Tijs J. Tobias
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Tijs J. Tobias has a total of 96 co-authors. Here are the top co-authors by number of shared publications:
- Arjan Stegeman
Department Population Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands
6 shared publications A. van Nes
Department of Population Health Sciences, Farm Animal Health Unit, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
5 shared publicationsA. Bouma
Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands
4 shared publications- Don Klinkenberg
Centre for infectious disease control, National institute for public health and the environment (RIVM), Bilthoven, the Netherlands
4 shared publications J.A. Stegeman
Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands
4 shared publicationsA.J.J.M. Daemen
Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands
3 shared publications
Latest Publications
- Open Access
- 24 November 2025
- Published by Elsevier in Smart Agricultural Technology
- Vol. 12
HogDSim - A within-farm modeling framework for infectious diseases of swine
- 24 November 2025
- Published by Elsevier in Smart Agricultural Technology
- Vol. 12
Open AccessHogDSim - A within-farm modeling framework for infectious diseases of swine
- Open Access
- 15 October 2024
- Published by Springer Nature in Research Square
The Versatility of Influenza A Surveillance and Monitoring in European Swine; results from an electronic survey
Surveillance of influenza A virus in swine populations is essential, from both a veterinary and public health perspective. Although some international organizations have published guidelines for swine influenza A virus (swIAV) surveillance, there is no standardized guidelines available and a clear overview of current existing surveillance activities is lacking at the European level. This study aimed to describe swIAV surveillance systems across Europe in 2022. An electronic survey was distributed to 41 member countries of the Cost Action “ESFLU”, resulting in 44 responses from 39 institutions representing 25 countries. The analysis identified 26 unique surveillance systems, operating at local, national, regional, and multi-national levels. The majority of the systems had the objective of surveilling emerging strains or monitoring for swine influenza viruses in herds. In 2022, approximately 3,500 farms were sampled, with piglets and weaners being the most sampled age groups. Most systems (n=23) used RT-PCR for detection and fourteen used sequencing for viral characterization/subtyping. The study also highlighted a strong reliance on passive surveillance. While data sharing with OFFLU and other public databases is advocated, nine systems consistently shared their data, while eleven others indicated that data sharing occurs conditionally, depending on specific circumstances. The study emphasized the need for harmonized guidelines for surveillance and the establishment of pipelines for the systematic collection and analysis of data in swIAV in pigs.
- 15 October 2024
- Published by Springer Nature in Research Square
Open AccessThe Versatility of Influenza A Surveillance and Monitoring in European Swine; results from an electronic survey
Surveillance of influenza A virus in swine populations is essential, from both a veterinary and public health perspective. Although some international organizations have published guidelines for swine influenza A virus (swIAV) surveillance, there is no standardized guidelines available and a clear overview of current existing surveillance activities is lacking at the European level. This study aimed to describe swIAV surveillance systems across Europe in 2022. An electronic survey was distributed to 41 member countries of the Cost Action “ESFLU”, resulting in 44 responses from 39 institutions representing 25 countries. The analysis identified 26 unique surveillance systems, operating at local, national, regional, and multi-national levels. The majority of the systems had the objective of surveilling emerging strains or monitoring for swine influenza viruses in herds. In 2022, approximately 3,500 farms were sampled, with piglets and weaners being the most sampled age groups. Most systems (n=23) used RT-PCR for detection and fourteen used sequencing for viral characterization/subtyping. The study also highlighted a strong reliance on passive surveillance. While data sharing with OFFLU and other public databases is advocated, nine systems consistently shared their data, while eleven others indicated that data sharing occurs conditionally, depending on specific circumstances. The study emphasized the need for harmonized guidelines for surveillance and the establishment of pipelines for the systematic collection and analysis of data in swIAV in pigs.
- Open Access
- 11 October 2023
- Published by Taylor & Francis in Journal of Applied Animal Welfare Science
- Vol. 28 (3) , 357-370
Handling End-of-Life Situations in Small Animal Practice: What Strategies do Veterinarians Contemplate During their Decision-Making Process?
