Fecal Shedding Research Articles

Revisiting the gene loss of respiratory requirements for Salmonella Typhimurium and Salmonella Enteritidis in the chicken infection model.

Salmonella strains are able to use tetrathionate as a terminal respiratory electron acceptor. Here we report the role of ttrRSBCA operon in Salmonella-challenged broilers. Signature-tagged mutagenesis was used to construct defective strains of S. Typhimurium and S. Enteritidis carrying deletions in the whole ttr operon (ΔttrRSBCA) followed by measurement of faecal shedding and cecal colonization counts. Regarding fecal excretion, S. Typhimurium mutant strain harbouring deletion in ttrRSBCA were excreted in similar numbers than the parental wild-type strain during the experimental period, while the SEΔttrRSBCA strain was excreted slightly less in comparison to the wild-type strain. Furthermore, our findings revealed partial attenuation of STMΔttrRSBCA at 2, 5, 7, and 28 days post-infection (dpi), whereas the SEΔttrRSBCA strain was recovered in lower numbers compared to the parental strain at 5, 14, and 28 dpi. These results indicate that such mutations must be accompanied by other genetic changes to obtain a complete attenuation.

Breed-specific responses to coccidiosis in chickens: identification of intestinal bacteria linked to disease resistance

BackgroundCoccidiosis, caused by Eimeria parasites, is a major enteric disease in poultry, significantly impacting animal health, production performance, and welfare. This disease imposes a substantial economic burden, costing the global poultry industry up to $13 billion annually. However, effective mitigation strategies for coccidiosis remain elusive. While different chicken breeds exhibit varying resistance to coccidiosis, no commensal bacteria have been directly linked to this resistance.MethodsTo assess relative resistance of different breeds to coccidiosis, 10-day-old Fayoumi M5.1, Leghorn Ghs6, and Cobb chickens were challenged with 50,000 sporulated Eimeria maxima oocysts or mock-infected. Body weight changes, small intestinal lesions, and fecal oocyst shedding were evaluated on d 17. Ileal and cecal digesta were collected from individual animals on d 17 and subjected to microbiome analysis using 16S rRNA gene sequencing. ResultsFayoumi M5.1 chickens showed the lowest growth retardation, intestinal lesion score, fecal oocyst shedding, and pathobiont proliferation compared to Ghs6 and Cobb chickens. The intestinal microbiota of M5.1 chickens also differed markedly from the other two breeds under both healthy and coccidiosis conditions. Notably, group A Lactobacillus and Ligilactobacillus salivarius were the least prevalent in both the ileum and cecum of healthy M5.1 chickens, but became highly enriched and comparable to Ghs6 and Cobb chickens in response to coccidiosis. Conversely, Weissella, Staphylococcus gallinarum, and Enterococcus durans/hirae were more abundant in the ileum of healthy M5.1 chickens than in the other two breeds. Despite being reduced by Eimeria, these bacteria retained higher abundance in M5.1 chickens compared to the other breeds.ConclusionsFayoumi M5.1 chickens exhibit greater resistance to coccidiosis than Leghorn Ghs6 layers and Cobb broilers. Several commensal bacteria, including group A Lactobacillus, L. salivarius, Weissella, S. gallinarum, and E. durans/hirae, are differentially enriched in Fayoumi M5.1 chickens with strong correlation with coccidiosis resistance. These bacteria hold potential as probiotics for coccidiosis mitigation.

VP4-Specific IgA level as a correlate of neutralizing antibody and fecal shedding of porcine rotavirus infection.

VP4-Specific IgA level as a correlate of neutralizing antibody and fecal shedding of porcine rotavirus infection.

Hepato-selective dihydroquinolizinones active against hepatitis A virus in vitro and in vivo.

Hepato-selective dihydroquinolizinones active against hepatitis A virus in vitro and in vivo.

