Simple models for the impact of rabbit calicivirus disease (RCD) on Australasian rabbits

• Published in: Ecological modelling 1998-06, Vol.109 (3), p.225-241
• Main Authors: Barlow, N.D, Kean, J.M
• Format: Article
• Language: English
• Subjects: Animal viral diseases; Biological and medical sciences; Biological control; Calicivirus; Epidemiology; Fundamental and applied biological sciences. Psychology; Infectious diseases; Leporidae; Medical sciences; Microbiology; Rabbit calicivirus; Rabbits; RCD; Viral diseases; Virology
• ISSN: 0304-3800; 1872-7026
• DOI: 10.1016/S0304-3800(98)00009-X

Models are described for simple epidemics of rabbit calicivirus disease (RCD) and for its longer-term effect on non-seasonal or seasonally varying rabbit populations, assuming direct transmission or indirect transmission via free-living virus. The additional effect of juvenile immunity is examined, in which young of a certain age are immune for life if exposed. The models are parameterised from European and Australian data and used to demonstrate the relationships between disease parameters and epidemic intensity and velocity. Disease cannot persist locally, given direct transmission and the rapid epidemics observed. Given indirect transmission, disease persistence depends on the decay rate of virus in the environment and the basic reproductive rate of the disease, R 0. Again, the model suggested that local disease persistence is unlikely given the observed rapidity and intensity of epidemics, particularly in Australia, and given that a proportion of susceptibles survive exposure. If the criterion for the speed of the initial epidemic is relaxed, the models allowed persistent disease with 2-yearly outbreak patterns, as observed in European rabbit populations. Damped 2-yearly cycles in rabbit density were an intrinsic property of the rabbit/RCD system, but adding seasonally varying reproduction caused the biennial cycles to persist indefinitely. When juvenile immunity was added, disease persistence was enhanced and yearly epidemics were more likely than 2-yearly ones. In terms of RCD as a control, persistent disease generally gave around a 75% reduction in average density, while non-persistent disease gave about a 60% reduction if introduced every 3 years. The timing of introduction, whether within or outside the breeding season, appeared to have little effect on suppression and recovery.