Transboundary and Emerging Diseases

Soon after the beginning of the COVID-19 pandemic in early 2020, the Betacoronavirus SARS-CoV-2 infection of several mink farms breeding American minks (Neovison vison) for fur was detected in several countries of Europe. The risk of a new reservoir formation and of a reverse zoonosis from minks was then a major concern. The aim of this study was to investigate the four French mink farms for the circulation of SARS-CoV-2 at the end of 2020. The investigations took place during the slaughtering period thus facilitating different types of sampling (swabs and blood). In one of the four mink farms, 96.6% of serum samples were positive in SARS-CoV-2 ELISA coated with purified N protein recombinant antigen and 54 out of 162 (33%) pharyngo-tracheal swabs were positive by RT-qPCR. The genetic variability among 12 SARS-CoV-2 genomes sequenced in this farm indicated the co-circulation of several lineages at the time of sampling. All SARS-CoV-2 genomes detected were nested within the 20A clade (Nextclade), together with SARS-CoV-2 genomes from humans sampled at the same period. The percentage of SARS-CoV-2 seropositivity by ELISA varied between 0.5 and 1.2% in the three other farms. Interestingly, among these three farms, 11 pharyngo-tracheal swabs and 3 fecal pools from two farms were positive by end-point RT-PCR for an Alphacoronavirus highly similar to a mink coronavirus sequence observed in Danish farms in 2015. In addition, a mink Caliciviridae was identified in one of the two positive farms for Alphacoronavirus. The clinical impact of these unapparent viral infections is not known. The co-infection of SARS-CoV-2 with other viruses in mink farms could contribute to explain the diversity of clinical symptoms noted in different infected farms in Europe. In addition, the co-circulation of an Alphacoronavirus and SARS-CoV-2 within a mink farm would increase potentially the risk of viral recombination between alpha and betacoronaviruses already suggested in wild and domestic animals, as well as in humans. Author summaryFrance is not a country of major mink fur production. Following the SARS-CoV-2 contamination of mink farms in Denmark and the Netherlands, the question arose for the four French farms. The investigation conducted at the same time in the four farms revealed the contamination of one of them by a variant different from the one circulating at the same time in Denmark and the Netherlands mink farms. Investigation of three other farms free of SARS-CoV-2 contamination revealed the circulation of other viruses including a mink Alphacoronavirus and Caliciviridae, which could modify the symptomatology of SARS-CoV-2 infection in minks.

Human salmonellosis cases are often caused by Salmonella serovars Enteritidis and Typhimurium and a large percentage of Salmonella outbreaks is associated with the consumption of eggs and egg products. For this reason, many countries implemented general surveillance programmes for the detection and control of Salmonella on pullet and layer farms. The infection risk however varies between farms and the identification of risk factors for Salmonella infection may be used to improve the performance of these surveillance programmes. The aims of this study are therefore to determine 1) whether local farm density is a risk factor for the infection of pullet and layer farms by Salmonella Enteritidis and Typhimurium and 2) whether the sampling effort of surveillance programmes can be reduced by accounting for this risk factor, while still providing sufficient control of target serovars Enteritidis and Typhimurium. To assess the importance of local farm density as a risk factor, we fitted different transmission kernels to Israeli surveillance data during the period from June 2017 to April 2019. The analysis showed that the distance to infected farms significantly increases the infection risk by serovar Enteritidis within an approximately 4 km radius and by Typhimurium within an approximately 0.3 km radius. We subsequently used these kernels to derive a model for the between-farm R0 and used it to optimise a surveillance programme that subdivided layer farms into groups at low and at high risk of between-farm transmission based on the local farm density and allowed the sampling frequency to vary between these groups. In this design, the pullet farms were always sampled one week prior to pullet distribution. Our analysis showed that the risk-based surveillance programme was able to keep the between-farm R0 of serovars Enteritidis and Typhimurium below 1 for all pullet and layer farms, using a sampling effort that was reduced by 32% compared to the currently implemented surveillance programme in Israel. The results of our study therefore indicate that local farm density is an important risk factor for infection of pullet and layer farms by Salmonella Enteritridis and Typhimurium and can be used to improve the performance of surveillance programmes.

