A Practical Guide to Ticks in London

Previously, ticks that carried Lyme Disease occasionally appeared in London in association with migrating birds. Prior to 2016, tick encounters were rare in Ontario and isolated to a few specific locations.


Within the last 4 years, ticks have become increasingly common in Ontario. The two most common ticks that we will encounter in London are:

  • Dermacentor variabilis (aka American dog tick; wood tick)

  • Ixodes scapularis (aka deer tick; blacklegged tick)


These ticks will feed on mammals and birds but will have preferences at different life stages. They cannot jump or fly. Ticks 'quest' by climbing up vegetation and grabbing or falling onto a passing host.


The most common tick (of any species) for us to find on a pet is a female tick as these are the ticks that engorge significantly when feeding, and therefore, are the largest and easiest to see.


MYTH: The biggest risk for Lyme disease occurs in long grasses.


In fact, deer ticks (Ixodes scapularis) are most commonly found under leaf litter as they prefer the moist environment. As soon as the temperature rises to 4 degrees Celsius or greater, the deer ticks are ready and waiting to grab an unsuspecting host. Keep in mind that the greatest danger for deer ticks lies in wooded areas.


In contrast, American dog ticks (Dermacentor variabilis) are more common in fields and long grasses, yet they do not typically carry Lyme Disease (although they can carry other diseases such as tick paralysis).

Adult American dog ticks are most active in mid-summer.

Deer Tick
Deer ticks in various stages of engorgement. The scutum appears so small in comparison to the body!

The easiest way to tell the difference between the 2 ticks is to look at the small 'armoured plate' (the scutum) on the back of the tick. In the deer tick, the scutum is a solid-coloured, dark brownish-black. It is known as inornate or 'plain'. The mouthparts or palps are long.

American Dog Ticks

Conversely, the American dog tick has a fancy, ornate scutum of mottled black and yellowish-white, and its palps are short.


Given the fact that the ticks you will see in London will be either of these 2 varieties, the easiest way to identify the tick is to ignore the engorged body (which can range from grey to brown), and concentrate on the scutum:


Is it ornate? Then it's an American dog tick. Or is it inornate? Then it's a deer tick.


On a very engorged tick, the scutum will appear very small, and you may need to use a magnifying glass.

Watch out for this tick if you love steak!

An unusual tick called the Lone Star tick (Amblyomma americanum) has made rare appearances in Southwestern Ontario. The tick is aptly named for the white spot (“star”) on its scutum. Lone Star ticks are not native to Ontario, and we suspect that they have fallen off migratory birds. 


In addition to having the potential to cause disease in pets, these ticks are remarkably significant to human health in that a bite from a Lone Star tick can cause an allergy to red meat to develop in a human. This allergic reaction to a carbohydrate in red meat may cause symptoms such as hives, vomiting and diarrhea, abdominal pain, and even a life-threatening anaphylactic shock. There is no known cure – other than avoiding red meat!

Interestingly enough, a Lone Star tick was discovered on a cat in London, Ontario in June 2019.

Lone Star Tick
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