Sheep challenged with sheep-derived type II Mycobacterium avium subsp. paratuberculosis: the first experimental model of paratuberculosis in China

BackgroundParatuberculosis (PTB), caused by Mycobacterium avium subsp. paratuberculosis (MAP), is difficult to diagnose in the early stages and poses substantial challenges in prevention, control, treatment, and eradication. A well-defined animal model can help identify disease markers and serve as a platform for vaccine and drug development. This study used sheep as a ruminant model for experimental MAP infection research.MethodsNine 3-month-old lambs with negative MAP antigen and antibody were divided into three groups (control group A and inoculated groups B and C). The inoculated groups were challenged with sheep-derived type II MAP. After exposure, we recorded clinical signs, assessed fecal shedding, tested blood MAP levels, and performed fecal cultures. We also measured MAP-specific antibodies and monitored IFN-γ and IL-10 responses in vivo. At 255 days after inoculation, we performed autopsy, tissue culture, pathomorphological observation, and bacterial organ burden (BOB) testing.ResultsAll six sheep in groups B and C were infected, regardless of the challenge dose and exhibited emaciation; two had intermittent soft stools. Intermittent MAP shedding in feces was observed from 60 to 255 days after exposure. Typical MAP colonies formed after 4–6 weeks of fecal and tissue culture, and Ziehl–Neelsen staining showed positive results. In the groups challenged with MAP, some blood samples tested positive for MAP and MAP-specific antibodies were detected in some serum samples. IFN-γ response was significantly higher in groups B and C than that in group A from day 60 post-exposure, whereas the IL-10 response was higher than that in group A from day 120 post-exposure. In the infected groups, the ileal lesions were the most severe and were classified as grade 3 PTB granulomatous inflammation (multibacillary lesions). BOB levels varied across different tissues.ConclusionsTo the best of our knowledge, this is the first experimental MAP challenge study on sheep in China. Polymerase chain reaction detection was more sensitive than MAP culture, whereas enzyme-linked immunosorbent assay was less sensitive for detecting MAP-specific antibodies. IFN-γ and IL-10 responses may serve as targets for monitoring PTB progression. The severity of ileal lesions and acid-fast bacilli grading play crucial roles in the understanding of infection dynamics. Currently, early PTB diagnosis requires a combination of multiple sample types and detection methods.

The effect of asparagine-13 in porcine epidemic diarrhea virus envelope protein on pathogenicity

The pathogenesis of porcine epidemic diarrhea virus (PEDV) has not been fully clarified, which seriously hinders the prevention of the disease. The envelope (E) protein of PEDV induces the expression of pro-inflammatory cytokines, but the role of these inflammatory reactions in PEDV pathogenicity is still unknown. In this study, the asparagine at position 13 was found to be crucial to PEDV E protein induced inflammatory response. Exogenously expressing the parent E protein, rather than the E mutant carrying N13A, induces the activation of NF-κB and expression of inflammatory factors, including IL-6, IL-8, and TNF-α. Compared with the parental rPEDV strain, the recombinant strain rPEDV-EN13A exhibited a significantly lower infectious titer and formed smaller plaques. In addition, rPEDV-EN13A induced lower expression of inflammatory factors in vitro and in vivo. The pathogenicity assay shows that the rPEDV-EN13A strain caused diminished fecal PEDV RNA shedding, delayed death time, and milder histopathological lesions to intestinal villi. Our data provide a unique perspective for exploring the pathogenic mechanism of PEDV and a new target for the development of attenuated PEDV live vaccines.

Genotype I Newcastle Disease Virus, Isolated from Wild Duck, Can Protect Chickens Against Newcastle Disease Caused by Genotype VII.

