Lawsonia intracellularis infection and proliferative enteropathy in foals

Microbiological pathogens in fecal samples of foals during the first year of life

OBJECTIVE

The objective of the study was to investigate the age dependent occurrence of different infectious agents in foals with diarrhea.

MATERIAL AND METHODS

Fecal samples, which were submitted to a commercial laboratory for a PCR-profile "Foal Diarrhea Pathogens" from 01.01.2021 up to 31.12.2022 (n=144), were examined for Equine Coronavirus (ECoV), Lawsonia (L.) intracellularis, Rhodococcus (R.) hoagii (=R. equi), Clostridium (Cl.) perfringens toxin-encoding genes cpa, cpe, cpb, etx and netF, Clostridioides (C.) difficile toxin-encoding genes tcdA and tcdB, as well as Rotavirus A via PCR.

RESULTS

Pathogens could be detected in a high proportion (42.9%) of the samples. Rotavirus A was the most prevalent pathogen in the current study, followed by clostridial species. Especially in foals younger than one month, netF-producing Cl. perfringens was detected frequently. In this age group, netF-producing Cl. perfringens was as prevalent as Rotavirus A. In comparison, R. hoagii, L. intracellularis and ECoV were detected rarely. Cl. perfringens toxin-encoding genes cpb and etx were not present in the examined samples. In general, the previously known age dependency of the investigated pathogens could be confirmed. Nevertheless, Rotavirus A and netF-positive Cl. perfringens could also be detected outside of the most susceptible age group. Coinfections with the examined pathogens had a low prevalence in the current study.

CONCLUSIONS

In general, the examined pathogens showed an age dependent occurrence, but infections in foals outside of the common age group could not be ruled out with certainty due to small sample numbers in some of the age groups. Although Rotavirus A was the most prevalent pathogen in this study, netF-producing Cl. perfringens is an important differential diagnosis, especially in newborn foals. The diagnostic approach in diarrheic foals should contain a broad spectrum of pathogens. This is not only important to detect coinfections, but also to detect shedders, in order to protect other horses in the stable.

Ecophysiology and interactions of a taurine-respiring bacterium in the mouse gut

Taurine-respiring gut bacteria produce H2S with ambivalent impact on host health. We report the isolation and ecophysiological characterization of a taurine-respiring mouse gut bacterium. Taurinivorans muris strain LT0009 represents a new widespread species that differs from the human gut sulfidogen Bilophila wadsworthia in its sulfur metabolism pathways and host distribution. T. muris specializes in taurine respiration in vivo, seemingly unaffected by mouse diet and genotype, but is dependent on other bacteria for release of taurine from bile acids. Colonization of T. muris in gnotobiotic mice increased deconjugation of taurine-conjugated bile acids and transcriptional activity of a sulfur metabolism gene-encoding prophage in other commensals, and slightly decreased the abundance of Salmonella enterica, which showed reduced expression of galactonate catabolism genes. Re-analysis of metagenome data from a previous study further suggested that T. muris can contribute to protection against pathogens by the commensal mouse gut microbiota. Together, we show the realized physiological niche of a key murine gut sulfidogen and its interactions with selected gut microbiota members.

High Seroprevalence of Lawsonia intracellularis in Thoroughbred Farms in Southern Brazil

The aim of the present study was to carry out a serological survey to identify the seroprevalence of Lawsonia intracellularis in six Thoroughbred farms in the Southern region of the state of Rio Grande do Sul, Brazil. During 2019 and 2020, blood samples from 686 Thoroughbred horses were obtained from six different breeding farms. Horses were divided into groups according to age: (1) broodmares (>5 years), (2) two-year-old foals, (3) yearlings, and (4) 0-6 months-old foals. Blood samples were collected by venipuncture of the external jugular vein. The detection of antibodies (IgG) against L. intracellularis was performed by Immunoperoxidase Monolayer Assay. The detection of specific antibodies (IgG) against L. intracellularis in the evaluated population was 51%. The highest detection (86.8%) of IgG was in the broodmares category, while the lowest (5.2%) was in foals of 0-6 months of age. Regarding the farms, the Farm 1 had the highest (67.4%) prevalence of seropositivity against L. intracellularis, while Farm 4 had the lowest (30.6%). There was no record of clinical manifestation of Equine Proliferative Enteropathy in the sampled animals. The results of this study show the high seroprevalence of L. intracellularis in Thoroughbred farms in the Southern of Rio Grande do Sul, suggesting a large and continuous exposure to the agent.

