Predicted foot and mouth disease virus and African swine fever virus inactivation within carcasses undergoing field decomposition in three Australian climate zones.

Australia's large populations of feral and extensively farmed livestock pose challenges to implementing response plans in the event of an Emergency Animal Disease outbreak. This study aimed to determine if a "Destroy and Let Lie" approach to carcass disposal (leaving carcasses in situ to decompose naturally after field euthanasia) would reliably inactivate Foot and Mouth Disease virus (FMDV) and African Swine Fever virus (ASFV) under Australian conditions. Ninety-five animals (24 each of cattle, sheep, goats and 23 pigs) were used across six trials, conducted in winter and summer, in three locations in Eastern Australia. After euthanasia, temperature and pH were measured at six internal anatomical sites hourly for 24 h, then less frequently for a further 24 h. Data were compared with published FMDV and ASFV inactivation thresholds to assess the likely effectiveness of field decomposition in reducing viral infectivity. Tissue pH levels generally declined for the first 6-12 h postmortem. Based on a pH threshold of <6, FMDV would be reliably inactivated in the thoracic and abdominal cavities and deep and superficial muscle sites. In contrast, no porcine tissues at any location in any season would provide inactivation of ASFV, based on a pH threshold of <3.9. "Destroy and Let Lie" appears to be a suitable approach to reduce risk of FMDV transmission from carcasses that cannot be disposed of using conventional means under Australian field conditions. This would not be the case for an ASF outbreak, where expected viral inactivation would be minimal.