Wildlife Disease Control Research Articles

Evolutional dynamics of highly pathogenic avian influenza H5N8 genotypes in wintering bird habitats: Insights from South Korea's 2020–2021 season

The winter of 2020–2021 in South Korea witnessed severe outbreaks of Highly Pathogenic Avian Influenza (HPAI) viruses, specifically multiple genotypes of the H5N8 subtype. These outbreaks prompted an extensive investigation into the genetic characteristics and evolutionary dynamics of these viruses. Under the auspices of the National Institute of Wildlife Disease Control and Prevention (NIWDC), we conducted a nationwide surveillance program, collecting 7588 specimens from diverse wild bird habitats. Influenza A viruses were isolated at a rate of 5.0%, with HPAI H5N8 viruses accounting for 38.5% of isolates, predominantly found in wild bird carcasses (97.3%). Genetic analysis revealed the emergence of novel HPAI genotypes due to genetic reassortment events. G1 and G2 viruses were separately introduced into Korea, with G1 viruses displaying dynamic behavior, resulting in diverse sub-genotypes (G1–1 to G1–5) and mainly isolated from clinical specimens. Conversely, the G2 virus, introduced later, became the dominant strain consistently isolated mainly from bird carcasses (88.9%). These findings underscore the emergence of numerous novel HPAI genotypes shaped by multiple reassortment events in high-density wintering grounds of migratory birds. These sites act as hotspots for genetic exchanges, significantly influencing avian ecology, including resident bird species, and contributing to HPAI H5N8 evolution. The genetic diversity and ongoing evolution of these viruses highlight the need for vigilant surveillance and adaptive control measures. Recognizing the potential spillover to human populations, a One Health approach is essential to mitigate the evolving threats posed by avian influenza.

Production Technologies, Regulatory Parameters, and Quality Control of Vaccine Vectors for Veterinary Use

This paper presents a comprehensive review of the main types of vaccines approaching production technology, regulatory parameters, and the quality control of vaccines. Bioinformatic tools and computational strategies have been used in the research and development of new pharmaceutical products, reducing the time between supposed pharmaceutical product candidates (R&D steps) and final products (to be marketed). In fact, in the reverse vaccinology field, in silico studies can be very useful in identifying possible vaccine targets from databases. In addition, in some cases (subunit or RNA/ DNA vaccines), the in silico approach permits: (I) the evaluation of protein immunogenicity through the prediction of epitopes, (II) the potential adverse effects of antigens through the projection of similarity to host proteins, (III) toxicity and (IV) allergenicity, contributing to obtaining safe, effective, stable, and economical vaccines for existing and emerging infectious pathogens. Additionally, the rapid growth of emerging infectious diseases in recent years should be considered a driving force for developing and implementing new vaccines and reassessing vaccine schedules in companion animals, food animals, and wildlife disease control. Comprehensive and well-planned vaccination schedules are effective strategies to prevent and treat infectious diseases.

Model Integrated Disease Management to facilitate effective translatable solutions for wildlife disease issues

Abstract There are multiple demands for the development of effective and sustainable disease management practices in wildlife, but solutions are widely lacking. In this perspective, we focus on the need to structure research to support advancement toward enhanced wildlife disease control solutions. We concentrate on the need for improved integration between wildlife disease management undertaken in situ with modelling to guide and assess disease management actions. We recognise that many disease management attempts in wildlife are made in isolation, are not supported by modelling and are not used as a stepping stone to advancement. However, we emphasise that the development of disease control practices in wildlife is greater than any one management attempt, and should be seen and undertaken as a set of systematic steps towards well‐articulated management goals. We describe modelling of disease management and in situ disease management as two complementary phases of investigation, viewed as a feedback loop to support advancements, and highlight established and less established pathways in this loop. We describe how stakeholders engaged in practical management actions can better engage with modellers, and also the need for more fit‐for‐purpose modelling that captures the on‐ground realities of in situ practice to support advancements. The concepts and approaches described in this perspective are captured within a Model Integrated Disease Management for wildlife framework. We illustrate the framework, concepts and challenges proposed in this perspective using a case study for which we have experience: sarcoptic mange (etiologic agent Sarcoptes scabiei) in bare‐nosed wombats (Vombatus ursinus). Synthesis and applications: Effective and sustainable solutions to critical wildlife diseases are needed. Progress can be improved when disease management is guided through iterative and fit‐for‐purpose integration between modelling and in situ practice. We describe and illustrate a Model Integrated Disease Management for wildlife framework. Moving beyond isolated disease management attempts into a structured process of advancement can help overcome barriers to tackling pathogens threatening wildlife.

