European Wild Boar Populations Research Articles

Lack of polymorphism at the MC1R wild-type allele and evidence of domestic allele introgression across European wild boar populations

Domestication promotes the emergence of novel phenotypic and behavioural traits in domesticated animals compared to their wild ancestors. We analysed variation at the melanocortin receptor I (MC1R) and nuclear receptor subfamily 6, group A, member 1 (NR6A1) genes in European wild boar populations, two loci which have been under strong artificial selection during domestication. These loci influence coat colour and number of vertebrae, respectively.A total of 145 wild boars were sampled throughout Europe, to evaluate frequency and spatial distribution of domestic alleles and patterns of hybridization between wild and domestic forms. Most of the wild boars (94%) were homozygous for the European wild-type (E+) MC1R allele. We did not observe any synonymous substitution in the European E+ allele, confirming its monomorphism even in areas known to be hotspots of wild boar genetic diversity. The remaining wild boars (6%) showed genetic introgression of three different European domestic alleles. No Asian MC1R allele was found in our sample.Furthermore, domestic NR6A1 alleles were observed in 6% of wild boars. Considering jointly the two loci analyzed, 11% of boars, sampled all over Europe, showed signs of recent or past introgression in their genome.These data agree with previous investigations on other molecular markers, confirming that, compared to Asian conspecifics, European wild boars have a relatively low genetic diversity, which is locally increased by the introgression of allelic variants from the domestic counterpart.

Spatiotemporal and Ecological Patterns of Mycobacterium microti Infection in Wild Boar (Sus scrofa).

Mycobacterium microti has recently been described as the causative agent of tuberculosis-like lesions in wild boar (Sus scrofa), a reservoir specie of Mycobacterium tuberculosis complex (MTBC) in some European Mediterranean ecosystem. Through a five-year survey on tuberculosis in free-living wild boars, the epidemiological trend of M.microti infections and the host and population risk factors linked with its occurrence were described. Retropharyngeal and mandibular lymph nodes of 3041 hunted wild boars from six different districts were macroscopically inspected. The sex and age of each animal were registered, as well as the animal abundance in each district. Lesions compatible with tuberculosis (190) were collected and analysed using a gyrB PCR-RFLP assay. M.microti was identified directly in 99 tissue samples (Prev=3.26%; 95% CI: 2.67-3.97%), while neither Mycobacterium bovis, nor other members of the MTBC were detected. The probability of being M.microti positive showed spatio-temporal variability, with 26% of increase of risk of being infected for each year. Moreover, a positive effect of wild boar abundance and age on the prevalence was detected. The generalized increase in the European wild boar population, coupled with its sensitivity to M.microti infection, poses a future concern for the identification and management of MTBC members in wild boar.

Genetic relatedness of Brucella suis biovar 2 isolates from hares, wild boars and domestic pigs

Porcine brucellosis generally manifests as disorders in reproductive organs potentially leading to serious losses in the swine industry. Brucella suis biovar 2 is endemic in European wild boar (Sus scrofa) and hare (Lepus europeus, Lepus capensis) populations, thus these species may play a significant role in disease spread and serve as potential sources of infection for domestic pigs. The aim of this study was an epidemiologic analysis of porcine brucellosis in Hungary and a comparative analysis of B. suis bv. 2 strains from Europe using multiple-locus variable-number tandem repeat analysis (MLVA). MLVA-16 and its MLVA-11 subset were used to determine the genotypes of 68 B. suis bv. 2 isolates from Hungary and results were then compared to European MLVA genotypes. The analyses indicated relatively high genetic diversity of B. suis bv. 2 in Hungary. Strains isolated from hares and wild boars from Hungary showed substantial genetic divergence, suggesting separate lineages in each host and no instances of cross species infections. The closest relatives of strains from Hungarian wild boars and domestic pigs were mainly in the isolates from German and Croatian boars and pigs. The assessment of the European MLVA genotypes of wild boar isolates generally showed clustering based on geographic origin. The hare strains were relatively closely related to one another and did not cluster based on geographic origin. The limited relationships between geographic origin and genotype in isolates from hares might be the result of cross-border live animal translocation. The results could also suggest that certain B. suis strains are more adapted to hares. Across Europe, isolates from domestic pigs were closely related to isolates originating from both hares and wild boars, supporting the idea that wild animals are a source of brucellosis in domestic pigs.

