Controlling mouse plagues in the Australian grain-growing regions using a proposed species-specific, genetically modified, immunocontraceptive (IC) murine cytomegalovirus (icMCMV) may risk infected mice infesting export cargo and, subsequently in other countries, infecting closely related, susceptible and valued Mus species.  This paper uses simple simulation models to examine (a) how design of an IC virus and deployment strategy could affect the likelihood of inadvertent export, and (b) where intervention may minimise the likelihood of export effectively and economically.  Field efficacy is best in an IC virus with an immunocontraceptive efficacy of 75?100% and high transmissibility, and the likelihood of export is lower than for some less efficacious designs.  Greatest likelihood of export arises from using an IC virus with low (or zero) immunocontraceptive efficacy and high transmissibility.  Lower transmissibility of the IC virus relative to field strains reduces field efficacy and the likelihood of export.  Conversely, higher relative transmissibility increases field efficacy and modestly increases the likelihood of export.  Effective control of mice in the field requires the IC virus to infect a high proportion of the mouse population while numbers are very low.  Deviation from this strategy through (a) underestimation of mouse abundance, and (b) late deployment during population increase, diminishes effectiveness in the field and increases the likelihood of export.  Intervention at ports seems the most effective strategy to mitigate export risk.  Australian legislation and codes of practice specify export quarantine procedures for particular types of goods but are silent for others.  Current practices for shipping container movements also leave gaps in the export quarantine barrier.