New threats in the recovery of large carnivores inhabiting human-modified landscapes: the case of the Cantabrian brown bear (Ursus arctos)

Understanding mortality causes is important for the conservation of endangered species, especially in small and isolated populations inhabiting anthropized landscapes where both natural and human-caused mortality may hinder the conservation of these species. We investigated the mortality causes of 53 free-ranging brown bears (Ursus arctos) found dead between 1998 and 2023 in the Cantabrian Mountains (northwestern Spain), a highly human-modified region where bears are currently recovering after being critically threatened in the last century. We detected natural traumatic injuries in 52.63% and infectious diseases in 39.47% of the 38 bears for which the mortality causes were registered, with 21.05% of these cases presenting signs of both infectious diseases and traumas. More specifically, almost 30% of the bears died during or after intraspecific fights, including sexually selected infanticide (10.53%). In addition, primary infectious diseases such as infectious canine hepatitis, distemper, clostridiosis and colibacillosis caused the death of 15.79% of the bears. The number of direct human-caused deaths (i.e., shooting, poisoning, snare) decreased over the study period. This study also reveals three new mortality causes triggered by pathogens, two of which-Clostridium novyi and verotoxigenic Escherichia coli-not previously described in ursids, and the other one, canine distemper virus, never reported in brown bears as cause of death. New management strategies for the conservation of Cantabrian bears, which are urgently needed due to the rapid expansion of the population, should consider the mortality causes described in this study and must promote further research to elucidate how the high prevalence of infectious diseases may threaten the current recovery of the population.

The importance of long-term studies on wildlife diseases and their interfaces with humans and domestic animals: A review

Long-term wildlife disease research (LTWDR) and its interfaces with humans and domestic animals provide perspective to understand the diseases' main drivers and how they operate. In a systematic review, we analysed the temporal trend of the studies on LTWDR, their aims, and the hosts, pathogens and geographic areas studied. We also evaluated the added value that such studies provide. For analysis, we selected a total of 538 articles from 1993 to 2017 with a study period greater than or equal to 4 consecutive years. A marked increase in the number of studies published during the last 20 years was observed that reflects a growing awareness of the outstanding role of wildlife as a reservoir of diseases. The most studied pathogen agents were viruses (39.2%), bacteria (38.5%) and protozoans (15.8%). Concerning the hosts, mammals (84.9%), particularly ungulates (40%) and carnivores (30.9%), and birds (12.5%) were the most represented in these long-term studies. Most articles reached conclusions concerning the effect of the disease on the infection/host dynamics (98.7%) and over 40% considered the economic consequences or proposed management and control measures. The research was mainly located in the Northern Hemisphere. While the definition of LTWDR is not only determined by the duration of the monitoring, the study must be long enough to: (a) address ecological and epidemiological questions that cannot be resolved with short-term observations or experiments, and (b) clarify the effects of different drivers. This review demonstrates that LTWDR has provided information about the causes and consequences of disease change that otherwise could not have been obtained. It may be used to inform decisions related to the emergence of disease and might help to design early warning systems of disease based on retrospective investigations.

Enterocytozoon bieneusi (Microsporidia): Identification of novel genotypes and evidence of transmission between sympatric wild boars (Sus scrofa ferus) and Iberian pigs (Sus scrofa domesticus) in Southern Spain

Microsporidia is a phylum of obligate emergent intracellular protist-like fungi pathogens that infect a broad range of hosts including vertebrates and invertebrates. Enterocytozoon bieneusi is the most common cause of microsporidiosis in humans, affecting primarily immunosuppressed patients but also reported in immunocompetent individuals. Epidemiological information on the presence and molecular diversity of E. bieneusi in livestock and wildlife in Spain is limited. Therefore, the occurrence of this microsporidia was investigated in sympatric extensively reared Iberian pigs (n = 186) and free ranging wild boars (n = 142) in the province of Córdoba, Southern Spain. Forty-two Iberian pigs (22.6%) and three wild boars (2.1%) were found E. bieneusi positive by PCR. In Iberian pigs, occurrence of E. bieneusi was significantly higher in sows than in fattening pigs (31.6% vs. 11.4%; p = .001). Five genotypes were identified in Iberian pigs, four previously reported (EbpA, PigEb4, O, Pig HN-II) and a novel genotype (named PigSpEb1), while only two genotypes were identified in wild boars, EbpA and novel genotype PigSpEb1. All five genotypes identified belong to Group 1 suggesting zoonotic potential. This study constitutes the first report on the occurrence and molecular characterization of E. bieneusi in Iberian pigs and wild boars. The identification of two genotypes with zoonotic potential in sympatric Iberian pigs and wild boars suggests that E. bieneusi can be potentially transmitted between those two hosts, but also implies that they may act as natural sources of microsporidia infection to other hosts including humans.

