Evaluation of the persistence of porcine reproductive and respiratory syndrome virus in pig carcases

Abstract

The presence of porcine reproductive and respiratory syndrome (PRRS) virus in pig meat was assessed in samples collected from experimentally infected pigs and from the carcases of pigs from infected herds at an abattoir. In the experimental study, pigs approximately six months old were inoculated with two isolates of PRRS virus and tissue samples were collected seven and 14 days after inoculation. At seven days, PRRS virus was recovered from lungs, tonsils, lymph nodes and muscle tissues, and viral antigens were detected by immunogold silver staining (IGSS) in formalin-fixed lungs, tonsils and scattered cells in muscle tissues. Neither PRRS virus nor antigens were detected in muscle tissue samples collected 14 days after inoculation. In the abattoir pigs, attempts were made to isolate PRRS virus from a total of 44 samples of muscle tissue, collected as pools, from the carcases of 44 pigs originating from seropositive herds. No PRRS virus could be isolated on porcine alveolar macrophages from these 44 muscle tissue samples and no PRRS virus antigens could be detected by IGSS in the formalin-fixed tissue samples. Although the results of experimental infections indicated that PRRS virus may be recovered from muscle tissues early after infection with the virus, the presence of PRRS virus in muscle tissues from carcases of slaughter pigs previously exposed to the PRRS virus could not be demonstrated.

Survival of porcine reproductive and respiratory syndrome virus in fresh pork

“…For PRRSV, a D-value (time taken for a 1 log 10 reduction) was estimated to be 30 h at 4 °C (Magar et al, 1995). Following inoculation of 6-month-old piglets, PRRSV was re-isolated within 7 days post inoculation but not at 14 days (Magar et al, 1995). In another study, the virus could be isolated from only one of 72 muscle tissues collected from 18 pigs between 3 and 70 days after exposure (Mengeling et al, 1995).…”

“…Most of the previous studies attempted to detect the presence of virus in meat from experimentally infected animals. For PRRSV, a D-value (time taken for a 1 log 10 reduction) was estimated to be 30 h at 4 °C (Magar et al, 1995). Following inoculation of 6-month-old piglets, PRRSV was re-isolated within 7 days post inoculation but not at 14 days (Magar et al, 1995).…”

“…Low concentrations of PRRSV have been detected in muscle samples of experimentally infected pigs (Bloemraad et al, 1994;Magar et al, 1995;Mengeling et al, 1995), indicating the possibility of oral transmission through infected pork. In fact, oral transmission in pigs was demonstrated by using a PRRSV suspension (Magar and Larochelle, 2004) and via the feeding of pork obtained from recently infected pigs (van der Linden et al, 2003).…”

Deactivation of Porcine Reproductive and Respiratory Syndrome Virus during Microwave Heating of Bacon

“…Virus isolation procedures require at least 1 infectious virion per ml in order to give a positive result. Like the current project, various reports Magar et al [2], Larochelle and Magar [8] and Magar and Larochelle [9] have shown low but detectable levels of PRRS virus in raw meat products from PRRS-infected pigs.…”

“…Transmission of PRRS virus to recipient pigs through consumption of infected donor pig meat has been documented experimentally [1,2] providing the justification for PRRS free countries to exclude import of uncooked or minimally cooked pork products such as bacon.…”