This study researched end-of-life (EoL) decision-making processes in small animal practices in the Netherlands, focusing on strategies veterinarians contemplate during this process. Fourteen veterinarians were interviewed about animal end-of-life decision-making. The results of these interviews show that the decision-making process consists of three steps. The first step is to assess the animal's health and welfare. During the second step, veterinarians consider the position of the owner. Based on steps 1 and 2, veterinarians decide in step 3 whether their advice is to a) euthanize or b) contemplate one or more strategies to come to a decision or potentially alter the decision. These results can support members of the veterinary profession to reflect on their decision-making process. If veterinarians know what strategies their peers use to deal with EoL situations, this can help to reduce the stress they experience in such situations. In addition, veterinarians may find inspiration for new strategies in the study results. For the veterinary profession itself, the current results can be used as a starting point for describing best practices for EoL decision-making in small animal practice.
- 11 October 2023
- Published by Taylor & Francis in Journal of Applied Animal Welfare Science
- Vol. 28 (3) , 357-370
Open AccessHandling End-of-Life Situations in Small Animal Practice: What Strategies do Veterinarians Contemplate During their Decision-Making Process?
This study researched end-of-life (EoL) decision-making processes in small animal practices in the Netherlands, focusing on strategies veterinarians contemplate during this process. Fourteen veterinarians were interviewed about animal end-of-life decision-making. The results of these interviews show that the decision-making process consists of three steps. The first step is to assess the animal's health and welfare. During the second step, veterinarians consider the position of the owner. Based on steps 1 and 2, veterinarians decide in step 3 whether their advice is to a) euthanize or b) contemplate one or more strategies to come to a decision or potentially alter the decision. These results can support members of the veterinary profession to reflect on their decision-making process. If veterinarians know what strategies their peers use to deal with EoL situations, this can help to reduce the stress they experience in such situations. In addition, veterinarians may find inspiration for new strategies in the study results. For the veterinary profession itself, the current results can be used as a starting point for describing best practices for EoL decision-making in small animal practice.
- Open Access
- 29 September 2023
- Published by Elsevier in Journal of Food Protection
- Vol. 86 (11) , 100171
A Review of Slaughter Practices and Their Effectiveness to Control Microbial – esp. Salmonella spp. – Contamination of Pig Carcasses
- 29 September 2023
- Published by Elsevier in Journal of Food Protection
- Vol. 86 (11) , 100171
Open AccessA Review of Slaughter Practices and Their Effectiveness to Control Microbial – esp. Salmonella spp. – Contamination of Pig Carcasses
- Open Access
- 16 February 2023
- Published by MDPI AG in Microorganisms
- Vol. 11 (2) , 500
Evaluation of Non-Invasive Sampling Methods for Detection of Hepatitis E Virus Infected Pigs in Pens
Pigs are a reservoir of hepatitis E virus (HEV), which causes hepatitis in humans. To study the epidemiology of HEV in pig farms, sampling methods are currently used that cause discomfort to pigs, such as rectal sampling. In line with the 3Rs principle, we aimed to evaluate non-invasive methods to detect pens with HEV-shedding pigs. Twenty-eight pens of one farm were sampled cross-sectionally. Individual rectal swabs (IRS) were collected to determine prevalence within pens. Four pen-level samples were compared: a pool of IRS per pen (P), boot socks (BS), oral fluid (OF) and pooled faecal droppings (FD). Each sample was tested by RT-PCR and the sensitivity and specificity of each method was determined by Bayesian latent class analysis. According to IRS, 19/28 pens were HEV positive. BS had a sensitivity of 95% and detected HEV in pens with 10% of pigs shedding; however, specificity was below 30%. FD were comparably accurate to P, with a sensitivity and specificity of 94% and 86%, respectively. BS sampling is thus advised to detect early shedding of HEV or pen contamination, and FD to determine the duration of shedding. This study demonstrates that non-invasive sampling can replace rectal swabs in research on HEV in pigs.
