Abstract
A commercial pig farm with no history of porcine circovirus 2 (PCV2) or porcine reproductive and respiratory syndrome virus (PRRSV) repeatedly reported a significant reduction in body weight gain and wasting symptoms in approximately 20–30% of the pigs in the period between three and six weeks after weaning. As standard clinical interventions failed to tackle symptomatology, viral metagenomics were used to describe and monitor the enteric virome at birth, 3 weeks, 4 weeks, 6 weeks, and 9 weeks of age. The latter four sampling points were 7 days, 3 weeks, and 6 weeks post weaning, respectively. Fourteen distinct enteric viruses were identified within the herd, which all have previously been linked to enteric diseases. Here we show that wasting is associated with alterations in the enteric virome of the pigs, characterized by: (1) the presence of enterovirus G at 3 weeks of age, followed by a higher prevalence of the virus in wasting pigs at 6 weeks after weaning; (2) rotaviruses at 3 weeks of age; and (3) porcine sapovirus one week after weaning. However, the data do not provide a causal link between specific viral infections and the postweaning clinical problems on the farm. Together, our results offer evidence that disturbances in the enteric virome at the preweaning stage and early after weaning have a determining role in the development of intestinal barrier dysfunctions and nutrient uptake in the postweaning growth phase. Moreover, we show that the enteric viral load sharply increases in the week after weaning in both healthy and wasting pigs. This study is also the first to report the dynamics and co-infection of porcine rotavirus species and porcine astrovirus genetic lineages during the first 9 weeks of the life of domestic pigs.
Highlights
IntroductionThe postweaning period is a critical stage in the life of pigs, with sudden social, environmental, and immunological changes
We present the first longitudinal study on enteric viral dynamics in a herd affected by postweaning wasting complications that are not related to porcine circovirus 2 (PCV2) or porcine reproductive and respiratory syndrome virus (PRRSV) infections
We followed a farm with recurrent problems with wasting pigs, not associated with porcine circovirus 2 (PCV2) or porcine reproductive and respiratory syndrome virus (PRRSV), with the aim of providing insight into the development of the virome over time in relation to the wasting phenotype
Summary
The postweaning period is a critical stage in the life of pigs, with sudden social, environmental, and immunological changes This is sometimes associated with clinical disease problems generally referred to as ‘wasting disease’. Pigs may even die or may have to be euthanized due to cachexia—i.e., pathological physical wasting typified by a loss of weight and muscle mass, involving lipolysis, activation of the acute phase response and insulin resistance [1]. It was regarded as an occasional problem in swine husbandry for many years and was typically overlooked as it entailed marginal economic loses. The scenario drastically changed between 2008 and 2010, when several farms in North America reported a significant increase in the number and frequency of wasting disease cases [2,3]
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