title: Factors affecting the infectivity of tissues from pigs with classical swine fever: thermal inactivation rates and oral infectious dose.
abstract: Outbreaks of classical swine fever are often associated with ingestion of pig meat or products derived from infected pigs. Assessment of the disease risks associated with material of porcine origin requires knowledge on the likely amount of virus in the original material, how long the virus may remain viable within the resulting product and how much of that product would need to be ingested to result in infection. Using material from pigs infected with CSFV, we determined the viable virus concentrations in tissues that comprise the majority of pork products. Decimal reduction values (D values), the time required to reduce the viable virus load by 90% (or 1 log10), were determined at temperatures of relevance for chilling, cooking, composting and ambient storage. The rate of CSFV inactivation varied in different tissues. At lower temperatures, virus remained viable for substantially longer in muscle and serum compared to lymphoid and fat tissues. To enable estimation of the temperature dependence of inactivation, the temperature change required to change the D values by 90% (Z values) were determined as 13 °C, 14 °C, 12 °C and 10 °C for lymph node, fat, muscle and serum, respectively. The amount of virus required to infect 50% of pigs by ingestion was determined by feeding groups of animals with moderately and highly virulent CSFV. Interestingly, the virulent virus did not initiate infection at a lower dose than the moderately virulent strain. Although higher than for intranasal inoculation, the amount of virus required for infection via ingestion is present in only a few grams of tissue from infected animals.
authors.affiliation: Virology Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom; Department of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD United Kingdom.
authors.forename: Lucie
authors.initials: L
authors.lastname: Cowan
authors.affiliation: Virology Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Felicity J
authors.initials: FJ
authors.lastname: Haines
authors.affiliation: Virology Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Helen E
authors.initials: HE
authors.lastname: Everett
authors.affiliation: Virology Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Bentley
authors.initials: B
authors.lastname: Crudgington
authors.affiliation: Virology Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Helen L
authors.initials: HL
authors.lastname: Johns
authors.affiliation: Animal Sciences Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Derek
authors.initials: D
authors.lastname: Clifford
authors.affiliation: Virology Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Trevor W
authors.initials: TW
authors.lastname: Drew
authors.affiliation: Virology Department, Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom. Electronic address: Helen.Crooke@apha.gsi.gov.uk.
authors.forename: Helen R
authors.initials: HR
authors.lastname: Crooke
mesh_terms: D000818:Animals; D006691:Classical Swine Fever / Q000635:transmission / Q000821:virology*; D006692:Classical Swine Fever Virus / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D005838:Genotype; D008297:Male; D008460:Meat / Q000821:virology*; D009132:Muscles / Q000821:virology; D013552:Swine; D013696:Temperature; D019562:Viral Load / Q000662:veterinary; D038301:Virus Inactivation
keywords: Classical swine fever; Meat; Oral dose; Virus inactivation, D value; Z value