Spatio-temporal trends in the frequency of interspecific interactions between domestic and wild ungulates from Mediterranean Spain

Controlling infections shared by wildlife and livestock requires the understanding and quantification of interspecific interactions between the species involved. This is particularly important in extensive multi-host systems, in which controlled domestic animals interact with uncontrolled, abundant and expanding wild species, such as wild ungulates. We have, therefore, quantified the interspecific interactions between wild boar (Sus scrofa) and free-ranging cattle in Mediterranean Spain, along with their spatio-temporal variability. GPS-GSM-collars were used to monitor 12 cows and 14 wild boar in the Doñana National Park between 2011 and 2013. Interactions were defined as encounters between cattle and wild boar within a spatio-temporal window of 52 m and 1 hour. On average, each wild boar interacted with one cow 1.5 ± (SE) 0.5 times per day, while each cow interacted with one wild boar 1.3 ± 0.4 times per day. The frequency of interaction was significantly higher during crepuscular hours owing to the overlap of both species’ activity, and also during spring and autumn, probably owing to a higher individual aggregation around shared resources. Finally, the frequency of interaction was higher near the most significant shared resources (e.g. water points) but was lower in areas with dense vegetation. The results presented here show the usefulness of GPS monitoring as regards quantifying interactions and helping to clarify the process of pathogen transmission at the wildlife-livestock interface in Mediterranean Spain, along with the main spatio-temporal risk factors. In a changing scenario in which European populations of wild ungulates are increasing, more efficient measures with which to control interactions are required to meet the demands of farmers and managers. Our results, therefore, provide directional hypotheses that could be used to design disease control programmes.

Coxiella burnetii in wild mammals: A systematic review

Coxiella burnetii is a multi-host bacterium that causes Q fever in humans, a zoonosis that is emerging worldwide. The ecology of C. burnetii in wildlife is still poorly understood and the influence of host, environmental and pathogen factors is almost unknown. This study gathers current published information on different aspects of C. burnetii infection in wildlife, even in species with high reservoir potential and a high rate of interaction with livestock and humans, in order to partially fill the existing gap and highlight future needs. Exposure and/or infection by C. burnetii has, to date, been reported in 109 wild mammal species. The limited sample size of most of the existing studies could suggest an undervalued prevalence of C. burnetii infection. Knowledge on the clinical outcome of C. burnetii infection in wildlife is also very limited, but currently includes reproductive failure in waterbuck (Kobus ellipsiprymnus), roan antelope (Hippotragus niger), dama gazelle (Nanger dama) and water buffalo (Bubalus bubalis) and placentitis in the Pacific harbor seal (Phoca vitulina richardsi), Steller sea lion (Eumetopias jubatus) and red deer (Cervus elaphus). The currently available serological tests need to be optimised and validated for each wildlife species. Finally, there is a huge gap in the research on C. burnetii control in wildlife, despite of the increasing evidence that wildlife is a source of C. burnetii for both livestock and humans.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine tuberculosis

Bovine tuberculosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of bovine tuberculosis to be listed, Article 9 for the categorisation of bovine tuberculosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to bovine tuberculosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, bovine tuberculosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 2, 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (b), (c), (d) and (e) of Article 9(1). The main animal species to be listed for bovine tuberculosis according to Article 8(3) criteria are several mammal species, as indicated in the present opinion.

