Genotyping of Equine Lawsonia intracellularis Sampled in Japan by Using Multilocus Variable-Number Tandem Repeat Analysis.

The incidence of equine proliferative enteropathy, caused by Lawsonia intracellularis, is increasing around the world. To investigate the relationships of variable-number tandem repeat (VNTR) patterns with host species and clinical status in horses, multilocus VNTR analysis (MLVA) was applied to 98 L. intracellularis samples collected from horses, seven from pigs, seven from wildlife, one vaccine strain, and 17 public strains. The VNTR patterns were highly diverse: a total of 130 samples identified 99 distinct patterns, and the 98 horses were classified into 71 different patterns. A phylogenetic tree based on the MLVA showed three clusters: porcine, equine, and miscellaneous cluster. The equine cluster contained 46 horse samples, of which 42 (91.3%) were collected from two sampling areas. The MLVA could discriminate horse samples from pig, but the horse samples in the miscellaneous cluster could not be distinguished from wildlife samples. As for clinical data of the horses, the VNTR patterns were unrelated to horse age, clinical signs, and clinical outcomes. This study shows that VNTR patterns had no clear connection with equine clinical status, but the MLVA could be useful to investigate its epidemiological relationships, and interspecific transmission of L. intracellularis between horse and wildlife cannot be ruled out.

Metagenomic sequencing of clinical samples reveals a single widespread clone of Lawsonia intracellularis responsible for porcine proliferative enteropathy.

Lawsonia intracellularis is a Gram-negative obligate intracellular bacterium that is the aetiological agent of proliferative enteropathy (PE), a common intestinal disease of major economic importance in pigs and other animal species. To date, progress in understanding the biology of L. intracellularis for improved disease control has been hampered by the inability to culture the organism in vitro. In particular, our understanding of the genomic diversity and population structure of clinical L. intercellularis is very limited. Here, we utilized a metagenomic shotgun approach to directly sequence and assemble 21 L. intracellularis genomes from faecal and ileum samples of infected pigs and horses across three continents. Phylogenetic analysis revealed a genetically monomorphic clonal lineage responsible for infections in pigs, with distinct subtypes associated with infections in horses. The genome was highly conserved, with 94 % of genes shared by all isolates and a very small accessory genome made up of only 84 genes across all sequenced strains. In part, the accessory genome was represented by regions with a high density of SNPs, indicative of recombination events importing novel gene alleles. In summary, our analysis provides the first view of the population structure for L. intracellularis, revealing a single major lineage associated with disease of pigs. The limited diversity and broad geographical distribution suggest the recent emergence and clonal expansion of an important livestock pathogen.

LI1035, a putative effector secreted by Lawsonia intracellularis, targets the MAPK pathway and regulates actin organizationin yeast and mammalian cells.

Lawsonia intracellularis is an obligate intracellular Gram-negative bacterium that has been identified as the etiological agent of the contagious disease proliferative enteropathy (PE) in a wide range of animals, mainly pigs. The genome sequence of L. intracellularis indicates that this bacterium possess a type III secretion system (T3SS), which may assist the bacterium during cell invasion and host innate immune system evasion and could be a mechanism for inducing cellular proliferation. However, the effectors secreted by the T3SS (T3Es) of L. intracellularis have not been reported. T3Es often target conserved eukaryotic cellular processes, and yeast is an established and robust model system in which to reveal their function. By screening the growth inhibition of an ordered array of Saccharomyces cerevisiae strains expressing the hypothetical genes of L. intracellularis, LI1035 was identified as the first putative effector that inhibits yeast growth. The LI1035-induced growth inhibition was rescued in two of the 14 mitogen-activated protein kinase (MAPK) yeast haploid deletion strains, suggesting that LI1035 interacts with the components of the MAPK pathway in yeast. Phosphorylation assays confirmed that LI1035 inhibits MAPK signaling cascades in yeast and mammalian cells. Actin staining assays revealed that LI1035 regulates actin organization in yeast and mammalian cells. Taken together, these results indicate that LI1035 alters MAPK pathway activity and regulates actin organization in the host. These findings may contribute to the understanding the pathogenesis of L. intracellularis and support the use of yeast as a heterologous system for the functional analysis of pathogen-specific gene products in the laboratory.

