A review of viral diseases of the European wild boar: effects of population dynamics and reservoir rôle

Subclinical Ovine Gammaherpesvirus 2-Related Infections in Free-Ranging Wild Boars (Sus scrofa) from Southern Brazil

Ovine gammaherpesvirus 2 (OvGHV2), is a Macavirus and the cause of sheep-associated malignant catarrhal fever (SA-MCF), in which sheep are the asymptomatic reservoir hosts. Susceptible mammalian populations infected by OvGHV2 may develop clinical SA-MCF or subclinical infections. All members of the Macavirus genus known to be associated with MCF are collectively referred to as the MCF virus (MCFV) complex. This report describes the occurrence of subclinical OvGHV2-related infections in free-ranging wild boars (Sus scrofa) from southern Brazil. Specific body organs (n = 14) and biological samples (nasal and oral swabs; n = 17) were collected from 24 asymptomatic wild boars from a conservation unit located within the Central-eastern mesoregion of Paraná State. Organs were processed to observe histopathological patterns suggestive of diseases of domestic animals; only pulmonary samples were used in an immunohistochemical assay designed to detect MCFV tissue antigens. Furthermore, all samples were submitted to molecular assays designed to detect the OvGHV2 tegument protein gene. Viral-induced pneumonia was diagnosed in two wild boars; one of these contained OvGHV2 DNA, with MCFV antigens identified in the other. Additionally, MCFV tissue antigens were detected within pulmonary epithelial cells of the lungs with and without pulmonary disease. Collectively, OvGHV2 was detected in 37.5% (9/24) of all wild boars, with detection occurring in the organs of 57.1% (8/14) wild boars and the oral cavity of one animal. These results demonstrated that these wild boars were subclinically infected by OvGHV2, and that infection produced typical pulmonary alterations. In addition, the detection of OvGHV2 within the oral cavity of one wild boar may suggest that this animal may be a potential disseminator of this pathogen to susceptible animal populations, including livestock and wildlife, acting as a possible bridge host for OvGHV2. Furthermore, infection by OvGHV2 probably occurred due to incidental contact with asymptomatic sheep maintained within the surrounding rural areas and not within the conservation units.

Molecular detection of ovine gammaherpesvirus 2 in free ranging wild boars (Sus scrofa) from Southern Brazil

Ovine gammaherpesvirus 2 (OvGHV2) is a member of Macavirus genus, subfamily Gammaherpesvirinae, family Herpesviridae, and causes sheep associated-malignant catarrhal fever (SA-MCF) in a wide range of ungulates. However, no descriptions of SA-MCF and/or infections due to OvGHV2 were identified in the wild boar (Sus scrofa). This study investigated the occurrence of OvGHV2 in the lungs (n = 44) of asymptomatic, free ranging wild boars captured in several regions of Paraná State, Southern Brazil. A PCR assay targeting the OvGHV2 tegument protein gene amplified OvGHV2 DNA in 4.55% (2/44) of the pulmonary tissues evaluated. Sequence analysis confirmed that the OvGHV2 strains herein identified have 98.4% deduced amino acid (aa) sequence identity with the prototype strain of OvGHV2 and 96.4-100% aa identity with similar strains of OvGHV2 detected in several animal species from diverse countries. These findings confirmed that these two wild boars were infected by OvGHV2, represent the first description of this infection in these animals, and add to the number of pathogens identified in this animal species. Furthermore, these findings contrast earlier descriptions of OvGHV2 in swine since in all previous reports the infected pigs demonstrated clinical manifestations of disease. Consequently, these wild boars from Southern Brazil were subclinically infected or suffered asymptomatic infections by OvGHV2.

Porcine Epidemic Diarrhea Virus: Etiology, Epidemiology, Antigenicity, and Control Strategies in China

Porcine epidemic diarrhea virus (PEDV) is a porcine enteric coronavirus, which is one of the main causative agents of porcine epidemic diarrhea (PED), with 100% morbidity and 80-100% mortality in neonatal piglets. Since 2010, large-scale PED caused by highly pathogenic variants of PEDV has occurred successively in China and other countries in the world, posing a great threat to the global pig industry. It has been demonstrated in many investigations that the classic attenuated vaccine strain, PEDV CV777, is insufficient to fully protect against the PEDV variants. Moreover, the maternally derived antibodies elicited by inactivated vaccines also cannot completely protect piglets from infection. In addition, feedback feeding poses a risk of periodic PEDV recurrence in pig farms, making it challenging to successfully limit the spread of PEDV in China. This review focuses on the etiology, epidemiology, antigenicity, and control strategies of PEDV in China and provides information for the formulation of effective control measures.

Assessment of Ecological Bridges at Wildlife Crossings in Türkiye: A Case Study of Wild Boar Crossings on the Izmir-Çeşme Motorway

In this study, the use of an ecological bridge installed as a wildlife overpass and constructed in the Zeytinler neighborhood in 2020 was analyzed as a mitigating factor in wild-boar-vehicle collisions (WVCs) on the Izmir-Çeşme motorway. In this context, this study aimed to assess the use of the Zeytinler Ecological Bridge by wild boars (Sus scrofa Linnaeus, 1758). To this end, wildlife crossings were monitored, analyzed, and modeled with Bayesian networks. Between August 2020 and December 2022, a total of 686 instances of movement were observed among six medium to large wild mammal species. Wild boars accounted for approximately 87.5% of the recorded wildlife crossings, with foxes comprising 10%. The findings showed that the highest frequency of wildlife crossings occurred during the autumn season, particularly between 22:00 (10 p.m.) and 02:00 (2 a.m.), coinciding with the Waxing Gibbous and Waxing Crescent phases of the moon. The model outcomes highlighted that during the autumn season with a full pond, wild boar crossings increased by one and a half times in comparison to regular herd crossings. Throughout the observation period, there were no instances of wild boar fatalities subsequent to the completion of the bridge.

First Serologic Survey of Erysipelothrix rhusiopathiae in Wild Boars Hunted for Private Consumption in Portugal

Erysipelothrix rhusiopathiae is a relevant zoonotic infectious agent causing swine erysipelas (SE) in wild boar. In Portugal, there is no information on its occurrence. For this reason, this study aims to perform a first serosurvey of SE in hunted wild boars in Portugal. During the 2019/2020 hunting season, 111 sera from hunted wild boar were collected and analysed serologically in the laboratory with a commercial ELISA kit. No animals were eviscerated and examined after the hunt. The hunters took it all for private consumption. The results identified 18 animals that were exposed to SE, corresponding to a seroprevalence of 16.2% (95% CI: 19.9-24.4%). No statistical significance was observed on the effect of gender and age on seropositivity. However, wild boar hunted in Pinhel County, had five times more likely to be seropositivity (p-value < 0.05; OD = 5.4). Apart from its potential debilitating capacity and chronicity in the wild boar population, SE is also a very serious occupational zoonosis. Thus, the result of this first serosurvey in Portugal should raise awareness and alert competent national veterinary authorities and those involved in the hunting sector, especially hunters who directly handle these carcasses. Further studies should be conducted to better understand the role of wild boar as a reservoir and spillover of this disease to other animals and humans.

Hepatitis E Virus in the Wild Boar Population: What Is the Real Zoonotic Risk in Portugal?

Hepatitis E virus (HEV) is an important zoonosis in wild boar. Reported zoonotic cases are mainly associated with the consumption of raw/undercooked meat and/or liver. This study aims to determine the occurrence of HEV in the Portuguese wild boar population. During the hunting season 2021/2022, 123-matched samples (liver, faeces, and blood) were collected from hunted wild boars throughout Portugal. An RT-PCR assay tested liver and faeces samples to detect HEV-RNA. From blood samples, an ELISA test was performed. Only one liver sample was positive for HEV (0,8%) and one other from faeces. A total of 34 sera were seropositive (26.7%). At the same time, in a survey of 106 hunters, 21 consumed/ate the liver of wild boars (19.8%). Only three recognised the possibility of consuming it undercooked. Contrary to previous studies in Portugal, the prevalence of HEV in liver and faeces is low, but the seropositivity is higher. But, when analyzing in detail, it could be observed that an HEV hotspot exists in the southeast of central Portugal and that it is a zoonotic risk for hunters of this region. The data of this study reinforce the importance of including HEV in surveillance programs for wildlife diseases to expand the potential zoonotic information.

