Clostridioides difficile in calves, cattle and humans from Dutch dairy farms: Predominance of PCR ribotype 695 (clade 5, sequence type 11) in cattle.

Background: Clostridioides difficile is a leading cause of infectious diarrhea in both humans and livestock. In particular, C. difficile strains belonging to sequence type (ST) 11 are common enteropathogens. The aim of this study was to determine the presence and genetic relatedness of C. difficile types in dairy cattle and calves. Method: Dutch dairy farms were visited between February and December 2021. Feces was collected from adult dairy cattle and calves of two age categories (<4 weeks and 4 weeks-4 months). Fecal samples were also requested from dairy farmers, family members and employees. Fecal samples were cultured in an enrichment medium for 10-15 days and subcultured on solid media for capillary PCR ribotyping and whole genome sequencing. Results: C. difficile was detected on 31 out of 157 (19.8%) dairy farms. The highest prevalence was found in calves <4 weeks (17.5%). None of the 99 human samples collected were positive. Thirty-seven cultured isolates belonged to 11 different PCR ribotypes (RT) of which RT695 (56.8%) and RT078/126 (16.2%) were most abundant. In the database of the Netherlands National Expertise Centre for C. difficile infections (CDI, >10.000 patient isolates), RT695 was found in only two patients with hospital-onset CDI, diagnosed in 2020 and 2021. Sequence analysis of 21C. difficile RT695 from cattle revealed that all isolates belonged to clade 5, ST11 and contained genes encoding toxin A, toxin B and binary toxin. RT695 strains carried antimicrobial resistance genes typically found in clade 5C. difficile. Groups of genetically related RT695 isolates were found between dairy farms, whereas identical strains were only present in individual farms. Conclusions: C. difficile was found in ∼20% of dairy farms with a predominance of the relatively unknown RT695. Isolates of RT695 belonged to the same clade and sequence type as RT078/126, which is recognized as an important zoonotic type.

Attitudes towards zoonotic disease risk vary across sociodemographic, communication and health-related factors: A general population survey on literacy about zoonoses in the Netherlands.

Introduction: Literacy about zoonoses can contribute people adapt their behaviour to minimize zoonotic risks. In this study, associations between sociodemographic factors and zoonotic risk-averse attitudes were explored. Objective: To determine factors significantly associated with literacy about zoonoses across sociodemographic groups to inform targeted interventions aiming at improving awareness and zoonotic risk-avoidance behaviours. Method: Data was collected in 2022 using an online survey of a nationally representative sample of residents in the Netherlands. A multivariable logistic regression analysis, accounting for multiple hypothesis testing, was applied to assess whether there were significant associations between socio-demographic factors and attitudes towards zoonosis prevention. Results: A total of 2039 respondents completed the survey. People who were female, older, highly educated and those who searched for information about zoonoses, were relatively more likely to report behaviours favourable to the prevention of zoonoses. However, people with limited language and computer skills and immunocompromised people were significantly more likely to report risky behaviours. There were no significant associations found for pregnant women, dog and cat owners, those with an intermediate level of education and those who do have contact with farm animals. Conclusion: Certain sociodemographic groups display significantly riskier attitudes towards zoonoses. These groups provide targets where to improve literacy about zoonoses. This also implies that there is room for improvement in literacy about zoonoses, particularly among immunocompromised people and people with limited language and limited computer skills.

In vitro assay to determine inactivation of Toxoplasma gondii in meat samples.