A real-time loop-mediated isothermal amplification method for rapid detection of Lawsonia intracellularis in porcine fecal samples.

Porcine proliferative enteritis is a common diarrheal disease characterized by thickening of the intestinal mucosa in swine due to enterocyte proliferation, which is caused by Lawsonia intracellularis. In this study, a real-time loop-mediated isothermal amplification (LAMP) assay was developed to detect L. intracellularis based on the conserved region of the 16S ribosomal RNA gene. The optimal reaction conditions of the real-time LAMP was 65 °C for 60 min. The LAMP products could be detected by both real-time turbidity and direct visual inspection. The assay was specific for L. intracellularis, as no cross-reaction was observed with other pathogens. The detection limit of the real-time LAMP assay was 1.4 × 10-1pg of L. intracellularis DNA, which was the same as that of real-time PCR and approximately 100 times more sensitive than that of conventional PCR. Of the 136 clinical samples, L. intracellularis DNA was identified in 60 samples by real-time LAMP, which was the same as real-time PCR and higher than conventional PCR (36.8%, 50/136). The specific, sensitive and rapid real-time LAMP assay developed in this study could be a useful alternative tool in point-of-care (POC) diagnosis of L. intracellularis infection.

Identification of Lawsonia intracellularis putative hemolysin protein A and characterization of its immunoreactivity.

Despite the recent global increase in fatal endemic outbreaks of proliferative enteropathy (PE) caused by the obligate intracellular bacterium Lawsonia intracelluralis (LI) in the swine industry, development of effective prevention strategies or immunodiagnostic tests has been delayed due to the difficulty of cultivating this pathogen in vitro. Although several genetic analyses have been performed at the level of gene transcription after the complete genome sequence of LI was made available, the mechanism of LI infection and virulence genes remain unidentified. In the present study, we assessed the antigenic features of the LI0004 protein, which we putatively defined as Lawsonia hemolysin A (LhlyA), by employing bioinformatics tools and in vivo and in vitro protein-based molecular assays. The amino acid sequence of LhlyA showed approximately 60% homology to the hemolysin-like proteins of Bilophila wadsworthia and Desulfovibrio piger. Presence of computationally predicted linear antigenic B-cell epitopes on the LhlyA protein was demonstrated by immunoblotting; a band with a molecular mass corresponding to the predicted size of the protein was strongly recognized by sera collected from artificially infected mice. Further, in an in vivo cytotoxicity assay, no splenomegaly was observed in mice inoculated with purified LhlyA. Collectively, the data presented here suggest that the LhlyA protein is a highly immuno-reactive antigen of L. intracellullaris and can potentially be used to develop effective protection strategies against PE.

Effect of Tetracycline Dose and Treatment Mode on Selection of Resistant Coliform Bacteria in Nursery Pigs.

This study describes the results of a randomized clinical trial investigating the effect of oxytetracycline treatment dose and mode of administration on the selection of antibiotic-resistant coliform bacteria in fecal samples from nursery pigs. Nursery pigs (pigs of 4 to 7 weeks of age) in five pig herds were treated with oxytetracycline for Lawsonia intracellularis-induced diarrhea. Each group was randomly allocated to one of five treatment groups: oral flock treatment with a (i) high (20 mg/kg of body weight), (ii) medium (10 mg/kg), or (iii) low (5 mg/kg) dose, (iv) oral pen-wise (small-group) treatment (10 mg/kg), and (v) individual intramuscular injection treatment (10 mg/kg). All groups were treated once a day for 5 days. In all groups, treatment caused a rise in the numbers and proportions of tetracycline-resistant coliform bacteria right after treatment, followed by a significant drop by the time that the pigs left the nursery unit. The counts and proportions of tetracycline-resistant coliforms did not vary significantly between treatment groups, except immediately after treatment, when the highest treatment dose resulted in the highest number of resistant coliforms. A control group treated with tiamulin did not show significant changes in the numbers or proportions of tetracycline-resistant coliforms. Selection for tetracycline-resistant coliforms was significantly correlated to selection for ampicillin- and sulfonamide-resistant strains but not to selection for cefotaxime-resistant strains. In conclusion, the difference in the dose of oxytetracycline and the way in which the drug was applied did not cause significantly different levels of selection of tetracycline-resistant coliform bacteria under the conditions tested.IMPORTANCE Antimicrobial resistance is a global threat to human health. Treatment of livestock with antimicrobials has a direct impact on this problem, and there is a need to improve the ways that we use antimicrobials in livestock production. We hypothesized that antibiotic resistance development following treatment of diarrhea in nursery pigs could be reduced either by lowering the dose of oxytetracycline or by replacing the commonly used practice of flock treatment with individual or small-group treatments, since this would reduce the number of pigs treated. However, the study showed no significant difference between treatment groups with respect to the number or proportion of tetracycline-resistant coliforms selected. The most important conclusion is that under practical field conditions, there will be no added value, in terms of lowering resistance development, by exchanging flock treatment for individual or small-group treatment of nursery pigs. The reason for the lack of an effect of single-animal treatment is probably that such animals share the environment with treated animals and take up resistant bacteria from the environment.

