Detection of porcine teschoviruses and enteroviruses by LightCycler real-time PCR

Characterization of an African Swine Fever Virus Field Isolate from Vietnam with Deletions in the Left Variable Multigene Family Region

In this paper, we report the characterization of a genetically modified live-attenuated African swine fever virus (ASFV) field strain isolated from Vietnam. The isolate, ASFV-GUS-Vietnam, belongs to p72 genotype II, has six multi-gene family (MGF) genes deleted, and an Escherichia coli GusA gene (GUS) inserted. When six 6-8-week-old pigs were inoculated with ASFV-GUS-Vietnam oro-nasally (2 × 105 TCID50/pig), they developed viremia, mild fever, lethargy, and inappetence, and shed the virus in their oral and nasal secretions and feces. One of the pigs developed severe clinical signs and was euthanized 12 days post-infection, while the remaining five pigs recovered. When ASFV-GUS-Vietnam was inoculated intramuscularly (2 × 103 TCID50/pig) into four 6-8 weeks old pigs, they also developed viremia, mild fever, lethargy, inappetence, and shed the virus in their oral and nasal secretions and feces. Two contact pigs housed together with the four intramuscularly inoculated pigs, started to develop fever, viremia, loss of appetite, and lethargy 12 days post-contact, confirming horizontal transmission of ASFV-GUS-Vietnam. One of the contact pigs died of ASF on day 23 post-contact, while the other one recovered. The pigs that survived the exposure to ASFV-GUS-Vietnam via the mucosal or parenteral route were fully protected against the highly virulent ASFV Georgia 2007/1 challenge. This study showed that ASFV-GUS-Vietnam field isolate is able to induce complete protection in the majority of the pigs against highly virulent homologous ASFV challenge, but has the potential for horizontal transmission, and can be fatal in some animals. This study highlights the need for proper monitoring and surveillance when ASFV live-attenuated virus-based vaccines are used in the field for ASF control in endemic countries.

First report on co-isolation and whole-genomic characterisation of mammalian orthorubulavirus 5 and mammalian orthoreovirus type 3 from domestic pigs in India

During a surveillance study to monitor porcine epidemic diarrohoea virus and transmissible gastroenteritis virus in India, a total of 1043 swine samples including faeces (n = 264) and clotted blood (n = 779) were collected and tested. Five samples (four faecal and one serum) showed cytopathic effects in Vero cells. Transmission electron microscopy of infectious cell supernatant revealed the presence of two types of virions. Next-generation sequencing (de novo) allowed the complete genome sequence of mammalian orthorubulavirus 5 (MRuV5; 15246 bp) and that of all 10 gene segments of mammalian orthoreovirus to be determined. Genetic analysis of MRuV5 revealed grouping of the Indian MRuV5 with isolates from various mammalian species in South Korea and China, sharing more than 99% nucleotide sequence identity. The deduced amino acid sequences of the HN, NP, and F genes of MRuV5 isolates showed three (92L, 111R, 447H), two (86S, 121S), and two (139T, 246T) amino acid substitutions, respectively, compared to previously reported virus strains. Phylogenic analysis based on S1 gene sequences showed the Indian MRV isolates to be clustered in lineage IV of MRV type 3, with the highest nucleotide sequence identity (97.73%) to MRV3 strain ZJ2013, isolated from pigs in China. The protein encoded by the MRV3 S1 gene was found to contain the amino acid residues 198-204NLAIRLP, 249I, 340D, and 419E, which are known to be involved in sialic acid binding and neurotropism. This is the first report of co-isolation and whole-genomic characterisation of MRuV5 and MRV3 in domestic pigs in India. The present study lays a foundation for further surveillance studies and continuous monitoring of the emergence and spread of evolving viruses that might have pathogenic potential in animal and human hosts.

