Interstitial pneumonia in swine is an important respiratory condition in which inflammation and thickening of the pulmonary interstitium result in impaired gas exchange and respiratory distress. The multifactorial etiology of the disease includes viral, bacterial, and parasitic pathogens, as well as environmental or toxic insults. Clinical signs range from acute respiratory distress and fever to chronic weight loss and reduced growth performance, contributing to economic losses due to decreased productivity and increased mortality. Pathogenesis typically begins with a primary insult, commonly viral infection, septicemia, parasitic migration, or toxic exposure, triggering inflammation and immune cell infiltration within the lung parenchyma. This process may progress to alveolar septal thickening and impaired pulmonary function. Gross lesions vary depending on the etiologic agent and chronicity, ranging from rubbery-to-firm lungs that appear bright-red to tan with a patchy, lobular, or diffuse distribution. Histologically, lesions include interstitial septal thickening, mononuclear inflammatory cell infiltration, and type II pneumocyte hyperplasia. Several infectious agents are associated with interstitial pneumonia. Viral pathogens such as porcine reproductive and respiratory syndrome virus, porcine circovirus 2, swine influenza A virus, porcine parainfluenza virus, porcine hemagglutinating encephalomyelitis virus, and porcine astrovirus 4 may induce interstitial or bronchointerstitial pneumonia. Bacterial pathogens such as Escherichia coli, Actinobacillus suis, Streptococcus suis, and Erysipelothrix rhusiopathiae, and parasites including Ascaris suum and Metastrongylus spp., may contribute through septicemia or larval migration. Accurate diagnosis requires integration of gross and histopathologic findings with ancillary techniques such as PCR, immunohistochemistry, and in situ hybridization.

F18 enterotoxigenic Escherichia coli (ETEC) causes post-weaning diarrhea in nursery pigs, with susceptibility determined by a polymorphism in the α(1,2)-fucosyltransferase (FUT1) gene at nucleotide M307, where FUT1-M307A/A pigs are deemed F18 resistant and FUT1-M307G/A and FUT1-M307G/G pigs are deemed F18 susceptible to bacterial attachment. This post hoc analysis evaluated the effect of FUT1 genotype on disease susceptibility following F18 ETEC challenge over 3 experiments. It was hypothesized that FUT1 susceptible pigs (G/G and G/A) would incur greater F18 attachment than FUT1 resistant pigs (A/A). In Exp. 1 and 2, 194 pigs (5.79 ± 1.02 kg BW; 12% FUT1-M307G/G, 52% FUT1-M307G/A, 36% FUT1-M307A/A) were allocated to pens (6 pigs/pen), and half were orally inoculated with ∼1 × 109 CFU/mL F18 ETEC on d 10 (d-post infection [dpi] 0). Individual pig body weights (BW) were recorded on dpi -10, 0, 5, 12, and 28 to calculate growth rates. In Exp. 3, 18 individually housed pigs (5.68 ± 0.51 kg BW; 6% FUT1-M307G/G, 65% FUT1-M307G/A, 29% FUT1-M307A/A) were inoculated on d 10 (dpi 0) with ∼1 × 107-109 CFU/mL and euthanized at dpi 5 for collection of ileal tissue and digesta to evaluate ileal F18 ETEC attachment, cystic fibrosis transmembrane conductance regulator (CFTR) abundance, and F18 gene abundance. From dpi 0 to 5, growth rates were reduced by 58.9% and 62.2% in FUT1-M307G/A and FUT1-M307G/G pigs, respectively, compared with unchallenged controls, whereas FUT1-M307A/A pigs growth rates were unaffected (P < 0.0001). Over the entire post-infection period (dpi 0-28), growth rate and mortality did not differ between genotypes or F18 ETEC challenge (P > 0.10). Ileal F18 attachment tended to be greatest in G/G pigs compared with G/A and A/A pigs (2.6%, 1.2%, 0.1, respectively; P < 0.10). Ileal CFTR abundance was greater in G/G relative to G/A and A/A pigs (3.1%, 1.1%, 0.3%, respectively; P < 0.05). Ileal F18 gene abundance tended to be highest in G/G pigs (21.7) compared with G/A (18.0) and A/A (12.7) pigs (P < 0.10). In conclusion, FUT1 genetic polymorphisms G/G and G/A can increase susceptibility to F18 ETEC infection, warranting further investigation into interactions with other intestinal microbes, and representing a promising target for genetic selection.