Newcastle disease viruses (NDVs) circulating among wild birds and poultry may differ in virulence. Some NDVs cause devastating outbreaks in chickens. The NDV/duck/Moscow/3639/2008 (d3639) strain was isolated from a wild duck. Its genome was sequenced (PP795281, GenBank) and the biological properties, specifically for infection in chicken and mice, were studied. Strain d3639 of genotype I.2 has an F protein cleavage site (112-GKQGRL-117) and a HN protein length (616 a.a.) of the lentogenic pathotype. It was tested, in comparison with the genotype II LaSota vaccine strain, for its immunogenicity and protective efficacy against a challenge with the velogenic NDV strain NDV/chicken/Moscow/6081/2022 (ch6081) of sub-genotype VII.1.1, the complete genome of which was also sequenced in this study (PP766718, GenBank). Both the d3639 and LaSota viruses did not induce clinical signs in chickens or mice. Single immunization was performed by inoculation through drinking water with the live virus. Inoculation protected the chickens during a subsequent challenge with velogenic ch6081 and significantly reduced shedding in feces. Double immunization was sufficient to achieve prolonged immunity and prevented the shedding of the velogenic virus after the challenge. Thus, this natural lentogenic d3639 virus possesses properties similar to the LaSota vaccine strain and can protect against sub-genotype VII.1.1 NDV.

A new method to replace oral gavage for the study of Cryptosporidium infection in mice.

Oral gavage is a widely used method to infect mice with Cryptosporidium parvum (CP), the most common animal model of infection. Cryptosporidium spp. are worldwide distributed, gastrointestinal parasites that mainly cause diarrhea in humans and neonatal ruminants. CP is transmitted via the fecal-oral route, usually through contaminated water. In rodent models of Cryptosporidium infection, oral gavage is used as the route of infection. This method, while effective, induces a generalized stress response and requires specific skills and experience. Our aim was to replace oral gavage by a refined method using a mixture palatable to mice, where oocysts could be mixed in. A peanut butter gelatin mix (PBG) containing CP oocysts was developed and used for voluntary oral infection of mice. We were able to confirm CP infections in young interferon-gamma knock out mice by detecting oocyst shedding in feces, demonstrating that the PBG method successfully produced infections similar to those obtain through oral gavage, and could be used for other pathogens or as a method to deliver experimental therapeutics or other substances.

Non-Compromised Efficacy of the First Commercial Ready-to-Use Genotype 2d Porcine Circovirus Type 2 and Mycoplasma hyopneumoniae Vaccine.

Mycoplasma hyopneumoniae (Mhyo) and porcine circovirus type 2 (PCV2) are critical pathogens in the swine industry, both contributing significantly to the porcine respiratory disease complex (PRDC). Given their impact, it is logical to control these pathogens simultaneously. Consequently, combined vaccinations against Mhyo and PCV2 are gaining popularity in swine health management. We present the efficacy of the first commercial combined vaccine prepared of a genotype PCV2d strain and Mhyo and tested against experimental challenge infections with target pathogens in comparative trials with other commercial products. In these studies, three-week-old piglets were vaccinated according to the manufacturers' instructions. Five weeks later, they were challenged with two Mhyo strains over three consecutive days or with a PCV2d strain once. Positive controls included challenged pigs without prior vaccination, while non-vaccinated/non-challenged pigs served as negative controls. The key parameters measured were lung lesion scores and seroconversion for Mhyo, and viraemia, rectal shedding, lymph node and lung viral content, and seroconversion for PCV2. Findings and conclusion: The results showed no compromising effects between the vaccine components and highlighted significant differences in efficacy among the various products tested. Additionally, oral fluid sampling demonstrated a strong correlation with the viraemia and fecal shedding of PCV2, underscoring the diagnostic and animal welfare benefits of this sampling method.

Evaluation of Extended-Release Eprinomectin Injectable and Doramectin Injectable with the Inclusion of Refugia on Performance Outcomes and Fecal Parameters in Stocker Cattle.

