Epidemiological survey of swine influenza A virus in selected wild boar populations in Germany

The aim of this study was to evaluate the epidemiological situation of swine influenza virus (SIV) infections in different wild boar populations in Germany based on a serological surveillance in some Bundeslaender (federal states) in connection with virological investigations in wild boar shot in Northern Germany (Mecklenburg-Western Pomerania, district of Nordvorpommern). Altogether, 1245 sera from wild boar were tested using the hemagglutination inhibition test. The established seroprevalence rate was low (on average 5.2%). Antibodies were only detected against the subtypes H1N1 and H3N2 showing differences between wild boar populations and age classes. The virological investigation of samples derived from lungs of wild boar shot in Mecklenburg-Western Pomerania, district of Nordvorpommern (n=242), revealed that the virus prevalence (two virologically positive animals, 0.8%) was very low. Based on serological typing, the isolated SIV was identified as subtype H3N2. Molecular biological investigations of the hemagglutinin (HA) and neuraminidase (NA) genes confirmed this result. This study suggests that SIV infections in wild boar seem to be no serious threat for domestic pigs.     

Epidemiological study on porcine circovirus type 2 (PCV2) infection in the European wild boar (Sus scrofa)

Porcine circovirus type 2 (PCV2) is considered as the causative agent of postweaning multisystemic wasting syndrome (PMWS) in domestic pigs, where the virus is ubiquitous as evidenced by serological surveys. We present the results of the first nationwide sero-survey on the presence of PCV2 antibodies in European wild boars, and report the first PMWS case in a wild boar from Spain. Sera from 656 hunter harvested wild boars from 45 different geographical sites and 22 additional imported animals were analysed by means of an immunoperoxidase monolayer assay (IPMA). We also examined the tissues from 55 healthy and one diseased wild boars for the presence of PCV2 nucleic acid and PMWS lesions by in situ hybridisation and histopathology, respectively. Additionally, abundance estimates of wild boars and field interviews were carried out on 30 sampling sites. The prevalence of medium to high PCV2 serological titres among the examined wild boars was 47.89 +/- 1.9%. Seropositive wild boars appeared in all but one of the geographical regions analysed. Seroprevalence and titre of PCV2 antibodies were closely related to the management of the wild boar populations. Wild boars from intensively managed, farm-like populations had higher prevalence than wild boars living in more natural situations. The effect of wild boar abundance and management on PCV2 antibody prevalence was further evidenced by the high correlation existing between the relative abundance estimates of animals and the percentage of wild boars with medium to high levels of PCV2 antibodies. PCV2 nucleic acid was detected in the tissues of three wild boars. One of these was diagnosed as PMWS. The results, in addition to information on piglet mortalities, suggest a potential role of PMWS in piglet mortality in intensively managed wild boar populations.     

Evidence of the role of European wild boar as a reservoir of Mycobacterium tuberculosis complex

Bovine tuberculosis (bTB) is caused by Mycobacterium bovis and closely related mycobacteria of the Mycobacterium tuberculosis complex. They have an extensive host range and may cause zoonotic TB. A major obstacle to bTB eradication in livestock is the implication of wildlife in the natural cycle of the pathogen. The identification of wildlife reservoir hosts is crucial for the implementation of effective control measures. The European wild boar (Sus scrofa) is frequently considered a spillover or dead end host rather than a true reservoir, and scientific evidence is conflicting outside Mediterranean Spain. The aim of this review is to update current scientific evidence of the wild boar as a TB reservoir and to underline those aspects that need further research. Evidences supporting that wild boar is a TB reservoir host include: (i) presence of common M. tuberculosis complex genotypes in wild boar, domestic and wild animals and humans, (ii) high prevalence of M. bovis among wild boar in estates fenced for decades in complete absence of contact with domestic livestock, and other wild ungulates (iii) TB lesions are frequently seen in thoracic lymph nodes and lungs, suggesting that respiratory infection and excretion may occur, and (iv) extensive tuberculous lesions in more than one anatomical region occur in a high proportion of juvenile wild boar that probably represents the main source of mycobacterial excretion. Hence, epidemiological, pathological and microbiological evidence strongly suggests that, at least in Spanish Mediterranean ecosystems, wild boar are able to maintain TB infection in the wild and are most probably able to transmit the disease to other species, acting as a true wildlife reservoir. These results expand the list of wildlife species that act as natural reservoirs of TB in different parts of the world and suggest the need to control the infection in wild boar populations for the complete eradication of the disease in Spain.     

