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Background: African swine fever (ASF) is one of the deadliest swine diseases with haemorrhagic symptoms and a high mortality rate. Plant‐derived additives are potential antiviral agents against viruses due to their environmental and user‐friendly properties. Objectives: This study aims to evaluate the efficacy of plant‐based additives (Phyto.A04 and Phyto.B) compared to an organic acid blend (OAB) in inactivating ASF virus (ASFV) in cell culture and feed. Methods: ASFV‐spiked feed was treated with individual or combined additives such as OAB, Phyto.A04 and Phyto.B. The viability of ASFV after treatment of ASFV‐spiked feed with additives was then confirmed by both methods, real‐time PCR and cell culture. Results: The results of the in vitro test with cell cultures showed that all three additives (OAB, Phyto.A04 and Phyto.B) exerted a strong virucidal effect on ASFV in porcine alveolar macrophage cells. OAB at a concentration of 0.3% reduced the virus concentration from 4.48 log10 HAD50/mL after 1 day of treatment (day 1) to 3.29 log10 HAD50/mL after 3 days of treatment (day 3) and remained undetected after 7 days of treatment (day 7). In Phyto.A04 with 1%, the virus was only detectable on day 1 (3.53 log10 HAD50/mL). Phyto.B with 0.01% and 0.05% both showed good efficacy in completely inhibiting virus presence on days 3 and 7. Conclusions: All additives, OAB, Phyto.A04 and Phyto.B, were able to inactivate ASFV in a dose‐dependent manner, as confirmed by cell culture and PCR methods. The combination of additives at different concentrations consistently improved the virucidal results. [ABSTRACT FROM AUTHOR]

ABSTRACT The objective of this study was to assess the impact of the vehicle of administration and the prandial state of post weaning piglets on the indices of therapeutic efficacy for different broad‐spectrum antibiotic/pathogen combinations. Pharmacokinetic data were retrieved from previous studies, in which we orally administered oxytetracycline (OTC), fosfomycin (FOS), or amoxicillin (AMX) according to the following treatments: dissolved in soft water to fasted or non‐fasted piglets, dissolved in hard water to fasted or non‐fasted piglets, and mixed with feed. Minimum inhibitory concentration (MIC) values for susceptible strains of bacteria causing swine diseases were obtained from the database of European Committee on Antimicrobial Susceptibility Testing (EUCAST) for each antibiotic. Pharmacokinetic/pharmacodynamic (PK/PD) indices of therapeutic efficacy—drug exposure over the dosing interval (fAUC/MIC) for OTC and FOS; time that free drug concentration remains above MIC (%fT>MIC) for AMX—were calculated for each antibiotic/pathogen combination under each treatment. After all OTC and in‐feed FOS and AMX treatments, the indices of therapeutic efficacy were below the target value for all the study microorganisms. When FOS or AMX were delivered dissolved in soft or hard water, the indices were above the target value over which therapeutic efficacy would be expected for Escherichia coli treated with FOS and, Glaesserella parasuis, Pasteurella multocida, and Actinobacillus pleuropneumoniae treated with AMX. The prandial state of piglets showed no influence on the indices of therapeutic efficacy. Pharmacokinetic profiles of broad‐spectrum antibiotics, specifically the ability to achieve target concentrations, may be largely reduced due to drug interactions with components present in feed or water resulting in a discrepancy with PK/PD principles of prudent and responsible use of antibiotics. [ABSTRACT FROM AUTHOR]

Flunixin meglumine is a nonsteroidal anti‐inflammatory drug approved to manage pyrexia associated with swine respiratory disease. In the United States, no analgesic drugs are approved for use in swine by the FDA, although they are needed to manage painful conditions. This study evaluated the pharmacokinetics and relative bioavailability of intranasal versus intramuscular flunixin in grower pigs. Six pigs received 2.2 mg/kg flunixin either intranasally via atomizer or intramuscularly before receiving flunixin via the opposite route following a 5‐day washout period. Plasma samples were collected over 60 h and analysed using ultra‐performance liquid chromatography and tandem mass spectrometry to detect flunixin plasma concentrations. A non‐compartmental pharmacokinetic analysis was performed. The median Cmax was 4.0 μg/mL and 2.7 μg/mL for intramuscular and intranasal administration, respectively, while the median AUCinf was 6.9 h μg/mL for intramuscular administration and 4.9 h μg/mL for intranasal administration. For both routes, the median Tmax was 0.2 h, and flunixin was detectable in some samples up to 60 h post‐administration. Intranasal delivery had a relative bioavailability of 88.5%. These results suggest that intranasal flunixin has similar, although variable, pharmacokinetic parameters to the intramuscular route, making it a viable route of administration for use in grower swine. [ABSTRACT FROM AUTHOR]

Background: Porcine reproductive and respiratory syndrome is a highly infectious disease of swine caused by PRRS virus (PRRSV). Objectives: To evaluate the prevalence of PRRSV antibodies in the four districts of hilly and terai regions of Nepal. Toassess the farm characteristics through a questionnaire interview of farmersregarding management practices and PRRS. Methods: A cross‐sectional study was conducted from July 2020 to June 2021 to determine the sero‐prevalence of PRRSV in pigs. A total of 180 porcine serum samples were collected from 23 pig farms and tested for PRRSV antibodies by ELISA. Alongside, farm characteristics were also assessed through questionnaire to determine the level of biosecurity measures in the farm, knowledge of the disease and possible control mechanisms. Results: Out of 180 samples, 37 were tested positive resulting the overall sero‐prevalence of 20.5%. There was significant association between different districts (p < 0.05) and PRRS prevalence. Prevalence of PRRSV antibody was found higher in Kaski district (10.5%) followed by Sunsari (8.8%) district. Based on age groups, highest prevalence was found in age groups of above 18 months (9.4%), followed by 13–18 months age groups (7.7%). Regarding the knowledge level of the disease, 43% of the farmers responded that they have heard about the disease. Biosecurity practices in the farm was found very poor where only 40% of the farms had disinfectant at the entrance of the farm and 25% pig farmers were found using separate boots while dealing with pigs. Conclusions: The findings of this study reveal the presence of PRRSV antibodies in pigs of Nepal. In addition poor biosecurity measures, management practices and poor knowledge level about the disease among farmers highly affect in the control and prevention of disease thereby affecting the pig production and productivity. Therefore, government should develop and implement effective control measures and biosecurity programs. [ABSTRACT FROM AUTHOR]

