Zoonotic and arthropod-borne diseases

While West Nile virus (WNV), a mosquito-borne zoonotic pathogen, is detected every year in animals in Spain, clinical human cases occur more sporadically. Most explanatory and predictive models for WNV circulation focus on single components and aggregate multiple year data into a single dataset.

We sought WNV circulation environmental drivers across different ecological components (vectors, reservoirs, and dead-end hosts), by analysing their spatial and temporal dynamics.

We used active and passive surveillance data collected in Spain between 2003 and 2022, encompassing mosquitoes, 120 bird species, 115 mammal species, and humans. To understand WNV circulation, mosquito spatial and host spatiotemporal models were developed, incorporating current and lagged environmental variables. Our One Health approach integrated the different models to determine WNV exposure risk, including 1 year in advance.

Over 20 years, WNV exposure risk in Spain rose by 19% in birds, 17% in non-human mammals, and 38% in humans. In birds and non-human mammals, exposure more likely occurred in areas experiencing mean respective annual temperatures > 5 °C and > 8 °C in the previous year. In humans, increased exposure risk concurred with mild winters (> 5.3 °C). Integrating mosquito and host models found the country’s southern half and mediterranean coast most suited for WNV. Predictive models solely using prior-year variables yielded comparable results to contemporaneous ones.

The models suggest that annual human WNV transmission may occur more regularly than evidenced by surveillance, possibly due to asymptomatic or misdiagnosed cases. Our framework could serve as an early warning tool, enhancing outbreak preparedness up to 1 year ahead.

One Health (OH) is a multisectoral approach that aims to optimise health of people, animals and the environment, recognising their interconnection. Despite gaining political support in recent years, examples of successful OH implementation among governmental institutions across the European Union/European Economic Area (EU/EEA) remain limited.

To identify key enablers and barriers to collaboration across human, animal and environmental health sectors, and provide a framework to support national OH operationalisation in the EU/EEA.

Semi-structured interviews were conducted with 26 experts from national public health institutes in 15 EU/EEA countries, recruited through European Centre for Disease Prevention and Control networks. Transcripts were analysed through qualitative content analysis.

Collaborations between human and animal health sectors were reported, but greater integration of the environmental sector is needed to strengthen OH partnerships. Analysis of opportunities and challenges highlighted key interlinked elements that can facilitate sustainable OH implementation. Strong political leadership emerged as pivotal to drive policy coherence in nexus areas, embed collaborative activities within core funding, and facilitate cross-sectoral partnerships at the technical level.

This qualitative study provides an overview of enablers and barriers to OH collaboration at the national level. The findings constitute the basis for an empirically derived framework emphasising the cyclical relationship between political leadership and cross-sectoral technical collaboration. Incremental steps, starting with strengthening existing cross-sectoral relationships, have the potential to generate self-reinforcing progress and enhance emergency preparedness. These empirical insights provide a foundation for developing and evaluating OH policies in EU/EEA countries, complementing existing international guidelines.

Toxoplasma gondii is a zoonotic protozoan capable of infecting warm-blooded animal species and humans. Although toxoplasmosis presents mostly as mild or asymptomatic infection in immunocompetent individuals, in unborn children and people with weakened immune systems, the disease can be severe with ocular, neurological or multi-systemic manifestations and even death.

We aimed to collate and analyse data on T. gondii seroprevalence in humans to model and compare age-dependent prevalence in geographic regions in Europe.

A systematic review identified 1,822 scientific publications, from which seroprevalence data were extracted from 69 studies. Data were analysed using a Bayesian hierarchical model.

The modelling of the seroprevalence indicated the highest incidence rates in eastern (50%) and western (48%) Europe, with the lowest estimates in northern Europe (18%) and the United Kingdom (UK) (18%). Eastern and western Europe were regions where T. gondii infections occurred earliest in life, with half of the population expected to be seropositive by the age of 44 and 47 years, respectively. In contrast, in northern Europe and the UK the modelled median time to infection exceeded 170 years.

Results of the study provide a robust baseline for future epidemiological research on human T. gondii infections in Europe and may be useful to validate subsequent research, such as risk assessment studies.

Laboratory surveillance detected an unprecedented increase in Cryptosporidium spp. (predominantly Cryptosporidium hominis) in England and Wales in August 2023. Cases are not routinely followed up in all of England and Wales, and initial investigations identified no common exposures.

To perform a retrospective case–case study investigation of the increase in Cryptosporidium spp. in England and Wales.

We conducted an unmatched case–case study with 203 cases of laboratory-confirmed C. hominis and 614 comparator cases of laboratory-confirmed Campylobacter spp. reported between 14 August and 30 September 2023. We fitted a multilevel logistic regression model, with random intercepts for geographical region, to estimate adjusted odds ratios (aOR) for exposures. We present the final model as aOR and 95% confidence intervals (CI).

Multivariable analysis identified associations with swimming pool use (aOR: 5.3, 95% CI: 2.3–9.3), travel to Spain (aOR: 6.5, 95% CI: 3.5–12.3) and young age, with children 0–4 years having the strongest association of being a case (aOR: 3.6, 95% CI: 1.5–8.6). We also identified associations with swimming in a river, and travel to France or Türkiye, but there was low frequency of exposure among cases and comparator cases.

Following the largest recorded increase of Cryptosporidium spp. and in particular C. hominis cases in England and Wales, we identified several exposures, suggesting that causation was likely to be multifactorial. We recommend development of a standardised questionnaire to enable rapid investigation of future case increases, which will improve existing surveillance and inform public health actions.

Tick-borne encephalitis (TBE) can be a severe neurological disease. Identifying ecological factors that may facilitate tick-borne encephalitis virus (TBEV) circulation in the Netherlands could improve awareness and detection.

We aimed to identify ecological factors affecting TBEV circulation in the Netherlands and to determine if there is sustained circulation and spread of the virus.

Between June and September 2021, rodents and ticks from three previously TBEV-positive locations were tested for TBEV by PCR. We sequenced TBEV and compared the sequences with previous and subsequent sequences from the Netherlands and other countries to investigate the spread of TBEV-variants.

We captured 383 rodents, 928 feeding ticks and 1,571 questing Ixodes ticks and detected TBEV from six (three Apodemus sylvaticus and three Clethrionomys glareolus) (2.9%) of 206 tested rodents and two (0.9%) of 215 questing tick pools. Detection of TBEV was associated with questing tick density (Mann–Whitney U test  = 81.5; 95% confidence interval (CI): − 3.7–6.3 × 10⁻⁵; p = 0.05). Tick larvae (odds ratio (OR) = 9.0; 95% CI: 2.8–38.2; p < 0.01) and nymphs (OR = 3.8; 95% CI: 1.3–13.6; p < 0.01) were more frequent on A. sylvaticus than on C. glareolus. Sequence comparisons suggest multiple introductions and local circulation of TBEV but no spread among locations.

Tick-borne encephalitis virus occurs in diverse woodlands in the Netherlands, posing a risk to those frequenting these areas. Surveillance for the early detection and monitoring of TBEV spread, along with public awareness campaigns on preventive measures, should continue. Recognition of TBE symptoms and supportive diagnostics should be made available nationwide.