Eucoleus boehmi infection in red fox (Vulpes vulpes) from Italy

In the last decade an increase of the number of red foxes in anthropized habitats across European countries, including Italy, has been observed. This pones implications in terms of disease transmission between wildlife and domestic animals; in fact, there are evidences of the role of foxes as reservoirs and amplifiers of a broad spectrum of parasites infecting pets. The present study evaluated the prevalence of Eucoleus boehmi, an emerging extra-intestinal nematodes of the Capillariinae subfamily, in red foxes. The nasal passages and sinuses of 179 red foxes culled from several areas of northern and central Italy were inspected and the mucosal surfaces were scrapped and examined for adult nematodes and eggs, microscopically and genetically identified. Overall 55 foxes (30.7%) were found to be infected with E. boehmi, i.e. 27 on inspection of the nasal passages and sinuses and 28 on mucosal flush and scraping. The occurrence of E. boehmi was significantly (p < 0.05) correlated to the sampling location, the age and gender of the animals examined; the higher rates of prevalence were observed in animals culled in Piedmont (43.3%) and in female (60.6%) and adult (38.1%) subjects. A total of 184 adult parasites were recovered, with a mean intensity of infection of 3.34, and a more frequent localization of E. boehmi in the nasal passages rather than in the sinuses. A significant (p < 0.05) relationship was found between the parasite burden and body condition and age of the animals; the intensity of infection was significantly higher in juveniles (mean: 6.3 specimens) and in animals showing poor fox body condition (mean: 7.8 specimens). These results show that E. boehmi is highly prevalent in the red fox populations of certain areas of Italy. Epidemiological implications are discussed, with a special focus on the role that this wild canid may have in the increasing transmission of nasal eucoleosis to domestic dogs.

Stakeholder opinions on the practicality of management interventions to control bovine tuberculosis

Livestock disease control strategies are usually determined at national and international levels, yet their successful implementation is determined by stakeholders operating at local scales. Such stakeholders may also have detailed knowledge that would contribute to the development of disease control options suited to the socio-cultural and environmental conditions where management is undertaken. The aim of this study was to evaluate stakeholders' opinions of a list of potential bovine tuberculosis (TB) management interventions for South Central Spain. This area has high TB prevalence in wildlife and livestock, so veterinarians, livestock farmers and hunters are all key stakeholders in TB management. A literature review identified possible management activities. The effectiveness of each intervention was ranked by local experts, and practicality was ranked by hunters, cattle farmers and veterinarians, using a best-worst scaling exercise as part of a questionnaire. The most effective intervention, the banning of supplemental feeding of game species, was not considered practical by stakeholders. The most effective and practical interventions were the separation of wildlife and livestock access to waterholes, testing cattle every 3 months on farms with a recent positive TB case and removing gut-piles from the land after hunting events. Although all three of these options were well supported, each stakeholder group supported different approaches more strongly, suggesting that it might be effective to promote different disease management contributions in different stakeholder communities. This integrated approach contributes to the identification of the optimum combination of management tools that can be delivered effectively.

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.

Wild boar: an increasing concern for Aujeszky's disease control in pigs?

BACKGROUND

The goal of this study was describing the temporal evolution of Aujeszky's disease virus (ADV) contact prevalence among Eurasian wild boar (Sus scrofa) populations under different management regimes and contact likelihoods with domestic pigs. Given the recent increase in wild boar abundance throughout Europe, we hypothesized that wild boar contact with ADV would remain stable in time even after significant reduction of ADV prevalence in domestic pigs.

RESULTS

Sera from 1659 wild boar were collected from 2000 to 2010 within 6 areas of the Iberian Peninsula and tested for the presence of antibodies against ADV by ELISA. According to sampling date, wild boar were grouped into three time periods. ADV prevalence was compared through period both globally and by geographic area. Overall seroprevalence for the ten-year study period was 49.6 ± 2.4%. The highest seroprevalence was recorded in areas with intense wild boar management. The annual proportion of positive wild boar sampling sites remained stable through the study period, while the percentage of domestic pig AD positive counties decreased from 70% in 2003 to 1.7% in 2010.

