The scavenging behaviour of ferrets (Mustela furo), feral cats (Felis domesticus), possums (Trichosurus vulpecula), hedgehogs (Erinaceus europaeus) and harrier hawks (Circus approximans) on pastoral farmland in New Zealand: implications for bovine tuberculosis transmission

Adaptive Expression and ncRNA Regulation of Genes Related to Digestion and Metabolism in Stomach of Red Pandas during Suckling and Adult Periods

Red pandas evolved from carnivores to herbivores and are unique within Carnivora. Red pandas and carnivorous mammals consume milk during the suckling period, while they consume bamboo and meat during the adult period, respectively. Red pandas and carnivorous mammal ferrets have a close phylogenetic relationship. To further investigate the molecular mechanisms of dietary changes and nutrient utilization in red pandas from suckling to adult, comparative analysis of the whole transcriptome was performed on stomach tissues from red pandas and ferrets during the suckling and adult periods. The main results are as follows: (1) we identified ncRNAs for the first time in stomach tissues of both species, and found significant expression changes of 109 lncRNAs and 106 miRNAs in red pandas and 756 lncRNAs and 109 miRNAs in ferrets between the two periods; (2) up-regulated genes related to amino acid transport regulated by lncRNA-miRNA-mRNA networks may efficiently utilize limited bamboo amino acids in adult red pandas, while up-regulated genes related to amino acid degradation regulated by lncRNAs may maintain the balance of amino acid metabolism due to larger daily intakes in adult ferrets; and (3) some up-regulated genes related to lipid digestion may contribute to the utilization of rich nutrients in milk for the rapid growth and development of suckling red pandas, while up-regulated genes associated with linoleic acid metabolism regulated by lncRNA-miRNA-mRNA networks may promote cholesterol decomposition to reduce health risks for carnivorous adult ferrets. Collectively, our study offers evidence of gene expression adaptation and ncRNA regulation in response to specific dietary changes and nutrient utilization in red pandas during suckling and adult periods.

A global synthesis and assessment of free-ranging domestic cat diet

Free-ranging cats (Felis catus) are globally distributed invasive carnivores that markedly impact biodiversity. Here, to evaluate the potential threat of cats, we develop a comprehensive global assessment of species consumed by cats. We identify 2,084 species eaten by cats, of which 347 (16.65%) are of conservation concern. Islands contain threefold more species of conservation concern eaten by cats than continents do. Birds, reptiles, and mammals constitute ~90% of species consumed, with insects and amphibians being less frequent. Approximately 9% of known birds, 6% of known mammals, and 4% of known reptile species are identified in cat diets. 97% of species consumed are <5 kg in adult body mass, though much larger species are also eaten. The species accumulation curves are not asymptotic, indicating that our estimates are conservative. Our results demonstrate that cats are extreme generalist predators, which is critical for understanding their impact on ecological systems and developing management solutions.

Comparative study of the digestion and metabolism related genes' expression changes during the postnatal food change in different dietary mammals

The changes in the expression of genes related to digestion and metabolism may be various in different dietary mammals from juvenile to adult, especially, the giant panda (Ailuropoda melanoleuca) and red panda (Ailurus fulgens), which were once carnivores but have shifted to being specialized bamboo eaters, are unique features of their changes are more unclear. To elucidate the changing patterns of gene expression related to digestion and metabolism from juvenile to adult in different dietary mammals, we performed transcriptome analysis of the liver or pancreas in giant and red pandas, herbivorous rabbits (Oryctolagus cuniculus) and macaques (Macaca mulatta), carnivorous ferrets (Mustela putorius furo), and omnivorous mice (Mus musculus) from juvenile to adult. During the transition from juvenile to adulthood, giant and red pandas, as well as rabbits and macaques, show significant upregulation of key genes for carbohydrate metabolism, such as starch hydrolysis and sucrose metabolism, and unsaturated fatty acid metabolism, such as linoleic acid, while there is no significant difference in the expression of key genes for fatty acid β-oxidation. A large number of amino acid metabolism related genes were upregulated in adult rabbits and macaques compared to juveniles. While adult giant and red pandas mainly showed upregulation of key genes for arginine synthesis and downregulation of key genes for arginine and lysine degradation. In adult stages, mouse had significantly higher expression patterns in key genes for starch hydrolysis and sucrose metabolism, as well as lipid and protein metabolism. In contrast to general expectations, genes related to lipid, amino acid and protein metabolism were significantly higher expressed in adult group of ferrets, which may be related to their high metabolic levels. Our study elucidates the pattern of changes in the expression of genes related to digestion and metabolism from juvenile to adult in different dietary mammals, with giant and red pandas showing adaptations associated with specific nutritional limitations of bamboo.

Niche partitioning in a guild of invasive mammalian predators

Predators compete aggressively for resources, establishing trophic hierarchies that influence ecosystem structure. Competitive interactions are particularly important in invaded ecosystems where introduced predators can suppress native prey species. We investigated whether niche partitioning exists within a guild of invasive mammalian predators and determined the consequences for native species. Over 4405 camera-trap days, we assessed interactions among three invasive predators: two apex predators (feral cats Felis catus and ferrets Mustela furo) and a mesopredator (stoats Mustela erminea), in relation to their primary prey (lagomorphs, rodents and birds) and habitat use. Further, we tested for mesopredator release by selectively removing cats and ferrets in a pulse perturbation experiment. We found compelling evidence of niche partitioning; spatiotemporal activity of apex predators maximized access to abundant invasive prey, with ferrets targeting lagomorphs and cats targeting rodents. Mesopredators adjusted their behavior to reduce the risk of interference competition, thereby restricting access to abundant prey but increasing predation pressure on diurnal native birds. Stoats were only recorded at the treatment site after both larger predators were removed, becoming the most frequently detected predator at 6 months post-perturbation. We suggest there is spatial and resource partitioning within the invasive predator guild, but that this is incomplete, and avoidance is achieved by temporal partitioning within overlapping areas. Niche partitioning among invasive predators facilitates coexistence, but simultaneously intensifies predation pressure on vulnerable native species.

