Minimum specifications for transmissible transgenic biocontrol agents for brushtail possum (Trichosurus vulpecula) population eradication

I consider how two fundamental aspects of parasitology and population genetics - macro-parasite aggregation among hosts and the Hardy-Weinberg principle - govern the theoretical impact of transgenic forms of a possum-specific nematode Parastrongyloides trichosuri, that cause female infertility, on brushtail possum (Trichosurus vulpecula) populations. Assuming chromosomal inheritance of transgenes, the conditions under which transgenic P. trichosuri would be an efficacious tool for eradication are predicted to be severely limited, given the level of aggregation with which this parasite occurs naturally in its host. These limits indicate that a transgenic form of P. trichosuri containing a chromosomally-inherited female infertility transgene, would need to cause near total infertility in all host females infected with a single such parasite, for eradication to be realistically possible. Relatively greater effort is predicted necessary to achieve thresholds for eradication when transgenic nematodes are introduced to hosts already infected by the parasite compared with populations free of the parasite. Under such circumstances, the predicted effort required is reduced if transgenes are dominant as opposed to recessive, and introduced in homozygous as opposed to heterozygous form.