Every other Friday on Morning Edition, Outside/In host Sam Evans-Brown tackles a question from a listener.
Gary from Randolph asks: "I was curious as to whether Lyme disease affects wildlife. Do fox, moose, bear and other critters suffer from Lyme disease?"
You may have heard that dogs can get Lyme disease. You may have also heard that cats don’t. What gives?
To sort it all out, I called Dr. Bettina Wagner, a professor of Veterinary medicine at Cornell University. “If we look at cats they can get infected, if we look at cattle they can get infected, if we look at llamas,” she said, “So every single species looked at can be infected.”
So for starters, it’s important to distinguish between creatures that carry the spirochete — the bacteria that causes Lyme disease, Borrelia burgdorferi — in their body, and having a disease. Think for example of the famous case of Typhoid Mary, who never exhibited symptoms but carried the pathogen that causes typhoid.
In other words, medically speaking, we draw a distinction between infection and disease.
But We Know Dogs Get Sick
And we know horses get sick too. Which prompts a question, how do we know?
Dr. Wagner says part of the reason we know is that we’ve done the science here: there have been experiments where dogs have been infected with lyme, treated with various types of antibiotic regimes, and euthanized so that a necropsies can be done looking to see if they can still find live bacteria.
The fact that these studies have been done, which of course ethically you would not be able to do in humans, in fact means we know more about Lyme in dogs than we even do in people.
But another part of this is we live with dogs. We can observe them and tell that, in fact, when they are infected, they start to get sore swollen joints, become sensitive to the touch and may even limp while out on walks. That research may even lead to better Lyme testing for humans.
Obviously we don’t get too much of an opportunity to observe coyotes so closely.
But what about this idea that cats don’t get Lyme? Well, Dr. Wagner said we’re not even 100% sure of that, because cats are just a bit inscrutable. “Is a cat that sleeps all day just old? Or does it have Lyme disease?” she explained.
Lyme Diagnosis Ain’t Easy
In other words, given that many mammals do exhibit symptoms when infected with the Lyme pathogen, we might reasonably expect that other mammals like foxes and coyotes and bears might get sick, but it’s just a hard question to answer.
In fact, even the infamous white-footed mouse — who’s so important to the transmission of the disease — we’re not even sure if they get sick or not. “I don’t know!” says Dr. Wagner, “It would be interesting to ask the mouse population how they feel about the infection.”
And this gets to this broader point, which you might have learned if you had listened to our podcast series put out last August called Patient Zero, even in humans Lyme is a difficult disease to diagnose!
The tests that we have can detect an immune response to the bacteria that causes the disease but can’t be used to definitively diagnose the disease itself. So, doctors make a diagnosis in humans by pairing those immune response tests with a patient’s constellation of clinical symptoms. (Bullseye rash, fever, fatigue, swelling and pain in the joints, for instance) And since some of these symptoms can be shared with other illnesses and are somewhat subjective, the difficulty of making a diagnosis has fueled the fear and uncertainty that surrounds the disease.
So do foxes get Lyme? If you want to know the answer, next time you see one you’ll have to ask if its knees ache.
Sam Evans-Brown, is host of NHPR’s Outside/In which you can subscribe to where-ever you get your podcasts. If you’d like to submit a question you can record it as a voice memo on your smartphone and send it to email@example.com, OR call the hotline, 1-844-GO-OTTER, OR submit it here.