Consumption of raw and undercooked meat is considered as an important source of Toxoplasma gondii infections. However, most non-heated meat products contain salt and additives, which affect T. gondii viability. It was our aim to develop an in vitro method to substitute the mouse bioassay for determining the effect of salting on T. gondii viability. Two sheep were experimentally infected by oral inoculation with 6.5 × 104 oocysts. Grinded meat samples of 50 g were prepared from heart, diaphragm, and four meat cuts. Also, pooled meat samples were either kept untreated (positive control), frozen (negative control) or supplemented with 0.6 %, 0.9 %, 1.2 % or 2.7 % NaCl. All samples were digested in pepsin-HCl solution, and digests were inoculated in duplicate onto monolayers of RK13 (a rabbit kidney cell line). Cells were maintained for up to four weeks and parasite growth was monitored by assessing Cq-values using the T. gondii qPCR on cell culture supernatant in intervals of one week and ΔCq-values determined. Additionally, 500 µL of each digest from the individual meat cuts, heart and diaphragm were inoculated in duplicate in IFNγ KO mice. Both sheep developed an antibody response and tissue samples contained similar concentrations of T. gondii DNA. From all untreated meat samples positive ΔCq-values were obtained in the in vitro assay, indicating presence and multiplication of viable parasites. This was in line with the mouse bioassay, with the exception of a negative mouse bioassay on one heart sample. Samples supplemented with 0.6 %-1.2 % NaCl showed positive ΔCq-values over time. The frozen sample and the sample supplemented with 2.7 % NaCl remained qPCR positive but with high Cq-values, which indicated no growth. In conclusion, the in vitro method has successfully been used to detect viable T. gondii in tissues of experimentally infected sheep, and a clear difference in T. gondii viability was observed between the samples supplemented with 2.7 % NaCl and those with 1.2 % NaCl or less.

A predictive risk map for human leptospirosis guiding further investigations in brown rats and surface water.

Leptospirosis is a zoonosis caused by the spirochete Leptospira spp. It is often not clear why certain areas appear to be hotspots for human leptospirosis. Therefore, a predictive risk map for the Netherlands was developed and assessed, based on a random forest model for human leptospirosis incidence levels with various environmental factors and rat density as variables. Next, it was tested whether misclassifications of the risk map could be explained by the prevalence of Leptospira spp. in brown rats. Three recreational areas were chosen, and rats (≥25/location) were tested for Leptospira spp. Concurrently, it was investigated whether Leptospira spp. prevalence in brown rats was associated with Leptospira DNA concentration in surface water, to explore the usability of this parameter in future studies. Approximately 1 L of surface water sample was collected from 10 sites and was tested for Leptospira spp. Although the model predicted the locations of patients relatively well, this study showed that the prevalence of Leptospira spp. infection in rats may be an explaining variable that could improve the predictive model performance. Surface water samples were all negative, even if they had been taken at sites with a high Leptospira spp. prevalence in rats.

Virulence and antimicrobial resistance of Shiga toxin-producing Escherichia coli from dairy goat and sheep farms in The Netherlands.

AIMS: The aim of our study was to investigate the virulence and resistance of STEC from small ruminants farms in The Netherlands. Moreover, the potential transmission of STEC between animals and humans on farms was evaluated. METHODS AND RESULTS: From 182 farms, in total, 287 unique STEC isolates were successfully recovered from animal samples. In addition, STEC was isolated from eight out of 144 human samples. The most detected serotype was O146:H21; however, among other serotypes also O26:H11, O157:H7, and O182:H25 isolates were present. Whole genome sequencing covering all human isolates and 50 of the animal isolates revealed a diversity of stx1, stx2, and eae sub-types and an additional 57 virulence factors. The assessed antimicrobial resistance phenotype, as determined by microdilution, was concordant with the genetic profiles identified by WGS. WGS also showed that three of the human isolates could be linked to an animal isolate from the same farm. CONCLUSIONS: The obtained STEC isolates showed great diversity in serotype, virulence, and resistance factors. Further analysis by WGS allowed for an in-depth assessment of the virulence and resistance factors present and to determine the relatedness of human and animal isolates.

Risk factors for acute toxoplasmosis in the Netherlands.

