Spatial and Temporal Phylogeny of Border Disease Virus in Pyrenean Chamois (Rupicapra p. pyrenaica)

New Potential Role of European Mouflon (Ovis aries musimon) in the Epidemiology of Border Disease in the Pyrenees

Since 2001, high-mortality outbreaks of border disease (BD) have negatively affected populations of Pyrenean chamois (Rupicapra pyrenaica pyrenaica). Studies in the affected areas determined that sympatric wild ruminants did not seem to have an epidemiologic role in the circulation of border disease virus (BDV). However, the recent increase in European mouflon (Ovis aries musimon) densities might enhance the risk of pathogen transmission among chamois and mouflons. We conducted a serologic and virologic investigation of BDV in European mouflon from the Spanish Pyrenees, with the aim of determining potential changes in the role of this species in BDV epidemiology. From 2018 to 2022, we detected antibodies against BDV in 31/185 (16.7%) animals but did not detect BDV RNA in any spleen sample (0/65). These results indicate that BDV infection is occurring in these mouflon populations to a greater extent than previously described, which could shift the current understanding of BD epidemiology in the Pyrenees and cause an unpredictable effect on both chamois and mouflon populations. Further studies on the molecular identification of BDV in mouflon and chamois are required to better understand the contribution of mouflon in the epidemiology of BD.

Circulation of Pestiviruses in Small Ruminants from Greece: First Molecular Identification of Border Disease Virus

The incidence of small ruminant pestivirus infections in Greece remains unknown as they have not been diagnosed in the country since 1974 when the most recent Border Disease Virus (BDV) outbreak was reported. The objective of our study was to explore the possible occurrence of pestiviral infections among sheep and goat farms in Greece and to further determine the variants of major concern. Thus, serum samples were collected from 470 randomly selected animals belonging to 28 different flocks/herds. ELISA on p80 antibody revealed the existence of seropositive animals in four out of the 24 studied sheep flocks, whereas all the goats in the four studied herds were seronegative. Viral RNA and antigens were detected in two sheep out of the four seropositive flocks by RT-PCR and ELISA, respectively. Sequencing and phylogenetic analysis showed that the newly identified Greek variants were closely related to the strains of the BDV-4 genotype. One of the BDV-positive sheep demonstrated the diagnostic profile of a persistently infected (PI) animal, providing additional information regarding the source of the infection. This is the first molecular identification of BDV isolates in Greece. Our findings indicate that BDV infections are likely to remain undiagnosed, highlighting the need for further epidemiological studies and active surveillance programs to determine the prevalence and impact of BDV infections on a countrywide level.

Genetic diversity of Bovine Viral Diarrhea Virus in cattle in France between 2018 and 2020

Bovine Viral Diarrhea Virus (BVDV) is one of the main pathogens that affects ruminants worldwide, generating significant economic losses. Like other RNA viruses, BVDV is characterized by a high genetic variability, generating the emergence of new variants, and increasing the risk of new outbreaks. The last report on BVDV genotypes in France was in 2008, since which there have been no new information. The goal of this study is to determine the genetic diversity of BVDV strains currently circulating in France. To this aim, samples of cattle were taken from different departments that are part of the main areas of livestock production during the years 2018 to 2020. Using the partial sequence of the 5'UTR region of the viral genome, we identified and classified 145 samples corresponding to Pestivirus A and one sample corresponding to Pestivirus D. For the Pestivirus A samples, the 1e, 1b, 1d, and 1l genotypes, previously described in France, were identified. Next, the 1r and 1s genotypes, not previously described in the country, were detected. In addition, a new genotype was identified and was tentatively assigned as 1x genotype. These results indicate an increase in the genetic diversity of BVDV in France.