In 2019, sows at a swine farm in Japan showed influenza‐like illness (ILI) shortly after contact with an employee that exhibited ILI. Subsequently, a veterinarian became sick shortly after examining the sows and was diagnosed with influenza A virus (IAV) infection. Then, her family also contracted the infection. Subsequently, Pandemic A(H1N1)2009 viruses were isolated from all samples obtained from the sows, veterinarian and her family. Whole‐genome analysis of the isolates confirmed that the viruses belonged to the same lineage (6B.1A) and the genome sequences obtained from all of the isolates were almost identical to each other. Furthermore, an epidemiological survey revealed no contact between veterinarians or their families and influenza patients prior to the onset of illness. These results strongly indicated a case of bidirectional infection between humans and sows. At the same time, we found a few unique mutations in the IAV genomes corresponding to the host species. The mutations that occurred in the virus after it was transferred from the farm worker to the sows were not observed in the humans infected from the sows, probably as a result of the mutations reverting to the original nucleotides. These results demonstrate that the bidirectional transmission of IAV is a potential risk for the next pandemic outbreak due to the emergence of new mutant strains. [ABSTRACT FROM AUTHOR]

Influenza D virus (IDV) was first isolated from a swine with respiratory disease symptoms in 2011 in the United States. Epidemiological and serological studies support the hypothesis that cattle represent the natural reservoir of IDV with periodical spillover events to other animal hosts. Little is known about the seroprevalence in humans and in specific target groups such as veterinarians in Italy. This study was designed to assess the prevalence of antibodies against two influenza D lineages (D/660 and D/OK) in Italy in archived serum samples from veterinarians working with swine collected in 2004. Serum samples were tested by haemagglutination inhibition (HI) and virus neutralization (VN) assays. Results showed that 4.88% (4/82) of tested samples were positive for D/660 and 2.44% (2/82) for D/OK by HI assay. Three out of four samples showed positivity when tested by VN assay. Our data suggest undetected IDVs might have circulated and/or been introduced in Italy as early as 2004 at least in some animal species such as swine. In addition, it seems that the virus was circulating among veterinarians before the first isolation in 2011. This finding highlights the importance to continue monitoring the IDV spread in animals and humans for more detailed surveillance. [ABSTRACT FROM AUTHOR]

Introduction: Chronic infections lead to the functional exhaustion of T cells. Exhausted T cells are phenotypically differentiated by the surface expression of the immunoinhibitory receptor, such as programmed death-1 (PD-1). The inhibitory signal is produced by the interaction between PD-1 and its PDligand 1 (PD-L1) and impairs the effector functions of T cells. However, the expression dynamics of PD-L1 and the immunological functions of the PD-1/PD-L1 pathway in chronic diseases of pigs are still poorly understood. In this study, we first analyzed the expression of PD-L1 in various chronic infections in pigs, and then evaluated the immune activation by the blocking assay targeting the swine PD-1/PD-L1 pathway. Methods: In the initial experiments, anti-bovine PD-L1 monoclonal antibodies (mAbs) were tested for cross-reactivity with swine PD-L1. Subsequently, immunohistochemical analysis was conducted using the anti-PD-L1 mAb. Finally, we assessed the immune activation of swine peripheral blood mononuclear cells (PBMCs) by the blockade with anti-PD-L1 mAb. Results: Several anti-PD-L1 mAbs tested recognized swine PD-L1-expressing cells. The binding of swine PD-L1 protein to swine PD-1 was inhibited by some of these cross-reactive mAbs. In addition, immunohistochemical analysis revealed that PD-L1 was expressed at the site of infection in chronic infections of pigs. The PD-L1 blockade increased the production of interleukin-2 from swine PBMCs. Conclusions: These findings suggest that the PD-1/PD-L1 pathway could be also involved in immunosuppression in chronic infections in pigs. This study provides a new perspective on therapeutic strategies for chronic diseases in pigs by targeting immunosuppressive pathways. [ABSTRACT FROM AUTHOR]

A 7‐month‐old, male castrated mixed‐breed pig presented for evaluation of a 3‐month history of cutaneous pigmented nodular lesions, multifocal leukoderma and leukotrichia. Skin biopsies were performed from pigmented nodules and depigmented skin for histopathology. Additional skin biopsies were collected aseptically for bacterial and fungal tissue cultures. Histopathologic diagnosis was a benign melanocytic neoplasm (melanocytoma) and marked vitiligo. Spontaneous regression of melanocytomas did not occur after 1 year of age as previously reported to occur in several swine breeds. Topical imidazoquinoline amine cream was applied to one melanocytoma three times a week for a month. No clinical improvement in either the melanocytoma or vitiligo occurred. In humans, vitiligo is associated with both neoplastic and benign melanocytic neoplasms; this case illustrates the presence of melanoma‐associated leukoderma in a domestic mixed‐breed pig and emphasises the importance of meticulous skin examination in swine patients with the development of vitiligo. [ABSTRACT FROM AUTHOR]

The pharmacokinetics of gamithromycin were evaluated in 26 male castrated and female crossbred swine administered gamithromycin 15% w/v (Zactran®, Boehringer Ingelheim) intravenously at 6 mg/kg bodyweight or intramuscularly at 3, 6 or 12 mg/kg bodyweight. Blood samples were collected up to Day 10 to establish the plasma profile of gamithromycin, bioavailability and dose proportionality. When administered by intramuscular injection at 6 mg/kg BWT, pharmacokinetic parameters were as follows: area under the curve until last quantifiable plasma concentration, 5.13 ± 0.957 µg*hours/ml; maximum plasma concentration, 960 ± 153 ng/ml at 5 to 15 min; terminal half‐life of 94.1 ± 20.4 hr. Absolute bioavailability was 92.2%. Increase in systemic exposure was proportional to the gamithromycin dose level over the range 3–12 mg/kg BWT. No gender‐related statistically significant difference in exposure was observed. For clinical evaluation of Zactran® against swine respiratory disease, 305 pigs from six commercial farms in three countries in Europe with signs associated with Actinobacillus pleuropneumoniae and/or Haemophilus parasuis and/or Pasteurella multocida and/or Bordetella bronchiseptica were used. At each site, animals were treated once in a 1:1 ratio with a single intramuscular dose of Zactran® (6 mg gamithromycin/kg bodyweight) or Zuprevo® (4% w/v tildipirosin at 4 mg/kg bodyweight; MSD Animal Health) at the recommended dose respectively. Animals were observed and scored daily for 10 consecutive days for signs of swine respiratory disease (depression, respiration and rectal temperature), and animals presenting signs of clinical swine respiratory disease (Depression Score 3 and/or Respiratory Score 3 associated with Rectal Temperature > 40.0°C) were removed from the study and considered as treatment failure. Animals which remained in the study were individually assessed for ʽtreatment successʼ or ʽtreatment failureʼ (Depression Score ≥ 1 and Rectal Temperature > 40.0°C or Respiratory Score ≥ 1 and Rectal Temperature > 40.0°C). Using a non‐inferiority hypothesis test (non‐inferiority margin = 0.10), the proportion of treatment successes in the Zactran® group (97%) was equivalent to or better than that in the Zuprevo® group (93%). [ABSTRACT FROM AUTHOR]