Abstract Zinc oxide at pharmacological concentrations can enhance nursery pig growth performance, improve intestinal health, and reduce post-weaning diarrhea. However, the mechanisms underlying these benefits remain unclear. This study investigated the mode of action by which zinc oxide improves intestinal health and growth performance in nursery pigs challenged with F18 enterotoxigenic Escherichia coli (ETEC). A total of 196 newly weaned pigs [Camborough 1050 × 337 (PIC, Hendersonville, TN)] were utilized in a 2x2 factorial design consisting of corn–soybean meal diets containing either 120 ppm zinc (CON) or 3,000 ppm zinc from zinc oxide (ZNO), and non-challenged (NC; 6.11 ± 1.0 kg BW) or F18 ETEC-challenged (ETEC; 6.08 ± 1.1 kg BW). Pens were balanced for α-(1,2) fucosyltransferase (FUT1) genotype and randomly assigned to diets. Feed was provided ad libitum in two phases (10 and 28 days). On day 10 [day post-inoculation (dpi) 0], ETEC pens were orally inoculated with 5 mL of a 2.2 × 109 cfu/mL F18 ETEC culture. Pig BW and feed disappearance were recorded on dpi -10, 0, 5, 7, 12, 19, and 28 to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). Pooled pen fecal dry matter (DM) and F18 and LT gene abundance (qPCR) were measured on dpi –1, 3, 5, 7, 9, 11, 14, and 20. On dpi 5 and 7, one FUT1 heterozygous (A/G) pig per pen was euthanized and fixed ileal tissues were evaluated for histomorphology and F18 attachment (in situ hybridization). Pen served as the experimental unit, and data were analyzed for main effects and interactions of diet and ETEC challenge, with room included as a random effect. During the pre-inoculation period (dpi –10 to 0), ZNO pigs had greater ADG (P = 0.015) and ADFI (P = 0.036) compared with CON, while G:F was not affected. At dpi 28, ETEC-CON pigs had lower BW compared with ETEC-ZNO (18.6 vs. 22.9 kg; P = 0.007). Overall (dpi –10 to 28), a diet by challenge interaction was observed where ETEC-CON pigs exhibited reduced ADG compared to ETEC-ZNO (0.32 vs. 0.44 kg/d; P = 0.001). At dpi 5, ileal F18 ETEC attachment was greater in the ETEC-CON pigs than ETEC-ZNO, NC-CON, and NC-ZNO (0.03%, 0.02%, and 0.06%, respectively; P = 0.012). By dpi 7, ileal F18 attachment remained higher in ETEC pigs than NC (P = 0.001), but the overall magnitude of staining was reduced compared with dpi 5. Fecal consistency improved from dpi –1 to 20, with fecal DM tending to be lower in ETEC-CON pens compared with all other treatments (P = 0.089). Overall, a major mode of action was zinc oxide’s ability to reduce F18 ETEC adherence to the intestinal epithelium. Subsequently, pharmacological ZNO improved growth performance and fecal consistency in the presence of an ETEC challenge.

Swine producers frequently encounter polymicrobial disease challenges, with co-infections exacerbating clinical disease and complicating response strategies. This study aimed to characterize co-diagnosis patterns in swine by integrating confirmed diagnosis cases using a standardize diagnosis system (Dx code) from the Iowa State University Veterinary Diagnostic Laboratory. As a secondary objective, the study developed the concept and implemented a framework for the technological transfer of the Dx code system from ISU-VDL to the Ohio Animal Disease Diagnostic Laboratory, and to gather Dx code data through an animal disease monitoring program, thereby creating a multi-institutional, confirmed tissue disease diagnosis database. The final collated database was harmonized and used to analyze 45,310 confirmed tissue diagnosis cases submitted between 2020 and 2025. Co-diagnosis was defined as the presence of two or more distinct etiologies within a single case. Overall, 52.62