Epidemiology of Bovine Pestiviruses Circulating in Italy

Pestiviruses are widespread and economically important pathogens of cattle and other animals. Pestivirus A (formerly known as Bovine viral diarrhea virus 1, BVDV-1), Pestivirus B (Bovine viral diarrhea virus 2, BVDV-2), and Pestivirus H (HoBi-like pestivirus, HoBiPeV) species are infecting primarily cattle. Like other RNA viruses, pestiviruses are characterized by a high degree of genetic variability. This high rate of variability is revealed by the existence of a number of viral subgenotypes within each species. In cattle, the highest number of pestivirus subgenotypes has been documented in European countries, particularly in Italy. The aim of this review is to report an up-to-date overview about the genetic diversity of pestiviruses in Italian cattle herds. All three bovine pestiviruses species have been identified in cattle population with variable frequency and geographical distribution. The genetic diversity of Italian pestiviral strains may have diagnostic and immunological implications, affecting the performance of diagnostic tools and the full cross-protection elicited by commercially available vaccines. Implementation and strengthening of coordinated approaches for bovine pestivirus control in Italy are recommended. Therefore, it would be extremely important to increase control and restriction measures to the trade of cattle and biological products of bovine origin, including those containing fetal bovine serum.

Global Distribution and Genetic Heterogeneity of Border Disease Virus

Border disease virus (BDV) belongs to the genus Pestivirus of the family Flaviviridae. Interspecies transmission of BDV between sheep, cattle, and pigs occurs regularly, sometimes making diagnosis a challenge. BDV can yield substantial economic losses, including prenatal and postnatal infections in lambs, which are the primary source of infection and maintenance of the virus in the population. Since BDV is antigenically and genetically related to bovine viral diarrhea virus (BVDV), it might pose a significant risk to cattle, influencing BVDV eradication campaigns. Similarly, the presence of BDV in swine herds due to pestivirus spillover between small ruminants and pigs might cause uncertainty in classical swine fever virus (CSFV) diagnostics. Therefore, knowledge of BDV epidemiology in different geographical regions will help prevent its spread and optimize control measures. Previous epidemiological studies have shown that various BDV genotypes are predominant in different countries. This review provides an overview of the spread of BDV world-wide in different host species.

Evolution and genetic diversity of atypical porcine pestivirus (APPV) from piglets with congenital tremor in Guangxi Province, Southern China

Atypical porcine pestivirus (APPV) was identified and associated with congenital tremor (CT) type A‐II in new born piglets and has been reported in many countries. In China, the first APPV identification in swine herds was reported in Guangdong province in 2016. To investigate the genetic characteristics of APPV in Guangxi province, 53 tissue samples from neonatal piglets with CT were collected and detected from October 2017 to May 2019. Five APPV strains which were named as GX04/2017, GX01‐2018, GX02‐2018, GX01‐2019 and GX02‐2019 were obtained. Sequence analysis revealed that all six APPV strains from Guangxi province, including five strains from this study and one from a previous report, shared 83.3%‐97.5% nucleotide identity of complete genome and 91.7%‐99.1% amino acid identity of the open reading frame (ORF), and shared 77.7%‐97.7% nucleotide identity of complete genome and 90.6%‐99.3% amino acid identity of ORF with reference strains. Phylogenetic analysis indicated that all APPV strains could be divided into three clades based on the complete genome, N^pro, E^rns and E2 gene sequences, respectively; and the APPV strains from Guangxi province distributed in two clades (clades I and II). No sign of recombination was observed from Guangxi strains. Evolution analysis performed on the complete genome of 58 APPV strains showed that America, Europe and Asia strains during 2006–2019 evolved at a mean rate of 1.37 × 10^–4 substitutions/site/year, and the most recent common ancestor (tMRCA) of them was estimated as 1,700.5 years ago. The findings of this study indicated that there existed a high degree of genetic diversity of APPV from Guangxi province, Southern China, which provided important information on the epidemiological features and evolutionary relationships of APPV.

Distribution of Pestivirus exposure in wild ruminants in Spain

A large-scale study was carried out to determine the prevalence of antibodies against Pestivirus species in wild ruminants and describe their spatial variation in mainland Spain. Serum samples of 1,874 wild ruminants from different regions of this country were collected between the years 2000 and 2017. A total of 6.6% (123/1,874) animals showed antibodies against Pestivirus by both blocking ELISA (bELISA) and virus neutralization tests (VNT). The prevalence of antibodies against pestiviruses was different both among species and regions. Seroprevalence by species was 30.0% (75/250) in Southern chamois (Rupicapra pyrenaica), 7.0% (25/357) in fallow deer (Dama dama), 2.5% (10/401) in red deer (Cervus elaphus), 2.4% (8/330) in Iberian wild goat (Capra pyrenaica), 1.1% (4/369) in roe deer (Capreolus capreolus) and 0.8% (1/130) in mouflon (Ovis aries musimon), not detecting seropositivity (0/37) in Barbary sheep (Ammotragus lervia). The results confirm that exposure to pestiviruses was detected throughout mainland Spain, with significantly higher seroprevalence in Northern regions associated with the presence of Southern chamois. This indicates an endemic circulation of pestiviruses in Southern chamois and a limited circulation of these viruses in the remaining wild ruminant species during the last two decades, thus suggesting that non-chamois species are not true Pestivirus reservoirs in Spain. Nonetheless, the high spatial spread of these viruses points out that new epidemic outbreaks in naïve wild ruminant populations or transmission to livestock may occur, evidencing the usefulness of monitoring pestiviruses in wild ruminants, especially at the wildlife-livestock interface.

Sarcoptic Mange in Wild Caprinae of the Alps: Could Pathology Help in Filling the Gaps in Knowledge?

Sarcoptic mange represents the most severe disease for wild Caprinae individuals and populations in Europe, raising concerns for both conservation and management of these ungulates. To date, this disease has been investigated in different wild caprine species and under many different perspectives including diagnostics, epidemiology, impact on the host populations, and genetics of both hosts and parasite, with the aim to disentangle the host-Sarcoptes scabiei relationship. Notwithstanding, uncertainty remains and basic questions still need an answer. Among these are the effect of immune responses on mange severity at an individual level, the main drivers in host-parasite interactions for different clinical outcomes, and the role of the immune response in determining the shift from epidemic to endemic cycle. A deeper approach to the pathology of this disease seems therefore advisable, all the more reason considering that immune response to S. scabiei in wild Caprinae, generally classified as a hypersensitivity, remains poorly understood. In this paper, we reviewed the pathological features associated to sarcoptic mange in wildlife, exploring different kinds of hypersensitivity and outcomes, with the objective of highlighting the major drivers in the different responses to this disease at an individual level and proposing some key topics for future research, with a particular attention to Alps-dwelling wild caprines.

Sanitary Emergencies at the Wild/Domestic Caprines Interface in Europe

Simple Summary

Even if it is an important achievement from a biodiversity conservation perspective, the documented increase in abundance of the four native European wild Caprinae (Rupicapra rupicapra, R. pyrenaica, Capra ibex, C. pyrenaica) can also be a matter of concern, since tighter and more frequent contact with sympatric livestock implies a greater risk of transmission of emerging and re-emerging pathogens. This article reviews the main transmissible diseases that, in a European scenario, are of greater significance from a conservation perspective. Epidemics causing major demographic downturns in wild Caprinae populations during recent decades were often triggered by pathogens transmitted at the livestock/wildlife interface.