Herein, we report Borna disease virus 1 (BoDV-1) infection in seven wild European hedgehogs (Erinaceus europaeus) from an endemic area in Germany. BoDV-1 causes encephalitis with a fatality rate of more than 90% in domestic mammals and humans. Currently, the bicolored white-toothed shrew (Crocidura leucodon) is the only known reservoir host. As hedgehogs are distant relatives of shrews and often cared for by humans, the cases raise concern regarding a potential zoonotic risk. All of the hedgehogs that tested positive for BoDV-1 had succumbed to neurological disease and exhibited severe polio-predominant lymphoplasmohistiocytic meningoencephalitis. However, due to the detection of viral antigens in non-neural cells in one animal, it cannot be completely excluded that some infected hedgehogs shed the virus. Although direct BoDV-1 transmission is known to be inefficient, our results emphasize the necessity of hygiene measures when handling hedgehogs, especially those with neurological signs from BoDV-1-endemic regions.

Two samples positive for the same strain (2103CP) of human astrovirus (HAstV) were identified during an acute gastroenteritis outbreak in Beijing, China. A full genomic analysis showed that for both samples, open reading frame 1a (ORF1a) clustered with HAstV-1, whereas ORF1b and ORF2 clustered with HAstV-5. The recombination site was detected upstream of the region where ORF1a and ORF1b overlapped. Recombinant HAstV-5 strains were reported previously in China in 2013 and 2021. Our results indicate the need for continuous surveillance of the prevalence and evolution of this recombinant HAstV-5 in China.

BackgroundIn August 1995, necropsies on post-weaning piglets from the CA-CART farm in the province of Cartago, Costa Rica, revealed respiratory lesions, pleuritis, peritonitis, and arthritis. Skin lesions were also observed, progressing to scabs. A subsequent outbreak in 1996 prompted antibiotic administration. Mortality analysis from 1990 to 1995 showed no significant seasonal patterns, but yearly variations were noted. Piglets born in Costa Rica from imported gilts had a higher average mortality rate (10.65%) than the 8.11% mortality rate for piglets born from non-imported gilts and sows or imported sows (p = 0.002). MethodsIn March 1996, serum samples were sent for potential PRRS virus (PRRSV) diagnosis, and 10 PRRSV-2 ORF5 sequences collected during a prospective study from 2019-2021 were obtained from various locations in the country. In this article, we seek to investigate the evolutionary and spatio-temporal dynamics of PRRSV-2 in Costa Rica in the context of international swine movements using the phylodynamic framework integrated with the BEAST package. Results and DiscussionThe phylodynamic modeling estimated at least two independent PRRSV-2 introductions into the country. The earliest introduction occurred around 1978 (95% highest posterior density interval: 1959.01-1997.54) and led to the viruses circulating in the farm 1CRC with an origin from Japan, possibly via US swine exports. A second cluster, 4CRC, subsequently emerged within Costa Rica from the earlier 1CRC lineage (1990.24; 95% HPD interval = 1976.15-2010.30). Another viral introduction from the US occurred around 1991 (95% highest posterior density interval: 1974.34-2011.35) and established the 3CRC cluster. Though the viral introduction was traced back to the US, the limited genomic surveillance of PRRSV leaves room for considering alternative origins. ConclusionOur findings provide a high-resolution model of how international swine trade drives the introduction and evolution of a major livestock pathogen, highlighting the critical need for integrating genomic surveillance into biosecurity protocols.

