Lawsonia intracellularis: Revisiting the Disease Ecology and Control of This Fastidious Pathogen in Pigs

Lawsonia intracellularis is an anaerobic obligate intracellular bacterium infecting the small intestine and infrequently also the large intestine of pigs and other animals including hamsters and horses. The infection is characterized by proliferation, hemorrhage, necrosis, or any combination commonly referred to as “ileitis,” affecting the health and production efficacy of farmed pigs. Despite decades of research on this pathogen, the pathogenesis and virulence factors of this organism are not clearly known. In pigs, prophylaxis against L. intracellularis infection is achieved by either administration of subtherapeutic levels of in-feed antibiotic growth promoters or vaccination. While the former approach is considered to be effective in L. intracellularis control, potential regulations on subtherapeutic antibiotics in many countries in the near future may necessitate alternative approaches. The potential of manipulating the gut microbiome of pigs with feed ingredients or supplements to control L. intracellularis disease burden is promising based on the current understanding of the porcine gut microbiome in general, as well as preliminary insights into the disease ecology of L. intracellularis infection accrued over the last 30 years

Understanding the pathogenesis of porcine circovirus type 2 (PCV2)-associated diseases

Porcine circovirus type 2 (PCV2) is associated with several disease manifestations in pigs including postweaning multisystemic wasting syndrome (PMWS). The hallmark microscopic lesions of PCV2-infection are lymphoid depletion or granulomatous lymphadentitis (or both) and the presence of PCV2 antigen or nucleic acids associated with the lymphoid lesions. PCV2 alone is limited in its ability to induce the full spectrum of disease and lesions associated with PMWS in pigs;PCV2 is widespread in the global swine population and in order to establish a PCV2 model in conventional pigs it was necessary to identify a method to derive pigs free of PCV2 or anti-PCV2 antibodies. We obtained more than 500 PCV2-free pigs from six seropositive breeding herds and demonstrated that segregated early weaning is an effective technique to derive PCV2-free pigs from positive breeding herds for research or for commercial production;We determined that vaccination with commercially available adjuvanted bacterins enhances PCV2 replication and PCV2-associated lesions. We also found that timing of vaccination in relationship to PCV2 infection is important in the outcome of vaccine-induced enhancement of PCV2 replication and PCV2-associated lesions;Field reports indicated that PCV2-infection may also decrease the efficacy of vaccines used at the time of PCV2 infection. When we vaccinated pigs with a modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine 14 days post PCV2 inoculation we found that PCV2 infection significantly decreased the efficacy of the PRRSV vaccine as measured by gross and microscopic lesions;It is thought that coinfections may be an important trigger for progression of PCV2 to PMWS and other PCV2-associated diseases. We experimentally confirmed that PCV2 and porcine parvovirus coinfection resulted in clinical PMWS in conventional pigs whereas singular infection does not. Coinfecting conventional pigs with PCV2 and Mycoplasma hyopneumoniae resulted in severe respiratory disease, reduced average daily gain, and severe lung and lymphoid lesions associated with PCV2-antigen in dual-infected pigs implying that M. hyopneumoniae potentiates the severity of PCV2-associated lung and lymphoid lesions and increases the incidence of PMWS;Host and virus differences may also be important in the outcome of PCV2 infection. In our conventional pig model, we found a predisposition of Landrace pigs to PCV2-associated lesions and disease when compared to Duroc and Large White pigs. Finally, we were the first to experimentally confirm that PCV2-field isolates differ significantly in virulence in our conventional pig model

SARS-CoV-2 does not infect pigs, but this has to be verified regularly

For successful xenotransplantation, freedom of the xenocraft donor from certain viral infections that may harm the organ recipient is important. A novel human coronavirus (CoV) with a respiratory tropism, designated as SARS‐CoV‐2, was first identified in January 2020 in China, but likely has been circulating unnoticed for some time before. Since then, this virus has reached most inhabited areas, resulting in a major global pandemic which is still ongoing. Due to a high number of subclinical infections, re‐infections, geographic differences in diagnostic tests used, and differences in result reporting programs, the percentage of the population infected with SARS‐CoV‐2 at least once has been challenging to estimate. With continuous ongoing infections in people and an overall high viral load, it makes sense to look into possible viral spillover events in pets and farm animals, who are often in close contact with humans. The pig is currently the main species considered for xenotransplantation and hence there is interest to know if pigs can become infected with SARS‐CoV‐2 and if so what the infection dynamics may look like. This review article summarizes the latest research findings on this topic. It would appear that pigs can currently be considered a low risk species, and hence do not pose an immediate risk to the human population or xenotransplantation recipients per se. Monitoring the ever‐changing SARS‐CoV‐2 variants appears important to recognize immediately should this change in the future

Erysipelothrix rhusiopathiae serotype 15 associated with recurring pig erysipelas outbreaks

