Disease-mediated bottom-up regulation: An emergent virus affects a keystone prey, and alters the dynamics of trophic webs

Rabbit hemorrhagic disease virus 2, 2010-2023: a review of global detections and affected species

Rabbit hemorrhagic disease virus 2/genotype GI.2 (RHDV2/GI.2; Caliciviridae, Lagovirus) causes a highly contagious disease with hepatic necrosis and disseminated intravascular coagulation in several Leporidae species. RHDV2 was first detected in European rabbits (Oryctolagus cuniculus) in France in 2010 and has since spread widely. We gather here data on viral detections reported in various countries and affected species, and discuss pathology, genetic differences, and novel diagnostic aspects. RHDV2 has been detected almost globally, with cases reported in Europe, Africa, Oceania, Asia, and North America as of 2023. Since 2020, large scale outbreaks have occurred in the United States and Mexico and, at the same time, cases have been reported for the first time in previously unaffected countries, such as China, Japan, Singapore, and South Africa, among others. Detections have been notified in domestic and wild European rabbits, hares and jackrabbits (Lepus spp.), several species of cottontail and brush rabbits (Sylvilagus spp.), pygmy rabbits (Brachylagus idahoensis), and red rock rabbits (Pronolagus spp.). RHDV2 has also been detected in a few non-lagomorph species. Detection of RHDV2 causing RHD in Sylvilagus spp. and Leporidae species other than those in the genera Oryctolagus and Lepus is very novel. The global spread of this fast-evolving RNA virus into previously unexploited geographic areas increases the likelihood of host range expansion as new species are exposed; animals may also be infected by nonpathogenic caliciviruses that are disseminated by almost all species, and with which genetic recombination may occur.

Antibody response of endangered riparian brush rabbits to vaccination against rabbit hemorrhagic disease virus 2

Rabbit hemorrhagic disease virus 2 (RHDV2; Caliciviridae, Lagovirus europaeus), the cause of a highly transmissible and fatal lagomorph disease, has spread rapidly through the western United States and Mexico, resulting in substantial mortality in domestic and wild rabbits. The disease was first detected in California in May 2020, prompting an interagency/zoo/academia/nonprofit team to implement emergency conservation actions to protect endangered riparian brush rabbits (Sylvilagus bachmani riparius) from RHDV2. Prior to vaccinating wild rabbits, we conducted a vaccine safety trial by giving a single SC dose of Filavac VHD K C+V (Filavie) vaccine to 19 adult wild riparian brush rabbits captured and temporarily held in captivity. Rabbits were monitored for adverse effects, and serum was collected before vaccination, and at 7-10, 14-20, and 60 d post-vaccination. Sera were tested using an ELISA to determine antibody response and timing of seroconversion. Reverse-transcription quantitative real-time PCR (RT-qPCR) was performed on rectal swabs to evaluate infection status. No adverse effects from the vaccine were observed. Before vaccination, 18 of 19 rabbits were seronegative, and RHDV2 was not detected by RT-qPCR on any rectal swabs. After vaccination, all rabbits developed an antibody response, with titers of 1:10-1:160. Seroconversion generally occurred at 7-10 d. The duration of antibody response was ≥60 d in 12 of 13 rabbits. Sixteen animals were released and 4 were recaptured several months later, offering a glimpse into longer duration immune response. Our study has informed vaccination strategies for this species and serves as a model for protecting other vulnerable lagomorphs against RHDV2.

A natural ANI gap that can define intra-species units of bacteriophages and other viruses

Despite the importance of intra-species variants of viruses for causing disease and/or disrupting ecosystem functioning, there is no universally applicable standard to define these. A (natural) gap in whole-genome average nucleotide identity (ANI) values around 95% is commonly used to define species, especially for bacteriophages, but whether a similar gap exists within species that can be used to define intra-species units has not been evaluated yet. Whole-genome comparisons among members of 1,016 bacteriophage (Caudoviricetes) species revealed a region of low frequency of ANI values around 99.2%-99.8%, showing threefold or fewer pairs than expected for an even distribution. This second gap is prevalent in viruses infecting various cultured or uncultured hosts from a variety of environments, although a few exceptions to this pattern were also observed (3.7% of total species) and are likely attributed to cultivation biases or other factors. Similar results were observed for a limited set of eukaryotic viruses that are adequately sampled, including SARS-CoV-2, whose ANI-based clusters matched well with the WHO-defined variants of concern, indicating that our findings from bacteriophages might be more broadly applicable and the ANI-based clusters may represent functionally and/or ecologically distinct units. These units appear to be predominantly driven by (high) ecological cohesiveness coupled to either frequent recombination for bacteriophages or selection and clonal evolution for other viruses such as SARS-CoV-2, indicating that fundamentally different underlying mechanisms could lead to similar diversity patterns. Accordingly, we propose the ANI gap approach outlined above for defining viral intra-species units, for which we propose the term genomovars.

IMPORTANCE

Viral species are composed of an ensemble of intra-species variants whose individual dynamics may have major implications for human and animal health and/or ecosystem functioning. However, the lack of universally accepted standards to define these intra-species variants has led researchers to use different approaches for this task, creating inconsistent intra-species units across different viral families and confusion in communication. By comparing hundreds of mostly bacteriophage genomes, we show that there is a widely distributed natural gap in whole-genome average nucleotide identity values in most, but not all, of these species that can be used to define intra-species units. Therefore, these results advance the molecular toolbox for tracking viral intra-species units and should facilitate future epidemiological and environmental studies.

Detections of Rabbit Hemorrhagic Disease Virus 2 (RHDV2) Following the 2020 Outbreak in Wild Lagomorphs across the Western United States

Rabbit hemorrhagic disease virus 2 (RHDV2) is a highly infectious, often fatal viral disease that affects both domestic and wild lagomorph species. In the United States (U.S.), the virus first was detected in wild lagomorph populations in the southwest in March 2020 and has continued to be detected in native North American lagomorph species over several years. The susceptibility of host species and exact mechanisms of environmental transmission across the U.S. landscape remain poorly understood. Our study aims to increase the understanding of RHDV2 in wild lagomorph populations by providing a history of detection. We present and summarize results from all RHDV2-suspect wild lagomorph morbidity and mortality samples submitted for diagnostic testing in the U.S. from March 2020 to March 2024. Samples were submitted from 916 wild lagomorphs across eight native North American species in 14 western states, of which 313 (34.2%) tested positive by RHDV2 RT-qPCR. Detections of RHDV2 in pygmy rabbits (Brachylagus idahoensis) and riparian brush rabbits (Sylvilagus bachmani riparius) suggest that the risk to threatened and endangered species warrants more attention. Continuing to investigate wild lagomorph morbidity and mortality events and tracking RHDV2 detections over time can help inform on disease epidemiology and wild lagomorph population trends.