Toxoplasmosis caused by the protozoan parasite Toxoplasma gondii occurs worldwide. Infections range from asymptomatic to life-threatening. T. gondii infection is acquired either via bradyzoites in meat or via oocysts in the environment, but the relative importance of these path ways and the different sources remains unclear. In this study, possible risk factors for toxoplasmosis in the Netherlands were investigated. A case-control study was conducted including persons with recent infection and individuals with a negative test result for IgM and IgG for T. gondii between July 2016 and April 2021. A total of 48 cases and 50 controls completed the questionnaire. Food history and environmental exposure were compared using logistic regression. Consumption of different meats was found to be associated with recent infection. In the multivariable model, adjusted for age, gender, and pregnancy, consumption of large game meat (adjusted odds ratio (aOR) 8.2, 95% confidence interval 1.6-41.9) and sometimes (aOR 4.1, 1.1-15.3) or never (aOR 15.9, 2.2-115.5) washing hands before food preparation remained. These results emphasize the value of the advice to be careful with the consumption of raw and undercooked meat. Good hand hygiene could also be promoted in the prevention of T. gondii infection.

Systematic Review and Modelling of Age-Dependent Prevalence of Toxoplasma gondii in Livestock, Wildlife and Felids in Europe.

Toxoplasma gondii is a zoonotic parasite of importance to both human and animal health. The parasite has various transmission routes, and the meat of infected animals appears to be a major source of human infections in Europe. We aimed to estimate T. gondii prevalence in a selection of animal host species. A systematic literature review resulting in 226 eligible publications was carried out, and serological data were analyzed using an age-dependent Bayesian hierarchical model to obtain estimates for the regional T. gondii seroprevalence in livestock, wildlife, and felids. Prevalence estimates varied between species, regions, indoor/outdoor rearing, and types of detection methods applied. The lowest estimated seroprevalence was observed for indoor-kept lagomorphs at 4.8% (95% CI: 1.8-7.5%) and the highest for outdoor-kept sheep at 63.3% (95% CI: 53.0-79.3%). Overall, T. gondii seroprevalence estimates were highest within Eastern Europe, whilst being lowest in Northern Europe. Prevalence data based on direct detection methods were scarce and were not modelled but rather directly summarized by species. The outcomes of the meta-analysis can be used to extrapolate data to areas with a lack of data and provide valuable inputs for future source attribution approaches aiming to estimate the relative contribution of different sources of T. gondii human infection.

Signalling and responding to zoonotic threats using a One Health approach: a decade of the Zoonoses Structure in the Netherlands, 2011 to 2021.

In the Netherlands, the avian influenza outbreak in poultry in 2003 and the Q fever outbreak in dairy goats between 2007 and 2010 had severe consequences for public health. These outbreaks led to the establishment of an integrated human-veterinary risk analysis system for zoonoses, the Zoonoses Structure. The aim of the Zoonoses Structure is to signal, assess and control emerging zoonoses that may pose a risk to animal and/or human health in an integrated One Health approach. The Signalling Forum Zoonoses (SO-Z), the first step of the Zoonoses Structure, is a multidisciplinary committee composed of experts from the medical, veterinary, entomology and wildlife domains. The SO-Z shares relevant signals with professionals and has monthly meetings. Over the past 10 years (June 2011 to December 2021), 390 different signals of various zoonotic pathogens in animal reservoirs and humans have been assessed. Here, we describe the Zoonoses Structure with examples from signals and responses for four zoonotic events in the Netherlands (tularaemia, Brucella canis, West Nile virus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)). This may serve as an example for other countries on how to collaborate in a One Health approach to signal and control emerging zoonoses.

Potential risk factors for the presence of anti-Toxoplasma gondii antibodies in finishing pigs on conventional farms in the Netherlands.

