Infection of naïve, free-living brushtail possums (Trichosurus vulpecula) with the nematode parasite Parastrongyloides trichosuri and its subsequent spread

Cowan, P. E.; Ralston, M.J.; Heath, D.D.; Grant, Warwick N.

doi:10.1016/j.ijpara.2005.11.004

Cited by 17 publications

(7 citation statements)

References 13 publications

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“…While actual introductions of wild type P. trichosuri to possums in the field free of the parasite have been observed to establish readily (Cowan et al 2006; as predicted by the simulation model here), introduction of parasites containing chromosomally-inherited transgenes to already infected hosts is predicted to need numbers sufficient to swamp the wild type parasite if the theoretical limits (or close to the limits) are to be achieved. It is under these circumstances that other factors relating to the transgene introduction become more important, with the relative effort required to establish sufficient transgene-expressing parasites for population control being far greater if the transgene is recessive as opposed to dominant and/or introduced in heterozygous as opposed to homozygous parasites (Table 3).…”

Section: Discussionmentioning

confidence: 74%

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

Tompkins¹

2007

New Zealand Journal of Zoology

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I consider how two fundamental aspects of parasitology and population genetics-macroparasite aggregation among hosts and the HardyWeinberg 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.

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Section: Discussionmentioning

confidence: 74%

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

Tompkins¹

2007

New Zealand Journal of Zoology

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“…Studies on P. trichosuri dynamics in the field have demonstrated dispersal from a single artificial infection site in the Upper South Island to an area of approximately 6000 ha within 3 years (Cowan et al 2006). By releasing a second genetically distinguishable worm strain at the same site 4 years after the initial release, it was further demonstrated that a new strain could be established and persist (at least in the short term) alongside existing strains in the field (Warwick N Grant & Phil E Cowan unpubl.…”

Section: Species-specific Infectious Agents As Transmissible Vectors:mentioning

confidence: 99%

Could recombinant technology facilitate the realisation of a fertility-control vaccine for possums?

Cross

Zheng

Duckworth

et al. 2011

New Zealand Journal of Zoology

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While lethal control remains the primary tool for possum control in New Zealand, there has been substantial research effort over the last decade into controlling possum populations by reducing the animals' breeding potential. In particular, the potential of immunological control to reduce fertility has been investigated, whereby the possums' immune system is induced to react against its reproductive system, in order to block or destroy key components of the reproductive process. Two of the most targeted key components have been the blocking of circulating hormones (e.g. gonadotrophin-releasing hormone) and the inhibition of functional egg surface proteins (e.g. zona pellucida). While some success has been achieved for each approach, three main obstacles remain to the development of a working fertility-control vaccine for possums: first, ensuring that the vaccine remains efficacious in oral-delivery formulation; second, ensuring sufficient levels of fertility reduction; and third, ensuring that the induced immune response is sustained for a duration sufficient for long-term suppression of reproduction. The use of a genetically modified recombinant organism (parasite, bacterium or virus) to deliver a fertility-control vaccine could satisfy these requirements. A strong precedent for this approach has been set already in wildlife biology, namely the oral rabies vaccine, which is based on a recombinant vaccinia virus and which has been used successfully for the last 25 years as a disease-eliminating vaccine in mesocarnivores in Europe and North America. This review outlines the different forms and examples of recombinant organisms with potential for engineering into recombinant fertilitycontrol vaccines to reduce possum reproduction; non-transmissible agents or fully-transmissible vectors are discussed, with shortcomings and benefits outlined for each.

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“…Preliminary laboratory and field trials have suggested that it may be a good candidate vector since it is possum-specific (but not speciesspecific as it can infect mountain brushtail possums (Trichosurus caninus): Viggers et al 1998), reaches high prevalence in infected possum populations, survives as a free-living stage under a range of environmental conditions and is capable of repeated reinfection after immune rejection (Cowan et al 2006). Given the potential problems associated with acquired immunity a key question is whether a genetically modified strain can compete with wild strains in the field, and this issue is currently being investigated (Cowan et al 2006).…”

Section: Virally Vectored Immunocontraceptionmentioning

confidence: 99%

Prospects for the future: is there a role for virally vectored immunocontraception in vertebrate pest management?

et al. 2007

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Virally vectored immunocontraception (VVIC) has been studied and promoted as an alternative to lethal methods for vertebrate pest control in Australia and New Zealand. Virally vectored immunocontraception offers a potentially humane and species-specific control method with potential for a good benefit-cost outcome, but its applicability for broad-scale management remains unknown. We present case studies for the house mouse, European rabbit, red fox and common brushtail possum and describe the current status of research into the use of VVIC as a broadscale pest-management tool. All case studies indicated that there are significant problems with delivery and efficacy. The current state of development suggests that VVIC is not presently a viable alternative for the management of these vertebrate pests, and it is highly unlikely that this will change in the foreseeable future. An absence of benefit-cost data also hinders decision-making, and until benefit-cost data become available it will not be clear if there are short-or longterm benefits resulting from the use of VVIC for broad-scale pest management.

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Infection of naïve, free-living brushtail possums (Trichosurus vulpecula) with the nematode parasite Parastrongyloides trichosuri and its subsequent spread

Cited by 17 publications

References 13 publications

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

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

Could recombinant technology facilitate the realisation of a fertility-control vaccine for possums?

Prospects for the future: is there a role for virally vectored immunocontraception in vertebrate pest management?

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