PCV2 is the main causative agent of a number of syndromes which are summarised under the specific term porcine circovirus diseases (PCVD). Among these syndromes the "postweaning multisystemic wasting syndrome" (PMWS) had the strongest economical impact in the swine industry. Until the first PCV2 vaccines became available, there had been only few options to act against the effects of the infection, namely optimising the hygiene regimen and the management procedures (e.g.
Madec´s 20-point plan). Circovac® (MERIAL, Lyon, France), an inactivated whole cell vaccine, was the first vaccine against PCV2 and has been available in Europe since 2004 under provisional licence. In the beginning, it has been used in sows and gilts for passive immunisation of piglets via colostrum intake. Since then, its application range has been expanded in November 2010 also for active immunisation of pigs from three weeks of age. In this study, the efficacy of the active immunisation of 3-week-old piglets with 0.5ml Circovac® as one-shot at weaning has been studied in a PCVD affected farm. Key parameters for the evaluation of the vaccine efficacy were especially average daily weight gain, number of underweight animals, mortality, and viremia.
The study is blinded and randomized, and was conducted in a swine farm including a fattening unit in Austria. In total, 1105 piglets from three consecutive batches were included, randomly allocated to vaccine and control group and were kept included until the end of fattening. They were weighed at birth, at weaning (3rd week of life), at the end of nursery (13th week of life), in the middle of the fattening period (21st week of life) and at the end of the fattening period (28th week of life). Clinical examination of all pigs was performed weekly and mortality was recorded. Additionally, 20% of the study animals have been selected randomly for blood sampling in order to investigate the serum for specific PCV2 IgG and IgM antibodies and for specific PCV2 DNA loads. ADWG has been improved in the vaccinated group by 64.83 g/day (p < 0.0001) in the first fattening period (13th to 21st week of life) and by 41.43 g/day (p < 0.0001) for the whole fattening period (13th to 28th week of life). The underweight-animals-rate has been reduced especially in the 21st week of life by 5.15% (p =0.044) in favour of the vaccinated group. The mortality rate has also been reduced in favour of the vaccinated group by 7.40% for the whole fattening period (p < 0.0001), the difference being most prominent in the first fattening period. As revealed by serological investigation, the main infection period took place around the end of the nursery and the very beginning of the fattening period; these findings fit well in the picture. In the same period, PCV2 viremia has been detected for the vaccinated, as well as for the control group animals. Nevertheless, the vaccinated animals had a lower level and a shortened period of viremia than the unvaccinated control animals.
Therefore, it can be concluded that the vaccination of piglets with Circovac® improved production parameters such as ADWG, reduced underweight animals rate, mortality rate and the viral shedding. All in all in this study, the vaccine has been a shown to be effective and a valuable tool against the effects of a PCV2 infection.