Evaluating different tactics to mitigate the effects of gastrointestinal nematode infection in growing stocker cattle is essential to better understand opportunities to optimize cattle health and performance. Due to the potential development of anthelmintic resistance, parasitologists and industry stakeholders have proposed maintaining refugia in cattle populations and combination treatment as tactics to delay anthelmintic resistance yet limited large-scale field data are available for practitioners to make evidence-based decisions. The objective of this experiment was to compare the effects of extended-release eprinomectin injectable and doramectin injectable on growth and fecal shedding of parasites in stocker calves grazing with non-treated (refugia) cohorts. Steers (n = 995; 243.38 kg) were randomized to one of two experimental treatment groups on Day 0, extended-release eprinomectin (ERE) or doramectin injectable (DOR). A subset of animals (n = 47) was selectively not treated with an anthelmintic to maintain refugia (REF). Individual body weights were recorded on days 0, 105, and 130 to calculate average daily gain and overall body weight gain during each of those time periods. Fecal samples were collected per rectum from approximately 10% of the same animals in each group on days 0, 105, and 130. Mean fecal egg count was significantly lower in the 10% of animals tested in the ERE group on days 105 and 130 when compared to 10% of the animals in the DOR group (Day 105-ERE: 46.45 eggs per gram, DOR: 155.30 eggs per gram, p < 0.01; Day 130-ERE: 9.65 eggs per gram, DOR: 22.51 eggs per gram, p = 0.02). From day 0 to 105, the mean average daily gain in the ERE group was 0.87 kg/day, which tended (p = 0.055) to be higher than the mean for the DOR group, 0.845 kg/day.

Development of intimin-enriched outer membrane vesicles (OMVs) as a vaccine to control intestinal carriage of Enterohemorrhagic Escherichia coli.

Development of intimin-enriched outer membrane vesicles (OMVs) as a vaccine to control intestinal carriage of Enterohemorrhagic Escherichia coli.

National survey of the rat hepatitis E virus in rodents in Spain, 2022 to 2023.

BackgroundRat hepatitis E virus (ratHEV) is an emerging virus causing acute and chronic hepatitis in humans. Rats are the main natural reservoir of this pathogen. Large-scale studies assessing ratHEV circulation in rodents in Spain are lacking.AimWe aimed to determine the prevalence of ratHEV in rats in Spain and evaluate potential transmission risk to humans.MethodsWe designed a cross-sectional nationwide study where black (Rattus rattus) and Norway (R. norvegicus) rats were collected and analysed between 2022 and 2023 for ratHEV infection using real-time (RT)-qPCR testing of liver tissue. Sequencing and analysis of ratHEV shedding in faeces were carried out in positive animals.ResultsRatHEV was detected in 125 of the 481 rats analysed, supposing a prevalence of 26.0% (95 CI%: 22.3-30.1). Positive rats were found in urban (25.6%), and farm (29.8%) settings. Black rats (31.3%) had 1.5 times higher odds of being infected by the virus than Norway rats (22.5%) (p=0.049). Significantly higher prevalence of ratHEV was detected in rodents sampled from southern (31.9%) than northern (17.8%) Spain (p=0.003). Viral RNA was detected in faeces from 45.5% of infected rats. Phylogenetic analysis evidenced a wide genetic diversity of ratHEV sequences, some showing high homology with ratHEV strains found in patients from Spain.ConclusionsCirculation of ratHEV appears to be heterogeneous and the virus appears to be endemic among rat populations in Spain, highlighting the possible risk of zoonotic transmission of this emerging virus in this country.

Impact of Temperature Variations on the Viability and Infectivity of Sporulated Eimeria papillata Oocysts in C57BL/6 Mice.