Exploring the potential links between gut microbiota composition and natural populations management in wild boar (Sus scrofa)

We surveyed wild boar (Sus scrofa) populations using 16S rRNA gene analysis of the gut microbiota in fresh faeces taken from 88 animals hunted in 16 hunting estates. The wild boar is a very convenient model system to explore how environmental factors including game management, food availability, disease prevalence, and behaviour may affect different biological components of wild individuals with potential implications in management and conservation. We tested the hypotheses that diet (according to stable carbon isotopes analyses), gender (i.e., animal behaviour studying males and females), and both health (analyses of serum samples to detect exposure to several diseases) and form statutes (i.e., thoracic circumference in adults) are reflected in changes in the intestinal microbiota. We focused on a gut functional biomarker index combining Oscillospiraceae and Ruminococcaceae vs. Enterobacteriaceae. We found that gender and the estate (population) were explanatory variables (c.a. 28% of the variance), albeit a high degree of overlapping among individuals was observed. The individuals with higher abundance of Enterobacteriaceae showed a gut microbiota with low diversity, mostly in males. Significant statistical differences for thoracic circumference were not found between males and females. Interestingly, the thoracic circumference was significantly and inversely related to the relative abundance of Enterobacteriaceae in males. Overall, we found that diet, gender, and form status were major factors that could be related to the composition and diversity of the gut microbiota. A high variability was observed in the biomarker index for populations with natural diet (rich in C3 plants). Although, we noticed a marginally significant negative trend between the index (higher abundance of Enterobacteriaceae) and the continuous feeding of C4 plants (i.e., supplementary maize) in the diet of males. This result suggests that continuous artificial feeding in hunting estates could be one of the factors negatively influencing the gut microbiota and the form status of wild boars that deserves further investigations.

Eleven Years of Health Monitoring in Wild Boars (Sus scrofa) in the Emilia-Romagna Region (Italy)

In recent years, the growth of wild ungulates has increased the focus on their health monitoring. In particular, the health status of wild boars is relevant for the economic impact on the pig industry. The Emilia-Romagna region activated a wildlife monitoring plan to better evaluate the health status of the wild boar population. Between 2011 and 2021, samples of found dead and hunted wild boar have been examined for trichinellosis, tuberculosis, brucellosis, african swine fever, classical swine fever, Aujeszky's disease, swine vesicular disease, and swine influenza A. Trichinella britovi was identified in 0.001% of the examined wild boars; neither M. bovis nor M. tuberculosis were found in M. tuberculosis complex positive samples; 2.3% were positive for Brucella suis; 29.4% of the sera were positive for Aujeszky's disease virus; and 0.9% of the samples were positive for swine influenza A virus. With an uncertain population estimate, the number of animals tested, the number of positives, and the sampling method do not allow us to make many inferences but suggest the need to implement and strengthen the existing surveillance activity, as it seems to be the only viable alternative for safeguarding animal and human health.

Presence of Foodborne Bacteria in Wild Boar and Wild Boar Meat-A Literature Survey for the Period 2012-2022

The wild boar is an abundant game species with high reproduction rates. The management of the wild boar population by hunting contributes to the meat supply and can help to avoid a spillover of transmissible animal diseases to domestic pigs, thus compromising food security. By the same token, wild boar can carry foodborne zoonotic pathogens, impacting food safety. We reviewed literature from 2012-2022 on biological hazards, which are considered in European Union legislation and in international standards on animal health. We identified 15 viral, 10 bacterial, and 5 parasitic agents and selected those nine bacteria that are zoonotic and can be transmitted to humans via food. The prevalence of Campylobacter, Listeria monocytogenes, Salmonella, Shiga toxin-producing E. coli, and Yersinia enterocolitica on muscle surfaces or in muscle tissues of wild boar varied from 0 to ca. 70%. One experimental study reported the transmission and survival of Mycobacterium on wild boar meat. Brucella, Coxiella burnetii, Listeria monocytogenes, and Mycobacteria have been isolated from the liver and spleen. For Brucella, studies stressed the occupational exposure risk, but no indication of meat-borne transmission was evident. Furthermore, the transmission of C. burnetii is most likely via vectors (i.e., ticks). In the absence of more detailed data for the European Union, it is advisable to focus on the efficacy of current game meat inspection and food safety management systems.

Snow Metrics as Proxy to Assess Sarcoptic Mange in Wild Boar: Preliminary Results in Aosta Valley (Italy)

The widespread diffusion of the wild boar on the Italian territory and its consistent use for hunting have created the possibility to conduct multiple studies on the pathologies afflicting this ungulate. Nevertheless, in the last two decades, only some pathologies such as classical and African Swine Fever, Tuberculosis, Brucellosis from Brucella suis have benefited from substantial public funding and the consequent great interest from the scientific world, while less attention was addressed to parasitic diseases including sarcoptic mange. Therefore, to fill this gap, the purpose of this study was to contribute to the knowledge of sarcoptic mange in the wild boar population in Aosta Valley in the Northwest of Italy, including sympatric species as foxes. Due to past field surveys, it has been possible to find a possible role of snow metrics in the spread of this pathogen. Even if there are only empirical evidence and the mechanism remain unknown remote sensing analysis considering snow metrics were performed to provide to veterinarians, foresters, biologists, and ecologists new tools to better understand wield board dynamics and join to ordinary tool an instrument to enhance management and planning strategies. The snow metrics (SM) were derived from USGS NASA Landsat 8 L2A retrieved from Theia CNES platform and processed in Orfeo Toolbox LIS extension package. The relationship between SM and the disease spread was tested per each Aosta Valley municipality obtaining LISA maps for each hunting season. The results have showed that this parasite is present in an endemic form even if with rather low prevalence values, equal to 1.2% in the season hunting season 2013/2014, and equal to 7.5% in the hunting season 2014/2015. Moreover, within simultaneous given values of SM, sarcoptic mange seem to find good conditions for spreading.

Genotype Shift of Malaysian Porcine Circovirus 2 (PCV2) from PCV2b to PCV2d within a Decade

Simple Summary

This study aims to provide an updated Malaysian porcine circovirus 2 (PCV2) situation after a knowledge gap of one decade. Molecular detection rates of 83.78% and 83.54% at farm and sample population level were reported, close to previous publication. However, an obvious genotype shift from genotype PCV2b to PCV2d was revealed. Substitution rate for PCV2 cap gene sequences in this study was estimated at 1.102 × 10⁻³ substitutions/site/year, in agreement with the high substitution rate expected from PCV2 strains. Phylogenetic clustering pattern according to the year of sample origin was observed, suggesting possible nucleotide mutation occurring over time. Concurrent circulation of different PCV2 strains within one farm and within a single individual were also observed. This study also reports detection of PCV2 antigen across all production age groups from fetuses to sows; in abattoir lung samples from clinically healthy finishers; and in the wild boar population roaming Peninsular Malaysia. These observations of high molecular detection rates in farms, clinically healthy abattoir samples and in the wild boar population; and most importantly, a new wave of genotype shift from PCV2b to PCV2d—warrant further attention on the Malaysian PCV2 situation pertinent to the control and management strategy applicable to local swine farming.

Abstract

This paper aims to update the molecular status of porcine circovirus 2 (PCV2) in Malaysia. Firstly, the molecular detection rate of PCV2 in farm and sampled pig population were reported to be 83.78% (31/37 farms) and 83.54% (66/79 pigs) positive for PCV2, respectively. PCV2 was detected across all age groups, from fetuses, porkers to sows. Co-detection of PCV2 and PCV3 antigens was also reported at a rate of 28.77% (21/73). Secondly, PCV2 antigen was also detected in Malaysian abattoir lung samples: 18 out of 19 (94.74%) samples originating from clinically healthy finishers were tested positive. Further, this is the first study to confirm the circulation of PCV2 in the wild boar population roaming Peninsular Malaysia, where 28 out of 28 (100%) wild boar lung samples were found positive. One decade earlier, only genotype PCV2b was reported in Malaysia. This most recent update revealed that genotypes PCV2a, PCV2b and PCV2d were present, with PCV2d being the predominant circulating genotype. PCV2 cap gene nucleotide sequences in this study were found to be under negative selection pressure, with an estimated substitution rate of 1.102 × 10⁻³ substitutions/site/year (ssy).

Permeability of artificial barriers (fences) for wild boar (Sus scrofa) in Mediterranean mixed landscapes

BACKGROUND

Fences are one of the most widespread manmade features in nature, constituting an artificial limitation to the movement of wildlife. To date, their effects on wildlife behavior have been understudied but this knowledge is required to design effective management procedures. Using 21 GPS-monitored wild boar, we evaluated the permeability of different types of fences and described temporal patterns and spatial hotspots for crossing events. A fence's permeability was inferred by the crossing success, i.e., the number of times that animals crossed a barrier vs the number of times they did not cross. The vulnerability of fences at watercourses was explored by assessing whether the frequency of crossings was higher around watercourse intersections than expected by chance.