Novel Vaccine Technologies in Veterinary Medicine: A Herald to Human Medicine Vaccines.

The success of inactivated and live-attenuated vaccines has enhanced livestock productivity, promoted food security, and attenuated the morbidity and mortality of several human, animal, and zoonotic diseases. However, these traditional vaccine technologies are not without fault. The efficacy of inactivated vaccines can be suboptimal with particular pathogens and safety concerns arise with live-attenuated vaccines. Additionally, the rate of emerging infectious diseases continues to increase and with that the need to quickly deploy new vaccines. Unfortunately, first generation vaccines are not conducive to such urgencies. Within the last three decades, veterinary medicine has spearheaded the advancement in novel vaccine development to circumvent several of the flaws associated with classical vaccines. These third generation vaccines, including DNA, RNA and recombinant viral-vector vaccines, induce both humoral and cellular immune response, are economically manufactured, safe to use, and can be utilized to differentiate infected from vaccinated animals. The present article offers a review of commercially available novel vaccine technologies currently utilized in companion animal, food animal, and wildlife disease control.

A PIT‐tag–based method for measuring individual bait uptake in small mammals

Abstract Rodents and other small mammals cause an increasing number of negative economic and environmental impacts worldwide. In the UK, the non‐native grey squirrel has a significant impact on the forestry industry and has caused the decline of the native red squirrel. Baits are used to deliver biocides and contraceptives to reduce overabundant wildlife populations and as vehicles for vaccines to control disease outbreaks. Bait‐delivered contraceptives are also being developed to manage grey squirrel populations in the UK. The effectiveness of bait‐delivered drugs on wildlife populations depends on the amount of bait consumed by individuals over time; therefore, it is important to understand individual level bait uptake in order to optimize delivery methods. Passive integrated transponder (PIT) tags are increasingly used to mark and monitor animal behaviour as they are cost‐effective, have minimal negative welfare impacts and have a lower tag loss rate than external tags, particularly in small animals. The aim of this study was to design and test a novel bait hopper equipped with a PIT‐tag reader and bait‐weighing device, to record bait uptake by individual grey squirrels for optimizing the delivery of a contraceptive bait. The hopper was designed to overcome some of the limitations of traditional PIT‐tag systems, by improving battery life and the quality and quantity of data collected in the field. In captive trials, the hopper proved to be highly effective at recording feeding visits by squirrels, as 95% of the visits could be attributed to a PIT‐tag record. The hoppers measured the amount of bait removed per feeding visit to an accuracy of 0.1 g, with 97% of the bait taken from six hoppers attributed to a PIT‐tag ID. In a field trial, the hoppers were effective at recording the feeding visits by grey squirrels in two woods, with 47 of the 51 PIT‐tagged grey squirrels entering the hoppers. The adaptability of the hopper design means that it has wider applications for wildlife management; in particular, efficacy studies for bait‐delivered substances in the context of wildlife disease control and/or population reduction.

Investigation of Brucella melitensis in Sable Antelope (Hippotragus niger) in South Africa.

In this study, Brucella melitensis infection in sable antelope (Hippotragus niger) was investigated on two wildlife ranches in South Africa over a 12-year period in order to determine the origin of the outbreaks and the role of livestock in maintaining the disease. Retrospective data were obtained from farm records and interviews as well as samples tested from different disease scenarios and clinical settings. On one ranch, 10 of 74 sable tested seropositive for B. melitensis in 2004 but were certified clear of infection after no further brucellosis cases were detected following repeated serological tests and culling over a five-year period. Recrudescence occurred in 2013 (7 of 187 brucellosis positives) and in 2014 (one positive), with persistent, latent infection being the most reasonable explanation. In a second case study, linked to the first one through a common vendor, 15 of 80 sable tested positive in 2016, some five years after the acquisition of the animals from a putative source. Brucella melitensis biovar 1 and/or 3 were isolated from each outbreak on both ranches. Both outbreaks resulted in substantial losses for the owners, arising from testing and culling and significant resource expenditure by the state. The study identified the diagnostic challenges for identifying and resolving disease outbreaks in wildlife, the persistence of B. melitensis in sable, the risks associated with animal movements, and the need for a wildlife-sensitive disease control scheme. Although the actual source of infection could not be identified, the investigation points away from local livestock as a source of ongoing infection while the persistent infection is consistent with the disease circulating within small, ranched populations and being spread through the keeping and trading of high-value animals. The implications of the study findings to disease control in wildlife are discussed.

