Variation in clinical and parasitological traits in Pietrain and Meishan pigs infected with Sarcocystis miescheriana

Microscopic detection and molecular characterization of Sarcocystis miescheriana in wild boars (Sus scrofa): first report from Greece

The genus Sarcocystis includes protozoan parasites with an indirect life cycle. Sarcocystis spp. can infect various animal species and humans, causing sarcocystosis, a parasitosis of economic importance and zoonotic concern. Wild boars can act as intermediate hosts for Sarcocystis miescheriana and the zoonotic Sarcocystis suihominis that infects humans by consumption of raw or undercooked infected swine meat. In the present study, the diaphragmatic muscle tissue of 123 wild boars hunted in Greece was examined to determine the frequency of Sarcocystis spp. The samples were examined by tissue compression and molecular techniques. Under light microscopy, 34 out of 123 (27.6%) wild boars tested positive for Sarcocystis spp., while a higher infection prevalence (75%) was revealed by multiplex PCR performed in 100 of the samples. The partial mtDNA cox1 gene (~ 1100 bp) of 20 samples tested positive for S. miescheriana by multiplex PCR was amplified and sequenced. Sarcocystis miescheriana was identified as the only species involved in these infections. This is the first study on the prevalence of Sarcocystis spp. in wild animals in Greece. Further, large-scale surveys are needed to assess the prevalence and species of this parasite in Greece and to design efficient control and preventive measures in a One Health perspective.

Molecular differentiation of Sarcocystis miescheriana and Sarcocystis suihominis using a new multiplex PCR targeting the mtDNA cox1 gene in wild boars in southern Italy

The increase of wild boar populations density and their meat consumption across Europe could expose humans to a plethora of foodborne diseases as sarcocystosis, caused by the zoonotic protozoan Sarcocystis suihominis. Humans become infected by eating raw or undercooked pig (Sus scrofa domesticus) containing S. suihominis sarcocysts. Despite this, to date very few data are available on the risk of infection by this parasite to wild boar (Sus scrofa) meat consumers. Thus, the present study aimed to assess the occurrence of Sarcocystis spp. in wild boars from southern Italy, applying both histology and a new multiplex PCR assay targeting the cox1 gene. Between 2019 and 2020, 997 muscle tissues (i.e., n = 269 oesophagus, n = 277 diaphragms, n = 298 hearts, n = 153 tongues) from 311 wild boars were collected and screened by a combined histological and molecular approach. Overall, 251 (80.7%) animals tested were positive for Sarcocystis spp., and S. miescheriana whose definitive hosts are canids, was the only molecularly identified species. A statistically significant difference (p < 0.05) in the prevalence of Sarcocystis infection was found according to the wild boar age and muscle tissue. Findings outlined the low zoonotic potential of infection to humans via wild boar meat consumption in Italy and the importance of the application of new molecular methods in distinguishing different Sarcocystis species.

Integrated analysis of lncRNA-mediated ceRNA network involved in immune regulation in the spleen of Meishan piglets

Meishan pigs are a famous local pig breed in China, with high fertility and early sexual maturity, and stronger immunity compared to other breeds. The spleen is the largest lymphoid organ in pigs and performs essential functions, such as those relating to immunity and haematopoiesis. The invasion of many pathogenic microorganisms in pigs is associated with spleen damage. Long non-coding RNAs participate in a broad range of biological processes and have been demonstrated to be associated with splenic immune regulation. However, the expression network of mRNAs and lncRNAs in the spleen of Meishan pigs remains unclear. This study collected spleen tissues from Meishan piglets at three different ages as a model, and mRNA and lncRNA transcripts were profiled for each sample. Additionally, 1,806 differential mRNAs and 319 differential lncRNAs were identified. A complicated interaction between mRNAs and lncRNAs was identified via WGCNA, demonstrating that lncRNAs are a crucial regulatory component in mRNA. The results show that the modules black and red have similar mRNA and lncRNA transcription patterns and are mainly involved in the process of the immune defense response. The core genes (DHX58 and IFIT1) and key lncRNAs (TCONS-00002102 and TCONS-00012474) of piglet spleen tissue were screened using the ceRNA network. The expression of these genes is related to the immune response of pigs. Our research may contribute to a further understanding of mRNA and lncRNA expression in the spleen of piglets, and provide new ideas to improve the disease resistance of piglets.