Classical swine fever (CSF) is an endemic disease in southeastern Asia and is one of the most important swine diseases in Vietnam. This study was conducted to characterize the pathology of natural cases of CSF in northern Vietnam in 2018 and their genetic prevalence. A total of 10 representative pigs were collected from four provinces (Hung Yen, Ha Noi, Quang Ninh and Thai Binh) during five outbreaks and examined pathologically. The gross and histopathological findings showed the disease was expressed as the acute or the subacute to chronic form of CSF, depending on the age of the animals. The most consistently observed lesions associated with infection by the classical swine fever virus (CSFV) included lymphoid depletions in tonsils, lymph node and spleen; histiocytic hyperplasia in spleen; cerebral haemorrhage; perivascular cuffing in the brain; renal erythrodiapedesis; urothelial vacuolation and degeneration and interstitial pneumonia. The immunohistochemical findings showed a ubiquitous CSFV antigen mainly in the monocytes/macrophages and in the epithelial and endothelial cells in various organs. CSFV neurotropism was also found in the small neurons of the cerebrum and the ganglia of the myenteric plexus. Analysis of the full‐length envelope protein (E2) genome sequence showed that all strains were genetically clustered into subgenotype 2.5, sharing a nucleotide identity of 94.0%–100.00%. Based on the results of this study, the strain was categorized as a moderately virulent CSFV. [ABSTRACT FROM AUTHOR]

Haemophilus parasuis is the etiological agent of Glässer's disease in swine, which associates with severe economic losses in the swine industry worldwide. A real‐time recombinase polymerase amplification assay (real‐time RPA) was developed for direct and rapid detection of H. parasuis basing on the translation‐initiation factor IF2 (infB) gene. The assay was performed successfully at 39°C for 20 min in Genie III, which is portable and chargeable by battery. The developed assay was highly specific for H. parasuis, and the limit of detection of the assay was 6.0 × 103 fg of H. parasuis genomic DNA, which was the same as that of a real‐time PCR developed previously. The assay was further evaluated on 68 pig tissue samples, and 18 (26.5%), 20 (29.4%), and 8 (11.8%) samples were positive for H. parasuis by the real‐time RPA, real‐time PCR and bacterial isolation, respectively. With the bacteria isolation as the reference method, the real‐time RPA showed a diagnostic specificity of 83.33% and a diagnostic sensitivity of 100%. The above data demonstrated the well‐potentiality and usefulness of the developed real‐time RPA assay in reliable diagnosis of swine Glässer's disease, especially in resource limited settings. [ABSTRACT FROM AUTHOR]

Background: Porcine epidemic diarrhea (PED) is a highly contagious swine disease caused by the PED virus (PEDV), which is a member of the family Coronaviridae. Since the first outbreaks in Belgium and the United Kingdom were reported in 1971, PED has spread throughout many countries around the world and causing significant economic loss. This study was conducted to investigate the recent distribution of PEDV strains in Vietnam during the 2015–2016 seasons. Methods: A total of 30 PED‐specific PCR‐positive intestinal and faecal samples were collected from unvaccinated piglets in Vietnam during the 2015–2016 seasons. The full length of the spike (S) gene of these PEDV strains were analysed to determine their phylogeny and genetic relationship with other available PEDV strains globally. Results: Phylogenetic analysis of the complete S gene sequences revealed that the 28 Vietnamese PEDV strains collected in the northern and central regions clustered in the G2 group (both G2a and G2b sub‐groups), while the other 2 PEDV strains (HUA‐PED176 and HUA‐PED254) collected in the southern region were clustered in the G1/G1b group/sub‐group. The nucleotide (nt) and deduced amino acid (aa) analyses based on the complete S gene sequences showed that the Vietnamese PEDV strains were closely related to each other, sharing nt and aa homology of 93.2%–99.9% and 92.6%–99.9%, respectively. The N‐glycosylation patterns and mutations in the antigenic region were observed in Vietnamese PEDV strains. Conclusions: This study provides, for the first time, up‐to‐date information on viral circulation and genetic distribution, as well as evidence to assist in the development of effective PEDV vaccines in Vietnam. [ABSTRACT FROM AUTHOR]

The coxsackievirus and adenovirus receptor (CAR) is an essential multifunctional cellular protein that is only beginning to be understood. CAR serves as a receptor for many adenoviruses, human group B coxsackieviruses, swine vesicular disease virus, and possibly other viruses. While named for its function as a viral receptor, CAR is also involved in cell adhesion, immune cell activation, synaptic transmission, and signaling. Knockout mouse models were first to identify some of these biological functions; however, tissue‐specific model systems have shed light on the complexity of different CAR isoforms and their specific activities. Many of these functions are mediated by the large number of interacting proteins described so far, and several new putative interactions have recently been discovered. As antiviral and gene therapy strategies that target CAR continue to emerge, future work poised to understand the biological implications of manipulating CAR in vivo is critical. [ABSTRACT FROM AUTHOR]

1 SMART Pharmacology, Department of Biomedical Sciences, Iowa State University, Ames, Iowa, U... B Introduction b : In vitro models for respiratory diseases in swine are based on 2D primary epithelial cell lines and are not solely derived from porcine pulmonary cells, which significantly hampers their biological relevance and predictive performance. AIV immunohistochemistry confirmed successful viral infection of H1N1 after a 24-h incubation, with significant cell apoptosis at the 72-h mark, confirming virus-induced cytolysis. [Extracted from the article]

