Exposure to tick-borne encephalitis virus among nature management workers in the Netherlands

Exposure, infection and disease with the tick-borne pathogen Borrelia miyamotoi in the Netherlands and Sweden, 2007-2019

Using a novel multi-antigen protein array and diagnostic algorithm the exposure, infection, and disease caused by the emerging tick-borne pathogen Borrelia miyamotoi was investigated in the Netherlands and Sweden throughout different populations at risk of tick-bites over the past decades. ABSTRACT: The impact of the emerging tick-borne pathogen Borrelia miyamotoi is not fully understood. We utilized a protein array to investigate B. miyamotoi seroreactivity in various human populations in the Netherlands and Sweden. The IgM/IgG seroprevalence in Dutch healthy (2·5%, 95%CI 1·5-4·1) and population controls (2·0%, 95%CI 0·9-4·4) was lower (p=0·01 and p=0·01) compared to the tick-bite cohort (6·1%, 95%CI 3·9-9·5). In accordance, the Swedish healthy controls (1·0%, 95%CI 0·1-6·9) revealed a lower (p=0·005 and p<0·001) IgM/IgG seroprevalence compared to the tick-bite (8·9%, 95%CI 5·7-13·7) and fever after tick-bite cohort (16·5%, 95%CI 10·6-24·8). Altogether, 15 of 2,175 individuals had serologic evidence of early B. miyamotoi infection. The risk of infection with B. miyamotoi was 0·7% (95%CI 0·3-1·4) in tick-bitten individuals, and of disease 7·3% (95%CI 2·6-12·8) in those with a febrile illness after tick-bite. Our findings provide insights into the risk of infection and disease with this pathogen in Europe.

Seropositivity to tick-borne pathogens in nature management workers in the Netherlands

The incidence of tick-borne infections other than Lyme borreliosis and tick-borne encephalitis is rising in Europe, including the Netherlands. Nature management workers, being highly exposed to ticks, serve as valuable sentinels for seroprevalence studies on tick-borne pathogens (TBPs). This study assessed nature management workers' seropositivity to TBPs including Anaplasma phagocytophilum, Babesia divergens, B. microti, Borrelia burgdorferi s.l., Rickettsia conorii and R. typhi in the Netherlands. In addition, the study examined coexposure to multiple TBPs and identified risk factors for B. burgdorferi s.l.- and A. phagocytophilum-seropositivity. The study included 525 nature management workers who donated serum and completed a questionnaire. Sera were analysed for exposure to A. phagocytophilum, B. divergens, B. microti, R. conorii and R. typhi using immunofluorescence assays. For B. burgdorferi s.l. antibody detection, the recommended two-tier testing strategy was used. Risk factor analysis was performed using logistic regression modelling. Seropositivity was 30.9 % for B. burgdorferi s.l.; 16.4 % for A. phagocytophilum; 6.5 % for R. conorii; 2.3 % for R. typhi; 4.2 % for B. divergens; and 0.4 % for B. microti. Almost half (49.3 %) of the participants demonstrated seropositivity for one or more pathogens. Risk factors for B. burgdorferi s.l.-seropositivity included being male, increasing age and tick bite frequency. For A. phagocytophilum-seropositivity, increasing age and working in North Holland province were significant risk factors. This study illustrates the exposure to TBPs in the Netherlands, emphasizing the need for ongoing vigilance and international collaborations to better understand and address the growing threat of TBPs in regions with demonstrated environmental TBP circulation.

Gender and sex differences in occupation-specific infectious diseases: a systematic review

Occupational infectious disease risks between men and women have often been attributed to the gendered distribution of the labour force, with limited comparative research on occupation-specific infectious disease risks. The objective of this study was to compare infectious disease risks within the same occupations by gender. A systematic review of peer-reviewed studies published between 2016 and 2021 was undertaken. To be included, studies were required to report infectious disease risks for men, women or non-binary people within the same occupation. The included studies were appraised for methodological quality. A post hoc power calculation was also conducted. 63 studies were included in the systematic review. Among high-quality studies with statistical power (9/63), there was evidence of a higher hepatitis risk for men than for women among patient-facing healthcare workers (HCWs) and a higher parasitic infection risk for men than for women among farmers (one study each). The rest of the high-quality studies (7/63) reported no difference between men and women, including for COVID-19 risk among patient-facing HCWs and physicians, hepatitis risk among swine workers, influenza risk among poultry workers, tuberculosis risk among livestock workers and toxoplasmosis risk among abattoir workers. The findings suggest that occupational infectious disease risks are similarly experienced for men and women within the same occupation with a few exceptions showing a higher risk for men. Future studies examining gender/sex differences in occupational infectious diseases need to ensure adequate sampling by gender.