CONCLUSIONS

Results presented herein confirmed our hypothesis that ADV would remain almost stable in wild boar populations. This evidences the increasing risk wild boar pose in the final stages of ADV eradication in pigs and for wildlife conservation.

Seroprevalence evolution of selected pathogens in Iberian wild boar

A total of 1279 Eurasian wild boar (Sus scrofa) sera were collected from 2000 to 2011 in the Iberian Peninsula to reveal time changes in serum antibody prevalences against selected infectious agents (porcine circovirus type 2, PCV2; porcine reproductive and respiratory syndrome virus, PRRSV; hepatitis E virus, HEV; and Erysipelothrix rhusiopathiae) and to identify putative individual or population factors driving such changes. Overall seroprevalences were 48%, 26%, 2% and 15% for PCV2, HEV, PRRSV and E. rhusiopathiae, respectively. The global observed prevalence of antibodies against PCV2 and HEV remained stable during the study period, while the global mean antibody seroprevalence against E. rhusiopathiae declined. The mean increment in prevalence was always lower for open than for fenced sites. This study evidenced for the first time that wild boar from the Iberian Peninsula have widespread contact with E. rhusiopathiae, and confirmed high prevalences of antibodies against PCV2 and HEV. Maintained high prevalences of transmissible agents in wild boar suggest that epidemiological drivers such as aggregation and high density are still acting. This will most probably also affect the transmission rates of other disease agents and should be taken into account regarding disease control at the wildlife-livestock interface.

Protection against tuberculosis in Eurasian wild boar vaccinated with heat-inactivated Mycobacterium bovis

Tuberculosis (TB) caused by Mycobacterium bovis and closely related members of the Mycobacterium tuberculosis complex continues to affect humans and animals worldwide and its control requires vaccination of wildlife reservoir species such as Eurasian wild boar (Sus scrofa). Vaccination efforts for TB control in wildlife have been based primarily on oral live BCG formulations. However, this is the first report of the use of oral inactivated vaccines for controlling TB in wildlife. In this study, four groups of 5 wild boar each were vaccinated with inactivated M. bovis by the oral and intramuscular routes, vaccinated with oral BCG or left unvaccinated as controls. All groups were later challenged with a field strain of M. bovis. The results of the IFN-gamma response, serum antibody levels, M. bovis culture, TB lesion scores, and the expression of C3 and MUT genes were compared between these four groups. The results suggested that vaccination with heat-inactivated M. bovis or BCG protect wild boar from TB. These results also encouraged testing combinations of BCG and inactivated M. bovis to vaccinate wild boar against TB. Vaccine formulations using heat-inactivated M. bovis for TB control in wildlife would have the advantage of being environmentally safe and more stable under field conditions when compared to live BCG vaccines. The antibody response and MUT expression levels can help differentiating between vaccinated and infected wild boar and as correlates of protective response in vaccinated animals. These results suggest that vaccine studies in free-living wild boar are now possible to reveal the full potential of protecting against TB using oral M. bovis inactivated and BCG vaccines.

Interdisciplinary approaches for the management of existing and emerging human - wildlife conflicts

Human–wildlife conflicts are increasing throughout the world, principally due to a combination of human population growth, increased pressure on land and natural resources and climate change. Many human–wildlife conflicts stem from differences in objectives between various stakeholder groups, especially where the wildlife in question is a resource that can be exploited for economic or cultural benefit, or where the conservation of wildlife is at odds with human population growth or development pressure. Conflicts can be exacerbated by an incomplete understanding of their causes and/or inappropriate intervention measures. Many traditional forms of intervention are also subject to increasing scrutiny and criticism from society. Here, we highlight the potential strategic benefits that can be made by an interdisciplinary approach to human–wildlife conflict situations, by integrating knowledge and understanding across the natural and social sciences. We also stress the potential tactical benefits from combining new approaches to management with more traditional ones. We emphasise the potential contribution of more recent developments in decision-making under conditions of limited data availability and uncertainty. Finally, we recommend that monitoring should play a more prominent role, both in assessing the role of stakeholder engagement in participatory decision-making and in contributing to the evidence base that will allow competing hypotheses about specific systems to be evaluated in an iterative manner.