The suitability of the nematode Parastrongyloides trichosuri (Nematoda: Strongyloididae) as a genetically modified vector for transmissible fertility control of introduced brushtail possums (Trichosurus vulpecula) is being explored in New Zealand. This review of progress in assessing the ecological and epidemiological characteristics of P. trichosuri against a set of essential properties for a suitable transmissible vector indicates that the parasite appears to have all the attributes of a highly effective vector, although additional information on persistence at low host density and on the outcome of competition between existing infection and new (recombinant) strains is needed to confirm this. Concerns have been raised about risks to possums and other marsupials in Australia from a genetically modified form of P. trichosuri. An international body with responsibility for managing consultation and debate about issues arising from the proposed use of genetically modified organisms for vertebrate pest management has been suggested as a way of addressing such concerns. A key issue remains as to which agency or group of agencies would take responsibility for such a body. A joint meeting of relevant agencies and researchers is needed urgently to begin the process of moving this issue forward.