Lyme Disease: What It Is, Borrelia, and How Infection Occurs

On November 1, 1975, two women from the town of Old Lyme contacted the Connecticut Department of Public Health: their children had been diagnosed with juvenile rheumatoid arthritis, and several adults had heard the same diagnosis. An investigation by Allen Steere's team showed that the disease begins after a tick bite; the town's name became the name of the most common disease transmitted by bites.

Lyme Disease: What Kind of Infection It Is

Tick-borne borreliosis, also known as Lyme disease, also known as Lyme borreliosis, is a vector-borne infectious disease caused by spirochetes of the genus Borrelia. "Vector-borne" refers only to the mode of transmission: the pathogen is carried by a blood-sucking arthropod, not by air or household contact. People sometimes mention "the Lyme virus," and this is the first mistake that has to be corrected: the cause of the disease is a bacterium.

Borrelia: The Pathogens and Their Species

In 1982, Willy Burgdorfer first isolated spirochete-like microorganisms of the genus Borrelia from ticks, later named Borrelia burgdorferi. In the United States, this species is most often considered the cause of the disease; in Europe it is associated with the ticks Ixodes ricinus and Ixodes persulcatus, and the genus Borrelia includes several species. The spirochete is extremely small, forms spore forms, and is present in tissues in small numbers, so it is difficult to find. Up to 60% of the Borrelia burgdorferi genome was identified in the remains of Ötzi, who died in the Alps about 5,300 years ago.

How Borrelia Enter the Body After a Tick Bite

Ticks are tiny creatures resembling spiders; they live in forests, in tall grass, and sometimes in city parks. They cannot fly or jump: they cling to the skin of anyone passing by and feed on blood for several days before dropping off. They do not always attach in a visible place — the groin, armpits, skin under the hair. To transmit the bacterium, a tick usually needs to remain on the body for more than 24 hours, and the bite is not necessarily noticeable, so after a walk people check themselves, their children, and their pets.

Stages and Symptoms of Borreliosis

Early manifestations begin 3–30 days after the bite of an infected tick. The best-known sign is a ring-shaped or oval rash around the bite site, erythema migrans: it usually appears after 1–4 weeks, but can also appear after 3 months, lasts several weeks, grows, may be warm, but usually does not hurt or itch. On light skin it is pink or red; on darker skin it is harder to notice, and it resembles a bruise; sometimes the pattern resembles a dartboard. In addition to the rash, the following appear:

• fever, chills, feeling cold;
• headache;
• muscle and joint pain;
• fatigue and loss of energy;
• enlarged lymph nodes.

Without treatment, the infection spreads to the joints, heart, and nervous system: severe headache and neck stiffness, new erythemas on the body, weakness of the facial muscles, arthritis of large joints, heart palpitations, dizziness and shortness of breath, inflammation of the brain and spinal cord, numbness and tingling in the hands and feet.

How the Diagnosis Is Confirmed

Recognizing Lyme disease is not easy: it has much in common with other conditions, and an obvious rash is not always present. The doctor asks about symptoms, noticed bites, and time spent in places where infected ticks live. Two types of blood tests that detect antibodies to the pathogen are helpful. Antibodies appear after several weeks, so testing in the first days may be negative even when the disease is present, and it is repeated. The decision about treatment is made by the doctor: started early, it is more effective.

Possible Complications and When to See a Doctor

Long-term consequences develop after months or years, and their likelihood is higher if treatment is delayed: joint pain and swelling, nervous system disorders in the form of pain or numbness, heart problems, difficulty with memory and concentration. In some people, after treated infection, fatigue, pain, and loss of energy persist for more than six months — this is post-treatment Lyme disease syndrome; the causes are unclear, there is no proven treatment, but most people gradually feel better. A person should see a doctor if there has been a tick bite in the last three months and flu-like symptoms or a round or oval rash have appeared. On darker skin, the rash is harder to recognize.

Lyme disease by itself is not a reason to call an ambulance. Numbers 103 and 112 are for life-threatening conditions, for example signs of a heart attack or stroke.

Everything written here is reference information about the disease and its pathogen, not a remote consultation: the decision about examination after a tick bite is made by a doctor, and no article can replace a conversation with them.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer