Non-invasive surveillance of shared pathogens in the Eurasian brown bear (Ursus arctos) human interface.

Multi-host communities are perfect scenarios for the emergence and spread of pathogens, threatening the recovery of endangered, isolated, or inbred populations, such as the brown bear (Ursus arctos) in northwestern Spain. The population recovery in recent years has forced bears to occupy highly anthropized areas, increasing their interaction with human and domestic animals, with potential consequences for global health. During 2022-2023 a survey of parasites, bacteria and viruses shared between wildlife, domestic animals and humans was performed in this population using non-invasive surveillance, i.e., bear fecal samples (n = 73) and sponge-based sampling of trees (n = 42; 14 rubbed trees and 28 control trees). Pathogen detection rates were defined as the percentage of qPCR or culture-positive samples. Generalized linear models were fitted to assess their relationship with environmental variables including dispersion of the human population, and percentage of agricultural and periurban habitats in a 6 km-buffer around each sample. Canine Adenovirus type 1 (45.2%), Giardia spp. (15.1%), Salmonella spp. (12.3%), and extended-spectrum-beta-lactamases (ESBL) Escherichia coli (1.4%) were identified in fecal samples. In contrast, only five sponges from three rubbed and two control trees resulted positive to E. coli (14.3%). The results suggest that several pathogens are common in the Cantabrian brown bear population and that anthropization of the territory modulates their prevalence and richness. The effective design of management programs for bear conservation will require a one-health approach, in which genetic analysis of non-invasive samples can be key tools for the sanitary surveillance at the wildlife-livestock-human interface.

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.

Efficacy of heat-inactivated Mycobacterium bovis vaccine delivered to European badgers (Meles meles) through edible bait.

Badgers (Meles meles) are a major tuberculosis (TB) reservoir in Europe, with the potential to transmit infection to cattle. Here we assessed whether a recently described oral tuberculosis vaccine based on heat-inactivated Mycobacterium bovis (HIMB), delivered as edible baits, can protect badgers from infection. Eight badgers were given individually five baits, each one consisting of a ball of peanut butter, natural peanut and oat flakes including a dose of the vaccine containing 5 × 107 colony-forming units. In parallel, a control group of seven badgers did not receive the vaccine. One month and a half later a second dose of the vaccine was offered to the vaccinated group. Ninety-four days after the second dose, all badgers were challenged with M. bovis (103 colony-forming units per animal) delivered endobronchially to the right middle lung lobe. Clinical, immunological, pathological and bacteriological variables were measured throughout the whole study to assess the efficacy of the vaccine. Two vaccinated animals showed high bacterial load of M. bovis and worsening of pathological lesions of TB. Conversely, the other six vaccinated animals showed slight improvement in bacterial load and pathology with respect to the control group. These results suggest that delivering the TB vaccine via food bait can partially protect wild badger populations, although vaccination can lead to either protection or tolerization, likely depending on the animal's immune status and general condition at the time of vaccination. Further optimization of the vaccination trial/strategy is needed to reduce the rate of tolerization, such as altering vaccine dose, number of doses, type of bait, use of adjuvants or route of administration.

Hypertrophic osteopathy in a common dolphin (Delphinus delphis) with concurrent pulmonary Halocercus delphini infestation.

Dolphins are marine mammals that often live in coastal habitats. Common causes of severe skeletal disorders among wild dolphins are congenital vertebral anomalities, collisions with sea vessels, trauma, hunting-related injury, infectious diseases, environmental pollution, and tumors. A free-ranging male, 3-year-old common dolphin (Delphinus delphis) was found dead in the coast of Asturias in northern Spain. Postmortem examination revealed lordosis in the caudal vertebral column, while X-ray imaging and computer tomography showed well-organized palisade-like periosteal proliferation, appearing as florid-like accretions, along the spinous apophysis of 26 lumbar-caudal vertebrae. The transverse apophysis was affected on only a few caudal vertebrae. The cortical layer remained intact. Histology of vertebra tissue showed periosteal proliferation of cancellous bone. The animal was diagnosed with hypertrophic osteopathy. The lungs showed diffuse parasitic granulomatous bronchointerstitial pneumonia caused by Halocercus delphini, consolidation of the pulmonary tissue, congestion, and alveolar edema. The animal was also afflicted by parasitic granulomatous gastritis caused by Anisakis simplex sensu lato and tattoo skin disease. The dolphin suffered from hypertrophic osteopathy associated with pulmonary Halocercus delphini infestation. This syndrome, known as hypertrophic pulmonary osteopathy, has been described in diverse terrestrial mammals, including domestic animals, wildlife and humans, but not in dolphins. This case reports the first description of hypertrophic osteopathy associated to a pulmonary disorder in dolphin, and it provides insights into factors that can induce column malformation in dolphins, suggesting the importance of taking thoracic lesions into account during differential diagnosis.

Mortality Causes in Captive Cantabrian capercaillie (Tetrao urogallus cantabricus) in Spain.

The Cantabrian capercaillie (Tetrao urogallus cantabricus) is one of the most severely threatened subspecies of capercaillie. Its current population range is restricted to a small area of the Cantabrian Mountains (northwestern Spain), with only around 200 individuals remaining. As part of the national strategy for the conservation of the subspecies, the Cantabrian capercaillie Captive Breeding Center of Sobrescobio opened in 2009. Here, we use the information provided by the necropsies performed in this facility on 29 individuals (11 males, 13 females and 5 undetermined; 16 chicks and 13 adults) in order to describe the main mortality causes of captive-bred Cantabrian capercaillies. After necropsy, tissue samples were taken for evaluation using standard methods in histology and microbiology. The majority of the captive animals (18/29, 62.07%) died due to infectious diseases, mainly due to Escherichia coli, Clostridium perfringens, or Aspergillus fumigatus infection. The remaining 11 animals died due to stress-related processes (i.e., rupture of the heart apex and cardiomyopathy or neurogenic shock) (8/29, 27.59%), duodenal obstruction and coelomitis (1/29, 3.45%), perforation of the proventriculus and heart with a briar branch (1/29, 3.45%) or euthanasia due to a valgus leg deformity that prevented proper animal welfare (1/29, 3.45%). Young animals (i.e., younger than 2 months) died mainly due to infectious diseases (14/16, 87.5%), while stress-related causes were responsible for most adult deaths (7/13, 53.85%). We additionally report that two free-ranging adult males died due to exertional myopathy. This study provides relevant information for reducing mortality in captive capercaillies and improving both living conditions in captivity and the adaptation of these animals to the wild.

Determinants of Crimean-Congo haemorrhagic fever virus exposure dynamics in Mediterranean environments.

Crimean-Congo haemorrhagic fever (CCHF) is an emerging tick-borne human disease in Spain. Understanding the spatiotemporal dynamics and exposure risk determinants of CCHF virus (CCHFV) in animal models is essential to predict the time and areas of highest transmission risk. With this goal, we designed a longitudinal survey of two wild ungulate species, the red deer (Cervus elaphus) and the Eurasian wild boar (Sus scrofa), in Doñana National Park, a protected Mediterranean biodiversity hotspot with high ungulate and CCHFV vector abundance, and which is also one of the main stopover sites for migratory birds between Africa and western Europe. Both ungulates are hosts to the principal CCHFV vector in Spain, Hyalomma lusitanicum. We sampled wild ungulates annually from 2005 to 2020 and analysed the frequency of exposure to CCHFV by a double-antigen ELISA. The annual exposure risk was modelled as a function of environmental traits in an approach to understanding exposure risk determinants that allow us to predict the most likely places and years for CCHFV transmission. The main findings show that H. lusitanicum abundance is a fundamental driver of the fine-scale spatial CCHFV transmission risk, while inter-annual risk variation is conditioned by virus/vector hosts, host community structure and weather variations. The most relevant conclusion of the study is that the emergence of CCHF in Spain might be associated with recent wild ungulate population changes promoting higher vector abundance. This work provides relevant insights into the transmission dynamics of CCHFV in enzootic scenarios that would allow deepening the understanding of the ecology of CCHFV and its major determinants.