Age-Dependent Susceptibility to Porcine Circovirus Type 2 Infections is Likely Associated with Declining Levels of Maternal Antibodies

Porcine circovirus associated disease (PCVAD) was most commonly observed in 12- to 16-week-old pigs, based on submissions to a diagnostic lab in the Midwest between 2003 and 2010, according to researchers at Iowa State University. Under experimental conditions, they found that 12-week-old pigs had significantly lower PCV2 antibody levels than younger pigs at the time of inoculation and significantly higher PCV2 viraemia levels after PCV2 inoculation. The effect of passively acquired antibodies protecting against PCV2 challenge was less evident in older pigs.

15 February 2012

3 minute read

By: Jackie Linden

Hui-Gang Shen of the College of Veterinary Medicine at Iowa State University and co-authors there and at National Veterinary Services Laboratories in Ames have investigated the relationships between age, porcine circovirus type 2 (PCV2) viraemia, and pathologic lesions by evaluating the age of porcine circovirus associated disease- (PCVAD-) affected pigs submitted to Iowa State University Veterinary Diagnostic Laboratory between 2003 and 2010 and by experimentally infecting pigs of different ages.

In a paper published in the Journal of Swine Health and Production, they explain that a total of 3,565 PCVAD cases were selected and ages of PCVAD-affected pigs summarised. Sixty-two pigs were randomly assigned to three groups and inoculated with PCV2 at two weeks (AGE-2; n=21), seven weeks (AGE-7; n=20) or 12 weeks of age (AGE-12; n=21).

A portion of the pigs in each group arbitrarily selected by the farm manager were vaccinated with an adjuvanted vaccine (Mycoplasma hyopneumoniae) at one week of age. All pigs were euthanised 14 days post inoculation (DPI). Lesions and viremia were compared among groups.

Among the PCVAD cases received from 2003 to 2010, 47.6 per cent were 12 to 16 weeks of age. AGE-12 pigs had significantly lower levels of PCV2 antibody than with AGE-2 and AGE-7 pigs at the time of inoculation, and AGE-12 pigs had significantly higher levels of PCV2 viraemia at seven and 14 days post-inoculation.

Mycoplasma hyopneumoniae–vaccinated pigs in the AGE-12 group had higher levels of PCV2 viraemia than non-vaccinated pigs but the effect was not seen in younger pigs.

The Iowa researchers concluded that, under field conditions, 12- to 16-week-old pigs are most commonly affected by PCVAD. Under experimental conditions, 12-week-old pigs are more susceptible to PCV2 infection than are two- and seven-week-old pigs.

Reference

Shen H.G., C.M. Loiacono, P.G. Halbur and T. Opriessnig. 2012. Age-dependent susceptibility to porcine circovirus type 2 infections is likely associated with declining levels of maternal antibodies. J Swine Health Prod. 20(1):17–24.