Development and validation of a flow cytometry antibody test for Lawsonia intracellularis

Lawsonia intracellularis is the etiologic agent of porcine proliferative enteropathy (PPE), an inflammatory bowel disease with a major economic impact on the pig industry. The serological diagnosis of PPE can be performed using Blocking or Indirect ELISA, Immunoperoxidase Monolayer Assay (IPMA) and Indirect Fluorescence Antibody Test (IFAT). Here, we designed a most sophisticated immunological method for the detection of porcine anti-L. intracellularis IgGs, named Flow Cytometry Antibody Test - FCAT. This assay uses whole, live-attenuated L. intracellularis bacteria derived from a commercial vaccine. For the assay, we set up the optimal antigen concentration (10⁶ bacterium/assay), primary antibody dilution (1:100), time of incubation (20 min), antigen stability (15 days), precision (coefficient of variation - CV < 10%), reproducibility (CV ≤ 13%) and Receiver Operating Characteristic (ROC). When using a cut-off of >15.15% for FCAT, we determined that it showed a sensitivity of 98.8% and specificity of 100%. The rate of agreement with IPMA was 84.09% with a kappa index of 0.66. FCAT was used to screen 1,000 sera from non-vaccinated pigs housed in 22 different farms and we found that 730 pigs (73%) from 16 farms (72.7%) had L. intracellularis IgG. This high prevalence confirms that L. intracellularis is endemic on Brazilian pig farms. Finally, we determined that FCAT is an easy to perform diagnostic assay and we would highly recommend it for: i) seroepidemiological studies; ii) evaluation of infection dynamics; and iii) characterization of the humoral response profile induced by vaccines.

Prevalence of equine proliferative enteropathy in Hidaka district, Hokkaido, over five seasons

Equine proliferative enteropathy (EPE) is an equine infectious disease that can lead to severe weight loss and hyperplasia of the intestinal mucosa due to infection with Lawsonia intracellularis. In this study, we investigated the prevalence of EPE in a major Thoroughbred breeding area: Hidaka district, Hokkaido, Japan. Of the 252 symptomatic horses that we tested, 192 EPE cases (76.2%), including 8 fatal cases, were confirmed from April 2015 to March 2020 by etiological and/or serological investigation. Most of the EPE cases were observed in foals (88.5%), with fewer cases in yearlings (7.3%) and adults (4.2%). Asymptomatic infection was observed in 62.9% of the horses kept with affected horses. These results suggest that EPE is an enzootic disease in Hidaka district.

Preparation and Characterization of a New Monoclonal Antibody Specific Against Lawsonia intracellularis and Its Application in Indirect Immunofluorescence and Immunocytochemistry Assay

Proliferative enteropathy (PE) is an infectious enteric disease caused by Lawsonia intracellularis (L. intracellularis) and is endemic in pig herds worldwide. However, a L. intracellularis-specific monoclonal antibody plays an important role in the evaluation of L. intracellularis infection in vitro. Therefore, the objective of this study was to produce and identify the characteristics of a new monoclonal antibody against the outer membrane protein (Omp2) of L. intracellularis and apply it in an indirect immunofluorescence assay (IFA) and immunocytochemistry (IHC). The results indicated that three highly specific monoclonal antibodies against the Omp2 protein (4D9, 3G2, and 7G5) of L. intracellularis were obtained by using purified Omp2 as an immunogen, the titers of ascitic fluids of 4D9, 3G2, and 7G5 cells were 1:2,048,000, 1:512,000, and 1:256,000, respectively. IFA analysis showed that the 4D9, 3G2, and 7G5 have no cross-reactivity with other enteric bacteria commonly found in the ilea of pigs or closely related to L. intracellularis, such as Desulfovibrio, Bilophila wadsworthia (B. wadsworthia), Salmonella choleraesuis (S. choleraesuis), Salmonella typhimurium (S. typhimurium), Escherichia coli (E. coli), and Brachyspira hyodysenteriae (B. hyodysenteriae). IFA and IHC results indicated that the monoclonal antibodies can be successfully used as primary antibodies to detect L. intracellularis in infected cells and in the crypt of the ileum from infected tissues of PE. Our findings suggested that the new monoclonal antibody specific against L. intracellularis will be useful for the evaluation of L. intracellularis infection in vivo and in vitro.

