Symptoms

For most people, the first symptom they see of Lyme disease is an oval rash at the sight of a tick bite that is called erythema migans.  Although it sometimes will look like the classic bullseye rash that has been ascribed to Lyme disease, more often, it will just be a solid red oval shaped rash.  It typically is not painful or itchy but can get quite large. Erythema migrans is only present at the early stages of disease as it will resolve spontaneously even without treatment.  At this early stage, antibiotics from your primary care doctor will normally clear it up quickly.

How does B. burgdorferi cause erythema migrans?

The center of the rash is where the tick has bitten you, and it goes a bit red like with most insect bites. This is a reaction to the tick bite itself—usually components of the tick saliva.  If you’re unlucky and the tick was carrying the Lyme disease bacteria (called Borrelia), they’ll start swimming away from the site of the bite and your immune cells will start chasing them, causing a growing rash. The rash expands outwards as the bacteria swim out, causing irritation and redness as they go. Eventually (after a week or so) they get so spread out

This swimming is important because it’s how the bacteria spread themselves around the body. The bacteria travel quite fast and some other species can go 100 times their own body length per second. Their body length is only a few thousands of a millimetre though, so you could still outrun one if you had to, but your immune cells cannot keep up with Borrelia, allowing it to escape killing.

Regardless of where the initial infection happens, the bacteria seem to swim to the same few places in the body. They don’t stay in the blood very long but they work their way to joints, muscles, and sometimes the heart or brain. One of the big mysteries of Lyme disease is why the bacteria end up in these particular places. We know some bacteria swim towards food, so it could be that these sites have some nutrient that Borrelia are especially fond of. It might also be that the bacteria do actually get everywhere, but then your immune system can get rid of them from everywhere else – they’re only left in the places that are easy to hide in.

Once they’re there, the bacteria cause the symptoms of Lyme disease. This is probably something to do with the way your body reacts to the presence of the bacteria, but we don’t know exactly. Generally the response to bacteria is to cause inflammation, where the surrounding tissue fills with immune cells and blood – that’s why an inflamed area gets swollen and red. This inflammation helps to get rid of the infection, but can cause problems of its own. You can see this most easily in the joints as arthritis. Elsewhere, inflammation has other effects: bacteria in the heart can cause an abnormal heartbeat, for instance. When they get to the brain, because the brain is in charge of everything else, the problems are quite varied: headaches, signs of meningitis, and memory issues.

As you might have gathered there’s still a lot we don’t know about Lyme disease, including quite fundamental things like why the infection appears where it does. Although we know a lot about the symptoms and the disease, we’re still learning  exactly what the bacteria are doing to cause them.

Early symptoms may appear anywhere from 3 to 30 days after a tick bite.  Symptoms can vary widely and are caused by the body’s immune response to the bacteria.  Approximately 80-90 percent of infected individuals develop a red rash called erythema migrans (EM).  EM begins at the site of the tick bite and expands outward.  This rash is rarely itchy or painful. The classic description is of a “bull’s eye” appearance, however, more commonly, it looks like a solid red oval or circle. In addition to rash, other early symptoms may include fever, chills, headache, and fatigue.  Joint aches and swollen lymph nodes may also be present.

The Lyme bacteria can spread quickly from the site of the original tick bite to involve other sites.  This can happen within days of the original infection.  The most common sites that are involved early include distant skin sites, the heart and the nervous system.  EM lesions at distant sites are typically smaller than the original EM lesion.  Heart symptoms are often not noticed by the patient but can be seen by electrocardiogram.  If severe, inflammation of the heart can cause dizziness or even fainting.  It can rarely even be fatal.  Nervous system symptoms include meningitis or inflammation of the nerves causing weakness.  Most commonly, this involves the facial nerve which can look like Bell’s palsy.