Aujeszky's disease virus (ADV), also known as Suid alphaherpesvirus 1, which mainly infects swine, causes life-threatening neurological disorders. This disease is a serious global risk factor for economic losses in the swine industry. The development of new anti-ADV drugs is highly anticipated and required. Natto, a traditional Japanese fermented food made from soybeans, is a well-known health food. In our previous study, we confirmed that natto has the potential to inhibit viral infections by severe acute respiratory syndrome coronavirus 2 and bovine alphaherpesvirus 1 through their putative serine protease(s). In this study, we found that an agent(s) in natto functionally impaired ADV infection in cell culture assays. In addition, ADV treated with natto extract lost viral infectivity in the mice. We conducted an HPLC gel-filtration analysis of natto extract and molecular weight markers and confirmed that Fraction No. 10 had ADV-inactivating ability. Furthermore, the antiviral activity of Fraction No. 10 was inhibited by the serine protease inhibitor 4-(2-Aminoethyl) benzene sulfonyl fluoride hydrochloride (AEBSF). These results also suggest that Fraction No. 10, adjacent to the 12.5 kDa peak of the marker in natto extract, may inactivate ADV by proteolysis. Our findings provide new avenues of research for the prevention of Aujeszky's disease., (© 2023 The Societies and John Wiley & Sons Australia, Ltd.)

Florfenicol, a structural analog of thiamphenicol, has broad‐spectrum antibacterial activity against gram‐negative and gram‐positive bacteria. This study was conducted to investigate the epidemiological, pharmacokinetic–pharmacodynamic cutoff, and the optimal scheme of florfenicol against Escherichia coli (E. coli) with PK‐PD integrated model in the target infectious tissue. 220 E. coli strains were selected to detect the susceptibility to florfenicol, and a virulent strain P190, whose minimum inhibitory concentration (MIC) was similar to the MIC50 (8 μg/ml), was analyzed for PD study in LB and ileum fluid. The MIC of P190 in the ileum fluid was 0.25 times lower than LB. The ratios of MBC/MIC were four both in the ileum and LB. The characteristics of time‐killing curves also coincided with the MBC determination. The recommended dosages (30 mg/kg·body weight) were orally administrated in healthy pigs, and both plasma and ileum fluid were collected for PK study. The main pharmacokinetics (PK) parameters including AUC24 hr, AUC0–∞, Tmax, T1/2, Cmax, CLb, and Ke were 49.83, 52.33 μg*h/ml, 1.32, 10.58 hr, 9.12 μg/ml, 0.50 L/hr*kg, 0.24 hr−1 and 134.45, 138.71 μg*hr/ml, 2.05, 13.01 hr, 16.57 μg/ml, 0.18 L/hr*kg, 0.14 hr−1 in the serum and ileum fluid, respectively. The optimum doses for bacteriostatic, bactericidal, and elimination activities were 29.81, 34.88, and 36.52 mg/kg for 50% target and 33.95, 39.79, and 42.55 mg/kg for 90% target, respectively. The final sensitive breakpoint was defined as 16 μg/ml. The current data presented provide the optimal regimens (39.79 mg/kg) and susceptible breakpoint (16 μg/ml) for clinical use, but these predicted data should be validated in the clinical practice. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the pharmacokinetics and relative bioavailability of tilmicosin enteric granules and premix after oral administration at a dose of 40 mg/kg in pigs. Three kinds of different respiratory pathogens were selected for determination of minimal inhibitory concentration (MIC) to tilmicosin. Eight healthy pigs were assigned to a two‐period, randomized crossover design. A modified rapid, sensitive HPLC method was used for determining the concentrations of tilmicosin in plasma. Pharmacokinetic parameters were calculated by using WinNonlin 5.2 software. The MIC90 of tilmicosin against Haemophilus parasuis, Actinbacillus pleuropneumoniae, and Pasteurella multocida were all 8 μg/ml. These results indicated that these common pig respiratory bacteria are sensitive to tilmicosin. The main parameters of time to reach maximum plasma concentration (Tmax), elimination half‐life (t1/2β), mean residence time (MRT), and apparent volume of distribution (VF) were 2.03 ± 0.37 hr, 29.31 ± 5.56 hr, 25.22 ± 2.57 hr, 4.06 ± 1.04 L/kg, and 3.05 ± 0.08 hr, 17.06 ± 1.77 hr, 15.55 ± 1.37 hr, 2.95 ± 0.62 L/kg after the orally administrated tilmicosin enteric granules and premix. The relative bioavailability of tilmicosin enteric granules to premix was 114.97 ± 7.19%, according to the AUC0‐t values. These results demonstrated that tilmicosin enteric granules produced faster tilmicosin absorption, slower elimination, larger tissue distribution, and higher bioavailability compared to the tilmicosin premix. The present study results manifest that tilmicosin enteric granules can be used as a therapeutic alternative to premix in clinical treatment. [ABSTRACT FROM AUTHOR]