Fencing for wildlife disease control

Abstract Fencing is a contentious issue due to its impact on conservation. The Danish government aims to establish a 70 km fence towards the border of Germany and the agricultural ministry of Bulgaria erected 133 km fences along the border with Romania to prevent the spread of African swine fever by wild boar. The Norwegian government recently erected 24 km of fencing as part of combating chronic wasting disease among reindeer. Europe therefore faces a new situation: fencing to limit emerging wildlife diseases. There is, however, surprisingly little scientific literature available on the efficacy of fencing for controlling wildlife disease. Fencing to combat disease include (a) “perimeter fencing” aiming for containment and reducing likelihood of geographic spread, and (b) “hot spot fencing” aiming to lower transmission rates within endemic disease areas. Critical limitations of perimeter fencing include: numerous practical and construction details, differences in animal behaviour relative to fences, animal contact along fences, placement relative to natural barriers, human infrastructure that disrupt continuous fencing, and mode of disease transmission including human‐aided disease spread. Hot spot fencing is a potentially important way of reducing transmission of diseases once endemic but materials and construction of fences need to be well thought through. A single fence breach does not have the same consequences as for perimeter fencing. Synthesis and applications. Fencing as a tactic to mitigate the spread of disease appears appealing to politicians, but implementation uncertainty is considerable. We fear efforts may be futile unless more attention is paid to both practical and biological detail. There is also an urgent need to build a more evidence‐based approach using experience from other sectors.

Experimental evidence of a pathogen invasion threshold.

Host density thresholds to pathogen invasion separate regions of parameter space corresponding to endemic and disease-free states. The host density threshold is a central concept in theoretical epidemiology and a common target of human and wildlife disease control programmes, but there is mixed evidence supporting the existence of thresholds, especially in wildlife populations or for pathogens with complex transmission modes (e.g. environmental transmission). Here, we demonstrate the existence of a host density threshold for an environmentally transmitted pathogen by combining an epidemiological model with a microcosm experiment. Experimental epidemics consisted of replicate populations of naive crustacean zooplankton (Daphnia dentifera) hosts across a range of host densities (20–640 hosts l−1) that were exposed to an environmentally transmitted fungal pathogen (Metschnikowia bicuspidata). Epidemiological model simulations, parametrized independently of the experiment, qualitatively predicted experimental pathogen invasion thresholds. Variability in parameter estimates did not strongly influence outcomes, though systematic changes to key parameters have the potential to shift pathogen invasion thresholds. In summary, we provide one of the first clear experimental demonstrations of pathogen invasion thresholds in a replicated experimental system, and provide evidence that such thresholds may be predictable using independently constructed epidemiological models.

Dynamic, spatial models of parasite transmission in wildlife: Their structure, applications and remaining challenges.

Individual differences in contact rate can arise from host, group and landscape heterogeneity and can result in different patterns of spatial spread for diseases in wildlife populations with concomitant implications for disease control in wildlife of conservation concern, livestock and humans. While dynamic disease models can provide a better understanding of the drivers of spatial spread, the effects of landscape heterogeneity have only been modelled in a few well-studied wildlife systems such as rabies and bovine tuberculosis. Such spatial models tend to be either purely theoretical with intrinsic limiting assumptions or individual-based models that are often highly species- and system-specific, limiting the breadth of their utility. Our goal was to review studies that have utilized dynamic, spatial models to answer questions about pathogen transmission in wildlife and identify key gaps in the literature. We begin by providing an overview of the main types of dynamic, spatial models (e.g., metapopulation, network, lattice, cellular automata, individual-based and continuous-space) and their relation to each other. We investigate different types of ecological questions that these models have been used to explore: pathogen invasion dynamics and range expansion, spatial heterogeneity and pathogen persistence, the implications of management and intervention strategies and the role of evolution in host-pathogen dynamics. We reviewed 168 studies that consider pathogen transmission in free-ranging wildlife and classify them by the model type employed, the focal host-pathogen system, and their overall research themes and motivation. We observed a significant focus on mammalian hosts, a few well-studied or purely theoretical pathogen systems, and a lack of studies occurring at the wildlife-public health or wildlife-livestock interfaces. Finally, we discuss challenges and future directions in the context of unprecedented human-mediated environmental change. Spatial models may provide new insights into understanding, for example, how global warming and habitat disturbance contribute to disease maintenance and emergence. Moving forward, better integration of dynamic, spatial disease models with approaches from movement ecology, landscape genetics/genomics and ecoimmunology may provide new avenues for investigation and aid in the control of zoonotic and emerging infectious diseases.