PREVALENCE OF ANTIBODY TO AND DNA OF LAWSONIA INTRACELLULARIS IN SAMPLES FROM WILD ANIMALS IN KOREA.

We evaluated the prevalence of Lawsonia intracellularis infection in three wild animal species in Korea; the Korean water deer ( Hydropotes inermis ), Siberian roe deer ( Capreolus pygargus ), and raccoon dogs ( Nyctereutes procyonoides ). We collected 136 sera and 109 fecal samples from individuals in 10 Wildlife Rescue and Conservation Centers. Serum samples were tested for anti- L. intracellularis antibodies using a blocking enzyme-linked immunosorbent assay (bELISA), and fecal samples were subjected to a real-time PCR assay for L. intracellularis . Thirty-five (25.7%) sera and 36 (33.0%) fecal samples were positive. We found a higher proportion of positive sera (64.7%, χ2=15.439, P<0.01) and feces (58.8%, χ2=6.126, P<0.05) in raccoon dogs (χ2=11.855, P<0.01) than in the other species (20% positive sera and 29% positive feces in Korean water deer; 20% positive sera and 25% positive feces in Siberian roe deer). Our data indicate infection by L. intracellularis in Korean water deer, Siberian roe deer, and raccoon dogs throughout the country. It is imperative to know whether these infected animal species are natural hosts for L. intracellularis in addition to domestic pigs ( Sus scrofa domesticus).

Detection of enteric pathogens in Turkey flocks affected with severe enteritis, in Brazil.

Twenty-two flocks of turkeys affected by enteric problems, with ages between 10 and 104 days and located in the Southern region of Brazil, were surveyed for turkey by PCR for turkey astrovirus type 2 (TAstV-2), turkey coronavirus (TCoV), hemorrhagic enteritis virus (HEV), rotavirus, reovirus, Salmonella spp., and Lawsonia intracellularis (Li) infections. Eleven profiles of pathogen combination were observed. The most frequently encountered pathogen combinations were TCoV-Li, followed by TCoV-TAstV-2-Li, TCoV-TastV-2. Only TCoV was detected as the sole pathogen in three flocks. Eight and 19 flocks of the 22 were positive for TAstV-2 and TCoV, respectively. Six were positive for Salmonella spp. and L. intracellularis was detected in 12 turkey flocks. Reovirus and HEV were not detected in this survey. These results throw new light on the multiple etiology of enteritis in turkeys. The implications of these findings and their correlation with the clinical signs are comprehensively discussed, illustrating the complexity of the enteric diseases.

Recent advances in understanding the pathogenesis of Lawsonia intracellularis infections.

Proliferative enteropathy is an infectious disease caused by an obligate intracellular bacterium, Lawsonia intracellularis, and characterized by thickening of the intestinal epithelium due to enterocyte proliferation. The disease is endemic in swine herds and has been occasionally reported in various other species. Furthermore, outbreaks among foals began to be reported on breeding farms worldwide within the past 5 years. Cell proliferation is directly associated with bacterial infection and replication in the intestinal epithelium. As a result, mild to severe diarrhea is the major clinical sign described in infected animals. The dynamics of L. intracellularis infection in vitro and in vivo have been well characterized, but little is known about the genetic basis for the pathogenesis or ecology of this organism. The present review focuses on the recent advances regarding the pathogenesis and host-pathogen interaction of L. intracellularis infections.

