Following a request from the European Commission, the Panel on Animal Health and Animal Welfare (AHAW) was asked to deliver a scientific opinion on animal health risk mitigation treatments with regard to imports of animal casings. This request is limited to casings produced from intestines and bladders of animals of the bovine, ovine, caprine, porcine and equine species.
Animal casings are imported into the European Union from a variety of third countries with different animal health status, provided that casings have been treated according to EU legislation (Commission Decision 2003/779/EC, laying down animal health requirements and the required veterinary certification for the import of animal casings from third countries). Salting with sodium chloride (NaCl) for 30 days is a well-established and accepted procedure in the casings industry worldwide, and it has been the standard animal health risk mitigation treatment prescribed in EU legislation for many years, in order to eliminate any potential animal health risk from casings. Experience has shown that, under practical conditions, the EU prescribed treatment has effectively prevented the spread or introduction of animal diseases within or into the EU via animal casings.
The request from the European Commission focused on the scientific review of: (i) improvements in the NaCl treatment that would lead to an increased level of safety to avoid transmission of animal pathogens; (ii) alternative treatments that could be developed, giving equivalent or better results in the inactivation of relevant pathogens; and (iii) assessment of the modified phosphate salt treatment recently recommended by the World Organisation for Animal Health for foot and mouth disease virus (FMDV), in particular whether it could be considered safe with regard to the elimination of animal health risks posed by pathogens other than FMDV possibly present in casings, taking into account the effects of both temperature and duration of treatment.
The list of the infectious agents of concern for the import of casings into the EU was derived from legislation on import of fresh meat (if not treated, intestines are considered fresh meat), and comprised, among others, viruses causing FMD, classical swine fever (CSF) and African swine fever (ASF), as well as bacterial infections such as brucellosis, tuberculosis and glanders. Available practices and treatments in the production of casings were reviewed, and information on general biological characteristics related to survival or inactivation of the pathogens was collected. Scientific information dealing with the effect of treatments on the survival of the relevant pathogens in casings or in a collagen-matrix model was reviewed.
For most of the infectious agents investigated, salting either with NaCl or with phosphate-supplemented NaCl showed higher efficacy at the upper range of temperature (about 20 ºC) than at 4 ºC.
FMDV in casings derived from experimentally infected animals was inactivated after treatment with NaCl for a period of 30 days at 20 ºC. However, after 30 days at 4 °C, some FMDV still remained infectious. Similar results were obtained with casings spiked with FMDV. In a three-dimensional (3D) matrix model the inactivation kinetics of FMDV in untreated and NaCl-salted samples was similar at the different temperatures tested, which emphasises the important role of temperature in inactivation.
Treatment with a phosphate-supplemented NaCl led to faster inactivation of FMDV than treatment with NaCl salt alone, both in casings derived from experimentally infected animals as well as in spiked casings. For both NaCl and phosphate-supplemented NaCl treatment a temperature of 20 ºC was more effective than lower temperatures for inactivation.
Salting of casings derived from experimentally infected animals with NaCl for a period of 30 days at room temperature (~20 °C) leads to inactivation of CSFV. However, the same treatment at low temperature (4 ºC) does not fully inactivate the virus. In a 3D matrix model an effect of NaCl salting on virus inactivation compared with the untreated controls was evident at 20 °C and 25 °C but not at 4 °C and 12 °C. Treatment with a phosphate-supplemented NaCl leads to complete inactivation of CSFV in casings derived from experimentally infected animals within 30 days.
Regarding ASFV, no studies were found dealing with inactivation on experimentally infected or spiked casings. In a 3D matrix model ASFV was readily inactivated by NaCl salting at all temperatures (4, 12, 20 and 25 °C) after 21 days. However, from its general characteristics, ASFV can be regarded as more stable than CSFV. Therefore, these results should be interpreted with caution.
There are no data available on inactivation of peste des petits ruminants virus and rinderpest virus on casings from experimentally infected animals, nor in spiked casings or in a 3D matrix model. From the general characteristics of these viruses it was assumed that they will be inactivated within 30 days at room temperature.
For swine vesicular disease virus (SVDV) there are no studies on inactivation performed with NaCl salting at room temperature. Survival of virus for at least 200 days at 4 °C has been reported in porcine casings preserved with NaCl. In a 3D matrix model SVDV showed a temperature-dependent inactivation, but, even at 20 °C with NaCl salting or 25 °C in untreated controls, some virus survived until day 30. Based on the general characteristics of SVDV, it is possible that NaCl salting for 30 days at room temperature will not completely inactivate the virus.
Brucella spp. are readily inactivated by NaCl salting, but Mycobacterium avium may survive far beyond 30 days in intestines in conditions similar to those used for salting of casings. M. bovis and other mycobacteria may show similar resistance to the salting treatment in casings, but this should be investigated.
Several other treatments have been applied to casings with the aim of inactivating infectious agents, but none of them have been extensively investigated with viruses relevant for animal health. No alternative procedures can therefore be recommended as substitutes for current salting treatments based on NaCl and phosphate-supplemented NaCl.
As there is a lack of specific scientific studies on the efficacy of bleaching and drying for pathogen inactivation in casings, these treatments cannot be recommended as stand-alone treatments, i.e. without prior salting for 30 days.