Detection of hybrids between wild boars (Sus scrofa scrofa) and domestic pigs (Sus scrofa f. domestica) in Greece, using the PCR-RFLP method on melanocortin-1 receptor (MC1R) mutations

Motivation and Habits of a Wild Boar-Hunting Community

The wild boar (Sus scrofa) is a widespread ungulate, the populations of which have recently increased throughout most of its range. This increase has caused negative impacts on ecosystems, biodiversity, and society. Nowadays, the wild boar is considered both a valuable game and a pest. Wildlife managers need to know the habits and motivations of wild boar hunters, a key stakeholder group, for effectively managing this controversial mammal. We carried out face-to-face interviews with 134 wild boar hunters in the Evros Prefecture, in the Region of Eastern Macedonia and Thrace, northern Greece to determine their hunting habits and their motivation for hunting. Most hunters owned a hunting dog (84.3%), hunted in groups of eight to nine people for 48 days, traveled 60 km, stayed outdoors for 4 nights, and spent weekly EUR 61 on average in each hunting season. Two motivations for wild boar hunting were prominent among the hunters (assessed on a 5-point scale; 1 = strongly disagree to 5 = strongly agree): a strong recreation motivation (hunting as a recreational activity; mean score 4.159 ± 1.144 SD) and a considerable utility motivation (hunting for its use values; 3.404 ± 1.11). Both recreation and utility motivations were positively associated with the preference for further increases in wild boar populations. Sociodemographic characteristics and hunting habits variously affected motivations and preferred future population trends. The findings revealed specific habits and strong motivations among hunters. Such findings will be useful for designing and implementing education and outreach programs for informing hunters about the negative impacts of wild boars and the need for their control. The participation of hunters in the management process will be critical for its success.

Signatures of Admixture and Genetic Uniqueness in the Autochthonous Greek Black Pig Breed Deduced from Gene Polymorphisms Affecting Domestication-Derived Traits

The Greek Black Pig (or Greek Pig) is the only recognized autochthonous pig breed raised in Greece, usually in extensive or semi-extensive production systems. According to its name, the characteristic breed coat color is solid black. In this study, with the aim to start a systematic genetic characterization of the Greek Black Pig breed, we investigated polymorphisms in major genes well known to affect exterior and production traits (MC1R, KIT, NR6A1, VRTN and IGF2) and compared these data with population genetic information available in other Mediterranean and Western Balkan pig breeds and wild boars. None of the investigated gene markers were fixed for one allele, suggesting that, in the past, this breed experienced introgression from wild boars and admixture from cosmopolitan pig breeds, enriching the breed genetic pool that should be further investigated to design appropriate conservation genetic strategies. We identified a new MC1R allele, containing two missense mutations already reported in two other independent alleles, but here present in the same haplotype. This allele might be useful to disclose biological information that can lead to better understanding the cascade transmission of signals to produce melanin pigments. This study demonstrated that autochthonous genetic resources can be an interesting reservoir of unexpected genetic variants.

Current Analytical Methods and Research Trends Are Used to Identify Domestic Pig and Wild Boar DNA in Meat and Meat Products

The pig, one of the most important livestock species, is a meaningful source of global meat production. It is necessary, however, to prove whether a food product that a discerning customer selects in a store is actually made from pork or venison, or does not contain it at all. The problem of food authenticity is widespread worldwide, and cases of meat adulteration have accelerated the development of food and the identification methods of feed species. It is worth noting that several different molecular biology techniques can identify a porcine component. However, the precise differentiation between wild boar and a domestic pig in meat products is still challenging. This paper presents the current state of knowledge concerning the species identification of the domestic pig and wild boar DNA in meat and its products.