Uncovering Forensic Taphonomic Agents: Animal Scavenging in the European Context

Simple Summary

In forensic cases of exposed human bodies, vertebrate animals frequently pose challenges concerning remains recovery, identification, and the interpretation of circumstances of death. For instance, they can remove body parts, destroy skeletal features, and create “pseudo-lesions” that complicate trauma analysis. With this review, we highlight vertebrate scavengers in Europe that are of forensic relevance, including their typical behaviour and their inflicted lesions on bones and soft tissues. Here, we support forensic practitioners in recognising animal activity at the site of discovery and in interpreting the circumstances of death. Our review serves as a guide for the examination of animal-altered human remains and their found state by providing ecological backgrounds on various vertebrate species. In addition, this study provides an overview of the current state of research in the field of animal scavenging in forensics.

Abstract

Animal scavenging by vertebrates can significantly alter human bodies and their deposition site. For instance, vertebrate animals can cause postmortem modification to a body, alter perimortem trauma, influence decomposition rates, disarticulate and scatter body parts or evidence, and affect the identification of the deceased. Animal scavenging is a relatively common occurrence in forensic investigations. Even so, studies on the subject are scattered and rare, with most focussing on geographical areas outside of Europe. For that reason, we intend to collate the literature to provide an account of forensically relevant vertebrate scavengers in Europe, their impacts on human remains, and their implications for forensic investigations. Here, we provide an overview of forensic aspects where the knowledge of animal scavenging is crucial, as well as an account of potential scavengers of human remains in Europe and their typical alterations to soft tissue and, in particular, to bones. In addition, we are the first to provide a guide for forensic practitioners to identify the presence of vertebrate scavenging and subsequently inform outdoor search strategies for affected human remains.

The host-specific resistome in environmental feces of Eurasian otters (Lutra lutra) and leopard cats (Prionailurus bengalensis) revealed by metagenomic sequencing

Investigation of feces of wildlife, which is considered as reservoirs, melting pots, vectors and secondary sources of antimicrobial resistance genes (ARGs), provides insights into the risks and ecology of ARGs in the environment. Here, we investigated microbiomes, virulence factor genes (VFGs) of bacterial pathogens, and resistomes in environmental feces of Eurasian otters (Lutra lutra) and leopard cats (Prionailurus bengalensis) using shotgun metagenome sequencing. As expected, the taxonomic compositions of bacteria were significantly different between the animals. Importantly, we found that the compositions of ARGs were also significantly different between the animals. We detected ARGs including iri, tetA(P), tetB(P), floR, sulII, strA, strB, tetW and tetY. Some of them were significantly more abundant in either of the host animals, such as strA, strB and tetY in Eurasian otters, and tetA(P), tetW and iri in leopard cats. We also found that some ARGs were selectively correlated to particular VFGs-related bacteria, such as tetA(P) and tetB(P) to Clostridium, and iri to Mycobacterium. We also found that there were positive correlations between Acinetobacter and ARGs of multiple antimicrobial classes. The host-specific resistomes and VFGs-related bacteria may be due to differences in the host's gut microbiome, diet and/or habitat, but further investigation is needed. Overall, this study provided important baseline information about the resistomes of the wildlife in Korea, which may help the conservation of these endangered species and assessment of human health risks posed by ARGs and bacterial pathogens from wildlife.

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Fecal ARGs and VFGs were investigated in wild Eurasian otters and leopard cats.

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The ARGs and VFGs were widespread in both the host animals.

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Certain ARGs and VFGs were differentially more abundant in either of the hosts.

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Multiple ARGs showed positive correlations with Acinetobacter VFGs.

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Consistent monitoring of ARGs in wildlife is needed from a One Health perspective.

Factors influencing scavenger guilds and scavenging efficiency in Southwestern Montana

Scavenging of carrion shapes ecological landscapes by influencing scavenger population demography, increasing inter- and intra-specific interactions, and generating ecosystem services such as nutrient cycling and disease moderation. Previous research found the cues promoting, or the constraints limiting, an individual's propensity or ability to scavenge vary widely, depending on anthropogenic and environmental factors. Here we investigated differences in scavenging patterns in a complex scavenger guild in Southwestern Montana. We used camera traps established at 13 carcass sites to monitor carcass detection, visitation, and consumption times, during 2016-2018 and generalized linear models to explore the influence of carcass characteristics, habitat features, and seasonality, on carcass selection and scavenging efficiency. We found that scavenger species diversity was higher at higher elevations and in grassland habitats. Scavenging efficiency was influenced inter alia by seasonality, distance to water, and elevation. We found that most carcass consumption was via facultative scavengers (bears, wolves, magpies, Corvus spp.) rather than turkey vultures, the only obligate scavengers in the study area. However, growing populations of turkey vultures may lead to increased competition with facultative scavengers over carrion, and could have cascading effects on food webs in this ecosystem.