Soybean-derived trypsin inhibitor proteins (TIU) impair amino acid bioavailability and increase exogenous and endogenous nitrogen flow to the hindgut, thereby attenuating pig growth performance. High-protein diets potentiate proteolytic fermentation-induced alterations to the gut microbiome, which may increase opportunistic enterotoxigenic Escherichia coli (ETEC) proliferation and exacerbate disease. We hypothesized that feeding high-TIU diets to nursery pigs would reduce growth rates and exacerbate F18 ETEC disease. Two hundred and eighty-eight (5.42 ± 0.93 kg BW; Camborough 1050 × 337, [PIC, Hendersonville, TN]) newly weaned pigs were evenly allotted across two control rooms (CON) and two challenge rooms (ETEC). Pigs were allotted based on sex and α-(1,2) fucosyltransferase (FUT1) genotype, with both factors evenly distributed across all pens. Pens were randomly assigned to corn-soy diets consisting of 1.1, 2.4, or 4.2 TIU/mg, creating six treatments: CON1.1, CON2.4, CON4.2, ETEC1.1, ETEC2.4, and ETEC4.2 (8 pens/treatment). On day 10 (day post-infection [dpi] 0), pigs in the ETEC rooms were orally inoculated with 5 mL of 3.8 × 109 cfu/mL of an F18 ETEC culture. Pooled pen feces were assessed for dry matter (DM) on dpi 0, 3, 5, 7, 9, 11, 14, and 21. Pen growth performance, medical treatments, and mortality were assessed prior to infection (dpi -10 to 0) and post infection (dpi 0 to 28). On dpi 5 and 12, one pig/pen was sacrificed to assess ileal mucosal attachment of F18 ETEC via in situ hybridization. Pen was the experimental unit and data were analyzed for the interactive and main effects of diet and challenge. Increasing dietary TIU to 4.2 TIU/mg led to a 13-16% decrease in ADG compared to the 1.1 TIU/mg diets, regardless of the challenge (P = 0.014). A diet × challenge interaction was observed regarding mortality, with ETEC2.4 showing a 20.8% mortality rate compared to 0% in CON2.4 (P = 0.001). Similarly, 22.9% of ETEC2.4 pigs required antibiotic treatment compared with 0% of CON2.4 pigs (P = 0.001). Fecal DM from dpi 0-21 showed no interaction, but ETEC pens had lower fecal DM compared to CON pens from dpi 3-11 (P < 0.0001). On dpi 5, ileal F18 attachment was increased in ETEC versus CON pigs (3.7 × 10-3 vs 0.1 × 10-3 F18 copies/μm2, P < 0.0001). By dpi 12, ileal F18 attachment did not differ between challenge groups (P > 0.05), suggesting disease resolution. In conclusion, diets at or greater than 2.4 TIU/mg decreased pig growth and reduced livability in ETEC-infected nursery pigs.

Global pork production has increased substantially over the past few decades, making swine a critical source of animal protein. However, endemic diseases in pigs continue to pose significant challenges to animal health, productivity, and food security. Several etiologies affect farm-level performance and have broader implications for zoonotic risks and public health. Many diagnostic cases are submitted to veterinary diagnostic laboratories, and their aggregation can yield insights into etiological activity. Therefore, this study aimed to develop a composite etiology index using confirmed tissue diagnosis data from the Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL) to assess endemic etiology activity across the United States. A total of 59,950 porcine tissue cases from 2020 to 2024 were analyzed, focusing on 81 etiologies of bacterial, viral, parasitic, and metabolic/intoxication origin. Four normalized variables: disease occurrence, codiagnosis, state occurrence, and Early Aberration Reporting System (EARS) alarms were integrated using the CompidexR package to generate a weighted index ranging from 0.01 to 1. Temporal consistency was evaluated using the Manhattan distance, Spearman's correlation, and the Wilcoxon signed-rank test. Also, a bootstrap resampling method was developed to detect anomalies in the distribution of etiologies. The index demonstrated strong year-over-year stability, with porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis consistently receiving yearly highest scores. Reemerging viruses like porcine sapovirus (PSaV) and astrovirus (AsV) showed notable increases in index values, reflecting rising diagnostic activity and geographic spread. Bootstrap analysis showed that over 55% of etiologies fell within expected confidence intervals (CIs) and had low root mean square errors (RMSEs), detecting anomalies such as PCV2 occurrences in 2024. The index summaries were visualized through an interactive Power BI dashboard, enabling dynamic exploration of etiology trends. This framework offers a scalable, reproducible tool for monitoring endemic swine diseases using routine diagnostic data. The ability to generate information on endemic etiology rankings can support decision-makers with evidence-based disease management and control. The developed model has flexibility and can be adapted to other species and disease systems. The index provided a robust foundation for enhancing surveillance of endemic pathogens in swine populations.