Porcine teschovirus, sapelovirus, and enterovirus in Swiss pigs: multiplex RT-PCR investigation of viral frequencies and disease association

Porcine teschovirus (PTV), sapelovirus (PSV-A), and enterovirus (EV-G) are enteric viruses that can infect pigs and wild boars worldwide. The viruses have been associated with several diseases, primarily gastrointestinal, neurologic, reproductive, and respiratory disorders, but also with subclinical infections. However, for most serotypes, proof of a causal relationship between viral infection and clinical signs is still lacking. In Switzerland, there has been limited investigation of the occurrence of the 3 viruses. We used a modified multiplex reverse-transcription PCR protocol to study the distribution of the viruses in Swiss pigs by testing 363 fecal, brain, and placental or abortion samples from 282 healthy and diseased animals. We did not detect the 3 viruses in 94 placental or abortion samples or in 31 brain samples from healthy pigs. In brain tissue of 81 diseased pigs, we detected 5 PSV-A and 4 EV-G positive samples. In contrast, all 3 viruses were detected at high frequencies in fecal samples of both healthy and diseased pigs. In healthy animals, PTV was detected in 47%, PSV-A in 51%, and EV-G in 70% of the 76 samples; in diseased animals, frequencies in the 81 samples were 54%, 64%, and 68%, respectively. The viruses were detected more frequently in fecal samples from weaned and fattening pigs compared to suckling piglets and sows. Co-detections of all 3 viruses were the most common finding. Based on clinical and pathology data, statistical analysis yielded no evidence for an association of virus detection and disease. Further research is required to determine if pathogenicity is linked to specific serotypes of these viruses.

Detection and molecular characterization of porcine enterovirus G15 and teschovirus from India

Porcine enterovirus G (EV-G) and teschovirus (PTV) generally cause asymptomatic infections. Although both viruses have been reported from various countries, they are rarely detected from India. To detect these viruses in Western India, fecal samples (n = 26) of diarrheic piglets aged below three months from private pig farms near Pune (Maharashtra) were collected. The samples were screened by reverse transcription-polymerase chain reaction using conserved enterovirus specific primers from 5' untranslated region. For genetic characterization of detected EV-G strain, nearly complete genome, and for PTV, partial VP1 gene were sequenced. EV-G strain showed the highest identity in a VP1 gene at nucleotide (78.61%) and amino acid (88.65%) level with EV-G15, prototype strain. However, its complete genome was homologous with the nucleotide (78.38% identity) and amino acid (91.24% identity) level to Ishi-Ka2 strain (LC316832), unassigned EV-G genotype detected from Japan. The nearly complete genome of EV-G15 consisted of 7398 nucleotides excluding the poly(A) tail and has an open reading frame that encodes a 2170 amino acid polyprotein. Genetic analysis of the partial VP1 gene of teschovirus identified porcine teschovirus 4 (PTV-4) and putative PTV-17 genotype. To the best of our knowledge, this is the first report on nearly full genome characterization of EV-G15, and detection of PTV-4 and putative PTV-17 genotypes from India. Further, detection and characterization of porcine enteroviruses are needed for a comprehensive understanding of their genetic diversity and their association with symptomatic infections from other geographical regions of India.

Swine polioencephalomyelitis in Brazil: identification of Teschovirus A, Sapelovirus A, and Enterovirus G in a farm from Southern Brazil