Gut Microbiota Manipulation in Foals-Naturopathic Diarrhea Management, or Unsubstantiated Folly?

Diarrhea in foals is a problem of significant clinical and economic consequence, and there are good reasons to believe microbiota manipulation can play an important role in its management. However, given the dynamic development of the foal microbiota and its importance in health and disease, any prophylactic or therapeutic efforts to alter its composition should be evidence based. The few clinical trials of probiotic preparations conducted in foals to date show underwhelming evidence of efficacy and a demonstrated potential to aggravate rather than mitigate diarrhea. Furthermore, recent studies have affirmed that variable but universally inadequate quality control of probiotics enables inadvertent administration of toxin-producing or otherwise pathogenic bacterial strains, as well as strains bearing transferrable antimicrobial resistance genes. Consequently, it seems advisable to approach probiotic therapy in particular with caution for the time being. While prebiotics show initial promise, an even greater scarcity of clinical trials makes it impossible to weigh the pros and cons of their use. Advancing technology will surely continue to enable more detailed and accurate mapping of the equine adult and juvenile microbiota and potentially elucidate the complexities of causation in dysbiosis and disease. In the meantime, fecal microbiota transplantation may be an attractive therapeutic shortcut, allowing practitioners to reconstruct a healthy microbiota even without fully understanding its constitution.

High Seroprevalence Against Lawsonia intracellularis Among Adult Horses in Belgium

Lawsonia intracellularis (LI) is an obligate intracellular gram-negative rod causing equine proliferative enteropathy (EPE). Occasional cases of EPE have been reported in foals living in Belgium, but the seroprevalence of equine LI in this country is unknown. The target population included clinically healthy adult horses, whose blood samples were collected and analyzed for specific IgG antibodies against LI using a blocking enzyme-linked immunosorbent assay test. The results were expressed as percentage of inhibition (PI). Samples that had a PI <20% were judged as negative, those between 20 and 30% as inconclusive, and those >30% were considered positive. A total of 356 blood samples were analyzed with 352 horses (98.8%) testing positive, 2 horses (0.6%) testing negative, and 2 horses (0.6%) showing inconclusive results. The large percentage of seropositive samples obtained in this study confirms a widespread exposure of Belgian horses to LI.

Mortality, clinical findings, predisposing factors and treatment of Clostridioides difficile colitis in Japanese thoroughbred racehorses

BACKGROUND

Although Clostridioides difficile-associated diseases (CDAD) is considered to be associated with colitis in horses, few studies have been performed with a focus on the characteristics of CDAD in thoroughbred racehorses.

METHODS

Between 2010 and 2018, a test for C. difficile was performed using faecal samples from 137 thoroughbred racehorses with colitis presenting with diarrhoea and fever. The mortality rate, clinical findings, predisposing factors and the selected treatments were investigated in a retrospective manner.

RESULTS

Twenty-four cases were diagnosed as CDAD and 113 as non-CDAD. The mortality rate was significantly higher in the CDAD group (83 per cent) than that in the non-CDAD group (34 per cent). The levels of serum amyloid A, blood urea nitrogen and packed cell volume at initial presentation were also significantly higher, and those of total protein and albumin were significantly lower in the CDAD group. The development of CDAD was associated with the administration of antimicrobials, surgery and hospitalisation. No significant improvement in mortality was observed for any of the selected treatment in both groups.