Using Off-the-Shelf Technologies to Mass Manufacture Oral Vaccine Baits for Wildlife.

Technology and infrastructure costs can limit access to oral vaccination tools for wildlife disease control. We describe vaccine bait mass manufacturing employing off-the-shelf technologies. Our approach has helped advance scaling-up of plague vaccination campaigns, but components of this production system could be translated into other wildlife vaccination applications.

Valuing conservation benefits of disease control in wildlife: A choice experiment approach to bovine tuberculosis management in New Zealand's native forests

We assess the non-monetary environmental benefits that accrue incidentally in New Zealand (NZ) from pest management conducted primarily to control an animal disease, bovine tuberculosis (TB). TB is an infectious disease that is one of the world's most serious animal health problems and, in many parts of the developing world, still a major mortality risk for humans. The incidence of TB in New Zealand (NZ) farmed livestock has been reduced progressively over the last 20 years, largely due to extensive and sustained population control of the main wildlife reservoir of disease, the introduced brushtail possum. Possums are also major pests that threaten indigenous forest biodiversity, and so extensive possum control for TB mitigation also incidental benefits conservation, but the extent and public value of this benefit has yet to be quantified. We conducted a choice experiment survey of the NZ public in an effort to value the native forest biodiversity benefits of TB-related possum control. We find strong public support for conservation outcomes consequent to TB-possum control in public native forests. The public place substantial value on the most observable biodiversity benefits of TB possum control, such as improved forest canopies and presence of native birds. The benefits, costs and values of TB-possum control are discussed in relation to the future directives of NZ's TB control programme, which is headed toward first regional and then national level disease eradication.

Harmonizing methods for wildlife abundance estimation and pathogen detection in Europe-a questionnaire survey on three selected host-pathogen combinations.

BackgroundThe need for wildlife health surveillance as part of disease control in wildlife, domestic animals and humans on the global level is widely recognized. However, the objectives, methods and intensity of existing wildlife health surveillance programs vary greatly among European countries, resulting in a patchwork of data that are difficult to merge and compare. This survey aimed at evaluating the need and potential for data harmonization in wildlife health in Europe. The specific objective was to collect information on methods currently used to estimate host abundance and pathogen prevalence. Questionnaires were designed to gather detailed information for three host-pathogen combinations: (1) wild boar and Aujeszky’s disease virus, (2) red fox and Echinococcus multilocularis, and (3) common vole and Francisella tularensis.ResultsWe received a total of 70 responses from 19 European countries. Regarding host abundance, hunting bags are currently the most widely accessible data source for widely distributed mid-sized and larger mammals such as red fox and wild boar, but we observed large differences in hunting strategies among countries as well as among different regions within countries. For small rodents, trapping is the method of choice, but practical applications vary among study sites. Laboratory procedures are already largely harmonized but information on the sampled animals is not systematically collected.ConclusionsThe answers revealed that a large amount of information is available for the selected host-pathogen pairs and that in theory methods are already largely harmonized. However, the comparability of the data remains strongly compromised by local differences in the way, the methods are applied in practice. While these issues may easily be overcome for prevalence estimation, there is an urgent need to develop tools for the routine collection of host abundance data in a harmonized way. Wildlife health experts are encouraged to apply the harmonized APHAEA protocols in epidemiological studies in wildlife and to increase cooperation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0935-x) contains supplementary material, which is available to authorized users.