Introgressive hybridisation between domestic pigs (Sus scrofa domesticus) and endemic Corsican wild boars (S. s. meridionalis): effects of human-mediated interventions

Owing to the intensified domestication process with artificial trait selection, introgressive hybridisation between domestic and wild species poses a management problem. Traditional free-range livestock husbandry, as practiced in Corsica and Sardinia, is known to facilitate hybridisation between wild boars and domestic pigs (Sus scrofa). Here, we assessed the genetic distinctness and genome-wide domestic pig ancestry levels of the Corsican wild boar subspecies S. s. meridionalis, with reference to its Sardinian conspecifics, employing a genome-wide single nucleotide polymorphism (SNP) assay and mitochondrial control region (mtCR) haplotypes. We also assessed the reliance of morphological criteria and the melanocortin-1 receptor (MC1R) coat colour gene to identify individuals with domestic introgression. While Corsican wild boars showed closest affinity to Sardinian and Italian wild boars compared to other European populations based on principal component analysis, the observation of previously undescribed mtCR haplotypes and high levels of nuclear divergence (Weir’s θ > 0.14) highlighted the genetic distinctness of Corsican S. s. meridionalis. Across three complementary analyses of mixed ancestry (i.e., STRUCTURE, PCADMIX, and ELAI), proportions of domestic pig ancestry were estimated at 9.5% in Corsican wild boars, which was significantly higher than in wild boars in Sardinia, where free-range pig keeping was banned in 2012. Comparison of morphologically pure- and hybrid-looking Corsican wild boars suggested a weak correlation between morphological criteria and genome-wide domestic pig ancestry. The study highlights the usefulness of molecular markers to assess the direct impacts of management practices on gene flow between domestic and wild species.

Genetic Diversity, Admixture and Analysis of Homozygous-by-Descent (HBD) Segments of Russian Wild Boar

The wild boar is the wild ancestor of the domestic pig and one of the most common species of ungulates. At the beginning of the 20th century, the wild boar was practically exterminated in the European part of Russia. In the period 1935-1988, 7705 boars were caught in various regions of the European part of Russia, the Far East, Ukraine, Belarus, Kyrgyzstan, Kazakhstan, Latvia, Lithuania, Estonia, Tajikistan and resettled in the territory of Russia. Asian and European wild boars dwell the territory of Russia. The aim of our research was to study the genetic diversity and structure of wild boar populations in different regions of Russia using genome-wide genotyping. We have determined the genetic distances, population structure, parameters of genetic diversity and significantly expanded our understanding of the genetic state of the Russian wild boar. For the first time, we calculated autozygosity of the wild boar of the European and Asian subspecies using Homozygous-by-Descent (HBD) Segments analysis, which is important in terms of population recovery. We also found evidence of hybridization between Russian wild boar and domestic pigs. A group of European wild boars showed introgression of the Asian boar into population. The mean level of the inbreeding coefficient in European wild boar was higher than in Asian wild boar, and combined groups of the European boar had higher inbreeding coefficient than Russian wild boars. These results obtained can be used in population management.

Consequences of Hybridization in Mammals: A Systematic Review

Hybridization, defined as breeding between two distinct taxonomic units, can have an important effect on the evolutionary patterns in cross-breeding taxa. Although interspecific hybridization has frequently been considered as a maladaptive process, which threatens species genetic integrity and survival via genetic swamping and outbreeding depression, in some cases hybridization can introduce novel adaptive variation and increase fitness. Most studies to date focused on documenting hybridization events and analyzing their causes, while relatively little is known about the consequences of hybridization and its impact on the parental species. To address this knowledge gap, we conducted a systematic review of studies on hybridization in mammals published in 2010-2021, and identified 115 relevant studies. Of 13 categories of hybridization consequences described in these studies, the most common negative consequence (21% of studies) was genetic swamping and the most common positive consequence (8%) was the gain of novel adaptive variation. The total frequency of negative consequences (49%) was higher than positive (13%) and neutral (38%) consequences. These frequencies are biased by the detection possibilities of microsatellite loci, the most common genetic markers used in the papers assessed. As negative outcomes are typically easier to demonstrate than positive ones (e.g., extinction vs hybrid speciation), they may be over-represented in publications. Transition towards genomic studies involving both neutral and adaptive variation will provide a better insight into the real impacts of hybridization.

Differentiating Pigs from Wild Boars Based on NR6A1 and MC1R Gene Polymorphisms

Simple Summary

Wild boar meat is much more expensive than pork. Therefore, there are cases when pork is added to wild boar meat products, but this information is not included on the product label. Currently, there is no fully reliable method that would allow the identification of wild boar and domestic swine products. In this study, we tested the possibility of distinguishing two subspecies using polymorphisms within the MC1R and NR6A1 genes. For this purpose, we used two techniques commonly used in molecular biology, PCR-RFLP and Real-time PCR.

