It has been known for some time that Lyme disease is on the rise. But we did not know exactly how often the disease occurs. A new study is changing that. And the results are startling.

This is how the research – published in the magazine BMJ Global Health – found that at least 1 in 7 people worldwide have antibodies against the bacteria that cause Lyme disease. The researchers reached that conclusion after looking at data from 89 studies, in which more than 158,000 people took part. An analysis of the collected data subsequently showed that about 14.5 percent of the persons studied had antibodies against Borrelia burgdorferic sensu lato (see box). It indicates that an equally large percentage of people are (have been) infected by this bacterium – which is transmitted to humans by ticks – and therefore have (had) Lyme disease among its members.

Borrelia burgdorferic sensu lato
Sensu lato is a Latin term that is best translated as ‘in a broad sense’ and that you come across regularly in taxonomy. In the case of B. burgdorferi, the Latin phrase indicates that we are not talking about one bacterium, but about several genospecies. When we talk about the Borrelia bacteria that cause Lyme disease, there are at least three. Namely: B. burgdorferi sensu stricto (or B. burgdorferi in the strict sense, in this case the species name refers to one specific bacterial species that can cause Lyme disease), B. afzelii and B. garinii. In the Netherlands it is mainly the latter two species that occur, while in the US, for example, B. burgdorferi sensu stricto occurs. In short: Lyme disease is therefore caused by different bacterial species that are often grouped under one heading – namely B. burgdorferi – out of convenience. In the remainder of this article, we will also refer to the different genotypes underlying Lyme disease in this way.

From tick to human

When sign on B. burgdorferic If they are infected and bite people and then eat a blood meal, they can also transmit the bacteria to their host, causing it to develop Lyme disease. When people contract the bacteria, they can develop flu-like symptoms, such as fever, muscle and joint pain. Antibiotics can be used to prevent worse; without the use of antibiotics, the bacterium can spread to various organs and ultimately cause much more serious complaints through damage to the nervous system or the heart.

Regional differences

Lyme disease has been on the rise in recent years. But exactly how often the disease occurs is unclear. We also do not have a good idea of ​​the risk factors, ie which characteristics increase the chance that people will contract the disease. Scientists are trying to change that in the new research. First of all, they show that a remarkably large part of the world population – based on their data, about 1 in 7 people worldwide – have antibodies against B. burgdorferic to own. However, if we zoom in on a regional level, major differences emerge. For example, the bacteria – again based on the antibodies found – appear to strike most often in Central Europe. About 20.7 percent of people have antibodies against it B. burgdorferic† That percentage is also quite high in East Asia at 15.9 percent. Just like in Western and Eastern Europe, where respectively 13.5 and 10.4 percent of the people studied have antibodies against the bacteria. The percentage of people with antibodies against B. burgdorferic in South Asia (3 percent) and Oceania (nearly 5.5 percent).

Bacteria is advancing

Furthermore, the research also shows that the Lyme bacteria are striking more and more. “Our results indicate that B. burgdorferic occurred more frequently between 2010 and 2021 than between 2001 and 2010,” this is how the researchers write† “That may be related to ecological changes and anthropogenic factors, such as longer summers and warmer winters, changes in precipitation during dry months, animal migration, fragmentation of cropland and forests, and frequency of outdoor activities.”

Risk Factors

In addition, the study also provides more insight into risk factors. For example, the study shows that the chance that people will have antibodies to B. burgdorferic possess, increase with age (50+), are male, live in the countryside and have been bitten by a tick. However, more research is needed to verify these conclusions. The next step could be to warn people more specifically about Lyme disease.

“Lyme disease is a widespread infectious disease,” the researchers conclude. “But has not received much attention worldwide.” They hope that their study will change that. The ultimate goal, of course, is to reduce the disease.

Lyme disease in the Netherlands
According to the RIVM, 1 million people are bitten by a tick every year in the Netherlands. About 2 in 100 people contract Lyme disease this way. This concerns 27,000 patients per year. Their complaints vary widely; most people develop a ring or spot that is characteristic of Lyme disease at the site of the tick bite, and about 1200 to 1500 people develop joint, skin and nerve complaints and sometimes heart complaints. Of the 27,000 people who contract Lyme disease every year, an estimated 1,000 to 2,500 per year continue to struggle with long-term complaints. The number of pathogenic tick bites is also increasing in the Netherlands. For example, the number of people who visit their GP after a tick bite with a red ring or spot on the skin has more than quadrupled between 1994 and 2017.