Cross-Sectional Study on the Sero- and Viral Dynamics of Porcine Circovirus Type 2 in the Field

Abstract

Porcine circovirus-associated diseases (PCVADs) cause considerable economic losses in industrial pork production in the field. To minimize the economic losses due to PCVAD, porcine circovirus type 2 (PCV2) vaccines have been developed, and there is widespread vaccination worldwide today. However, limited information is available concerning the current status of PCV2 infection in the field on the Asian continent. The present study aimed to assess sero- and viral dynamics of PCV2 from 12 PCV2-contaminated pig herds with vaccination against PCV2 in Southern and Central Taiwan. In particular, the level of PCV2 load during the window period for seroconversion using real-time polymerase chain reaction and a commercial enzyme-linked immunosorbent assay (ELISA) kit. Our results revealed that pig herds showed slight or no seroconversion after three to four weeks post-PCV2 immunization. The presence of PCV2 was observed during the window period for seroconversion in all herds. In conclusion, natural exposure of PCV2 occurs in the growing to fattening period, and viremia can last until slaughter. Additionally, our findings indicate that using ELISA showed the level of antibodies and aided in the understanding and surveillance of the current PCV2 status in the field.

Keywords: ELISA; porcine circovirus type 2; porcine circovirus-associated diseases; real-time PCR.

Figure 1

Comparison of maternally derived antibodies (MDA) of porcine circovirus type 2 (PCV2) on suckling piglets (only from 3 to 4-week-old piglets without PCV2 vaccination) born from different sow immunization programs against PCV2. A: sows without PCV2 vaccination; B: sows with mass vaccination; C: sow vaccination at 2–4 weeks pre-farrowing. Student’s t-test was used to assess differences in the presence of PCV2 MDA from suckling piglets born from different sow vaccination programs against PCV2. p values <0.05, <0.01, and <0.001 were considered statistically significant, highly significant, and very highly significant, respectively.

Figure 2

Serodynamic profile of porcine circovirus type 2 (PCV2) measured by BioCheck ELISA in different aged pigs born from different sow immunization programs against PCV2 from different farms. (a) sows without PCV2 vaccination (Farms A, B, C, and D); (b) sows with mass PCV2 vaccination (Farms E, F, G, and H); (c) PCV2 vaccination in sows at 2-4 weeks pre-farrowing (Farms I, J, K, and L).

Figure 3

Viremia loads (line graph, left Y axis) and detection rate (bar chart, right Y axis) of porcine circovirus type 2 (PCV2) in pigs born from sows without PCV2 vaccination group, Farms A, B, C, and D. The error bars show the standard deviation (SD) of positive samples.

Figure 4

Viremia loads (line graph, left Y axis) and detection rate (bar chart, right Y axis) of porcine circovirus type 2 (PCV2) in pigs born from the sow mass PCV2 vaccination group, Farms E, F, G, and H. The error bars show the standard deviation (SD) of positive samples.

Figure 5

Viremia loads (line graph, left Y axis) and detection rate (bar chart, right Y axis) of porcine circovirus type 2 (PCV2) in pigs born from PCV2 vaccination in sows at 2–4 weeks pre-farrowing, Farms I, J, K, and L. The error bars show the standard deviation (SD) of positive samples.