Abstract

This preliminary study aimed to differentiate domestic pigs from wild boars based on MC1R and NR6A1 polymorphisms and to identify admixture between these genomes. We studied samples obtained from wild boars from two regions of Poland and five pig breeds: Polish Landrace, Polish Large White, Złotnicka White, Pulawska and Duroc. Along the MC1R gene sequence, we identified four polymorphic loci comprising three codons. The “wild type” allele was primarily found in wild boar but also in the Duroc and Złotnicka White breeds. Non-wild type alleles were identified in the vast majority of domestic pig samples and in two wild boar samples. Based on MC1R profiles, we conducted a population study, and revealed admixture between both genomes using STRUCTURE and NETWORK Software. Interestingly, an allelic discrimination assay with NR6A1 g.748C > T TaqMan probes revealed a clear separation of samples into two groups: wild boar samples representing the C allele and domestic breeds representing the T allele. Based on the obtained results, we conclude that NR6A1 g.748C > T is an effective marker for differentiating between wild boars and domestic pigs, where this is supported by MC1R data, to identify admixed profiles. We recommend that a larger sample of genomes is studied to verify this method.

Wild pigs (Sus scrofa) population as reservoirs for deleterious mutations in the RYR1 gene associated with Porcine Stress Syndrome

Porcine Stress Syndrome (PSS) is a disorder codified by the ryanodine receptor 1 gene (RYR1) and affects both animal welfare and the quality of the meat product. As a consequence, individuals with this syndrome generate great worldwide economic losses in the porcine industry. In Argentina, the Buenos Aires Province is the most involved on this activity, and productions are to be in open field with a higher frequency of pigs with diverse pathologies. On the other hand, the biggest and oldest wild pigs population is located on the Atlantic coast of Buenos Aires Province, which presents a continuous bidirectional flow of individuals with the productive areas nearby. The aim of this study is to detect the presence of the RYR1 deleterious allele in the wild population from the Atlantic coast of Buenos Aires, in order to evaluate its possible role as a genetic reservoir for said allele. For this purpose, 106 wild pigs from 28 sites were studied, finding a 6.6% of carrier individuals, indicating that the wild population is not free of this allele. This constitutes the first analysis to detect the presence of the RYR1 deleterious allele, associated to the PSS in wild pigs from Argentina, being one of the few studies to report it worldwide and suggesting wild pigs populations to be a possible genetic reservoir for this disease.

High Seroprevalence of Hepatitis E Virus Infection Among East Balkan Swine (Sus scrofa) in Bulgaria: Preliminary Results

The East Balkan swine (Sus scrofa) is the only aboriginal pig breed in Bulgaria, and it is indigenous to the eastern part of the country. The aim of the present study was to investigate East Balkan swine (EBS) in Bulgaria for serological evidence of hepatitis E virus (HEV). Sera from 171 swine from two parts of the country (northeastern and southeastern) were tested for anti-HEV IgG antibodies. The overall HEV seroprevalence was 82.5% (141/171), and for weaners it was 77.2% (44/57), for fattening pigs 79.0% (45/57), and for adults 91.2% (52/57). HEV positivity was higher in fattening pigs and adults compared to weaners: OR = 1.108 (95% CI: 0.456–2.692) and OR = 3.073 (95% CI: 1.016–9.294), respectively. This study provides the first evidence of exposure to HEV in EBS from Bulgaria.

Matching STR and SNP genotyping to discriminate between wild boar, domestic pigs and their recent hybrids for forensic purposes

The genetic discrimination between phylogenetically close taxa can be challenging if their gene pools are not differentiated and there are many shared polymorphisms. The gene flow between wild boar (Sus scrofa) and domestic pig (S. s. domesticus) has never been interrupted from domestication onwards, due to non-stop natural and human-mediated crossbreeding. To date there are no individual genetic markers that are able to distinguish between the two forms, nor even to identify effectively their hybrids. We developed a combined molecular protocol based on multiplex porcine-specific STR-profiling system and new real time PCR-based assays of single polymorphisms in the NR6A1 and MC1R genes to gain high diagnostic power in the differentiation of wild boar, pig and hybrids for forensic purposes. The combined approach correctly assigned individuals to one or the other parental gene pool and identified admixed genotypes. Evidence was found for substantial reduction of false negative results by using multiple marker systems jointly, compared to their use individually. Our protocol is a powerful and cost-effective diagnostic tool that can easily be adopted by most forensic laboratories to assist authorities contrast food adulteration, assure veterinary public health and fight against wildlife crimes, like poaching and illegal detention of wild animals.

