Lyme disease
Lyme disease is an infectious disease caused by the Borrelia burgdorferi bacterium. This bacterium is primarily transmitted by the sheep tick (Ixodes ricinus). Medical literature also describes transmission during pregnancy from mother to child (1), through blood transfusion, breast milk (2), mosquitoes, fleas, and even semen (yes, Borrelia is the little sister of syphilis).
Spread of the Bacteria
Ticks thrive in humid environments, living in shrubs and grass up to about 1.50 meters high. In the Netherlands, they are active from March to November. High-risk groups for tick bites include children and those who spend a lot of time in nature, such as campers and forestry workers. The risk of exposure to this bacterium varies by region and depends on tick density and the prevalence of infected rodents. Transmission of Borrelia burgdorferi from tick to human can, in rare cases, occur shortly after the bite but becomes more likely after attachment for more than 36 to 48 hours.
Incidence and Estimates
In the Netherlands, approximately one in five ticks carries the Borrelia burgdorferi bacterium. Although the likelihood of a tick bite is relatively high, not every bite leads to an infection. According to a small Dutch study (3), there is a 2–3% chance of contracting an infection after a (contaminated) tick bite. These figures are based on detecting a red ring or antibodies by a general practitioner within three months of the bite. However, if the same individuals were re-examined five or ten years after the infection, the percentage of people with ongoing symptoms or infection would likely be much higher. Lyme disease often develops slowly, with symptoms frequently emerging years after the initial exposure.
The characteristic erythema migrans (EM)—a red ring at the site of infection—occurs in only 25–50% of infected individuals. It presents as a red or blue-red patch that gradually enlarges within days to two or three months after the tick bite.
According to RIVM (2017) data, approximately 1.5 million tick bites are reported annually in the Netherlands, resulting in about 27,000 new cases of Lyme disease. This figure is likely an underestimation, as not all cases are accurately identified or documented. The Dutch Lyme Disease Foundation points out several overlooked factors: the red ring (EM) does not always appear or is not noticed and reported to a doctor; general practitioners (GPs) may fail to (correctly) recognize EM or other Lyme symptoms; other symptoms may not be linked to the infection and thus go unreported; Lyme testing may not be conducted, or test results may yield false negatives. Including these cases would provide a more accurate estimate of the annual number of new patients.
Symptoms and Disease Progression
The progression of Lyme disease varies greatly between individuals and can manifest in different ways. Some people develop symptoms shortly after the tick bite, while others experience issues years later, often triggered by a stressful event or weakened immune system. Early symptoms may include flu-like complaints such as headache, fever, muscle aches, and fatigue. If accompanied by a red ring, the connection between symptoms and the tick bite is clear, and conventional doctors are likely to recognize it. Testing is not required in such cases, and treatment can begin immediately.
The disease usually progresses slowly. Depending on the type of bacteria and the host's immune response, various complaints can arise, including neurological, dermatological, rheumatological, cardiological, and even psychological issues.
The method of transmission also plays a role. Tick saliva contains substances that suppress the immune system, benefiting both the tick and the bacterium.
Tip
If you find a tick attached to your body, remove it carefully and place it in a glass container. Should you later develop vague symptoms, send the tick to a laboratory. This will quickly identify any pathogens it carried, making it easier to determine the necessary treatment. Pathogens are often easier to detect in ticks than in the human body.
Trevisan G., (2022). Case Report: Lyme Borreliosis and Pregnancy - Our Experience. Front Med (Lausanne). 2022 Mar 28;9: 816868. doi: 10.3389/fmed.2022.816868. PMID: 35419384; PMCID: PMC8996379.
Schmidt BL, Aberer E, Stockenhuber C, Klade H, Breier F, Luger A. Detection of Borrelia burgdorferi DNA by polymerase chain reaction in the urine and breast milk of patients with Lyme borreliosis. Diagn Microbiol Infect Dis. 1995 Mar;21(3):121-8. doi: 10.1016/0732-8893(95)00027-8. PMID: 7648832.
Hofhuis, A., Herremans, T., Notermans, D. W., Sprong, H., Fonville, M., van der Giessen, J. W., & van Pelt, W. (2013). A prospective study among patients presenting at the general practitioner with a tick bite or erythema migrans in The Netherlands. PloS one, 8(5), e64361.