The Low Down on Heartworm and Tick Prevention

Quick Summary on Heartworm

Heartworm is a parasite that is transmitted by mosquitos. A mosquito feeds on an infected animal and will pick up microfilaria (baby worms). These worms will mature into an infective stage in the mosquito. When the infected mosquito bites another dog or cat, the larvae enter the new host’s bloodstream. It takes approximately 6 months for the larvae to mature into adult worms.

Heartworm season in Ontario starts in the spring and runs through the fall.

We recommend heartworm tests in all of our canine patients. We start testing mid-April, approximately 6 months after the season ends.  Heartworm testing ensures your pet is not suffering from a heartworm infection

We recommend all dogs and outdoor cats are on heartworm prevention, normally from June to November.

Quick Summary on Ticks

Ticks are becoming more endemic in Ontario. The areas they frequent the most are long grassy regions and forests. Ticks attach to our pets, feed for a few days and detach once fed. The risk with ticks is that they can spread disease when feeding. A growing concern in Ontario is Lyme disease. It is spread by the deer tick. They will feed on an infected animal and can transmit the bacteria to your pet if they feed on them.

Ticks prefer more temperate weather. They come out when it’s about 5 °C – 20 °C.  They tend to stay on tall grasses; it puts them at a good advantage to attaching themselves to an animal passing by.

Tick season is more variable as it depends on the temperature. Generally, we need to start thinking about tick prevention in March/April. This can vary based on the areas your pet frequents. If July and August are very hot months (above 25 °C), then tick prevention may not be required. The fall months are also very important to maintain your tick prevention.

Based on your pet’s lifestyle and the areas they frequent it may be recommended to keep your pet on tick prevention.

Heartworm Prevention

There are multiple products available for your pet. Most products have combined prevention against multiple parasites.

Advantage Multi is our primary recommended heartworm prevention. It is a topical medication that is applied ONCE monthly on the skin. It protects against heartworm, fleas, mites, lungworm, roundworm, hookworm, and whipworm. We generally start June 1st to November 1st

If you have questions about other products (oral medications, or other topical), please feel free to contact us.

Tick Prevention

There are multiple tick products available for our dogs, both oral and topical.

Advantix is our primary topical tick prevention product. It is applied on the skin (along with the neck and back) ONCE monthly. 95% of ticks will die as soon as they are in contact with the skin. The other 5% may feed but will die quickly. This product also protects against fleas. When the medication is applied, your dog should be separated from your cat for approximately 12 hours. PLEASE NOTE, this product is toxic to cats. The medication is only toxic when wet and if your cat ingests it. We recommend applying the medication at night and keeping your cat separate from your dog overnight. We normally start this medication in March/April (based on their lifestyle) and continue to the fall.

There are oral products available as well if you would like more information on these products, please feel free to contact us.

DUO Pack: Advantage Multi and Advantix

If you have both the Advantage Multi and the Advantix, it is recommended to apply them at different times.

For example, start applying the Advantix on the 15th of every month. Generally, we will start Advantix BEFORE starting Advantage Multi. As mentioned earlier, the tick season starts earlier than heartworm. The Advantage Multi can be applied the 1st every month starting in June.

If you have any questions about this please don’t hesitate to contact us.


Written by Coxwell Animal Clinic