Risk factors associated with Lawsonia intracellularis in English pig farms

Epidemiology Tools to Evaluate the Control of Proliferative Enteropathy in Commercial Pig Herds

Proliferative enteropathy (PE) is characterized by diarrhea and reduced weight gains in growing pigs and intestinal hemorrhage in finishers. Vaccination, antibiotic medication, and improved hygiene can control PE, but their efficacy depends upon the epidemiology of PE. This study monitored the timing and severity of PE in 84 commercial pens across seven treatments, including disinfection, vaccination, no treatment, medication with olaquindox (50, 25 and 12.5 ppm), and combined disinfection and vaccination. Vaccination with or without lime disinfection suppressed clinical signs of PE and reduced the number of excreted L. intracellularis relative to untreated pigs housed in cleaned or cleaned and disinfected pens between 9 and 17 weeks of age. Continuous olaquindox mediation to 17 weeks of age prevented L. intracellularis infection, leaving finisher pigs naïve. These finisher pigs suffered an outbreak of hemorrhagic enteropathy with significant reductions in weight gain, feed intake, and mortalities of 4.6%. Over the 13 week grow/finish period, vaccinated pigs housed in disinfected pens showed significantly higher weight gain and feed intake relative to all other treatments, equating to a weight gain difference of between 3.6 and 3.9 kg per pig. Monitoring the immune response and fecal excretion of L. intracellularis in pens of pigs enabled effective PE control strategies to be evaluated on the farm.

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.

Correlation of Lawsonia intracellularis positivity in quantitative PCR and herd factors in European pig herds

BACKGROUND

Lawsonia intracellularis is causing diarrhea, poor growth and sudden death in pigs. It can be found in most pig populations leading to large economic losses worldwide. Many potential risk factors for the occurrence of disease or seropositivity have been described. The current study therefore focused on herd characteristics in European countries associated with direct detection of the pathogen determined by quantitative polymerase chain reaction.

RESULTS

A median number of less than 30 nursery pigs per pen was correlated to less positive nursery pigs (p < 0.01) and generally less samples positive per herd (p < 0.05) as well as a lower median of genome equivalents determined per herd (p < 0.05). Routine use of zinc oxide at/ around weaning, which was mentioned by 41.0% of all farmers, was correlated to higher number of positive nursery pigs (p < 0.01) as well as higher median genome equivalents determined per herd (p < 0.05). Slatted flooring of more than 78.0% of the surface in nursery units was correlated to lower number of positive animals (p < 0.05) and a lower median of genome equivalents per herd (p < 0.05). A weight of more than 7.8 kg at weaning was correlated to a higher number of positive growing pigs (p < 0.05) as well as general higher number of positive samples/ herd (p < 0.01).

CONCLUSIONS

Weaning and subsequent accommodation of nursery pigs seem to be of particular importance in prevention of infection with Lawsonia intracellularis and the spread of the pathogen within the herd.

Toward rational selection criteria for selection of probiotics in pigs

An accurate understanding of properties of probiotics is a prerequisite for selecting probiotic organisms for use in swine production. This review aims to review selection criteria for probiotic organism in swine. The systematically investigated ecological history rather than the source of isolates should be regarded as the natural origin of probiotic strains, which helps to correct the inconsistencies arising from incorrect identification of the source. Moreover, in vivo studies are suggested as follow-up assessment to validate the characteristics of probiotic predicted by in vitro experiments. In addition, the intended probiotic effect depends on the age of the animal and disease prevention in young animals may require different probiotic strains when compared to growth promotion in older animals. With adequate selection criteria, the inclusion of probiotic in feed supplementation is a promising way to exert positive effects on sows, newborns, weanling animals and grower-finisher pigs. Both host-adapted probiotics and nomadic probiotics can be applied for pathogen inhibition but host adapted organisms appear to have a different mode of action. Host-adapted probiotic strains are likely to be associated with exclusive colonization while the nomadic or environmental strain exert better immune stimulating functions. Strains with potent enzymatic activity are fitter for grower pigs favoring feed digestion and enhancing growth performance.