Molecular detection of Leptospira spp. in wild boar (Sus scrofa) hunted in Liguria region (Italy)

Leptospirosis is a re-emerging and widespread zoonosis, worldwide distributed, due to a wide variety of wild and domestic animal species able to act as natural or accidental hosts. During last years, in Europe, as in Italy, wild boar (Sus scrofa) population is increased. This animal represents a reservoir for different etiological agents, such as Leptospira. The aim of this investigation was to evaluate the prevalence of Leptospira spp. in wild boar hunted in Liguria region (Italy) during two-year hunting seasons. From 611 hunted wild boar, kidneys were collected. DNA was extracted from each organ and different targets were used to detect pathogenic (lipL32 gene), intermediate (16S rRNA gene) and saprophytic (23S rRNA gene) Leptospira by Taqman-based RealTime-PCR assays. Overall, kidneys were sampled from 282 adults, 155 sub-adults and 174 young wild boar (in total 314 males and 298 females). By RealTime PCR 77 kidneys were positive and, among these, 74 resulted positive for pathogenic (96.10%) and 3 (3.90%) for intermediate Leptospira. No significant differences in pathogenic Leptospira infection ratio were detected between male (11.50%) and female (12.75%). Only 13 sub-adult animals (8.39%) resulted infected by pathogenic Leptospira; 23 young animals (13.22%) and 38 adult animals (13.47%) were positive. The results of this study confirmed the importance of wild boar in the epidemiology of leptospirosis, which is able to infect other animal species (domestic and wild) including humans. Rarely, intermediate Leptospira could be able to infect wild boar with a renal localization that can contribute to their shedding and circulation.     

Genotyping of Mycoplasma hyopneumoniae in wild boar lung samples

Mycoplasma hyopneumoniae is the etiologic agent of enzootic pneumonia (EP), an important cause of disease-associated losses in swine production and a role of wild boar in recurrent infections can be supposed. Genotypes of M. hyopneumoniae from wild boar are unknown but could indicate its role as a potential reservoir. Therefore, 34 lung samples being PCR-positive for M. hyopneumoniae from wild boar from the Geneva region in Switzerland were assayed by genotyping using the p146 and multi-locus sequence typing (MLST) approaches and compared to data from outbreak cases from domestic swine in Switzerland. Successful genotyping was dependent on a sufficiently high concentration of M. hyopneumoniae DNA in the samples as assessed by different real-time PCR assays. The p146 genotyping was more successful with 24 samples (70.5%) being typeable whereas only 6 samples (17.6%) could be genotyped using the MLST approach. Variability of genotypes was high but identical types were found in geographically related animals. Genotypes from wild boar showed phylogenetic relatedness to those from domestic pigs but no matching types could be identified. Results show that direct genotyping from wild boar lung samples is possible and provides a promising approach to investigate future EP outbreak related samples from wild boar.     

Serosurveillance of notifiable veterinary diseases in wild boar in the Netherlands

During the hunting season 1996-1999, blood samples were collected from wild boar shot in The Netherlands. Sera were screened for presence of antibodies against classical swine fever virus (CSFV), swine vesicular disease virus (SVDV), Aujeszky's disease virus (ADV), and Trichinella spiralis. The results indicate that CSFV, SVDV, and ADV are uncommon in the wild boar population. Therefore, it seems that CSFV, SVDV, and ADV infection in the wild boar population is not an important reservoir in The Netherlands. ADV and CSFV infections are endemic in the wild boar population in Germany. Since contact between the German and Dutch wild boar populations can not be excluded, continuation of the sero-surveillance system seems appropriate. In the decade before 1998, the wild boar population in The Netherlands seemed to be free of T. spiralis. Whether the finding, in the hunting season of 1998-1999, of a few wild boar with antibodies against T. spiralis is an artefact or not, should be investigated in further research.     

