Interaction Of myxomatosis and Rabbit Haemorrhagic Disease in wild rabbit

Fulford, G. R. and Lee, X. J. and Berman, D. and Hamilton, G. (2011) Interaction Of myxomatosis and Rabbit Haemorrhagic Disease in wild rabbit. In: MODSIM 2011 - 19th International Congress on Modelling and Simulation - Sustaining our future: Understanding and living with uncertainty, 12-16 Dec 2011, Perth, Australia.

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Increasing resistance of rabbits to myxomatosis in Australia has led to the exploration of Rabbit Haemorrhagic Disease, also called Rabbit Calicivirus Disease (RCD) as a possible control agent. While the initial spread of RCD in Australia resulted in widespread rabbit mortality in affected areas, the possible population dynamic effects of RCD and myxomatosis operating within the same system have not been properly explored. Here we present early mathematical modelling examining the interaction between the two diseases. In this study we use a deterministic compartment model, based on the classical SIR model in infectious disease modelling. We consider, here, only a single strain of myxomatosis and RCD and neglect latent periods. We also include logistic population growth, with the inclusion of seasonal birth rates. We assume there is no cross-immunity due to either disease. The mathematical model allows for the possibility of both diseases to be simultaneously present in an individual, although results are also presented for the case where co-infection is not possible, since co-infection is thought to be rare and questions exist as to whether it can occur. The simulation results of this investigation show that it is a crucial issue and should be part of future field studies.

A single simultaneous outbreak of RCD and myxomatosis was simulated, while ignoring natural births and deaths, appropriate for a short timescale of 20 days. Simultaneous outbreaks may be more common in Queensland. For the case where co-infection is not possible we find that the simultaneous presence of myxomatosis in the population suppresses the prevalence of RCD, compared to an outbreak of RCD with no outbreak of myxomatosis, and thus leads to a less effective control of the population. The reason for this is that infection with myxomatosis removes potentially susceptible rabbits from the possibility of infection with RCD (like a vaccination effect). We found that the reduction in the maximum prevalence of RCD was approximately 30% for an initial prevalence of 20% of myxomatosis, for the case where there was no simultaneous outbreak of myxomatosis, but the peak prevalence was only 15% when there was a simultaneous outbreak of myxomatosis. However, this maximum reduction will depend on other param- eter values chosen. When co-infection is allowed then this suppression effect does occur but to a lesser degree. This is because the rabbits infected with both diseases reduces the prevalence of myxomatosis.

We also simulated multiple outbreaks over a longer timescale of 10 years, including natural population growth rates, with seasonal birth rates and density dependent (logistic) death rates. This shows how both diseases interact with each other and with population growth. Here we obtain sustained outbreaks occurring approximately every two years for the case of a simultaneous outbreak of both diseases but without simultaneous co-infection, with the prevalence varying from 0.1 to 0.5. Without myxomatosis present then the simulation predicts RCD dies out quickly without further introduction from elsewhere. With the possibility of simultaneous co-infection of rabbits, sustained outbreaks are possible but then the outbreaks are less severe and more frequent (approximately yearly).

While further model development is needed, our work to date suggests that: 1) the diseases are likely to interact via their impacts on rabbit abundance levels, and 2) introduction of RCD can suppress myx- omatosis prevalence. We recommend that further modelling in conjunction with field studies be carried out to further investigate how these two diseases interact in the population.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: MODSIM papers are copyright of the Modelling and Simulation Society of Australia and New Zealand Inc. (MSSANZ), who is also the publisher of the MODSIM Proceedings. IP is retained by authors, giving them the right to use MODSIM papers for their own academic purposes, including distribution through personal/staff/organisation websites and reproduction of parts of the content in journals (with suitable acknowledgement of the MODSIM paper).
Faculty/School / Institute/Centre: Historic - Faculty of Sciences - Department of Biological and Physical Sciences (Up to 30 Jun 2013)
Faculty/School / Institute/Centre: Historic - Faculty of Sciences - Department of Biological and Physical Sciences (Up to 30 Jun 2013)
Date Deposited: 03 Jul 2018 01:19
Last Modified: 03 Jul 2018 01:19
Uncontrolled Keywords: rabbits, calicivirus, myxomatosis, RCD, RHDV, pest control
Fields of Research (2008): 05 Environmental Sciences > 0502 Environmental Science and Management > 050211 Wildlife and Habitat Management
Fields of Research (2020): 41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410407 Wildlife and habitat management
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9604 Control of Pests, Diseases and Exotic Species > 960499 Control of Pests, Diseases and Exotic Species not elsewhere classified

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