Temporal variations in patterns of Escherichia coli strain diversity and antimicrobial resistance in the migrant Egyptian vulture

Aims: Multiple antimicrobial resistance in Escherichia coli of wild vertebrates is a global concern with scarce assessments on the subject from developing countries that have high human-wild species interactions. We studied the ecology of E. coli in a wintering population of Egyptian Vultures in India to understand temporal changes in both E. coli strains and patterns of antimicrobial resistance. Methods and Results: We ribotyped E. coli strains and assessed antimicrobial resistance from wintering vultures at a highly synanthropic carcass dump in north-west India. Both E. coli occurence (90.32%) and resistance to multiple antimicrobials (71.43%) were very high. Clear temporal patterns were apparent. Diversity of strains changed and homogenized at the end of the Vultures' wintering period, while the resistance pattern showed significantly difference inter-annually, as well as between arrival and departing individuals within a wintering cycle. Significance of study: The carcass dump environment altered both E. coli strains and multiple antimicrobial resistance in migratory Egyptian Vultures within a season. Long-distance migratory species could therefore disseminate resistant E. coli strains across broad geographical scales rendering regional mitigation strategies to control multiple antimicrobial resistance in bacteria ineffective.

Consumption of Big Game Remains by Scavengers: A Potential Risk as Regards Disease Transmission in Central Spain

Understanding the role that facultative scavenger species may play in spreading infectious pathogens, and even becoming reservoirs for humans, domestic and wild ungulates or, on the contrary, preventing the spread of disease, requires a prior understanding of the pattern of carrion scavenging in specific scenarios. The objectives of this paper are (i) to describe the guild of vertebrate scavengers and (ii) to study the species-specific, habitat, and management-related factors involved in the usage of gut piles in South Central Spain (SCS), a tuberculosis (TB) endemic area. We used camera trapping at 18 hunting piles on seven hunting estates. A total of eight bird and five mammal taxa were detected at the remains of hunting piles. The most frequently detected species in terms of number of gut piles visited (78%) and scavenged (61%) was the red fox Vulpes vulpes, followed by the griffon vulture Gyps fulvus (56% as regards both presence and scavenging) and the raven Corvus corax (61 and 39% as regards presence and scavenging, respectively). We evidenced that griffon vultures accounted for most of the scavenging activity in open habitats, while facultative mammal scavengers, red fox, and wild boar Sus scrofa made the highest contribution to scavenging in vegetation-covered habitats. In the case of wild boar, the gut piles deposited during the evening and night favored higher rates of scavenging, while the opposite pattern was observed for griffons. Overall, our findings suggest that when disposing of hunting remains in areas of risk as regards disease transmission it is particularly important to consider the access that facultative mammals, and especially wild boar, have to material, while the presence of the resource needs to be safeguarded to protect specialist scavengers of conservation value. These results are of particular relevance in the case of wild boar in the current context of re-emerging TB and emerging African swine fever (ASF) in Europe.

Ecological role of vertebrate scavengers in urban ecosystems in the UK

Recent research has demonstrated how scavenging, the act of consuming dead animals, plays a key role in ecosystem structure, functioning, and stability. A growing number of studies suggest that vertebrate scavengers also provide key ecosystem services, the benefits humans gain from the natural world, particularly in the removal of carcasses from the environment. An increasing proportion of the human population is now residing in cities and towns, many of which, despite being highly altered environments, contain significant wildlife populations, and so animal carcasses. Indeed, non-predation fatalities may be higher within urban than natural environments. Despite this, the fate of carcasses in urban environments and the role vertebrate scavengers play in their removal have not been determined. In this study, we quantify the role of vertebrate scavengers in urban environments in three towns in the UK. Using experimentally deployed rat carcasses and rapid fire motion-triggered cameras, we determined which species were scavenging and how removal of carcass biomass was partitioned between them. Of the 63 experimental carcasses deployed, vertebrate scavenger activity was detected at 67%. There was a significantly greater depletion in carcass biomass in the presence (mean loss of 194 g) than absence (mean loss of 14 g) of scavengers. Scavenger activity was restricted to three species, Carrion crows Corvus corone, Eurasian magpies Pica pica, and European red foxes Vulpes vulpes. From behavioral analysis, we estimated that a maximum of 73% of the carcass biomass was removed by vertebrate scavengers. Despite having low species richness, the urban scavenger community in our urban study system removed a similar proportion of carcasses to those reported in more pristine environments. Vertebrate scavengers are providing a key urban ecosystem service in terms of carcass removal. This service is, however, often overlooked, and the species that provide it are among some of the most disliked and persecuted.

Epidemiology and control of Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula), the primary wildlife host of bovine tuberculosis in New Zealand

The introduced Australian brushtail possum (Trichosurus vulpecula) is a maintenance host for bovine tuberculosis (TB) in New Zealand and plays a central role in the TB problem in this country. The TB-possum problem emerged in the late 1960s, and intensive lethal control of possums is now used to reduce densities to low levels over 8 million ha of the country. This review summarises what is currently known about the pathogenesis and epidemiology of TB in possums, and how the disease responds to possum control. TB in possums is a highly lethal disease, with most possums likely to die within 6 months of becoming infected. The mechanisms of transmission between possums remain unclear, but appear to require some form of close contact or proximity. At large geographic scales, TB prevalence in possum populations is usually low (1-5%), but local prevalence can sometimes reach 60%. Intensive, systematic and uniform population control has been highly effective in breaking the TB cycle in possum populations, and where that control has been sustained for many years the prevalence of TB is now zero or near zero. Although some uncertainties remain, local eradication of TB from possums appears to be straightforward, given that TB managers now have the ability to reduce possum numbers to near zero levels and to maintain them at those levels for extended periods where required. We conclude that, although far from complete, the current understanding of TB-possum epidemiology, and the current management strategies and tactics, are sufficient to achieve local, regional, and even national disease eradication from possums in New Zealand.