CONCLUSION

CDAD in thoroughbred racehorses was identified as a high mortality disease with rapid progression of systemic inflammation and deterioration of the circulatory state. Further investigation is required to improve the treatment.

Evaluation of mouse enteroids as a model for Lawsonia intracellularis infection

Lawsonia intracellularis, an obligate intracellular bacterium, is an important enteric pathogen in pig herds and horse farms worldwide. The hallmark feature of L. intracellularis infection is the proliferation of epithelial cells in intestinal crypts. A major limitation to the study of L. intracellularis infection is the lack of an in vitro model that reproduces the changes observed in proliferative enteropathy. Here we investigated the suitability of mouse enteroids as a model to study L. intracellularis infection. Mouse enteroids were microinjected with L. intracellularis, filter-sterilized L. intracellularis culture supernatant, or sterile cell culture media (DMEM). L. intracellularis antigen was detected in mouse enteroids by immunohistochemistry and was located mostly in the basal region of the epithelium. There was no differential growth of enteroids among treatment groups, and cellular proliferation was not increased in L. intracellularis-infected enteroids in relation to non-infected enteroids based on immunofluorescence staining. L. intracellularis infection did not induce changes in gene expression of Ki-67 (proliferation marker), Sox9 (marker for transit amplifying cells) and Muc2 (marker for goblet cells). These results indicate that although L. intracellularis antigen is detectable in mouse enteroids, indicating susceptibility to infection, mouse enteroids fail to replicate the cellular proliferation and gene expression changes observed in proliferative enteropathy. Nevertheless, we have successfully demonstrated that mouse enteroids can be used to model days-long intracellular pathogen infection, serving as potential models for the study of other pathogens of interest in veterinary medicine.

Effects of Lawsonia intracellularis infection in the proliferation of different mammalian cell lines

Lawsonia intracellularis is an obligate intracellular bacterium that causes proliferative enteropathy in various animal species. While cellular proliferation of intestinal cells is recognized as the hallmark of L. intracellularis infection in vivo, it has not been demonstrated in in vitro models. In order to assay the effect of L. intracellularis, various cell lines were infected with pathogenic and non-pathogenic passages of the bacterium. Because of the high proliferative rate of these cell lines, serum deprivation, which is known to reduce proliferation, was applied to each of the cell lines to allow the observation of proliferation induced by L. intracellularis. Using antibodies for Ki-67 and L. intracellularis in dual immunofluorescence staining, we observed that L. intracellularis was more frequently observed in proliferating cells. Based on wound closure assays and on the amount of eukaryotic DNA content measured over time, we found no indication that cell lines infected with L. intracellularis increased proliferation and migration when compared to non-infected cells (p > 0.05). Cell arrest due to decreased serum in the culture media was cell-line dependent. Taken together, our findings provide data to support and expand previous subjective observations of the absence of in vitro proliferation caused by L. intracellularis in cell cultures and confirm that cell lines infected by L. intracellularis fail to serve as adequate models for understanding the cellular changes observed in proliferative enteropathy-affected intestines.

Antimicrobial Resistance in Leptospira, Brucella, and Other Rarely Investigated Veterinary and Zoonotic Pathogens

Leptospira, Brucella, and Borrelia are major agents of zoonotic disease, causing high morbidity and, in some cases, significant mortality in humans. For all three genera, prompt diagnosis and appropriate antimicrobial therapy are required to prevent the development of chronic, debilitating illness. Leptospira spp. are intrinsically resistant to several antimicrobial classes; however, there is little evidence in the literature for development of acquired resistance to antimicrobial agents used for clinical treatment of acute leptospirosis. For Brucella infections, there are numerous reports of relapses following therapy, but it is unclear whether this is due to sequestration within infected sites (e.g., bone) or the development of acquired resistance. Brucella have maintained their susceptibility to doxycycline and rifampicin, which in combination remain the most common treatments of brucellosis in humans. In vitro induced point mutations are described as imparting resistance to rifampicin (rpoB) and fluoroquinolones (gyrA). The clinical significance of these mutations is unclear. For Borrelia burgdorferi, although acquired resistance to some antimicrobial agents has been described, resistance due to bacterial persister cells surviving in the presence of antimicrobial, with no apparent increase in the MIC of the organism, have been recently described. Of the remaining veterinary fastidious pathogens, Lawsonia intracellularis is the most interesting from an antimicrobial resistance perspective because it can only be grown in cell culture, making in vitro susceptibility testing challenging. MIC testing has been undertaken on a small number of isolates, and some differences in susceptibility to macrolides have been demonstrated between isolates obtained from different regions.

