A quantitative assessment of the risk of introducing foot and mouth disease virus into the United States via cloned bovine embryos.

The trade of livestock or their products between nations requires information on the risk of introducing infectious agents such as foot and mouth disease virus (FMDV). Although transmission pathways for FMDV vary, a recent concern in the United States (USA) is that it might enter via cloned embryos. A quantitative risk assessment model was developed to determine the scenarios (with mathematical probabilities) that could lead to the introduction and maintenance of FMDV via the importation of cloned bovine embryos. Using @RISK software with Monte Carlo simulation involving 50,000 iterations, the probability of introducing FMDV via cloned embryos was estimated to be 3.1 x 10(-7). Given the current cloning protocol, and assuming the annual importation of 250 to 1,700 (mean = 520) cloned embryos, the expected number of infected embryos ranges from 1.1 x 10(-7) to 4.4 x 10(-3) (mean = 1.6 x 10(-4)) per year. Critical pathway analysis showed that the risk of FMDV entering the USA by this route is extremely low.