RESULTS

Well-maintained big game proof fences were the most effective in reducing successful wild boar crossings; they were, on average, 30% more efficient than livestock type fences. Crossing success was higher for males than females and during the food shortage period than in the food abundance period. The frequency of crossings around watercourses was higher than expected by chance, especially in moderately and well-maintained big game proof type fences.

CONCLUSION

While no fence type was 100% wild boar proof, well-maintained big game proof fences substantially constrained the movement of boar. However, they are vulnerable around watercourses. Managing the conflicts in which this species is involved, such as shared infections and agricultural damage, would require fences that are even more effective than the ones analyzed here, ideally in conjunction with other preventive actions. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Isolation of Biotype 1 Serotype 12 and Detection of Actinobacillus pleuropneumoniae from Wild Boars

Actinobacillus pleuropneumoniae is a major pathogen of swine, which can cause severe pleuropneumonia in pigs, but sometimes the disease can be generalized. Diseases caused by A. pleuropneumoniae are frequent all over the world, resulting in high losses among domestic pigs. However, our knowledge on the occurrence of A. pleuropneumoniae in wild boars and feral pigs is limited. We aimed to examine the carriage of A. pleuropneumoniae by hunted wild boars. The presence of A. pleuropneumoniae was examined in tonsils of 68 hunted wild boars collected at a game processing unit. An in-house designed species-specific PCR test was used to detect the gene of Apx IV toxin, and the samples were inoculated on a modified selective agar. A. pleuropneumoniae was detected in 10 animals (14.7%) by PCR and one A. pleuropneumoniae serotype 12 strain was isolated. The antibiotic resistance pattern of the strain resembled field strains that were isolated from farmed pigs in Hungary. This is the first case for the detection of A. pleuropneumoniae not only using PCR or ELISA, but also its isolation, identification, and serotyping.

Genetic Diversity of Porcine Circovirus Types 2 and 3 in Wild Boar in Italy

Simple Summary

Porcine circoviruses (PCVs) are major viral agents of farmed swine, causing relevant economic impact due to direct losses and control measures expenses. Wild boar may serve as a PCVs reservoir for the domestic pigs, thus threatening for production efficiency in pig farms. PCV infection in both domestic pigs and wild boar has been chiefly studied in Northern Italy, a densely populated area with a highly developed pork industry. However, data on circulation of PCV are scarce in other Italian areas. For the above reasons, along with the increasing sanitary relevance of wildlife as host of many livestock diseases, we carried out an epidemiological study to assess the prevalence and genetic characteristics of the PCVs circulating in wild boar in Basilicata region (Southern Italy), characterized by large forested areas with limited anthropic presence. A high prevalence was detected, suggesting that PCVs infection is endemic in the study population. These findings are of particular interest as the pig production system of the study area involves local breeds raised outdoor for the production of high-quality cured meat, thus having a high risk of being in contact with infected wild boar.

Abstract

Porcine circovirus (PCV) infection is associated with relevant economic impact to the pig industry. To date, four species of PCV (PCV1 to 4) have been identified but only PCV2 has been associated firmly with disease in pigs. The objective of this study was to assess the prevalence of PCV2 and PCV3 in the wild boar population in Basilicata region, Southern Italy, since this region is characterized by large forested and rural areas and the anthropic pressure is lower than in other Italian regions. Liver samples from 82 hunted wild boar were collected in 2021 from 3 different hunting districts. Sixty (73%, 95%CI: 63–82) samples tested positive for PCVs by quantitative PCR. In detail, 22 (27%, 95%CI: 18–37) were positive for PCV2, 58 (71%, 95%CI: 60–79) for PCV3, and 20 (24.4%, 95%CI 16–35) for both PCV2 and PCV3. On genome sequencing, different types and sub-types of PCV2 and PCV3 were identified, remarking a genetic diversity and hinting to a global circulation for the identified PCV strains. Overall, the high prevalence suggests that PCV2 and PCV3 infections are endemic in the wild boar population, posing risks for semi-intensive and free-range pig farming, typical of this region, due to contact with PCV-infected wild boar.

Age-Dependent Invasion of Pseudorabies Virus into Porcine Central Nervous System via Maxillary Nerve

Pseudorabies virus (PRV) is the causative agent for Aujeszky’s disease, a disease that mainly affects pigs and incidentally other domestic and wild animals. While PRV is almost always fatal, causing neurological disease independently of the age in non-porcine species, the development of neurological manifestation in its host species, the pig, highly depends on the age. In this study, an attempt was made to investigate the effect of nerve development on the outcome of virus infection and the effect of virus infection on the structure of nerves in piglets of various ages. For that reason, 42 pigs at the age of one (n = 14), three (n = 14) and five (n = 14) weeks were inoculated with 10⁷ TCID₅₀ of PRV Kaplan strain and euthanized at one- or four-days post inoculation (DPI). The tissues of the trigeminal nervous pathway were collected and examined for virus replication (titration) in cell cultures for nerve morphology by light and transmission electron microscopy, and for viral antigen visualization by immunohistochemistry. The results showed that as the age of the pig increases, virus titers and clinical manifestations reduced, while, at the same time, myelin and axon development ceased. Following infection, the nerve structure was disrupted at all ages examined, being more prominent in one-week-old pigs compared to five-week-old pigs. In conclusion, the age-dependent PRV neuroinvasion in pigs seems to correlate with the morphological changes of neurons.

Aujeszky's disease in hunting dogs after the ingestion of wild boar raw meat in Sicily (Italy): clinical, diagnostic and phylogenetic features

Background

Aujeszky's disease is caused by Suid Herpes Virus-1 and species belonging to the genus Sus scrofa are the main reservoir hosts. This virus, however, is capable of infecting and causing severe disease, with an almost constant fatal outcome in other species, both domestic and wild (carnivores, monogastric herbivores and ruminants). Moreover, the possibility of transmission to humans has been demonstrated. This study reports and describes the clinical, diagnostic, pathological and phylogenetic aspects of two cases of Aujeszky's disease in two hunting dogs following the ingestion of infected wild boar raw meat. These cases are contextualized in the province of Messina (Sicily), where a high prevalence of Aujeszky's disease has been recorded (average of 12,20% in the period 2010–2019) in farmed pig, and with evidence of spread to other species. A severe outbreak in cattle has recently been reported in these areas. Nevertheless, cases of Aujeszky's disease in dogs are rarely reported and this study represents the first well-documented report in this species in Sicily.

Case presentation

After a wild boar hunt, two dogs showed neurological symptoms and intense itching unresponsive to therapy. Diagnosis of Aujeszky's disease was made based on clinical suspicion, anamnestic information and confirmed by the isolation of the virus from the brain of both dogs. In addition, molecular typing, sequencing and phylogenetic analysis of the Real-Time PCR products were performed. The sequences studied were placed in the Italian Clade 1 along with the sequences obtained from wild boars and hunting dogs from Italy and France.

Conclusions

The finding of this disease in non-natural hosts in Sicilian multi-host epidemiological contexts suggests that the risk of inter-species transmission is concrete and that attention should be paid to developing disease control programs in these territories. The data obtained from genome sequencing of the two SuHV-1 isolates contribute to the enrichment of the GenBank with unknown sequences and the phylogenetic analysis implementation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03138-2.

Characterization and management of interaction risks between livestock and wild ungulates on outdoor pig farms in Spain

Background

To control the transmission of relevant shared diseases, such as animal tuberculosis (TB) and African swine fever (ASF), it is essential to reduce the risk of interaction between livestock and wild ungulates. In Eastern and Central Europe, the current spread of ASF virus affecting wild boar and domestic pigs (especially those raised outdoors and/or in backyards) has devastated the pig sector in affected regions and is seriously threatening other exporting countries. Here, we evaluated the risk of wildlife-livestock interactions on 45 outdoor pig farms in Spain, the second largest pork producer in the EU and then proposed biosecurity-related actions. An integrated, systematic wildlife risk mitigation protocol based on interviews, questionnaires and field audits was developed and applied on each farm.