Toward eradication: the effect of Mycobacterium bovis infection in wildlife on the evolution and future direction of bovine tuberculosis management in New Zealand

New Zealand's bovine tuberculosis (TB) control programme has greatly reduced the burden of tuberculosis on the farming industry, from 11% of mature cattle found with TB at slaughter in 1905 to <0.003% in 2012/13. New Zealand implemented TB control measures in cattle from the mid-twentieth century, and later in farmed deer. Control was based on established methods of tuberculin testing of herds, slaughter of suspect cases, and livestock movement control. Unexplained regional control failures and serious disease outbreaks were eventually linked to wildlife-vectored infection from the introduced Australian brushtail possum (Trichosurus vulpecula), which also triggered a wildlife disease complex involving a range of introduced species. This paper reviews the progressive elucidation of the epidemiology of Mycobacterium bovis in New Zealand's wildlife and farmed livestock, and the parallel development of research-led, multi-faceted TB control strategies required to protect New Zealand's livestock industries from damaging infection levels. The adoption of coordinated national pest management strategies, with increasingly ambitious objectives agreed between government and industry funders, has driven a costly but very successful management regime targeted at controlling TB in the possum maintenance host. This success has led to initiation of a strategy designed to eradicate TB from New Zealand's livestock and wildlife, which is considered a realistic long-term prospect.

The role of multiple wildlife hosts in the persistence and spread of bovine tuberculosis in New Zealand

AIM

To explore how the inclusion of multi-host dynamics affects the predicted prevalence of bovine tuberculosis (TB) in possums and other host species following the current best practice for control of TB in large difficult and remote areas, to identify which host species are responsible for changes in predicted prevalence, and whether TB can persist in possum-free host communities.

METHODS

Multi-host TB models were constructed, comprising three host species with density-dependent population growth, density-dependent disease transmission and susceptible and infected classes. Models were parameterised for two case studies of current concern in New Zealand, namely chronic TB persistence in a possum-deer-pig complex in extensive forest, and in a possum-pig-ferret complex in unforested semi-arid shrub and grasslands. Persistence of TB in the face of best practice possum control was evaluated from model simulations, and the contribution of different hosts to persistence of TB was assessed by removing each host species in turn from the simulations. A sensitivity test explored how different parameter values affected modelled persistence of TB.

RESULTS

The forest multi-host model-predicted amplification of TB prevalence due to the presence of pigs. The presence of pigs and/or deer did not jeopardise the success of best practice possum control in eradicating TB from the system, as pigs and deer are effectively end-hosts for TB. Sensitivity analyses indicated these interpretations were robust to uncertainty in model parameter values. The grassland system model predicted that the multi-host species complex could potentially lead to failure of eradication of TB under possum-only control, due to TB persisting in ferret and pig populations in the absence of possum hosts through reciprocal scavenging, resulting in spillback transmission to possums once their populations had started to recover from control.

CONCLUSIONS

With respect to management of TB, for modelled forest habitats, 15 years of effective possum control was predicted to eradicate TB from the possum-deer-pig host community, indicating the current focus on possum-only control is appropriate for such areas. For grassland model systems, TB was predicted to persist in the ferret-pig host complex in the absence of possums, potentially jeopardising the effectiveness of possum-only control programmes. However this outcome depended on the occurrence and rate of pigs acquiring TB from ferrets, which is unknown. Thus some estimation of this transmission parameter is required to enable managers to assess if multi-host disease dynamics are important for their TB control programmes.

The epidemiology of Mycobacterium bovis in wild deer and feral pigs and their roles in the establishment and spread of bovine tuberculosis in New Zealand wildlife

In New Zealand, wild deer and feral pigs are assumed to be spillover hosts for Mycobacterium bovis, and so are not targeted in efforts aimed at locally eradicating bovine tuberculosis (TB) from possums (Trichosurus vulpecula), the main wildlife host. Here we review the epidemiology of TB in deer and pigs, and assess whether New Zealand's TB management programme could be undermined if these species sometimes achieve maintenance host status. In New Zealand, TB prevalences of up to 47% have been recorded in wild deer sympatric with tuberculous possums. Patterns of lesion distribution, age-specific prevalences and behavioural observations suggest that deer become infected mainly through exposure to dead or moribund possums. TB can progress rapidly in some deer (<10%), but generalised disease is uncommon in wild deer; conversely some infected animals can survive for many years. Deer-to-deer transmission of M. bovis is rare, but transmission from tuberculous deer carcasses to scavengers, including possums, is likely. That creates a small spillback risk that could persist for a decade after transmission of new infection to wild deer has been halted. Tuberculosis prevalence in New Zealand feral pigs can reach 100%. Infections in lymph nodes of the head and alimentary tract predominate, indicating that TB is mostly acquired through scavenging tuberculous carrion, particularly possums. Infection is usually well contained, and transmission between pigs is rare. Large reductions in local possum density result in gradual declines (over 10 years) in TB prevalence among sympatric wild deer, and faster declines in feral pigs. Elimination of TB from possums (and livestock) therefore results in eventual disappearance of TB from feral pigs and wild deer. However, the risk of spillback infection from deer to possums substantially extends the time needed to locally eradicate TB from all wildlife (compared to that which would be required to eradicate disease from possums alone), while dispersal or translocation of pigs (e.g. by hunters) creates a risk of long-distance spread of disease. The high rate at which pigs acquire M. bovis infection from dead possums makes them useful as sentinels for detecting TB in wildlife. It is unlikely that wild deer and feral pigs act as maintenance hosts anywhere in New Zealand, because unrestricted year-round hunting keeps densities low, with far less aggregation than on New Zealand farms. We conclude that active management of wild deer or feral pigs is not required for local TB eradication in New Zealand.