The critical threshold of Lawsonia intracellularis in pig faeces that causes reduced average daily weight gains in experimentally challenged pigs.

Serology indicates that Lawsonia intracellularis infection is widespread in many countries, with most pigs seroconverting before 22 weeks of age. However, the majority of animals appear to be sub-clinically affected, demonstrated by the low reported prevalence of diarrhoea. Production losses caused by sub-clinical proliferative enteropathy (PE) are more difficult to diagnose, indicating the need for a quantitative L. intracellularis assay that correlates well with disease severity. In previous studies, increasing numbers of L. intracellularis in pig faeces, quantified with a real time polymerase chain reaction (qPCR), showed a strong negative correlation with average daily gain (ADG). In this study, the association between faecal L. intracellularis numbers and PE severity was examined in two L. intracellularis experimental challenge trials (n1=32 and n2=95). The number of L. intracellularis shed in individual faeces was determined by qPCR on days 0, 7, 14, 17 and 21 days post challenge, and average daily gain was recorded over the same period. The severity of histopathological lesions of PE was scored at 21 days post challenge. L. intracellularis numbers correlated well with histopathology severity and faecal consistency scores (r=0.72 and 0.68, respectively), and negatively with ADG (r=-0.44). Large reductions in ADG (131 g/day) occurred when the number of L. intracellularis shed by experimentally challenged pigs increased from 10(7) to 10(8)L. intracellularis, although smaller ADG reductions were also observed (15 g/day) when the number of L. intracellularis increased from 10(6) to 10(7)L. intracellularis.

Species-specificity of equine and porcine Lawsonia intracellularis isolates in laboratory animals.

Lawsonia intracellularis infection causes proliferative enteropathy (PE) in many mammalian species, with porcine and equine proliferative enteropathy (PPE and EPE) known worldwide. Hamsters are a well-published animal model for PPE infection studies in pigs. There is no laboratory animal model for EPE infection studies and it is not known whether there is species-specificity for equine or porcine isolates of L. intracellularis in animal models. The objective of this study was to determine whether it is possible to generate typical EPE lesions in hamsters after inoculation with an equine strain of L. intracellularis (EPE strain) and whether it is comparatively possible to generate PPE lesions in rabbits after inoculation with a porcine strain of L. intracellularis (PPE strain). In 2 separate trials, 4-week-old and 3-week-old weanling golden Syrian hamsters were challenged with EPE strains and compared to uninfected (both trials) and PPE-infected controls (Trial 2 only). Concurrently, 6 female New Zealand white juvenile rabbits were infected with PPE strain and observed concomitantly to 8 similar rabbits infected with EPE strain for a different experiment. Hamsters and rabbits were observed for 21 to 24 days post-infection (DPI), depending on the experiment. Neither infected species developed clinical signs. The presence of disease was assessed with diagnostic techniques classically used for pigs and horses: immune-peroxidase monolayer assay on sera; quantitative polymerase chain reaction (qPCR) detection of molecular DNA in feces; and hematoxylin and eosin (H&E) stain and immunohistochemistry (IHC) on intestinal tissues. Our results showed that EPE-challenged hamsters do not develop infection when compared with PPE controls (IHC, P = 0.009; qPCR, P = 0.0003). Conversely, PPE-challenged rabbits do not develop typical intestinal lesions in comparison to EPE-challenged rabbits, with serological response at 14 DPI being significantly lower (P = 0.0023). In conclusion, PPE and EPE strains appear to have different host-specificities for hamsters and rabbits, respectively.