Results

Most of the interaction risk points were associated with water sources (84.2%; 701/832), mainly springs and ponds, which accounted for almost all the specific points with high or very high risk scores. The risk of interaction at feeding points (6.9%; 57/832) and those associated with facilities for livestock and/or game management (8.9%; 74/832) were rated as low and very low risk, respectively. Wild boar were present and hunted on 69% of the farms. Supplementary feeding for wild ungulate species (mainly wild boar) was provided on almost half (48.9%; 22/45) the surveyed farms. Risk mitigation actions were categorised to target water access, waterers, food, other livestock species, grazing, wildlife, and offal disposal. Of the total number of actions (n = 2016), 82.7% were identified as priority actions while 17.3% represented alternative options which were identified less cost-effective. On average, 37.1 (median: 32; range 14–113) action proposals per study farm were made and 2.0 (median: 1; range 0–4) per risk point. The mean estimated cost of implementing the proposed priority actions was 14,780 €/farm (25.7 €/hectare and 799.4 €/risk point).

Conclusions

This study expands the knowledge of interaction risks between domestic pigs and wild ungulates in outdoor pig farming systems and highlights the importance of considering local risks and management practices when designing and prioritising adapted wildlife risk mitigation and biosecurity actions. This practical and feasible protocol developed for Mediterranean ecosystems is easily transferable to professionals and can be adapted to extensive (outdoor) production or epidemiological systems in other European regions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40813-021-00246-7.

Serological survey of antibodies to four pathogens in wild boars in Nagano Prefecture, Japan

Wild boars (Sus scrofa) captured or found dead in Nagano Prefecture were surveyed for antibodies to Aujeszky’s disease virus (ADV), Erysipelothrix rhusiopathiae, porcine reproductive and respiratory syndrome virus (PRRSV), and Toxoplasma gondii. While all 168 samples tested were negative for anti-ADV antibodies and all 140 samples tested were negative for anti-PRRSV antibodies, all 190 samples tested were positive for anti-E. rhusiopathiae antibodies and 12 of 180 samples were positive for anti-toxoplasma antibodies. These results suggest that since E. rhusiopathiae and T. gondii cause zoonotic diseases, in addition to wild boars being a potential source of infection for domestic pigs, caution should be taken when handling wild boars or eating wild boar meat because of the possibility of human infection.

Porcine Enteric Coronavirus Infections in Wild Boar in Poland - a Pilot Study

Introduction

Porcine epidemic diarrhoea virus (PEDV) of the Coronaviridae family causes significant economic losses in the pig industry worldwide. Wild boars contribute to the transmission of different viral, bacterial and parasitic infections to livestock animals and humans. However, their role in the maintenance and transmission of PEDV has not been established.

Material and Methods

In this study, blood and faecal samples from 157 wild boars were collected from 14 provinces of Poland during the 2017–2018 hunting season. RNA was extracted from the faecal homogenate supernatant and subjected to quantitative RT-PCR (RT-qPCR), while clotted blood samples were used for detection of antibodies against PEDV by ELISA.

Results

Five blood samples (3.2%) were seropositive in ELISA, while none of the faecal samples were found positive using RT-qPCR assays.

Conclusion

The results of this analysis indicate the need for additional studies incorporating a larger number of samples and preferably comparing different serological methods, to confirm whether wild boars in Poland act as PEDV reservoirs.

A systematic review and meta-analysis of hepatitis E virus (HEV) in wild boars

This systematic review and meta-analysis summarize the available information on Hepatitis E virus (HEV) -specific antibody seroprevalence and HEV RNA prevalence in wild boar, one of the most abundant game species worldwide. A literature search (CAB Abstracts, Web of Science, Embase and Scopus) was performed to find relevant peer-reviewed works published during the period 1990-2020. A random-effect model was carried out to calculate the pooled HEV-specific antibody seroprevalence and HEV RNA prevalence estimates with 95% confidence intervals, and I2 statistic was used to assess the heterogeneity of the data. Values by subgroups were compared according to the geographical area, age class (≤ 12 months old and > 12 months old), and sample type (bile, faeces, liver, meat/muscle, serum). Sixty-nine publications were selected, with the majority of the studies from Southern Europe (n = 27). The pooled HEV-specific antibody seroprevalence in wild boar was 28% (CI95% 23-34) and the HEV RNA prevalence 8% (CI95% 6-10). The analysis highlighted a significant heterogeneity among the estimates from the included studies (I2 = 98% and I2 = 95% for HEV-specific antibody seroprevalence and viral prevalence respectively). The moderator analysis indicated a statistically significant difference (p-value = 0.03) for the HEV RNA prevalence according to the sample type, with the highest value in bile (17%, CI95% 9-27), followed by liver (10%, CI95% 7-14), serum (7%, CI95% 4-10), faeces (5%, CI95% 2-9), and meat/muscle (3%, CI95% 0.04-10). Finally, the HEV RNA prevalence in Europe (8.7, CI95% 6.7-11) was significantly (p-value = 0.04) higher than in Asia (4, CI95% 0.6-8). The analysis highlights the important role of wild boar in the epidemiology of HEV.

First Isolation and Molecular Characterization of Pseudorabies Virus in a Hunting Dog in Sicily (Southern Italy)

Pseudorabies virus (PrV) is the etiological agent of Aujeszky's disease, a viral infection that causes neurological lethal illness in mammals other than swine. Herein, we describe the occurrence of PrV infection in a hunting dog that had been bitten by an infected wild boar in Sicily, reporting for the first time genetic and phylogenetic data on the virus strain isolated in a dog in this Italian region. The dog was referred for severe neurological signs, respiratory distress, and intense itch around the muzzle. Death occurred within 48 h to the onset of clinical signs. On gross examination, self-induced skin lesions to the head due to intense itching and diffuse cerebral congestion were observed, whereas mild, aspecific, nonsuppurative meningitis was histologically diagnosed. Diffuse PrV positivity in neurons of the brainstem was observed by immunohistochemistry. PrV DNA was isolated and amplified from olfactory bulbs by nested PCR, targeting the viral glycoprotein G gene, and the sequence obtained matched with sequences of PrV isolates from dogs and wild boar. Isolation of PrV in the dog herein analysed denotes the spread of the virus in wild boar populations in Sicily and provides a proof of direct interspecies transmission. Thus, there is an urgent need to increase our understanding of the epidemiology of the PrV infection in wildlife to provide tools to trace possible spill over into domestic pigs or other livestock.

Aujeszky's Disease in South-Italian Wild Boars (Sus scrofa): A Serological Survey

Simple Summary

Aujeszky’s disease (AD, pseudorabies) is a viral disease of suids caused by Suid Herpesvirus 1 (SHV-1) also referred as Aujeszky’s disease virus (ADV) or Pseudorabies virus (PRV). The aim of our study was to evaluate seroprevalence of AD in wild boar hunted in the Campania Region, during the 2016–2017 hunting season. A total of 503 serum samples from wild boars hunted in the provinces of Campania Region were tested for antibody against ADV using an ELISA assay. A Seroprevalence of 23.85% (120/503, 95% Confidence Interval (CI 95%: 20.15–27.55) was found. Gender was not significantly associated with of ADV seropositivity (p > 0.05), while the presence of ADV antibodies was statistically associated with age (>36-month, p < 0.0001) and location (Avellino, p = 0.0161).

Abstract

Aujeszky’s disease (AD, pseudorabies) is a viral disease of suids caused by Suid Herpesvirus 1 (SHV-1) also referred as Aujeszky’s disease virus (ADV) or Pseudorabies virus (ADV). Domestic pig and Wild boar (Sus scrofa) are the natural host, but many species can be infected with ADV. The aim of our study was to evaluate seroprevalence of AD in wild boar hunted in the Campania Region, during the 2016–2017 hunting season. A total of 503 serum samples from wild boars hunted in the provinces of Campania Region (Southern Italy) were collected and were tested for antibody against ADV using an AD, blocking ELISA assay. A Seroprevalence of 23.85% (120/503, 95% Confidence Interval (CI): 20.15–27.55) was found. Gender was not significantly associated with of ADV seropositivity (p > 0.05), while the presence of ADV antibodies was statistically associated with age (>36-month, p < 0.0001) and location (Avellino, p = 0.0161). Our prevalence values are like those obtained in 2010 in our laboratory (30.7%), demonstrating a constant circulation of ADV in the area.

Prevalence of Infection with Porcine Circovirus Types 2 and 3 in the Wild Boar Population in the Campania Region (Southern Italy)

In recent years, porcine circovirus (PCV) infection has been documented as an important and emerging health concern for livestock and wildlife worldwide. The purpose of the present study was to assess the molecular prevalence of PCV-2 and PCV-3 and to clarify the epidemiological role of wild boars in the circulation of this virus in Campania, Southern Italy. For this purpose, samples from several organs were collected during the hunting season 2017-2018 from 148 wild boars in the Campania region. Quantitative real-time PCR was used for the detection and quantification of PCV-2 and PCV-3 genomes. The combined prevalence of PCV-2 and PCV-3 was 74.32% in the wild boars tested. The proportions of wild boars positive for PCV-2 or PCV-3, or coinfected, were 47.30%, 49.32%, and 22.30%, respectively. No link was detected between PCV positivity and location, but gender was a risk factor for the disease (female; p < 0.0001; OR 0.29). Furthermore, our study provides a snapshot of PCV-2 and PCV-3 circulation in wild boars in the Campania region: our findings can help us to better understand the role of wildlife in PCV circulation.