Swine respiratory disease (SRD) causes massive economic losses in the swine industry and is difficult to control and eradicate on pig farms. Here, we employed population genetics and transcriptomics approaches to decipher the molecular mechanism of host adaptation to swine respiratory disease. We recorded two SRD‐related traits, the enzootic pneumonia‐like (EPL) score and lung lesion (LL) levels, and performed four body weight measurements, at ages of 150, 180, 240, and 300 days, in a Chinese Bamaxiang pig herd (n = 314) raised under consistent indoor rearing conditions. We divided these animals into disease‐resistant and disease‐susceptible groups based on the most likely effects of both SRD‐related traits on their weight gain, and performed genetic differentiation analyses in these two groups. Significant loci showing the top 1% of genetic differentiation values, exceeding the threshold of p = 0.005 set based on 1,000‐times permutation tests, were defined as candidate regions related to host resistance or susceptibility to SRD. We identified 107 candidate genes within these regions, which are mainly involved in the biological processes of immune response, fatty acid metabolism, lipid metabolism, and growth factor signaling pathways. Among these candidate genes, TRAF6, CD44, CD22, TGFB1, CYP2B6, and SNRPA were highlighted due to their central regulatory roles in host immune response or fat metabolism and their differential expression between healthy lung tissues and lung lesions. These findings advance our understanding of the molecular mechanisms of host resistance or susceptibility to respiratory disease in pigs and are of significance for the breeding pigs resistant to respiratory disease in the swine industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: This study evaluated the effects of dietary zinc oxide nanoparticles (nano‐ZnOs) on growth performance, zinc status, intestinal morphology, microflora population, and immune response in weaned piglets. A total of 150 weaned piglets (9.37 ± 0.48 kg) were randomly allotted to five dietary treatments and fed with a basal diet (control), or the basal diet supplemented with nano‐ZnOs at 150, 300, or 450 mg kg−1, and 3000 mg kg−1 ZnO for 21 days. After a feeding test, six pigs from the control, 450 mg kg−1 nano‐ZnOs and 3000 mg kg−1 ZnO groups were slaughtered. RESULTS: Compared with the control, dietary supplements of nano‐ZnOs and ZnO could improve (P < 0.05) average daily weight gain (ADG), average daily feed intake (ADFI), and villus height to crypt depth ratio in the duodenum and jejunum, and decrease (P < 0.05) diarrhea incidence. Zinc retention in the serum, heart, liver, spleen and kidney of pigs supplemented with nano‐ZnOs and ZnO was increased (P < 0.05). Nano‐ZnOs decreased (P < 0.05) the zinc excretion compared with conventional ZnO. Lower Escherichia coli counts in the cecum, colon, and rectum were observed (P < 0.05) in the nano‐ZnOs group compared with the other groups. Compared with the control, ZnO and nano‐ZnOs increased (P < 0.05) the serum concentration of IgA, IL‐6, and TNF‐α, and decreased (P < 0.05) the concentration of IgM. CONCLUSION: These results indicated that low doses of nano‐ZnOs can have beneficial effects on growth performance, intestinal morphology and microflora, and immunity in weanling pigs, which are similar to the effects of pharmacological dosages of conventional ZnO. Nano‐ZnOs may reduce mineral excretion, which may reduce environmental challenges. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Background: Influenza B viruses (IBVs) have never been isolated from natural‐infected pigs in clinical cases, although the susceptibility of domestic pigs to experimental IBV infections had been confirmed as well as IBV‐specific antibodies were detected from pigs under natural and experimental conditions. Objectives: We aimed to assess and investigate the activities for infection and circulation of IBVs in pigs. Methods: Annual active surveys for influenza have been implemented on swine populations in Taiwan since July 1998. Nasal swabs, trachea, lungs, and blood from pigs were tested using virological and serological assays for influenza. Gene sequences of influenza viral isolates were determined and characterized. Preliminary sero‐epidemiological data for influenza virus were investigated. Results: Three strains of IBV were isolated and identified from natural‐infected pigs in 2014. Genetic characterization revealed the highest identities (>99%) of molecular sequence with the contemporary IBVs belonged to the B/Brisbane/60/2008 genetic clade of Victoria lineage in the phylogenetic trees for all 8 genes. IBV‐specific antibodies were detected in 31 (0.2%; 95%CI: 0.1%‐0.2%) of 15 983 swine serum samples from 29 (2.8%; 95%CI: 1.9%‐3.9%) of 1039 farm visits under annual active surveys from 2007 through 2017. Seropositive cases have been found sparsely in 1‐5 of test prefectures every year except 2015 and 2017 as well as scattered loosely over 26 townships/districts of 11 prefectures in Taiwan cumulatively in 11 years. Conclusions: Influenza B viruse infections from humans to pigs remained sporadic and accidental currently in Taiwan but might have paved potential avenues for newly emerging zoonotic influenza in the future. [ABSTRACT FROM AUTHOR]

Summary: As Salmonella enterica is an important pathogen of food animals, surveillance programmes for S. enterica serovars have existed for many years in the United States. Surveillance programmes serve many purposes, one of which is to evaluate alterations in the prevalence of serovars that may signal changes in the ecology of the target organism. The primary aim of this study was to evaluate changes in the proportion of S. enterica serovars isolated from swine over a near 20‐year observation period (1997–2015) using four longitudinal data sets from different food animal species. The secondary aim was to evaluate correlations between changes in S. enterica serovars frequently recovered from food animals and changes in S. enterica serovars associated with disease in humans. We found decreasing proportions of S. enterica serovar Typhimurium, serovar Derby and serovar Heidelberg and increasing proportions of S. enterica serovar 4,[5],12:i:‐, serovar Infantis and serovar Johannesburg in swine over time. We also found positive correlations for the yearly changes in S. enterica serovar 4,[5],12:i:‐, serovar Anatum and serovar Johannesburg between swine and human data; in S. enterica Worthington between avian and human data; and in S. enterica serovar 4,[5],12:i:‐ between bovine and human data. We found negative correlations for the yearly changes in S. enterica serovar 4,[5],12:i:‐ and serovar Johannesburg between avian and human data. [ABSTRACT FROM AUTHOR]

Salmonella is a major foodborne pathogen causing important zoonosis worldwide. Pigs asymptomatically infected in mesenteric lymph nodes (MLN) can be intermittent shedders of the pathogen through faeces, being considered a major source of human infections. European baseline studies of fattening pig salmonellosis are based on Salmonella detection in MLN. This work studies the relationship between Salmonella infection in MLN and intestinal content (IC) shedding at slaughter and the relationship between the presence of the pathogen and the serologic status at farm level. Mean Salmonella prevalence in the selected pigs (vertically integrated production system of Navarra, Spain) was 7.2% in MLN, 8.4% in IC and 9.6% in serum samples. In this low-moderate prevalence context, poor concordance was found between MLN infection and shedding at slaughter and between bacteriology and serology. In fact, most of shedders were found uninfected in MLN (83%) or carrying different Salmonella strains in MLN and in IC (90%). The most prevalent Salmonellae were Typhimurium resistant to ACSSuT ± Nx or ASSuT antibiotic families, more frequently found invading the MLN (70%) than in IC (33.9%). Multivariable analysis revealed that risk factors associated with the presence of Salmonella in MLN or in IC were different, mainly related either to good hygiene practices or to water and feed control, respectively. Overall, in this prevalence context, detection of Salmonella in MLN is an unreliable predictor of faecal shedding at abattoir, indicating that subclinical infections in fattening pigs MLN could have limited relevance in the IC shedding. [ABSTRACT FROM AUTHOR]

Hepatitis E virus (HEV) is an emerging pathogen that can be transmitted through contaminated raw or undercooked meat derived from domestic pigs. HEV infections have been documented among pig herds, pig products and environmental samples raising concern about the spread of the virus. HEV genotypes 3 and 4 are considered zoonotic and have been linked to human cases. HEV was detected in 51 of 335 bile samples (15.2%) from healthy pigs in Minas Gerais, Brazil. Phylogenetic analysis of partial sequences from ORF1 and ORF2 regions yielded discordant results, assigning isolates to subtypes 3c and 3i, respectively, suggesting intragenotypic HEV recombination. [ABSTRACT FROM AUTHOR]