利用DNA条形码对海南特种野猪的鉴定研究

试验旨在探讨以猪的细胞色素氧化酶Ⅰ（cytochrome C oxidase subunitⅠ,COXⅠ）基因的特定区段作为DNA条形码识别海南特种野猪与其他品种的可行性和有效性。以海南特种野猪、海南野猪、屯昌猪、五指山猪及长白猪为研究对象,测定其COXⅠ基因,同时在NCBI中下载已发表的具有地方代表性的13个猪品种的COXⅠ基因序列,分析海南特种野猪与其他品种的遗传多样性、遗传距离,并构建系统进化树。结果发现,猪COXⅠ基因序列长1 419 bp,5个猪品种45个个体COXⅠ基因共检测到67个变异位点,占分析位点的4.7%,其中简约信息位点22个;5个猪品种的种内遗传距离为0.001~0.019,其中海南特种野猪的种内遗传最大,为0.019;5个猪品种的种间遗传距离为0.009~0.123,其中海南特种野猪与长白猪的遗传距离最大,为0.123;海南特种野猪杂交情况比较明显,与海南本地品种五指山猪、屯昌猪和海南野猪都有聚类,与武夷黑猪、三都黑猪、陆川猪位于一个分支,另一部分与大花白猪位于一个分支,与长白猪没有聚类。本试验结果为海南特种野猪的进一步选育提供了参考依据。     

Detection and molecular characterization of Suid herpesvirus type 1 in Austrian wild boar and hunting dogs

Aujeszky's disease (AD), caused by Suid herpesvirus type 1 (SuHV-1), is an economically important disease in domestic swine. Thus, rigorous control programmes have been implemented and consecutively AD in domestic swine was successfully eradicated in many countries, including Austria. However, SuHV-1 continues to thrive in wild boar populations, as indicated by high seroprevalences in a number of European countries and by occasional cases of AD in hunting dogs. For the first time, SuHV-1 was detected in Austrian wild boar and a molecular characterization of SuHV-1 isolated from wild boar and hunting dogs was performed. Results of preliminary serological analyses suggest a regional SuHV-1 seroprevalence of over 30% in free-living and almost 70% in fenced wild boar from Eastern Austria. Molecular typing of Austrian SuHV-1 isolates of wild boar origin revealed the presence of two genetically distinct variants of SuHV-1, both capable of infecting dogs that have been exposed to infected wild boar during hunting.     

Simulating the spread of classical swine fever virus between a hypothetical wild-boar population and domestic pig herds in Denmark

Denmark has no free-range wild-boar population. However, Danish wildlife organizations have suggested that wild boar should be reintroduced into the wild to broaden national biodiversity. Danish pig farmers fear that this would lead to a higher risk of introduction of classical swine fever virus (CSFV), which could have enormous consequences in terms of loss of pork exports. We conducted a risk assessment to address the additional risk of introducing and spreading CSFV due to the reintroduction of wild boar. In this paper, we present the part of the risk assessment that deals with the spread of CSFV between the hypothetical wild-boar population and the domestic population. Furthermore, the economic impact is assessed taking the perspective of the Danish national budget and the Danish pig industry. We used InterSpreadPlus to model the differential classical swine fever (CSF) risk due to wild boar. Nine scenarios were run to elucidate the effect of: (a) presence of wild boar (yes/no), (b) locations for the index case (domestic pig herd/wild-boar group), (c) type of control strategy for wild boar (hunting/vaccination) and (d) presence of free-range domestic pigs. The presence of free-range wild boar was simulated in two large forests using data from wildlife studies and Danish habitat data. For each scenario, we estimated (1) the control costs borne by the veterinary authorities, (2) the control-related costs to farmers and (3) the loss of exports associated with an epidemic. Our simulations predict that CSFV will be transmitted from the domestic pig population to wild boar if the infected domestic pig herd is located close to an area with wild boar (<5 km). If an outbreak begins in the wild-boar population, the epidemic will last longer and will occasionally lead to several epidemics because of periodic transfer of virus from groups of infected wild boar to domestic pig herds. The size and duration of the epidemic will be reduced if there are no free-range domestic pig herds in the area with CSF-infected wild boar. The economic calculations showed that the total national costs for Denmark (i.e. the direct costs to the national budget and the costs to the pig industry) related to an outbreak of CSF in Denmark will be highly driven by the reactions of the export markets and in particular of the non-EU markets. Unfortunately, there is a substantial amount of uncertainty surrounding this issue. If hunting is used as a control measure, the average expenses related to a CSF outbreak will be 40% higher if wild boar are present compared with not present. However, a vaccination strategy for wild boar will double the total costs compared with a hunting strategy.     

