Modelling multi‐species and multi‐mode contact networks: Implications for persistence of bovine tuberculosis at the wildlife–livestock interface

Abstract

1 Individual-and species-level heterogeneity in contact rates can alter the ability of a pathogen to invade a host community. Many pathogens have multiple modes of transmission-by direct or indirect contact. It is important to identify the role of heterogeneity in different types of transmission when managing the risk of disease spillover at the interface among different host species.2 We developed a network-based analysis to explore how individual-and specieslevel heterogeneity shape multi-mode contact networks. We applied this networkbased approach to contact data from proximity loggers collected in a multi-species host community that contributes to the spillover of the disease bovine tuberculosis (bTB) to cattle populations in Michigan, USA. We used this approach to (a) quantify how individual-and species-level heterogeneity influence direct and indirect contacts in this system, (b) explore how management interventions to control spillovers, such as the installation of deer fences, can alter observed contact networks and c) predict the role that wildlife species have in maintaining bTB in the community.3 We found that individual-and species-level heterogeneity disproportionately influenced indirect and direct contact networks, with individual-level heterogeneity having a greater effect on indirect contact networks and species-level heterogeneity having a greater effect on direct contact networks. We also found that the installation of deer fences significantly reduced deer-specific indirect contacts.We used the results from our network analysis to show that white-tailed deer (Odocoileus virginianus) could act as the sole reservoir host for bTB in this community with important implications for understanding past bTB dynamics and managing the persistence of bTB in the future.4 Synthesis and applications. Analyses of epidemiological networks rarely account for multiple modes of contact, which can lead to an incomplete understanding of how individual-and species-level heterogeneity affect disease transmission. The

Towards a unified generic framework to define and observe contacts between livestock and wildlife: a systematic review

“…Models that incorporate empirical rather than theoretical information on the frequency and duration of contacts important for disease transmission are more likely to be useful for disease mitigation ( Craft, 2015 ). The use of a standardised definition framework in future studies of livestock-wildlife contacts would enable consistency in datasets and enable the retrospective selection of contact data relevant to a particular model, which could then be incorporated in a similar way to the data used in recent bovine tuberculosis transmission models ( Wilber et al, 2019 ; Silk et al, 2018 ). The generic unified framework proposed in this current paper could also be useful in designing livestock-wildlife contact studies, since defining the type of contact to be detected—in addition to practical considerations, such as an area’s signal strength affecting the viability of GPS device use—helps with the choice of detection method.…”

“…To mitigate wolf ( Canis lupus ) predation on sheep, for example, the effectiveness of prevention programs needs to be evaluated in ways that do not depend on livestock attacks alone, using methods such as GPS monitoring of wolf movements around sheep farm bio-fences ( Bautista et al, 2019 ; Ausband et al, 2013 ). Similarly, the effectiveness of measures taken to prevent disease transmission can also be evaluated such as by comparing deer-cattle contact rates between farms with and without deer fences installed ( Lavelle et al, 2015 ; Lavelle et al, 2016 ; Wilber et al, 2019 ). Knowledge of livestock-wildlife contacts can be used in these contexts to limit the economic loss associated with disease and predation.…”

Effects of social structure and management on risk of disease establishment in wild pigs

“…A previous study developed a method for inferring contact structure across species that included direct and indirect contact mechanisms within a single network (Wilber et al., 2019). This approach estimated the probability that two individuals (nodes) make contact (edges) within a given time frame.…”

“…However, descriptive metrics only represent contact features of the observed sample, and this approach may not detect the mechanisms underlying formation of a contact network. An alternative approach is to statistically infer contact networks using probabilistic inference from pairwise contacts (Welch et al., 2011; Wilber et al., 2019). By probabilistically modelling pairwise contacts based on covariates, we can better understand the underlying mechanisms of contact processes and propagate their uncertainty more thoroughly when the network is scaled up to a larger population (Welch et al., 2011).…”

Dynamic Network of Interactions in the Wildlife-Livestock Interface in Mediterranean Spain: An Epidemiological Point of View

“…In our case study, 63.4% of the interactions recorded with GPS devices took place in areas further than 150 m from a water point (data not shown). These would be not recorded if only water points were to be monitored, for instance only using BS [35]. It is likely that the omission of such information could result in different conclusions being made about the conformation of the network of interactions and therefore pathogen transmission.…”