The emergence of highly pathogenic avian influenza A H5N1 in dairy cattle raises many questions related to animal health and changes to the risk of an epidemic in humans. We synthesized information currently published to fit a compartment model of H5N1 transmission within a dairy herd. An accompanying web application allows users to run simulations for specific outbreak scenarios. We estimated R0 near 1.2 with a short duration of infectiousness and fast time course of an epidemic within a farm, which we discuss in the context of possible on-farm control strategies. The web application allows users to simulate consequences of an epidemic using herd-specific information, a tool we propose will help inform stakeholders about potential consequences of uncontrolled H5N1 spread. Our modeling work has identified several key information gaps that would strengthen our understanding and control of this emerging infectious disease.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect many animals, including pets such as dogs and cats. Many studies have documented infection in companion animals by bio-molecular and serological methods. However, only a few have compared seroprevalence in cats and dogs from the general population, and these studies were limited by small sample sizes and collections over short periods. Our goal was to obtain a more accurate evaluation of seroprevalence in companion animals in France and to determine whether cats and dogs differ in their exposure to SARS-CoV-2. For this purpose, we conducted an extensive SARS-CoV-2 cross-sectional serological survey of 2036 cats and 3577 dogs sampled by veterinarians during medical examinations in clinics throughout France. Sampling was carried out from October 2020 through June 2021, a period encompassing the second and third waves of SARS-CoV-2 infections in humans in the country. Using a microsphere immunoassay targeting the receptor binding domain and trimeric spike protein, we found 7.1% seroprevalence in pets. In a subset of 308 seropositive samples, 26.3% had neutralizing antibodies. We found that cats were significantly more likely to test positive than dogs, with seropositivity rates of 9.3% and 5.9% in cats and dogs, respectively. Finally, data for both species showed that seroprevalence was lower in older animals and was not associated with the date of sampling or the sex of the animal. Our results show that cats are significantly more sensitive to SARS-CoV-2 than dogs, in line with experimental studies. Our large sample size provides for a reliable, statistically robust estimate of the frequency of infection of pets from their owners and offers strong support for the notion that cats are more sensitive to SARS-CoV-2 than dogs. Our findings emphasise the importance of a One-Health approach to the SARS-CoV-2 pandemic and raise the question of whether companion animals in close contact with humans should be vaccinated.

BackgroundFor a successful control of highly pathogenic avian influenza virus (HPAIV) epidemics in poultry, early detection is key and it is mostly dependent on the farmers prompt identification of disease and reporting suspicions. The latter could be further improved by providing references to farmers for triggering suspicions. MethodsHere we report observations on clinical signs of HPAIV H5N1 and H5N8 infected broiler farms in the Netherlands and analyze their daily mortality and feed and water intake data in order to identify thresholds for reporting suspicions. In addition, mortality data was used to characterize the transmissibility of these viruses, which could help estimate how fast infection spreads within the flock and when infection was likely introduced. ResultsThe most frequently observed clinical signs in affected flocks were sudden increase in mortality, cyanosis of wattles comb and/or legs and hemorrhagic conjunctiva. Analysis of mortality data indicate that daily mortality higher than 0.17% is an effective threshold for reporting a HPAIV-suspicion. Reliable thresholds for food or water intake could not be stablished. The estimated within-flock transmission rates ranged from 1.1 to 2.0 infections caused by one infectious broiler chicken per day. ConclusionsWe identified effective mortality thresholds for reporting suspicions of HPAIV infections. The estimated transmission rates appear to indicate a slow progression of a H5 HPAIV outbreak in affected broiler flocks. The information here provided can be used to improve syndromic surveillance and guide outbreak response.

In April 2020, respiratory disease and increased mortality were observed in farmed mink on two farms in the Netherlands. In both farms, at least one worker had been found positive for SARS-CoV-2. Necropsies of the mink revealed interstitial pneumonia, and organ and swab samples tested positive for SARS-CoV-2 RNA by qPCR. Variations in viral genomes point at between-mink transmission on the farms and lack of infection link between the farms. Inhalable dust in the mink houses contained viral RNA, indicating possible exposure of workers.

With high risk of sustained transmission and substantial associated morbidity, Lumpy Skin Disease (LSD) of cattle presents a major emerging threat to bovine herds worldwide, and has the potential to cause huge losses for farmers, producers, and the wider bovine and dairy trade industries. The epidemic which started in June 2025 in France illustrates this threat, as the government-imposed mass culling strategy has led to protests by farmers and social unrest throughout the country. Here, we developed an infectious disease modelling framework for evaluating different intervention strategies in an effort to critically evaluate the evidence behind the drastic measures being taken. By simulating epidemics under different response settings, we found that control strategies employing targeted culling were essentially as effective as those requiring mass culling, and did not require significantly more vaccination. These results question the response strategy currently imposed by the French government, and suggest avenues for alternative response strategies which could gain better support from the affected communities. Our results are entirely reproducible using a new free, open-source simulation tool which can be used for further evaluation of public health interventions against LSD epidemics.