African Swine Fever in Wild Boar in Europe-A Review

The introduction of genotype II African swine fever (ASF) virus, presumably from Africa into Georgia in 2007, and its continuous spread through Europe and Asia as a panzootic disease of suids, continues to have a huge socio-economic impact. ASF is characterized by hemorrhagic fever leading to a high case/fatality ratio in pigs. In Europe, wild boar are especially affected. This review summarizes the currently available knowledge on ASF in wild boar in Europe. The current ASF panzootic is characterized by self-sustaining cycles of infection in the wild boar population. Spill-over and spill-back events occur from wild boar to domestic pigs and vice versa. The social structure of wild boar populations and the spatial behavior of the animals, a variety of ASF virus (ASFV) transmission mechanisms and persistence in the environment complicate the modeling of the disease. Control measures focus on the detection and removal of wild boar carcasses, in which ASFV can remain infectious for months. Further measures include the reduction in wild boar density and the limitation of wild boar movements through fences. Using these measures, the Czech Republic and Belgium succeeded in eliminating ASF in their territories, while the disease spread in others. So far, no vaccine is available to protect wild boar or domestic pigs reliably against ASF.

Molecular detection and characterization of highly pathogenic porcine reproductive and respiratory syndrome virus from a natural outbreak in wild pigs, Mizoram, India

This study reports for the first time a natural outbreak of highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRS) caused by HP-PRRS virus (HP-PRRSV) in wild pigs characterized by sudden onset of depression, anorexia, respiratory distress, and high fever. The disease has caused severe haemorrhagic pneumonia, haemorrhagic lymphadenitis, enlarged spleen with areas of infarction, and petechial haemorrhages on the myocardium and on the surface of kidneys. HP-PRRSV was detected in representative tissue samples by reverse transcription-PCR, and the field strain was isolated in the MA104 cell line. The phylogenetic analyses based on the whole genome sequences and nucleotide sequences of open reading frame 5 (ORF5) gene showed close grouping with the subtype IV of lineage 8/8.7 of PRRSV II, which represents the HP-PRRSV strains that predominate in the pig population of China since 2010. The amino acid sequence analysis of the ORF5 gene revealed the replacement of leucine (L) at position 39 to isoleucine (I) in the primary neutralizing epitope. Among the four potential N glycosylation sites, the N34 was mutated and found to be restricted to only three N glycosylation sites. The present findings have indicated that HP-PRRSV can cause fatal outbreaks and may emerge as a major threat to the wild pig population.

Detection of Hepatitis E Virus in Hyalomma lusitanicum Ticks Feeding on Wild Boars

Little is known about the role of ticks in maintaining highly prevalent zoonotic viruses in wildlife, such as hepatitis E virus (HEV), which do not require ticks for transmission between animals and humans. In this cross-sectional study, adult female ticks were collected from Eurasian wild boar (Sus scrofa) in autumn 2015 in Spain. HEV RNA in both ticks and wild boar was evaluated by RT-qPCR. Twenty-nine adult Hyalomma lusitanicum ticks were collected from 29 wild boars. HEV RNA was detected in a total of 10 tick (34.4%) and 11 wild boar serum samples (37.9%). In two cases, detectable HEV RNA was found in a wild boar but not in the tick collected from them. In contrast, one HEV-positive tick was collected from an HEV-negative wild boar. All viral sequences were consistent with genotype 3f. We describe for the first time the presence of HEV RNA in adult Hyalomma lusitanicum ticks.

Research priorities to fill knowledge gaps in wild boar management measures that could improve the control of African swine fever in wild boar populations

The European Commission asked EFSA to provide study designs for the investigation of four research domains (RDs) according to major gaps in knowledge identified by EFSA in a report published in 2019: (RD 1) African swine fever (ASF) epidemiology in wild boar; (RD 2) ASF transmission by vectors; (RD 3) African swine fever virus (ASFV) survival in the environment, and (RD 4) the patterns of seasonality of ASF in wild boar and domestic pigs in the EU. In this Scientific Opinion, the second RD on ASF epidemiology in wild boar is addressed. Twenty-nine research objectives were proposed by the working group and broader ASF expert networks and 23 of these research objectives met a prespecified inclusion criterion. Fourteen of these 23 research objectives met the predefined threshold for selection and so were prioritised based on the following set of criteria: (1) the impact on ASF management; (2) the feasibility or practicality to carry out the study; (3) the potential implementation of study results in practice; (4) a possible short time-frame study (< 1 year); (5) the novelty of the study; and (6) if it was a priority for risk managers. Finally, after further elimination of three of the proposed research objectives due to overlapping scope of studies published during the development of this opinion, 11 research priorities were elaborated into short research proposals, considering the potential impact on ASF management and the period of one year for the research activities.

Screening of Eurasian Tundra Reindeer for Viral Sequences by Next-Generation Sequencing

Reindeer husbandry is essential for the livelihood and culture of indigenous people in the Arctic. Parts of the herding areas are also used as pastures for farm animals, facilitating potential transmission of viruses between species. Following the Covid-19 pandemic, viruses circulating in the wild are receiving increased attention, since they might pose a potential threat to human health. Climate change will influence the prevalence of infectious diseases of both humans and animals. The aim of this study was to detect known and previously unknown viruses in Eurasian tundra reindeer. In total, 623 nasal and 477 rectal swab samples were collected from reindeer herds in Fennoscandia, Iceland, and Eastern Russia during 2016–2019. Next-generation sequencing analysis and BLAST-homology searches indicated the presence of viruses of domesticated and wild animals, such as bovine viral diarrhea virus, bovine papillomavirus, alcephaline herpesvirus 1 and 2, deer mastadenovirus B, bovine rotavirus, and roe deer picobirnavirus. Several viral species previously found in reindeer and some novel species were detected, although the clinical relevance of these viruses in reindeer is largely unknown. These results indicate that it should be possible to find emerging viruses of relevance for both human and animal health using reindeer as a sentinel species.

Long-Term Determinants of the Seroprevalence of the Hepatitis E Virus in Wild Boar (Sus scrofa)

Simple Summary

The hepatitis E virus (HEV) is an emerging multi-host pathogen whose main reservoir is suids, and the leading cause of acute viral hepatitis in humans. This study evaluates the main long-term drivers of the exposure to HEV are in the wild boar population from Doñana National Park (southwestern Spain) during a 13-year period (2005–2018). For this purpose, we assay sera from 700 wild boar in which anti-HEV antibodies are widely distributed (46.7 ± 3.8%, 327 out of 700 sampled). The observed marked interannual fluctuations could be explained by the variations in the population control of the wild boar during the study period and its impact on abundance rates. Several factors operating in the medium and long-term (individual, environmental, populational and stochastic) and their interplay explained the exposure to HEV in wild boar. The preferential use of certain areas by wild boar together with its abundance and the meteorological conditions may be behind the level of exposure. Wild boar population control remains a challenge at the international level, and an increase of shared pathogen-related conflicts associated with this species is expected, as exemplified by HEV.

Abstract

The hepatitis E virus (HEV) is an emerging zoonotic pathogen whose main reservoir is suids. Most of the ecological and epidemiological aspects of its sylvatic cycle remain unknown. Thus, in this work, we study the drivers of HEV exposure in the wild boar population of Doñana National Park (DNP, southwest Spain) operating in the medium and long-term (2005–2018). Anti-HEV antibodies are widely distributed throughout the wild boar (46.7 ± 3.8%, 327 out of 700 sampled), showing a statistically significant age-increasing pattern. The temporal pattern displayed important interannual fluctuations. This could be mediated by marked variations in the population control of the wild boar, and subsequent changes in abundance rates, and its interplay with climatic conditions; as wet years together with a low abundance of wild boar led to the lowest seroprevalence. The fact that seroprevalence is high during conditions of high abundance, and not affected by rainfall level, is probably due to the increased interactions among the animals, and possibly, the subsequent higher environmental contamination with HEV particles. The proximity to the marshland (the main water body of the study area) is associated with a higher risk of testing positive, which is probably mediated by the preferential use of this area during the dry season and the favourable environmental conditions for the survival of HEV particles. A deeper understanding of the epidemiology of HEV in host communities deserves future research concerning other susceptible species. Most importantly, wild boar population control remains a challenge at the international level, and an increase of shared pathogen-related conflicts associated with this species is expected, as exemplified by HEV. Therefore, surveillance of wild boar diseases, including integrated population monitoring and sustainable population control programmes, will be essential to control the associated risks.