- 16 February 2023
- Published by MDPI AG in Microorganisms
- Vol. 11 (2) , 500
Open AccessEvaluation of Non-Invasive Sampling Methods for Detection of Hepatitis E Virus Infected Pigs in Pens
Pigs are a reservoir of hepatitis E virus (HEV), which causes hepatitis in humans. To study the epidemiology of HEV in pig farms, sampling methods are currently used that cause discomfort to pigs, such as rectal sampling. In line with the 3Rs principle, we aimed to evaluate non-invasive methods to detect pens with HEV-shedding pigs. Twenty-eight pens of one farm were sampled cross-sectionally. Individual rectal swabs (IRS) were collected to determine prevalence within pens. Four pen-level samples were compared: a pool of IRS per pen (P), boot socks (BS), oral fluid (OF) and pooled faecal droppings (FD). Each sample was tested by RT-PCR and the sensitivity and specificity of each method was determined by Bayesian latent class analysis. According to IRS, 19/28 pens were HEV positive. BS had a sensitivity of 95% and detected HEV in pens with 10% of pigs shedding; however, specificity was below 30%. FD were comparably accurate to P, with a sensitivity and specificity of 94% and 86%, respectively. BS sampling is thus advised to detect early shedding of HEV or pen contamination, and FD to determine the duration of shedding. This study demonstrates that non-invasive sampling can replace rectal swabs in research on HEV in pigs.
- Open Access
- 16 January 2023
- Published by Springer Nature in Porcine Health Management
- Vol. 9 (1) , 1-16
Comparison of efficacy of needle-free injection versus injection by needle for iron supplementation of piglets: a double blind randomized controlled trial
Background: In pig husbandry, most piglets receive an intramuscular injection with iron around three days of age for the prevention of hypochromic, microcytic anaemia. In recent years an increased interest is noted for needle-free injections, because of efficiency and safety for man and animal. This study aims to support the evidence on efficacy to extent the registration of a commercial iron supplement with a needle-free administration application. To this aim the study has two objectives: 1) to determine the effect of needle-free injection of the iron supplement on the mean blood Haemoglobin level at weaning, as primary outcome, and mean Haematocrit and mean Body weight of pigs at weaning as secondary outcome compared to no treatment, as main determinant of iron deficiency anaemia in piglets at time of weaning; 2) to compare the effects of needle-free administration of the iron supplement with regular injection by needle, with regard to the course over time of Haemoglobin, Haematocrit, piglet growth and the differentiated haematological and serum iron parameters.Methods: A double blind randomized controlled trial was conducted with 72 piglets, 8 piglets per litter from 9 litters. At three days of age pigs were selected, based on body weight, and random allocated to three study groups: a) control non-treated group (2 pigs per litter, 18 in total), b) a group with regular iron injection by needle injection (3 pigs per litter, 27 in total), c) a group that received iron by needle-free injection (3 pigs per litter, 27 in total). At four points in time (day 3, 14, 26 and 40) piglets were weighed and bled to analyse the dynamics of red blood counts and haematological parameters as well as serum iron parameters. The primary outcome parameter was the Haemoglobin (Hb) level on day 26. Of secondary importance were Haematocrit (Ht) and body weight (BW) at weaning and parameters with tertiary importance were the course of Hb, Ht and differentiated red blood cell parameters, serum iron, iron binding capacity and iron saturation. In the statistical analyses, linear mixed effect regression modelling was used to account for repeated measures within litters and pigs.Results: The analyses showed that needle-free administration was as efficacious to prevent iron deficiency anaemia at day 26 as administration using regular needle injection, compared to the control group. The mean level of Hb and Ht of pigs in the needle and needle-free group did not differ significantly. No side effects were observed.Conclusion: It is concluded that needle-free iron administration of the tested product is as efficacious as regular administration by needle injection.
