BioSystems 105 (2011) 300–306 Contents lists available at ScienceDirect BioSystems jo ur nal homep age : www.elsevier.com/locate /biosystems The effect of predation on the prevalence and aggregation of pathogens in prey Min Su a,∗ , Cang Hui b,∗∗ a School of Mathematics, Hefei University of Technology, Hefei 230009, China b Centre for Invasion Biology, Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa a r t i c l e i n f o Article history: Received 20 December 2010 Received in revised form 9 May 2011 Accepted 26 May 2011 Keywords: Eco-epidemiology Predation pressure Spatial structure Join-count statistics Pair approximation a b s t r a c t Although pathogens and predators have been widely used as bio-control agents against problematic prey species, little has been done to examine the prevalence and aggregation of pathogens in spatially struc- tured eco-epidemiological systems. Here, we present a spatial model of a predator–prey/host–parasite system based on pair approximation and spatially stochastic simulations, with the predation pressure indicated by predator abundance and predation rates. Susceptible prey can not only be infected by contacting adjacent infected individuals but also by the global transmission of pathogens. The disease prevalence was found to follow a hump-shaped function in response to predation pressure. Moreover, predation pressure was not always negatively correlated with pathogen aggregation as proposed from empirical studies, but depending on the level of predation pressure. Highly connected site network facil- itated the parasites infection, especially under high predation pressure. However, the connectivity of site network had no effect on the prevalence and aggregation of pathogens that can infect health prey through global transmission. It is thus possible to better design biological control strategies for target species by manipulating predation pressure and the range of pathogen transmission. © 2011 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Pathogen infection and predation are distinctive but analo- gous inter-specific interactions, with each an important field of research in its own right (Bairagi et al., 2007; Raffel et al., 2008; Mata-Machuca et al., 2010; Kihara et al., 2011). Eco-epidemiology that considers both ecological and epidemiological dynamics ties these two fields together and has attracted increasing attention (Chattopadhyay and Bariagi, 2001; Webb et al., 2007a; Bairagi et al., 2007; Su et al., 2009a; Greenman and Hoyle, 2010). Studies in eco- epidemiology have provided increasing insights to the complex dynamics in the system and their applications in conservation man- agement, such as the biological control of problematic species using their natural enemies through the interplay of disease transmission and predation (Holt and Roy, 2007; Greenman and Hoyle, 2010). For instance, although predation has been viewed as an important force to prevent successful invasion of pathogens into prey (Packer et al., 2003; Bairagi et al., 2007), the prevalence of pathogenic diseases can, nonetheless, enhance the predation risk (Hethcote et al., 2004; Hatcher et al., 2006; Williams, 2008). As such, understanding such complex processes and dynamics in eco-epidemiological systems and elucidating the impact of predation on the control of epidemics are necessary and have important implications in wildlife conser- vation and management. ∗ Corresponding author. Tel.: +86 551 2902592; fax: +86 551 2902500. ∗∗ Corresponding author. E-mail addresses: sum04@163.com (M. Su), chui@sun.ac.za (C. Hui). Theoretical studies have provided certain propositions regard- ing the impacts of predation on the pathogen loads in natural predator–prey/host–parasitoid systems (Packer et al., 2003; Bairagi et al., 2007; Roy and Holt, 2008; Williams, 2008; Greenman and Hoyle, 2010). Evidently, because predators prefer infected prey as easy targets, they can potentially alter the prevalence of disease in prey population (Hudson et al., 1992; Packer et al., 2003; Ostfeld and Holt, 2004; Hall et al., 2005; Roy and Holt, 2008). Packer et al. (2003) thus suggest that the removal of predators can be indirectly detrimental to prey and facilitate pathogen invasion and transmission (also see Bairagi et al., 2007; Williams, 2008). However, recent work has questioned the generality of Packer et al.’s proposition by demonstrating results that depend on prey’s mechanisms of population regu- lation (Holt and Roy, 2007; Roy and Holt, 2008). For instance, if considering the acquired immunity in prey, the overall rela- tionship between pathogen prevalence and predator abundance could be hump-shaped (Holt and Roy, 2007). Enhanced predation pressure (either by manipulating predator density or enhanc- ing predation efficiency) could also facilitate the transmission of a pathogen under certain circumstances (Greenman and Hoyle, 2010). Preference in predation can also have a bearing on pathogen transmission. Although studies often consider that predators pre- fer infected (less active) prey (Chattopadhyay and Bariagi, 2001; Hethcote et al., 2004; Bairagi et al., 2007), it has also been sug- gested that such preferential predation could also depend on the type of pathogens and the life-history characteristics of preda- tors (Dawkins, 1982; Bhattacharyya and Mukhopadhyay, 2010). 0303-2647/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.biosystems.2011.05.012