Contemporary Genetic Structure, Phylogeography and Past Demographic Processes of Wild Boar Sus scrofa Population in Central and Eastern Europe

The wild boar (Sus scrofa) is one of the most widely distributed mammals in Europe. Its demography was affected by various events in the past and today populations are increasing throughout Europe. We examined genetic diversity, structure and population dynamics of wild boar in Central and Eastern Europe. MtDNA control region (664 bp) was sequenced in 254 wild boar from six countries (Poland, Hungary, Belarus, Ukraine, Moldova and the European part of Russia). We detected 16 haplotypes, all known from previous studies in Europe; 14 of them belonged to European 1 (E1) clade, including 13 haplotypes from E1-C and one from E1-A lineages. Two haplotypes belonged respectively to the East Asian and the Near Eastern clade. Both haplotypes were found in Russia and most probably originated from the documented translocations of wild boar. The studied populations showed moderate haplotype (0.714±0.023) and low nucleotide diversity (0.003±0.002). SAMOVA grouped the genetic structuring of Central and Eastern European wild boar into three subpopulations, comprising of: (1) north-eastern Belarus and the European part of Russia, (2) Poland, Ukraine, Moldova and most of Belarus, and (3) Hungary. The multimodal mismatch distribution, Fu's Fs index, Bayesian skyline plot and the high occurrence of shared haplotypes among populations did not suggest strong demographic fluctuations in wild boar numbers in the Holocene and pre-Holocene times. This study showed relatively weak genetic diversity and structure in Central and Eastern European wild boar populations and underlined gaps in our knowledge on the role of southern refugia and demographic processes shaping genetic diversity of wild boar in this part of Europe.

Presence ofSalmonellaspp.,Yersinia enterocolitica,Yersinia pseudotuberculosisandEscherichia coliO157:H7 in wild boars

The European wild boar populations are growing and spreading to new areas, which might constitute a threat to public health, since wild boar can harbour pathogens with the potential to cause serious illness in humans. Tonsils, ileocaecal lymph nodes and faecal samples were collected from 88 Swedish wild boars and analysed for the presence of the zoonotic pathogens Salmonella spp., Yersinia enterocolitica, Y. pseudotuberculosis and enterohaemorrhagic Escherichia coli O157:H7 (EHEC). A combination of cultivation and polymerase chain reaction (PCR) analysis was used and overall, 20% of sampled individuals tested positive for Y. enterocolitica, 20% for Y. pseudotuberculosis and 10% for Salmonella spp. A total of 41% of sampled individuals tested positive for one or more of these three pathogens. No EHEC were detected. Samples PCR-positive for Salmonella spp. were cultivated further and six isolates were obtained, belonging to Salmonella enterica subspecies enterica and subspecies diarizone. The pathogens were most commonly detected in tonsil samples.

Genetic evidence for introgression between domestic pigs and wild boars (Sus scrofa) in Belgium and Luxembourg: a comparative approach with multiple marker systems

Hybridization between wild species and their domestic relatives can be an important conservation and management problem. Genetic purity of the wild species is desirable per se and the phenomenon can have unpredictable evolutionary consequences. Declining European wild boar populations were frequently restocked with farmed wild boars that sometimes had been crossed with domestic pigs. We used simple polymerase chain reaction-based diagnostic tests to detect the presence of mitochondrial DNA and coat colour alleles of domestic origin in wild boars from Belgium, Luxembourg, and western Germany. Microsatellite genotypes were used to test for genetic admixture between the wild boars and domestic pigs. Although almost one-third of all Luxembourg wild boars carried Asian mitochondrial DNA haplotypes originating from domestic pigs, microsatellite-based clustering only identified four putatively admixed individuals in Luxembourg. By contrast, clustering identified wild boar × domestic hybrids in most sampling locations in Belgium. We interpret these results as evidence of releases of hybrid captive-reared wild boars. Our results emphasize the need (if working with classical markers) to use different systems to obtain an understanding as to whether hybridization between wild and domestic relatives might have affected the genetic make-up of a local population. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 104–115.