L'infection par Lawsonia intracellularis provoque une entéropathie proliférative chez de nombreuses espèces de mammifères; celle des porcins (EPP) et des équidés (EEP) sont connues mondialement. Les hamsters sont un modèle animal bien connu pour l'étude de l'EPP. Il n'existe pas de modèle animal de laboratoire pour étudier l'EEP, et on ne sait pas s'il y a spécificité d'espèce pour les isolats équins ou porcins de L. intracellularis dans des modèles animaux. L'objectif de la présente étude était de déterminer s'il est possible de générer des lésions typiques d'EEP chez les hamsters après inoculation d'une souche équine de L. intracellularis (souche EEP) et s'il est également possible de générer des lésions d'EPP chez des lapins après inoculation d'une souche porcine de L. intracellularis (souche EPP). Dans 2 essais séparés, des hamsters dorés syriens sevrés âgés de 4 semaines et de 3 semaines ont été inoculés avec des souches EEP, et ont été comparés à des témoins non infectés (les deux essais) et à des témoins infectés avec EPP (essai 2 seulement). Parallèlement, 6 jeunes lapines Nouvelle-Zélande ont été infectées par la souche EEP et observées de façon concomitante à 8 lapins similaires infectés par la souche EPP pour une expérience différente. Les hamsters et les lapins ont été observés pendant 21 à 24 jours après l'infection (JAI), en fonction de l'expérience. Aucune des espèces infectées n'a développé de signes cliniques. La présence de maladie a été évaluée par des techniques classiques de diagnostic utilisées pour les porcs et les chevaux : l'essai par immuno-peroxydase sur monocouche pour les sérums; la détection par réaction d'amplification en chaîne par la polymérase quantitative (qPCR) de l'ADN moléculaire dans les selles; la coloration hématoxyline-éosine et l'immunohistochimie (IHC) sur des tissus intestinaux. Nos résultats ont montré que les hamsters inoculés avec EEP ne développent pas d'infection comparativement aux EPP témoins (IHC P = 0,009; qPCR P = 0,0003). À l'inverse, les lapins inoculés avec EPP ne développent pas des lésions intestinales typiques comparativement aux lapins inoculés avec EEP, avec une réponse sérologique à 14 JAI significativement plus faible (P = 0,0023). En conclusion, les souches d'EPP et d'EEP semblent avoir des spécificités d'hôte différentes chez les hamsters et les lapins, respectivement.(Traduit par Dr. J.M. Dhillon).

Comparative genome sequencing identifies a prophage-associated genomic island linked to host adaptation of Lawsonia intracellularis infections.

Lawsonia intracellularis is an obligate intracellular bacterium and the causative agent of proliferative enteropathy (PE). The disease is endemic in pigs, emerging in horses and has also been reported in a variety of other animal species, including nonhuman primates. Comparing the whole genome sequences of a homologous porcine L. intracellularis isolate cultivated for 10 and 60 passages in vitro, we identified a 18-kb prophage-associated genomic island in the passage 10 (pathogenic variant) that was lost in the passage 60 (non-pathogenic variant). This chromosomal island comprises 15 genes downstream from the prophage DLP12 integrase gene. The prevalence of this genetic element was evaluated in 12 other L. intracellularis isolates and in 53 infected animals and was found to be conserved in all porcine isolates cultivated for up to 20 passages and was lost in isolates cultivated for more than 40 passages. Furthermore, the prophage region was also present in 26 fecal samples derived from pigs clinically affected with both acute and chronic forms of the disease. Nevertheless, equine L. intracellularis isolates evaluated did not harbor this genomic island regardless of the passage in vitro. Additionally, fecal samples from 21 clinically affected horses and four wild rabbits trapped in horse farms experiencing PE outbreaks did not show this prophage-associated island. Although the presence of this prophage-associated island was not essential for a virulent L. intracellularis phenotype, this genetic element was porcine isolate-specific and potentially contributed to the ecological specialization of this organism for the swine host.

Comparative transcriptional analysis of homologous pathogenic and non-pathogenic Lawsonia intracellularis isolates in infected porcine cells.