The continuous spread of highly pathogenic avian influenza H5 viruses poses significant challenges, particularly in regions with high poultry farm densities where conventional control measures are less effective. Using phylogeographic and phylodynamic tools, we analysed virus spread in Southwestern France in 2020-21, a region with recurrent outbreaks. Following a single introduction, the virus spread regionally, mostly affecting duck farms, peaking in mid-December with a velocity of 27.8 km/week and an effective reproduction number between farms (Re) of 3.8, suggesting the virus can spread beyond current control radii. Transmission declined after late December following preventive culling. Farm infectiousness was estimated around 9 days. Duck farm density was the main driver of virus spread and we identified farm density and proximity thresholds required to maintain effective control (Re < 1). These findings offer actionable guidance to support regional biosecurity and to improve the robustness of the poultry sector to mitigate future outbreaks.

In 2020, African swine fever (ASF) was first notified in German wild boar, reaching a case number of about 4200 to date. Upon experimental infection, pathology is well-documented, however, data on field infections are very scarce in domestic pigs and not available from wild boar, respectively. Although ASF viral genome is considered exceptionally stable, a total of five lineages with 10 distinct virus variants of genotype II have emerged in Eastern Germany. To investigate the pathology in naturally infected wild boar and to evaluate virus variants II, III and IV for their virulence, wild boar carcasses were obtained from three different outbreak areas. The cadavers underwent virological and pathomorphological investigation. Regardless of the virus variant all wild boar revealed characteristic lesions of highest severity indicative for ASF. However, wild boar infected with variant IV from Spree-Nei{beta}e (SN) district showed lower viral genome loads and a lower total viral antigen score, but simultaneously revealed more chronic lesions. Our findings indicate a protracted course of the disease at least after infection with variant IV, but need confirmation under standardized experimental conditions. There is a strong need to monitor differences in the virulence among variants to identify potential attenuation that might complicate diagnosis.

BackgroundLyme borreliosis and tick-borne encephalitis (TBE) are tick-borne zoonoses of public health importance, transmitted in Western Europe by the same tick vector Ixodes ricinus. Roe deer (Capreolus capreolus) is a widespread feeding host for I. ricinus stages. Here, we explored the spatial extent of both pathogens in the wild in Northern France by assessing serological status in roe deer. MethodsWe collected 3,147 blood samples (2019-2022), and searched antibodies against both pathogens using ELISA tests. We fitted logistic models to investigate exposure to both or either pathogens, and explored spatial patterns using Kulldorf clustering scan tests. ResultsThe overall ELISA IgG prevalence was 23.24% (95%CI [21.77-34.72]) for Borrelia and 8.64% (95%CI [7.45-9.86]) for TBEV. The median Borrelia seroprevalence varied from 4% to 42% between departments, with two high-risk clusters of exposure identified. TBEV seroprevalence did not show any spatial pattern, and positives by seroneutralisation tests were reported in eight departments. DiscussionOur findings suggest the presence of both pathogens over large areas. Wider spatial sampling including areas at lower risk and improved serological methods would be beneficial to further validate those estimates.

Chlamydia pecorum is a globally endemic livestock pathogen but prevalence data from Switzerland has so far been limited. The present longitudinal study aimed to get an insight into the C. pecorum prevalence in Swiss cattle and investigated infection dynamics. The study population consisted of a bovine herd (n = 308) located on a farm in the north-eastern part of Switzerland. The herd comprised dairy cows, beef cattle and calves all sampled up to five times over a one-year period. At each sampling timepoint, rectal and conjunctival swabs were collected resulting in 782 samples per localization (total n = 1564). Chlamydiaceae screening was performed initially, followed by C. pecorum-specific real-time qPCR on all samples. For C. pecorum-positive samples, bacterial loads were determined. During this study, C. pecorum was the only chlamydial species found. Animal prevalences included 5.2%-11.4%, 38.1%-61.5% and 55%-100% in dairy cows, beef cattle and calves, respectively. In all categories, the number of C. pecorum-positive samples was higher in conjunctival (n = 151) compared to rectal samples (n = 65), however, the average rectal load was higher. At a younger age, the chlamydial prevalence and the mean bacterial loads were significantly higher. Of all sampled bovines, only 9.4% (29/308) were high shedders (number of copies per {micro}l >1000). Calves, which tested positive multiple times, either failed to eliminate the pathogen between sampling timepoints or were reinfected, whereas dairy cows were mostly only positive at one timepoint. In conclusion, C. pecorum was found in healthy Swiss cattle. Our observations suggested that infection takes place at an early age and immunity might develop over time. Although the gastrointestinal tract is supposed to be the main infection site, C. pecorum was not present in rectal samples from dairy cows.