Detection of Sarcocystis spp. and Toxoplasma gondii in swine and detection of DNA of these protozoa in tissues and sausages

The seroprevalence of Sarcocystis spp. and Toxoplasma gondii was researched in swine raised in Santa Maria, RS, Brazil. Serum samples from 84 pigs from 31 farms were tested using indirect immunofluorescence assay (IFA) for both agents. Additionally, 53 samples of pork sausages and tissues destined for human consumption, including: salami, sausage, black pudding, heart, tongue, brain, and rib muscle, were submitted to PCR to detect DNA for each agent. The frequency of anti-Sarcocystis spp. antibodies was 36.9% (31/84), with titers ranging from 32 to 1024, and 25% (21/84) for anti-T. gondii antibodies, with titers ranging from 64 to 2048. Sarcocystis spp. and T. gondii DNA were detected in 67.9% (36/53) and 13.2% (7/53) of samples, respectively. The presence of antibodies and the detection of DNA from Sarcocystis spp., and T. gondii suggests that the pigs were infected and may serve as an important reservoir for both parasites. The infection by these protozoa in the swine population is relevant to public health due to their zoonotic potential.

[Opportunities and risks of the use of genetic resistances to infectious diseases in pigs - an overview]

Demands for health, performance and welfare in pigs, as well as the desire for consumer protection and reduced antibiotic use, require optimal measures in advance of disease development. This includes, in principle, the use of genetically more resistant lines and breeding animals, whose existence has been proven for a wide range of pathogen-host interactions. In addition, attempts are being made to identify the gene variants responsible for disease resistance in order to force the selection of suitable populations, also using modern biotechnical technics. The present work is intended to provide an overview of the research status achieved in this context and to highlight opportunities and risks for the future.The evaluation of the international literature shows that genetic disease resistance exist in many areas of swine diseases. However, polygenic inheritance, lack of animal models and the influence of environmental factors during evaluation render their implementation in practical breeding programs demanding. This is where modern molecular genetic methods, such as Gene Editing, come into play. Both approaches possess their pros and cons, which are discussed in this paper. The most important infectious diseases in pigs, including general diseases and epizootics, diseases of the respiratory and digestive tract and diseases of the immune system are taken into account.

Biochemical profile of blood in naturally occurring Sarcocystis infection in cattle

The aim of this study was to determine the biochemical blood indicators in Lithuanian Black-and-White cattle with regard to the intensity of their infection with Sarcocystis spp. In total 945 bull muscle samples and 120 blood samples were used for the analysis. Aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT) were increased in infected animals relative to uninfected animals. The AST levels differed significantly between the no infection, low, and moderate infection groups (P < 0.05); ALP differed between the no infection and moderate infection groups (P < 0.05); and ALT differed between the no infection, low infection and intense infection groups (P < 0.05). Total protein levels were higher than physiological limits and differed significantly between the no infection, low infection and intense infection groups (P < 0.05). Iron levels were at the lowest physiological limits and differed significantly between the no infection and low infection groups, as well as between the low infection and intense infection groups (P < 0.05). Triglyceride levels were at their physiological limits, and differed significantly between all examined groups (P < 0.05). The results show that changes in the biochemical markers ALP, AST and ALT are related to the intensity of the Sarcocystis spp. infection.

DNA methylation differences of the BPI promoter among pig breeds and the regulation of gene expression

TheBPIpromoter methylation is distinct between different pig breeds and potentially associated with its expression and disease susceptibility.