集约化养猪场嗜流产衣原体病流行状况的初步调查

本试验对北京郊区5个规模化猪场断奶仔猪、育成猪、育肥猪和怀孕母猪采集血清共507份,同时采集密切接触饲养人员、仔猪、育肥猪的喉头拭子、母猪阴道拭子及公猪的精液共183份。分别使用间接血凝诊断试剂盒、法国ELISA试剂盒检测抗体;利用直接荧光染色法检测抗原,包括166份猪喉头拭子、阴道拭子和精液以及17份饲养人员喉头拭子。结果发现间接血凝诊断试剂盒、ELISA试剂盒抗体阳性率分别为4.14%和2.17%;抗原平均阳性率为14.8%,其中精液阳性率达到37.5%,母猪阴道拭子阳性率为27.5%,饲养人员阳性率为23.5%。本试验证实北京郊区猪嗜流产衣原体在种公猪、母猪群和饲养员呈高流行趋势。同时研究结果显示,5个被调查的规模化猪场嗜流产衣原体抗体阳性率显著低于有报道的其他省市,这与间接血凝诊断试剂盒检测结果高于ELISA试剂有关。针对发现的问题,必须采取有效措施控制种公猪精液污染衣原体现象,阻断向母猪和饲养人员传播,以降低人兽共患病发生的风险。     

Genetic profile and serosurvey for virus infections of Japanese wild boars in Shikoku Island

To estimate the genetic background of Japanese wild boars inhibiting the 4 prefectures of Shikoku Island (Kagawa, Tokushima, Kouchi and Ehime), we examined haplotypes of mitochondrial DNA (mtDNA) and genotypes of the nuclear glucosephosphate isomerase-processed pseudogene (GPIP) in 189 wild boars. Of the 8 different mtDNA haplotypes (J5, J10, J12, J13, J15, J19, J20 and E33) detected in Shikoku Island, the first to be identified were J19 and J20 (of Japanese wild boar lineage) and E33 (of European domestic pig lineage). The presence of haplotype E33 indicates local crossbreeding between wild boar and escaped domestic pigs and/or crossbred Inobuta. Four kinds of the GPIP genotypes were detected from 189 wild baors in Shikoku Island, but no European GPIP alleles were found. In 113 wild boars, no antibodies against Classical Swine Fever or Aujeszky's disease were detected, suggesting that they had not been exposed to those pathogens.     

Patterns of lesions of bovine tuberculosis in wild red deer and wild boar

The data obtained from a survey of Mycobacterium bovis infection in wild red deer (Cervus elaphus) and wild boar (Sus scrofa) conducted in France in the 2005/06 hunting season were used to describe and quantify the pathological findings in the two species. The red deer had caseous abscessed lesions in their organs and lymph nodes, whereas in the wild boar the lesions were predominantly caseocalcareous and occurred mainly in the lymph nodes. The severity of the gross tuberculosis-like lesions was estimated on the basis of a numerical score. The significant difference between the distribution of the scores in the two species indicated that the disease was more serious in the red deer than in the wild boar. Unlike the red deer, the wild boar did not show a generalised pattern of disease. Among the lymph nodes examined systematically, gross lesions were most frequently observed in the mesenteric lymph nodes in the red deer and in the retropharyngeal lymph nodes in the wild boar. In both species, the presence of gross lesions showed the closest agreement with the isolation of M bovis from the same lymph nodes. The different patterns of the lesions of tuberculosis in the two species suggest that red deer might play an important role in the intraspecies and interspecies dissemination of the infection, whereas in wild boar the spread of the infection would be more likely to be restricted to other wild boar.     