Signatures of de-domestication in autochthonous pig breeds and of domestication in wild boar populations from MC1R and NR6A1 allele distribution

Autochthonous pig breeds are usually reared in extensive or semi-extensive production systems that might facilitate contact with wild boars and, thus, reciprocal genetic exchanges. In this study, we analysed variants in the melanocortin 1 receptor (MC1R) gene (which cause different coat colour phenotypes) and in the nuclear receptor subfamily 6 group A member 1 (NR6A1) gene (associated with increased vertebral number) in 712 pigs of 12 local pig breeds raised in Italy (Apulo-Calabrese, Casertana, Cinta Senese, Mora Romagnola, Nero Siciliano and Sarda) and south-eastern European countries (Krškopolje from Slovenia, Black Slavonian and Turopolje from Croatia, Mangalitsa and Moravka from Serbia and East Balkan Swine from Bulgaria) and compared the data with the genetic variability at these loci investigated in 229 wild boars from populations spread in the same macro-geographic areas. None of the autochthonous pig breeds or wild boar populations were fixed for one allele at both loci. Domestic and wild-type alleles at these two genes were present in both domestic and wild populations. Findings of the distribution of MC1R alleles might be useful for tracing back the complex genetic history of autochthonous breeds. Altogether, these results indirectly demonstrate that bidirectional introgression of wild and domestic alleles is derived and affected by the human and naturally driven evolutionary forces that are shaping the Sus scrofa genome: autochthonous breeds are experiencing a sort of 'de-domestication' process, and wild resources are challenged by a 'domestication' drift. Both need to be further investigated and managed.

Genetic background of coat colour in sheep

Abstract. The coat colour of animals is an extremely important trait that affects their behaviour and is decisive for survival in the natural environment. In farm animal breeding, as a result of the selection of a certain coat colour type, animals are characterized by a much greater variety of coat types. This makes them an appropriate model in research in this field. A very important aspect of the coat colour types of farm animals is distinguishing between breeds and varieties based on this trait. Furthermore, for the sheep breeds which are kept for skins and wool, coat/skin colour is an important economic trait. Until now the study of coat colour inheritance in sheep proved the dominance of white colour over pigmented/black coat or skin and of black over brown. Due to the current knowledge of the molecular basis of ovine coat colour inheritance, there is no molecular test to distinguish coat colour types in sheep although some are available for other species, such as cattle, dogs, and horses. Understanding the genetic background of variation in one of the most important phenotypic traits in livestock would help to identify new genes which have a great effect on the coat colour type. Considering that coat colour variation is a crucial trait for discriminating between breeds (including sheep), it is important to broaden our knowledge of the genetic background of pigmentation. The results may be used in the future to determine the genetic pattern of a breed. Until now, identified candidate genes that have a significant impact on colour type in mammals mainly code for factors located in melanocytes. The proposed candidate genes code for the melanocortin 1 receptor (MC1R), agouti signaling protein (ASIP), tyrosinase-related protein 1 (TYRP1), microphthalmia-associated transcription factor MITF, and v-kit Hardy–Zuckerman 4 feline sarcoma viral oncogene homologue (KIT). However, there is still no conclusive evidence of established polymorphisms for specific coat colour types in sheep.

How much does it cost to look like a pig in a wild boar group?

Hybridization between domestic and wild species is known to widely occur and it is reported to be one of the major causes of the current biodiversity crisis. Despite this, poor attention has been deserved to the behavioural ecology of hybrids, in particular in relation to their social behaviour. We carried out a camera trap study to assess whether phenotypically anomalous colouration in wild boar, i.e. potentially introgressed with domestic pigs, affected the hierarchical structure of wild boar social groups. Chromatically anomalous wild boars (CAWs) were detected in 32 out of 531 wild boar videos. In most videos (75%) CAWs were the latest of the group, independently from their age class and group composition. Aggressions by their wild type fellows were recorded in 31.25% videos; by contrast, no aggression among wild type individuals was observed. The lack of camouflage may expose CAWs, and thus their group, to a higher predation risk, compared to wild type groups. This individual loss of local adaptation may increase predation risk by the wolf or detection by hunters, being maladaptive for the whole social group.