A High Throughput Genotyping Approach Reveals Distinctive Autosomal Genetic Signatures for European and Near Eastern Wild Boar

The lack of a Near Eastern genetic signature in modern European porcine breeds indicates that, although domestic pigs from the Fertile Crescent entered Europe during the Neolithic, they were completely replaced by their European counterparts in a short window of time. Whilst the absence of such genetic signature has been convincingly demonstrated at the mitochondrial level, variation at the autosomal genomes of European and Near Eastern Sus scrofa has not been compared yet. Herewith, we have explored the genetic relationships among 43 wild boar from Europe (N = 21), Near East (N = 19) and Korea (N = 3), and 40 Iberian (N = 16), Canarian (N = 4) and Mangalitza (N = 20) pigs by using a high throughput SNP genotyping platform. After data filtering, 37,167 autosomal SNPs were used to perform population genetics analyses. A multidimensional scaling plot based on genome-wide identity-by-state pairwise distances inferred with PLINK showed that Near Eastern and European wild boar populations are genetically differentiated. Maximum likelihood trees built with TreeMix supported this conclusion i.e. an early population split between Near Eastern and European Sus scrofa was observed. Moreover, analysis of the data with Structure evidenced that the sampled Iberian, Canarian and Mangalitza pigs did not carry any autosomal signature compatible with a Near Eastern ancestry, a finding that agrees well with previous mitochondrial studies.

Oesophagostominae (Nematoda: Chabertiidae) Of Suids From Southern Poland / Oesophagostominae (Nematoda: Chabertiidae) u świniowatych z Polski południowej

Abstract Until recently, the genus Oesophagostomum was the only Oesophagostominae occurring commonly in both domestic and wild suids of Europe. A few years ago, an alien oesophagostomin nematode Bourgelatia diducta was recorded in the wild boar population from southern Poland, and Vietnamese potbellied pig was blamed for introduction of this Far Eastern parasite. Apart from wild boars kept in captivity for meat production purposes, Vietnamese potbellied pigs can be raised in extensive, organic, or especially agrotourism farms, which constitutes an infection hazard to domestic pigs. The aim of the research was to determine and compare species composition of Oesophagostominae in wild boars from the natural environment, and in domestic pigs from extensively managed farms, located in the area where B. diducta was previously noted for the first time. A postmortem examination of the large intestines of 25 wild boars and 20 domestic pigs, each from different smallholdings, was conducted in the autumn and winter season of 2010- 2011. Oesophagostomum dentatum with coexisting O. quadrispinulatum were ascertained in swine, whereas the sole Bourgelatia diducta was recorded in wild boars. All the parasites occurred commonly in their hosts, with the prevalence of 80, 50 and 32% for O. dentatum, O. quadrispinulatum and B. diducta, respectively. Mean number of worms was many-fold higher in pigs, reaching 181 (range 1 to 2500) specimens in individual host, versus 3 (1-6) parasites in wild boars. A presumable influence of the alien nematode species on the European wild boar population as well as the potential for further spread of the parasite are elucidated

Genome‐wide single nucleotide polymorphism analysis reveals recent genetic introgression from domestic pigs into Northwest European wild boar populations

Present-day genetic introgression from domestic pigs into European wild boar has been suggested in various studies. However, no hybrids have been identified beyond doubt mainly because available methods were unable to quantify the extent of introgression and rule out natural processes. Genetic introgression from domestic pigs may have far-reaching ecological consequences by altering traits like the reproduction rate or immunology of wild boar. In this study, we demonstrate a novel approach to investigate genetic introgression in a Northwest (NW) European wild boar data set using a genome-wide single nucleotide polymorphism (SNP) assay developed for domestic pigs. We quantified the extent of introgression using allele frequency spectrum analysis, in silico hybridization simulations and genome distribution patterns of introgressed SNPs. Levels of recent introgression in the study area were expected to be low, as pig farming practices are prevailingly intensive and indoors. However, evidence was found for geographically widespread presence of domestic pig SNPs in 10% of analysed wild boar. This was supported by the identification of two different pig mitochondrial DNA haplotypes in three of the identified hybrid wild boar, suggesting that introgression had occurred from multiple sources (pig breeds). In silico hybridization simulations showed that the level of introgression in the identified hybrid wild boar is equivalent to first-generation hybrids until fifth-generation backcrosses with wild boar. The distribution pattern of introgressed SNPs supported these assignments in four of nine hybrids. The other five hybrids are considered advanced-generation hybrids, resulting from interbreeding among hybrid individuals. Three of nine hybrids were genetically associated with a different wild boar population than the one in which they were sampled. This discrepancy suggests that genetic introgression has occurred through the escape or release of an already hybridized farmed wild boar stock. We conclude that genetic introgression from domestic pigs into NW European wild boar populations is more recent and more common than expected and that genome-wide SNP analysis is a promising tool to quantify recent hybridization in free-living populations.