Understanding rabbit owners' willingness to engage in disease prevention behaviors

Rabbit hemorrhagic disease virus 2 (RHDV2) is a fatal, highly contagious pathogen that infects wild and domestic lagomorphs (rabbits and hares). RHDV2 is an important cause of disease in pet and companion rabbits, has resulted in economic losses for the commercial rabbit industry, and has caused declines of wild lagomorph populations. It is essential for domestic rabbit owners to engage in appropriate actions (e.g., using effective disinfectants, creating secure barriers between domestic and wild rabbits) to protect the health and welfare of their rabbits and reduce the risk of human-mediated spread of RHDV2. Thus, we investigated rabbit owners' stated willingness to engage in nine commonly recommended biosecurity practices and their support for seven potential government-implemented management actions. We administered an online survey to 1790 rabbit owners in the United States between April and August 2021. Respondents were likely to engage in all biosecurity measures and were supportive of most management actions that could be implemented by government agencies. Respondents' willingness to engage in and support biosecurity measures was positively correlated with their perceptions of the importance of biosecurity, risk perceptions pertaining to the impact of RHDV2 on lagomorphs and rabbit-related industries, knowledge of RHDV2, and trust in government to manage RHDV2. Respondents' motivations for owning rabbits, husbandry behaviors, and demographic characteristics also influenced their willingness to engage in or support biosecurity measures. Engaging domestic rabbit owners in collaborative biosecurity measures is critical for protecting domestic rabbit health and preventing potential spillover between domestic and free-roaming lagomorphs, as there are still many uncertainties about how RHDV2 is spreading across the United States and the world. Implementing outreach strategies that communicate the importance and effectiveness of biosecurity practices in protecting rabbit welfare, rabbit-related activities, and wild lagomorph populations may increase the likelihood of rabbit owners adopting biosecurity measures.

Dynamics of Humoral Immunity to Myxoma and Rabbit Hemorrhagic Disease Viruses in Wild European Rabbits Assessed by Longitudinal Semiquantitative Serology

Myxoma virus (MYXV) and rabbit hemorrhagic disease virus (RHDV) are important drivers of the population decline of the European rabbit, an endangered keystone species. Both viruses elicit strong immune responses, but the long-term dynamics of humoral immunity are imperfectly known. This study aimed to assess the determinants of the long-term dynamics of antibodies to each virus based on a longitudinal capture-mark-recapture of wild European rabbits and semiquantitative serological data of MYXV and RHDV GI.2-specific IgG. The study included 611 indirect enzyme-linked immunosorbent assay (iELISA) normalized absorbance ratios for each MYXV and RHDV GI.2 from 505 rabbits from 2018 to 2022. Normalized absorbance ratios were analyzed using log-linear mixed models, showing a significant positive relationship with the time since the first capture of individual rabbits, with monthly increases of 4.1% for antibodies against MYXV and 2.0% against RHDV GI.2. Individual serological histories showed fluctuations over time, suggesting that reinfections boosted the immune response and likely resulted in lifelong immunity. Normalized absorbance ratios significantly increased with the seroprevalence in the population, probably because of recent outbreaks, and with body weight, highlighting the role of MYXV and RHDV GI.2 in determining survival to adulthood. Juvenile rabbits seropositive for both viruses were found, and the dynamics of RHDV GI.2 normalized absorbance ratios suggest the presence of maternal immunity up to 2 months of age. Semiquantitative longitudinal serological data provide epidemiological information, otherwise lost when considering only qualitative data, and support a lifelong acquired humoral immunity to RHDV GI.2 and MYXV upon natural infection. IMPORTANCE This study addresses the long-term dynamics of humoral immunity to two major viral pathogens of the European rabbit, an endangered keystone species of major ecological relevance. Such studies are particularly challenging in free-ranging species, and a combination of longitudinal capture-mark-recapture and semiquantitative serology was used to address this question. Over 600 normalized absorbance ratios of iELISA, obtained from 505 individual rabbits in 7 populations over 5 years, were analyzed using linear mixed models. The results support a lifelong acquired humoral immunity to myxoma virus and rabbit hemorrhagic disease virus upon natural infection and suggest the presence of maternal immunity to the latter in wild juvenile rabbits. These results contribute to understanding the epidemiology of two viral diseases threatening this keystone species and assist in developing conservation programs.

Comparison of the Impact between Classical and Novel Strains of Rabbit Haemorrhagic Disease on Wild Rabbit Populations in Spain

The outbreaks of two strains of rabbit haemorrhagic disease (RHD) (GI.1 and GI.2) in the Iberian Peninsula have caused substantial economic losses in commercial rabbitries and have affected the conservation of rabbit-sensitive predators due to the dramatic decline of their natural populations. However, the assessment of the impact of both RHD strains on wild rabbit populations has been limited to a few small-scale studies. Little is known about the overall impact within its native range. In this study, we described and compared the effects of GI.1 and GI.2 countrywide by using time series of hunting bag data widely available across the country and compared their trend during the first eight years after the first outbreak of GI.1 (i.e., 1998) and GI.2 (i.e., 2011), respectively. We used Gaussian generalised additive models (GAM) with the number of hunted rabbits as the response variable and year as the predictor to evaluate the non-linear temporal dynamics of the population at the national and regional community levels. The first GI.1 caused a population decline of around 53%, affecting most Spanish regional communities where the disease occurred. The positive trend observed after GI.1 in Spain ended with the initial outbreak of GI.2, which did not appear to cause a national population decline. In contrast, we found significant variability in the rabbit population trend among regional communities, where some increased, and others decreased. Such a disparity is unlikely to be explained by a single factor; rather, it appears to result from several factors, such as climatic conditions, host resistance improvement, virulence attenuation, or population density. Our study suggests that a national comprehensive hunting bag series could aid in elucidating the differences in the impact of emerging diseases on a large scale. Future research should focus on national longitudinal serological studies to shed light on the immunological status of rabbit populations in different regions to better understand the evolution of RHD strains and the resistance gained by the wild populations.

Occurrence of Lagovirus europaeus (Rabbit Hemorrhagic Disease Virus) in Domestic Rabbits in Southwestern Poland in 2019: Case Report

Lagovirus europaeus (rabbit hemorrhagic disease virus [RHDV]) is a small, nonenveloped, single-stranded RNA virus that causes a severe, highly infectious, and fatal disease in rabbits (Oryctolagus cuniculus) called rabbit hemorrhagic disease (RHD). Since its discovery in the 1980s, it has posed a very serious threat to the global rabbit industry and the rabbit population in the wild. According to data from 2005 to 2018, the occurrence of RHD has been reported or suspected in 50 countries, with more than one-half of the reports being recorded in European countries. The main aim of the study was to detect Lagovirus europaeus (RHDV) strains found in domestic rabbits that died suddenly in the city of Wrocław in southwest Poland. All animals (n = 14) tested in this study died naturally and showed macroscopic features at necropsy that indicated the possibility of death from RHD. As a result of the research, the presence of L. europaeus virus was confirmed in 8 samples of all 14 samples collected. All strains of Lagovirus europaeus isolated in the present study showed 100% nucleotide identity to L. europaeus GI.1 strain FRG and a strain isolated in New Zealand, as well as the L. europaeus GI.1a Erfurt strain. This suggests that it is likely that L. europaeus GI.2 strains have so far not displaced L. europaeus GI.1 strains from the environment in Poland. IMPORTANCE Lagovirus europaeus (RHDV) causes a severe, highly infectious, and fatal disease in rabbits called RHD. The disease is a very serious threat to the global rabbit industry and the rabbit population in the wild. The aim of the study was to detect Lagovirus europaeus (RHDV) strains in domestic rabbits that died suddenly in Poland. The presence of RHDV was confirmed in 8 samples of all 14 samples collected. This is one of the very few reports on the existence of this virus in pet rabbits in Poland.

Down the Rabbit Hole: Domestic Rabbit Owners' Perceptions of Rabbit Hemorrhagic Disease Virus 2

Rabbit hemorrhagic disease virus 2 (RHDV2) is a highly contagious pathogen that infects wild and domestic rabbits and hares (lagomorphs). Globally, RHDV2 has resulted in substantial economic losses for commercial rabbit trade and caused wild lagomorph population declines. Previous research on RHDV2 suggests that human-mediated movement of rabbits may contribute to the spread of RHDV2. We conducted the first survey of individuals who own or interact with domestic rabbits to identify their rabbit husbandry behaviors and knowledge of, and concerns about, RHDV2. In 2021, we surveyed 1807 rabbit owners, breeders, and rescue staff in the USA. Respondents had a high level of knowledge about RHDV2. Respondents believed RHDV2 posed a high risk to rabbit-related activities and were concerned about its economic and ecological impacts. Nearly half of respondents always kept their rabbits indoors, but 10.7% of respondents allowed their rabbits outside frequently on properties used by wild lagomorphs. Respondents with five rabbits or less were generally willing to vaccinate their rabbits, but respondents with larger herds argued that vaccines were cost prohibitive. Given respondents' concerns about RHDV2, communication about disease prevention should highlight the adverse ecological and economic consequences of RHDV2.

Hinfluences severe disease-mediated population declines in two of the most common garden bird species in Great Britain

The influence of supplementary feeding of wildlife on disease transmission and its consequent impacts on population dynamics are underappreciated. In Great Britain, supplementary feeding is hypothesised to have enabled the spread of the protozoan parasite, Trichomonas gallinae, from columbids to finches, leading to epidemic finch trichomonosis and a rapid population decline of greenfinch (Chloris chloris). More recently, chaffinch (Fringilla coelebs), has also declined markedly from the second to fifth commonest bird in Britain. Using citizen science data, we show that both declines were driven primarily by reduced adult survival, with the greatest reductions occurring in peri-domestic habitats, where supplementary food provision is common. Post-mortem examinations showed a proportional increase in chaffinch trichomonosis cases, near-contemporaneous with its population decline. Like greenfinches, chaffinches often use supplementary food, but are less associated with human habitation. Our results support the hypothesis that supplementary feeding can increase parasite transmission frequency within and between common species. However, the dynamics behind resultant population change can vary markedly, highlighting the need for integrating disease surveillance with demographic monitoring. Other species susceptible to T. gallinae infection may also be at risk. Supplementary feeding guidelines for wildlife should include disease mitigation strategies to ensure that benefits to target species outweigh risks.

Comparison of Biological Features of Wild European Rabbit Mesenchymal Stem Cells Derived from Different Tissues

Although the European rabbit is an "endangered" species and a notorious biological model, the analysis and comparative characterization of new tissue sources of rabbit mesenchymal stem cells (rMSCs) have not been well addressed. Here, we report for the first time the isolation and characterization of rMSCs derived from an animal belonging to a natural rabbit population within the native region of the species. New rMSC lines were isolated from different tissues: oral mucosa (rOM-MSC), dermal skin (rDS-MSC), subcutaneous adipose tissue (rSCA-MSC), ovarian adipose tissue (rOA-MSC), oviduct (rO-MSC), and mammary gland (rMG-MSC). The six rMSC lines showed plastic adhesion with fibroblast-like morphology and were all shown to be positive for CD44 and CD29 expression (characteristic markers of MSCs), and negative for CD34 or CD45 expression. In terms of pluripotency features, all rMSC lines expressed NANOG, OCT4, and SOX2. Furthermore, all rMSC lines cultured under osteogenic, chondrogenic, and adipogenic conditions showed differentiation capacity. In conclusion, this study describes the isolation and characterization of new rabbit cell lines from different tissue origins, with a clear mesenchymal pattern. We show that rMSC do not exhibit differences in terms of morphological features, expression of the cell surface, and intracellular markers of pluripotency and in vitro differentiation capacities, attributable to their tissue of origin.

Effects of Population Declines on Habitat Segregation and Activity Patterns of Rabbits and Hares in Doñana National Park, Spain

Competition, predation, and diseases are key factors shaping animal communities. In recent decades, lagomorphs in Europe have been impacted by virus-borne diseases that have caused substantial declines in their populations and, subsequently, in many of their predators. We examined activity and habitat-use patterns of sympatric European rabbits (Oryctolagus cuniculus L.) and Iberian hares (Lepus granatensis R.) in Doñana National Park, Spain, (DNP) during two periods of disease outbreak. In the first period (1984–1985), fecal pellet counts and roadside counts indicated that lagomorph species were segregated, with rabbits occurring in scrublands and hares in marshlands. Both species also occupied rush and fern belt ecotones. Roadside counts at sunrise, midday, sunset, and midnight revealed that rabbits and hares had the same activity patterns (crepuscular and nocturnal) in the zone of sympatry. During the second period (2005–2016), roadside counts showed that rabbits and hares were mainly nocturnal in scrublands and border marshlands. Hares occupied scrublands; a habitat previously occupied only by rabbits. These results are interpreted in light of the competition theory and predation pressure. The disease-caused decline of rabbits has likely favored hares that moved into scrublands, a vegetation type previously occupied exclusively by rabbits. The decline of rabbits in DNP has also caused the almost disappearance of this area of the Iberian lynx (Lynx pardinus), a rabbit specialist, thus enabling generalist predators to increase. Generalist predators have subsequently increased predation pressure on both rabbits and hares, causing them to switch to nocturnal activity.

Changes in European wild rabbit population dynamics and the epidemiology of rabbit haemorrhagic disease (RHD) in response to artificially increased viral transmission

European wild rabbit (Oryctolagus cuniculus) populations are severely affected by rabbit haemorrhagic disease (RHD), currently aggravated by the spread of the new lagovirus serotype RHDV2 that replaced the classical RHDV strains (RHDV/RHDVa). This virus causes high mortality in both adult and young rabbits and to date, there is no management tool to effectively reduce its impact in wild rabbit populations. This hinders the success of common strategies, such as habitat management or restocking, in areas where rabbits are native. However, the present study, conducted on enclosed wild rabbit populations, showed that spreading RHDV2 on baits during breeding periods induced infection of young rabbits, reducing mortality rates, presumably due to maternal antibody protection. This reduced the young rabbit mortality hazard by a third and more juvenile rabbits immune to RHDV2 were recruited into the adult breeding population. Young rabbits from populations in which the force of infection of RHDV2 was increased, however, exhibited considerably higher susceptibility to infection by RHDV than those from non-treated control populations. Since co-circulation of classical RHDVs was ruled out, differences in the type and degree of immunisation, the level of cross-protection and/or other unknown factors, such as the circulation of undetected non-pathogenic lagoviruses, arose as possible explanations. This meant that although the present work demonstrated the possibility of successfully modulating the impact of RHD in wild populations, the epidemiological complexity of the situation where several lagoviruses circulate requires additional research to determine final applicability of the proposed method. This article is protected by copyright. All rights reserved.

Reactivity of selected markers of innate and adaptive immunity in rabbits experimentally infected with antigenic variants of RHD (Lagovirus europaeus/GI.1a)

Lagovirus europaeus/GI.1 causes a fatal viral condition in rabbits characterized by acute viral hepatitis and disseminated intravascular coagulation. Due to rapid viral and environmental changes variants (Lagovirus europaeus/GI.1a and GI.2) have appeared and few immunological studies were performed. The aim of the study was to determine innate and adaptive immunity parameters in rabbits infected with six Lagovirus europeus/GI.1a viruses. To achieve the goal several methods were used, i.e. cytometry, microscopy, biochemical and cytochemical tests, spectrophotometry. The results show that three immunotypes exists among the studied strains and they differ in innate (mainly) and adaptive immunity, partly depending on hemagglutination. The peak of changes is 24 h post infection in phagocytosis markers of polymorphonuclear cells and CD8⁺ T cells. Lagovirus europaeus/GI.1a strains differ from Lagovirus europaeus/GI.1 in terms of immunological response based on our previous work concerning the same parameters in immunological response against this disease.

Lack of evidence for differences in the spread of classic (Lagovirus europaeus/GI.1) and novel (Lagovirus europaeus/GI.2) rabbit haemorrhagic disease viruses in Europe and North Africa

BACKGROUND

Fast-spreading diseases affecting wildlife populations threaten biodiversity. Two caliciviruses, Lagovirus europaeus/GI.1 and Lagovirus europaeus/GI.2, caused rabbit haemorrhagic disease virus (RHDV) in wild rabbits. Despite having different characteristics, these variants spread quickly, posing a threat to wild rabbit populations.

METHODS

In this study, we conducted a thorough review of the scientific literature and reports of international organisations of first detections of both variants of RHDV in the Euro-Mediterranean region. We concentrated on this area to avoid bias due to intentional human introductions.

RESULTS

The estimated mean spread rate of GI.2 was higher than that of GI.1 (GI.2: 479 km/year, range: 47-7346; GI.1: 330 km/year, 37-6248). These differences were not statistically significant. This lack of difference may be due to the interactions between each variant's virulence characteristics. Humans may have a dominant effect on their spread. Potential limitations associated with the observational process could have hindered our ability to identify statistical differences.

CONCLUSIONS

The lack of difference in the spread patterns of the two variants could be due to a biological cause, human facilitation or a lack of statistical power. Adapting protocols to detect diseases in wildlife using homogeneous criteria will be indispensable in the coming years.

First detected case of rabbit Haemorrhagic disease virus 2 (RHDV2) in the Irish hare (Lepus timidus hibernicus)

BACKGROUND

Rabbit haemorrhagic disease virus (RHDV) is a Lagovirus, a subgroup of the family Caliciviridae. RHDV2 is a variant first described in France in 2010, and has since spread globally. It has been reported in several Lagomorph species (rabbits, hares, and their relatives) as well as other mammals including voles and shrews. The disease has raised international concerns for its potential impact on population abundance trajectories, particularly as 25% of Lagomorphs are currently Red-Listed by the International Union for the Conservation of Nature (IUCN). The Irish hare (Lepus timidus hibernicus) is a subspecies of the mountain hare, L. timidus, and is endemic to Ireland, making it an Evolutionarily Significant Unit of intrinsic value.

CASE PRESENTATION

The first case of RHDV2 was detected in a wild Irish hare in July 2019. The individual exhibited atypical neurological behaviour (running in circles) prior to death. On necropsy, pink tinged foam was seen in the trachea and congestion was noted in the lungs, but there was no evidence of haemorrhages in any other organ. Both the liver and spleen were tested by reverse transcription real time qPCR confirming high levels of RHDV2 RNA. Histopathology confirmed multifocal necrotising hepatitis.

CONCLUSION

The Irish hare is susceptible to RHDV2 infection. Further investigation is warranted to explore the clinical, epidemiological, and population biology implications.

Early circulation of rabbit haemorrhagic disease virus type 2 in domestic and wild lagomorphs in southern California, USA (2020-2021)

Rabbit haemorrhagic disease virus type 2 (RHDV2) causes a severe systemic disease with hepatic necrosis. Differently from classic RHDV, which affects only European rabbits (Oryctolagus cuniculus), RHDV2 can affect many leporid species, including hares (Lepus spp.) and cottontail rabbits (Sylvilagus spp.). RHDV2 emerged in Europe in 2010 and spread worldwide. During the last 5 years, there have been multiple outbreaks in North America since the first known event in 2016 in Quebec, Canada, including several detections in British Columbia, Canada, between 2018 and 2019, Washington State and Ohio, USA, in 2018 and 2019, and New York, USA, in 2020. However, the most widespread outbreak commenced in March 2020 in the southwestern USA and Mexico. In California, RHDV2 spread widely across several southern counties between 2020 and 2021, and the aim of this study was to report and characterize these early events of viral incursion and circulation within the state. Domestic and wild lagomorphs (n = 81) collected between August 2020 and February 2021 in California with a suspicion of RHDV2 infection were tested by reverse transcription quantitative real-time PCR on the liver, and histology and immunohistochemistry for pan-lagovirus were performed on liver sections. In addition, whole genome sequencing from 12 cases was performed. During this period, 33/81 lagomorphs including 24/59 domestic rabbits (O. cuniculus), 3/16 desert cottontail rabbits (Sylvilagus audubonii), and 6/6 black-tailed jackrabbits (Lepus californicus) tested positive. All RHDV2-positive animals had hepatic necrosis typical of pathogenic lagovirus infection, and the antigen was detected in sections from individuals of the three species. The 12 California sequences were closely related (98.9%-99.95%) to each other, and also very similar (99.0%-99.4%) to sequences obtained in other southwestern states during the 2020-2021 outbreak; however, they were less similar to strains obtained in New York in 2020 (96.7%-96.9%) and Quebec in 2016 (92.4%-92.6%), suggesting that those events could be related to different viral incursions. The California sequences were more similar (98.6%-98.7%) to a strain collected in British Columbia in 2018, which suggests that that event could have been related to the 2020 outbreak in the southwestern USA.

Exploratory and territorial behavior in a reintroduced population of Iberian lynx

In reintroduction projects, an analysis of dispersal, exploratory movements and territorial behavior of the species concerned offers valuable information on the adaptive management of threatened species and provides a basis for the management of future reintroductions. This is the case of the Iberian lynx (Lynx pardinus) an endemic and endangered species reintroduced in Extremadura (Spain) in 2014. We analysed spatial data from 32 individuals just after their reintroduction. Our findings show exploratory movements sufficient to colonise and connect population nuclei within a radius of about 50 km of the reintroduction area. No significant differences were found in the exploratory movements capacity or in any directionality of males and females. Our results showed an effect of sex on the sizes of the territories established, as well as an inverse relationship between them and the time elapsed since release. No effects of rabbit abundance and lynx density on the size of territories are occurring during the early stages of reintroduction. On average, the territories of reintroduced individuals were less stable than those previously described in natural populations. Findings indicate that the reintroduced population has successfully been established but it takes more than 5 years to stabilize the territories in the area. Exploratory movements of reintroduced lynx can be large and in any direction, even when there is still a lot of high quality habitat available, which should be taken into account when reintroducing species, especially terrestrial carnivores.

Pathology of Lagovirus europaeus GI.2/RHDV2/b (Rabbit Hemorrhagic Disease Virus 2) in Native North American Lagomorphs

Rabbit hemorrhagic disease, a notifiable foreign animal disease in the US, was reported for the first time in wild native North American lagomorphs in April 2020 in the southwestern US. Affected species included the desert cottontail (Sylvilagus audubonii), mountain cottontail (Sylvilagus nuttallii), black-tailed jackrabbit (Lepus californicus), and antelope jackrabbit (Lepus alleni). Desert cottontails (n=7) and black-tailed jackrabbits (n=7) collected in April and May 2020 were necropsied at the US Geological Survey National Wildlife Health Center and tested positive for Lagovirus europaeus GI.2, also known as rabbit hemorrhagic disease virus 2 (GI.2/RHDV2/b), by real-time PCR at the US Department of Agriculture's Foreign Animal Disease Diagnostic Laboratory. Gross and microscopic lesions were similar to those reported in European rabbits (Oryctolagus cuniculus) and other hare (Lepus) species with GI.2/RHDV2/b infection; they included epistaxis (12/13; 92%); massive hepatocellular dissociation (14/14; 100%) and necrosis or apoptosis (11/11; 100%); pulmonary congestion (12/12; 100%), edema (12/13; 92%), and hemorrhage (11/12; 92%); and acute renal tubular injury (3/8; 38%). As in previous reports, massive hepatocellular dissociation and necrosis or apoptosis was the most diagnostically distinct finding. As North American Sylvilagus and Lepus species appear to be susceptible to fatal GI.2/RHDV2/b infection, additional work is needed to understand the host range, pathogenicity, and potential population effects of GI.2/RHDV2/b in North America.

Age and Infectious Dose Significantly Affect Disease Progression after RHDV2 Infection in Naïve Domestic Rabbits

Rabbit haemorrhagic disease virus 2 (RHDV2 or GI.2, referring to any virus with lagovirus GI.2 structural genes) is a recently emerged calicivirus that causes generalised hepatic necrosis and disseminated intravascular coagulation leading to death in susceptible lagomorphs (rabbits and hares). Previous studies investigating the virulence of RHDV2 have reported conflicting results, with case fatality rates ranging from 0% to 100% even within a single study. Lagoviruses are of particular importance in Australia and New Zealand where they are used as biocontrol agents to manage wild rabbit populations, which threaten over 300 native species and result in economic impacts in excess of $200 million AUD annually to Australian agricultural industries. It is critically important that any pest control method is both highly effective (i.e., virulent, in the context of viral biocontrols) and has minimal animal welfare impacts. To determine whether RHDV2 might be a suitable candidate biocontrol agent, we investigated the virulence and disease progression of a naturally occurring Australian recombinant RHDV2 in both 5-week-old and 11-week-old New Zealand White laboratory rabbits after either high or low dose oral infection. Objective measures of disease progression were recorded through continuous body temperature monitoring collars, continuous activity monitors, and twice daily observations. We observed a 100% case fatality rate in both infected kittens and adult rabbits after either high dose or low dose infection. Clinical signs of disease, such as pyrexia, weight loss, and reduced activity, were evident in the late stages of infection. Clinical disease, i.e., welfare impacts, were limited to the period after the onset of pyrexia, lasting on average 12 h and increasing in severity as disease progressed. These findings confirm the high virulence of this RHDV2 variant in naïve rabbits. While age and infectious dose significantly affected disease progression, the case fatality rate was consistently 100% under all conditions tested.

A Review on the Methods Used for the Detection and Diagnosis of Rabbit Hemorrhagic Disease Virus (RHDV)

Since the early 1980s, the European rabbit (Oryctolagus cuniculus) has been threatened by the rabbit hemorrhagic disease (RHD). The disease is caused by a lagovirus of the family Caliciviridae, the rabbit hemorrhagic disease virus (RHDV). The need for detection, identification and further characterization of RHDV led to the development of several diagnostic tests. Owing to the lack of an appropriate cell culture system for in vitro propagation of the virus, much of the methods involved in these tests contributed to our current knowledge on RHD and RHDV and to the development of vaccines to contain the disease. Here, we provide a comprehensive review of the RHDV diagnostic tests used since the first RHD outbreak and that include molecular, histological and serological techniques, ranging from simpler tests initially used, such as the hemagglutination test, to the more recent and sophisticated high-throughput sequencing, along with an overview of their potential and their limitations.

Immunity against Lagovirus europaeus and the Impact of the Immunological Studies on Vaccination

In the early 1980s, a highly contagious viral hemorrhagic fever in rabbits (Oryctolagus cuniculus) emerged, causing a very high rate of mortality in these animals. Since the initial occurrence of the rabbit hemorrhagic disease virus (RHDV), several hundred million rabbits have died after infection. The emergence of genetically-different virus variants (RHDV GI.1 and GI.2) indicated the very high variability of RHDV. Moreover, with these variants, the host range broadened to hare species (Lepus). The circulation of RHDV genotypes displays different virulences and a limited induction of cross-protective immunity. Interestingly, juvenile rabbits (<9 weeks of age) with an immature immune system display a general resistance to RHDV GI.1, and a limited resistance to RHDV GI.2 strains, whereas less than 3% of adult rabbits survive an infection by either RHDV GI.1. or GI.2. Several not-yet fully understood phenomena characterize the RHD. A very low infection dose followed by an extremely rapid viral replication could be simplified to the induction of a disseminated intravascular coagulopathy (DIC), a severe loss of lymphocytes—especially T-cells—and death within 36 to 72 h post infection. On the other hand, in animals surviving the infection or after vaccination, very high titers of RHDV-neutralizing antibodies were induced. Several studies have been conducted in order to deepen the knowledge about the virus’ genetics, epidemiology, RHDV-induced pathology, and the anti-RHDV immune responses of rabbits in order to understand the phenomenon of the juvenile resistance to this virus. Moreover, several approaches have been used to produce efficient vaccines in order to prevent an infection with RHDV. In this review, we discuss the current knowledge about anti-RHDV resistance and immunity, RHDV vaccination, and the further need to establish rationally-based RHDV vaccines.

Full-genome sequencing of German rabbit haemorrhagic disease virus uncovers recombination between RHDV (GI.2) and EBHSV (GII.1)

Rabbit haemorrhagic disease virus (RHDV; genotypes GI.1 and GI.2) and European brown hare syndrome virus (EBHSV; genotype GII.1) are caliciviruses belonging to the genus Lagovirus. These viruses pose a serious threat to wild and domestic rabbit and hare populations around the world. In recent years, an expanding genetic diversity has been described within the genus, with recombination events occurring between the different genotypes. Here, we generated and analysed 56 full-genome sequences of RHDV and EBHSV from rabbit and hare livers, collected in Germany between the years 2013 and 2020. We could show that genotype Gl.2 (RHDV-2) almost entirely replaced Gl.1 (classical RHDV) in the German rabbit population. However, GI.1 is still present in Germany and has to be included into disease control and vaccination strategies. Three recombinant strains were identified from rabbit samples that contain the structural genes of genotype Gl.2 and the non-structural genes of genotype Gl.1b. Of special interest is the finding that sequences from two hare samples showed recombination events between structural genes of RHDV Gl.2 and non-structural genes of EBHSV GII.1, a recombination between different genogroups that has not been described before. These findings lead to the assumption that also a recombination of the non-structural genes of RHDV Gl.2 with the structural genes of EBHSV Gll.1 might be possible and therefore increase the potential genetic variability of lagoviruses immensely. Our findings underline the importance of whole genome analysis with next-generation sequencing technology as one of new tools now available for in-depth studies that allow in depth molecular epidemiology with continuous monitoring of the genetic variability of viruses that would otherwise likely stay undetected if only routine diagnostic assays are used.

The paradox of endangered European rabbits regarded as pests on the Iberian Peninsula: trends in subspecies matter

The European rabbit Oryctolagus cuniculus faces a paradoxical situation in its native range on the Iberian Peninsula. While many populations have declined sharply due to a new variant of the rabbit haemorrhagic disease virus (RHDV-b), others remain healthy. The latter populations, which flourish mostly on farmland, cause significant crop damage. We explored if this difference could be related to the existence of the 2 rabbit subspecies (O. c. algirus and O. c. cuniculus) that coexist allopatrically on the Iberian Peninsula. Potential differences in population trends between rabbit subspecies may also be relevant in assisting the conservation of endangered rabbit-dependent predators which mainly occur in the distribution area of O. c. algirus. To test this, we assessed rabbit trends after the outbreak of RHDV-b by an online questionnaire to the senior administrative officers of all provincial official game departments throughout peninsular Spain (n = 47). A generalized negative trend was reported by officers in the distribution area of O. c. algirus, while a more stable or even positive trend was reported in the distribution area of O. c. cuniculus. We point to the need for establishing a long-term rabbit population monitoring programme on the Iberian Peninsula to further confirm the observed patterns, but also to contribute to evidence-based management decision-making. Our results suggest a need to apply different management systems for each rabbit subspecies.

Ecological traits and the spatial structure of competitive coexistence among carnivores

Competition is a widespread interaction among carnivores, ultimately manifested through one or more dimensions of the species' ecological niche. One of the most explicit manifestations of competitive interactions regards spatial displacement. Its interpretation under a theoretical context provides an important tool to deepen our understanding of biological systems and communities, but also for wildlife management and conservation. We used Bayesian multispecies occupancy models on camera-trapping data from multiple sites in Southwestern Europe (SWE) to investigate competitive interactions within a carnivore guild, and to evaluate how species' ecological traits are shaping coexistence patterns. Seventeen out of 26 pairwise interactions departed from a hypothesis of independent occurrence, with spatial association being twice as frequent as avoidance. Association behaviors were only detected among mesocarnivores, while avoidance mainly involved mesocarnivores avoiding the apex predator (n = 4) and mesocarnivore-only interactions (n = 2). Body mass ratios, defined as the dominant over the subordinate species body mass, revealed an important negative effect ( β ^ = - 0.38 ; C I 95 = - 0.81 t o - 0.06 ) on co-occurrence probability, and support that spatially explicit competitive interactions are mostly expressed by larger species able to dominate over smaller ones, with a threshold in body mass ratios of ~4, above which local-scale intraguild coexistence is unlikely. We found a weak relationship between pairwise trophic niche overlap and the probability of coexistence ( β ^ = - 0.19 ; C I 95 = - 0.58 t o 0.21 ), suggesting that competition for feeding resources may not be a key driver of competition, at least at the scale of our analysis. Despite local-scale avoidance, regional-scale coexistence appears to be maintained by the spatial structuring of the competitive environment. We provide evidence that SWE ecosystems consist of spatially structured competitive environments, and propose that coexistence among near-sized species is likely achieved through the interplay of "facultative" and "behavioral" character displacements. Factors influencing carnivore coexistence likely include context-dependent density and trait-mediated effects, which should be carefully considered for a sound understanding of the mechanisms regulating these communities.