ABSTRACT: Toll‐like receptor 5 is a pattern‐recognition receptor for bacterial flagellin. We previously reported that a single nucleotide polymorphism (SNP) of swine TLR5, C1205T, impairs recognition of Salmonella typhimurium (ST) flagellin and ethanol‐killed Salmonella Choleraesuis (SC). In the present study, weaned, specific pathogen‐free (SPF) Landrace piglets with CC, CT or TT genotypes were orally infected with ST (L‐3569 strain) to determine the effect of this specific SNP on ST infection in vivo. Eighteen ST‐infected piglets (six each with CC, CT, or TT) exhibited fever and diarrhea for 1 week after infection. TT piglets had the longest duration of fever. TT piglets had the greatest mean diarrhea score during the experimental period, followed by CT and CC piglets. Fecal ST shedding was greater in CT and TT pigs than CC pigs from 2 days after infection. Serum haptoglobin concentration increased in ST‐infected piglets and to greater extents in CT and TT pigs than CC pigs. Daily weight gain was lower in infected pigs, particularly TT piglets, than control pigs. To the best of our knowledge, this study is the first to demonstrate that impairment of TLR recognition affects pig susceptibility to disease in vivo. Thus, piglets with the T allele of swine TLR5 (C1205T) exhibit impaired resistance to ST infection. Furthermore, elimination of the T allele of this SNP from Landrace pigs would lead to enhancement of their resistance to ST infection. [ABSTRACT FROM AUTHOR]

Flunixin is marketed in several countries for analgesia in adult swine but little is known about its efficacy in piglets. Thirty‐two piglets (6–8 days old) were randomized to receive placebo saline (n = 11, group CONTROL) or flunixin meglumine intravenously at 2.2 (n = 11, group MEDIUM) or 4.4 (n = 10, group HIGH) mg/kg, 10 hr after subcutaneous injection of kaolin in the left metacarpal area. A hand‐held algometer was used to determine each piglet’s mechanical nociceptive threshold (MNT) from both front feet up to 50 hr after treatment (cut‐off value of 24.5 newton). Serial venous blood samples were obtained to quantify flunixin in plasma using LC‐MS/MS. A PKPD model describing the effect of flunixin on the mechanical nociceptive threshold was obtained based on an inhibitory indirect response model. A two‐compartmental PK model was used. A significant effect of flunixin was observed for both doses compared to control group, with 4.4 mg/kg showing the most relevant (6–10 newton) and long‐lasting effect (34 hr). The median IC50 was 6.78 and 2.63 mg/ml in groups MEDIUM and HIGH, respectively. The ED50 in this model was 6.6 mg/kg. Flunixin exhibited marked antinociceptive effect on kaolin‐induced inflammatory hyperalgesia in piglets. [ABSTRACT FROM AUTHOR]

We studied the constancy of the relationship between rectal and intraabdominal temperature as well as their linkage to inflammatory markers (leucocyte counts, kynurenine-to-tryptophan ratio (Kyn-Trp ratio), tumour necrosis factor alpha ( TNF- α) in healthy and in pigs exposed to lipopolysaccharide ( LPS) and/or deoxynivalenol ( DON). Barrows ( n = 44) were fed 4 weeks either a DON-contaminated (4.59 mg DON/kg feed) or a control ( CON) diet and equipped with an intraabdominal temperature logger and a multicatheter system ( V.portae hepatis, V.lienalis, Vv.jugulares) facilitating infusion of 0.9% NaCl ( CON) or LPS (7.5 μg/kg BW) and simultaneous blood sampling. Body temperatures were measured and blood samples taken every 15 min for leucocyte counts, TNF- α and Kyn-Trp ratio. Combination of diet and infusion created six groups: CON_ CONjug.- CONpor., CON_ CONjug.- LPSpor., CON_ LPSjug.- CONpor., DON_ CONjug.- CONpor., DON_ CONjug.- LPSpor., DON_ LPSjug.- CONpor.. The relationship between both temperatures was not uniform for all conditions. Linear regression revealed that an intraabdominal increase per 1°C increase in rectal temperature was ~25% higher in all LPS-infused pigs compared to NaCl-infusion, albeit diet and site of LPS infusion modified the magnitude of this difference. Inflammatory markers were only strongly present under LPS influence and showed a significant relationship with body temperatures. For example, leucocyte counts in clinically inconspicuous animals were only significantly correlated to core temperature in DON-fed pigs, but in all LPS-infused groups, irrespective of diet and temperature method. In conclusion, the gradient between body core and rectal temperature is constant in clinically inconspicuous pigs, but not under various pathophysiological conditions. In the latter, measurement of inflammatory markers seems to be a useful completion. [ABSTRACT FROM AUTHOR]

Summary: Most swine Salmonella national control programmes in Europe have been based on the categorization of herds according to risk levels based on serological results. However, none of the non‐Scandinavian countries have reported of any significant success on Salmonella infection reduction in fattening pigs or the number of human cases attributable to pigs or pork. The limited accuracy of the tests used, the small number of animals sampled and the likely lack of herd representativeness of the samples used could be major factors affecting the suitability of these programmes. Focusing on minimizing Salmonella shedding at slaughter appears more important to prevent human infections than focusing on detection of seropositive pigs/herds at this stage. This study assessed whether performing on‐farm serology may help to predict shedding at slaughter. Between 2010 and 2016, pigs from six cohorts from a Salmonella‐positive herd were bled at 30, 60 and 90 days on fattening and before slaughter, and faecal samples collected at slaughter. Serology on days 60, 90 and before slaughter predicted somewhat shedding at slaughter with no significant differences among them. Pigs with higher OD% values at these point times would have higher risk of shedding when arriving to slaughter. The probability of shedding for a pig sampled on day 90 and showing an OD% value of 10 was 43%, and the risk increased up to 65% if the OD% was 40. Concluding, on‐farm serology may help to determine to some extent the risk of Salmonella shedding at slaughter from seropositive fattening units, which would allow for prompt on‐farm and slaughter interventions to reduce the likelihood of slaughter contamination with Salmonella. [ABSTRACT FROM AUTHOR]