A serological and bacteriological survey of brucellosis in wild boar (Sus scrofa) in Belgium

BackgroundBrucellosis is frequently reported among wild boar populations in Europe. The aim of the study was to assess the epidemiological situation in Belgium, regarding the steady increase of wild boar populations over the last decades. Several serological tests were used and compared with culture and IS711 polymerase chain reaction (PCR), to determine the most suitable combination of diagnostic tools for conducting a successful prevalence study in wildlife.ResultsAn indirect enzyme-linked immunosorbent assay (iELISA) was used on 1168 sera from hunter-killed wild boar sampled between 2003 and 2007 in 4 natural regions of southern Belgium. Results gave an apparent prevalence of 54.88% (95% CI 52.03-57.73). Prevalence was significantly affected by age and by the year of study, but not by sex nor by the region of sampling. The relative sensitivities of the complement fixation test (CFT), the Rose Bengal test (RBT), and the slow agglutination test (SAT) versus the iELISA differed widely between tests, reaching 62.67%, 46.68%, and 34.77%, respectively. The relative specificities of the CFT, RBT and SAT versus the iELISA were respectively 99.01%, 92.49%, and 99.1%. From seropositive animals (iELISA), 9% were positive by culture and 24% by PCR when testing spleen and/or tonsils. Sensitivity of the PCR was higher on tonsils than on spleen. All bacterial isolates were identified as Brucella suis biovar 2.ConclusionsBrucellosis is widespread among wild boar in southern Belgium, with seroprevalences having increased over ten years, and constitutes a growing risk of spillback to outdoor-farmed pig herds. The iELISA showed a better sensitivity than the CFT, RBT and SAT. Serological tests must be associated with direct diagnosis and PCR proved more sensitive than culture under wildlife sampling conditions. Spleen and tonsils are lymphoid tissues usually sampled in multi-disease monitoring programs. They remain top-grade organs for direct diagnosis of brucellosis, with a preference for tonsils.

A Gustatory Repellent for Protection of Agricultural Land from Wild Boar Damage: An Investigation on Effectiveness

Following the spread and increase of wild boar populations in Europe during the last decades, conflicts with humans have intensified also in Switzerland. Damage to crops and grassland augmented considerably and became unacceptable. Farmers and authorities are highly interested in efficient alternatives to the installation of costly and time consuming electric fences for crop protection. In the present study we investigated the effectiveness of a gustative repellent in field experiments with free-ranging wild boars in clover sowings, meadows, and wheat fields. Although we observed a slight trend towards a damage reduction, the results show, that the repellent was not able to prevent damage at a significant level. We further could not detect any area avoidance by the wild boars as a response to the repellent. On the basis of our findings we conclude that gustative repellents relying on learned avoidance as a consequence of negative experience are not a promising means for protection of crops and grassland from wild boar damage. We further discuss the effects of different agricultural crops and the anthropogenic influence on the frequency of damage.

Disease severity declines over time after a wild boar population has been affected by classical swine fever—Legend or actual epidemiological process?

