The risks posed by the importation of animals vaccinated against foot and mouth disease and products derived from vaccinated animals: a review.

The Terrestrial Animal Health Code of the OIE (World organisation for animal health) (the Terrestrial Code) makes recommendations for international movements of live animals and animal products because of a possible generic risk of foot and mouth disease (FMD) for these different commodities. For instance, international movement of vaccinated live animals or products of such animals is restricted due to the possible masking of clinical disease as a result of vaccination and to the perceived risk of persistently infected animals among vaccinated livestock. In addition, bilateral agreements between exporting and importing countries on the importation of animal products can be based on the 'equivalence' of the animal health conditions in both countries, or on formal or informal risk assessments in accordance with the norms and recommendations of the Terrestrial Code. In this regard, an exporting country may be required to prepare a complete and transparent document describing the animal health situation, including the factors required to assess the risk involved. Furthermore, expert committees of importing countries regularly evaluate and verify these conditions in exporting countries. The level of confidence in the information obtained by the expert committee can then be entered into the risk analysis equation. An important FMD risk reduction factor for the importation of animals and animal products is early recognition of the disease at the source of the commodity by alert stakeholders, such as official and private veterinarians and the chain of the livestock industry. This is true for all countries irrespective of their vaccination status. The risk posed by the importation of vaccinated animals becomes negligible when an adequate protocol--in compliance with the norms and recommendations of the Terrestrial Code--is applied. However, recently, export of live animals from countries that do not practise vaccination has also proven to pose a significant risk and the rules governing such transport may have to be reviewed. Disease surveillance, biosecurity at the farm level, traceability and control of the source cattle and slaughterhouse inspections are the main risk reduction measures for meat and meat products from vaccinated cattle. If these animals are slaughtered and processed under good management practice--in accordance with the norms and recommendations of the Terrestrial Code--these products present a negligible risk for the introduction of FMD. Risk reduction by maturation and deboning is an important procedure, but is probably overemphasised. Mechanical contamination of cattle carcasses with 'carrier virus' from the pharyngeal area during slaughter and processing is very unlikely. Risk assessments showed that the importation of milk products from countries or zones that practise vaccination of dairy herds poses a negligible risk. Risk assessments also demonstrated that the importation of bovine embryos from vaccinated cows--in accordance with the norms and recommendations of the Terrestrial Code--poses a negligible risk. Likewise, the risk from the importation of semen from vaccinated bulls is also negligible when an adequate test protocol is applied in accordance with the Terrestrial Code.