Thankyou for your fax of September 13 with the accompanying article discussing the need for rabbit calicivirus release in New Zealand. I agree with you that the discussion of the release of the rabbit hemorrhagic disease virus in Australia and New Zealand has been co-opted by the advocates of the release and that those who wish due consideration and moderation in such a decision have not been heard are marginalized. In part, this co-opting of the content of public discussion reflects the initiative taken by the RHDV release proponents to fund and push for a program that would allow the virus release. On the other hand, the enthusiasm that the release proponents had for this virus as a biologic control agent has, in my opinion, clouded their judgement as to the wisdom of such a release. For example, prior releases of stoats and other predators for rabbits in New Zealand, although as well intentioned as this release is, it had unexpected, unintended effects that are still being dealt with. The essential information needed to justify such a release according to the law, as I understand it, is that the virus be species-specific. No data are available to justify this as a reasonable conclusion for RHDV. I recently had an opportunity to look at actual laboratory results on the sera collected from a number of species tested by CSIRO. It is clear to me, looking at that data, that CSIRO has over-interpreted their results in a way that justifies the release and does not permit other more reasonable conclusions that could be drawn from the same data. Overall, the CSIRO scientists chose to say that high test results could not mean the presence of antibody and changes in antibody levels, that other scientists would say support the observation of a seroresponse, must be evidence of no infection. In my opinion, a more reasonable interpretation of the results would be that high test results in a first sample from an animal are uninterpretable and that antibody responses are more likely to indicate infection, as is the general interpretation of most scientists looking at such data.

My general opinion is that there are no reasonable grounds for deciding that RHDV is species-specific on the basis of the CSIRO experiments, results from other countries, and historical information about the virus. In fact, it is my opinion that the evidence supports the conclusion that the virus is not species-specific. This opinion is strengthened nearly daily as new information, requested 11 months ago from CSIRO, is being made available to me by indirect routes. As an example, I have now seen tables from a scientific paper published from China that following challenge of certain species viral antigen was detected in internal organs. This is remarkably different from detection of antibody responses and such viral antigen would almost certainly be a result of active viral replication.

It is important in all of these discussions to not allow the proponents of the viral release to confuse the issues of host-switching and host range. Most scientists agree that host-switching is a rare phenomenon that must of course have occurred from time to time in the past as pathogens find new hosts in which they can replicate. Evidence for host-switching in the past is quite easy to find. For example, the pathogen Toxoplasma gondii naturally occurs in cats and as an infection in humans. It started in one species or the other. HIV certainly did not arise in humans but came from a non-human primate host. These are examples of pathogens that have switched hosts and can spread within the new hosts. The concept of host range is that if one would challenge a number of species with a pathogen one would find that the host range, the species acceptable to the pathogen, is broader than naturally occurs. Part of the reason for a more limited number of natural hosts is that mechanisms of transmission, an ecological issue, dictate a more restricted niche for pathogens than would be apparent if one used artificial mechanisms for infection. What is occuring in Australia is a deliberate artificial challenge of a continent's species with the hope that the pathogen would limit itself to one species. As a general concept, choice of RNA viruses for such activities is absurd.