Classical swine fever (CSF) is a severe multi-systemic disease that can affect both domestic pigs and wild boar. Past outbreaks in European wild boar involved high-virulent CSF virus (CSFV) strains and were mostly self-limiting. In these cases, morbidity and mortality rates were high in the affected regions. In contrast, endemic infections have been observed in several European wild boar populations in recent decades. Morbidity and mortality rates were much lower despite the fact that outbreaks were still detected via diseased or fallen animals. The virus strains involved were mostly classified as genotype 2.3 strains of moderate virulence causing age-dependent disease outcomes. The mechanisms leading to the establishment and perpetuation of endemicity are still not fully understood, but the factor “moderate virulence” seems to be of considerable importance.In this study, we aim to clarify whether the perception of declined ‘CSF severity’ could hypothetically reflect the adaptation of an initially high-virulent virus or whether this might be better explained as a misinterpretation of observations. A mechanistic eco-epidemiological model was employed to follow up a highly virulent strain of CSFV introduced into large connected wild boar populations. In the model, the virulence of the CSF virus is represented by case mortality and life expectancy after lethal infection. Allowing for small stochastic variation, these two characteristics of the virus are passed on with every new simulated infection that occurs.Model analysis revealed a decrease from high to moderate case mortality within a few years of simulated perpetuation of the virus. The resulting mortality corresponded to the level where the population average of the infectious period and the basic reproduction number of the disease were maximal. This shift in virulence was sufficient to prolong virus circulation considerably beyond the epidemic phase of the simulated outbreaks. Alternative mechanistic explanations for the decrease in disease severity in a CSF-affected wild boar population were evaluated in the light of the simulation experiments and the available epidemiological or virological evidence.In conclusion, the current virus isolates of subgroup 2.3 might be the ideally adapted variants of the CSF virus for long-term perpetuation in wildlife and indeed may have evolved (once) during past outbreaks in large populations. A repeated perception of a declining severity of disease pattern during the course of a CSF outbreak, however, favours the explanation based on monitoring and detection biases rather than repeated observation of selection against highly virulent virus during the time of virus perpetuation.

Efficiency of spatio-temporal vaccination regimes in wildlife populations under different viral constraints

Classical Swine Fever (CSF) is considered an endemic disease in European wild boar populations. In view of the high economic impact of the introduction of the virus into domestic pig units, huge efforts are invested in the preventive control of CSF in wild boar populations. Recent European Community guidelines favour oral mass vaccination against CSF in wild boar populations. The guidelines are explicit on the temporal structure of the vaccination protocol, but little is known about the efficacy of different spatial application schemes, or how they relate to outbreak dynamics.We use a spatially explicit, individual-based wild boar model that represents the ecology of the hosts and the epidemiology of CSF, both on a regional scale and on the level of individual course of infection. We simulate adaptive spatial vaccination schemes accounting for the acute spread of an outbreak while using the temporal vaccination protocol proposed in the Community guidelines.Vaccination was found to be beneficial in a wide range of scenarios. We show that the short-term proactive component of a vaccination strategy is not only as decisive as short-term continuity, but also that it can outcompete alternative practices while being practically feasible. Furthermore, we show that under certain virus-host conditions vaccination might actually contribute to disease persistence in local populations.

Reproductive performance of wild boar females in Portugal

Reproductive tracts of 214 female wild boars collected in Central Portugal between October and February over the period 1997 to 2001 were examined. From this material, we were able to determine reproductive phenology (conception and birth periods) as well as age and weight of sows at puberty, ovulation rates of adults, foetal sex ratio, levels of intrauterine mortality, final litter size and postnatal mortality. Differences between year, region, age and body weight were analysed. A total of 66.8% of the females examined were gestating or lactating and 96.3% of these weighed >40 kg. The highest proportions of pregnant sows were found in the adult age/weight classes (74%). None of the juvenile females (1 year old and younger) were lactating and only 7% was pregnant. The average number of foetuses/female (4.1 ± 1.2SD) and that of corpora lutea per female (4.6 ± 1.7SD) increased from lighter and younger to heavier and older wild sows. Foetal sex ratio was biased towards males (1.3:1). Observed intrauterine mortality rate (9.7%) and postnatal mortality (6.3%) were among the lowest recorded in European wild boar populations. The productivity rate of the Central Portuguese wild boar population was calculated as 1.1 young per individual in the population. Conception and birth periods did not differ significantly between the considered 4 years. Birth synchronisation was pronounced in all the years, with a peak of births occurring in March.

