PUZZLING OVER THE EPIDEMIOLOGY OF PORCINE CIRCOVIRUS TYPE 2.

Abstract

The present thesis aimed to provide information on porcine circovirus type 2 (PCV2) epidemiology. The four studies included in this PhD Thesis are summarised below:_x000D_ The first study aimed to assess the prevalence of PCV2 and other swine viruses, namely reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), Aujeszky’s disease virus (ADV) and porcine parvovirus (PPV) in Spanish pig herds. It was obtained that in the early-mid 2000s, PCV2 and PPV showed evidence of ubiquitous distribution in pigs; PRRSV and SIV were also widespread. Seroprevalence against ADV wild virus decreased over time. Boar studs had lower seroprevalences than sow and fattening herds._x000D_ The second work consisted in an exploratory case-control study aimed to assess risk factors that, in association with PCV2 infection, induced the expression of porcine circovirus type 2-systemic disease (PCV2-SD), a multifactorial disease. It was concluded that early infection by PCV2, measured by evidence of seroconversion, is a predisposing factor for PCV2-SD occurrence._x000D_ The third study focused on the pig genetic background, a specific risk factor for PCV2-SD. It was concluded that the genetic background is a risk factor for PCV2-SD development. Piglets from pure Pietrain boars showed the best clinical performance followed by piglets from Large White x Pietrain boars. Piglets from Large White x Duroc boars were the most affected by PCV2-SD._x000D_ Finally, the last study aimed to assess the effect of PCV2 loads in pig serum on average daily weight gain (ADWG) during the postweaning period. It was concluded that ADWG variation among pigs in PCV2-SD affected farms is partly explained by serum PCV2 load from weaning to slaughter age. Three subpopulations of pigs with different serum PCV2 loads from weaning to slaughter age were identified. These subpopulations experienced significantly different ADWG, in which the higher the PCV2 load the lower the ADWG.

Date of Award	27 Nov 2014
Original language	English
Supervisor	Joaquim Segales Coma (Director)