Low-coverage vaccination strategies for the conservation of endangered species

Division of Environmental and Evolutionary Biology, University of Glasgow, Glasgow G12 8QQ, UK.
Nature (Impact Factor: 41.46). 11/2006; 443(7112):692-5. DOI: 10.1038/nature05177
Source: PubMed


The conventional objective of vaccination programmes is to eliminate infection by reducing the reproduction number of an infectious agent to less than one, which generally requires vaccination of the majority of individuals. In populations of endangered wildlife, the intervention required to deliver such coverage can be undesirable and impractical; however, endangered populations are increasingly threatened by outbreaks of infectious disease for which effective vaccines exist. As an alternative, wildlife epidemiologists could adopt a vaccination strategy that protects a population from the consequences of only the largest outbreaks of disease. Here we provide a successful example of this strategy in the Ethiopian wolf, the world's rarest canid, which persists in small subpopulations threatened by repeated outbreaks of rabies introduced by domestic dogs. On the basis of data from past outbreaks, we propose an approach that controls the spread of disease through habitat corridors between subpopulations and that requires only low vaccination coverage. This approach reduces the extent of rabies outbreaks and should significantly enhance the long-term persistence of the population. Our study shows that vaccination used to enhance metapopulation persistence through elimination of the largest outbreaks of disease requires lower coverage than the conventional objective of reducing the reproduction number of an infectious agent to less than one.

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    • "While some evidence points to dogs serving as a potential reservoir for RABV, their role in the transmission of other pathogens like CDV and CPV to grey wolves is less clear. Dogs appears to be responsible for transmission of these diseases to other wild canids like Ethiopian wolves (Canis simensis) and African wild dogs (Lycaon pictus) (Cleaveland et al., 2001; Haydon et al., 2006; Woodroffe et al., 2012). Both CPV and CDV affect wolves (Mech et al., 1986; Bailey et al., 1995; Sobrino et al., 2008) and it has been shown they can affect wolf pup survival (Johnson et al., 1994; Mech et al., 2008). "
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    ABSTRACT: Although both wolves and dogs have been the subjects of numerous studies in many disciplines, the complex relationships between them have not yet been synthesized within a common review, and neither has it been placed in a holistic conservation context. Information and data are spread across numerous publications from different disciplines that rarely interact. Dogs have become the most common carnivore and their population is still increasing. In a context of wolf recovery in multi-use landscapes, there is a growing concern among conservationists for the potential negative impact of dogs on wolf conservation. With this paper we aim to review the numerous and complex interactions existing between wolves and dogs, using literature from disciplines as diverse as history, archeology, anthropology, genetics, ecology, and epidemiology in order to better understand the wolf–dog relationship and its potential impact on wolf conservation. Starting with their phylogenetic relationship and following a summary of the current knowledge on the dog’s ancestry we explore how dogs can represent a direct threat for wolves through hybridization, disease transfer and competition. The review highlights a number of ways in which dogs can impact wolf conservation, although a general lack of data and conclusive studies is a common theme that emerges for many topics. Then we analyse how dogs can mitigate human–wolf conflicts through their role as livestock guardians or wolf hunters. Finally we describe the complex phenomenon of wolf predation on dogs before discussing the wolf–dog relationships in general, with a special focus on including a more anthropological perspective. The review highlights the diversity of interactions between wolves and dogs, that can be both negative and positive for wolf conservation. However, more important than these direct impacts, the review highlights how the wolf–dog relationship challenges human attempts to construct simple dichotomies between wild and domestic, or between nature and culture. The borders between these concepts are in fact much more fluid and elusive than is often appreciated, and wolf conservation must adapt to this more complex reality.
    Full-text · Article · Mar 2014 · Biological Conservation
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    • "Targeting bottleneck species, such as the zebra and buffalo, is similar to the low-coverage vaccination strategy proposed by Haydon et al. (2006) for Ethiopian wolves (Canis simensis). Epidemiological models demonstrated that vaccinating wolf packs occupying habitat corridors connecting subpopulations reduced extinction risk and the size of rabies outbreaks in wolves by reducing the ability of a rabies epidemic to spread between metapopulations (Haydon et al., 2006). In our system, animals functioned as bottlenecks not by occupying certain spatial regions, such as habitat corridors, but because their long-distance ranging behavior allowed them to function as bridges between different regions of the study area. "
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    ABSTRACT: Multi-host wildlife pathogens are an increasing concern for both wildlife conservation and livestock husbandry. Here, we combined social network theory with microbial genetics to assess patterns of interspecific pathogen transmission among ten species of wild and domestic ungulates in Kenya. If two individuals shared the same genetic subtype of a genetically diverse microbe, Escherichia coli, then we inferred that these individuals were part of the same transmission chain. Individuals in the same transmission chain were interlinked to create a transmission network. Given interspecific variation in physiology and behavior, some species may function as “super-spreaders” if individuals of that species are consistently central in the transmission network. Pathogen management strategies targeted at key super-spreader species are theoretically more effective at limiting pathogen spread than conventional strategies, and our approach provides a means to identify candidate super-spreaders in wild populations. We found that Grant’s gazelle (Gazella granti) typically occupied central network positions and were connected to a large number of other individuals in the network. Zebra (Equus burchelli), in contrast, seemed to function as bridges between regions of the network that would otherwise be poorly connected, and interventions targeted at zebra significantly increased the level of fragmentation in the network. Although not usually pathogenic, E. coli transmission pathways provide insight into transmission dynamics by demonstrating where contact between species is sufficient for transmission to occur and identifying species that are potential super-spreaders.
    Full-text · Article · Jan 2014 · Biological Conservation
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    • "This could reduce costs and effort as well as involving fewer animals in the invasive procedures. Targeting particular individuals for vaccination has not yet been widely applied; however, there is some evidence indicating that vaccinating packs of Ethiopian wolves (Canis simensis) that ranged within or near a corridor connecting two subpopulations reduced the overall extent of a rabies epidemic in this species [32]. It is possible that targeting superspreaders for vaccination could provide a powerful method of disease prevention, or at least limit disease spread, in wild animal populations. "
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    ABSTRACT: Disease is a major concern for the conservation of great apes, and one that is likely to become increasingly relevant as deforestation and the rise of ecotourism bring humans and apes into ever closer proximity. Consequently, it is imperative that preventative measures are explored to ensure that future epidemics do not wipe out the remaining populations of these animals. In this paper, social network analysis was used to investigate vulnerability to disease in a population of wild orang-utans and a community of wild chimpanzees. Potential 'superspreaders' of disease - individuals with disproportionately central positions in the community or population - were identified, and the efficacy of vaccinating these individuals assessed using simulations. Three resident female orang-utans were identified as potential superspreaders, and females and unflanged males were predicted to be more influential in disease spread than flanged males. By contrast, no superspreaders were identified in the chimpanzee network, although males were significantly more central than females. In both species, simulating the vaccination of the most central individuals in the network caused a greater reduction in potential disease pathways than removing random individuals, but this effect was considerably more pronounced for orang-utans. This suggests that targeted vaccinations would have a greater impact on reducing disease spread among orang-utans than chimpanzees. Overall, these results have important implications for orang-utan and chimpanzee conservation and highlight the role that certain individuals may play in the spread of disease and its prevention by vaccination.
    Full-text · Article · Dec 2013 · PLoS ONE
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