Development of integrated surveillance systems for the management of tuberculosis in New Zealand wildlife

Disease surveillance for the management of bovine tuberculosis (TB) in New Zealand has focussed, to a large extent, on the development of tools specific for monitoring Mycobacterium bovis infection in wildlife. Diagnostic techniques have been modified progressively over 30 years of surveillance of TB in wildlife, from initial characterisation of gross TB lesions in a variety of wildlife, through development of sensitive culture techniques to identify viable mycobacteria, to molecular identification of individual M. bovis strains. Of key importance in disease surveillance has been the elucidation of the roles that different wildlife species play in the transmission of infection, specifically defining brushtail possums (Trichosurus vulpecula) as true maintenance hosts compared to those that are predominantly spillover hosts, but which may serve as useful sentinel species to indicate TB persistence. Epidemiological modelling has played a major role in TB surveillance, initially providing the theoretical support for large-scale possum population control and setting targets at which control effort should be deployed to ensure disease eradication. As TB prevalence in livestock and wildlife declined throughout the 2000s, more varied field tools were developed to gather surveillance data from the diminishing possum populations, and to provide information on changing TB prevalence. Accordingly, ever more precise (but disparate) surveillance information began to be integrated into multi-faceted decision-assist models to support TB management decisions, particularly to provide informed parameters at which control effort could be halted, culminating in the Proof of Freedom modelling framework that now allows an area to be declared TB-free within chosen confidence limits. As New Zealand moves from large-scale TB control to regional eradication of disease in the coming years, further integrative models will need to be developed to support management decisions, based on combined field data of possum and TB prevalence, sentinel information, risk assessment in relation to financial benefits, and changing political and environmental needs.

Feral ferrets (Mustela furo) as hosts and sentinels of tuberculosis in New Zealand

The control and eventual eradication of bovine tuberculosis (TB) poses major challenges in New Zealand, given the variety of wildlife species susceptible to TB, many of which are capable of onwards transmission of Mycobacterium bovis infection. Here we discuss the role of feral ferrets (Mustela furo), focussing on potential transmission or risk pathways that have implications for management of TB. Firstly inter-specific transmission to ferrets. Ferrets scavenge potentially infected wildlife, including other ferrets, thus prevalence of TB can be amplified through ferrets feeding on tuberculous carcasses, particularly brushtail possums (Trichosurus vulpecula). Secondly intra-specific transmission between ferrets. The rate of ferret-ferret transmission depends on population density, and in some places ferret densities exceed the estimated threshold for disease persistence. TB can therefore potentially be maintained independently of other sources of infection. Thirdly transmission from ferrets to other wildlife. These include the main wildlife maintenance host, brushtail possums, that will occasionally scavenge potentially tuberculous ferret carcasses. Fourthly transmission from ferrets to livestock. This is considered to occur occasionally, but the actual rate of transmission has never been measured. Fifthly geographical spread. M. bovis-infected ferrets can travel large distances and cause new outbreaks of TB at locations previously free of TB, which may have caused an expansion of TB-endemic areas.Ferrets play a complex role in the TB cycle in New Zealand; they are capable of contracting, amplifying and transmitting M. bovis infection, sometimes resulting in ferret populations with a high prevalence of TB. However, ferret population densities are usually too low to sustain infection independently, and transmission to other wildlife or livestock appears a rarer event than with possums. Nevertheless, management of ferrets remains a key part of the National Pest Management Strategy for TB. Control is prudent where M. bovis-infected ferret populations exist in high numbers, to reduce the onward transmission risk of any self-sustained infection to livestock. When ferret numbers are well below the theoretical disease maintenance threshold, ferret control is still sometimes warranted because of the animals’ ability to acquire infection when young and, through dispersal, transport it outside TB-endemic areas. Ferrets can also be used as disease sentinels for TB, especially in areas where alternative sentinel species are rare or expensive to survey, and when sampling of possums is not cost-effective.