Abstract

Population density and distribution of the four native European wild Caprines (Rupicapra rupicapra, Rupicapra pyrenaica, Capra ibex, Capra pyrenaica) have increased in recent decades. The improved conservation status of this valuable wildlife, while a welcome event in general terms, is at the same time a matter of concern since, intuitively, frequent and tighter contacts with sympatric livestock imply a greater risk of cross-transmission of emerging and re-emerging pathogens, and offer unexpected opportunities for pathogens to spread, persist and evolve. This article recalls the transmissible diseases that are perceived in Europe to be of major significance from a conservation perspective, namely brucellosis (BRC) by Brucella melitensis, infectious kerato-conjunctivitis (IKC) by Mycoplasma conjunctivae, pestivirosis (PV) by the border disease virus strain 4 and mange by Sarcoptes scabiei. Special emphasis has been put on the epidemiological role played by small domestic ruminants, and on key knowledge needed to implement evidence-based prevention and control strategies. Remarkably, scientific evidence demonstrates that major demographic downturns in affected wild Caprinae populations in recent decades have often been triggered by pathogens cross-transmitted at the livestock/wildlife interface.

Characterization of internal ribosome entry sites according to secondary structure analysis to classify border disease virus strains

Applying palindromic nucleotide substitutions (PNS) method, variable loci of the internal ribosome entry site (IRES) secondary structure in the 5' untranslated region (UTR) of Border disease virus sequences were analysed allowing their allocation into ten IRES classes within the species. Sequence characteristics of Turkish and Chinese strains were highly divergent from other genogroups, indicating geographic segregation and micro-evolutive steps within the species. Observed heterogeneity in the BDV species has to be considered for potential implications on diagnostic tests, control and preventive measures.

First report of border disease virus in Melophagus ovinus (sheep ked) collected in Xinjiang, China

Melophagus ovinus (sheep ked) is a blood-sucking ectoparasite that is parasitic primarily on sheep. It is widely distributed in different geographical regions worldwide. In China, it has been mainly found in Xinjiang, Gansu, and Tibet in recent years. In addition to causing direct damage to the animal hosts, M. ovinus also carries pathogens and serves as a vector for disease transmission. Border disease virus (BDV) is a positive-sense, single-stranded RNA pestivirus that mainly infects and causes border disease (BD) in sheep and goats worldwide. Since 2012, this disease has been reported in 4 provinces in China. In the present study, we investigated the presence of BDV in M. ovinus from Xinjiang and Gansu. Frozen M. ovinus collected during 2017 and 2018 from Xinjiang and Gansu and preserved in our laboratory were studied. First, total RNA of M. ovinus was extracted, followed by reverse transcription, PCR (RT-PCR) amplification of the 5′-UTR of BDV, and sequencing of the amplified products. Finally, the sequencing results were analyzed using DNAStar, MEGA 5.0 molecular biology software, and the BLAST online platform. The results from RT-PCR and sequencing analyses showed that among the samples included in the study, only the M. ovinus collected from Qinghe County in Alta, Xinjiang in 2018 tested positive for BDV. BLAST analysis showed that the viral strain with the most similar nucleotide identity to the sequence of the China/BDV/2018 fragment was the goat-derived BDV strain AH12-02 collected in Anhui, China, in 2012. A phylogenetic-tree analysis showed the strain to exhibit a BDV-3 genotype. This is the first report globally on BDV detected in M. ovinus and is also the first report of BDV discovered in Xinjiang, China. This study reconfirms the presence of BDV in China.

Histological and virological findings in severe meningoencephalitis associated with border disease virus in Alpine chamois (Rupicapra rupicapra rupicapra) in Aosta Valley, Italy

In 2015, a young female Alpine chamois (Rupicapra rupicapra rupicapra), originated from the Aosta Valley Region, Northernwestern Italy, was conferred to the National Reference Centre for Wild Animal Diseases for pathologic examinations. Histological analysis revealed a severe meningoencephalitis characterized by lymphocytic and plasmacellular infiltration, gliosis, perivascular cuffs, and leptomeningitis at the level of brain and brain stem. Laboratory investigations included polymerase chain reaction, sequencing and characterization by phylogenetic analysis, and evaluation of the internal ribosome entry site secondary structure in the 5’ untranslated region. These tests identified the pathological agent as border disease virus, a known health risk in domestic small ruminants. Genetic characteristics of the isolated strains, closely related to ovine and caprine strain sequences from neighboring regions of Piedmont, France, and Switzerland, suggested geographic segregation and micro-evolutive steps within the species.

