Enriched Housing Reduces Disease Susceptibility to Co-Infection with Porcine Reproductive and Respiratory Virus (PRRSV) and Actinobacillus pleuropneumoniae (A. pleuropneumoniae) in Young Pigs.

Until today, anti-microbial drugs have been the therapy of choice to combat bacterial diseases. Resistance against antibiotics is of growing concern in man and animals. Stress, caused by demanding environmental conditions, can reduce immune protection in the host, influencing the onset and outcome of infectious diseases. Therefore psychoneuro-immunological intervention may prove to be a successful approach to diminish the impact of diseases and antibiotics use. This study was designed to investigate the effect of social and environmental enrichment on the impact of disease, referred to as "disease susceptibility", in pigs using a co-infection model of PRRSV and A. pleuropneumoniae. Twenty-eight pigs were raised in four pens under barren conditions and twenty-eight other pigs were raised in four pens under enriched conditions. In the enriched pens a combination of established social and environmental enrichment factors were introduced. Two pens of the barren (BH) and two pens of the enriched housed (EH) pigs were infected with PRRSV followed by A. pleuropneumoniae, the other two pens in each housing treatment served as control groups. We tested if differences in disease susceptibility in terms of pathological and clinical outcome were related to the different housing regimes and if this was reflected in differences in behavioural and immunological states of the animals. Enriched housed pigs showed a faster clearance of viral PRRSV RNA in blood serum (p = 0.014) and histologically 2.8 fold less interstitial pneumonia signs in the lungs (p = 0.014). More barren housed than enriched housed pigs developed lesions in the lungs (OR = 19.2, p = 0.048) and the lesions in the barren housed pigs showed a higher total pathologic tissue damage score (p<0.001) than those in enriched housed pigs. EH pigs showed less stress-related behaviour and differed immunologically and clinically from BH pigs. We conclude that enriched housing management reduces disease susceptibility to co-infection of PRRSV and A. pleuropneumoniae in pigs. Enrichment positively influences behavioural state, immunological response and clinical outcome in pigs

Rectal temperature (mean ± standard error) of BHI and EHI pigs.

<p>Days of infection (ID0 and ID8) are indicated as black vertical lines. HxD: housing-day interaction effect. ‘a’ denotes higher temperatures on ID2(2) and ID8(2) as compared with other days (both p<0.001). Post hoc comparison at ID9(1) and ID9(2): **: p<0.01 and *: p<0.05.</p

Enriched Housing Reduces Disease Susceptibility to Co-Infection with Porcine Reproductive and Respiratory Virus (PRRSV) and <i>Actinobacillus pleuropneumoniae</i> (<i>A</i>. <i>pleuropneumoniae</i>) in Young Pigs - Fig 4

<p><b>Overall histology (A) and total interstitial component (B) score.</b> The central blue box indicates the lower and upper boundary at the 25% / 75% quantile of the data. The central red line indicates the median of the data. Two vertical lines extending from the central box indicate the remaining data outside the central box that are not regarded as outliers. Outliers are indicated as red crosses. ***: p<0.001; *: p<0.05.</p

Skin lesion scores (mean of a four-point scale ± standard error).

<p>(A) Front. (B) Middle. (C) Rear of the body. Blue bars: BH pigs, Red bars: EH pigs. W-1 and W+1: days before and after weaning. T-1 and T+1: days before and after transport. Black dotted vertical line indicates the separate statistical analysis of the day before weaning. HxD: housing-day interaction effect. Day effects are indicated as ‘a’ and ‘b’, bars with no common superscript differ significantly (p<0.05).</p

Experimental set up and group names.

<p>Experimental set up and group names.</p

Behaviour of BH and EH pigs (frequencies/pig/10min, mean ± standard error).

<p>(A) Oral manipulation. (B) Mounting. (C) Aggression. (D) Manipulation pen. Blue bars: BH pigs, Red bars: EH pigs. W-1 and W+1: days before and after weaning. T-1 and T+1: days before and after transport. Black dotted vertical line indicates the separate statistical analysis of the day before weaning. HxD: housing-day interaction effect. Day effects are indicated as ‘a’-‘c’, bars with no common superscript differ significantly (p<0.05). (A) Post hoc comparison of housing effect at T-1, ***: p<0.001.</p

Ethogram.

<p>Ethogram.</p

Phenotypic markers of BALF Cells (mean percentages and MFI ± standard error).

<p>Phenotypic markers of BALF Cells (mean percentages and MFI ± standard error).</p

Antibody panels for FACS.

<p>Antibody panels for FACS.</p

Absolute numbers of blood cells counts in BHI and EHI pigs (mean ± standard error).

<p>(A) WBC. (B) Lymphocytes. (C) Granulocytes. (D) Monocytes. (E) Cytotoxic T-cells. (F) NK cells. Moments of infections are represented as black vertical lines. HxD: housing-day interaction. ‘a’ denotes a significant increase between ID8 and ID9 in BHI pigs (post hoc comparison, p<0.05).</p