Chronic wasting disease (CWD) is a contagious neural prion-disease affecting deer populations in North America with severe ecological and societal consequences. CWD is fatal and infectious prions spread and remain in the environment for many years even without animals present. The recent appearance of CWD in reindeers in Norway called for a drastic culling operation to prevent further spreading of the disease. This appears to have stopped the spreading of CWD among reindeers, but due to the persistence of CWD prions in the environment a reappearance of new cases among reindeer or other species in the future cannot be excluded. To evaluate the risks and the effectiveness of alternative management (monitoring and culling) options, we developed a model of CWD dynamics and management. The model includes stochastic population and spatial dynamics of the four relevant deer species in northern Sweden and Norway: reindeer (Rangifer tarandus), roe deer (Capreolus capreolus), red deer (Cervus elaphus) and moose (Alces alces). Transmission of CWD is modelled via direct contacts and via the environment. The model was parameterized and calibrated based on CWD studies from USA, data from the Norwegian CWD cases, and local deer population and vegetation data. The results indicate that without management, a CWD epidemic can be initiated by a single infected reindeer and would spread to other deer species. It would lead to dramatic population declines of reindeer and red deer and would also reduce the populations of roe deer and moose. The disease prevalence would stabilise at a about 50% after 50 years, as observed in some areas in the USA. A management strategy to cull only visibly sick animals, even with very efficient detection, cannot prevent a catastrophic development but merely slow the outbreak. To prevent an outbreak and the establishment of CWD it is necessary to cull all individuals, not only visibly sick ones, of an affected species in a relatively large area (30x30 km in our model) once a case is detected. Further, to prevent a slow buildup of CWD in the environment and eliminate the risk of outbreaks in the future it is necessary to expand this area of culling even further. Although the model has not yet been thoroughly validated due to scarcity of data, the results suggest that the drastic culling done in Norway was appropriate and necessary to prevent establishment of CWD and that further monitoring and potential culling is required to prevent outbreaks in the future.

Equine herpesvirus myeloencephalopathy (EHM) caused by equine herpesvirus type 1 (EHV-1) is a major threat to the equine industry because of its devastatating impact on animal welfare and performance. A specific single nucleotide polymorphism (SNP) (G2254/D752) in the EHV-1 ORF30 gene encoding DNA polymerase was previously shown to be a marker of the strain of EHV-1 that causes EHM. However, the effect of this SNP has never been resolved. Clinical findings indicated that fever and higher viremia levels are associated with the onset of EHM. No studies have examined EHV-1 growth at elevated temperatures so far. We found that EHV-1 with the D752 SNP replicated at elevated temperatures, and EHV-1 without it did not. We also found that EHV-1s isolated from horses with EHM could grow at elevated temperatures and most non-EHM isolates were suppressed by elevated temperatures. EHV-1s that can replicate at elevated temperatures have this SNP or one other SNP in ORF30. This appears to be the first report to show an association between EHM and the ability of EHV-1 to grow at elevated temperatures. (177 words) ImportanceEquine herpesvirus myeloencephalopathy (EHM) caused by equine herpesvirus type 1 (EHV-1) is a major threat to the equine industry because of its impact on animal welfare and performance. A specific single nucleotide polymorphism (SNP) (G2254/D752) in EHV-1 ORF30 gene encoding DNA polymerase (UL30) was previously shown to be a marker of EHM. However, the effect of this SNP has never been resolved. Here we show that this and one other SNP in UL30 are associated with replication capacity at elevated temperatures. (81 words)

Since March 2024, HPAI H5N1 virus has infected dairy cattle in the U.S., prompting concern about novel transmission routes. During an outbreak in California, HPAI H5N1 RNA was detected in an asymptomatic bulls semen. Although infectious virus was not isolated, questions remain about semen-associated transmission risks and biosecurity practices.