Porcine encephalomyelitis can be associated with many etiologies, including viral agents, such as Porcine teschovirus (PTV), Porcine sapelovirus (PSV), and Porcine astrovirus (PoAstV). In this study, we investigated the presence of these viruses in a neurological disease outbreak in a swine farm in Southern Brazil. The piglet production farm unity had 1200 weaning piglets, and 40 piglets with neurological signs such as motor incoordination, paresis, and paralysis of hind limbs, with an evolution time of approximately 4 days. Among these, 10 piglets were submitted to postmortem examination. Gross lesions were restricted to a mild enlargement of the nerve roots and ganglia of spinal cord segments. The microscopic lesions were characterized by nonsuppurative encephalomyelitis and ganglioneuritis with evident neuronal degeneration and necrosis. Samples of the central nervous system (CNS), cerebrospinal fluid, and feces were collected and submitted to molecular analysis. PTV was identified in all samples of the CNS, while eight of the piglets were also positive for PSV, and seven were positive for Porcine enterovirus (EV-G). PoAstV was identified in a pool of feces of healthy animals used as controls. This study demonstrates the occurrence of encephalomyelitis associated with PTV on a swine farm in Southern Brazil, as well as the presence of other viruses such as PSV, EV-G, and PoAstV in the swineherd. Sequences of the fragments that were previously amplified by PCR showed a high similarity to PTV 6. Herein, we describe the first case report of severe swine polioencephalomyelitis associated with PTV in South America.

Detection and genetic analysis of a novel atypical porcine pestivirus from piglets with congenital tremor in Japan

Atypical porcine pestivirus (APPV), which has been confirmed to be associated with congenital tremor (CT) in pigs, is a newly discovered porcine virus that has been found in the Americas, Europe and Asia; however, no report of APPV in Japan has been published. We identified an APPV in the central nervous system of Japanese piglets with CT and firstly determined and analysed the complete genome sequence. Phylogenetic analysis using the complete genome nucleotide sequence of the Japanese APPV, named Anna/2020, and those of APPVs from the NCBI database showed that APPVs were divided into three genotypes (genotypes 1 to 3), and that Anna/2020 clustered with the genotype 3 APPV strains, but distantly branched from these strains. Pairwise complete coding region nucleotide sequence comparisons revealed that there was 94.0%- 99.7% sequence identity among the genotype 3 strains, while Anna/2020 showed 87.0%-89.3% identity to those genotype 3 strains, suggesting that Anna/2020 represents a novel APPV lineage within genotype 3. Retrospective examinations using RT-PCR revealed one genotype 1 and two novel genotype 3 APPVs from pigs without CT, and that novel genotype 3 APPVs have been prevalent in Japan since at least 2007.

Porcine rotavirus B as primary causative agent of diarrhea outbreaks in newborn piglets

Rotavirus (RV) is considered a major cause of acute viral gastroenteritis in young animals. RV is classified into nine species, five of which have been identified in pigs. Most studies worldwide have highlighted diarrhoea outbreaks caused by RVA, which is considered the most important RV species. In the present study, we described the detection and characterization of porcine RVB as a primary causative agent of diarrhoea outbreaks in pig herds in Brazil. The study showed a high frequency (64/90; 71.1%) of RVB diagnosis in newborn piglets associated with marked histopathological lesions in the small intestines. Phylogenetic analysis of the VP7 gene of wild-type RVB strains revealed a high diversity of G genotypes circulating in one geographic region of Brazil. Our findings suggest that RVB may be considered an important primary enteric pathogen in piglets and should be included in the routine differential diagnosis of enteric diseases in piglets.

Sapelovirus

Sapelovirus (SPV), an emerging virus in the family Picornaviridae, is detected in several animal and bird species irrespective of their age. Amid all SPVs, porcine sapeloviruses (PSVs) are more ubiquitously present all over the world in porcine population. These viruses are highly stable in different environmental conditions and spread easily within the susceptible animals mainly through faeco-oral route. Usually, PSVs cause asymptomatic infections but are also clinically associated with encephalomyelitis, respiratory distress, fertility disorders and skin lesions. PSV-associated outbreaks have been reported where death occurs due to polioencephalitis and respiratory paralysis. Till date, PSVs have been detected from several European and Asian countries with moderate-to-high prevalence and clinical course. Viral capsid proteins are immunogenic and mutations in these proteins are responsible for the diverse nature of the viruses. Further, genomic analysis shows the varied evolutionary patterns and the presence of recombination within PSV strains. These viruses also exist as concurrent infections with several enteric bacterial, viral and parasitic pathogens. Classical to modern biotechnological assays are in use to detect PSV involving virus isolation in cell culture, immunohistochemistry, conventional nucleic acid amplification techniques, quantitative real-time amplification assays and isothermal amplification molecular techniques. Till date, there is no vaccine available against PSVs.

