Porcine Reproductive and Respiratory Syndrome (PRRS) caused by PRRS virus (PRRSV)(Wensvoort et al. 1992) was first recognised in North America in 1987, in Europe in 1990 and in the UK in 1991. The prevalence of PRRS ranges from 33.6% (National Animal Disease Service, UK, 2010) (UK data) to 39.8% (Evans, Medley and Green 2008) (GB data). The presence of endemic PRRSV supresses immunity and hightens suceptibility to other infections.
(Evans et al. 2010) highlights the importance of transmission of virus between herds, whilst re-introduction has been shown (Holtkamp et al. 2010) on previously PRRS negative farms, where external risks including introduction of replacement pigs from other herds were shown to be significant in re-introduction.
Daniel Franklin's Research
Endemic diseases such as Porcine Reproductive and Respiratory Syndrome (PRRS) is a persistent and heavy burden on the pig industry in Great Britain. I investigate the transmission and persistence of these diseases, with emphasis on the metapopulation (i.e. between herd) processes. Mathematical models have been developed to explore potential control and intervention strategies. A continuous time stochastic model framework to simulate the demographic processes (birth, death, movement) and transmission of disease through a metapopulation has been developed. Each farm in the metapopulation is comprised of 6 demographic groups representing the life cycles of pigs in a commercial herd. Pig movement data (RADAR) are used to characterise farm-types and their connections within the metapopulation. This is then used to inform 'scenario' networks for use in the modelling. The networks of pig farms can be complex, and do not apparently conform to “perceived wisdom”. One result is that the impact of specific control interventions have to be considered differentially at farm and network levels, and the optimum policy is not necessarily the same for both perspectives, i.e. what minimises disease in the pig population does not minimise disease in the individual farms. My research is sponsored by BPEX.