Abstract:
This study aimed to determine the dynamics of serological and virological profiles against Porcine Circovirus type 2 (PCV2) infection in Thai swine herds using the in-house indirect ELISA and real-time PCR techniques. A total of 10 swine herds in Thailand were divided into two groups according to their clinical history. Group A (n=5) had clinical signs of PCV2, and was routinely vaccinated by PCV2 vaccines with production loss more than 5%. Group B (n=5) had no clinical signs of PCV2 with production loss less than 5%. Group B consisted of two subgroups: PCV2-vaccinated herds (B-Vac, n=2) and non-vaccinated herds (B-non-Vac, n=3). Serum samples (n=500) were collected from parity 1, 3 and 5 sows and at 3, 5, 9, 13, 17, 21 and 25 weeks of pigs (n=5 per age group). The result of seroprofiles of group A and B revealed similar pattern in which high antibody titers in all parity sows. However, PCV2 antiboby titers of group A at parity 1 and 5 sows were significantly higher than those of group B (p<0.05). In piglets, the titers were high at 3 weeks and gradully decreased at 5 to 9 weeks of age indicating the decline in maternal immunity. After 9 weeks, PCV2 antibodies were gardually increased until fattening period coincided with high viral loads and high percentage of production loss indicating natural infection. At 17 weeks of age, the titers of group A were significantly higher than those of group B (p<0.05). In group B, the antibody levels at 3 to 13 weeks of B-Vac were significantly lower than those of B-non-Vac. The detection of PCV2 load revealed that mean viral load of group A was higher than group B but it was not significantly different. Within group B, the PCV2 DNA load in B-Vac group was significantly lower than B-non-Vac group indicating that vaccination in non-clinical pigs could reduce viral load and risk of clinical disease. This study showed that in-house ELISA and detection of viral DNA together with PCV2 clinical expressions of pigs could indicate the dynamic of PCV2 infection within swine herds and could be beneficial for disease control.