Lawsonia intracellularis in the feces of wild rodents and stray cats captured around equine farms

BACKGROUND

Proliferative enteropathy is a global enteric disease of particular importance in pigs. The causative bacterium, Lawsonia intracellularis, has a wide range of susceptible host species. Recently, L. intracellularis has been recognized as an etiologic agent of an emerging enteric disease in foals called equine proliferative enteropathy (EPE). The presence of L. intracellularis in nonruminant wildlife has raised questions regarding the role of these species in EPE transmission.

RESULTS

This study investigated exposure to L. intracellularis in wild rodents and feral cats from eight farms with confirmed EPE. Serum (42) and fecal (40) samples from resident foals and fecal samples (131), intestinal mucosa tissues (14), and mesenteric lymph nodes (14) from wild and feral animals were collected for the evaluation of the farm status and the molecular detection of L. intracellularis following the diagnosis of EPE in index cases. Fresh feces from wild rodents and feral cats were collected from the ground while walking the premises or after trapping the animals using live traps. A total of 3 brown rats, 7 house mice, 1 striped field mouse, 2 grey red-backed voles, and 3 feral cats showed evidence of prior exposure to L. intracellularis.

CONCLUSIONS

Our data add to increasing evidence demonstrating the potential for L. intracellularis transmission and infection in wild rodents and feral cats and provide possible evidence of interspecies transmission. The exposure of wild rodents and feral cats provides potential evidence for the spillover of L. intracellularis to wildlife species and raises the question of spillback to horses. Additionally, these animals may represent an indicator of environmental exposure or may be actively involved in the transmission of L. intracellularis to foals by acting as potential reservoir/amplifier hosts. This study is the first to demonstrate the magnitude of L. intracellularis shedding in the feces of wild rodents and feral cats and to indicate the significant infection risk that wild rodents and feral cats pose to naïve horses in South Korea.

Draft Genome Sequence of Lawsonia intracellularis Strain E40504, Isolated from a Horse Diagnosed with Equine Proliferative Enteropathy

Reported herein is the draft genome sequence of equine-origin Lawsonia intracellularis strain E40504, an obligate intracellular bacterium and the etiological agent of equine proliferative enteropathy. The 1.69-Mb draft genome sequence includes 1,380 protein-coding genes and 49 RNA genes, and it lacks a genomic island reported in swine-origin L. intracellularis strain PHE/MN1-00.

Equine proliferative enteropathy on a Brazilian farm

Abstract:Lawsonia intracellularis infection on a horse farm in the Midwest region of Brazil is described. Thirty-nine foals a few days to months old from a herd with 300 horses, experienced diarrhea with variable characteristics and intensities, weight loss, hyperemic mucous membranes and dehydration. In foals 3 to 6 months of age, hypoproteinemia associated with submandibular edema were also common. Intestinal fragments of a 7-month-old foal were sent to an animal disease laboratory for diagnosis. The observed macroscopic lesions were hyperemic serosa, thickening of the intestinal wall with a corrugation, thickening of the mucosa folds and reduction of intestinal lumen. Histological analysis of the small and large intestine revealed enterocyte hyperplasia of the crypts associated with diffuse marked decrease in the number of goblet cells and positive L. intracellularis antigen labeling by immunohistochemistry. Three out of 11 animals of the same property were seropositive for L. intracellularis, demonstrating the circulation of the agent throughout the farm, but none were PCR positive in fecal samples. Based on clinical signs and pathological findings, the diagnosis of equine proliferative enteropathy was confirmed.