Characterization of pseudorabies virus of wild boar origin from Europe

Pseudorabies virus (PrV) infections appear to be more widely distributed in the European wild boar (Sus scrofa) population than assumed. In Europe, attempts to isolate and characterize the causative agents have been limited so far. We therefore collected and examined a total of 35 PrV isolates obtained from wild boar or hunting dogs in Germany, France, Spain, Italy, Slovakia and Hungary between 1993 and 2008. Restriction enzyme analysis of genomic DNA using BamHI showed that all isolates, except one, belonged to genogroup I but different subtypes were evident. For further investigations of the phylogenetic relationships, a 732-bp fragment of the glycoprotein C (gC) gene was amplified by PCR. Sequence analysis revealed about 40 variant positions within this fragment. Comparison of the nucleotide sequences supported the separation into a clade containing isolates from North-Rhine Westphalia, Rhineland-Palatinate (Germany), France and Spain (clade B) and an apparently more variable clade comprising isolates from Brandenburg, Baden-Wurttemberg, Saxony, Saxony-Anhalt (Germany), Slovakia, Hungary, Italy and France (clade A).

Multiple Asian pig origins revealed through genomic analyses

Previous mitochondrial DNA (mtDNA) studies have suggested that European and Asian pig populations were derived through multiple domestication events. We investigated whether domestic pig populations were derived from distinct ancestors within their respective regions, using eight domestic breeds (five European and three Asian), and also European and Asian wild boar populations. Genomic analyses utilized 21 microsatellite markers (MS) selected for their distribution across the pig genome in addition to the mtDNA D-loop region. The number of alleles per MS loci ranged from 8 (Sw2008) to 16 (S0097 and S0218). Few significant departures from Hardy-Weinberg equilibrium were detected, suggesting the absence of heterozygote deficiencies. Analyses within populations revealed observed mean heterozygosity from 0.48 (Erhualian) to 0.68 (Dutch WB) and an expected mean heterozygosity from 0.53 (Hampshire) to 0.80 (Japanese WB) with effective alleles ranging from 2.28 (Hampshire) to 3.74 (French WB). Wild boar populations demonstrated a higher level of heterozygosity than domestic breeds. Genetic differentiation estimated by fixation indices (F(ST)) ranged from 0.021 (Yorkshire and Duroc) to 0.410 (Meishan and Hampshire) and was consistent with previous mtDNA analysis. Both phylogenetic and principal component analyses revealed a distinct separation of European and Asian derived populations with tight clustering of the European domestic breeds. Conversely, the use of both MS and mtDNA clarified that the Asian populations were comprised of three groups, one represented by Erhualian and Meishan breed, the second represented by Lanyu pigs and the third represented by the Asian wild boars. The current findings support the hypothesis that Asian domestic populations were derived from multiple Asian ancestral origins whereas the European domestic populations represent a single ancestral European lineage.

Expression of immunoregulatory genes in peripheral blood mononuclear cells of European wild boar immunized with BCG

The objective of this study was to analyze the expression of immunoregulatory genes in European wild boar ( Sus scrofa) immunized with BCG. Eighteen immunoregulatory genes were selected for expression analysis based on their role in host immune response during tuberculosis and/or for their association with resistance to bovine tuberculosis in European wild boar populations. Initially, mRNA levels were analyzed by quantitative real-time reverse transcription PCR (qRT-PCR) in spleen samples from Mycobacterium bovis-infected ( N = 18) and uninfected ( N = 22) European wild boar. Statistical analysis of qRT-PCR data revealed that four genes, complement component C3, IFN-gamma, IL-4 and RANTES were downregulated in infected animals ( P < 0.05). These genes were selected for analysis of mRNA levels in peripheral blood mononuclear cells (PBMCs) from seven wild boar experimentally immunized with BCG and seven non-immunized controls. Blood was collected at 0, 5, 13 and 25 weeks post-immunization (wpi). The mRNA levels of IFN-gamma and C3 showed a peak (>15-fold increase) at 5 wpi, whereas transcripts for RANTES and IL-4 showed a peak (>2-fold increase) at 13 wpi in BCG-immunized animals when compared to non-immunized controls. The pattern of expression of these genes over the time provides the first description of BCG specific immune response in European wild boar. These results provide new insights into the molecular basis of wild boar response to M. bovis infection and BCG vaccination and may be used to monitor BCG vaccination in this species.