Summary: Influenza A viruses circulate in swine and can spread rapidly among swine when housed in close proximity, such as at agricultural fairs. Youth who have close and prolonged contact with influenza‐infected swine at agricultural fairs may be at increased risk of acquiring influenza virus infection from swine. Animal and human health officials have issued written measures to minimize influenza transmission at agricultural exhibitions; however, there is little information on the knowledge, attitudes, and practice (KAP) of these measures among animal exhibitors. After an August 2016 outbreak of influenza A(H3N2) variant (“H3N2v”) virus infections (i.e., humans infected with swine influenza viruses) in Michigan, we surveyed households of animal exhibitors at eight fairs (including one with known H3N2v infections) to assess their KAP related to variant virus infections and their support for prevention measures. Among 170 households interviewed, most (90%, 151/167) perceived their risk of acquiring influenza from swine to be low or very low. Animal exhibitor households reported high levels of behaviours that put them at increased risk of variant influenza virus infections, including eating or drinking in swine barns (43%, 66/154) and hugging, kissing or snuggling with swine at agricultural fairs (31%, 48/157). Among several recommendations, including limiting the duration of swine exhibits and restricting eating and drinking in the animal barns, the only recommendation supported by a majority of households was the presence of prominent hand‐washing stations with a person to monitor hand‐washing behaviour (76%, 129/170). This is a unique study of KAP among animal exhibitors and highlights that animal exhibitor households engage in behaviours that could increase their risk of variant virus infections and have low support for currently recommended measures to minimize infection transmission. Further efforts are needed to understand the lack of support for recommended measures and to encourage healthy behaviours at fairs. [ABSTRACT FROM AUTHOR]

Summary: Influenza A virus (IAV) is a major zoonotic pathogen that threatens global public health. Novel strains of influenza A viruses pose a significant risk to public health due to their pandemic potential, and transmission of influenza A viruses from animals to humans is an important mechanism in the generation and introduction of IAVs that threaten human health. The purpose of this descriptive correlational study was to develop real‐life training scenarios to better inform swine exhibitors of the risks they may encounter when influenza A viruses are present in swine. Educational activities were implemented in five Ohio counties where exhibition swine had historically been shedding influenza A viruses during the county fair. A total of 146 youth swine exhibitors participated in the educational programme, and an increase in the knowledge base of these youth was documented. It is expected that educating youth exhibitors about exposure to influenza A virus infections in the swine they are exhibiting will result in altered behaviours and animal husbandry practices that will improve both human and animal health. [ABSTRACT FROM AUTHOR]

Summary: To investigate public health implications of antibiotics to control post‐weaning scours, we surveyed 22 commercial pig herds in southeastern Australia. Fifty faecal samples per herd were collected from pre‐ and post‐weaned piglets. Presumptive Escherichia coli isolates were confirmed by MALDI‐TOF MS. Isolates (n = 325) were screened for susceptibility to 19 veterinary antibiotics using MIC broth microdilution. All 325 E. coli isolates underwent further testing against 27 antibiotics used in human medicine and were screened for ETEC adhesin and enterotoxin genes (F4 (K88), F5 (K99), F6 (987P), F18, F41, STa, STb, Stx2e and LT) by multiplex PCR. Isolates identified as phenotypically resistant to third‐generation cephalosporin (3GC) and aminoglycoside antibiotics were screened by multiplex PCR/reverse line blot to detect common β‐lactam and aminoglycosides resistance genes, confirmed by sequencing. Twenty (6.1%) of the E. coli isolates were resistant to 3GC antibiotics and 24 (7.4%) to the aminoglycoside antibiotic gentamicin. Genetic analysis revealed six different extended spectrum β‐lactamase (ESBL) genes (blaCTX‐M‐1, ‐14, ‐15, ‐27, blaSHV‐12 and blaCMY‐2‐like genes), four of which have not been previously reported in Australian pigs. Critically, the prevalence of 3GC resistance was higher in non‐pathogenic (non‐ETEC) isolates and those from clinically normal (non‐diarrhoeal) samples. This highlights the importance of non‐ETECE. coli as reservoirs of antimicrobial resistance genes in piglet pens. Antimicrobial resistance surveillance in pig production focused on diagnostic specimens from clinically‐affected animals might be potentially misleading. We recommend that surveillance for emerging antimicrobial resistance such as to 3GC antibiotics should include clinically healthy pigs. [ABSTRACT FROM AUTHOR]

Abstract: In a group of 22 healthy pigs aged between 4 and 6 months, 2 pigs became ill with high fever, complete anorexia, cough and abnormal swaying movements on 22 June 2015. One of them died on June 24 and the second died on July 3. Shortly after, the remaining pigs also fell ill and died from the same illness by 10 August 2015. We investigated the aetiology, epidemiological and clinical features of the outbreak. We recorded the clinical signs and symptoms for each pig with the date of onset of illness. Veterinarians conducted post‐mortem examinations on the 12 dead pigs, they collected tissue samples from the dead pigs and placed them in a tube containing 1 mL of nucleic acid extraction buffer (lysis buffer). We tested all the tissue samples by real‐time reverse transcription polymerase chain reaction (rRT‐PCR) to detect classical swine fever virus (CSFV) because the animals’ symptoms matched those of this disease. We also conducted a phylogentic analysis of the nucleotide sequence of the E2 gene segment of CSFV detected in a lung tissue sample. The attack rate (22/22) and the case fatality were 100%. The predominant symptoms of the disease included high fever, cough, diarrhoea and swaying movements of the hind legs prior to death. Of the 12 pigs tissue samples tested, all had evidence of the presence of CSFV RNA by rRT‐PCR. The phylogenetic analysis indicated that the virus belongs to genotype 2.2, which is closely related to CSFV genotype 2.2 reported in India. Our investigation suggests that CSF is circulating in pigs, posing a risk for communities in Bangladesh that rely on pigs for economic income and dietary protein. Future research could focus on estimating the disease and economic burden of CSFV in pig rearing areas to determine if interventions might be warranted or cost‐effective. [ABSTRACT FROM AUTHOR]

Objective: To explore the diversity among isolates of the Actinobacillus pleuropneumoniae serovars most common in Australia (serovars 1, 5, 7 and 15) and to examine the Apx toxin profiles in selected representative isolates. Design: A total of 250 isolates selected from different farms were examined for their genotypic profiles and a subset of 122 isolates for their toxin profiles. Methods: The isolates of serovars 1, 5, 7 and 15 selected for this study came from different farms and different Australian states and were submitted for serotyping to the reference laboratory. The overall diversity of the strains was explored with the enterobacterial repetitive intergenic consensus (ERIC) PCR and the presence of the toxin genes was investigated with a toxin PCR assay. Results: Some degree of variation was observed in the ERIC‐PCR pattern within all four serovars, ranging from 38% to 61% genetic diversity. When looking at the toxin gene profile and, therefore, the predicted ability to produce the expected toxin pattern, one isolate each of serovars 1 (n = 20) and 7 (n = 47) and 17 isolates of serovar 15 (n = 40) showed variation to the expected gene profile. Conclusion: The variations in toxin gene patterns, as detected by PCR, found in this study could be related to significant changes in the gene sequence or total absence of the gene. Variation in toxin gene sequences has been observed in other countries. This variation in the toxin profile could also explain possible variation in pathogenicity observed in the field. [ABSTRACT FROM AUTHOR]