BACKGROUND: The parasite Toxoplasma gondii (T. gondii) causes a substantial human disease burden worldwide. Ingesting improperly cooked pork containing T. gondii is considered one of the major sources of human infection in Europe and North America. Consequently, control of T. gondii infections in pigs is warranted. The European Food Safety Authority advised to perform serological monitoring of pigs and to conduct farm audits for the presence of risk factors. Serological monitoring was implemented in several Dutch slaughterhouses, one to six blood samples (a total of 5134 samples) were taken from each delivery of finishing pigs and samples were tested for the presence of anti-T. gondii antibodies. Using these test results, a cross-sectional study was initiated to assess the association between the within-herd T. gondii seroprevalence and the presence of risk factors for T. gondii infections at 69 conventional finishing pig farms in the Netherlands. RESULTS: A multivariable model showed significant (P ≤ 0.05) association with twelve potential risk factors: type of farm, presence of dogs, presence of ruminants, use of boots, use of shower and farm clothing, mode of rodent control, bedding accessibility for rodents, presence of cats, type of drinking water, heating of the feed, use of goat whey and shielding of birds. CONCLUSIONS: Serological monitoring of finishing pigs for T. gondii in slaughterhouses can be used to identify the presence of T. gondii risk factors on Dutch conventional finishing pig farms and seems a valuable tool to guide and monitor the control of T. gondii in pork production.

Zoonotic Pathogens in Eurasian Beavers (Castor fiber) in the Netherlands.

Successful repopulation programs of Eurasian beavers (Castor fiber) have resulted in an increase in beaver populations throughout Europe. This may be of public health relevance because beavers can host multiple zoonotic pathogens. From March 2018 to March 2020, opportunistic testing of dead beavers was performed for hepatitis E virus, orthohantavirus, Anaplasma phagocytophilum, Bartonella spp., extended-spectrum-betalactamase or AmpC (ESBL/AmpC-)-producing Enterobacteriaceae, Francisella tularensis, Leptospira spp., Neoehrlichia mikurensis, Babesia spp., Echinococcus multilocularis, Toxoplasma gondii, and Trichinella spp. From the 24 beavers collected, three zoonotic pathogens were detected. One beaver was positive for T. gondii, one was positive for ESBL/AmpC-producing Enterobacteriaceae, and one was positive for N. mikurensis. The latter finding indicates that beavers can be bitten by Ixodes ricinus and be exposed to tick-borne pathogens. The detected ESBL/AmpC-gene was blaCMY-2 in an Escherichia coli ST6599. The findings suggest that the role of beavers in the spread of zoonotic diseases in the Netherlands is currently limited.

Population genetics, invasion pathways and public health risks of the raccoon and its roundworm Baylisascaris procyonis in northwestern Europe.

The geographic range of the zoonotic raccoon roundworm (Baylisascaris procyonis) is expanding together with the range of its host, the raccoon (Procyon lotor). This creates a new public health risk in parts of Europe where this parasite was previously absent. In the Netherlands, a raccoon population is becoming established and incidental findings of B. procyonis have been reported. To assess the risk to public health, the prevalence of B. procyonis was determined in the province of Limburg, where currently the largest Dutch raccoon population is present, as well as in the adjoining region of southern Belgium. Furthermore, genetic methods were employed to assess invasion pathways of both the raccoon and B. procyonis to aid in the development of control measures. Macroscopic analysis of intestinal content and testing of faecal samples were performed to detect B. procyonis adults and eggs. The population genetics of both B. procyonis and its raccoon host were analysed using samples from central and northwestern Europe. B. procyonis was found in 14/23 (61%, 95% CI: 41%-78%) raccoons from Limburg, but was not detected in 50 Belgian raccoons. Genetic analyses showed that the majority of the Dutch raccoons and their roundworms were introduced through ex-captive individuals. As long as free-living raccoon populations originate from captivity, population control methods may be pursued. However, natural dispersal from the border regions will complicate prolonged population control. To reduce the public health risk posed by B. procyonis, public education to increase awareness and adapt behaviour towards raccoons is key.

Mining Public Metagenomes for Environmental Surveillance of Parasites: A Proof of Principle.