- 16 January 2023
- Published by Springer Nature in Porcine Health Management
- Vol. 9 (1) , 1-16
Open AccessComparison of efficacy of needle-free injection versus injection by needle for iron supplementation of piglets: a double blind randomized controlled trial
Background: In pig husbandry, most piglets receive an intramuscular injection with iron around three days of age for the prevention of hypochromic, microcytic anaemia. In recent years an increased interest is noted for needle-free injections, because of efficiency and safety for man and animal. This study aims to support the evidence on efficacy to extent the registration of a commercial iron supplement with a needle-free administration application. To this aim the study has two objectives: 1) to determine the effect of needle-free injection of the iron supplement on the mean blood Haemoglobin level at weaning, as primary outcome, and mean Haematocrit and mean Body weight of pigs at weaning as secondary outcome compared to no treatment, as main determinant of iron deficiency anaemia in piglets at time of weaning; 2) to compare the effects of needle-free administration of the iron supplement with regular injection by needle, with regard to the course over time of Haemoglobin, Haematocrit, piglet growth and the differentiated haematological and serum iron parameters.Methods: A double blind randomized controlled trial was conducted with 72 piglets, 8 piglets per litter from 9 litters. At three days of age pigs were selected, based on body weight, and random allocated to three study groups: a) control non-treated group (2 pigs per litter, 18 in total), b) a group with regular iron injection by needle injection (3 pigs per litter, 27 in total), c) a group that received iron by needle-free injection (3 pigs per litter, 27 in total). At four points in time (day 3, 14, 26 and 40) piglets were weighed and bled to analyse the dynamics of red blood counts and haematological parameters as well as serum iron parameters. The primary outcome parameter was the Haemoglobin (Hb) level on day 26. Of secondary importance were Haematocrit (Ht) and body weight (BW) at weaning and parameters with tertiary importance were the course of Hb, Ht and differentiated red blood cell parameters, serum iron, iron binding capacity and iron saturation. In the statistical analyses, linear mixed effect regression modelling was used to account for repeated measures within litters and pigs.Results: The analyses showed that needle-free administration was as efficacious to prevent iron deficiency anaemia at day 26 as administration using regular needle injection, compared to the control group. The mean level of Hb and Ht of pigs in the needle and needle-free group did not differ significantly. No side effects were observed.Conclusion: It is concluded that needle-free iron administration of the tested product is as efficacious as regular administration by needle injection.
- Open Access
- 30 September 2022
- Published by Springer Nature in Porcine Health Management
- Vol. 8 (1) , 1-5
Cystic hygroma in a female suckling pig: a case report
Background: Cystic hygromas (lymphangiomas) are rarely reported in various animal species, humans included. A hygroma is a benign congenital malformation of the lymphatic drainage system, presenting itself as a mass consisting of multiple cysts of various sizes with a watery content. Case presentation: This report describes clinical, ultrasonographic, and post-mortem findings of a cystic hygroma in a suckling pig. The mass was characterized by a few thin-walled cysts, containing clear yellow serous fluid. Histologically, the central cavity was lined by a single layer of squamous cells, supported by a thick fibrous stroma. On immunohistochemistry, scattered lining cells were weakly positive for Factor-VIII, suggesting their possible endothelial origin. Conclusions: This case report contributes to raising awareness on this condition in pigs allowing early identification in life so that appropriate care can be provided. The case report attributes to science on hygromas in general, as better understanding of pathologic features, the aetiology and appropriate treatment are needed.