Incidence of classical swine fever (CSF) in wild boar in a densely populated area indicating CSF virus persistence as a mechanism for virus perpetuation

A virological survey was carried out to establish the distribution of classical swine fever (CSF) virus among wild boar in the Federal State of Brandenburg, Germany. Organ materials and blood samples were collected from 11,670 wild boar shot or found dead during the period March 1995 to December 1997. In total 211 (1.8%) wild boar were positive for CSF virus or antigen. The incidence of CSF-positive animals decreased continuously from 4.6% at the beginning of the epidemic in 1995 to 0.7% in 1997. The highest incidence of positive animals (22%) was found in wild-boar piglets younger than 3 months of age in 1995. The findings were indicative for the decisive role which young wild boar play in the epidemiology of CSF. Following intrauterine transfer some of the wild-boar piglets were probably persistently infected with CSF virus as experienced experimentally. Such piglets can be held responsible for CSF virus perpetuation within the wild-boar population. No CSF virus was isolated from adult wild boar weighing more than 75 kg. During 3 years of monitoring a sufficient number of susceptible wild boar, in particular young animals, was available to maintain the infection chain in that area. It was concluded that persistently infected piglets and the high population density of wild boar in the Brandenburg region offered optimal conditions for the establishment of an CSF epidemic.     

Evaluation of ELISA coupled with Western blot as a surveillance tool for Trichinella infection in wild boar (Sus scrofa)

Trichinella surveillance in wildlife relies on muscle digestion of large samples which are logistically difficult to store and transport in remote and tropical regions as well as labour-intensive to process. Serological methods such as enzyme-linked immunosorbent assays (ELISAs) offer rapid, cost-effective alternatives for surveillance but should be paired with additional tests because of the high false-positive rates encountered in wildlife. We investigated the utility of ELISAs coupled with Western blot (WB) in providing evidence of Trichinella exposure or infection in wild boar. Serum samples were collected from 673 wild boar from a high- and low-risk region for Trichinella introduction within mainland Australia, which is considered Trichinella-free. Sera were examined using both an ‘in-house’ and a commercially available indirect-ELISA that used excretory–secretory (E/S) antigens. Cut-off values for positive results were determined using sera from the low-risk population. All wild boar from the high-risk region (352) and 139/321 (43.3%) of the wild boar from the low-risk region were tested by artificial digestion. Testing by Western blot using E/S antigens, and a Trichinella-specific real-time PCR was also carried out on all ELISA-positive samples. The two ELISAs correctly classified all positive controls as well as one naturally infected wild boar from Gabba Island in the Torres Strait. In both the high- and low-risk populations, the ELISA results showed substantial agreement (k-value = 0.66) that increased to very good (k-value = 0.82) when WB-positive only samples were compared. The results of testing sera collected from the Australian mainland showed the Trichinella seroprevalence was 3.5% (95% C.I. 0.0–8.0) and 2.3% (95% C.I. 0.0–5.6) using the in-house and commercial ELISA coupled with WB respectively. These estimates were significantly higher (P < 0.05) than the artificial digestion estimate of 0.0% (95% C.I. 0.0–1.1). Real-time PCR testing of muscle from seropositive animals did not detect Trichinella DNA in any mainland animals, but did reveal the presence of a second larvae-positive wild boar on Gabba Island, supporting its utility as an alternative, highly sensitive method in muscle examination. The serology results suggest Australian wildlife may have been exposed to Trichinella parasites. However, because of the possibility of non-specific reactions with other parasitic infections, more work using well-defined cohorts of positive and negative samples is required. Even if the specificity of the ELISAs is proven to be low, their ability to correctly classify the small number of true positive sera in this study indicates utility in screening wild boar populations for reactive sera which can be followed up with additional testing.     

