Animal-Based Factors Prior to Infection Predict Histological Disease Outcome in Porcine Reproductive and Respiratory Syndrome Virus- and Actinobacillus pleuropneumoniae-Infected Pigs

Ingrid D E van Dixhoorn; Dennis E Te Beest; Jantina E Bolhuis; Hendrik K Parmentier; Bas Kemp; Simon van Mourik; Norbert Stockhofe-Zurwieden; Cornelis G van Reenen; Johanna M J Rebel

doi:10.3389/fvets.2021.742877

Animal-Based Factors Prior to Infection Predict Histological Disease Outcome in Porcine Reproductive and Respiratory Syndrome Virus- and Actinobacillus pleuropneumoniae-Infected Pigs

Front Vet Sci. 2021 Nov 17:8:742877. doi: 10.3389/fvets.2021.742877. eCollection 2021.

Authors

Ingrid D E van Dixhoorn¹, Dennis E Te Beest², Jantina E Bolhuis³, Hendrik K Parmentier³, Bas Kemp³, Simon van Mourik⁴, Norbert Stockhofe-Zurwieden⁵, Cornelis G van Reenen¹, Johanna M J Rebel¹

Affiliations

¹ Wageningen Livestock Research, Department of Animal Health and Welfare, Wageningen, Netherlands.
² Biometris, Wageningen University & Research, Wageningen, Netherlands.
³ Adaptation Physiology Group, Wageningen University & Research, Wageningen, Netherlands.
⁴ Farm Technology Group, Wageningen University & Research, Wageningen, Netherlands.
⁵ Wageningen Bio-Veterinary Research, Lelystad, Netherlands.

Abstract

A large variety of clinical manifestation in individual pigs occurs after infection with pathogens involved in porcine respiratory disease complex (PRDC). Some pigs are less prone to develop respiratory disease symptoms. The variation in clinical impact after infection and the recovery capacity of an individual animal are measures of its resilience. In this paper, we examined which ones of a range of animal-based factors (rectal temperature, body weight, skin lesion scores, behavior, natural antibody serum levels, serum levels of white blood cells, and type of T and granulocyte subsets) when measured prior to infection are related to disease severity. These animal-based factors and the interaction with housing regimen of the piglets (conventional or enriched) were modeled using linear regression to predict disease severity using a dataset acquired from a previous study using a well-established experimental coinfection model of porcine reproductive and respiratory syndrome virus (PRRSV) and Actinobacillus pleuropneumoniae. Both PRRSV and A. pleuropneumoniae are often involved in PRDC. Histological lung lesion score of each animal was used as a measure for PRDC severity after infection. Prior to infection, higher serum levels of lymphocytes (CD3⁺), naïve T helper (CD3⁺CD4⁺CD8^-), CD8⁺ (as well as higher relative levels of CD8⁺), and memory T helper (CD3⁺CD4⁺CD8⁺) cells and higher relative levels of granulocytes (CD172^a) were related to reduced disease severity in both housing systems. Raised serum concentrations of natural IgM antibodies binding to keyhole limpet hemocyanin (KLH) were also related to reduced disease severity after infection. Increased levels of skin lesions at the central body part (after weaning and before infection) were related to increased disease severity in conventional housing systems only. High resisters showed a lower histological lung lesion score, which appeared unrelated to sex. Body temperature, behavior, and growth prior to infections were influenced by housing regimen but could not explain the variation in lung lesion scores after infection. Raised basal lymphocyte counts and lower skin lesion scores are related to reduced disease severity independent of or dependent on housing system, respectively. In conclusion, our study identifies intrinsic animal-based measures using linear regression analysis that predicts resilience to infections in pigs.

Keywords: Actinobacillus pleuropneumoniae; PRRSV; animal-based factors; coping strategy; disease severity; enriched housing; porcine respiratory disease; resilience indicators.