Multiplex Serology for Sensitive and Specific Flavivirus IgG Detection: Addition of Envelope Protein Domain III to NS1 Increases Sensitivity for Tick-Borne Encephalitis Virus IgG Detection

Tick-borne encephalitis is a vaccine-preventable disease of concern for public health in large parts of Europe, with EU notification rates increasing since 2018. It is caused by the orthoflavivirus tick-borne encephalitis virus (TBEV) and a diagnosis of infection is mainly based on serology due to its short viremic phase, often before symptom onset. The interpretation of TBEV serology is hampered by a history of orthoflavivirus vaccination and by previous infections with related orthoflaviviruses. Here, we sought to improve TBEV sero-diagnostics using an antigen combination of in-house expressed NS1 and EDIII in a multiplex, low-specimen-volume set-up for the detection of immune responses to TBEV and other clinically important orthoflaviviruses (i.e., West Nile virus, dengue virus, Japanese encephalitis virus, Usutu virus and Zika virus). We show that the combined use of NS1 and EDIII results in both a specific and sensitive test for the detection of TBEV IgG for patient diagnostics, vaccination responses and in seroprevalence studies. This novel approach potentially allows for a low volume-based, simultaneous analysis of IgG responses to a range of orthoflaviviruses with overlapping geographic circulations and clinical manifestations.

Rescue and in vitro characterization of a divergent TBEV-Eu strain from the Netherlands

Tick-borne encephalitis virus (TBEV) may cause tick-borne encephalitis (TBE), a potential life-threatening infection of the central nervous system in humans. Phylogenetically, TBEVs can be subdivided into three main subtypes, which differ in endemic region and pathogenic potential. In 2016, TBEV was first detected in the Netherlands. One of two detected strains, referred to as Salland, belonged to the TBEV-Eu subtype, yet diverged ≥ 2% on amino acid level from other members of this subtype. Here, we report the successful rescue of this strain using infectious subgenomic amplicons and its subsequent in vitro characterization by comparison to two well-characterized TBEV-Eu strains; Neudoerfl and Hypr. In the human alveolar epithelial cell line A549, growth kinetics of Salland were comparable to the high pathogenicity TBEV-Eu strain Hypr, and both strains grew considerably faster than the mildly pathogenic strain Neudoerfl. In the human neuroblastoma cell line SK-N-SH, Salland replicated faster and to higher infectious titers than both reference strains. All three TBEV strains infected primary human monocyte-derived dendritic cells to a similar extent and interacted with the type I interferon system in a similar manner. The current study serves as the first in vitro characterization of the novel, divergent TBEV-Eu strain Salland.

Continued Circulation of Tick-Borne Encephalitis Virus Variants and Detection of Novel Transmission Foci, the Netherlands

Tick-borne encephalitis virus (TBEV) is an emerging pathogen that was first detected in ticks and humans in the Netherlands in 2015 (ticks) and 2016 (humans). To learn more about its distribution and prevalence in the Netherlands, we conducted large-scale surveillance in ticks and rodents during August 2018-September 2020. We tested 320 wild rodents and >46,000 ticks from 48 locations considered to be at high risk for TBEV circulation. We found TBEV RNA in 3 rodents (0.9%) and 7 tick pools (minimum infection rate 0.02%) from 5 geographically distinct foci. Phylogenetic analyses indicated that 3 different variants of the TBEV-Eu subtype circulate in the Netherlands, suggesting multiple independent introductions. Combined with recent human cases outside known TBEV hotspots, our data demonstrate that the distribution of TBEV in the Netherlands is more widespread than previously thought.