Managing and eradicating wildlife tuberculosis in New Zealand

Tuberculosis (TB) due to Mycobacterium bovis infection was first identified in brushtail possums (Trichosurus vulpecula) in New Zealand in the late 1960s. Since the early 1970s, possums in New Zealand have been controlled as part of an ongoing strategy to manage the disease in livestock. The TB management authority (TBfree New Zealand) currently implements three strategic choices for disease-related possum control: firstly TB eradication in areas selected for eradication of the disease from livestock and wildlife, secondly Free Area Protection in areas in which possums are maintained at low densities, normally along a Vector Risk Area (VRA) boundary, and thirdly Infected Herd Suppression, which includes the remaining parts of VRA where possums are targeted to minimise the infection risk to livestock. Management is primarily through a range of lethal control options. The frequency and intensity of control is driven by a requirement to reduce populations to very low levels (usually to a trap-catch index below 2%), then to hold them at or below this level for 5–10 years to ensure disease eradication.Lethal possum control is implemented using aerial- and ground-based applications, under various regulatory and operational constraints. Extensive research has been undertaken aimed at improving the efficacy and efficiency of control. Aerial applications use sodium fluoroacetate (1080) bait for controlling possums over extensive and rugged areas of forest that are difficult to access by foot. Ground-based control uses a range of toxins (primarily, a potassium cyanide-based product) and traps. In the last 5 years there has been a shift from simple possum population control to the collection of spatial data on possum presence/absence and relative density, using simple possum detection devices using global positioning system-supported data collection tools, with recovery of possum carcasses for diagnostic necropsy. Such data provide information subsequently used in predictive epidemiological models to generate a probability of TB freedom.The strategies for managing TB in New Zealand wildlife now operate on four major principles: firstly a target threshold for possum population reduction is defined and set, secondly an objective methodology is applied for assessing whether target reductions have been achieved, thirdly effective control tools for achieving possum population reductions are used, and fourthly the necessary legislative support is in place to ensure compliance. TBfree New Zealand's possum control programme meets these requirements, providing an excellent example of an effective pest and disease control programme.

Importance and mitigation of the risk of spillback transmission of Mycobacterium bovis infection for eradication of bovine tuberculosis from wildlife in New Zealand

Introduced brushtail possums (Trichosurus vulpecula) are wildlife maintenance hosts for Mycobacterium bovis in New Zealand, often living sympatrically with other potential hosts, including wild red deer (Cervus elaphus scoticus). Population control of possums has been predicted to eradicate tuberculosis (TB) from New Zealand wildlife; however, there is concern that long-lived M. bovis-infected deer could represent a ‘spillback’ risk for TB re-establishment (particularly when possum populations recover after cessation of intensive control). We constructed a time-, age- and sex-structured, deer/TB population generic model and simulated the outcomes of deer control on this potential spillback risk. Maintaining intensive possum control on a 5-year cycle, the predicted spillback risk period after TB eradication from possums is ∼7 years, while the probability of TB re-establishing in possums over that period is ∼6%. Additional targeted control of deer would reduce the risk period and probability of spillback; however, even with high population reductions (up to 80%) only modest decreases in risk and risk period would be achieved. We conclude that possum control alone remains the best strategy for achieving TB eradication from New Zealand habitats in which possums and wild deer are the main M. bovis hosts.

Effects of vulture declines on facultative scavengers and potential implications for mammalian disease transmission

Vultures (Accipitridae and Cathartidae) are the only known obligate scavengers. They feed on rotting carcasses and are the most threatened avian functional group in the world. Possible effects of vulture declines include longer persistence of carcasses and increasing abundance of and contact between facultative scavengers at these carcasses. These changes could increase rates of transmission of infectious diseases, with carcasses serving as hubs of infection. To evaluate these possibilities, we conducted a series of observations and experimental tests of the effects of vulture extirpation on decomposition rates of livestock carcasses and mammalian scavengers in Kenya. We examined whether the absence of vultures changed carcass decomposition time, number of mammalian scavengers visiting carcasses, time spent by mammals at carcasses, and potential for disease transmission at carcasses (measured by changes in intraspecific contact rates). In the absence of vultures, mean carcass decomposition rates nearly tripled. Furthermore, the mean number of mammals at carcasses increased 3-fold (from 1.5 to 4.4 individuals/carcass), and the average time spent by mammals at carcasses increased almost 3-fold (from 55 min to 143 min). There was a nearly 3-fold increase in the mean number of contacts between mammalian scavengers at carcasses without vultures. These results highlight the role of vultures in carcass decomposition and level of contact among mammalian scavengers. In combination, our findings lead us to hypothesize that changes in vulture abundance may affect patterns of disease transmission among mammalian carnivores.

Mycobacterial infection in the ferret

Mycobacteriosis is an important disease in the feral ferret (Mustela putorius furo) of New Zealand; elsewhere, reports of tuberculosis in the ferret are sporadic. Genus Mycobacterium consists of aerobic, non-spore-forming, gram-positive, nonmotile bacteria that characteristically feature a cell wall rich in mycolic acids and esters. The epidemiology of mycobacteriosis in the ferrets of New Zealand involves complex interactions between ferrets, possums, and livestock. Investigators have shown that the ferret is highly susceptible only to Mycobacterium bovis infection and is more resistant to infection by other Mycobacterium spp. The principal site of all mycobacterial infection in the ferret is the gastrointestinal tract.

Hedgehogs and sugar gliders: respiratory anatomy, physiology, and disease

This article discusses the respiratory anatomy, physiology, and disease of African pygmy hedgehogs (Atelerix albiventris) and sugar gliders (Petaurus breviceps), two species commonly seen in exotic animal practice. Where appropriate, information from closely related species is mentioned because cross-susceptibility is likely and because these additional species may also be encountered in practice. Other body systems and processes are discussed insofar as they relate to or affect respiratory function. Although some topics, such as special senses, hibernation, or vocalization, may seem out of place, in each case the information relates back to respiration in some important way.