- 30 September 2022
- Published by Springer Nature in Porcine Health Management
- Vol. 8 (1) , 1-5
Open AccessCystic hygroma in a female suckling pig: a case report
Background: Cystic hygromas (lymphangiomas) are rarely reported in various animal species, humans included. A hygroma is a benign congenital malformation of the lymphatic drainage system, presenting itself as a mass consisting of multiple cysts of various sizes with a watery content. Case presentation: This report describes clinical, ultrasonographic, and post-mortem findings of a cystic hygroma in a suckling pig. The mass was characterized by a few thin-walled cysts, containing clear yellow serous fluid. Histologically, the central cavity was lined by a single layer of squamous cells, supported by a thick fibrous stroma. On immunohistochemistry, scattered lining cells were weakly positive for Factor-VIII, suggesting their possible endothelial origin. Conclusions: This case report contributes to raising awareness on this condition in pigs allowing early identification in life so that appropriate care can be provided. The case report attributes to science on hygromas in general, as better understanding of pathologic features, the aetiology and appropriate treatment are needed.
- Open Access
- 21 December 2021
- Published by Taylor & Francis in Emerging Microbes & Infections
- Vol. 11 (1) , 91-94
Experimental and field investigations of exposure, replication and transmission of SARS-CoV-2 in pigs in the Netherlands
Knowledge on host species susceptibility and transmission of emerging pathogens is essential to assess the risk for reservoir development. SARS-CoV-2 can infect multiple animal species, which has b...
- 21 December 2021
- Published by Taylor & Francis in Emerging Microbes & Infections
- Vol. 11 (1) , 91-94
Open AccessExperimental and field investigations of exposure, replication and transmission of SARS-CoV-2 in pigs in the Netherlands
Knowledge on host species susceptibility and transmission of emerging pathogens is essential to assess the risk for reservoir development. SARS-CoV-2 can infect multiple animal species, which has b...
- Open Access
- 4 August 2021
- Published by MDPI AG in Antibiotics
- Vol. 10 (8) , 945
ESBL-Producing, Carbapenem- and Ciprofloxacin-Resistant Escherichia coli in Belgian and Dutch Broiler and Pig Farms: A Cross-Sectional and Cross-Border Study
Background. The use of antibiotics in food production selects for resistant bacteria and may cause a threat to human and animal health. Belgium and the Netherlands have one of the highest densities of broilers and pigs in Europe, making active monitoring of antibiotic use and resistance in this region vital. Objectives. This study aimed to quantify ESBL-producing (ESBL-E. coli), carbapenem- and ciprofloxacin-resistant (CiproR) Escherichia coli in animal feces on broiler and pig farms with a history of high antibiotic use in Belgium and the Netherlands. Methods. A total of 779 broiler and 817 pig fecal samples, collected from 29 conventional broiler and 31 multiplier pig farms in the cross-border region of Belgium and the Netherlands, were screened for the presence of antibiotic-resistant E. coli using selective culturing. Results. Carbapenem-resistant E. coli were not detected. ESBL-E. coli were remarkably more prevalent in samples from Belgian than Dutch farms. However, CiproR-E. coli were highly prevalent in broilers of both countries. The percentage of samples with ESBL- and CiproR-E. coli was lower in pig compared to poultry farms and varied between farms. No clear association with the on-farm antibiotic use in the year preceding sampling was observed. Multidrug resistance was frequently observed in samples from both countries, but ESBL-production in combination with ciprofloxacin resistance was higher in samples from Belgium. Conclusions. This study demonstrated marked differences in antibiotic resistance between countries, farms and within farms. The observed variation cannot be explained straightforward by prior quantity of antibiotic use suggesting that it results from more complex interactions that warrant further investigation.