Parasites often have complex developmental cycles that account for their presence in a variety of difficult-to-analyze matrices, including feces, water, soil, and food. Detection of parasites in these matrices still involves laborious methods. Untargeted sequencing of nucleic acids extracted from those matrices in metagenomic projects may represent an attractive alternative method for unbiased detection of these pathogens. Here, we show how publicly available metagenomic datasets can be mined to detect parasite specific sequences, and generate data useful for environmental surveillance. We use the protozoan parasite Cryptosporidium parvum as a test organism, and show that detection is influenced by the reference sequence chosen. Indeed, the use of the whole genome yields high sensitivity but low specificity, whereas specificity is improved through the use of signature sequences. In conclusion, querying metagenomic datasets for parasites is feasible and relevant, but requires optimization and validation. Nevertheless, this approach provides access to the large, and rapidly increasing, number of datasets from metagenomic and meta-transcriptomic studies, allowing unlocking hitherto idle signals of parasites in our environments.

Effectiveness and costs of interventions to reduce the within-farm Toxoplasma gondii seroprevalence on pig farms in the Netherlands.

BACKGROUND: The parasite Toxoplasma gondii (T. gondii) is recognized as one of the major foodborne pathogens with a high human disease burden. To control T. gondii infections in pigs, European Food Safety Agency (EFSA) advises serological testing of pigs and audits of pig farms to identify risk factors for T. gondii infection. In line with this approach, the aim of the current study was to assess the effectiveness and costs of intervention measures implemented to reduce the T. gondii seroprevalence on finishing pig farms in the Netherlands. A crossover clinical trial was conducted at five case farms were their own control and the cross-over moment was the implementation of interventions to reduce risk factors. Each of the case farms had a farm-specific intervention strategy with one principal intervention measure (neutering of cats, professional rodent control or covering food storage). RESULTS: All finishing pig farms (n = 5) showed a reduction in T. gondii seroprevalence within one year of implementing the intervention strategy. Cat neutering (n = 3) and feed coverage (n = 1) showed statistically significant reductions in seroprevalence. Rodent control (n = 1) did not show a statistically significant reduction. The estimated reduction in seroprevalence in response to the neutering of cats and feed coverage were 67 and 96 %, respectively. CONCLUSIONS: Our work demonstrates that it is possible to reduce the within-farm T. gondii seroprevalence within one year after interventions were implemented to reduce T. gondii risk factors. This information is essential and encouraging for policy makers, food business operators, and farmers to implement in their risk assessment and to apply to food safety control systems.

Prevalence, risk factors and genetic traits of Salmonella Infantis in Dutch broiler flocks.

Salmonella Infantis is a poultry-adapted Salmonella enterica serovar that is increasingly reported in broilers and is also regularly identified among human salmonellosis cases. An emerging S. Infantis mega-plasmid (pESI), carrying fitness, virulence and antimicrobial resistance genes, is also increasingly found. We investigated the prevalence, genetic characteristics and risk factors for (pESI-carrying) S. Infantis in broilers. Faecal samples from 379 broiler flocks (in 198 farms with ≥3000 birds) in the Netherlands were tested. A questionnaire about farm characteristics was also administered. Sampling was performed in July 2018-May 2019, three weeks before slaughter. Fourteen flocks (in 10 farms) were S. Infantis-positive, resulting in a 3.7 % flock-level and 5.1 % farm-level prevalence. Based on multi-locus sequence typing (MLST), all isolates belonged to sequence type 32. All but one isolate carried a pESI-like mega-plasmid. Core-genome MLST showed considerable heterogeneity among the isolates, even within the same farm, with a few small clusters detected. The typical pESI-borne multi-resistance pattern to aminoglycosides, sulphonamide and tetracycline (93 %), as well as trimethoprim (71 %), was found. Additionally, resistance to (fluoro)quinolones based on gyrA gene mutations was detected. S. Infantis was found more often in flocks using salinomycin as coccidiostat, where flock thinning was applied or litter quality was poor, whereas employing external cleaning companies, wheat in feed, and vaccination against infectious bronchitis, were protective. Suggestive evidence for vertical transmission from hatcheries was found. A heterogeneous (pESI-carrying) S. Infantis population has established itself in Dutch broiler flocks, calling for further monitoring of its spread and a comprehensive appraisal of control options.