Maintenance, spillover and spillback transmission of bovine tuberculosis in multi-host wildlife complexes: a New Zealand case study

The causative agent of bovine tuberculosis (bTB; Mycobacterium bovis) has a broad host range. The role of each animal species in spreading the disease depends on how transmission occurs, on the abundance of each host, and on the interactions between hosts. This paper explores differences in the roles individual host species can play in allowing M. bovis infection to persist and spread within a multi-species complex, using New Zealand as a case study. In New Zealand, four wild mammal species are frequently infected. Of these the brushtail possum is now regarded as the only true "maintenance" host. Red deer and ferrets can become maintenance hosts where their densities are exceptionally high, but more often they are "spillover" hosts, with most infection arising from moderately frequent inter-species transmission from possums. The latter situation is even more strongly the case for feral pigs. Spillover hosts may occasionally play a crucial epidemiological role by transmitting infection back to a potential maintenance host (spillback). Three key factors make spillback transmission far more epidemiologically important than its low frequency of occurrence might suggest--amplification of the reservoir of bTB, far greater spatial spread than by the maintenance host, and greater persistence of bTB in long-lived spillover hosts extending the risk of spillback far into the future. The risk of spillback is undoubtedly low, but it nonetheless determines the nature, scale and duration of management required. Eradication of the disease may require management of both the infection in maintenance hosts and reduction or elimination of any risk of spillback.

Comparison of Three Immunodiagnostic Assays for Antemortem Detection of Mycobacterium Bovis Stimulation in Domestic Cats

Mycobacterium bovis causes disease in numerous mammalian species including humans, thus making research, surveillance, and control important in the eradication of tuberculosis. Domestic cats are susceptible to multiple mycobacterial species including Mycobacterium bovis; however, their role in the epidemiology of bovine tuberculosis is not fully documented. The current study was an evaluation of the immune response in specific pathogen–free (SPF) cats stimulated with sensitinogen, a heat-killed M. bovis product, using the rapid test, multiple antigen print immunoassay (MAPIA), and bovine-purified protein derivative (bPPD) single skin test. Six cats were inoculated with sensitinogen subcutaneously on days 0 and 24; 2 noninoculated cats and 49 non-SPF cats were controls. Serial serum samples were collected during 135 days and assayed for M. bovis antibodies by rapid test and MAPIA. On day 123, bPPD skin test was performed and read at 48 and 72 hr. The bPPD test at 72 hr had a mean skin thickness of 0.3 mm for stimulated cats and 0.1 mm for controls. Rapid test identified 4 of 6 stimulated cats after bPPD injection. The MAPIA detected antibody against MPB83, 16/83, 16 kDa, and M. bovis culture filtrate (MBCF) antigens. All assays differentiated between stimulated and control cats; however, 7 of 49 non-SPF control cats had a reaction for either antigen MBCF or 16/83. These preliminary studies show potential for antemortem detection of M. bovis among domestic cats. Additional studies to better characterize virulent M. bovis infection in cats would be of value.

Rate of removal of bird carcasses in arable farmland by predators and scavengers

Studies requiring carcasses to be retrieved to detect mortality and its causes in wildlife can be difficult to interpret due to removal of carcasses by scavengers. This paper describes two linked studies measuring rate of removal of carcasses from farmland in the UK, carried out to inform the results of a pesticide study involving carcass searching. In winter, 6% of carcasses had been removed 24 h after placement, and 32% had been removed 96 h after placement; wild bird carcasses were removed significantly faster than those of artificially reared birds. In summer, 76% of carcasses had been removed 24 h after placement and 91% after 96 h. A literature review of similar studies is given. Carcass removal rates by predators and scavengers appear to vary widely between sites and seasons, and may be high. If the results of studies involving carcass searches or surveillance are to be interpreted correctly, carcass removal rate by scavengers should be measured under similar conditions to, and contemporaneous with, those under which mortality is expected to occur.

Adaptation of IFN-gamma ELISA and ELISPOT tests for feline tuberculosis

There are currently no reliable immunodiagnostic tests for feline tuberculosis. Infection of domestic cats in the UK is thought to occur via their contact with the relevant reservoir of infection, e.g. cattle and badgers for Mycobacterium bovis, and rodents for M. microti. In the African National Parks, where M. bovis infection of Bovidae is an increasing problem, transmission to big cats is occurring via their ingestion of infected carcasses. We have adapted feline ELISA and ELISPOT assays to potentially provide the first cell-based diagnostic test for the detection of tuberculosis in cats. We tested peripheral blood mononuclear cell antigen-specific IFN-gamma responses of 18 cats suspected of mycobacterial infection for which biopsy material was co-submitted to the Veterinary Laboratories Agency for mycobacterial culture and identification. Seventeen cats were tested by ELISA while seven cats were tested by ELISPOT (six cats were tested by both ELISA and ELISPOT). Six healthy control cats provided baseline data for these tests. Responses to bovine and avian tuberculins (PPDB and PPDA) and a protein cocktail of ESAT6 and CFP10 were measured, together with positive mitogen (PMA and calcium ionophore) and negative (medium) controls. Overall, both ELISPOT and ELISA tests were found to be suitable for generating rapid results (2 and 4 days, respectively), which provided good predictive information for M. bovis and M. microti infections, but were unable to reliably discern M. avium infection.

