apply insecticides in your home.

Once it emerges, the flea adult, unlike the larvae, is attracted to light and heads to the surface in order to encounter a passing host to feed upon. Two days after the first blood meal, female fleas begin egg production. In normal circumstances the adult female will live up to three weeks, laying approximately 40 eggs per day. The entire life cycle, from egg to adult flea can be completed in as little as 14-28 days depending on environmental conditions.



Ticks are not only a concern in the four-legged community but for us as humans as well. We are all fully aware of Lyme disease and the health concerns involved.

The tick lifecycle involves four distinct life stages: egg, six-legged larvae, eight-legged nymph and adult. Females deposit from 3,000 to 6,000 eggs on the ground. Adult ticks seek host animals and after engorgement on blood, they quickly mate. Male ticks usually die after mating with one or more females, although some may continue to live for several months. Females die soon after laying their eggs in protected habitats on the ground. The life cycle requires from as little as 2 months to more than 2 years, depending on the species. After the egg hatches, the tiny larva (sometimes called a “seed tick”) feeds on an appropriate host. The larva then develops (“molts”) into the larger nymph. The nymph feeds on a host and then molts into an even larger adult. Male and female adults feed and mate on the host; the female falls to the ground to lay her eggs, continuing the life cycle. 


Parasite Prevention

Here at the Usher Animal Hospital, we provide an abundance of heartworm, flea and tick preventative medications. Which product you choose will all depend on the lifestyle of your individual pet and their risk factors. Most pets that stay within the City of Toronto use a heartworm and flea combination product as Ticks aren’t as prevalent within the city itself. Pets that travel to northern parts of Ontario and visit cottages will often use a preventative that takes care of heartworm, fleas and ticks since the prevalence is much higher.

Products we carry:

Topical Oral
Revolution (dogs and cats) – Heartworm, flea, intestinal parasites, mites and some ticks Heartgard (dogs only) – heartworm, intestinal parasites
Advantage Multi (dogs and cats) – Heartworm, flea, intestinal parasites, mites and some ticks Trifexis (dogs only) – heartworm, fleas, intestinal parasites.
Advantix (dogs ONLY*) – tick and fleas*Not to be used on cats or around cats Nexgard (dogs only) – flea and tick
Advantage (dogs and cats) – fleas


If you are confused about which product would be right for your pet, please do not hesitate to contact us and we’d be happy to discuss your options.



  1. Heartworm Disease: https://www.usheranimalhospital.com/pet-health-resources/pet-health-articles/articles/?rid=773
  2. Fleas: https://www.usheranimalhospital.com/pet-health-resources/pet-health-articles/articles/?rid=763
  3. Ticks: https://www.usheranimalhospital.com/pet-health-resources/pet-health-articles/articles/?rid=725


usherahadmin | Uncategorized

2 thoughts on “Heartworm, fleas and ticks … Oh my! – Is your pet protected?”

  1. Jenn says:

    My outdoor cat stays close to home in my backyard in downtown Toronto. What months should I apply a spot-on treatment like Revolution?

    1. usherahadmin says:

      Revolution should be applied monthly June to November in most situations.

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**Please note the hospital is CLOSED EVERY TUESDAY BETWEEN 12:30pm and 1:30pm for staff training**
After Hours: Please contact the Veterinary Emergency Clinic at 416-920-2002. They are located at 920 Yonge St. with the entrance off of McMurrich St.