Genetic diversity, extent of linkage disequilibrium and persistence of gametic phase in Canadian pigs

Background

Knowledge on the levels of linkage disequilibrium (LD) across the genome, persistence of gametic phase between breed pairs, genetic diversity and population structure are important parameters for the successful implementation of genomic selection. Therefore, the objectives of this study were to investigate these parameters in order to assess the feasibility of a multi-herd and multi-breed training population for genomic selection in important purebred and crossbred pig populations in Canada. A total of 3,057 animals, representative of the national populations, were genotyped with the Illumina Porcine SNP60 BeadChip (62,163 markers).

Results

The overall LD (r²) between adjacent SNPs was 0.49, 0.38, 0.40 and 0.31 for Duroc, Landrace, Yorkshire and Crossbred (Landrace x Yorkshire) populations, respectively. The highest correlation of phase (r) across breeds was observed between Crossbred animals and either Landrace or Yorkshire breeds, in which r was approximately 0.80 at 1 Mbp of distance. Landrace and Yorkshire breeds presented r ≥ 0.80 in distances up to 0.1 Mbp, while Duroc breed showed r ≥ 0.80 for distances up to 0.03 Mbp with all other populations. The persistence of phase across herds were strong for all breeds, with r ≥ 0.80 up to 1.81 Mbp for Yorkshire, 1.20 Mbp for Duroc, and 0.70 Mbp for Landrace. The first two principal components clearly discriminate all the breeds. Similar levels of genetic diversity were observed among all breed groups. The current effective population size was equal to 75 for Duroc and 92 for both Landrace and Yorkshire.

Conclusions

An overview of population structure, LD decay, demographic history and inbreeding of important pig breeds in Canada was presented. The rate of LD decay for the three Canadian pig breeds indicates that genomic selection can be successfully implemented within breeds with the current 60 K SNP panel. The use of a multi-breed training population involving Landrace and Yorkshire to estimate the genomic breeding values of crossbred animals (Landrace × Yorkshire) should be further evaluated. The lower correlation of phase at short distances between Duroc and the other breeds indicates that a denser panel may be required for the use of a multi-breed training population including Duroc.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-017-0473-y) contains supplementary material, which is available to authorized users.

STR Profiling for Discrimination between Wild and Domestic Swine Specimens and between Main Breeds of Domestic Pigs Reared in Belarus

A panel comprising 16 short tandem repeats (STRs) and a gender-specific amelogenin marker was worked out and tested for robustness in discrimination between wild and domestic swine subspecies encountered in Europe, between regional populations of wild boars and between main breeds of domestic pigs reared in Belarus. The STR dataset comprised 310 wild boars, inhabiting all administrative regions of Belarus, and 313 domestic pigs, representing three local and three cosmopolitan lines. Additionally, a total of 835 wild boars were genotyped for the presence of melanocortin 1 receptor (MC1R) alleles specific for domestic pigs. Correctness of assignment of STR profiles to appropriate populations was measured by log-likelihood ratios (log-LRs). All samples were correctly identified as wild boars or domestic pigs with average log-LR of 42.4 (LR = 2.6×10¹⁸). On the other hand, as many as 50 out of 835 (6.0%) genotyped wild boars from Belarus possessed MC1R alleles specific to domestic pigs, demonstrating supremacy of our STR profiling system over traditional differentiation between wild boars and domestic pigs, based on single binary markers. Mean log-LRs for allocation of wild boars to their regions of origin and of domestic pigs to appropriate breeds were 2.3 (LR = 9.7) and 13.4 (LR = 6.6×10⁵), respectively. Our results demonstrate the developed STR profiling system to be a highly efficient tool for differentiation between wild and domestic swine subspecies and between diverse breeds of domestic pigs as well as for verification of genetic identity of porcine specimens for the purpose of forensic investigations of wildlife crimes, assurance of veterinary public health, parentage control in animal husbandry, food safety management and traceability of livestock products.