Clostridioides difficile infection (CDI) is a toxin-mediated gastro-intestinal disease. Yet, C. difficile is a phylogenetically diverse species that includes many non-toxigenic strains. In general, these are understudied, despite having significant potential impact for our understanding of the colonization process and as therapeutic modalities. Here, we present an in-depth characterization—including the complete genome sequence—of the non-toxigenic C. difficile strain L-NTCD03. This strain belongs to PCR ribotype 416, clade 4 and multilocus sequence type 39. It is resistant to multiple antimicrobials, but not those used for treatment of CDI. We validated the relevance of the cfr(B) gene from this strain in antimicrobial resistance to clindamycin, linezolid, retapamulin and streptogramin A. We found the L-NTCD03 strain to be non-toxic in various assays. Altogether, L-NTCD03 is a promising candidate for developing into a live biotherapeutic product.

Highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b virus was identified in 4 cull dairy cows condemned by the U.S. Department of Agriculture because of pneumonia with accompanying systemic changes. Histologic findings were bronchopneumonia in 3 cows and embolic pneumonia and nephritis in 1 cow. In addition to detection of HPAI A(H5N1) virus by reverse-transcription real-time PCR in various formalin-fixed, paraffin-embedded tissues, influenza A virus was detected by immunohistochemistry and in situ hybridization in the pulmonary respiratory epithelium of 2 of the cows with bronchopneumonia and in renal medullary tubules of the cow with nephritis. A PCR panel screening for common bovine respiratory pathogens in the cows with bronchopneumonia revealed variable coinfections with Histophilus somni, Pasteurella multocida, Mannheimia haemolytica, Mycoplasmopsis bovis, and bovine coronavirus. We describe the distribution of HPAI A(H5N1) virus in naturally infected cows while highlighting the need for research on the roles of coinfection and immune response in influenza viral replication.

Lawsonia intracellularis and its resulting disease remains a troubling pathogen for pork producers worldwide. In the current experiment, we aimed to characterize the microbiome of pigs challenged with L. intracellularis through peak disease impact to better understand microbial community function and how microbial changes may contribute to disease and resulting decreased growth. Twenty-four L. intracellularis negative barrows were assigned to either L. intracellularis negative (NC) or L. intracellularis challenged (PC) treatment groups (n = 12 pigs/treatment). On days post-inoculation (dpi) 0, PC pigs were inoculated with L. intracellularis. Feed disappearance was monitored daily, body weights and fecal samples were collected weekly. At dpi 21, pigs were euthanized for sample collection and macroscopic lesion scoring. Pigs challenged with L. intracellularis had sustained reductions in growth performance and feed intake throughout the 21-day period (P < 0.001). This was accompanied by changes to fecal microbial communities, particularly increased abundance of Chlamydia suis in challenged pigs at dpi 7, 14, and 21. Changes to microbial communities were also accompanied by differences in microbial metabolism, marked most notably by signatures of lesser amino acid biosynthesis and greater nucleotide synthesis in challenged pigs. In summary, L. intracellularis challenge produced reductions in growth and feed intake. This was accompanied by sustained changes to fecal microbial communities, particularly sustained increased abundance of C. suis in challenged pigs. Changes to microbial communities were also accompanied by differences in microbial metabolism which likely play a role disease.