Unravelling the genetic diversity and relatedness of Echinococcus multilocularis isolates in Eurasia using the EmsB microsatellite nuclear marker.

The cestode Echinococcus multilocularis is the causative agent of alveolar echinococcosis, a severe helminthic zoonotic disease distributed in the Northern Hemisphere. The lifecycle of the parasite is mainly sylvatic, involving canid and rodent hosts. The absence of genetic data from most eastern European countries is a major knowledge gap, affecting the study of associations with parasite populations in Western Europe. In this study, EmsB microsatellite genotyping of E. multilocularis was performed to describe the genetic diversity and relatedness of 785 E. multilocularis isolates from four western and nine eastern European countries, as well as from Armenia and the Asian parts of Russia and Turkey. The presence of the same E. multilocularis populations in the Benelux resulting from expansion from the historical Alpine focus can be deduced from the main profiles shared between these countries. All 33 EmsB profiles obtained from 528 samples from the nine eastern European countries belonged to the European clade, except one Asian profile form Ryazan Oblast, Russia. The expansion of E. multilocularis seems to have progressed from the historical Alpine focus through Hungary, Slovakia, the Czech Republic and southern Poland towards Latvia and Estonia. Most of the samples from Asia belong to the Asian clade, with one EmsB profile shared between Armenia and Turkey, and two between Turkey and Russia. However, two European profiles were described from two foxes in Turkey, including one harboring worms from both European and Asian clades. Three EmsB profiles from three Russian samples were associated with the Arctic clade. Two E. multilocularis profiles from rodents from Lake Baikal belonged to the Mongolian clade, described for the first time here using EmsB. Further worldwide studies on the genetic diversity of E. multilocularis using both mitochondrial sequencing and EmsB genotyping are needed to understand the distribution and expansion of the various clades.

Inactivation of Trichinella muscle larvae at different time-temperature heating profiles simulating home-cooking.

BACKGROUND: Trichinellosis is caused by consumption of raw or undercooked meat containing infective Trichinella muscle larvae (ML). Only few studies on heat-inactivation of Trichinella ML are available in literature and more validated data concerning heat inactivation is needed to improve the risk estimation. OBJECTIVE AND METHODS: The aim of the present study was to evaluate the two in vitro methods "staining" and "morphological examination" as proxies for Trichinella ML heat inactivation in comparison with the mouse bioassay method to get more insight in the relationship between heat, heating time and inactivation of Trichinella ML. The second aim was to evaluate whether these methods could replace the bioassay in the light of ongoing animal use reduction in lifescience research. Tubes containing quantified live Trichinella ML were exposed to heat profiles ranging from 40 to 80 °C. Subsequently, inactivation was evaluated using both methylene blue staining and morphological examination, which was validated by bioassay. Results were used to model Trichinella inactivation. RESULTS: Trichinella muscle larvae exposed to 60 °C or higher for 12-12.5 min were not infective to mice. We found that morphological examination was more consistent with the bioassay than methylene blue staining. Modelled inactivation fitted experimental data consistently. Moreover, this study shows that larval Trichinella morphology may be used in situations where bioassays are not possible or prohibited. CONCLUSIONS: The relationship between heat and inactivation of larvae obtained from this study could be used in Trichinella QMRA models to improve quantification of the risk of Trichinella infection.

Surveillance of foodborne parasitic diseases in Europe in a One Health approach.