Transcriptomic Analysis Identifies Candidate Genes and Gene Sets Controlling the Response of Porcine Peripheral Blood Mononuclear Cells to Poly I:C Stimulation

Polyinosinic-polycytidylic acid (poly I:C), a synthetic dsRNA analog, has been demonstrated to have stimulatory effects similar to viral dsRNA. To gain deep knowledge of the host transcriptional response of pigs to poly I:C stimulation, in the present study, we cultured and stimulated peripheral blood mononuclear cells (PBMC) of piglets of one Chinese indigenous breed (Dapulian) and one modern commercial breed (Landrace) with poly I:C, and compared their transcriptional profiling using RNA-sequencing (RNA-seq). Our results indicated that poly I:C stimulation can elicit significantly differentially expressed (DE) genes in Dapulian (g = 290) as well as Landrace (g = 85). We also performed gene set analysis using the Gene Set Enrichment Analysis (GSEA) package, and identified some significantly enriched gene sets in Dapulian (g = 18) and Landrace (g = 21). Most of the shared DE genes and gene sets were immune-related, and may play crucial rules in the immune response of poly I:C stimulation. In addition, we detected large sets of significantly DE genes and enriched gene sets when comparing the gene expression profile between the two breeds, including control and poly I:C stimulation groups. Besides immune-related functions, some of the DE genes and gene sets between the two breeds were involved in development and growth of various tissues, which may be correlated with the different characteristics of the two breeds. The DE genes and gene sets detected herein provide crucial information towards understanding the immune regulation of antiviral responses, and the molecular mechanisms of different genetic resistance to viral infection, in modern and indigenous pigs.

Enhancing genome-wide copy number variation identification by high density array CGH using diverse resources of pig breeds

Copy number variations (CNVs) are important forms of genomic variation, and have attracted extensive attentions in humans as well as domestic animals. In the study, using a custom-designed 2.1 M array comparative genomic hybridization (aCGH), genome-wide CNVs were identified among 12 individuals from diverse pig breeds, including one Asian wild population, six Chinese indigenous breeds and two modern commercial breeds (Yorkshire and Landrace), with one individual of the other modern commercial breed, Duroc, as the reference. A total of 1,344 CNV regions (CNVRs) were identified, covering 47.79 Mb (∼1.70%) of the pig genome. The length of these CNVRs ranged from 3.37 Kb to 1,319.0 Kb with a mean of 35.56 Kb and a median of 11.11 Kb. Compared with similar studies reported, most of the CNVRs (74.18%) were firstly identified in present study. In order to confirm these CNVRs, 21 CNVRs were randomly chosen to be validated by quantitative real time PCR (qPCR) and a high rate (85.71%) of confirmation was obtained. Functional annotation of CNVRs suggested that the identified CNVRs have important function, and may play an important role in phenotypic and production traits difference among various breeds. Our results are essential complementary to the CNV map in the pig genome, which will provide abundant genetic markers to investigate association studies between various phenotypes and CNVs in pigs.

The effect of mutation at M307 in FUT1 gene on susceptibility of Escherichia coli F18 and gene expression in Sutai piglets

Escherichia coli F18 (ECF18) is a common porcine enteric pathogen. The pathogenicity of ECF18 bacteria depends on the existence of ECF18 receptor in the brush border membranes of piglet's small intestinal mucosa. Alpha (1) fucosyltransferase gene (FUT1) has been identified as the candidate gene controlling the adhesion to ECF18 receptor. The genetic variations in the position of M307 nucleotide in open reading frame of FUT1 have been proposed as a marker for selecting resistant pigs. The piglets were divided into three groups, AA, AG and GG, according to the genotypes present at M307 of FUT1. Small intestinal epithelium cells of piglets with AA, AG and GG genotypes were selected to test the adhesion capability of the wild type E.coli expressing F18ab fimbriae, the recombinant E. coli expressing F18ac fimbriae or the recombinant E. coli secreting and surface-displaying the FedF subunit of F18ab fimbriae, respectively. Here, we examined the distribution and expression of porcine FUT1 mRNA in different tissues in Sutai pigs using real-time PCR. The results showed that piglets with AA genotype show resistance, whereas piglets with GG or AG genotypes are sensitive to the pathogenic E. coli F18 in Sutai piglets. FUT1 was expressed in all the tissues that were examined, and the gene's expression was highest in the lungs. There was no significant difference in expression level among the three genotypes in the liver, lung, stomach and duodenum, where the gene expression was relatively high. The present analysis suggested that mutation at M307 in FUT1 gene determines susceptibility of small intestinal epithelium to E. coli F18 adhesion in Sutai piglet and the expression of FUT1 gene may be regulated by other factors or the mutation was likely to be in linkage disequilibrium with some cis-regulatory variants.

