Borrelia, antibodies

Borreliosis, or Lyme disease, is caused by a bacterium spread by ticks. This species of bacteria is known as borrelia burgdorferi. Not all ticks carry these bacteria, so not all tick bites cause an infection. Small rodents are the actual source of borrelia in the wild.

An estimated 500,000 Finns are bitten by ticks every year. If the tick carries the bacteria in its gut, it is transmitted to the human in 2 out of 3 cases. An estimated 6,000 people are infected per year, and 50–80% of them develop symptoms. Approximately 1/50 to 1/100 of the cases result in borreliosis. Antibody studies suggest that approximately 2% of Finns have been infected at some point.

When the bacteria end up in the body, the cells of the immune system begin to develop antibodies to the bacteria. This takes approximately 2–4 weeks from infection. The test measures these antibodies, called immunoglobulin M (BorrAbM) and immunoglobulin G (BorrAbG).

The disease got its other name from the town of Lyme in the United States, where the disease was described for the first time in 1975.

When should borreliosis be tested for?

The antibody test can indicate whether the subject has had borreliosis. In other words, the test is used to find the body’s response to the potential bacteria, not the bacterium itself. The test cannot be used in the initial phases of a tick bite.

The most common first symptom of borreliosis is a circular rash at the site of the tick bite, known as erythema migrans. When the bacteria spread to other organs via the bloodstream, it can result in arthritis, meningitis or facial nerve paralysis.

Symptoms can also include headaches, concentration and memory problems, fatigue, joint or muscle pain, dizziness, sweating and low blood pressure. Antibiotic treatment is started in the early phase of the disease based solely on the skin lesion.

At this point, the antibodies are often still negative. In a later phase of the disease, the test is usually positive.

What does the test measure?

The test measures two antibodies to borreliosis: immunoglobulin M (BorrAbM) and immunoglobulin G (BorrAbG).

Immunoglobulin M antibodies occur in the blood 2–4 weeks after infection and can remain elevated for a few months. The existence of immunoglobulin M antibodies indicates a recent infection.

Immuniglobulin G antibodies occur in the blood 4–6 weeks after infection and can remain elevated for years after the infection.