In 2012, WHO/FAO ranked 24 foodborne parasites (FBP) using multicriteria decision analysis (MCDA) to provide risk assessors with a basis for prioritising control of highly ranked FBP on the global level. One conclusion was that ranking may differ substantially per region. In Europe, the same methodology was used to rank FBP of relevance for Europe. Of the 24 FBP, the top-five prioritised FBP were identified for Europe as Echinococcus multilocularis, Toxoplasma gondii, Trichinella spiralis, E. granulosus, and Cryptosporidium spp., all of which are zoonotic. The objective of the present study was to provide an overview of surveillance and reporting systems in Europe for these top five prioritised FBP in the human and animal populations, to identify gaps, and give recommendations for improvement. Information on the surveillance systems was collected from 35 European countries and analysed according to the five different regions. For most FBP, human surveillance is passive in most countries and regions in Europe and notification differs between countries and regions. Adequate surveillance programmes for these FBP are lacking, except for T. spiralis, which is notifiable in 34 countries with active surveillance in susceptible animals under EU directive. Although human and animal surveillance data are available for the five prioritised FBP, we identified a lack of consistency in surveillance and reporting requirements between national experts and European bodies. Recommendations for improved surveillance systems are discussed.

Mathematical modelling of Toxoplasma gondii transmission: A systematic review.

BACKGROUND: Toxoplasma gondii is a ubiquitous protozoan parasite that can infect virtually all warm-blooded animals. It is the causative agent of toxoplasmosis, a significant public health issue worldwide. Mathematical models are useful to study the transmission dynamics of T. gondii infection in different settings, and may be used to compare the effectiveness of prevention measures. METHODS: To obtain an overview of existing mathematical models for transmission of T. gondii, a systematic review was undertaken. The review was conducted according to an a priori protocol and the results were reported according to the PRISMA guidelines. Specific search terms were developed and used in the search of three databases (Scopus, PubMed, and Embase). RESULTS: In total, 484 unique records were retrieved from the systematic search. Among them, 15 studies that used mathematical models to study the transmission of T. gondii. These studies were categorized into four groups based on the primary aims: dynamics of transmission (n = 8), intervention (n = 5), spatial distribution (n = 1), and outbreak investigation (n = 1). CONCLUSIONS: Considering the high disease burden caused by T. gondii, the number of studies using mathematical models to understand the transmission dynamics of this parasite and to evaluate the effectiveness of intervention measures was only 15. This systematic review provides an overview of existing mathematical models and identifies the data gaps for model building. The results from this study can be helpful for further development of mathematical models and improved understanding of the transmission dynamics of T. gondii infection.

Sources and transmission routes of campylobacteriosis: A combined analysis of genome and exposure data.

OBJECTIVES: To determine the contributions of several animal and environmental sources of human campylobacteriosis and identify source-specific risk factors. METHODS: 1417 Campylobacter jejuni/coli isolates from the Netherlands in 2017-2019 were whole-genome sequenced, including isolates from human cases (n = 280), chickens/turkeys (n = 238), laying hens (n = 56), cattle (n = 158), veal calves (n = 49), sheep/goats (n = 111), pigs (n = 110), dogs/cats (n = 100), wild birds (n = 62), and surface water (n = 253). Questionnaire-based exposure data was collected. Source attribution was performed using core-genome multilocus sequence typing. Risk factors were determined on the attribution estimates. RESULTS: Cases were mostly attributed to chickens/turkeys (48.2%), dogs/cats (18.0%), cattle (12.1%), and surface water (8.5%). Of the associations identified, never consuming chicken, as well as frequent chicken consumption, and rarely washing hands after touching raw meat, were risk factors for chicken/turkey-attributable infections. Consuming unpasteurized milk or barbecued beef increased the risk for cattle-attributable infections. Risk factors for infections attributable to environmental sources were open water swimming, contact with dog faeces, and consuming non-chicken/turkey avian meat like game birds. CONCLUSIONS: Poultry and cattle are the main livestock sources of campylobacteriosis, while pets and surface water are important non-livestock sources. Foodborne transmission is only partially consistent with the attributions, as frequency and alternative pathways of exposure are significant.