- 4 August 2021
- Published by MDPI AG in Antibiotics
- Vol. 10 (8) , 945
Open AccessESBL-Producing, Carbapenem- and Ciprofloxacin-Resistant Escherichia coli in Belgian and Dutch Broiler and Pig Farms: A Cross-Sectional and Cross-Border Study
Background. The use of antibiotics in food production selects for resistant bacteria and may cause a threat to human and animal health. Belgium and the Netherlands have one of the highest densities of broilers and pigs in Europe, making active monitoring of antibiotic use and resistance in this region vital. Objectives. This study aimed to quantify ESBL-producing (ESBL-E. coli), carbapenem- and ciprofloxacin-resistant (CiproR) Escherichia coli in animal feces on broiler and pig farms with a history of high antibiotic use in Belgium and the Netherlands. Methods. A total of 779 broiler and 817 pig fecal samples, collected from 29 conventional broiler and 31 multiplier pig farms in the cross-border region of Belgium and the Netherlands, were screened for the presence of antibiotic-resistant E. coli using selective culturing. Results. Carbapenem-resistant E. coli were not detected. ESBL-E. coli were remarkably more prevalent in samples from Belgian than Dutch farms. However, CiproR-E. coli were highly prevalent in broilers of both countries. The percentage of samples with ESBL- and CiproR-E. coli was lower in pig compared to poultry farms and varied between farms. No clear association with the on-farm antibiotic use in the year preceding sampling was observed. Multidrug resistance was frequently observed in samples from both countries, but ESBL-production in combination with ciprofloxacin resistance was higher in samples from Belgium. Conclusions. This study demonstrated marked differences in antibiotic resistance between countries, farms and within farms. The observed variation cannot be explained straightforward by prior quantity of antibiotic use suggesting that it results from more complex interactions that warrant further investigation.
- Open Access
- 17 May 2021
- Published by MDPI AG in Antibiotics
- Vol. 10 (5) , 590
Coaching Belgian and Dutch Broiler Farmers Aimed at Antimicrobial Stewardship and Disease Prevention
A reduction in antimicrobial use (AMU) is needed to curb the increase in antimicrobial resistance in broiler production. Improvements in biosecurity can contribute to a lower incidence of disease and thereby lower the need for AMU. However, veterinary advice related to AMU reduction or biosecurity is often not complied with, and this has been linked to the attitudes of farmers. Behavior change promoted by coaching may facilitate uptake and compliance regarding veterinary advice. Thirty broiler farms in Belgium and the Netherlands with high AMU were included in this study for 13 months. For each farmer, the attitude towards AMU reduction was quantified using an adjusted Awareness, Desire, Knowledge, Ability, and Reinforcement (ADKAR®) change management model, and farm biosecurity was assessed with the Biocheck.UGent™ tool. Subsequently, farmers were coached to improve disease prevention and antimicrobial stewardship. After the individual coaching of farmers, there was a change in their attitudes regarding AMU, reflected by an increase in ADKAR® scores. Biosecurity levels improved by around 6% on average, and AMU was reduced by 7% on average without negative effects on performance parameters. Despite these improvements, no significant association could be found between higher ADKAR® scores and lower AMU. Further investigation into sociological models is needed as a tool to reduce AMU in livestock production.
- 17 May 2021
- Published by MDPI AG in Antibiotics
- Vol. 10 (5) , 590
Open AccessCoaching Belgian and Dutch Broiler Farmers Aimed at Antimicrobial Stewardship and Disease Prevention
A reduction in antimicrobial use (AMU) is needed to curb the increase in antimicrobial resistance in broiler production. Improvements in biosecurity can contribute to a lower incidence of disease and thereby lower the need for AMU. However, veterinary advice related to AMU reduction or biosecurity is often not complied with, and this has been linked to the attitudes of farmers. Behavior change promoted by coaching may facilitate uptake and compliance regarding veterinary advice. Thirty broiler farms in Belgium and the Netherlands with high AMU were included in this study for 13 months. For each farmer, the attitude towards AMU reduction was quantified using an adjusted Awareness, Desire, Knowledge, Ability, and Reinforcement (ADKAR®) change management model, and farm biosecurity was assessed with the Biocheck.UGent™ tool. Subsequently, farmers were coached to improve disease prevention and antimicrobial stewardship. After the individual coaching of farmers, there was a change in their attitudes regarding AMU, reflected by an increase in ADKAR® scores. Biosecurity levels improved by around 6% on average, and AMU was reduced by 7% on average without negative effects on performance parameters. Despite these improvements, no significant association could be found between higher ADKAR® scores and lower AMU. Further investigation into sociological models is needed as a tool to reduce AMU in livestock production.