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March 10, 1997


Christine Gilbert, Letters Editor
Science
1333 H Street, NW
Washington D.C. 20005

Dear Editor:

Please consider the following letter in response to Mr. Drollettes's second article attempting to put a nice light on the unfortunate escape of Rabbit Hemorrhagic Disease in Australia.

"It kills, it doesn't appear to jump species and best of all...rabbit hemorrhagic disease (RHD)--so far--is working exactly as Australian animal control and health officials hoped when they released the deadly agent...". These are the words of freelance writer Dan Drollette published in Science 10 January 1997.¹ In stark contrast, the news and headlines in Australia read "Rabbit Virus a Flop",² 75% failure at 350 virus release sites, and Federated Farmers reporting that, after the virus had been released, "rabbit numbers are at their highest in decades."² Primary Industries Minister John Anderson, who approved the RHD virus release nationwide, assessing the failures saying "we do not know quite how and why it spreads", and "I am a little disappointed...in some areas it has been patchy".²

Oddly, the bungled Wardang Island experiments foretold these events. Exposed rabbits were unaffected in three of seven open-pen experiments.³

In New Zealand "The Ministry of Health considers the scientific validity of the assessment of rabbit calicivirus disease provided (by Australia) to be questionable and does not support the introduction of the virus."⁴ In their assessment, the New Zealand Association of Scientists "strongly oppose approval of the application" to import RHD because "the exposure to risks far outweigh the benefits". They continue "the application itself is unbalanced and deceptive...resulting in spurious assurances of safety". And "the consequences for New Zealand could be catastrophic."⁵

In Geelong Australia, infectivity studies on 34 non-rabbit species were reported negative except for "low levels" of antibodies in mice and Kiwis.⁶ In contrast, others report a two-to-seventeen fold antibody increase in 11 of the 34 species, presumably because of infection.^6,7 Reported failure to detect virus in test animals using RT-PCR⁸ may be explained in part by failure to examine early blood samples.⁹

Possible human health effects of RHD exposure were assessed by comparing 153 individuals having RHD contact with 116 having no contact.¹⁰ When the number of reported illnesses were standardized over time¹¹ there was a three-fold (3.7% vs 12.6%) increase in the exposed group. These increases were for fever/flu-like, gastrointestinal, and neurological illnesses.^10,11 Might we now ask, is RHD our newest emerging zoonosis? Surely these preliminary findings demand a more in-depth investigation.

Thank you for considering my letter.

Highest regards,



Alvin W. Smith, DVM, PhD
Head, Laboratory for Calicivirus Studies

References:

1. Drollette, D., Science 275:154 (1997)

2. Aubin, T., Weekly Times, Victoria, 3 March (1997)

3. Coman, B.J., Environmental Impact Statement (draft) prepared for the Australian/New Zealand Rabbit Calicivirus Program, February (1996)

4. Durham, G., and the New Zealand Ministry of Health Submission to the New Zealand Ministry of Agriculture and Fisheries (Number 176) filed 17 October (1996)

5. Sissons, C.H., The New Zealand Association of Scientists Submission to the New Zealand Ministry of Agriculture and Fisheries (Number 493) filed 4 November (1996).

6. Bureau of Resource Sciences, Rabbit Calicivirus Disease, a report, Canberra Australia, pp. 38-42 August (1996)

7. Smith, A.W., Matson, D.O., Submissions to the New Zealand Ministry of Agriculture and Fisheries (Numbers 376 and 391) November (1996)

8. Gould, A.R., Kattenbelt, J.A., Lenghaus, G., Morrisy, C., Chamberlain, T., Collins, B.J., Westbury, H.A. Virus Research 47:7-17 (1997)

9. Import Impact Assessment and Application to Approve Rabbit Calicivirus Appendix G, pp. 36-38, CSIRO-AAHL Report (1996)

10. Mead, C., Kaldor, J., Catton, M., Gamer, G., Crerar, S., Thomas, S. Report of the Rabbit Calicivirus Human Health Study Group, Department of Primary Industries and Energy Australian Government (released under the official Information Act)(1996)

11. Cherry, N., Submission to the New Zealand Ministry of Agriculture and Fisheries (Number 1,000) page 19, 4 November (1996)