Breaking barriers: Iberian Lynx Lynx pardinus Temminck, 1827 (Mammalia: Carnivora: Felidae) colonizing Olive groves

In recent years, the Andújar-Cardeña Iberian Lynx Lynx pardinus population has grown both in number and in occupied surface area.  This feline has spread into areas surrounding existing population nuclei and occupied new habitats including human-dominated areas and tree crops.  Here we describe this colonization process and the evolution of the Iberian Lynx populations in the Olive Olea europaea groves that surround typical Lynx scrub habitats in Andújar-Cardeña.  Our findings were obtained through radio-tracking, camera trapping and European Rabbit Oryctolagus cuniculus monitoring.  Two colonized areas—Zocueca and Marmolejo-Montoro—were identified in which Olive cultivation is predominant.  Since 2011, a total of 45 and 50 different individuals have been detected in Zocueca and Marmolejo-Montoro, respectively.  At present, 19 individuals are known to live in Zocueca and 29 in Marmolejo-Montoro.  The main cause of mortality is road-kills.  Our results suggest that the Iberian Lynx is capable of colonizing human-modified areas such as agricultural land provided that they can support high-density Rabbit populations and the causes of non-natural mortality are minimized.

Planning the peninsula-wide recovery of the Iberian lynx: identification of favourable habitat areas

The creation of new populations through reintroductions in their former range is still necessary for the long-term conservation of the Iberian lynx (Lynx pardinus). A large-scale assessment of habitat suitability is a necessary prerequisite for evaluating the possibility of carrying out lynx reintroductions. We modelled habitat suitability for the Iberian lynx in the Iberian Peninsula using MaxEnt. Lynx presence data for 2010–2013 from Andujar-Cardeña and Doñana populations were used. Habitat variables were quantified using the CORINE Land Cover. This habitat suitability model predicted an environmentally suitable area of 87,747 km2, which represents 14.08% of the whole Iberian Peninsula. Of the total suitable habitat identified, 45% is located in a large continuous area in the south-western quadrant coinciding with the historical range of the species in the mid-20th century. However, there are also relevant patches mainly in the north-eastern quadrant. About 55% of the potential area suitable for the lynx falls outside protected areas. If Iberian lynx populations are to attain levels that will facilitate their long-term survival, it will be necessary to consider potential habitat for the species throughout the whole of the Iberian Peninsula.

An Ecosystems Perspective on Virus Evolution and Emergence

Understanding the emergence of pathogenic viruses has dominated studies of virus evolution. However, new metagenomic studies imply that relatively few of an immense number of viruses may lead to overt disease. This suggests a change in emphasis, from viruses as habitual pathogens to integral components of ecosystems. Here we show how viruses alter interactions between host individuals, populations, and ecosystems, impacting ecosystem health, resilience, and function, and how host ecology in turn impacts viral abundance and diversity. Moving to an ecosystems perspective will put virus evolution and disease emergence in its true context, and enhance our understanding of ecological processes.

Monitoring of the novel rabbit haemorrhagic disease virus type 2 (GI.2) epidemic in European wild rabbits (Oryctolagus cuniculus) in southern Spain, 2013-2017

Rabbit hemorrhagic disease (RHD) is a highly infectious disease in European rabbits (Oryctolagus cuniculus), caused by a virus belonging to the genus Lagovirus (RHDV; family Caliciviridae). In 2010, a new genotype of RHDV (RHDV2 or RHDVb, currently designated GI.2) emerged in France, affecting both domestic rabbits, even those vaccinated for the classical RHDV genotypes (currently designated GI.1) and wild rabbits. GI.2 was subsequently identified in other European countries. The aim of the present study was to monitor the GI.2 epidemic in wild rabbits in Andalusia (southern Spain) during the period 2013-2017. At the beginning of summer 2013, high mortalities were detected in wild rabbit populations in southern Spain. A total of 96 affected hunting or protected areas were surveyed. The first outbreak was observed on June 2013. The number of outbreaks sharply increased in 2013 and 2014, with a decreasing trend being observed during the following years. The spatial distribution of GI.2 was not homogeneous, since most of the detected outbreaks were concentrated in the western part of Andalusia. The outbreaks peaked in winter and spring and have been detected in the last five consecutive years, which suggests endemic circulation of GI.2 in wild rabbit populations in Spain. A total of 190 dead rabbits from 87 of the 96 areas surveyed were collected during the study period. Mortality affected rabbits of different age classes, including kittens. RT-PCR confirmed the presence of GI.2 RNA in the livers of 185 of the 190 (97.4%) rabbits. Phylogenetic analysis performed on eleven samples collected in different provinces of Andalusia between 2013 and 2017, showed high nucleotide identity with GI.2 strains Spain, France and Portugal. The results constitute an important step in understanding of the emergence and spread of GI.2 in this country and will provide valuable information for the development of surveillance programs in Europe.

Lynx eats cat: disease risk assessment during an Iberian lynx intraguild predation

Lethal interactions between members of the carnivore guild are well represented in literature. In the Iberian lynx, interspecific killing (without prey consumption) of some mesocarnivores, such as the Egyptian mongoose, genet, and red fox, has been reported. Although vaguely documented, evidence suggests feral cats fall victim to interactions with this apex predator. Here, we describe the first documented case of interspecific killing and partial consumption of a feral cat by an adult male Iberian lynx reintroduced in Southwestern Spain. Ulterior analyses demonstrated that the victim was viremic to feline leukemia virus. To prevent the dissemination of the virus and a potential outbreak in the Iberian lynx population, control measures, including the clinical evaluation of the male Iberian lynx, and intensive monitoring were implemented in order to detect intraspecific interactions. After 3 weeks, the lynx was evaluated, presented good condition and resulted negative to both ELISA and RT-PCR. Thanks to the long-term monitoring, this case could be detected and measures to prevent an outbreak could be implemented.