Exposure of wild boar to Influenza A viruses in Bavaria: Analysis of seroprevalences and antibody subtype specificity before and after the panzootic of highly pathogenic avian influenza viruses A (H5N8)

Swine influenza A viruses (S-IAV) circulate in wild boar populations worldwide. Subtypes primarily reflect those actually present within the respective pig industry. Accordingly, infections with swine H1N1, H1N2 and H3N2 have been reported for several regions of Germany. As pigs are susceptible not only to S-IAV but also to avian and human influenza A viruses, it is necessary to consider the possibility that new reassortant viruses with pandemic potential may arise in these new hosts. Therefore, in this study the impact of recent IAV epidemics on antibody prevalences in Bavarian wild boar was assessed. Important events considered were the H1N1pdm09 pandemic, which affected humans and swine, and the highly pathogenic avian influenza (HPAI) H5N8 panzootic in 2016 and 2017, affecting wild and domestic birds. IAV seroprevalences were determined analysing 1,396 samples from before and after the H5N8 panzootic, from various regions in Bavaria, a large administrative region in the South of Germany. Taken together, seroprevalences varied markedly from 1.44% to 12.59%, relative to region and time. However, no discrete correlation was found to population density either in wild boar or in pigs. Antibodies against H1N1 were the most prevalent. In addition, antibodies were detected reacting against H1N2 and against H1pdmNx reassortant viruses, already known to circulate in domestic pigs in Bavaria and notably also against the avian influenza A virus H5N8; the latter in samples taken in 2017. These results confirm the exposure of wild boar to IAV of diverse origin and the increasing variability of S-IAV present in the field. The necessity for continuous IAV surveillance not only of domestic swine but also of wildlife is emphasized.

Multi-Scale Spatial Prediction of Wild Boar Damage Risk in Hunchun: A Key Tiger Range in China

Simple Summary

Spatial distribution of wild boar damage risk is important and can be informative to wildlife habitat management. Hunchun is an important active area of Siberian tiger in China. The wild boar damage has brought barriers to the conservation and management of the Siberian tiger in this region. We predicted the spatial distribution of wild boar damage risk in Hunchun in terms of home range and feeding sites scales, and explored the spatial interaction between tiger habitats and the damage risk of wild boar. The results show the distance to the forest edge is an important factor affecting the wild boar damage, and 38.68% of the high-risk areas are overlapped with tiger habitats in Hunchun. Therefore, precise and differentiated management strategies should be adopted in the management of wild boar population.

Abstract

Hunchun, a typical area suffering wild boar (Sus scrofa) damage, is an important region for the Siberian Tiger (Panthera tigris) in China. By incorporating the maximum entropy model with 22 variables in the home range scale (12 variables) and in the feeding site scale (10 variables), we predicted wild boar damage risks in this area of China and analyzed how spatial factors influence damage risk. Damage risk was found to be high in areas close to the forest edge, areas with a higher forest cover and lower to medium deciduous forest proportion, low road density, and a medium river density and farmland proportion. The proportion of farmland which was identified as being in the high damage risk zone was 23.55%, of which 38.68% was within the habitat area of the Siberian Tiger. Finally, we propose wild boar damage prevention based on different management goals.

Macracanthorhynchus hirudinaceus in expanding wild boar (Sus scrofa) populations in Eastern Spain

Prevalence and temporal evolution of the infection by the acanthocephalan Macracanthorhynchus hirudinaceus is studied in the Valencian Community (Eastern Spain), a region only recently fully colonized by the expanding native Eurasian wild boar (Sus scrofa). For 8 years, a total of 1486 wild boars were sampled in order to look for the parasite. The mean prevalence was 20.7% (95% CI, 18.6-22.8; 307/1486). We observed an increasing trend through time, both in the number of wild boars and affected districts. The prevalence of M. hirudinaceus rose in parallel to the annual capture of wild boars, and its presence has been expanding towards the East. A hotspot of M. hirudinaceus is located to the west of the study area, in Muela de Cortes Game Reserve, where 89.6% of the wild boars were positive for the infection, constituting one of the world's highest known prevalence areas.

A framework for surveillance of emerging pathogens at the human-animal interface: Pigs and coronaviruses as a case study

Pigs (Sus scrofa) may be important surveillance targets for risk assessment and risk-based control planning against emerging zoonoses. Pigs have high contact rates with humans and other animals, transmit similar pathogens as humans including CoVs, and serve as reservoirs and intermediate hosts for notable human pandemics. Wild and domestic pigs both interface with humans and each other but have unique ecologies that demand different surveillance strategies. Three fundamental questions shape any surveillance program: where, when, and how can surveillance be conducted to optimize the surveillance objective? Using theory of mechanisms of zoonotic spillover and data on risk factors, we propose a framework for determining where surveillance might begin initially to maximize a detection in each host species at their interface. We illustrate the utility of the framework using data from the United States. We then discuss variables to consider in refining when and how to conduct surveillance. Recent advances in accounting for opportunistic sampling designs and in translating serology samples into infection times provide promising directions for extracting spatio-temporal estimates of disease risk from typical surveillance data. Such robust estimates of population-level disease risk allow surveillance plans to be updated in space and time based on new information (adaptive surveillance) thus optimizing allocation of surveillance resources to maximize the quality of risk assessment insight.

Detection and Characterization of Viral Pathogens Associated with Reproductive Failure in Wild Boars in Central Italy

Simple Summary

Suid herpesvirus 1, porcine circovirus 2 and porcine parvovirus are causative agents of reproductive failures in swine and are widely diffused in the wild boar population. No data describing the impact of those viruses on the reproductive performance of wild boar are so far available. We aimed to investigate the ability of the above viruses to infect foetuses of free-ranging pregnant wild boar sows living in a highly-populated area. Molecular investigation revealed that although all investigated viruses were detected in pregnant sows, only herpesvirus and circovirus were detected in the foetuses. Phylogenetic analysis revealed a close relationship between the strains circulating in wild boar and those already described in domestic swine. This study highlights the importance of monitoring the circulation of pathogens that are shared between domestic and wild pigs. This information is essential for the pig industry to avoid possible economic losses.

Abstract

Wild boar and domestic swine share several pathogens, including viruses responsible for reproductive failures, representing an important sanitary and economic risk for the swine industry. Among them, suid herpesvirus 1 (SuHV-1), porcine circovirus 2 (PCV2) and porcine parvovirus 1 (PPV1) are widely diffused in the wild boar population. Unfortunately, little is known about their pathogenetic mechanisms and impact on the reproductive parameters of wild animals. This study aims to investigate the presence of viruses responsible for reproductive failure in pregnant wild boar sows and their foetuses. The investigation was conducted on 46 pregnant wild boar and their foetuses by molecular analysis; a phylogenetic study was performed on the positive samples. All of the investigated pathogens were identified in sows, while only herpesvirus and circovirus were detected in the tissues of their foetuses. Phylogenetic analysis revealed that the viral sequences obtained from the positive wild boars were closely related to those previously identified in domestic swine belonging to the same study areas. The results suggest that SuHV-1 and PCV2 can infect wild boar foetuses, with a possible impact on wild boar reproductive performance. Moreover, our data highlight the importance of continuous monitoring of swine pathogens circulating in wild environments, so as to carry out adequate sanitary actions.