An intronic polymorphism in the porcine IRF7 gene is associated with better health and immunity of the host during Sarcocystis infection, and affects interferon signalling

Interferon regulatory factor 7 (IRF7), as a key regulator of type I interferon response, plays an important role during innate response against viral infection. Although well conserved across species, the structure of IRF7 and its function during parasite infection are not well documented in farm animals, such as the pig. To bridge this gap, we have determined the porcine IRF7 gene structure and identified two intronic single nucleotide polymorphisms (SNPs), SNP g.748G>C and SNP g.761A>G, in commercial pig breeds. The distribution of SNP g.761A>G in multiple breeds suggested that it was in Hardy-Weinberg equilibrium and allowed us to map it at the top of SSC2. We found that during Sarcocystis miescheriana infection, the G allele was associated with high lymphocyte levels (P < 0.02), reduced drop in platelet levels (P < 0.002) and IgG1-Th2-dominated response (P < 0.05). This suggests that the G allele was associated with better health and immunity of the host during Sarcocystis infection. Furthermore, we have also provided suggestive evidence that the G allele of SNPc.761A>G enhances the transactivation activity of IRF7, possibly by improving IRF7 transcript splicing of intron-3. These findings would suggest that IRF7, as a transcriptional regulator, is involved in the defence mechanism against a larger spectrum of pathogens, and in more host species, than initially anticipated.

Post-weaning multisystemic wasting syndrome (PMWS) clinical expression under field conditions is modulated by the pig genetic background

Post-weaning multisystemic wasting syndrome (PMWS) is a worldwide distributed disease of multifactorial origin and porcine circovirus type 2 (PCV2) has been identified as its essential infectious aetiology. Pig genetic background has been pointed to influence disease expression. In the present study, three different boar lines, namely A (100% Pietrain), B (50% Large White × 50% Pietrain) and C (25% Large White × 75% Duroc), were used to inseminate sows from the same genetic line (37.5% Large White × 37.5% Duroc × 25% Landrace) located on two PMWS-affected farms (farm-1 and farm-2). The PMWS clinical expression of their offspring was studied from weaning to slaughter, evaluating three parameters: total post-weaning mortality (PWM), PWM associated to PMWS (PMWS-PWM) and body weight (BW) evolution. The effect of other variables potentially related with PMWS, including sow and piglet PCV2 exposure, sow parity, piglet gender and piglet BW at weaning, were also considered in the study design. Overall, a total of 6.5% PWM and 4.3% PMWS-PWM occurred in the monitored farms. Pigs from boar line C showed the highest PWM (16.3%) and PMWS-PWM (12.4%), and the lowest BW; pigs from boar line A showed the lowest PWM (1.8%) and the highest BW. Furthermore, PWM was also higher in piglets from farm-2 and from multiparous sows. In farm-2, PMWS-PWM was higher in piglets from multiparous sows. Finally, BW was influenced by interactions between genetics and both farm and pig age, and was lower in piglets from farm-2. This study represents a consistent observation of the genetic background effect on PMWS clinical expression under field conditions.

First report of naturally acquired clinical sarcocystosis in a pig breeding stock

A two-year-old Large White boar from a pig breeding stock in an indoor farm in Switzerland presented anorexia, reduced general condition and fever. Despite antibiotic and anti-inflammatory treatment, the boar developed severe dyspnoea and cyanosis, and died after 4 days. At necropsy, no gross lesions were observed. Histopathologically, multifocal degeneration and necrosis of myocardial fibers with interstitial edema, severe multifocal non-suppurative myocarditis and hepatitis, and non-suppurative interstitial nephritis were observed. In heart samples, groups of organisms resembling apicomplexan tachyzoites were seen associated with the lesions. A PCR using the primers COC1-COC2 that target a conserved region of the small-subunit rRNA gene of Apicomplexa was performed with DNA from paraffin-embedded tissues. An amplification product of about 350 bp was obtained from heart samples. A sequence analysis showed 100% identities with GenBank sequences reported for Sarcocystis miescheriana. The histopathological observations and molecular findings in combination with the clinical signs, and absence of other pathologic agents highly suggested that an acute infection with S. miescheriana was the cause of death in this boar. To our knowledge, this the first report of fatal acute sarcocystosis after natural infection in a pig breeding herd.

