Estimation of the seroprevalence of Borrelia infection in the Isère department based on data from city medical laboratories from 2013 to 2020 ; Estimation de la séroprévalence de l’infection par le genre Borrelia dans le département de l’Isère à partir des données issues des laboratoires de biologie médicale de ville de 2013 à 2020

Lyme borreliosis is a bacterial vector-borne infection transmitted by ticks of the genus Ixodes, the germ of which is a bacterium of the genus Borrelia. It is the most common tick-borne disease in France and is present throughout the country, although there is a wide geographical disparity. The most affected regions are the east and center of the country (Alsace-Lorraine, Franche-Comté, Rhône-Alpes and Limousin regions). According to estimates from the Sentinel Network, the annual incidence of Lyme borreliosis in France from 2009 to 2015 remained stable at 45 cases/100,000 inhabitants before increasing from 2016 to 2019 to 83 cases/100,000 inhabitants. We wanted to estimate the seroprevalence in the Isère department and its evolution from 2013 to 2020 by using the results of Lyme serologies performed in city medical laboratories. The data collected from Oriade-Noviale and Eurofins laboratories allowed us to determine the seroprevalence in the Isère department and its evolution from 2015 to 2020 (the seroprevalences of 2013-2014 were not interpretable). Thus, it was possible to observe a peak in seroprevalence in 2015 at 5.9% which then decreased in 2016 to 5.2%, before reaching a plateau around 4.4% for the years 2017 to 2020. An association between male gender and positive status could be observed for each age group analyzed and for each year. Similarly, an increase in seroprevalence with age was observed, with two peaks of unequal size: one between 10-15 years and the other around the age of 70. A significant territorial heterogeneity could also be observed in our study. Indeed, seroprevalence was on average lower (around 3.5%) in geographical areas 6, 9, 10 and 11, whereas seroprevalence was almost twice as high in geographical areas 7, 8, 12 and 13. Data collected from laboratories for geographic areas 1-5 were partial and therefore should be treated with caution. A complementary study evaluating the reason for prescribing these Lyme serologies in the city by physicians could be an interesting addition to ...