Prevalence, Virulence and Antimicrobial Susceptibility of Salmonella spp., Yersinia enterocolitica and Listeria monocytogenes in European Wild Boar (Sus scrofa) Hunted in Tuscany (Central Italy)

Wild boar is an animal the population of which constantly increases in Europe. This animal plays an important role as a reservoir for several pathogens, including three of the most important zoonoses: salmonellosis, yersiniosis and listeriosis. The aim of this investigation was to evaluate the occurrence of antimicrobial-resistant and virulence factor genes of Salmonella spp., Yersinia enterocolitica and Listeria monocytogenes isolated from wild boar in Tuscany (Central Italy). During two consequent hunting seasons (2018/2019 and 2019/2020), rectal swabs, spleens and livers were collected from 287 hunted wild boar to isolate strains. Each isolate was tested to investigate its antimicrobial resistance and to detect virulence factor genes by PCR. Eighteen Salmonella strains (6.27%) were isolated. Of these, 66.7% were resistant to streptomycin, 13.4% to cephalothin, 6.67% to imipenem and one isolate (6.67%) was resistant simultaneously to five antimicrobials. Moreover, the most detected genes were sopE (73.4%), pipB (66.7%), sodCI (53.3%), spvR and spvC (46.7%). In total, 54 (17.8%) Yersinia enterocolitica were isolated; of them, 26 (48.1%), 9 (16.7%), 17 (31.5%), 1 (1.85%) and 1 (1.85%) belonged to biotypes 1, 2, 3, 4 and 5, respectively. All strains (100%) demonstrated resistance to cephalothin and 70.4% to amoxicillin-clavulanic acid, 55.6% to ampicillin, and 37.0% to cefoxitin. Additionally, the most detected genes were ystA (25.9%), inv (24.1%), ail (22.2%), ystB (18.5%) and virF (14.8%). Finally, only one Listeriamonocytogenes isolate (0.35%) was obtained, belonging to serogroup IVb, serovar 4b, and it was found to be resistant to cefoxitin, cefotaxime and nalidixic acid. The results highlighted the role of wild boar as a carrier for pathogenic and antimicrobial-resistant Salmonella spp., Yersinia enterocolitica and Listeria monocytogens, representing a possible reservoir for domestic animals and human pathogens.

A CRISPR/Cas12a Based Universal Lateral Flow Biosensor for the Sensitive and Specific Detection of African Swine-Fever Viruses in Whole Blood

Cross-border pathogens such as the African swine fever virus (ASFV) still pose a socio-economic threat. Cheaper, faster, and accurate diagnostics are imperative for healthcare and food safety applications. Currently, the discovery of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) has paved the way for the diagnostics based on Cas13 and Cas12/14 that exhibit collateral cleavage of target and single-stranded DNA (ssDNA) reporter. The reporter is fluorescently labeled to report the presence of a target. These methods are powerful; however, fluorescence-based approaches require expensive apparatuses, complicate results readout, and exhibit high-fluorescence background. Here, we present a new CRISPR-Cas-based approach that combines polymerase chain reaction (PCR) amplification, Cas12a, and a probe-based lateral flow biosensor (LFB) for the simultaneous detection of seven types of ASFV. In the presence of ASFVs, the LFB responded to reporter trans-cleavage by naked eyes and achieved a sensitivity of 2.5 × 10-15 M within 2 h, and unambiguously identified ASFV from swine blood. This system uses less time for PCR pre-amplification and requires cheaper devices; thus, it can be applied to virus monitoring and food samples detection.

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

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

Genotyping and Antibiotic Resistance Traits in Campylobacter jejuni and coli From Pigs and Wild Boars in Italy

The present study investigated the genomic constitution and antimicrobial resistance (AMR) of 238 Campylobacter from pigs and wild boars in Italy between 2012 and 2019. Campylobacter strains were genotyped using multilocus sequence typing (MLST) and whole genome MLST (wgMLST), screened for antimicrobial resistance genes, and tested for phenotypic susceptibility to six different antibiotics. C. coli was detected in 98.31% and 91.66% of pigs and wild boars, while C. jejuni was isolated in the remaining cases. MLST assigned 73 STs and 13 STs in pigs and wild boars, respectively, including 44 novel STs. The predominant ST in pigs was ST-854 (12.36%), followed by ST-9264 (6.18%). ST-1055 and ST-1417 were predominant in wild boars (30% and 13.33%, respectively). The minimum spanning tree using 1,121 global MLST profiles showed specific Italian clusters and a clear separation between pig and wild boar profiles. The wgMLST confirmed the MLST clustering and revealed a high genetic diversity within C. coli population in Italy. Minimum inhibitory concentrations (MIC) of six antibiotics revealed higher resistance in pigs to ciprofloxacin, nalidixic acid, streptomycin and tetracycline, compared to wild boar. In contrast, most strains were susceptible to gentamicin. Worrying levels of multidrug resistance (MDR) were observed mostly in pig isolates. Molecular screening of AMR mechanisms revealed the predominance of gyrA T86I substitution among fluoroquinolone- and quinolone-resistant isolates, and the 23S rRNA A2075G mutation among macrolide-resistant isolates. Other resistance determinants were observed: (i) tet(O) gene was present among tetracycline-resistant isolates; (ii) rpsL and aph(3’)-III genes conferring resistance to aminoglycosides, were identified only in streptomycin or gentamicin-resistant pig isolates; (iii) cmeA, cmeB, cmeC, cmeR genes responsible of pump efflux mechanisms, were observed in almost all the strains; (iv) OXA-61, encoding β-lactamase, was found in the half of the strains. Genotypic and phenotypic AMR profiling was fairly correlated for quinolones/fluoroquinolones. Campylobacter infection is common also in wild boar populations in Italy, suggesting that wild boars could be a reservoir of resistant and multi-resistant Campylobacter species, which may be of public health concern. The present study adds to our knowledge on the epidemiological and ecological traits of this pathogen in domesticated and wild swine.

Health profile of free-range wild boar (Sus scrofa) subpopulations hunted in Santa Catarina State, Brazil

Wild boars represent a potential dissemination source of important pathogens to public and animal health, since they can host several pathogens. This study aimed to evaluate the health profile of wild boars hunted for population control in the state of Santa Catarina (SC), south of Brazil. For this study, tissue and blood samples were collected from 61 wild boars hunted from October 2017 to November 2018. All 61 serum samples were screened for antibodies by different assays, presenting the following seroprevalence: 52.4% for porcine circovirus type 2 (PCV2); 21.3% for Leptospira spp.; 19.7% for Mycoplasma hyopneumoniae; 13.1% for hepatitis E virus (HEV); and 9.8% for influenza A virus (IAV). No seroreaction was observed for Brucella spp. and classical swine fever virus (CSFV). At necropsy, the main lesions observed were evidence of pulmonary metastrongylid parasites, haemorrhagic lymph nodes and white-spotted liver. Histopathological analyses mainly showed interstitial pneumonia, bronchopneumonia and bronchi-associated lymphoid tissue (BALT) hyperplasia. There was a significant association between metastrongylid parasitism and BALT hyperplasia in lungs. Pathological findings of wild boars indicate that the assessed individuals were not exposed to notifiable diseases, such as CSFV, African swine fever virus and foot-and-mouth disease, which cause economic damage by non-tariff trade barriers. However, the detection of antibodies against PCV2 and M. hyopneumoniae, pathogens that impact commercial production, indicates the circulation of these agents, with frequency variation in wild populations. This shows the potential risk of pathogen transmission among domestic swine populations and free-living ones. The detection of antibodies against zoonotic agents such as HEV, IAV and Leptospira spp., other than characterizing the pathogens' circulation in these populations, suggests a potential risk to public health and pig farming, depending on the interactions established with the environment, humans and domestic swine.

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

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

Genetic Diversity of Porcine Circovirus Isolated from Korean Wild Boars

In Korea, three genotypes of porcine circovirus type 2 (PCV2a, PCV2b, and PCV2d) have been identified on domestic pig farms, while two genotypes (PCV2a and PCV2b) have been identified in wild boar populations. Here, we investigated genotype diversity and genotypic shift in 91 PCV2 isolates from 1340 wild boars captured in South Korea between 2013 and 2017. Phylogenetic analyses based on the complete ORF2 showed that the 91 PCV2 strains were detected as four genotypes by qPCR screening assay: PCV2a (2.2%, 2/91), PCV2b (16.5%, 15/91), PCV2d (80.2%, 73/91), and PCV2h (1.1%, 1/91). Only one intergenotype recombinant event was detected between PCV2 ORF2 in wild boars (PCV2b) and domestic pigs (PCV2a). Amino acid positions 86–89 within ORF2, which distinguishes the different genotypes, were conserved in all PCV2 genotypes isolated from South Korean wild boars, including TNKI in PCV2a/PCV2h, SNPR in PCV2b, and SNPL in PCV2d. The estimated nucleotide substitution rates in the ORF2 region of viruses from South Korean wild boars and domestic pigs were 5.8145 × 10⁻⁴ and 4.5838 × 10⁻⁴ substitutions per site per year (s/s/y), respectively. The times to the most recent common ancestor (tMRCA) for South Korean domestic pig PCV2 were 1937 (PCV2a), 1972 (PCV2b), 1999 (PCV2d-1), and 2000 (PCV2d-2). By contrast, the tMRCA for South Korean wild boar PCV2b and PCV2d were 1989 and 2001, respectively. Thus, the PCV2d genotype is prevalent among South Korean wild boars and domestic pigs.