SNPs in the porcine GOT1 gene improve a QTL for serum aspartate aminotransferase activity on SSC14

Clinical-chemical traits are essential parameters to quantify the health status of individuals and herds, but the knowledge about their genetic architecture is sparse, especially in swine. We have recently described three QTL for serum aspartate aminotransferase activity (sAST), and one of these maps to a region on SSC14 where the aspartate aminotransferase coding gene GOT1 is located. This QTL was only apparent under the acute burden of a model disease. The aim of the present study was to characterize GOT1 as a candidate gene and to test the effects of different GOT1 SNPs as potential quantitative trait nucleotides (QTNs) for sAST. Nine SNPs within GOT1 were identified, and SNP c.-793C>G significantly increased the QTL effects and narrowed the confidence interval from 90 to 15 cM. Additionally, we found a significant association of SNP c.-793C>G in a commercial outbred line, but with reversed phase. We conclude that GOT1 is a putative candidate gene for the sAST QTL on SSC14, and that SNP c.-793C>G is close to the responsible QTN.

Quantitative trait loci for white blood cell numbers in swine

Differential white blood cell counts are essential diagnostic parameters in veterinary practice but knowledge on the genetic architecture controlling variability of leucocyte numbers and relationships is sparse, especially in swine. Total leucocyte numbers (Leu) and the differential leucocyte counts, i.e. the fractions of lymphocytes (Lym), polymorphonuclear leucocytes [neutrophils (Neu), eosinophils (Eos) and basophils (Bas)] and monocytes (Mon) were measured in 139 F(2) pigs from a Meishan/Pietrain family, before and after challenge with the protozoan pathogen Sarcocystis miescheriana for genome-wide quantitative trait loci (QTL) analysis. After infection, the pigs passed through three stages representing acute disease, reconvalescence and chronic disease. Nine genome-wide significant and 29 putative, single QTL controlling leucocyte traits were identified on 15 chromosomes. Because leucocyte traits varied with health and disease status, QTL influencing the leucocyte phenotypes showed specific health/disease patterns. Regions on SSC1, 8 and 12 contained QTL for baseline leucocyte traits. Other QTL regions reached control on leucocyte traits only at distinct stages of the disease model. Two-thirds of the QTL have not been described before. Single QTL explained up to 19% of the phenotypic variance in the F(2) animals. Related traits were partly under common genetic influence. Our analysis confirms that leucocyte trait variation is associated with multiple chromosomal regions.

Quantitative trait loci for red blood cell traits in swine

Haematological traits are essential diagnostic parameters in veterinary practice but knowledge on the genetic architecture controlling variability of erythroid traits is sparse, especially in swine. To identify QTL for erythroid traits in the pig, haematocrit (HCT), haemoglobin (HB), erythrocyte counts (RBC) and mean corpuscular haemoglobin content (MCHC) were measured in 139 F(2) pigs from a Meishan/Pietrain family, before and after challenge with the protozoan pathogen Sarcocystis miescheriana. The pigs passed through three stages representing acute disease, reconvalescence and chronic disease. Forty-three single QTL controlling erythroid traits were identified on 16 chromosomes. Twelve of the QTL were significant at the genome-wide level while 31 were significant at a chromosome-wide level. Because erythroid traits varied with health and disease status, QTL influencing the erythroid phenotypes showed specific health/disease patterns. Regions on SSC5, 7, 8, 12 and 13 contained QTL for baseline erythroid traits, while the other QTL regions affected distinct stages of the disease model. Single QTL explained 9-17% of the phenotypic variance in the F(2) animals. Related traits were partly under common genetic influence. Our analysis confirms that erythroid trait variation differs between Meishan and Pietrain breeds and that this variation is associated with multiple chromosomal regions.