Eimeria is a protozoan apicomplexan parasite that affects animals and poultries. This study investigated how temperature variations impact the inactivation of sporulated E. papillata oocysts during experimental infections in mice. A total of 20 male C57BL/6 mice were divided into four groups, with five mice in each group, as follows: Group 1: Control group - Group 2: Infected group inoculated with fresh oocysts (subjected to 23℃ for 7days) - Group 3: Infected group inoculated with thermal oocysts (subjected to heating conditions at 100℃ for 60min) - Group 4: Infected group inoculated with frozen oocysts (subjected to freezing at -20℃ for 7days). An oral infection was initiated using 103 sporulated E. papillata oocysts to inoculate groups 2-4. Biological indicators, including body weight (BW) and feed intake (FI), were evaluated for each group. Oocyst output was assessed on day 5 post-infection. After sacrificing the mice, jejunal tissues were collected and processed for histopathological and biochemical analyses. Our findings indicated significant morphological alterations of sporulated Eimeria oocysts (i.e. a reduction in oocyst size and rounded shape of sporozoite) after being subjected to heating and freezing conditions. During the in vivo study, temperature treatment data shows significant inactivation of oocysts, with no fecal shedding. This result reflects enhancements in biological indicators and histopathological injuries, with the absence of intracellular Eimeria stages in the jejunal tissues, alongside a restoration of nutrient composition, particularly carbohydrates and proteins. Significant observations were also recorded regarding catalase (CAT), glutathione (GSH), nitric oxide (NO), and hydrogen peroxide (H2O2) levels. Temperature changes impact the viability of Eimeria oocysts and their role in coccidiosis. More research is needed on other biotic and abiotic factors in managing the disease.

Occurrence and genetic diversity of the zoonotic rat hepatitis E virus in small mammal species, Spain

Rat hepatitis E virus (ratHEV-C1) is a newly zoonotic and globally distributed virus of increasing public health concern. Although rats of the genus Rattus are the main reservoir of this emerging virus, the role of other small mammals in the epidemiology of ratHEV-C1 in Europe is unknown as large-scale survey studies specifically assessing the circulation of ratHEV-C1 in these species have not yet been conducted. In this study, we examined active ratHEV-C1 infection in 514 animals from seven different small mammal species sampled throughout Spain. The presence of viral RNA was evaluated for ratHEV-C1 infection using RT-qPCRs in liver tissue. Sequencing and analysis of ratHEV-C1 shedding in faeces were carried out in positive animals. Viral RNA was detected in 15 individuals (mean Ct value: 34.5), supposing a frequency of 2.9% (95% CI: 1.8–4.8). We confirmed ratHEV infection in house mice (14.5%; 11/76), common voles (0.7%; 2/288) and garden dormice (25.0%; 2/8) and viral shedding in faeces in 36.4% (4/11) of positive house mice. Infected animals were detected in urban areas, small ruminant farms and rural areas throughout Spain. Our sequences showed a considerable genetic diversity, and they were closely related with ratHEV-C1 strains detected in human and rats from Spain, Germany and Hungary. Our study confirms that ratHEV is not limited to Rattus genus, identifying other rodents’ species as potential host of ratHEV-C1 in Europe. Our results highlight the importance of continued surveillance in animals to fully understand the dynamics of ratHEV-C1 and its impact on public health.

Temporal dynamics of SARS-CoV-2 shedding in feces and saliva: a longitudinal study in Norfolk, United Kingdom during the 2021-2022 COVID-19 waves.

This study provides critical insights into the dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) shedding in fecal and saliva samples, demonstrating that while viral RNA is detectable shortly after diagnosis, its prevalence declines rapidly over the course of infection. Detection was more common among individuals with more concurrent symptoms, emphasizing the potential influence of symptom burden on viral persistence. By analyzing a United Kingdom-based cohort, this study fills a significant gap in the literature, which has largely focused on Asian and North American populations, offering a geographically unique perspective on viral shedding dynamics. Our findings contribute to a globally relevant understanding of SARS-CoV-2 shedding by revealing differences in shedding durations compared to studies from other regions. These differences highlight the need for geographically diverse research to account for variations in genetic background, immune response, and healthcare practices.