Radioactivity in Calabrian (Southern Italy) Wild Boar Meat

The production chain for game meat is specific and differs from the production chain of meat from domestic livestock. Wild boar meat is a foodstuff consumed in Italy. Wild boars are considered as a reservoir of environmental radionuclides, and the accumulation of radioisotopes can pose a radiological hazard. 40K and 137Cs activity concentrations were measured through HPGe gamma spectrometry in wild boar meat samples, coming from six hygiene points representative of the entire district of Reggio Calabria, South Italy. Experimental values were found to be in the range of (91 ± 11) Bq kg−1 to (117 ± 14) Bq kg−1 for 40K and of (0.09 ± 0.03) Bq kg−1 to (1.61 ± 0.24) Bq kg−1 for 137Cs, respectively. Any possible radiological risk for the population was also estimated. Obtained values are in the range of 2.66 µSv a−1 to 4.00 µSv a−1, much lower than the recommended level for the public (1 mSv a−1).

Detection of Porcine Circovirus 3 in Wildlife Species in Spain

Porcine circovirus 3 (PCV-3) is the third member of the family Circoviridae, genus Circovirus, able to infect swine. A high prevalence of viral DNA has been recorded in wild boars. Recently, PCV-3 DNA was identified in Italian wild ruminants. Based on these previous results, this study assessed the frequency of PCV-3 DNA detection in free-ranging ruminants and Lagomorpha species in Spain. In addition, the genetic characterization of the PCV-3 PCR-positive samples was performed. A total of 801 serum samples, including red deer (Cervus elaphus, [CE]; n = 108), roe deer (Capreolus capreolus, [CC]; n = 87), Pyrenean chamois (Rupicapra pyrenaica, [RP]; n = 133), Iberian ibex (Capra pyrenaica, [CP]; n = 92), mouflon (Ovis aries, [OA]; n = 91), fallow deer (Dama dama, [DD]; n = 104), European rabbit (Oryctolagus cuniculus, [OC]; n = 101), and European hare (Lepus europaeus, [LE]; n = 85) from Catalonia (northeast Spain) were tested by conventional polymerase chain reaction (PCR) and, when positive, sequenced. Overall, PCV-3 DNA was found in three out of 801 analyzed sera (0.37%) corresponding to one red deer (1/108, 0.9%), one mouflon (1/91, 1.1%), and one fallow deer (1/104, 0.96%). None of the samples collected from Lagomorpha species resulted PCR positive. The partial genome sequences detected in positive samples displayed high identity with some PCV-3 sequences detected in wild boars and domestic pigs (99.7% and 100%, respectively). In conclusion, the present study indicated that free-ranging ruminant and Lagomorpha species are not relevant in the epidemiology of PCV-3 in Spain.

Copy Number and Prevalence of Porcine Endogenous Retroviruses (PERVs) in German Wild Boars

Porcine endogenous retroviruses (PERVs) are integrated in the genome of pigs and are transmitted like cellular genes from parents to the offspring. Whereas PERV-A and PERV-B are present in all pigs, PERV-C was found to be in many, but not all pigs. When PERV-C is present, recombination with PERV-A may happen and the PERV-A/C recombinants are characterized by a high replication rate. Until now, nothing has been known about the copy number of PERVs in wild boars and little is known about the prevalence of the phylogenetically youngest PERV-C in ancient wild boars. Here we investigated for the first time the copy number of PERVs in different populations of wild boars in and around Berlin using droplet digital PCR. Copy numbers between 3 and 69 per genome have been measured. A lower number but a higher variability was found compared to domestic pigs, including minipigs reported earlier (Fiebig et al., Xenotransplantation, 2018). The wild boar populations differed genetically and had been isolated during the existence of the Berlin wall. Despite this, the variations in copy number were larger in a single population compared to the differences between the populations. PERV-C was found in all 92 analyzed animals. Differences in the copy number of PERV in different organs of a single wild boar indicate that PERVs are also active in wild boars, replicating and infecting new cells as has been shown in domestic pigs.

Serological Survey on Bacterial and Viral Pathogens in Wild Boars Hunted in Tuscany

Wild boar (Sus scrofa) is one of the large mammals most spread worldwide, including Italy. This animal is highly adaptable, and its population has rapidly increased in many areas in Europe. Central Italy, as well as Tuscany region, is an area particularly suitable for wild boar. In order to verify the role of this animal species in the epidemiology of some important infectious diseases for livestock and humans, a seroepidemiological survey on Brucella spp., Leptospira spp., Mycoplasma hyopneumoniae, Pseudorabies virus (PrV), and Hepatitis E virus (HEV) has been performed on 374 sera collected from wild boar during 2015/2016 and 2016/2017 hunting seasons. Overall, 2 out of 374 sera (0.53%) tested positive to Brucella spp., 33 out of 374 sera (8.82%) tested positive for Leptospira spp., while 79 out of 374 (21.12%) were positive for M. hyopneumoniae. Considering viral pathogens, serology indicated that 107 out of 374 (28.60%) samples scored positive for PrV, while 186 out of 374 (49.73%) for HEV. This investigation indicated that wild boar free ranging in the study area are potential hosts for different etiological agents. This animal could contribute to maintaining and/or disseminating some bacterial or viral pathogens to humans (especially hunters) and domestic animals, especially in free range farms.

Dynamics of Aujeszky's disease virus infection in wild boar in enzootic scenarios

Aujeszky's disease (AD) virus is enzootic in Iberian wild boar, thus posing a threat to the official eradication of AD on extensive domestic pig farms in Spain. Understanding the dynamics and drivers of ADV infection in wild boar will help prevent viral transmission at the wild boar-pig interface. This study analyses the dynamics of ADV infection in wild boar and tests relevant hypotheses in order to identify drivers of ADV infection dynamics. Wild boar sera (N = 971) and oropharyngeal tonsils (TN, N = 549) collected over 11 consecutive years in south-western Spain were tested for ADV antibodies and DNA, respectively. We tested the hypotheses that population immunity modulates the risk of ADV infection (H₁ ) and that detecting ADV DNA in TN is a good proxy of the annual ADV infection pressure (H₂ ). This was done by building logistic regression models that were subsequently employed to test the influence of a series of host population and host individual factors-including predictors of ADV immunity in the population-on the annual risk of new ADV infections and on the presence of ADV DNA in TN. The premise of H₁ was that there would be a negative association between the proportion of ADV antibody-positive wild boar in a given year and the risk of ADV infection of naïve individuals. There was, however, a positive association, and H₁ was, therefore, rejected. If detecting ADV in TN had been a good indicator of ADV infection pressure, a positive association with the proportion of ADV antibody-positive wild boar would have been found. However, this was not the case and H₂ was also rejected. We confirmed that ADV infection is a dynamic phenomenon. The risk of infection with ADV can change considerably between consecutive years, and these changes are positively associated with the proportion of infected wild boar in the population.

Seasonal host life-history processes fuel disease dynamics at different spatial scales

Understanding the drivers underlying disease dynamics is still a major challenge in disease ecology, especially in the case of long-term disease persistence. Even though there is a strong consensus that density-dependent factors play an important role for the spread of diseases, the main drivers are still discussed and, more importantly, might differ between invasion and persistence periods. Here, we analysed long-term outbreak data of classical swine fever, an important disease in both wild boar and livestock, prevalent in the wild boar population from 1993 to 2000 in Mecklenburg-Vorpommern, Germany. We report outbreak characteristics and results from generalized linear mixed models to reveal what factors affected infection risk on both the landscape and the individual level. Spatiotemporal outbreak dynamics showed an initial wave-like spread with high incidence during the invasion period followed by a drop of incidence and an increase in seroprevalence during the persistence period. Velocity of spread increased with time during the first year of outbreak and decreased linearly afterwards, being on average 7.6 km per quarter. Landscape- and individual-level analyses of infection risk indicate contrasting seasonal patterns. During the persistence period, infection risk on the landscape level was highest during autumn and winter seasons, probably related to spatial behaviour such as increased long-distance movements and contacts induced by rutting and escaping movements. In contrast, individual-level infection risk peaked in spring, probably related to the concurrent birth season leading to higher densities, and was significantly higher in piglets than in reproductive animals. Our findings highlight that it is important to investigate both individual- and landscape-level patterns of infection risk to understand long-term persistence of wildlife diseases and to guide respective management actions. Furthermore, we highlight that exploring different temporal aggregation of the data helps to reveal important seasonal patterns, which might be masked otherwise.