Efficacy of a probiotic bacterium to treat bats affected by the disease white‐nose syndrome

Summary The management of infectious diseases is an important conservation concern for a growing number of wildlife species. However, effective disease control in wildlife is challenging because feasible management options are often lacking. White‐nose syndrome (WNS) is an infectious disease of hibernating bats that currently threatens several North American species with extinction. Currently, no effective treatments exist for WNS. We conducted a laboratory experiment to test the efficacy of probiotic treatment with Pseudomonas fluorescens, a bacterium that naturally occurs on bats, to reduce disease severity and improve survival of little brown bats Myotis lucifugus exposed to Pseudogymnoascus destructans, the fungal pathogen that causes WNS. We found that application of the probiotic bacteria at the time of fungal infection reduced several measures of disease severity and increased survival, whereas bacterial treatment prior to pathogen exposure had no effect on survival and worsened disease severity. Synthesis and applications. Our results suggest that probiotic treatment with Ps. fluorescens has potential for white‐nose syndrome disease management, but the timing of application is critical and should coincide with natural exposure of bats to P. destructans. These results add to the growing knowledge of how natural host microbiota can be implemented as a biocontrol treatment to influence disease outcomes.

Which mechanisms drive seasonal rabies outbreaks in raccoons? A test using dynamic social network models

SummaryThe timing of raccoon rabies outbreaks in the easternUSAis non‐random and often exhibits a seasonal peak. While fluctuations in disease transmission can be driven by seasonal changes in animal population dynamics, behaviour and physiology, it is still unclear which causal factors lead to seasonal outbreaks of raccoon rabies.We used dynamic network modelling to test which of three seasonally changing factors are most likely responsible for raccoon rabies outbreaks: (i) birth pulses, (ii) changes in social network structure and (iii) changes in social contact duration.In contrast to previous predictions, we found that a change in social contact duration was the single most important driver of rabies seasonality. More specifically, co‐denning for thermoregulation during the winter increases the amount of time individuals spend in close contact, which in turn should lead to peaks in rabies transmission during the winter.Increased time spent in close proximity during cold winter months has implications for seasonal disease patterns in raccoon populations across a latitudinal gradient, as well as potentially being important for pathogens transmitted by close contact in other wildlife hosts.Synthesis and applications. By incorporating detailed empirical data describing variation in raccoon contacts into a network modelling framework, it is possible to determine the likely causal mechanisms driving seasonal disease patterns. This can be crucial information for wildlife and public health officials implementing wildlife disease control programmes.

Controlling of CSFV in European wild boar using oral vaccination: a review.

Classical swine fever (CSF) is among the most detrimental diseases for the swine industry worldwide. Infected wild boar populations can play a crucial role in CSF epidemiology and controlling wild reservoirs is of utmost importance for preventing domestic outbreaks. Oral mass vaccination (OMV) has been implemented to control CSF in wild boars and limit the spill over to domestic pigs. This retrospective overview of vaccination experiences illustrates the potential for that option. The C-strain live vaccine was confirmed to be highly efficacious and palatable baits were developed for oral delivery in free ranging wild boars. The first field trials were performed in Germany in the 1990’s and allowed deploying oral baits at a large scale. The delivery process was further improved during the 2000’s among different European countries. Optimal deployment has to be early regarding disease emergence and correctly designed regarding the landscape structure and the natural food sources that can compete with oral baits. OMV deployment is also highly dependent on a local veterinary support working closely with hunters, wildlife and forestry agencies. Vaccination has been the most efficient strategy for CSF control in free ranging wild boar when vaccination is wide spread and lasting for a sufficient period of time. Alternative disease control strategies such as intensified hunting or creating physical boundaries such as fences have been, in contrast, seldom satisfactory and reliable. However, monitoring outbreaks has been challenging during and after vaccination deployment since OMV results in a low probability to detect virus-positive animals and the live-vaccine currently available does not allow serological differentiation of infected from vaccinated animals. The development of a new marker vaccine and companion test is thus a promising option for better monitoring outbreaks during OMV deployment as well as help to better determine when to stop vaccination efforts. After rabies in red fox, the use of OMV against CSF in European wild boar can be considered as a second example of successful disease control in wildlife. The 30 years of disease control experience included in this review may provide options for improving future disease management within wild populations.

The Wild Side of Disease Control at the Wildlife-Livestock-Human Interface: A Review.