The outbreak and propagation of COVID-19 have posed a significant challenge to our society, highlighting the relevance of epidemiological monitoring of animal pathogens closely related to humans due to potential zoonosis. To find previously undetected viruses inside Chilean swine farms, we collected non-invasive samples from animals suspected to undergo any viral disease. After screening by Next Generation Sequencing (NGS) adapted to identify viral species with RNA and DNA genomes simultaneously, different viral species were successfully detected. Among viruses with an RNA genome, Porcine Rotavirus A (RVA), Porcine Astrovirus type 5 (PAstV-5) and Porcine Feces-Associated IASV-like virus (PfaIV) were identified; whereas among viruses with DNA genome, Porcine Parvovirus 1 (PPV1), Porcine Circovirus type 1 (PCV1) and Porcine Circovirus type 3 (PCV3) were found. PCV3, a recently described pathogenic virus, was detected for the first time in Chile in different samples from mummified tissue of stillbirths. The whole genome sequence of PCV3 was completed using conventional PCR and Sanger sequencing and compared with previously reported genomes. To the best of our knowledge, this is the first time that an adapted NGS system is used for the screening of DNA and RNA viral species simultaneously inside the Chilean swine industry. This adapted NGS system might be useful for the detection of swine viral emerging diseases worldwide.

Dippity Pig Syndrome (DPS) is a well-known but rare complex of clinical signs affecting minipigs, which has not been thoroughly investigated yet. Clinically affected animals show acute appearance of red, exudating lesions across the spine. The lesions are painful, evidenced by arching of the back (dipping), and the onset of clinical symptoms is generally sudden. In order to understand the pathogenesis, histological and virological investigations were performed in affected and unaffected Gottingen Minipigs (GoMPs). The following DNA viruses were screened for using PCR-based methods: Porcine cytomegalovirus (PCMV), which is a porcine roseolovirus (PCMV/PRV), porcine lymphotropic herpesviruses (PLHV-1, PLHV-2, PLHV-3), porcine circoviruses (PCV1, PCV2, PCV3, PCV4), porcine parvovirus 1 (PPV1), and Torque Teno sus virus (TTSuV1, TTSuV2). Screening was also performed for integrated porcine endogenous retroviruses (PERV-A, PERV-B, PERV-C) and recombinant PERV-A/C and their expression as well as for the RNA viruses hepatitis E virus (HEV) and SARS-CoV-2. Eight clinically affected and one unaffected GoMPs were analyzed. Additional unaffected minipigs had been analyzed in the past. The analyzed GoMPs contained PERV-A and PERV-B integrated in the genome, which are present in all pigs and PERV-C, which is present in most, but not all pigs. In one affected GoMPs recombinant PERV-A/C was detected in blood. In this animal a very high expression of PERV mRNA was observed. PCMV/PRV was found in three affected animals, PCV1 was found in three animals with DPS and in the healthy minipig, and PCV3 was detected in two animals with DPS and in the unaffected minipig. Most importantly, in one animal only PLHV-3 was detected. It was found in the affected and unaffected skin, and in other organs. Unfortunately, PLHV-3 could not be studied in all other affected minipigs. None of the other viruses were detected and using electron microscopy, no virus particles were found in the affected skin. This data identified some virus infections in GoMPs with DPS and assign a special role to PLHV-3. Since PCMV/PRV, PCV1, PCV3 and PLHV-3 were also found in unaffected animals, a multifactorial cause of DPS is suggested. However, elimination of the viruses from GoMPs may prevent DPS.

Streptococcus suis is a major cause of respiratory and systemic diseases in post-weaned pigs, leading to significant production losses and animal welfare concerns. This study provides the first long-term national level analysis of Streptococcus suis-associated disease (SSAD) in the Republic of Ireland. We examined the pig diagnostic submissions, characterised serotype distribution, antimicrobial susceptibility, and co-infection patterns from 2010 to 2024. The findings confirm that serotypes 9 and 2 or 1/2 were most frequently associated with disease. We observed a significant shift in recent years where serotype 9 has surpassed serotype 2 or 1/2 in number of occurrences. S. suis was frequently co-detected with viral pathogens including porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2, and swine influenza virus (SIV), as well as bacterial pathogens such as Actinobacillus pleuropneumonia and Pasteurella multocida, typically from pneumonic lungs. While resistance to tetracycline and erythromycin was high (44.4% to 65.8%), isolates remained susceptible to first-line beta-lactam antibiotics such as penicillin (7.9% resistance), ampicillin (5.5% resistance) and amoxycillin/clavulanate (0% resistance). The observed heterogeneity between and within herds challenges successful implementation of vaccination and highlights the need for ongoing disease monitoring. These findings provide the first in-depth assessment of SSAD in Irelands pig population which will offer valuable insights for future surveillance efforts, including genomic studies and supporting evidence-based strategies and vaccine selection for controlling S. suis in Irish pig sector.