Demographic history, current expansion and future management challenges of wild boar populations in the Balkans and Europe

Wild boar (Sus scrofa), one of the most widespread wildlife species, has entered a stage of continuous growth in Europe, and could even be considered a pest species. We analysed microsatellite variability in 723 wild boars from across Europe, including the northern Dinaric Balkans. Our aims were: (1) to define the population structure of wild boars in the Balkans and its relation with other European populations; (2) to estimate effective populations sizes, levels of intra- and inter-population diversity, inbreeding migration and gene flow patterns; (3) to test subpopulations for bottlenecks; (4) to interpret these results in light of current knowledge about the demographic history of wild boars in Europe; and (5) to discuss the relevance of these findings for management and conservation. Strong population structuring was observed and 14 subpopulations were revealed. High genetic diversity was found, and besides the well-known identity of the Italian populations of Sardinia and Castelporziano, we bring new insights into other potential relevant, refugial populations such as Littoral Slovenia, South Portugal, North-western Iberia and an entire cluster in the Balkans. There was evidence of gene flow going from these refugial subpopulations towards less peripheral and more admixed subpopulations. Recent population bottlenecks and expansions were detected, mostly in the peninsular refuge subpopulations. The results are consistent with the fluctuations of wild boar numbers in Europe since the beginning of the twentieth century. These results should be taken into account in future conservation and management plans for wild boar populations in Europe.

A novel MC1R allele for black coat colour reveals the Polynesian ancestry and hybridization patterns of Hawaiian feral pigs

Pigs (Sus scrofa) have played an important cultural role in Hawaii since Polynesians first introduced them in approximately AD 1200. Additional varieties of pigs were introduced following Captain Cook's arrival in Hawaii in 1778 and it has been suggested that the current pig population may descend primarily, or even exclusively, from European pigs. Although populations of feral pigs today are an important source of recreational hunting on all of the major islands, they also negatively impact native plants and animals. As a result, understanding the origins of these feral pig populations has significant ramifications for discussions concerning conservation management, identity and cultural continuity on the islands. Here, we analysed a neutral mitochondrial marker and a functional nuclear coat colour marker in 57 feral Hawaiian pigs. Through the identification of a new mutation in the MC1R gene that results in black coloration, we demonstrate that Hawaiian feral pigs are mostly the descendants of those originally introduced during Polynesian settlement, though there is evidence for some admixture. As such, extant Hawaiian pigs represent a unique historical lineage that is not exclusively descended from feral pigs of European origin.

Unexpected but welcome. Artificially selected traits may increase fitness in wild boar

Artificial selection affects phenotypes differently by natural selection. Domestic traits, which pass into the wild, are usually negatively selected. Yet, exceptionally, this axiom may fail to apply if genes, from the domestic animals, increase fertility in the wild. We studied a rare case of a wild boar population under the framework of Wright's interdemic selection model, which could explain gene flow between wild boar and pig, both considered as demes. We analysed the MC1R gene and microsatellite neutral loci in 62 pregnant wild boars as markers of hybridization, and we correlated nucleotide mutations on MC1R (which are common in domestic breeds) to litter size, as an evaluation of fitness in wild sow. Regardless of body size and phyletic effects, wild boar sows bearing nonsynonymous MC1R mutations produced larger litters. This directly suggests that artificially selected traits reaching wild populations, through interdemic gene flow, could bypass natural selection if and only if they increase the fitness in the wild.

Exposure of extensively farmed wild boars (Sus scrofa scrofa) to selected pig pathogens in Greece

BACKGROUND

Increased density and distribution of wild boar populations are likely to promote interactions and transmission of certain pathogens, not only among wild boar but also from wild boar to livestock or humans and vice versa.

OBJECTIVE

The purpose of this study was to determine seroprevalence against seven selected pathogens in wild boar living in four different areas in Greece.

ANIMALS AND METHODS

In total, 359 serum samples were collected from extensively farmed wild boar (Sus scrofa scrofa) originating from four distinct geographical areas throughout Greece from April 2012 to August 2013. Samples were tested for antibodies to Actinobacillus pleuropneumoniae, African swine fever virus (ASFV), Aujeszky's disease virus (ADV), classical swine fever virus (CSFV), Erysipelothrix rhusiopathiae, Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome virus (PRRSV). Prevalence was compared among the four regions using Fisher's exact test.

