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Lyme, Mice, and Why 2017 May Be a Bad Year For the Disease

As anyone who lives in certain areas of the US can tell you, Lyme disease is a particularly big problem every summer. Lyme is a bacterial infection transmitted by ticks, and it can affect different parts of the body in different and significant ways; the symptoms can vary widely from one patient to the next. It’s also a disease that we’ve been hearing more and more about, as the past 20 years have seen a substantial increase in the number of Lyme disease cases.

Unfortunately for people who live in Lyme-affected areas of the US, researchers predict that the summer of 2017 will be an especially bad one for the tick-borne disease. The reason may come as a surprise, and frankly, it’s a little gross: mice.

The Mouse-Lyme Connection

Felicia Keesing and Rick Ostfeld, ecologists at Bard College and the Cary Institute of Ecosystem Studies, respectively, say that a mouse infestation one year can lead to an explosion in Lyme cases the following year. The couple has been studying the causes and effects of Lyme for over two decades, and last summer, their Hudson Valley home was hit with a particularly bad mouse infestation. It was indicative of a problem throughout the region, but what’s the connection?

Basically, where the mice are, the ticks follow. The mice transmit Lyme to ticks, and ticks, in turn, transmit it to humans. Ostfeld explains, “An individual mouse might have 50, 60, even 100 ticks covering its ears and face.” What’s more, he explains, mice pass Lyme onto the overwhelming majority of ticks that feed on them — as many as 95% of them. Consequently, last summer’s mouse problem will, if Keesing and Ostfeld’s prediction is correct, turn into this summer’s Lyme epidemic.

The Spread of Lyme

Since the 1980s, Lyme has gone from a little known disease affecting a small number of people to a much more widespread problem. In the early 1980s, Lyme was found in two specific areas of the US: western Wisconsin, and a small area from southern New England to northern New Jersey. In the early 1990s, it had spread somewhat, and there were about 10,000 new cases of it each year in the US.

Today, however, Lyme has exploded. It’s found in 260 counties in 14 states, from coastal maine to the southern Mid-Atlantic states, and also in a swatch from the southern tip of Lake Michigan to eastern Minnesota, with a few small clusters on the West Coast. The total number of new cases is now up to around 300,000 each year. According to Centers for Disease Control and Prevention epidemiologist Kiersten Kugeler, “Lyme disease is quite a big public health problem.”

Why Now?

The question of Lyme’s timing is a difficult one to answer because there are several possible explanations. Climate change may play a part, for sure. Perhaps more likely is the increase in the number of deer on the east coast, deer carry deer ticks, the particular species that spreads Lyme in the eastern US.

A more likely culprit, however is the Hudson Valley’s history of deforestation and more recent reforestation. A brief summary: when the area was settled in earnest by Europeans, more than 200 years ago, many of the trees were cut down. Wood was needed for building things like ships and structures, and the land needed to be clear to settlers could raise crops and livestock. However, conservation efforts in recent decades has brought a lot of those forested areas back, but they’re not exactly as they once were. Now, they’re clusters of wooded areas broken up by residential areas — just the type of environment that suits mice the best because it has everything they need and not a lot of predators like hawks and foxes.

It’s a perfect storm that leads to a population explosion in mice. Where they mice are, the ticks follow. Ticks pick up Lyme from the mice, and then spread it to humans who are out enjoying the region’s beautiful natural surroundings and increasingly building their homes near these newly reforested areas. In fact, according to Kugeler, most people who get Lyme actually get it at home.

Protecting Yourself From Lyme

There are several things you can do to reduce your chances of getting Lyme. For starters, do a tick check every day. Their small size (just a millimeter or two) makes them tough to spot, so you do have to be vigilant. They tend to favor the warmer parts of the body, so check in the armpits, the groin, and all over your scalp, especially behind your ears.

If you do find a tick, remove it as quickly as possible using a pair of tweezers. The sooner you get it off, the lower your chances of getting Lyme, since it takes a tick approximately a full day to infect you with the Lyme bacteria.

Then, be on the lookout for symptoms of Lyme, whether you’ve removed a tick or not. That last part is important, as according to ILADS (or the International Lyme and Associated Diseases Society), fewer than half of the people who get Lyme remember being bitten by a tick. Symptoms include a rash, typically shaped like a bullseye around the bite, plus fever, headache, and arthritic joints. If you’ve been bitten by a tick or suspect that you may have Lyme, see your doctor immediately for treatment. A full recovery from Lyme is possible when it’s caught early and treated properly.

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