The use of wastewater surveillance to estimate SARS-CoV-2 fecal viral shedding pattern and identify time periods with intensified transmission

BackgroundWastewater-based surveillance is an important tool for monitoring the COVID-19 pandemic. However, it remains challenging to translate wastewater SARS-CoV-2 viral load to infection number, due to unclear shedding patterns in wastewater and potential differences between variants.ObjectivesWe utilized comprehensive wastewater surveillance data and estimates of infection prevalence (i.e., the source of the viral shedding) available for New York City (NYC) to characterize SARS-CoV-2 fecal shedding pattern over multiple COVID-19 waves.MethodsWe collected SARS-CoV-2 viral wastewater measurements in NYC during August 31, 2020 – August 29, 2023 (N = 3794 samples). Combining with estimates of infection prevalence (number of infectious individuals including those not detected as cases), we estimated the time-lag, duration, and per-infection fecal shedding rate for the ancestral/Iota, Delta, and Omicron variants, separately. We also developed a procedure to identify occasions with intensified transmission.ResultsModels suggested fecal viral shedding likely starts around the same time as and lasts slightly longer than respiratory tract shedding. Estimated fecal viral shedding rate was highest during the ancestral/Iota variant wave, at 1.44 (95% CI: 1.35 – 1.53) billion RNA copies in wastewater per day per infection (measured by RT-qPCR), and decreased by around 20% and 50-60% during the Delta wave and Omicron period, respectively. We identified around 200 occasions during which the wastewater SARS-CoV-2 viral load exceeded the expected level in any of the city's 14 sewersheds. These anomalies disproportionally occurred during late January, late April—early May, early August, and from late-November to late-December, with frequencies exceeding the expectation assuming random occurrence (P < 0.05; bootstrapping test).DiscussionThese estimates may be useful in understanding changes in underlying infection rate and help quantify changes in COVID-19 transmission and severity over time. We have also demonstrated that wastewater surveillance data can support the identification of time periods with potentially intensified transmission.

Efficient gastrointestinal colonization by Campylobacter jejuni requires components of the ChuABCD heme transport system.

Previous research demonstrated that Campylobacter jejuni encodes a heme utilization system that facilitates heme-dependent growth under iron-limiting conditions and that transcription of this system is induced during human infection. Despite these observations, it remained unknown whether the heme transport system is required for colonization and disease in a susceptible host. To address this, we created individual non-polar deletion mutants of each component of the heme transport system, as well as a total deletion of the inner membrane transporter, ChuBCD, and examined their ability to promote heme-dependent growth and iron uptake. From this work, we found that only the heme receptor, ChuA, was required for heme-dependent growth and iron acquisition, which supports earlier work of another group. Further, we examined whether intestinal colonization, immune activation, and pathology were altered during infection with these mutants. After establishing that elevated heme and chuABCD expression occurs during C. jejuni infection of IL-10 -/- mice, we found that heme transport mutants exhibited significantly reduced fecal shedding and colonization of the cecum and colon. In addition, we found that neutrophil and macrophage recruitment and intestinal pathology often remained intermediately elevated despite decreased bacterial loads. These results suggest that heme utilization promotes efficient colonization and full pathogenicity in C. jejuni , but that neither is completely abrogated in its absence.

Isolation, genetic characterization, and pathogenicity of the porcine epidemic diarrhea virus S-INDEL strain EJS6 in China

Porcine epidemic diarrhea virus (PEDV) is a highly infectious intestinal coronavirus that poses a significant threat to the pig industry because of its strong virulence and propensity for mutation and recombination. PEDV is classified into three major genotypes based on the spike (S) gene sequence: G1 (classical), G2 (variant), and S-INDEL (characterized by nucleotide insertions/deletions in the S gene). Both the G1 and G2 genotypes have been frequently detected in China, whereas the S-INDEL strain has rarely been reported or isolated. In this study, we isolated a PEDV S-INDEL strain, designated EJS6, from a pig farm experiencing severe diarrhea in Jiangsu Province, China. Genetic evolution analysis revealed that the Chinese S-INDEL strains represented by EJS6 presented sequence differences from other S-INDEL strains isolated in Europe and the United States, forming a new branch within the S-INDEL genotype. Compared with the G2 strain EHuB4, EJS6 presented a lower viral titer, smaller plaque size, and reduced syncytium-forming ability in Vero cells. We also compared the pathogenicity of EJS6 and EHuB4 in 5-day-old suckling piglets. Both strains exhibited similar levels of fecal virus shedding in the infected piglets; however, the histopathological and mortality results indicated that the pathogenicity of the EJS6 strain was weaker than that of the EHuB4 strain. In summary, we successfully isolated the first Chinese PEDV S-INDEL strain and characterized its genetic evolution and pathogenicity, thereby enhancing our understanding of the prevalence of PEDV in China.