Mapping of quantitative trait loci affecting resistance/susceptibility to Sarcocystis miescheriana in swine

The outcome of infectious diseases in vertebrates is under genetic control at least to some extent. In swine, e.g., marked differences in resistance/susceptibility to Sarcocystis miescheriana have been shown between Chinese Meishan and European Pietrain pigs, and these differences are associated with high heritabilities. A first step toward the identification of genes and polymorphisms causal for these differences may be the mapping of quantitative trait loci (QTLs). Considering clinical, immunological, and parasitological traits in the above model system, this survey represents the first QTL study on parasite resistance in pigs. QTL mapping was performed in 139 F(2) pigs of a Meishan/Pietrain family infected with S. miescheriana. Fourteen genome-wide significant QTLs were mapped to several chromosomal areas. Among others, major QTLs were identified for bradyzoite numbers in skeletal muscles (F = 17.4; p < 0.001) and for S. miescheriana-specific plasma IgG(2) levels determined 42 days p.i. (F = 20.9; p < 0.001). The QTLs were mapped to different regions of chromosome 7, i.e., to the region of the major histocompatibility complex (bradyzoites) and to an immunoglobulin heavy chain cluster, respectively. These results provide evidence for a direct and causal role for gene variants within these gene clusters (cis-acting) in differences in resistance to S. miescheriana.

Genetic resistance to Sarcocystis miescheriana in pigs following experimental infection

Clinical and parasitological traits of Sarcocystis miescheriana differ in Pietrain and Meishan pigs. For further description and characterization of the genetic basis of this variation a F(2) family based on Pietrain boars and Meishan sows as founders was generated. One hundred and thirty-nine F(2) pigs were challenged orally at an age of 100 days with 50,000 sporozysts to produce the typical clinical picture of a moderate dose Sarcocystis infection. Heritabilities were estimated for clinical and clinical-chemical traits, for specific antibody responses to the infection and for bradyzoite numbers found in skeletal (Musculus longissimus dorsi: M.l.d.) and heart muscles at necropsy 70 days post-infection (p.i.) Apart from several low to moderate heritabilities, high heritabilities were observed for bradyzoite numbers in the M.l.d. (0.68), IgM antibody levels (0.74) during the acute (14 days p.i.) and titres of specific IgG antibodies (0.42) in the early stage of cyst formation (42 days p.i.). Marked heritabilities of these traits, which are basic for acute phase of the disease (14 days p.i.) or chronic Sarcocystosis presume genes that explain sufficient shares of variance (QTL). The model is considered valuable for screening of gene variants associated with resistance/susceptibility to Sarcocystis infection. Such gene variants could then be used in susceptibility-scoring or selection programs in the future.

Comparison of heterophil functions of modern commercial and wild-type Rio Grande turkeys

The purpose of the present study was to measure any functional differences in peripheral blood heterophils isolated from a commercial turkey line to wild-type Rio Grande turkeys. The phagocytosis of Salmonella enteritidis, oxidative burst (OXB) and degranulation (DGR) were used as parameters of heterophil functional efficiency in these studies. Blood was collected and heterophils isolated from each line of turkeys at days 4, 7, and 14 post-hatch. On days 4 and 7 post-hatch, heterophils from Rio Grande turkeys responded to phorbol A-myristate-13-acetate with significantly greater OXB activity than commercial line A. Results from the DGR assay also revealed a greater level of activity in Rio Grande heterophils when compared with heterophils from Line A turkeys. On day 14 post-hatch, heterophils from the commercial line A responded at similar or greater levels than Rio Grande turkey heterophils in the OXB and DGR assays. No differences in the phagocytosis of S. enteritidis were observed between the lines. These results indicate that the commercial Line A turkeys may be at an immunological disadvantage during the first days post-hatch when compared with their wild-type predecessors. Based on the results of these experiments, research into the differences and similarities between the innate immune response of commercial turkey lines and wild-type turkeys may illuminate areas where commercial lines can be improved to decrease losses due to disease and to decrease pathogen contamination of turkey products while preserving performance characteristics.

