Introduction

The Co-operative Research Centre

Why Biotechnology?

How does it work ?

Will it work

Bioethics

Conclusion

References

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Introduction

It is a new approach to rabbit control in two ways - one is that it uses genetic engineering and the other is that, contrary to all usual methods of rabbit control, it effects the birth rate rather than the death rate. As the project is a new and attractive hi-tech approach costing a considerable amount of money there is the possibility that it will be enthusiastically promoted and adopted without due consideration. As in any genetic manipulation the ethical issues, the possible social and ecological outcomes, both positive and negative should be considered.

It is not my aim to encourage or discourage the project, but to review it and to examine the issues that it raises.

The Cooperative Research Centre

Initial development on the concept from 1985-92 was funded by the Wool Research and Development Corporation and CSIRO. The CRC is funded by five partners which are:

• Commonwealth Government
• CSIRO
• 
  
  

  
  

  Why Biotechnology?

  Problems with some of the current control methods such as 1080 poisoning are that they affect other species, native and exotic and are seen as inhumane. The perception of a declining impact of myxomatosis along with the environmental and ethical aspects of current control technique provided an impetus to explore a control that would be less labour intensive, more species specific, more inhumane and have a permanent effect on the population. Most control methods except for warren ripping are just temporary measures, as the population may rebound to pre control levels in 1-2 years if there is no follow up treatment.

  Relevant Links

  Biotechnology Resource List
  Ethics in Science
  
  
  

  How Does Imunocontraception Work ?

  "Immunocontraception is the process of preventing fertilisation by inducing the body's immune system to attack the reproductive cells of its own species. This process prevents the normal recognition between sperm and egg, impeding fertilisation." If enough individuals were infertile, the population would eventually decline (CRC, No.2).

  Species specific proteins from the sperm and egg are isolated and the corresponding DNA is inserted into the DNA of the myxoma virus. The myxoma virus is injected back into the rabbits blood via a vector and the immune system then makes antibodies to these proteins. The antibodies attach themselves to proteins on the sperm or egg, preventing fertilisation.

  
  
  The genetically modified myxoma will differ from other genetically modified micro-organisms in one very important respect. This is that the modified myxoma will and must to be successful, spread from animal to animal. Other genetically modified micro-organisms have been designed to not to spread. This difference makes species specificity of the utmost importance with the modified myxoma virus.

  Regulating the numbers of a pest species through controlling it's fertility by using an immunological approach has very significant advantages. The virus species specific and it does not involve toxic chemicals that would non target animals. Infected rabbits that become prey to other species do not infect the predator. It controls numbers by regulating births in the population rather than trying to kill large numbers of animals. Animal Welfare organisations consider it is more acceptable than the traditional control by mortality.

  
  
  

  Will It Work ?

  
  In an ideal situation, the virus would infect 100% of the population and infected individuals will either die or become sterile. This is a somewhat optimistic situation which will be difficult to put into practice in the field for the following reasons;
  • (a) It is not known yet if 100% of infected animals can be made sterile and it is not known how long the sterility would last.

  • (b) About 50% of rabbits in field populations have antibodies to myxomatosis and are therefore not highly susceptible to infection. Repeated introductions over many years will need to be made to sterilise a high proportion of the population. If an introduction in one year fails then it is back to square one as there will be many fertile young in the population. Recent results indicate that more than 80% of the population has to be sterilised before the population declines.

  • (c) When there are sufficient vectors available to spread the modified myxoma virus then it is probable the field myxoma will be competing/ spreading at the same time and rate. Even if the modified myxoma spreads as well as the field myxoma, only half of the susceptible population are likely to become infected by it.

  • (d) The cost of spreading the modified myxoma over Southern Australia every year has not been estimated but could be in the order of 50-100 million dollars per year. The cost of warren ripping in the same area may be in the order of 400 million dollars with a annual maintenance cost of 50 million.

  • (e) One of the major vectors of myxoma, the European rabbit flea (Spilopsyllus cunicului) depends on rabbit breeding for its own breeding and its populations may fall to levels at which the myxoma virus may not spread well in some areas.

  • (f) Each experiment conducted by the research team must apply for approval from the Genetic Manipulation Advisory Committee. GMAC has strict guidelines that must be adhered to in regards to security and ethics and it is possible that GMAC may not approve the release as it is new and high risk.

  • (g) In the field, the modified strain may be selected against and if sterility and death rate is not 100%, it could lead to selection of genetically resistant animals. Apart from nullifying the sterilising virus this will also remove potentially the most effective present day control on rabbit populations.

  There is another side to the CRC's project that needs to be mentioned here and is discussed in Impact. The rabbit is a major food supply to foxes and when rabbit numbers are low the foxes turn to prey upon native species. If rabbit populations were to decrease, then to stop the fox having from impacting severly on native species, its' population also needs to be controlled. Research into finding a vector and a species specific virus is under way to introduce imunosterilising antigens into the fox, but it will take a long time to find either. If the immunosterilisation of the rabbit is successful, the same success for the fox is predicted to take a lot longer.

  
  
  
  

  Conclusion

  The reasons advanced for the rabbit immunocontraception project are that it will;
  • (a) be more effective and cost effective than existing control methods
  • (b) promote regeneration of rangeland plants and re-establish populations of endangered animals.
  • (c) cause less suffering of rabbits and the Australian ecosystem in the long run.

  At present there is lot of enthusiasm, yet considerable doubt as to weather the scientific aims will be successful. It is impossible for we as humans to make a ethical decision about the natural environment without that decision being tainted by our own anthropocentricism and limited understanding of the whole and by our vested interest in the continuation of our own species.

  There will always be tension concerning the most appropriate actions when dealing with the manipulation of life. All thoughts are valid and should be respected. My own view is that as the rabbit is an exotic species that brings detriment to the Australian environment, its' numbers should be controlled by human interference that has minimal negative effects. Whether the immunocontraception myxoma virus will do this will remain a matter of conjecture for some time. Because of the many uncertainties in the new technology of genetic manipulation, the final decision should be conservative as the manipulated virus can always be used at a later date when some of the uncertainties have been resolved.

  
  

  

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