Approximately 15% of the world’s population has been infected with Lyme disease at least once

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This is the conclusion of a meta-analysis based on nearly 90 scientific studies addressing infection rates in Borrelia burgdorferiThe type of bacteria causing the disease. The researchers who performed this analysis reported a global seroprevalence of 14.5%. They also paint the “typical” profile of the individuals most susceptible.

Lyme disease mainly occurs in the northern hemisphere, but it also affects certain areas of the southern hemisphere. expression Borrelia burgdorferi It actually identifies two entities of bacteria: species Borrelia burgdorferi in the narrow sense،, a bacterial complex of about thirty species, of which at least four are responsible for Lyme disease, is called Borrelia burgdorferi sensu lato. The disease is transmitted to humans by the bite of an infected tick – more precisely by species Ixodes ricinus in Europe.

The most common clinical manifestation of Lyme disease is erythema migrans (redness that gradually spreads in a circle from the site of the bite). The infection can then affect other tissues and organs, resulting in disorders of the joints, nervous system, or skin. To better understand the global epidemiology of this disease over the past decades, a team from the Institute of Tropical Medicine at Kunming Medical University, China, examined its seroprevalence and sociodemographic characteristics.

Central Europe is the most affected region

As part of their analysis, they sifted through many sources of scientific studies, such as PubMedAnd the Base where web of science, to collect all searches including the keywords “Borrelia burgdorferi sensu lato” and “infection rate”. Of the 4,196 studies that were extracted, 89 were selected for inclusion in the meta-analysis (involving more than 158,000 individuals in total). After a careful reading of this research, it appears that the global seroprevalence of infection with Borrelia burgdorferi sensu lato It is 14.5%.

This is the most comprehensive and up-to-date systematic review of the global seroprevalence of Borrelia burgdorferi sensu lato. Not surprisingly, some regions are affected more than others, with Central Europe at the fore, with a prevalence of 20.7%. It is followed by East Asia (15.9%) and Western Europe (13.5%). The regions least affected are the Caribbean and Australia, where the seropositivity rate is 2% and 4.1%.

Most of the serological findings were confirmed by Western blot — a laboratory method used to detect specific molecules among a mixture of molecules, the team says. This study also revealed that this method gives much more reliable results than a simple serological test.

Prevalence of IgG antibody and IgM antibody specific against Borrelia burgdorferi sensu lato Among the studies reporting seropositivity confirmed by Western blot (WB), versus seropositivity not confirmed by WB. © Y. Dong et al.

The 58 studies that used WB confirmation to determine seropositivity in Borrelia burgdorferi sensu lato Then they were used to analyze predictive factors for infection. These studies were conducted in 28 countries and were published between 1999 and 2021.

Factors associated with increased seropositivity are: age (individuals over 50 years of age are most affected), gender (men are more affected, as they are more likely than women to be at risk), and place of residence (rural areas are more affected). leads to the presence of ticks) and, obviously, the fact of suffering from tick bites. The seropositivity rate for people considered to be at high risk (farmers, workers, police, military and anyone in regular contact with host animals) is 14.7%, while the rate for the general population is 5.7%.

growing prevalence

The team also noted that the spread of infection with Borrelia burgdorferi sensu lato It was higher after 2011: the seropositivity rate decreased from 8.1% (during 2001-2010) to 12.2% (during 2011-2021). ” This may be related to environmental changes and human factors, such as longer summers and warmer winters, changes in rainfall during the drier months, migration of animals, the fragmentation of arable land and forest cover due to human activities and the spread of outdoor activities ‘, explained the researchers.

Estimation of the seroprevalence of Borrelia burgdorferi sensu lato in different population groups in the reported countries. The darker the color, the greater the seroprevalence; Gray areas represent countries that reported no seroprevalence. (a) the general population, (b) the high-risk population, (c) the population infected with tick bites, (d) the population with Lyme disease-like symptoms. © Y. Dong et al.

Since its identification in 1975, Lyme disease has become the most common zoonosis transmitted by ticks in the world. Specifically, the infection is often asymptomatic, but it can sometimes cause very debilitating symptoms, such as joint pain or partial paralysis of the limbs. When the disease is diagnosed early, treatment with antibiotics is sufficient to stop the infection. Without any treatment, disorders can appear for months or even several years after the bite.

Ticks live in wooded and damp areas (mats of dead leaves, brush, etc.), tall meadow grasses, parks and woodlands or urban parks. In France, human infections are most common between the beginning of spring and the end of autumn, which corresponds to the period of maximum activity of these mites. Ticks attached to the skin should be removed as soon as possible, because the risk of contamination increases with the duration of contact. After removing the tick and disinfecting the area, it is recommended to monitor the bite site for a month.

Source: Y. Dong et al., BMJ Global Health

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