The Role of Predation in Disease Control: A Comparison of Selective and Nonselective Removal on Prion Disease Dynamics in Deer

Abstract

ABSTRACT:Effective measures for controlling chronic wasting disease (CWD), a contagious prion disease of cervids, remain elusive. We review theoretic relationships between predation and hostparasite dynamics and describe a mathematical model to evaluate the potential influence of random removal through harvest or culling and selective predation by wolves (Canis lupus) upon CWD dynamics in deer (Odocoileus spp.) populations. Imposing nonselective mortality representing a 15% annual harvest or cull 51 yr after CWD introduction lowered both deer population size and steady state CWD. Selective (43) mortality at the same 15% predation rate caused a more modest reduction in deer population size accompanied by a relatively rapid decline in CWD prevalence and elimination of the disease from a closed population. The impacts of selective predation on epidemic dynamics were sensitive to assumptions on parameter estimates; however, within expected ranges, the results of selective predation were consistent and robust. We suggest that as CWD distribution and wolf range overlap in the future, wolf predation may suppress disease emergence or limit prevalence.

Behavioral Immunity Suppresses an Epizootic in Caribbean Spiny Lobsters

“…In host-parasite pathosystems involving intermediate hosts, host behavior is often altered by the parasite to enhance predation risk thus parasite transmission [47–49]. However, in pathosystems with classically defined definitive hosts, like that for the lobster-PaV1 system, predatory culling of infected hosts reduces the spread of pathogens, as demonstrated in studies of captive and wild animal populations [50–52], and supported by theoretical research [53,54]. Predatory culling could explain the steady prevalence of PaV1 among spiny lobsters following the sponge die-off, but only if increased predation on clinically infected (i.e., infectious) lobsters kept density-dependent transmission below some threshold necessary for an epizootic.…”

Systematic review of management strategies to control chronic wasting disease in wild deer populations in North America

“…Most (5/6) of the predictive modeling studies were deterministic [21–25], while only one was stochastic [20]. The predictive modeling studies used a combination of hypothetical scenarios [22, 23, 25], field observations [20–22, 24], experimental data [20, 22], and expert opinion [22] to parameterize the models.

Fig. 1PRISMA diagram summarizing literature database search

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“…Studies assessing selective removal of infected deer evaluated scenarios where this occurred with large carnivores [22], or by increased harvest of bucks which have a higher prevalence of CWD [24] or by test (varying from removing sick to detecting preclinical deer) and cull [20]. All studies evaluating selective removal did so using predictive models and all were effective under specific scenarios.…”

“…The role of predation in control of CWD was evaluated by Wild et al [22] in a deterministic predictive model. Imposing non-selective mortality (any deer) from wolves decreased population size and CWD prevalence, resulting in persistence of CWD within the simulated population.…”

“…An additional summary table of evidence for effectiveness, sources of uncertainty, and other limitations in these studies is shown in more detail (see Additional file 3). A major source of uncertainty identified in four studies [21, 23–25] and alluded to in a fifth [22] was the relative contributions of different modes, FD or DD, of CWD transmission. Other sources of uncertainty affecting CWD transmission, such as prion dynamics in the environment, were specifically identified in two studies [23, 28] and alluded to in a third [22].…”