Ancient vs. recent processes as factors shaping the genetic variation of the European wild boar: are the effects of the last glaciation still detectable?

The European wild boar is an important game species, subjected to local extinctions and translocations in the past, and currently enormously and worryingly expanding in some areas where management is urgently required. Understanding the relative roles of ancient and recent events in shaping the genetic structure of this species is therefore not only an interesting scientific issue, but it represents also the basis for addressing future management strategies. In addition, several pig breeds descend from the European wild boar, but the geographical location of the domestication area(s) and the possible introgression of pig genomes into wild populations are still open questions. Here, we analysed the genetic variation in different wild boar populations in Europe. Ten polymorphic microsatellites were typed in 252 wild boars and the mtDNA control region was sequenced in a subset of 145 individuals. Some samples from different pig breeds were also analysed. Our results, which were obtained considering also 612 published mtDNA sequences, suggest that (i) most populations are similarly differentiated, but the major discontinuity is found along the Alps; (ii) except for the Italian populations, European wild boars show the signature of a postglacial demographic expansion; (iii) Italian populations seem to preserve a high proportion of preglaciation diversity; (iv) the demographic decline which occurred in some areas in the last few centuries did not produce a noticeable reduction of genetic variation; (v) signs of human-mediated gene flow among populations are weak, although in some regions the effects of translocations are detectable and a low degree of pig introgression can be identified; (vi) the hypothesis of an independent domestication centre in Italy is not supported by our data, which in turn confirm that Central European wild boar might have represented an important source for domestic breeds. We can therefore conclude that recent human activities had a limited effect on the wild boar genetic structure. It follows that areas with high variation and differentiation represent natural reservoirs of genetic diversity to be protected avoiding translocations. In this context controlling some populations by hunting is not expected to affect significantly genetic variation in this species.

Differential Anti-Influenza Activity among Allelic Variants at TheSus Scrofa Mx1Locus

A promising way to oppose infectious challenges would be to improve the resistance of the target species through genetic selection. Theoretically, a candidate gene is available against influenza viruses since a resistance trait was fortuitously discovered in the A2G mouse strain. This trait was demonstrated to be correlated with the expression of a specific isoform of the type I interferon (IFN)-dependent protein MX, an isoform coded by a specific allele at the mouse Mx1 locus. Two allelic polymorphisms were described recently in the Sus scrofa homologous gene. In this study, the frequencies and distribution of both alleles were evaluated among European domestic pig and wild boar populations by PCR-RFLP, and the anti-influenza activity conferred by both MX1 isoforms was evaluated in vitro using transfection of Vero cells followed by flow cytometric determination of the fraction of influenza virus-infected cells among MX-producing and MX-nonproducing cell populations. A significant difference in the anti-influenza activity brought by the two MX1 isoforms was demonstrated, which suggests that a significant improvement of innate resistance of pigs by genetic selection might be feasible provided the differences found here in vitro are epidemiologically relevant in vivo.

Torque teno virus (TTV) is highly prevalent in the European wild boar ( Sus scrofa)

The present study represents the first survey of Torque teno virus (TTV) prevalence in European wild boar ( Sus scrofa). The prevalence of two distinct TTV genogroups in 178 Spanish wild boar sera from different geographic regions, management conditions, gender and age was determined by a nested PCR method. The overall prevalence of TTV genogroups was 84% (58% for genogroup 1 and 66% for genogroup 2), and differences between genogroup prevalence were observed depending on the geographical region analysed. Significantly higher prevalence for TTV genogroup 2 was found in fenced managed wild boar, juvenile animals and females. No other significant differences in TTV genogroup prevalence were observed. The phylogenetic analysis of nucleotide sequences obtained from the untranslated region of selected samples revealed that the same TTV genogroups are infecting wild boar and domestic pig. The results indicate that TTV is apparently ubiquitous in European wild boar populations.