A groundbreaking analysis has revealed that more than 14% of the world’s population has or has previously had tick-borne Lyme disease.
Researchers have performed a pooled data analysis of available evidence, identifying that based on the presence of antibodies in the blood, around 14% of people globally have contracted tick-borne Lyme disease at some point in their lifetime.
The analysis, published in the open access journal BMJ Global Health, suggests that tick-borne Lyme disease is most prevalent in Central and Western Europe and Eastern Asia, with men over 50 who live in rural areas being most at risk.
What is tick-borne Lyme disease?
Tick-borne Lyme disease – otherwise known as Borrelia burgdorferi sensu lato (Bb) infection – is the most common form of tick-borne infection. Only mosquitos are more notorious than ticks for carrying harmful microbes.
Lyme disease is characterised by redness and swelling at the site of the tick bite, and the infecting agent can spread to tissues and organs throughout the body, affecting the nervous system, joints, heart, and skin. Despite tick-borne Lyme disease being a global health threat, its true prevalence and specific risk factors were unknown.
Mapping the global burden of Lyme disease
To illustrate a more comprehensive picture of the disease, the team analysed research databases and reviewed 137 eligible studies from a pool of 4,196. The researchers then pooled the data from 89 studies that comprised 158,287 people. The pooled data analysis illuminated that the estimated overall global seroprevalence, which is the presence of antibodies to Bb infection in the blood, was 14.5%.
The areas where seroprevalence was highest were Central Europe (21%), Eastern Asia (16%), and Western Europe (13.5%). In contrast, the regions with the lowest seroprevalence were the Caribbean (2%), Southern Asia (3%), and Oceania (nearly 5.5%).
The reported pooled Bb seroprevalence in studies that employed an analytical technique known as Western blotting, which can accurately confirm the presence of specific proteins, was lower than that in studies using other confirmatory methods. Due to this, the researchers suggest that widespread use of Western blotting could optimise the accuracy of Bb antibody detection.
Subsequently, the team examined the results of 58 studies that used Western blotting, discovering that being male, over the age of 50, living in a rural area, and being bitten by a tick were all linked to an increased risk of Bb antibodies.
The researchers explained: “Our results indicate that the prevalence of Bb in 2010–2021 was higher than that in 2001–2010.”
The team hypothesised that the increase in tick-borne Lyme disease might be due to ecological changes and factors such as longer summers, warmer winters, lower rainfall, animal migration, fragmentation of arable land, and more time spent outdoors with pets.
The team explained that a potential imitation of their investigation was a lack of long-term studies and that it was impossible to systematically assess whether Bb antibody positivity had a long-term effect on the risk of developing Lyme disease or the risk of recurrence. Moreover, the studies included in the analysis varied considerably, and most of the reports lacked vital information, such as the exact definitions of high-risk groups.
The researchers concluded: “The reported estimated global Bb seropositivity is relatively high. Lyme disease is a widely distributed infectious disease, but it has not received much attention worldwide. A more accurate picture of its global distribution and who is most at risk of infection could inform the development of public health response policies and Lyme disease control programmes.”