Characterization of swine leukocyte antigen polymorphism by sequence-based and PCR-SSP methods in Meishan pigs

Resource herds of swine leukocyte antigen (SLA)-characterized pigs are an important tool for the study of immune responses, disease resistance, and production traits. They are also valuable large animal models for biomedical research, such as transplantation. The Meishan breed of pig is an economically significant breed that is available at several research institutions in the United States. We have characterized the SLA polymorphism of the breeding stock in the herd maintained at the University of Illinois and developed a simple assay to SLA type individuals within that herd. We have used a reverse transcription-polymerase chain reaction (RT-PCR)-based SLA typing method to clone and DNA sequence 19 SLA alleles at three SLA class Ia (SLA-1, SLA-2, and SLA-3) and two SLA class II (SLA-DRB1 and SLA-DQB1) loci. Based on this sequence information, a rapid SLA typing assay was developed to discriminate each allele using PCR with sequence-specific primers (PCR-SSP). Using this method, we were able to characterize the entire Meishan breeding stock and identify four SLA haplotypes present in the herd. The combination of SLA typing by cloning and DNA sequencing with PCR-SSP is therefore a valuable tool for the characterization of SLA alleles and haplotypes in resource herds of pigs.

Evidence of breed-dependent differences in susceptibility to porcine circovirus type-2-associated disease and lesions

Porcine circovirus type 2 (PCV2) has been confirmed as the primary cause of postweaning multisystemic wasting syndrome (PMWS). However, in the field, PMWS is seen only in a small percentage of pigs infected with PCV2. The overall objective of the study reported here was to determine whether host genetic differences in the susceptibility to PCV2-associated disease exist among selected breeds of pigs. This study included Duroc (n = 23), Landrace (n = 19), and Large White (n = 21) pigs. The pigs were infected intranasally and intramuscularly at 5-7 weeks of age with PCV2. A portion of the pigs (31/63; 30.2%) had low passively acquired PCV2 antibodies at the time of infection. There were no differences in mean weight gain, rectal temperature, or respiratory score. Clinical disease compatible with PMWS was observed only in the Landrace pigs. Most of the PCV2-infected pigs had enlarged lymph nodes, and individual Duroc and Landrace pigs had mottled tan lungs. PCV2-associated lymphoid depletion and granulomatous inflammation were observed in pigs of all breeds. Three of 19 Landrace pigs and none of the Duroc or Large White pigs developed severe lymphoid lesions associated with large amounts of intralesional PCV2 antigen typical of PMWS. Compared with seronegative Landrace pigs, Landrace pigs that had low maternal antibodies at the time of PCV2 inoculation had significantly (P < 0.05) less-severe PCV2-associated lesions. The results suggest a predisposition of the Landrace pigs of this study to PCV2-induced disease and lesions, and that low levels of passively acquired antibodies are protective.

Innate immune traits differ between Meishan and Large White pigs

A panel of innate immune traits were compared between Meishan and Large White pigs. These pigs were of similar age and kept under the same environmental conditions to reduce non-genetically derived variation in immune traits. The animals were all apparently healthy and were not experimentally challenged with any pathogen during the study. The measures only required a small blood sample. Total white cell counts were similar between the pig breeds. However, the numbers of lymphocytes, neutrophils and monocytes differed significantly, with Meishans having higher neutrophil and monocyte counts and lower lymphocyte counts. Flow cytometric methods were used to determine quantitatively the characteristics and function of neutrophils and monocytes. Meishan neutrophils were smaller and less complex than Large White neutrophils, and phagocytosis of Escherichia coli and the ensuing oxidative burst was lower in Meishan neutrophils compared to Large White neutrophils. Monocyte phagocytosis of E. coli was significantly less than that of neutrophils in both breeds but the function of Meishan monocytes as measured by phagocytosis and tumour necrosis factor alpha (TNFalpha) release did not differ from that of Large White monocytes. Levels of acute phase proteins also differed between the breeds with a significantly higher proportion of Meishans having elevated serum amyloid A levels. However, Meishans had lower alpha(1)-acid glycoprotein levels than Large Whites and haptoglobin levels were similar. Such differences in innate immune traits may have implications in the resistance to infection by a broad range of pathogens and subsequent disease effects in these breeds. Further studies are warranted to investigate the genes underlying these traits.