Lawsonia intracellularis is the causative agent of proliferative enteropathy. This disease affects various animal species, including nonhuman primates, has been endemic in pigs, and is an emerging concern in horses. Non-pathogenic variants obtained through multiple passages in vitro do not induce disease, but bacterial isolates at low passage induce clinical and pathological changes. We hypothesize that genes differentially expressed between pathogenic (passage 10) and non-pathogenic (passage 60) L. intracellularis isolates encode potential bacterial virulence factors. The present study used high-throughput sequencing technology to characterize the transcriptional profiling of a pathogenic and a non-pathogenic homologous L. intracellularis variant during in vitro infection. A total of 401 genes were exclusively expressed by the pathogenic variant. Plasmid-encoded genes and those involved in membrane transporter (e.g. ATP-binding cassette), adaptation and stress response (e.g. transcriptional regulators) were the categories mostly responsible for this wider transcriptional landscape. The entire gene repertoire of plasmid A was repressed in the non-pathogenic variant suggesting its relevant role in the virulence phenotype of the pathogenic variant. Of the 319 genes which were commonly expressed in both pathogenic and non-pathogenic variants, no significant difference was observed by comparing their normalized transcription levels (fold change±2; p<0.05). Unexpectedly, these genes demonstrated a positive correlation (r(2) = 0.81; p<0.05), indicating the involvement of gene silencing (switching off) mechanisms to attenuate virulence properties of the pathogenic variant during multiple cell passages. Following the validation of these results by reverse transcriptase-quantitative PCR using ten selected genes, the present study represents the first report characterizing the transcriptional profile of L. intracellularis. The complexity of the virulence phenotype was demonstrated by the diversity of genes exclusively expressed in the pathogenic isolate. The results support our hypothesis and provide the basis for prospective mechanistic studies regarding specific roles of target genes involved in the pathogenesis, diagnosis and control of proliferative enteropathy.

Prevalence of Lawsonia intracellularis, Salmonella spp. and Eimeria spp. in healthy and diarrheic pet rabbits.

A total of 170 fresh fecal samples (healthy; n=137, diarrheic; n=33) were collected from pet rabbits. By using PCR and formol-ether concentration method, a total 13/137 healthy rabbit feces were positive for L. intracellularis, 6/137 for Salmonella, and 13/137 for Eimeria. On the other hand, a total 17/33 diarrheic rabbit fecal samples were positive for L. intracellularis, 10/33 for Salmonella, and 21/33 for Eimeria. From these results, more than 20% of clinically normal and 97% of diarrheic rabbits were positive for single or concurrent infection of three pathogens. To the best of our knowledge, this is the first report to describe the prevalence of the microorganisms L. intracellularis, Salmonella and Eimeria in pet rabbits.

Analysis of bacterial load and prevalence of mixed infections with Lawsonia intracellularis, Brachyspira hyodysenteriae and/or Brachyspira pilosicoli in German pigs with diarrhoea.

Lawsonia (L.) intracellularis, Brachyspira (B.) hyodysenteriae and B. pilosicoli are important pathogens in domestic pig production world-wide, responsible for porcine intestinal adenomatosis, swine dysentery, and porcine intestinal spirochetosis, respectively. Conventional PCR is the major diagnostic tool in the detection of the three pathogens, but the sole detection of bacterial DNA might lead to misinterpretations of results with respect to their clinical relevance, especially with mixed infections. Thus, the present study targeted the detection and quantification of the three pathogens in samples from herds with a case history of diarrhoea. Herds and samples were selected by the practitioners on a voluntary basis. Results were based on 1176 individual samples from 95 herds from Southern Germany. The pathogens were detected simultaneously by multiplex real-time PCR. The overall prevalence for L. intracellularis, B. hyodysenteriae and B. pilosicoli was 12.6%, 8.4% and 3.2% in faecal samples and 48.4%, 24.2% and 31.6% in herds, respectively. Sixty one percent, 82.6%, and 73.4% of herds positive for L. intracellularis, B. hyodysenteriae, and B. pilosicoli, respectively, had mixed infections. Median log values of DNA equivalents/g of faeces for L. intracellularis, B. hyodysenteriae and B. pilosicoli were 3.3, 5.9 and 3.2, with maxima of 8.3, 8.0 and 6.3, respectively. Within herd prevalence of B. hyodysenteriae and B. pilosicoli as well as the load of B. hyodysenteriae were significantly associated with the severity of diarrhoea.

The use of quantitative PCR for identification and quantification of Brachyspira pilosicoli, Lawsonia intracellularis and Escherichia coli fimbrial types F4 and F18 in pig feces.