The presentation will cover the regulatory and commercialization history of Harrisvaccines (now Merck Animal Health/MSD) and the future of next generation saRNA vaccines delivered with novel nanoparticles. Self-amplifying messenger RNA (saRNA) replicates itself within a cell, significantly increasing the amount of protein produced from the encoded gene. Genvax Technologies Inc., Ames, Iowa, USA The commercial use of mRNA vaccine platforms against infectious diseases in swine predates the mRNA vaccine acceptance for COVID-19 in humans. [Extracted from the article]

Hepatitis E virus ( HEV) is the most common cause of viral hepatitis in humans. Pigs may act as a reservoir of HEV, and pig handlers were frequently identified with a higher prevalence of antibodies to HEV. The objectives of this study were to identify evidence of HEV infection in pigs and compare the history of jaundice between pig handlers and people not exposed to pigs and pork. Blood and faecal samples were collected from 100 pigs derived from three slaughterhouses in the Gazipur district of Bangladesh from January to June, 2011. We also interviewed 200 pig handlers and 250 non-exposed people who did not eat pork or handled pigs in the past 2 years. We tested the pig sera for HEV-specific antibodies using a competitive ELISA and pig faecal samples for HEV RNA using real-time RT- PCR. Of 100 pig sera, 82% ( n = 82) had detectable antibody against HEV. Of the 200 pig handlers, 28% (56/200) demonstrated jaundice within the past 2 years, whereas only 17% (43/250) of controls had a history of jaundice ( p < .05). Compared to non-exposed people, those who slaughtered pigs (31% versus 15%, p < .001), reared pigs (37% versus 20%, p < .001), butchered pigs (35% versus 19%, p < .001) or involved in pork transportation (28% versus 13%, p < .001) were more likely to be affected with jaundice in the preceding 2 years. In multivariate logistic regression analysis, exposure to pigs (odds ratio [ OR]: 2.2, 95% CI: 1.2-3.9) and age ( OR: 0.97, 95% CI: 0.95-0.99) was significantly associated with jaundice in the past 2 years. Pigs in Bangladesh demonstrated evidence of HEV infection, and a history of jaundice was significantly more frequent in pig handlers. Identifying and genotyping HEV in pigs and pig handlers may provide further evidence of the pig's role in zoonotic HEV transmission in Bangladesh. [ABSTRACT FROM AUTHOR]

Salmonella enterica serotype Choleraesuis ( S. Choleraesuis), Gram-negative facultative intracellular pathogen is capable of inducing the cholera in pigs whose symptoms manifest as fever, depression, septicemia, arthritis, and diarrhea. Infections with S. Choleraesuis has resulted in great economic loss for the swine breeding operations. Bacterial outer membrane vesicles (OMVs) play an important role in pathogenicity and host-pathogen interaction. In this study, we purified OMVs released by S. Choleraesuis strain χ3545 and characterized their lipopolysaccharide (LPS) profile. The OMVs contained intact LPS molecules. By using LC-MS/MS, we identified 192 proteins in the OMVs. In addition, the subcellular location and biological functions of the vesicles was predicted. The proteins were mainly derived from outer membranes and cytoplasm. Several proteins were immunoreactive and associated with the secretion pathway. Some putative multi-drug resistance-associated proteins were also identified. Furthermore, immunization experiment via intranasal or intraperitoneal route in mice demonstrated that S. Choleraesuis OMVs could elicit strong humoral and mucosal immune responses. Although OMVs as vaccine did not provide strong protection against clinical strain of wild-type S. Choleraesuis, immunization of OMVs still prolonged the survival time of vaccinated mice after high dose of S. Choleraesuis infection. Overall, this study provides valuable fundamental information toward elucidating the pathogenicity and functions of OMVs secreted from S. Choleraesuis. [ABSTRACT FROM AUTHOR]

This study deals with the levels of toxic polychlorinated dibenzo-p-dioxin and furan congeners (PCDD/Fs) in the livers of piglets affected by infectious diseases using isotope dilution high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). Seventeen toxic congeners in the liver samples infected with bacterial and viral diseases were compared. For porcine reproductive and respiratory syndrome virus (PRRSV) samples, the North American- and European-type PRRS diseases were observed. This study shows that there are significantly different levels of PCDD/Fs, present, which vary according to the types of diseases as evidenced by our analysis of the piglet liver samples. [ABSTRACT FROM AUTHOR]

The risk of Salmonella shedding among pigs at slaughter with regard to their previous on-farm Salmonella status was assessed in a group of pigs from a farm from NE of Spain. A total of 202 pigs that had been serologically monitored monthly during the fattening period and from which mesenteric lymph nodes ( MLN) and faecal ( SFEC) samples were collected at slaughter for Salmonella isolation were included. A repeated-measures anova was used to assess the relationship between mean OD% values during the fattening period and sampling time and bacteriology on MLN and SFEC. Pigs were also grouped into four groups, that is pigs seronegative during the fattening period and Salmonella negative in MLN (group A; n = 69); pigs seronegative during the fattening period but Salmonella positive in MLN (B; n = 36); pigs seropositive at least once and Salmonella positive in MLN (C; n = 50); and pigs seropositive at least once but Salmonella negative in (D; n = 47). Pigs shedding at slaughter seroconverted much earlier and showed much higher mean OD% values than non-shedders pigs. The proportion of Salmonella shedders in groups A and D was high and similar (26.1% and 29.8%, respectively), but significantly lower than that for groups B and C. The odds of shedding Salmonella for groups B and C were 4.8 (95% CI = 1.5-15.5) and 20.9 (3.7-118) times higher, respectively, when compared to A. It was concluded that a large proportion of Salmonella seronegative pigs may shed Salmonella at slaughter, which would be likely associated to previous exposure with contaminated environments (i.e. transport and lairage). For pigs already infected at farm, the likelihood of shedding Salmonella was much higher and may depend on whether the bacterium has colonized the MLN or not. The odds of shedding Salmonella spp. were always much higher for pigs in which Salmonella was isolated from MLN. [ABSTRACT FROM AUTHOR]