Porcine Reproductive and Respiratory Syndrome (PRRS) virus reduces feed intake and growth rates and increases mortality risk in pigs. During this disease state, it is unclear if macronutrient and feed preferences change to support the immune response. Our objective was to evaluate how diet composition impacts feeding preferences during PRRS. In Exp. 1, pigs were offered a choice between a corn-soybean meal (CON) and a CON + 3.75% glucose and fructose high sugar (HS) diet. In Exp. 2, pigs were offered both CON and CON plus functional amino acids (10–20% increase in methionine, threonine, and tryptophan; FAA) diets. In Exp. 3, pigs were presented with CON, a high-protein diet (28% increase in CP; HCP), or a high-fat diet (20% increased metabolizable energy; ME) diets. Each experiment contained six pens of mixed-sex pigs (40 ± 5.5 kg) that were randomly allotted to pens (Exp. 1 and 2 contained three pigs/pen, Exp. 3 contained four pigs/pen). On day post inoculation (dpi) 0, one pig/pen was inoculated intramuscularly with a live PRRS virus. Body weights and feed disappearance were recorded weekly (-1 week post-inoculation [wpi] and at 1, 2, and 3 wpi) to calculate ADG, ADFI, and feed preference. Feed preference was expressed as the percentage of each tested diet relative to total feed intake. Data were analyzed using a linear mixed model with the fixed effect of wpi and wpi by diet. As expected, ADFI decreased (P< 0.001) in Exp. 1 (2.17, 2.27, 1.74 and 2.16 kg/d), Exp. 2 (2.10, 2.06, 1.62 and 1.92 kg/d), and Exp. 3 (1.64, 1.93, 1.53, and 1.96 kg/d) over wpi. In Exp. 1, ADG and G:F did not differ by wpi. Over the challenge period, ADG decreased by up to 50% (P< 0.05) in Exp. 2 and 3. In Exp. 2, G:F tended to decrease during 2 wpi compared to -1 and 1 wpi, recovering by 3 wpi (P=0.08), and did not differ for Exp. 3 (P=0.114). In Exp. 1, HS diets were preferred over CON in wpi -1 and 1 wpi (84% vs. 16%, respectively); however, by wpi 2 and 3, HS preference decreased to 55% compared to 45% for CON (P=0.015). Across all wpi, HS diets were preferred over CON (69% vs. 31%, P=0.001). In Exp. 2, no diet by wpi was reported. However, overall, the CON was preferred over FAA (63% and 37%, respectively, P=0.02). No wpi by diet interaction was reported in Exp. 3 (P=0.17). However, overall, the HCP and ME were preferred over CON (42, 36, and 22%, respectively, P=0.003). In conclusion, pigs prefer diets containing natural sweeteners, higher crude protein, or energy during peak PRRS. Further research is needed to determine if this is driven by olfactory or gustatory factors.

Weaning-associated enteric diseases are a major concern in the swine industry. This study investigates the effects of fecal microbiota transplantation (FMT) on the jejunum of weanling piglets, a segment of bowel less studied in terms of microbiomic changes despite its primary involvement in major post-weaning enteric diseases, including postweaning diarrhea (PWD). Thirty-two 3-week-old piglets were divided equally into two groups: Control and FMT. The FMT group received fecal microbiota preparation from 3-month-old healthy pigs on the 1st and 3rd day after weaning. Half of each group was inoculated with an enterotoxigenic E. coli (ETEC) isolate 10 days post-FMT. Piglets were euthanized in the third week (14th and 18th days post-FMT) after weaning to collect intestinal tissues and contents for microbiomic, metabolomic, and transcriptomic analyses. The jejunal microbiota showed a significant increase in alpha diversity in the third week post-FMT compared with the ileum and colon. FMT significantly enriched the jejunal microbiota composition, while multiple bacterial genera were specifically lacking in control weanling piglets. FMT was strongly associated with the enrichment of the genus Pseudoscardovia of the Bifidobacteriaceae family, which was found lacking in the jejunum of weanling control piglets and inversely associated with the abundance of the genus Bifidobacterium within the same family. Other genera associated with FMT included Solobacterium, Shuttleworthia, and Pseudoraminibacter, whereas bacteria such as Erysipelotrichaceae and Acidaminococcus were identified as most abundant in the control piglets. Metabolomic analysis revealed a significant modulatory effect of FMT on carbohydrate, amino acid, nucleotide, vitamin, and xenobiotic metabolisms, suggesting improved nutrient utilization. Transcriptomic analyses further confirmed the regulatory effects of FMT on gene expression associated with immune, metabolic, barrier, and neuroendocrine functions. Prior FMT treatment in the context of ETEC infection indicated a potential protective role, as evidenced by a significant shift in microbial diversity and metabolomic compositions and decreased diarrhea severity even though no effect on pathogen shedding was evident. This study underscores the promise of FMT in enhancing jejunal health. In addition, the results suggest that FMT could be considered a potential strategy to address conditions associated with small intestinal dysbiosis in swine and other monogastric species with similar gut anatomy and physiology, such as humans.