Four quantitative PCR (qPCR) assays were evaluated for quantitative detection of Brachyspira pilosicoli, Lawsonia intracellularis, and E. coli fimbrial types F4 and F18 in pig feces. Standard curves were based on feces spiked with the respective reference strains. The detection limits from the spiking experiments were 10(2) bacteria/g feces for Bpilo-qPCR and Laws-qPCR, 10(3)CFU/g feces for F4-qPCR and F18-qPCR. The PCR efficiency for all four qPCR assays was between 0.91 and 1.01 with R(2) above 0.993. Standard curves, slopes and elevation, varied between assays and between measurements from pure DNA from reference strains and feces spiked with the respective strains. The linear ranges found for spiked fecal samples differed both from the linear ranges from pure culture of the reference strains and between the qPCR tests. The linear ranges were five log units for F4-qPCR, and Laws-qPCR, six log units for F18-qPCR and three log units for Bpilo-qPCR in spiked feces. When measured on pure DNA from the reference strains used in spiking experiments, the respective log ranges were: seven units for Bpilo-qPCR, Laws-qPCR and F18-qPCR and six log units for F4-qPCR. This shows the importance of using specific standard curves, where each pathogen is analysed in the same matrix as sample DNA. The qPCRs were compared to traditional bacteriological diagnostic methods and found to be more sensitive than cultivation for E. coli and B. pilosicoli. The qPCR assay for Lawsonia was also more sensitive than the earlier used method due to improvements in DNA extraction. In addition, as samples were not analysed for all four pathogen agents by traditional diagnostic methods, many samples were found positive for agents that were not expected on the basis of age and case history. The use of quantitative PCR tests for diagnosis of enteric diseases provides new possibilities for veterinary diagnostics. The parallel simultaneous analysis for several bacteria in multi-qPCR and the determination of the quantities of the infectious agents increases the information obtained from the samples and the chance for obtaining a relevant diagnosis.

Porcine proliferative enteropathy in Estonian pig herds: histopathology and detection of Lawsonia intracellularis by PCR.

Lawsonia intracellularis is the causative agent of proliferative enteritis in pigs (PPE). This bacterium is difficult to culture from clinical samples and antemortem demonstration is therefore usually performed by PCR on faecal samples. The aim of this study was to elucidate the frequency of L. intracellularis infection in pig herds in Estonia using PCR, histopathological methods and electronmicroscopical studies. The frequency of demonstration of L. intracellularis was highest in 9-12 weeks old pigs (68.1%). It was more frequent in growing pigs with enteritis on small farms where the system of "all-in all-out" was not practiced and where standards of hygiene were poor. Gross and histopathological studies demonstrated that characteristic macroscopic changes associated with PPE were localised to the distal jejunum and ileum.Thickened longitudinal and circumferential folds occurred in the mucosa of the affected regions of the bowel. Samples from pigs aged 4 to 20 weeks exhibited the most intensive inflammatory changes. The distal part of the jejunum, ileum and the upper third of proximal colon and cecum wall were visibly thickened with reduced luminal diameter. Hyperplasia of lymphoid tissue and, in many cases, pseudomembranous or fibrinous inflammation was found. L. intracellularis was detected in 56 young pigs using histopathological methods. Additionally, in 8 of these pigs intracellular bacteria were demonstrated in ilial epithelial cells by transmission electronmicroscopical (TEM) investigation. On the basis of these TEM investigations it was concluded that L. intracellularis causes disturbances of normal growth, differentiation and apoptosis of the epithelial cells of ileum.

Comparison of feces versus rectal swabs for the molecular detection of Lawsonia intracellularis in foals with equine proliferative enteropathy.

