# Seroprevalence of tick-borne infections in blood donors in Europe: a systematic review

## TL;DR

This study reviews the prevalence of tick-borne infections in European blood donors, highlighting the risk to blood safety and the need for improved detection methods.

## Contribution

The study provides the first comprehensive systematic review of tick-borne infection seroprevalence in European blood donors from 2000 to 2024.

## Key findings

- Eleven tick-borne pathogens were detected in blood donors, with some showing seroprevalence rates over 20%.
- Most studies used antibody detection, but Nucleic Acid Amplification Testing is recommended for better risk assessment.
- The review emphasizes the need for broader research on tick-borne pathogens to improve transfusion safety.

## Abstract

Tick-borne infections (TBIs) pose an increasing threat to public health and recent research shows a wide range of infections transmitted to humans by tick bite. This situation may have an impact on blood safety in the context of transfusion-transmitted TBIs. We aimed to assess the seroprevalence of TBIs in blood donors in Europe in the period 2000 to 2024.

This systematic review followed PRISMA guidelines. We searched PubMed, Embase, MEDLINE, Scopus, CINAHL, and national reporting systems up to April 2024 using keywords related to TBIs, Europe and epidemiology. Two reviewers independently screened and selected studies, focusing on seroprevalence of TBIs in European blood donors from 2000 to 2024. Data extraction and risk of bias assessment were performed.

The search yielded 5304 articles, of which 56 met the inclusion criteria. We added one article after citation search. The included studies encompassed 19 European countries and 11 different TBIs. The most studied pathogen was Borrelia spp. The majority of studies used antibody detection as a diagnostic technique. The highest seroprevalence rates were observed for Tick-Borne Encephalitis Virus (TBEV), Bartonella spp., Rickettsia spp. and Borrelia spp. with pathogen seropositivity rates, in some studies, of over 20 % depending on the pathogen and the vaccination status of included individuals.

This study highlights the need to focus on a wider range of tick-borne pathogens to better understand the epidemiological landscape of TBIs. Additionally, incorporating Nucleic Acid Amplification Testing of donated blood will improve the ability to differentiate between past exposure and potential infectivity, to allow for an improved assessment of TBI transmission risk in transfusion medicine.

•Serological and molecular evidence of 11 tick-borne infections has been detected in blood donors' sera in Europe.•Several tick-borne pathogens demonstrated significant seroprevalences of over 20 %.•The majority of studies used antibody detection as a diagnostic technique.•Need for a broader research focus on a wider range of tick-borne pathogens.•Incorporating Nucleic Acid Amplification Testing allows for the detection of pathogen presence with potential infectivity.

Serological and molecular evidence of 11 tick-borne infections has been detected in blood donors' sera in Europe.

Several tick-borne pathogens demonstrated significant seroprevalences of over 20 %.

The majority of studies used antibody detection as a diagnostic technique.

Need for a broader research focus on a wider range of tick-borne pathogens.

Incorporating Nucleic Acid Amplification Testing allows for the detection of pathogen presence with potential infectivity.