The prevalence, serotypes and antibiograms of Salmonella isolates on Thoroughbred stud farms in New South Wales and Victoria.

Salmonella enterica subsp. enterica is responsible for substantial morbidity and mortality within horse populations, worldwide. The prevalence of Salmonella shedding in faeces has largely been reported in hospital settings, with limited information from general horse populations. Further, there is little understanding of the serotypes and antibiograms of Salmonella isolates from horses in Australia. The objectives of this study were to (1) estimate the prevalence of Salmonella in stud farm horse populations, (2) determine serotypes and antibiograms for isolates, and (3) determine whether seasonal, animal, farm or management factors are associated with Salmonella shedding. A prospective longitudinal cohort study was performed on 11 Thoroughbred stud farms in New South Wales and Victoria between 1st April 2023 and 30th March 2024. Faecal samples were collected every 3 months (spring, summer, autumn, winter) and data for each animal and farm were obtained. Standard bacteriological culture methods were used to isolate Salmonella and serotype and antimicrobial susceptibility patterns were determined. A total of 1476 faecal samples from 1330 horses were submitted. Salmonella was isolated from 5 horses (0.4%, 95% CI 0.2-0.9) on four farms during summer and autumn: S. Mbandaka (2), S. Typhimurium (2) and S. Wandsbek (1). No isolate was multidrug-resistant (MDR). Five stud farms reported a history of a horse shedding Salmonella on the property (NSW: 4, Victoria: 1) and four farms reported vaccination for Salmonella. The prevalence of Salmonella on Australian Thoroughbred stud farms is low with varied serotypes involved and without evidence of MDR.

Vaccination versus antimicrobials to prevent Porcine Proliferative Enteropathy: associated costs and effects on piglets' growth, health, and serological performance.

This study evaluated vaccination and prophylactic use of antimicrobials as strategies to prevent Porcine Proliferative Enteropathy (PPE) during nursery and growth-finishing phases. Three hundred weaned piglets (~ 29 days old) were distributed into groups: NVMED - no vaccinated against Lawsonia intracellularis but in-feed medicated with antimicrobials (amoxicillin, florfenicol, lincomycin, spectinomycin and tilmicosin); VMED - vaccinated and in-feed medicated; VNMED - vaccinated but no in-feed medicated. Piglets were vaccinated at weaning (Porcilis® Ileitis, MSD Animal Health). The following variables were assessed: growth and health performance, anti-L. intracellularis IgG levels, L. intracellularis fecal shedding, Pneumonia and Pleurisy Index (PPI) at slaughter, antimicrobial consumption and costs, and vaccination expenses. Average daily gain (ADG) at the nursery phase was lower in VNMED group (p < 0.01); however, there was no treatment effect on feed conversion, ADG, and body weight at growth-finishing phase (p ≥ 0.23). Similar anti-L. intracellularis IgG levels were found for VMED and VNMED groups at all evaluated moments (p = 0.01). L. intracellularis was only detected in feces samples from 4/90 tested piglets and no difference in health performance was found (p > 0.05). Groups presented PPI < 0.89. In-feed antimicrobial consumption and related costs were 3 to 3.5-fold higher for NVMED and VMED groups compared to VNMED group. The prophylactic administration of antimicrobials used in this study did not affect the serological performance post-vaccination against L. intracellularis. Additionally, vaccine use to prevent PPE reduced the antimicrobial consumption and related costs by ~70%, with no impairments on production outputs.