Deer Fences for Prevention of Lyme Disease

Introduction

Transmission of Lyme disease, the most prevalent vector-borne disease in the US, can be strongly discouraged by deer fences.

That’s important for several reasons. First, no vaccine is currently available. Second, the disease (not always curable) can produce a host of severe joint, neurologic and other symptoms. And third, most people are infected not in woods or fields but in their own back yards.

So if one erects a deer-fence around one’s yard that ends the problem. Right? Not exactly. Erecting a deer fence is a key first step, but the picture is more complex. Here’s why:

Deer Ticks and Lyme Disease

Lyme disease, common in the Northeast US as well as in Wisconsin and Minnesota, is caused by a bacterium (usually Borrelia burgdorferi, rarely Borrelia mayonii) that infects deer ticks—ticks that also spread anaplasmosis, babesios, and Powassan disease. But the deer don’t get Lyme disease. They just carry the adult ticks, which get a blood meal from the deer and (if female) drop off and lay thousands of eggs.

It appears that the eggs don’t support the Lyme disease bacteria either. So uninfected ticks hatch out and pick up the bacteria in their early (larval and nymph) stages via blood meals, mostly from the disease’s principal reservoir, the outdoor white-footed mouse, and sometimes from chipmunks, which can also carry the disease. They then infect people or their pets via another bite.

Deer Fences and Ticks

If you protect your yard with a deer fence, that stops the adult ticks from coming in and laying thousands of eggs. But once the fence is erected, some ticks may still remain in the protected zone. And a trickle of ticks may still enter the protected area, mostly on the bodies of small creatures – mostly white-footed mice, chipmunks, and birds -- to which they have attached.

Hence, besides installing a deer fence it’s important to take secondary measures. Specifically, treat the protected area with a tick-killing spray containing an active ingredient like cedar oil that is safe for both pets and people. Repeat such spraying occasionally to deal with the occasional tick brought in from outside the fence. And, at least equally important, make a point of removing leaf litter, brush piles, low-lying tree branches, and tall grasses from your yard, because these can harbor small animals -- notably white-footed mice and chipmunks.

Taking these steps in the indicated order, whether or not they eliminate the problem in your yard altogether, should vastly reduce the risk of Lyme disease transmission.