Risk factors associated with the prevalence of tuberculosis-like lesions in fenced wild boar and red deer in south central Spain

In recent decades the management of large game mammals has become increasingly intensive in south central Spain (SCS), resulting in complex epidemiological scenarios for disease maintenance, and has probably impeded schemes to eradicate tuberculosis (TB) in domestic livestock. We conducted an analysis of risk factors which investigated associations between the pattern of tuberculosis-like lesions (TBL) in wild boar (Sus scrofa) and red deer (Cervus elaphus) across 19 hunting estates from SCS and an extensive set of variables related to game management, land use and habitat structure. The aggregation of wild boar at artificial watering sites was significantly associated with an increasing risk of detecting TBL in both species, which probably relates to enhanced opportunities for transmission. Aggregation of wild boar at feeding sites was also associated with increased risks of TBL in red deer. Hardwood Quercus spp. forest availability was marginally associated with an increased risk of TB in both species, whereas scrubland cover was associated with a reduced individual risk of TBL in the wild boar. It is concluded that management practices that encourage the aggregation of hosts, and some characteristics of Mediterranean habitats could increase the frequency and probability of both direct and indirect transmission of TB. These findings are of concern for both veterinary and public health authorities, and reveal tuberculosis itself as a potential limiting factor for the development and sustainability of such intensive game management systems in Spanish Mediterranean habitats.

Factors affecting carcass use by a guild of scavengers in European temperate woodland

Although facultative scavenging is very common, little is known about the factors governing carrion acquisition by vertebrates. We examined the influence of carcass characteristics, carcass state, and weather conditions on carrion use by main scavengers. Carcasses (N = 214, mainly ungulates) of various origins (predation, natural deaths, harvest) were monitored by systematic inspections (N = 1784) in Białowieża Forest (Poland). Common raven (Corvus corax L., 1758), red fox (Vulpes vulpes (L., 1758)), and European pine marten (Martes martes (L., 1758)) mainly used the prey remains of gray wolves (Canis lupus L., 1758). The kills of predators were the preferred carrion, rather than dead ungulates. Common ravens, common buzzards (Buteo buteo (L., 1758)), white-tailed eagles (Haliaeetus albicilla (L., 1758)), and domestic dogs scavenged more frequently on carcasses in open habitats. Carcasses located in the forest were the most available to European pine martens, jays (Garrulus glandarius (L., 1758)), and wild boar (Sus scrofa L., 1758). The common tendency was to increase scavenging when temperature decreased, except for raccoon dogs (Nyctereutes procyonoides (Gray 1834)). As snow depth increased, jays and great tits (Parus major L., 1758) increased scavenging. We suggest that carrion use by scavengers is not random, but a complex process mediated by extrinsic factors and by behavioural adaptations of scavengers.

The relationship between prevalence of Mycobacterium bovis infection in feral ferrets and possum abundance

AIM

To determine the relationship between the prevalence of macroscopic Mycobacterium bovis infection in feral ferrets (Mustela furo) and the abundance of brushtail possums (Trichosurus vulpecula).

METHODS

The predictive power of a previously reported positive association between the prevalence of macroscopic M. bovis infection in ferrets and possum abundance was examined by undertaking surveys of M. bovis infection in ferrets at sites of low and high possum abundance. The association was then tested by a manipulative experiment that measured changes in the prevalence of macroscopic M. bovis infection in feral ferrets after reducing possum abundance.

RESULTS

The positive relationship between the prevalence of macroscopic M. bovis infection in ferrets and possum abundance remained valid for new survey data, although the goodness of fit of the relationship was reduced. Experimentally reducing possum abundance reduced the odds of macroscopic M. bovis infection in ferrets by 80% in the years immediately following possum control (Odds Ratio=0.23, p=0.003).

CONCLUSIONS

There is a causal link between possum abundance and the prevalence of macroscopic M. bovis infection in feral ferrets in areas in which M. bovis infection is known to occur in ferret populations. This suggests that possum-to-ferret transmission of disease occurs and accounts for most of the disease evident in ferret populations, though does not determine whether ferrets are spillover or maintenance hosts of M. bovis. Management to reduce the prevalence of M. bovis infection in ferrets should consider reducing possum abundance as a control tactic.

Surveillance of wildlife forMycobacterium bovisinfection using culture of pooled tissue samples from ferrets (Mustela furo)

AIM

To compare culture results of homogenates of pooled lymph nodes from individual ferrets with and without macroscopic lesions of bovine tuberculosis for the presence of Mycobacterium bovis, and to determine whether homogenates from 10-30 ferrets could be combined and cultured without loss of sensitivity as a possible method for improving cost-effectiveness of surveillance for M. bovis infection in wildlife populations.

METHODS

Numbers of colony forming units (cfu) of M. bovis present in cultures of homogenates of pooled lymph nodes from individual ferrets known to be infected and having no visible lesions (NVL) or macroscopic lesions consistent with bovine tuberculosis were determined. Prevalences of M. bovis infection in populations of ferrets in the Marlborough region of the South Island of New Zealand were determined by culturing homogenates of pooled lymph nodes from individual animals. Samples from homogenates from North Canterbury were combined to form pools representing 10, 20 and 30 animals and also cultured for M. bovis.

RESULTS

Fewer M. bovis cfu were isolated from ferrets with NVL (mean=0.77 log10) compared with ferrets with macroscopic lesions (mean=3.22 log10; p<0.05). The mean prevalence of infection in eight different surveys involving 427 ferrets from the Marlborough region was 18% (range 8-44%), which included a small number of animals with macroscopic lesions of tuberculosis. Pooling of samples from up to 30 different ferrets with NVL did not reduce the sensitivity of detecting M. bovis infected populations.

CONCLUSION

Culturing of pools of lymph node samples detected a significant proportion of M. bovis-infected ferrets that would otherwise have gone unnoticed based on samples that had only macroscopic lesions. Culturing of samples pooled from up to 30 different ferrets could provide significant cost savings in surveys of wildlife for the presence of M. bovis infection without any apparent loss of sensitivity.