Enterotoxigenic Escherichia coli (ETEC) infection presents a major economic challenge to pig production, specifically post-weaning, and it is believed that dietary protein fermentation can exacerbate this infection. Due to the prevalence of soybean protein products in weanling pig diets and their inherent antinutritional compounds, such as active trypsin inhibitor protein, we hypothesized that increased active dietary trypsin inhibitor unit (TIU) intakes will exacerbate F18 ETEC disease in weanling pigs. Two hundred and eighty-eight [Camborough 1050 × 337, (PIC, Hendersonville, TN)] newly weaned pigs were equally allocated across two control rooms [CON; 5.37 ± 0.91 kg body weight (BW)] and two challenge rooms (ETEC; 5.42 ± 0.93 kg BW). Pigs were allotted based on sex and alpha-(1,2) fucosyltransferase (FUT1) genotype, with both factors evenly distributed among and within the pens and rooms. Pens were randomly assigned to one of three corn and soy-based dietary treatments, with TIU/mg in the complete feed of 1.1, 2.4, or 4.2, (8 pens/diet/challenge-group). Diets were isocaloric, isonitrogenous, and identical in standardized ileal digestible lysine and essential amino acid to lysine ratios, with treatments exceeding 1.1 TIU/mg replacing equivalent amounts of soybean meal with high-TIU soy flour to achieve desired TIU levels. All diets were provided ad libitum in two phases, lasting 10 and 28 days. On day 10, pigs in the ETEC rooms were drenched once with 5 ml of 3.8 log9 F18 ETEC culture. Pig BW and feed disappearance were recorded at the start and end of each phase to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F). Pooled pen fecal dry matter (DM) was assessed on day post-infection (dpi) 0, 3, 5, 7, 9, 11, 14, and 21 and treated as a repeated measure. Pen was the experimental unit and data were analyzed for main effects and interaction between diet and ETEC with room as a random effect. A diet and ETEC interaction was observed regarding mortality, with ETEC2.4 exhibiting a 20.8% mortality rate compared to 0% in CON2.4 (P=0.001). Pre-infection (dpi -10 to 0) performance measurements did not differ. Fecal DM from dpi 0-21 showed no interaction, but ETEC pens had lower fecal DM compared to CON pens from dpi 3-11 (P=0.049). Post-infection performance (dpi 0-28) observed no interaction between diet and ETEC (P>0.05). Overall (dpi -10 to 28), ETEC2.4 pigs had improved G:F (1.01 vs. 0.81, P=0.029) and reduced ADFI (0.42 vs. 0.55 kg, P=0.009) compared to CON2.4, although ADG and end BW remained statistically indifferent. Increasing dietary TIU to 4.2 TIU/mg led to a 13–16% decrease in ADG compared to the 1.1 TIU/mg diets, regardless of the challenge (P=0.014). In conclusion, increased dietary TIU may decrease weanling pig livability in ETEC-infected populations.