The purpose of the current study was to compare the molecular detection rate of Lawsonia intracellularis between feces and rectal swabs collected from 42 foals with suspected equine proliferative enteropathy (EPE). Fecal samples and rectal swabs were processed for DNA purification by using an automated extraction system. The purified DNA was then analyzed by real-time polymerase chain reaction (PCR) for the presence of the aspartate ammonia lyase (aspA) gene of L. intracellularis. Absolute quantitation was calculated by using a standard curve for L. intracellularis and expressed as copy numbers of the aspA gene of L. intracellularis per microliter of purified DNA. The combined PCR detection rate for L. intracellularis was 90%, with 38 foals testing PCR positive in feces (33 samples), rectal swabs (32), or both (27). Six foals tested PCR positive only in feces, whereas 5 tested positive only in rectal swabs. Feces yielded a significantly higher aspA gene copy number of L. intracellularis than rectal swabs. Feces and rectal swabs tested PCR negative from 4 foals. In conclusion, the results showed that feces yielded similar numbers of PCR-positive results, with a higher L. intracellularis aspA gene load than rectal swabs. By analyzing dual samples, the PCR detection rate for L. intracellularis increased from 76% and 79% for rectal swabs and feces, respectively, to 90%. Rectal swabs should be considered as an alternative sample type for EPE-suspected patients with decreased or no fecal output.

Evaluation of Lawsonia intracellularis infection in a group of pigs in a subclinically affected herd from weaning to slaughter.

The purpose of this study was to follow the course of a subclinical Lawsonia (L.) intracellularis infection in a group of 60 pigs on a commercial farm from weaning to slaughter. From 6 to 16 and at 26 weeks of age, rectal faecal samples and blood samples were collected weekly from every pig for examination by PCR and blocking ELISA, respectively. At corresponding times starting at 8 weeks of age, pigs were randomly selected for necropsy (n=51). Intestinal tissues were examined histopathologically and by immunohistochemistry (IHC) for L. intracellularis antigen. Infection with L. intracellularis showed a mainly subclinical course. Shedding of L. intracellularis was detected by PCR in three pigs as early as 6 weeks of age and persisted up until 14 weeks of age. In most pigs shedding of L. intracellularis was seen only for 1-2 weeks followed by a rapid serum antibody response. More than 50% of pigs had seroconverted by week 10. At slaughter, 30.8% of investigated animals were still found to be seropositive by ELISA. Of the 60 study animals 39 were found positive by faeces PCR (65.0%), 49 animals were found positive by serology (81.7%), and 35 pigs (68.6%) had positive results by IHC at necropsy. All but one pig were found to be L. intracellularis infected by at least one of the three methods (98.3%). In conclusion, this is the first field study revealing the presence of prominent histological lesions characteristic for L. intracellularis infection and associated positive pathogen specific PCR and immunohistological results even in subclinically infected pigs. Although intestinal alterations disappeared after 3-4 weeks, L. intracellularis was detected by IHC for a longer time, especially in intestinal lymph nodes.

A multiplex real-time PCR for the simultaneous detection and quantitation of Brachyspira hyodysenteriae, Brachyspira pilosicoli and Lawsonia intracellularis in pig faeces.

A multiplex real-time PCR assay was developed to detect and quantify B. hyodysenteriae, B. pilosicoli, and L. intracellularis in pig faeces. Specific probes and primers were directed against the NADH oxidase (nox) gene of Brachyspira and the aspartate ammonia lyase (aspA) gene of L. intracellularis, respectively. The analytical sensitivity for the real-time PCR assay, expressed as limit of detection (LOD) was below 10 DNA copies for L. intracellularis, 14 DNA copies for B. pilosicoli and 26 DNA copies per PCR reaction for B. hyodysenteriae. The experimental sensitivity, expressed as limit of quantitation (LOQ) for the real-time PCR assay was set to 100 DNA copies per PCR reaction which equals 8 x 10(3) cells per gram of faeces. The multiplex real-time PCR was tested in parallel to conventional PCR on 749 faecal samples from 121 farms. 73 (9.7%), 30 (4%), and 30 (4%) faecal samples were positive for L. intracellularis, B. hyodysenteriae, and B. pilosicoli, respectively by conventional PCR and 59 (7.9%), 27 (3.6%), and 7 (0.9%) by multiplex real-time PCR. From the real-time PCR positive results 34 (4.5%), 25 (3.3%), and 4 (0.5%) were above the LOQ. The multiplex real-time PCR will allow rapid and quantitative detection of clinical relevant amounts of the three key porcine enteric pathogens simultaneously.