Erysipelothrix rhusiopathiae is the causative agent of pig erysipelas and can be associated with sporadic cases or larger outbreaks of septicaemia with characteristic skin lesions or chronic polyarthritis. Within the genus Erysipelothrix, at least 6 species (Erysipelothrix rhusiopathiae, Erysipelothrix tonsillarum, Erysipelothrix species strain 1, Erysipelothrix species strain 2, Erysipelothrix species strain 3 and Erysipelothrix inopinata) and 28 serotypes (1a, 1b, 2-26 and N) have been recognised.1 E rhusiopathiae serotypes 1 and 2 are frequently isolated from clinically affected pigs, although other E rhusiopathiae serotypes have been sporadically associated with clinical disease. While there is no experimental evidence that Erysipelothrix species other than E rhusiopathiae cause disease in pigs, certain Erysipelothrix species strains have been isolated from clinical cases and from condemned carcases in abattoirs

Refinement of a colostrum-deprived pig model for infectious disease research

Well-defined pig models are useful to study the pathogenicity of newly recognized pathogens or strains in pigs and serve as animal models for some human diseases. The conventional pig model, where research pigs are sourced from commercial high-health production systems, is commonly used due to the easiness of getting pigs in a timely manner. However, freedom of the pig for the pathogen of interest is important at study start and serological assays to screen pigs for antibodies against newly identified pathogens or molecular assays detecting all possible circulating pathogen variants may not yet exist. Using colostrum-deprived (CD) pigs is a good alternative strategy to circumvent passively-acquired immunity against the pathogen of interest or exposure to pathogens shortly after birth. However, CD pigs are difficult to rear as they are highly susceptible to infections, and mortality rates in the first few days of life are often very high. Herein we report on refinement of a CD pig model with consistent survival rates of 90–100% of the piglets. • Step-by-step protocol to derive and rear CD piglets with higher expected survival rates. • Pig housing improvement minimizes the risk of disease transmission. • Infectious virus disease research pig model purpose. Method name: Colostrum-deprived pig model, Keywords: Pig model, Infectious pathogens, Colostrum-deprived pigs, Naturally-farrowed, Artificially-reare

Review of methods for the detection of Lawsonia intracellularis infection in pigs

Lawsonia intracellularis is an obligate intracellular bacterium associated with enteric disease in pigs. Clinical signs include weight loss, diarrhea, and, in some cases, sudden death. The hallmark lesion is the thickening of the intestinal mucosa caused by increased epithelial cell replication, known as proliferative enteropathy. The immune response to L. intracellularis is not well defined, and detection of the infection, especially in the early stages, is still a significant challenge. We review here the main approaches used to identify this important but poorly understood pathogen. Detection of L. intracellularis infection as the cause of clinical disease is confounded by the high prevalence of the pathogen in many countries and that several other pathogens can produce similar clinical signs. A single L. intracellularis–specific ELISA and several amplification assays are available commercially to aid detection and surveillance, although histopathology remains the primary way to reach a conclusive diagnosis. There are major gaps in our understanding of L. intracellularis pathogenesis, especially how the host responds to infection and the factors that drive infection toward different clinical outcomes. Knowledge of pathogenesis will increase the predictive value of antemortem tests to guide appropriate interventions, including identification and treatment of subclinically affected pigs in the early stages of disease, given that this important manifestation reduces pig productivity and contributes to the economic burden of L. intracellularis worldwide

Artificial Insemination and Its Role in Transmission of Swine Viruses

1. Introduction Artificial insemination (AI) in swine is not a new technique and reports as early as the 1930s (Lush, 1925) describe collecting semen for AI. However, because of farm structure changes, increasing farm sizes and separation of production stages, interest in intensive pig production is growing and AI has become a critical component in modern pig production. In 2001, nearly 60% of North American swine herds utilized AI (Singleton, 2001), a drastic increase from the estimated 5% in the 1990’s (Flowers & Esbenshade, 1993). This is still relatively low compared to the 90% or greater use of AI in Western Europe (Madsen, 2005; Maes et al., 2008). The extensive use of AI in pig reproduction in the last decade has facilitated the exchange of desirable genetic characteristics at an international level, allowing producers to make greater use of superior genetics at a lower cost than some natural-service systems (Gerrits et al., 2005). However, the growth in use of AI has increased the risk of quick and widespread transmission of venereally transmissible pathogens (Thacker et al., 1984). It has been reported that the porcine male reproductive tract is highly susceptible to viral infections (Phillips et al., 1972; Spradbrow, 1968). This, coupled with the ability of boars to produce tens to thousands of insemination doses per week and the widespread distribution of the processed semen (both nationally and internationally), further increases the risk of wide transmission of viral pathogens by semen.This book chapter is published as Opriessnig T, Giménez-Lirola LG, Halbur PG. (2012). Artificial insemination and its role in transmission of swine viruses. In: Carlos C Perez-Marin (Ed), A Bird’s-Eye View of Veterinary Medicine, pp. 255-280. InTech, Croatia. ISBN 978-953-51-0031-7. DOI: 10.5772/17961. Copyright 2012 InTech. Attribution 3.0 International (CC BY 3.0). Posted with permission