Post-weaning diarrhea (PWD) due to Escherichia coli in pigs is a significant enteric disease in the U.S. Contemporary data about the main virulence factors, colony morphology, and distribution of virotypes of isolates associated with post-weaning colibacillosis (PWC) is essential information for swine veterinarians, producers, and stakeholders. This study reports the rate of PWC/PWD, frequency of detection of fimbrial types, pathotypes, toxins, virotypes, morphological characteristics, and temporal analysis of the most prevalent virotype of enterotoxigenic E. coli recovered from cases of PWD in pigs in the United States. There was a significant increase in PWC cases submitted to the diagnostic laboratory in 2013, 2014, and 2021, respectively. A greater frequency of detection of F18 fimbrial adhesin (69.87%) was observed compared to F4 (26.19%), F5 (0.25%), F41 (0.13%), AIDA (0.10%), and multiple adhesins (3.46%), respectively. Hybrid ETEC:STEC pathotype was greater than ETEC and STEC, and STb toxin was present in 93.33% of the detected isolates. The most frequently observed virotype was F18:LT:STa:STb:Stx2e (27.71%). Smooth:mucoid colony morphology was associated with a greater likelihood of PWC (0.758, 0.968, and 0.993) compared to smooth, intermediate, and rough, respectively. The frequency of the F18:LT:STa:STb:Stx2e virotype increased across all U.S. states from 2016 to 2023, greatest in the northwest and east of Iowa and northeast Indiana in 2022 and Iowa in 2023. The virulence factors and morphology of enterotoxigenic E. coli associated with PWC across different states in the U.S. from 2010 to 2023 were diverse; nevertheless, the virotype F18:LT:STa:STb:Stx2e predominated and increased in frequency during this time period.

Swine dysentery, caused by the anaerobic spirochete Brachyspira hyodysenteriae, leads to mucohemorrhagic diarrhea in grower-finisher pigs, impacting swine production. Knowledge regarding its genomic epidemiology is limited. We performed a whole-genome sequence analysis for 251 B. hyodysenteriae genomes from 10 countries, including 117 isolates sequenced in this study. Phylogenomic analysis based on core-genome single nucleotide polymorphisms (SNPs) revealed nine lineages, with L7 (72 isolates, 28.69%), L9 (67 isolates, 26.69%), and L2 (53 isolates, 21.12%) predominating. Geographical clustering was observed with distinct lineage distributions. Multilocus sequence typing identified 69 sequence types (STs), including 20 novel STs across 251 genomes. Association between specific lineages, STs, and geographical regions was evident, highlighting evolutionary and regional patterns. The pan-genome analysis identified 5,231 genes, categorized into core (1,648), accessory (2,619), and unique (964) components. Functional annotation linked core genes to essential cellular processes, while accessory and unique genes were enriched in genetic variability, defense mechanisms, and secondary metabolism. The pan-genome exhibited a high proportion of hypothetical genes, necessitating further functional characterization. Antimicrobial resistance (AMR) screening detected the tva(A) and lnu(C) genes associated with tiamulin and lincomycin resistance, respectively, in specific lineages and STs. Virulence factor analysis identified genes linked to hemolysin production, iron uptake, and survival in host environments in most isolates, with a subset of genes demonstrating lineage-specific associations that are further linked to pathogenic potential. This comprehensive genomic epidemiological analysis elucidates the genetic diversity, antimicrobial resistance, and virulence of B. hyodysenteriae globally, enhancing understanding of its epidemiology and guiding interventions to mitigate swine dysentery. IMPORTANCE:Brachyspira hyodysenteriae, the primary causative agent of swine dysentery, remains a less-studied pathogen than other bacterial species that impact animal health. This study uses whole-genome sequencing and advanced phylogenomic approaches to reveal the genetic diversity and geographical distribution of B. hyodysenteriae isolates, focusing on U.S. populations. The identification of nine distinct phylogenetic lineages and associated sublineages highlights the pathogen's complex population structure and regional variation. Importantly, the study detects AMR genes, including tva(A) and lnu(C), linked to tiamulin and lincomycin resistance, that may pose significant challenges to disease management. The analysis also identifies virulence-associated genes, shedding light on molecular mechanisms underlying pathogenicity. By combining core-genome SNP phylogenies with multilocus sequence typing and accessory genome insights, this work provides a robust framework for a better understanding of B. hyodysenteriae evolution. Overall, these findings underscore the importance of genomic surveillance in informing control strategies and improving swine health worldwide.

