The transmission rate of MCMV in house mice in pens: implications for virally vectored immunocontraception
A. D. Arthur A F , C. J. Krebs A B , R. P. Pech A C , L. N. Farroway A D and G. R. Singleton A EA CSIRO Sustainable Ecosystems, GPO Box 284, Canberra, ACT 2601, Australia.
B University of British Columbia, Vancouver V6T1Z4, Canada.
C Present address: Landcare Research Ltd, Christchurch 7640, New Zealand.
D Department for Environment and Heritage, Adelaide, SA 5001, Australia.
E Present address: International Rice Research Institute, Manila 1301, The Philippines.
F Corresponding author. Email: tony.arthur@csiro.au
Wildlife Research 36(5) 386-393 https://doi.org/10.1071/WR09006
Submitted: 21 January 2009 Accepted: 23 April 2009 Published: 21 July 2009
Abstract
Pest mammals have severe economic, environmental and social impacts throughout the world. Fertility control could reduce these impacts. Murine cytomegalovirus (MCMV) is being considered as an immunocontraceptive vector to control outbreaks of house mice (Mus domesticus) in Australian grain-growing regions. For successful control, a modified MCMV must transmit at a sufficient rate to keep populations of house mice below acceptable economic thresholds. We used disease models developed previously by using observations of free-ranging wild-mouse populations to assess the transmission rate of two laboratory strains of MCMV (N1 and G4) collected in a previous experiment. Mice contained in pens were deliberately infected with the N1 strain only, or with the N1 strain followed by the G4 strain. If we assume density-dependent transmission, which is the more likely mode of transmission, we found the N1 strain of MCMV transmitted at a rate ~1/300 of the rate of field strains, and hence too slowly for successful virally vectored immunocontraception (VVIC). If transmission was frequency-dependent, the rate of transmission was ~1/3 of the rate of field strains, and hence may allow successful VVIC. The G4 strain transmitted at least as slowly as the N1 strain, and possibly much more slowly; however, we could not determine whether this was an inherent property of the G4 strain or whether it was caused by competition with the N1 strain. Given the reliance of successful VVIC on rapid transmission, we recommend that future work in any VVIC system explicitly quantifies the transmission rate of recombinant viruses relative to field strains, both in the presence and absence of competing strains.
Acknowledgements
This work was funded by the Pest Animal Control CRC and the Grains Research and Development Corporation (CSV16). This study relied on data collected by Shelley Gorman, Malcolm Lawson, Nicole Harvey, Dean Jones, Fiona Murdoch, Micah Davies, Katrina Leslie, Megan Lloyd and John Winsbury, for which we are grateful. We thank Geoff Shellam, Lyn Hinds and Chris Hardy for providing stimulating discussion on MMCV as a vector for immunocontraception. Chris Hardy, Peter Caley and two anonymous reviewers provided comments on an earlier draft of this paper. All data were collected in accordance with the Australian code of practice for the care and use of animals for scientific purposes, and was approved by the Sustainable Ecosystems Animal Ethics Committee (approval number 99/00-17).
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