Incidence of Classical Swine Fever (CSF) in Wild Boar in a Densely Populated Area Indicating CSF. Virus Persistence as a Mechanism for Virus Perpetuation

A virological survey was carried out to establish the distribution of classical swine fever (CSF) virus among wild boar in the Federal State of Brandenburg, Germany. Organ materials and blood samples were collected from 11 670 wild boar shot or found dead during the period March 1995 to December 1997. In total 211 (1.8%) wild boar were positive for CSF virus or antigen. The incidence of CSF-positive animals decreased continuously from 4.6% at the beginning of the epidemic in 1995 to 0.7% in 1997. The highest incidence of positive animals (22%) was found in wild-boar piglets younger than 3 months of age in 1995. The findings were indicative for the decisive role which young wild boar play in the epidemiology of CSF. Following intrauterine transfer some of the wild-boar piglets were probably persistently infected with CSF virus as experienced experimentally. Such piglets can be held responsible for CSF virus perpetuation within the wild-boar population. No CSF virus was isolated from adult wild boar weighing more than 75 kg. During 3 years of monitoring a sufficient number of susceptible wild boar, in particular young animals, was available to maintain the infection chain in that area. It was concluded that persistently infected piglets and the high population density of wild boar in the Brandenburg region offered optimal conditions for the establishment of an CSF epidemic.     

猪肉质性状功能基因在野猪群体内的变异研究

本试验旨在研究猪肉质性状功能基因突变位点在野猪群体里面的遗传变异规律。以MC4R基因(D298N G>A)、RYR1基因(c.1843 C>T)、PRKAG3基因(1849 G>A)和IGF2基因(3072 G>A)突变位点为基础,通过PCR-RFLP、PCR-SSCP技术,对72头圈养野猪群体进行突变位点的多态性检测和群体遗传变异分析。结果表明,RYR1基因在c.1843 C>T突变位点的CC基因型为野猪群体内的优势基因型,等位基因C是野猪群体内的优势基因,没有TT基因型,该突变位点处于不平衡状态(P<0.01和P<0.05)。在MC4R基因D298N G>A突变位点上,GG基因型为野猪群体内的优势基因型,等位基因G是野猪群体内的优势基因。而PRKAG3基因(1849 G>A)的突变位点检测结果是GG基因型为野猪群体内的优势基因型,等位基因G是野猪群体内的优势基因,没有发现AA基因型。IGF2基因3072 G>A在野猪群体内没有发现多态性,经测序验证全部为GG基因型。这3个基因突变都处于Hardy-Weinberg平衡状态(P>0.05)。本研究得出该野猪种群体遗传多样性和变异较小,符合其品种特性。     

Galanin is Co‐Expressed with Substance P,Calbindin and Corticotropin‐Releasing Factor (CRF) in The Enteric Nervous System of the Wild Boar (Sus scrofa) Small Intestine

Galanin is a neuropeptide widely present in the enteric nervous system of numerous animal species and exhibiting neurotransmittery/neuromodulatory roles. Colocalization patterns of galanin with substance P (SP), corticotropin‐releasing factor (CRF) and calbindin were studied in the small intestine of the wild boar using immunofluorescence technique. We demonstrated the presence of SP in substantial populations of galanin‐immunoreactive (IR) submucous neurons. Additionally, different amounts of nerve fibres exhibiting simultaneous presence of galanin and SP were noted in the small intestinal smooth musculature, submucous ganglia, lamina muscularis mucosae and mucosa. In the wild boar duodenum, jejunum and ileum, the co‐expression of galanin and calbindin was limited to minor populations of submucous neurons only. Single galanin‐/CRF‐IR nerve fibres were exclusively present in the duodenal and jejunal (but not ileal) mucosa. These results strongly suggest that galanin participates in neuronal control of the wild boar small intestine also by functional co‐operation with other biologically active neuropeptides.