Toxoplasma gondii is an important apicomplexan parasite in veterinary medicine, with swine prevalence varying due to age, geographic distribution, and production program. Samples from a 6-wk-old pig from a small backyard farm with multisystemic disease concerns were submitted to the Iowa State University-Veterinary Diagnostic Laboratory. Gross findings included severe necrotizing enteritis with pseudomembrane formation and edematous, non-collapsing lungs. Histologic findings were severe necrotizing enterocolitis and random multifocal pulmonary and hepatic necrosis with numerous intralesional protozoal cysts consistent with T. gondii. Immunohistochemistry, reverse-transcription real-time PCR (RT-rtPCR), and serologic tests were positive for T. gondii; concurrent influenza A virus, porcine reproductive and respiratory syndrome virus, porcine circovirus 2, African swine fever virus, and classical swine fever virus were ruled out by RT-rtPCR. Given the worldwide distribution and zoonotic potential of T. gondii, the possibility of infection in swine should be considered.

Trypsin inhibitor proteins are antinutritional compounds innate to soybeans that reduce protein digestibility, amino acid bioavailability, and growth performance of pigs. The objective of this study was to evaluate the impact of increasing levels of dietary trypsin inhibitor unit activity (TIU/mg) on nursery pig growth performance and health. In a 41-d study, 1,140 newly weaned nursery pigs (5.9 ± 0.34 kg BW) were allotted into split sex pens, blocked by body weight, assigned randomly to one of five dietary treatments (n = 19 pens/treatment) varying in TIU/mg concentration, and fed over three dietary phases. Treatments targeted 0.41, 1.32, 2.20, 3.08, and 3.96 TIU/mg of complete feed averaged over the three phases and were achieved by using a corn-soybean meal basal diet with added soybean flour. Analyzed dietary treatments averaged 0.61, 1.22, 2.19, 3.41, and 3.51 TIU/mg. Pen BW and feed disappearance were recorded at the start and end of each phase to calculate ADG, ADFI, and G:F. Fecal consistency was scored and recorded daily. On d 21 of the study, 10 pigs per treatment were sacrificed for intestinal sample collection. Data were analyzed with pen as the experimental unit, the random effect of block, and the fixed effect of TIU, including polynomial contrasts for linear and quadratic effects of 0.61 to 3.51 TIU/mg treatments. No quadratic responses to dietary TIU/mg activity were reported in any parameters. Overall, as active dietary TIU/mg increased, ADG, ADFI, and G:F linearly decreased (P < 0.001). Pigs fed the highest level (3.51 TIU/mg) exhibited reduced ADG by 25%, ADFI by 17%, and G:F by 8% compared to pigs fed the lowest level (0.61 TIU/mg). Dietary TIU/mg did not affect fecal consistency, mortality, or removals (P > 0.10). Individual and total concentrations of colonic biogenic amines and short chain fatty acids did not differ (P > 0.10). Histological lesions of the ileum and colon did not differ (P > 0.10). Ileum VH tended to decrease (P = 0.078) and CD linearly decreased as TIU/mg increased (P = 0.004), but VH:CD and colonic CD were similar (P > 0.10). Moderate relationships between TIU intake and G:F (R2 = 0.393), caloric efficiency (R2 = 0.378), and lysine efficiency (R2 = 0.376) were observed. In conclusion, soybean-derived active TIU concentrations negatively impact nursery pig performance above 1.22 TIU/mg, with minimal impacts on intestinal and pig health.

Detecting calves that are persistently infected with bovine viral diarrhea virus (BVDV) is essential to disease prevention. Immunohistochemistry (IHC) performed on formalin-fixed, paraffin-embedded ear-notch samples is commonly used for surveillance detection of BVDV antigens. However, due to the low percentage of positive samples in most submissions, the current workflow often entails considerable time reviewing negative results. Herein we aimed to utilize digital pathology and whole-slide imaging, coupled with advanced image analysis software, to enhance the efficiency of positive IHC detection in surveillance. Despite some challenges encountered during the implementation phase, the benefits of the reduced potential for human error and significant time savings for technicians and pathologists are evident. The screening of 518 slides, containing 2,884 ear notches, reached 97.4% sensitivity and 89.4% specificity compared to the gold standard of direct human assessment. The time taken for the personnel to operate the software and organize results was significantly shorter than the time needed for technicians and pathologists to manually examine the slides. Future refinements in software integration, staining protocols, and QC measures promise to further optimize this approach.