EMA and EFSA Joint Scientific Opinion on measures to reduce the need to use antimicrobial agents in animal husbandry in the European Union, and the resulting impacts on food safety (RONAFA)

EFSA and EMA have jointly reviewed measures taken in the EU to reduce the need for and use of antimicrobials in food-producing animals, and the resultant impacts on antimicrobial resistance (AMR). Reduction strategies have been implemented successfully in some Member States. Such strategies include national reduction targets, benchmarking of antimicrobial use, controls on prescribing and restrictions on use of specific critically important antimicrobials, together with improvements to animal husbandry and disease prevention and control measures. Due to the multiplicity of factors contributing to AMR, the impact of any single measure is difficult to quantify, although there is evidence of an association between reduction in antimicrobial use and reduced AMR. To minimise antimicrobial use, a multifaceted integrated approach should be implemented, adapted to local circumstances. Recommended options (non-prioritised) include: development of national strategies; harmonised systems for monitoring antimicrobial use and AMR development; establishing national targets for antimicrobial use reduction; use of on-farm health plans; increasing the responsibility of veterinarians for antimicrobial prescribing; training, education and raising public awareness; increasing the availability of rapid and reliable diagnostics; improving husbandry and management procedures for disease prevention and control; rethinking livestock production systems to reduce inherent disease risk. A limited number of studies provide robust evidence of alternatives to antimicrobials that positively influence health parameters. Possible alternatives include probiotics and prebiotics, competitive exclusion, bacteriophages, immunomodulators, organic acids and teat sealants. Development of a legislative framework that permits the use of specific products as alternatives should be considered. Further research to evaluate the potential of alternative farming systems on reducing AMR is also recommended. Animals suffering from bacterial infections should only be treated with antimicrobials based on veterinary diagnosis and prescription. Options should be reviewed to phase out most preventive use of antimicrobials and to reduce and refine metaphylaxis by applying recognised alternative measures.

Serological profile, seroprevalence and risk factors related to Lawsonia intracellularis infection in swine herds from Minas Gerais State, Brazil

Background

Lawsonia intracellularis is the etiologic agent of proliferative enteropathy, which causes diarrhea in several animal species, including swine. Serology can be used both to determine the prevalence of antibodies against a specific pathogen in a herd and to obtain the serological profile, which is used to determine the dynamics of infection in the herd. The objective of this study was to determine the serological profile and seroprevalence of anti-L. intracellularis antibodies in swine herds from intensive production regions of Minas Gerais, Brazil, and to identify the risk factors related to the herd-level seropositivity.

Results

A total of 2999 serum samples were collected for this cross–sectional study in the four major regions of intensive swine production in Minas Gerais, Brazil. To obtain better estimates and increase the external validity of the seroprevalence, the sample data were weighted based on the pig population of each herd, the stratum in which the herd was classified and the swine population of the region where each herd was located. A questionnaire was used to identify potential risk factors related to this herd-level seropositivity. The overall weighted prevalence in Minas Gerais was 34.7 % (95 % confidence interval: 32.12 - 37.20 %), and there was no significant difference among the sampled regions, with the seroprevalence rates ranging between 32.06 and 37.66 %. Finishing pigs were the most prevalent among the sampled categories. Among the evaluated risk factors, “cleaning before disinfecting” had a negative impact in the seroprevalence (p < 0.05) and was considered a protective factor.

Conclusions

The anti-L. intracellularis antibodies were detected in all of the investigated herds in Minas Gerais, which indicated a wide distribution of the agent in the state. The predominant serological profile was consistent with the dynamics of infection previously observed in pig herds in other countries with similar antimicrobial usage, in which the nursery pigs usually show the lowest seroprevalence and the finishing pigs exhibit the highest. Herds that adopt the practice of “cleaning before disinfection” can decrease their L. intracellularis antibody seropositivity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0618-z) contains supplementary material, which is available to authorized users.