Reduction of PMWS-associated clinical signs and co-infections by vaccination against PCV2

The effects of a single-dose recombinant Porcine circovirus type 2 (PCV2) open reading frame 2 (ORF2) subunit vaccine were studied in a post-weaning multisystemic wasting syndrome (PMWS)-affected pig herd. A total of 1519 3-week-old piglets were allocated randomly into two treatmentgroups and eithervaccinated against PCV2 or treated with a placebo. Study animals were followed from the time ofvaccination until the end of finishing. Onset of PCV2 viraernia and clinical signs of PMWS (wasting, cough, dyspnoea, pallor and lethargy) were observed when animals were approximately 9-10 weeks old. Compared to placebo-treated animals, vaccinated animals had a significantly reduced PCV2 viral load and duration of viraemia (p < 0.0001). This reduction in viraemia was not affected by the level of maternal anti-PCV2 antibodies present at the time of vaccination. During the period of viraernia (10-26 weeks of age) vaccinated animals exhibited a 53% reduction in mortality rate (p = 0.0010), a 4.84 kg higher body weight gain (p, < 0.0001) and a significant reduction in clinical signs (p, < 0.0004). Furthermore, lung samples of vaccinated animals had a considerably reduced number ofco-infections with PRRSV and Mycoplasma hyorhinis than lung samples of placebo-treated animals. These data indicate that vaccination against PCV2 alone protects pigs from clinical signs and co-infections associated with PMWS. (c) 2008 Elsevier Ltd. All rights reserved.