Worldwide rapid spread of the novel rabbit haemorrhagic disease virus (GI.2/RHDV2/b)

We describe the extremely rapid worldwide spread of the Lagovirus europaeus/GI.2/RHDV2/b (henceforth GI.2), the causative infectious agent of the so-called 'novel' rabbit haemorrhagic disease of the European rabbit (Oryctolagus cuniculus). We tracked down all novel confirmed detections of GI.2 between May 2010 and November 2018 by carrying out a two-step in-depth review. We suggest that such spread would not have been possible without anthropogenic involvement. Our results also point out the importance of reviewing and adapting the protocols of virus detection and management in order to control, mitigate and contain properly, not only GI.2, but also new viruses that may emerge in the future.

Females know better: Sex-biased habitat selection by the European wildcat

The interactions between animals and their environment vary across species, regions, but also with gender. Sex-specific relations between individuals and the ecosystem may entail different behavioral choices and be expressed through different patterns of habitat use. Regardless, only rarely sex-specific traits are addressed in ecological modeling approaches. The European wildcat (Felis silvestris silvestris) is a species of conservation concern in Europe, with a highly fragmented and declining distribution across most of its range. We assessed sex-specific habitat selection patterns for the European wildcat, at the landscape and home range levels, across its Iberian biogeographic distribution using a multipopulation approach. We developed resource selection functions in a use-availability framework using radio-telemetry data from five wildcat populations. At the landscape level, we observed that, while both genders preferentially established home ranges in areas close to broadleaf forests and far from humanized areas, females selected mid-range elevation areas with some topographic complexity, whereas males used lowland areas. At the home range level, both females and males selected areas dominated by scrublands or broadleaf forests, but habitat features were less important at this level. The strength of association to habitat features was higher for females at both spatial levels, suggesting a tendency to select habitats with higher quality that can grant them enhanced access to shelter and feeding resources. Based on our results, we hypothesize that sex-biased behavioral patterns may contribute to the resilience of wildcats' genetic integrity through influencing the directionality of hybridization with domestic cats. Our study provides information about European wildcats' habitat use in an Iberian context, relevant for the implementation of conservation plans, and highlights the ecological relevance of considering sex-related differences in environmental preferences.

Elucidation of the pathology and tissue distribution of Lagovirus europaeus GI.2/RHDV2 (rabbit haemorrhagic disease virus 2) in young and adult rabbits (Oryctolagus cuniculus)

Lagovirus europaeus GI.2, also known as RHDV2 or RHDVb, is an emerging virus that causes rabbit haemorrhagic disease (RHD) in European rabbits (Oryctolagus cuniculus). In contrast to L. europaeus GI.1 (or RHDV/RHDVa) viruses that are only pathogenic for adults, GI.2 causes clinical disease in both adults and kittens. However, detailed descriptions of the pathology of this virus that may provide insight into its pathogenicity and emergence are lacking. Using an Australian GI.2 field strain isolated in 2015, we provide the first detailed description of pathology, viral antigen distribution and tissue load of GI.2 in adult and 5-week old New Zealand white rabbits using histology, immunohistochemistry and RT-qPCR. Liver was the target organ, but in contrast to GI.1 viruses, lesions and inflammatory responses did not differ between adults and kittens. Lymphocytic inflammation, proposed to be protective in kittens infected with GI.1, was notably absent. We also present the first descriptions of bone marrow changes in RHD, including decreased myeloid-to-erythroid ratio. Consistent with other pathogenic lagoviruses, intracellular viral antigen was demonstrated in hepatocytes and cells of the mononuclear phagocytic system. In terminal stages of disease, viral loads were highest in liver, serum and spleen. Despite the small sample size, our data suggest that unlike early European GI.2 strains, the pathogenicity of the Australian GI.2 virus is similar to GI.1 viruses. Additionally, GI.2 was fatal for all (n = 5) inoculated kittens in this study. This may significantly alter RHD epidemiology in the field, and may impact biocontrol programs for invasive rabbits in Australia where GI.1 viruses are intentionally released.

Substantial numerical decline in South Australian rabbit populations following the detection of rabbit haemorrhagic disease virus 2

Lagovirus europaeus GI.2, also commonly known as rabbit haemorrhagic disease virus 2, was first detected at two long-term monitoring sites for European rabbits, Oryctolagus cuniculus, in South Australia, in mid-2016. Numbers of rabbits in the following 12-18 months were reduced to approximately 20 per cent of average numbers in the preceding 10 years. The impact recorded at the two South Australian sites, if widespread in Australia and persistent for several years, is likely to be of enormous economic and environmental benefit.

A large-scale assessment of European rabbit damage to agriculture in Spain

BACKGROUND

Numerous small and medium-sized mammal pests cause widespread and economically significant damage to crops all over the globe. However, most research on pest species has focused on accounts of the level of damage. There are fewer studies concentrating on the description of crop damage caused by pests at large geographical scales, or on analysis of the ecological and anthropogenic factors correlated with these observed patterns. We investigated the relationship between agricultural damage by the European rabbit (Oryctolagus cuniculus) and environmental and anthropogenic variables throughout Spain.

RESULTS

Rabbit damage was mainly concentrated within the central-southern regions of Spain. We found that rabbit damage increased significantly between the early 2000s and 2013. Greater losses were typical of those areas where farming dominated and natural vegetation was scarce, where main railways and highways were present, and where environmental conditions were generally favourable for rabbit populations to proliferate.

CONCLUSION

From our analysis, we suggest that roads and railway lines act as potential corridors along which rabbits can spread. The recent increase in Spain of such infrastructure may explain the rise in rabbit damage reported in this study. Our approach is valuable as a method for assessing drivers of wildlife pest damage at large spatial scales, and can be used to propose methods to reduce human - wildlife conflict. © 2017 Society of Chemical Industry.

Conventional and real time RT-PCR assays for the detection and differentiation of variant rabbit hemorrhagic disease virus (RHDVb) and its recombinants

Since its emergence, variant RHDV (RHDVb/RHDV2) has spread throughout the Iberian Peninsula aided by the apparent lack of cross protection provided by classic (genogroup 1; G1) strain derived vaccines. In addition to RHDVb, full-length genome sequencing of RHDV strains has recently revealed the circulation of recombinant viruses on the Iberian Peninsula. These recombinant viruses contain the RHDVb structural protein encoding sequences and the non-structural coding regions of either pathogenic RHDV-G1 strains or non-pathogenic (np) rabbit caliciviruses. The aim of the work was twofold: firstly to validate a diagnostic real time RT-PCR developed in 2012 for the detection of RHDVb strains and secondly, to design a conventional RT-PCR for the differentiation of RHDVb strains from RHDVb recombinants by subsequent sequencing of the amplicon.