Hall W, Neumann E. Transbound Emerg Dis.
2015 Aug;62(4):350-66. doi: 10.1111/tbed.12163. Epub 2013Sep 10.
Abstract
Porcine reproductive and respiratory
syndrome virus (PRRS) is a highly infectious virus. Experimentally, the disease
can be induced in naïve pigs by the oral, intranasal and intramuscular routes.
Depending on the virulence of the strain of the virus and the age of the pig,
peak viremia can occur within 7 days of infection, and live virus can be
isolated from blood or lymph nodes for several months post-infection. Young
pigs tend to develop higher titres of viremia than older pigs infected by the
same route and dose with the same strain of virus. Porcine reproductive and
respiratory syndrome virus survives in pork harvested from infected pigs for
extended periods at temperatures of -20 or -70°C. In experimentally infected
pigs, survival of PRRS virus in muscle held at 4°C has been demonstrated for at
least 7 days, and infectivity of the virus in these samples was confirmed
by bioassay. The optimal pH range for the survival of PRRS virus is thought to
be 6.0 to 7.5. The elevated pH of non-meat tissues (generally one pH unit
higher) is likely to favour extended survival of PRRS virus in pig carcasses
from which all superficial and deep lymph nodes have not been removed. It is
likely that exsanguinated carcasses held at 4°C retain sufficient blood or lymph
tissue to contain infective doses of PRRS virus. Porcine reproductive and respiratory
syndrome virus is rapidly inactivated by heat, providing a predictable method
to ensure that pork tissues are free of viable virus and feeding of cooked
swill or garbage should not constitute a risk to pigs. While the probability of
viable PRRS virus being present in a pig carcass may be low, the risk is not
zero. The importation of raw pork into countries where PRRS is not endemic
represents a hazard with potentially severe economic consequences.
© 2013 Blackwell Verlag GmbH. PMID:
24016101 [PubMed - in process]
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