RESULTS

Low overall seropositivities of 2.4% and 5.6% were detected for E. rhusiopathiae and PRRSV, respectively, higher ones for ADV (32.0%) and the highest (72.5% and 90.5%) for M. hyopneumoniae and A. pleuropneumoniae, respectively. All sera tested were found negative for antibodies directed against CSFV and ASFV.

CONCLUSIONS

This is the first report of exposure of wild boars to selected pig pathogens in Greece. These results are indicative of the circulation of these pathogens in Greece with the exception of CSFV and ASFV and suggestive of the potential role of wild boars on their maintenance and transmission to their domestic counterparts and vice versa.

Differentiation of meat from European wild boars and domestic pigs using polymorphisms in the MC1R and NR6A1 genes

Wild boar meat cannot be easily distinguished from domestic pig meat, especially in processed products, thus it can be fraudulently substituted with cheaper domestic pork. In this study we genotyped polymorphisms in two genes (MC1R, affecting coat color and NR6A1, associated with number of vertebrae) in 293 domestic pigs of five commercial breeds, 111 wild boars sampled in Italy, and 90 in Slovenia and other Western Balkan regions. Allele and genotype frequency data were used to set up a DNA-based method to distinguish meat of wild boars and domestic pigs. Genotyping results indicated that domesticated genes were introgressed into wild boar populations. This complicated the determination of the origin of the meat and would cause a high error rate if markers of only one gene were used. The combined use of polymorphisms in the two analyzed genes substantially reduced false negative results.

Use of domesticated pigs by Mesolithic hunter-gatherers in northwestern Europe

Mesolithic populations throughout Europe used diverse resource exploitation strategies that focused heavily on collecting and hunting wild prey. Between 5500 and 4200 cal BC, agriculturalists migrated into northwestern Europe bringing a suite of Neolithic technologies including domesticated animals. Here we investigate to what extent Mesolithic Ertebølle communities in northern Germany had access to domestic pigs, possibly through contact with neighbouring Neolithic agricultural groups. We employ a multidisciplinary approach, applying sequencing of ancient mitochondrial and nuclear DNA (coat colour-coding gene MC1R) as well as traditional and geometric morphometric (molar size and shape) analyses in Sus specimens from 17 Neolithic and Ertebølle sites. Our data from 63 ancient pig specimens show that Ertebølle hunter-gatherers acquired domestic pigs of varying size and coat colour that had both Near Eastern and European mitochondrial DNA ancestry. Our results also reveal that domestic pigs were present in the region ~500 years earlier than previously demonstrated.

Domestication does not narrow MHC diversity in Sus scrofa

The Major Histocompatibility Complex (MHC) is a multigene family of outstanding polymorphism. MHC molecules bind antigenic peptides in the peptide-binding region (PBR) that consists of five binding pockets (P). In this study, we compared the genetic diversity of domestic pigs to that of the modern representatives of their wild ancestors, the wild boar, in two MHC loci, the oligomorphic DQA and the polymorphic DRB1. MHC nucleotide polymorphism was compared with the actual functional polymorphism in the PBR and the binding pockets P1, P4, P6, P7, and P9. The analysis of approximately 200 wild boars collected throughout Europe and 120 domestic pigs from four breeds (three pureblood, Pietrain, Leicoma, and Landrace, and one mixed Danbred) revealed that wild boars and domestic pigs share the same levels of nucleotide and amino acid polymorphism, allelic richness, and heterozygosity. Domestication did not appear to act as a bottleneck that would narrow MHC diversity. Although the pattern of polymorphism was uniform between the two loci, the magnitude of polymorphism was different. For both loci, most of the polymorphism was located in the PBR region and the presence of positive selection was supported by a statistically significant excess of nonsynonymous substitutions over synonymous substitutions in the PBR. P4 and P6 were the most polymorphic binding pockets. Functional polymorphism, i.e., the number and the distribution of pocket variants within and among populations, was significantly narrower than genetic polymorphism, indicative of a hierarchical action of selection pressures on MHC loci.