Experimental infection with high- and low-virulence strains of border disease virus (BDV) in Pyrenean chamois (Rupicapra p. pyrenaica) sheds light on the epidemiological diversity of the disease

Since 2001, Pyrenean chamois (Rupicapra pyrenaica pyrenaica) populations have been affected by border disease virus (BDV) causing mortalities of more than 80% in some areas. Field studies carried out in France, Andorra, and Spain have shown different epidemiological scenarios in chamois populations. This study was designed to confirm the presence of BDV strains of a high and low virulence in free-ranging chamois populations from Pyrenees and to understand the implications of these findings to the diverse epidemiological scenarios. An experimental infection of Pyrenean chamois with a high-virulence (Cadí-6) and low-virulence (Freser-5) BDV strains was performed. Pregnant and non-pregnant animals with and without antibodies against BDV were included in each group. Cadí-6 BDV strain was confirmed to be of high virulence for seronegative adults and their foetuses. The antibody negative chamois infected with Freser-5 BDV strain did not show symptoms, presented less viral distribution and RNA load in tissues than Cadí-6 group, and cleared the virus from the serum. However, foetuses died before the end of the experiment and RNA virus was detected in sera and tissues although with lower RNA load than the Cadí-6 group. Chamois from both groups presented lesions in brain but the ones infected with the low-virulence Freser-5 BDV strain were mild and most likely transient. In both groups, seropositive pregnant females and all but one of their foetuses did not present viraemia or viral RNA in tissues. The existence of a low-virulence strain has been confirmed experimentally and related to chamois population infection dynamics in the area where it was isolated. Such strain may persist in the chamois population through PI animals and may induce cross-protection in chamois against high-virulence strains. This study demonstrates that viral strain diversity is a significant factor in the heterogeneity of epidemiological scenarios in Pyrenean chamois populations.

Border disease in cattle

Within the family Flaviviridae, viruses within the genus Pestivirus, such as Border disease virus (BDV) of sheep, can cause great economic losses in farm animals. Originally, the taxonomic classification of pestiviruses was based on the host species they were isolated from, but today, it is known that many pestiviruses exhibit a broad species tropism. This review provides an overview of BDV infection in cattle. The clinical, hematological and pathological-anatomical findings in bovines that were transiently or persistently infected with BDV largely resemble those in cattle infected with the closely related pestivirus bovine viral diarrhoea virus (BVDV). Accordingly, the diagnosis of BDV infection can be challenging, as it must be differentiated from various pestiviruses in cattle. The latter is very relevant in countries with control programs to eradicate BVDV in Bovidae, as in most circumstances, pestivirus infections in sheep, which act as reservoir for BDV, are not included in the eradication scheme. Interspecies transmission of BDV between sheep and cattle occurs regularly, but BDV in cattle appears to be of minor general importance. Nevertheless, BDV outbreaks at farm or local level can be very costly.

Demographic stochasticity drives epidemiological patterns in wildlife with implications for diseases and population management

Infectious diseases raise many concerns for wildlife and new insights must be gained to manage infected populations. Wild ungulates provide opportunities to gain such insights as they host many pathogens. Using modelling and data collected from an intensively monitored population of Pyrenean chamois, we investigated the role of stochastic processes in governing epidemiological patterns of pestivirus spread in both protected and hunted populations. We showed that demographic stochasticity led to three epidemiological outcomes: early infection fade-out, epidemic outbreaks with population collapse, either followed by virus extinction or by endemic situations. Without re-introduction, the virus faded out in >50% of replications within 4 years and did not persist >20 years. Test-and-cull of infected animals and vaccination had limited effects relative to the efforts devoted, especially in hunted populations in which only quota reduction somewhat improve population recovery. Success of these strategies also relied on the maintenance of a high level of surveillance of hunter-harvested animals. Our findings suggested that, while surveillance and maintenance of population levels at intermediate densities to avoid large epidemics are useful at any time, a 'do nothing' approach during epidemics could be the 'least bad' management strategy in populations of ungulates species facing pestivirus infection.

