Characterization of the interferon gamma response to Lawsonia intracellularis using an equine proliferative enteropathy challenge (EPE) model

Lawsonia intracellularis associated equine proliferative enteropathy in Danish weanling foals

Background

Lawsonia intracellularis, an obligate intracellular bacterium, causes equine proliferative enteropathy, mainly in horses around weaning. This disease is rarely reported in the Scandinavian countries.

Results

Five cases of equine proliferative enteropathy were diagnosed between 2008–2016 at the University of Copenhagen Large Animal Teaching Hospital. Cases were Danish Warmbloods and a Friesian horse, aged 6–7 months, presenting with typical clinical signs of lethargy, poor body condition, pyrexia and diarrhea. Clinical pathology was consistent with previous reports of severe hypoalbuminemia and leukocytosis. Diagnosis was confirmed by fecal polymerase chain reaction, serum immunomonolayer peroxidase assay and/or immunofluorescence and fluorescence in situ hybridization performed on formalin-fixed ileum samples. Concurrent intestinal parasitism was present in all five cases. Treatment consisted of antimicrobial therapy, anti-inflammatories, intravenous crystalloids and plasma. Three foals were euthanised due to deterioration and poor response to treatment, one with complications of septic arthritis and Strongylus vulgaris associated intestinal infarct. The other two foals survived and were reported by the owners to be healthy on long-term follow-up.

Conclusions

Equine proliferative enteropathy is a disease to consider in young horses presenting with diarrhea and hypoproteinemia in Denmark.

Systemic cytokine response in pigs infected orally with a Lawsonia intracellularis isolate of South Korean origin

In the swine industry, Lawsonia intracellularis is one of the main enteric pathogens; it causes acute intestinal hemorrhage (proliferative hemorrhagic enteropathy) in naïve adult pigs and a wasting disease (proliferative enteropathy) in growing pigs. Among many kinds of cytokines, interferon-γ (IFN-γ) has previously been reported to play a significant role in limiting intracellular infection and increasing cellular proliferation associated with L. intracellularis. However, the levels of various circulating inflammatory cytokines, including IFN-γ, in animals infected with L. intracellularis is still an area of considerable interest for understanding immunity against this bacterium. In addition, there has been no information on cytokine response in animals infected with any L. intracellularis isolate of South Korean origin or Asian origin. To determine the relationship between the changes in the systemic inflammatory cytokine response in the peripheral blood of the host after L. intracellularis infection, we measured the levels of some pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IFN-γ), anti-inflammatory cytokines (IL-4, IL-10, and transforming growth factor-β (TGF-β)), and a chemokine (IL-8) in pigs infected with L. intracellularis isolated from South Korea. This study demonstrated that a L. intracellularis isolate of South Korean origin induced cytokine (TNF-α, IL-6, and IFN-γ) responses in infected animals within 15 days post-infection although the circulating levels of IL-4, IL-10, IL-8 and TGF-β were induced relatively late.

Lawsonia intracellularis infection and proliferative enteropathy in foals

Equine proliferative enteropathy (EPE) is a disease of foals caused by the obligate intracellular organism Lawsonia intracellularis. This organism is unique in that it causes proliferation of infected enterocytes, resulting in thickening of the intestinal epithelium, most often the small intestine. This disease affects mainly weanling foals and causes fever, lethargy, peripheral edema, diarrhea, colic and weight loss. The diagnosis of EPE may be challenging and relies on the presence of hypoproteinemia, thickening of segments of the small intestinal wall observed on abdominal ultrasonography, positive serology and molecular detection of L. intracellularis in feces. The epidemiology and genetic basis for pathogenesis for this disease is beginning to be elucidated. Phenotypic traits, genomic features, and gene expression profiles during L. intracellularis infection in vitro and in vivo are presented. In addition, this article reviews the epidemiology, pathological and clinicopathological findings, diagnosis, and control of EPE.

Equine proliferative enteropathy--a review of recent developments

Equine proliferative enteropathy (EPE) is a disease of foals caused by the obligate intracellular organism Lawsonia intracellularis. This emerging disease affects mainly weanling foals and causes fever, lethargy, peripheral oedema, diarrhoea, colic and weight loss. The diagnosis of EPE may be challenging and relies on the presence of hypoproteinaemia, thickening of segments of the small intestinal wall observed upon abdominal ultrasonography, positive serology and molecular detection of L. intracellularis in faeces. Although the clinical entity, diagnostic approach and treatment of EPE are well established and described, the epidemiology for this disease has remained largely unaddressed. This article focuses on new developments in the field of EPE, including epidemiology, pathophysiology, clinical signs, diagnosis, treatment and prevention.

The Summary is available in Chinese – see Supporting information.

The effect of an immunomodulator (parapoxvirus ovis) on cell-mediated immunity (CMI) in abruptly weaned foals

The weaning process of foals involves a period of considerable stress which likely contributes to an increased risk of infectious disease in these young horses. Mechanisms responsible for this heightened risk of infection remain unknown, although likely due to compromised cell-mediated immunity. Parapoxvirus ovis (PPVO), an immmunomodulator, has been shown to limit the severity of infectious disease outbreaks among horses and has been shown to enhance CMI responses. Thus, an objective of this study was to investigate the effect of PPVO therapy on cell-mediated immune (CMI) responses of abruptly weaned foals. A group of foals (n=6) were given an intramuscular injection of PPVO on days -2, 0 (weaning) and 9. An additional group of foals (n=5) received the diluent only on the same days serving as controls. Peripheral blood samples were collected from all foals prior to weaning (day 0) and on days 1, 3, 5, 7, 9, 11, 14, and 21 after weaning. Whole blood samples were prepared to determine in vivo cytokine mRNA expression by reverse transcription and real-time PCR (RT-PCR). Peripheral blood mononuclear cells (PBMC) were isolated and stimulated to determine in vitro cytokine production by intracellular staining using flow cytometry and gene expression was measured by RT-PCR. Cytokines analyzed in this study were interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10). Regardless of PPVO treatment, foals undergoing the weaning process showed a significant decrease in both in vivo and in vitro cytokine (IFN-γ, TNF-α and IL-10) production. These results indicate that abrupt weaning significantly impacts CMI of the foal which may increase susceptibility to infectious agents.