The control of diseases shared with wildlife requires the development of strategies that will reduce pathogen transmission between wildlife and both domestic animals and human beings. This review describes and criticizes the options currently applied and attempts to forecast wildlife disease control in the coming decades. Establishing a proper surveillance and monitoring scheme (disease and population wise) is the absolute priority before even making the decision as to whether or not to intervene. Disease control can be achieved by different means, including: (1) preventive actions, (2) arthropod vector control, (3) host population control through random or selective culling, habitat management or reproductive control, and (4) vaccination. The alternative options of zoning or no-action should also be considered, particularly in view of a cost/benefit assessment. Ideally, tools from several fields should be combined in an integrated control strategy. The success of disease control in wildlife depends on many factors, including disease ecology, natural history, and the characteristics of the pathogen, the availability of suitable diagnostic tools, the characteristics of the domestic and wildlife host(s) and vectors, the geographical spread of the problem, the scale of the control effort and stakeholders’ attitudes.

Trend of National and International Wildlife Disease Control

Trend of National and International Wildlife Disease Control

Sarcoptic-mange detector dogs used to identify infected animals during outbreaks in wildlife

BackgroundOne of the main aims of forensic investigation is the detection and location of people and substances of interest, such as missing people and illegal drugs. Dogs (Canis lupus var. familiaris) have had an important role in legal and forensic investigations for decades; nonetheless canines’ keen sense of smell has never been utilized in either the surveillance or control of wildlife diseases. The rapid removal and treatment of infected carcasses and/or sick animals is a key task in the management of infectious diseases, but it is usually difficult or impractical to carry out in the wild.ResultsIn this paper we report on a study running over a period of 15 years, in which - for the first time to our knowledge - two disease-detector dogs were trained to follow the scent of Sarcoptes-infected animals and to find carcasses, even under the snow, and apparently no false positives were detected in fieldwork. Sarcoptic mange-detector dogs were used to collect the carcasses of 292 mangy wild animals and to identify, separate from their herd, and capture 63 mange-infected wild animals in the Italian Alps.ConclusionsProperly trained disease-detector dogs are an efficient and straightforward tool for surveillance and control of sarcoptic mange in affected wild animal populations.

Sustainable control of zoonotic pathogens in wildlife: how to be fair to wild animals?

Wildlife may harbour infectious pathogens that are of zoonotic concern. However, culling such reservoir populations to mitigate or control the transmission of these pathogens to humans has proved disappointingly inefficient. Alternatives are still in an experimental stage of development. They include vaccination, medication, contraception and environmental manipulation, including fencing and biosecurity measures. This review examines the general concepts involved in the control of wildlife diseases and presents relevant case studies. Since wildlife disease control inevitably involves interfering with wildlife ecology, this is a complex goal whose attempts at realisation should be supervised by a scientific organisation. Most approaches within natural ecosystems should first be carefully tested in trials that are progressively extended to a larger scale. Finally, all measures that aim to prevent infection in humans (such as personal hygiene or vaccination) or that encourage us to avoid infectious contacts with wildlife should be recommended.

Specificity and success of oral-bait delivery to Eurasian wild boar in Mediterranean woodland habitats

Eurasian wild boar (Sus scrofa) is an important reservoir host for pathogens affecting humans and domestic animals. The eradication of these diseases may require the development of control strategies that reduce pathogen transmission between wildlife and domestic animals. Baiting for oral vaccine delivery is often considered for wildlife disease control. The effective and efficient field vaccination of wildlife requires species-specific baits as delivery vehicles for oral vaccines and designing appropriate baiting strategies. The objective of this study was to determine the proportion of young and adult wild boar and non-target animals that consumed baits containing a chemical marker, iophenoxic acid (IPA), in delivery trials conducted in summer in four different sites in the Mediterranean region of Spain where wild boar are abundant. The proportion of wild boar showing IPA markers in serum in autumn ranged from 11.5% to 56.4%. When attending to age classes, 12.6% to 72.7% of young individuals presented IPA. The results evidenced that the percent of wild boar that ingested the baits varied among study sites and age classes. Placing baits inside selective cages (for juveniles) and under heavy pavel stones (for adults) contributed to improve age specificity in bait consumption. We suggest ways for improving the age specificity of bait delivery systems used for young and adult wild boar.