Age

PMWS is observed most often in pigs between 5 and 18 weeks of age with most cases occurring between 6 and 10 weeks of age. Reports of PMWS in adult pigs are rare. PCV2-associated lesions are typically observed from 14 to 35 days post PCV2 inoculation in experimental studies. This suggests that pigs in the field are most likely infected between 1 and 10 weeks of age. Studies investigating the influence of age on PCV2-infection are lacking. In experimental models described to date in the literature, pigs that were singularly-infected with PCV2 (no coinfection or immune stimulation) and developed clinical PMWS were between 1-21 days of age when inoculated. PMWS in older pigs was observed only in purebred Landrace pigs (35-39 days of age) (Opriessnig et al., 2006) or with additional coinfections or immune stimulation (i.e. vaccination).

References:

Opriessnig T, Fenaux M, Thomas P, Hoogland MJ, Rothschild M, Meng XJ, Halbur PG: Evidence of breed-dependent differences in susceptibility to porcine circovirus type 2-associated disease and lesions. Vet Pathol. In press, 2006a