Self-clearance of Pestivirus in a Pyrenean Chamois ( Rupicapra pyrenaica) Population

Understanding the dynamics of host-pathogen interaction is key to the management of epidemics. A pestivirus belonging to the border disease virus group 4 emerged around 2001 in Pyrenean chamois ( Rupicapra pyrenaica) in Spain and France. The virus had significant demographic impact in some populations, but it was less harmful and more endemic in other places. The determinants of these local variations are still unclear. Here, we documented empirical evidence of self-clearance of the virus in a chamois population in France. This population has regularly been counted, and chamois were trapped and harvested each year, providing unique demographic and epidemiologic surveys of the population since 1984 and 1994, respectively. The virus was detected using direct (PCR) and indirect (antibody) testing. We showed that virus transmission declined in 2011-12 and likely ceased in 2013, leading to a decline in antibody prevalence since 2014. Self-clearance may be due to limited exchanges with other populations, decrease in population size after an epizootic, and herd immunity. The age structure of captured animals shifted to younger age classes after virus self-clearance, suggesting a return to a colonizing population structure. The possible consequences of virus re-entry are discussed. This observation suggests that pestivirus dynamics occurs at the scale of the metapopulation of Pyrenean chamois. Local self-clearance and re-emergence may help explain the variation of virus dynamics at the local scale.

Long-term dynamics of Mycoplasma conjunctivae at the wildlife-livestock interface in the Pyrenees

Functional roles of domestic and wild host populations in infectious keratoconjunctivitis (IKC) epidemiology have been extensively discussed claiming a domestic reservoir for the more susceptible wild hosts, however, based on limited data. With the aim to better assess IKC epidemiology in complex host-pathogen alpine systems, the long-term infectious dynamics and molecular epidemiology of Mycoplasma conjunctivae was investigated in all host populations from six study areas in the Pyrenees and one in the Cantabrian Mountains (Northern Spain). Detection of M. conjunctivae was performed by qPCR on 3600 eye swabs collected during seven years from hunted wild ungulates and sympatric domestic sheep (n = 1800 animals), and cluster analyses of the strains were performed including previous reported local strains. Mycoplasma conjunctivae was consistently detected in three Pyrenean chamois (Rupicapra p. pyrenaica) populations, as well as in sheep flocks (17.0% of sheep) and occasionally in mouflon (Ovis aries musimon) from the Pyrenees (22.2% in one year/area); statistically associated with ocular clinical signs only in chamois. Chamois populations showed different infection dynamics with low but steady prevalence (4.9%) and significant yearly fluctuations (0.0%– 40.0%). Persistence of specific M. conjunctivae strain clusters in wild host populations is demonstrated for six and nine years. Cross-species transmission between chamois and sheep and chamois and mouflon were also sporadically evidenced. Overall, independent M. conjunctivae sylvatic and domestic cycles occurred at the wildlife-livestock interface in the alpine ecosystems from the Pyrenees with sheep and chamois as the key host species for each cycle, and mouflon as a spill-over host. Host population characteristics and M. conjunctivae strains resulted in different epidemiological scenarios in chamois, ranging from the fading out of the mycoplasma to the epidemic and endemic long-term persistence. These findings highlight the capacity of M. conjunctivae to establish diverse interactions and persist in host populations, also with different transmission conditions.

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

Border disease 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 Border disease to be listed, Article 9 for the categorisation of Border disease according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species concerned by Border disease. 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, Border disease 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 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (c), (d) and (e) of Article 9(1). The animal species to be listed for Border disease according to Article 8(3) criteria are mainly sheep and other species of the family Bovidae as susceptible and reservoirs.