How Mice are Responsible for the Spread of Lyme Disease

When you hear talk of Lyme disease, the first thing that pops into your heads is most likely going to be ticks. With the recent upswing in confirmed cases of Lyme disease in Ontario, there has been plenty of information available on this topic. Most of which points the finger at ticks. although the only way people contract the bacteria responsible for Lyme disease (bacterium Borrelia burgdorferi) is through a tick bite; mice actually play a bigger role in the spread of the disease.

However, if you dig a little deeper, you will discover that mice actually play an integral part in the spread of this bacteria. Yet another reason to want to rid your property and home of these pests.

 How Lyme Disease Spreads

Cases of Lyme disease in Canada have been on the rise steadily the past several years. Historically this disease was found in the southern parts of the U.S. However, with the advent of climate change, we are seeing cases appear in new regions each year. The exponential growth and migration north of the bacteria was also helped along by an unusually large corn harvest in 2016. This allowed the sustenance required to reproduce at a much higher rate. A perfect storm if you will. 

The bacteria is transmitted by black-legged ticks (also known as deer ticks). These hard-bodied biting arachnids attach themselves to deer, rodents, and birds mostly. They require a steady source of fresh blood and typically need to be attached for at least 24 hours to transmit the disease. The bacteria needs to work its way from its guts, through its saliva, and into the other animal’s bloodstream. This is a timely process. So check yourself and your pets regularly if you are outdoors in affected areas.

Through birds longer travel trajectories the bacteria can cover greater distances more efficiently, but it is through rodents that the disease reaches larger numbers. More on that in a bit.

The key takeaways here are that in Ontario, this a very recent issue we have to contend with. And as the climate continues to change, the further north this bacteria will move and be infecting greater numbers of animals and humans along the way. 

The Role Mice Play

It’s not a stretch to say that mice are the single most important link in the chain that allows this disease to spread. Here’s how it works: adult ticks generally feed off white-tailed deer, after they have finished, they will fall off the deer onto the forest floor. At this point in their lifecycle adult ticks lay their eggs, which also happens on the forest floor. The following year these eggs will hatch into larvae. At this point they are harmless. The larvae are not yet infected with the bacteria.

This is where the mice come in. The most accessible source of nourishment for the larvae are mice and in endemic areas, up to 90% of the mice are infected. The larvae only become infected once it feeds of an infected host. The mice population in the wild is unimaginably large, and as such,  they play the single most important role in the spread and growth of Lyme disease.

Once again, if you live in affected areas inspect yourself and your pets regularly. It does take 24 hours for the disease to be transmitted.  Please see the map below for affected areas in Ontario:

What You Can Do

For obvious reasons, you will want to keep mice out of your home. If you suspect you have any wildlife accessing the interior of your home, contact your local wildlife professional immediately. 

As for what you can do to help with the spread of Lyme disease in your area; there are these items called Tick Tubes (this link will teach you how to make them).  How they work is these tubes are stuffed with a poison-laced material that mice like to use to make their nests. Ticks, in turn, love reproducing and living in mice nests. These tubes are placed around your property and the mice will eventually take the poison-laced material back to their nest.

The substance is called permethrin and is harmless to mice, but will kill the local tick population. 

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