Immunocytochemistry assay in BHK-21 cell line infected with Porcine Sapelovirus

The present study describes an immunocytochemistry (ICC) assay with self-raised hyperimmune sera and a Baby Hamster Kidney-21 (BHK-21) cell line infected with Porcine Sapelovirus (PSV). Sapelovivus/IVRI/SPF-c-6/2015 strain Indian PSV was isolated from the porcine IBRS-2 cell line and investigated for growth on non-porcine cell lines. After two passages, PSV was successfully grown in BHK-21 and produced the same cytopathic effects as in IBRS-2 such as shrinking of cytoplasm, rounding of cells and detachment of cells from the surface of flask within 24 h. For raising of hyperimmune sera, PSV was grown in IBRS-2 cell line up to the required volume and purified by ultracentrifugation. With self-raised hyperimmune sera in laboratory rats, ICC was performed in BHK-21 cells infected with PSV. Positive signals consisted of large granular aggregates of virus in the cytoplasm near the nucleus, suggesting that PSV can infect cell lines other than those of porcine origin.

Pathogenicity of porcine sapelovirus infection in mice

Porcine Sapelovirus (PSV) is a RNA virus belonging to a new genus Sapelovirus of family Picornaviridae. PSV has been isolated from India in 2016. In the present study, mice experiment was conducted to detect the ability of PSV to infect mice and its ability to induce pathological lesions. The intestinal and extra intestinal spread of the PSV virus in three week-old Swiss albino mice inoculated with PSV virus quantified by probe based real time PCR are described. Herein, three groups were made with 10 mice per group (both sex). The first group was infected through oral route (8×106, TCID50, 240 μl/mice) while the second through intra-peritoneal route (8×106, TCID50, 240 μl/mice) and the third group was inoculated with PBS of neutral pH orally and intra-peritoneal route. Seven mice (each from oral and intraperitoneal route and three from control group were sacrificed at 5th, 7th, 9th, 12th, 15th, 17th, 21st day post infection (DPI). Indian strain was able to replicate in mice organs up to 15 DPI in oral route and 9 DPI in intraperitoneal route. By real-time reverse transcription (RT) PCR, PSV was detected in most of the organs but with highest viral load in the small intestine and large intestine than extra-intestinal organs in the orally infected mice. In addition, this Indian strain is enteropathogenic but could spread to the bloodstream from the gut and disseminate to extra-intestinal organs. These results will contribute to our understanding of PSV pathogenesis.

Development of a Taqman-based real-time PCR assay for detection of porcine sapelovirus infection in pigs

The objective of the present study was to develop a rapid, simple, specific and sensitive Taqman-based real-time PCR assay for porcine sapelovirus (PSV) detection. Specific primers and probe were designed from the five untranslated regions (UTRs) of the viral genome. The detection limit of the real-time PCR was 10² copies. The specificity of the Taqman real-time PCR assay was evaluated using other animal viruses and nuclease free water as a negative control. Strong fluorescent signals were obtained only in the detection of PSV real-time PCR and conventional RT-PCR were preformed simultaneously on 90 faecal samples. Based on conventional RT-PCR study 17.7% (16/90) of the faecal samples were positive for PSV. Whereas 21 of 90 samples (23.3%) were positive by real-time RT-PCR. The results showed that real-time PCR was more sensitive than the conventional RT-PCR assay. In conclusion, the Taqman real-time PCR assay for detection of PSV developed, herein, is sensitive, specific, and reliable. This assay will be useful for clinical diagnosis, epidemiological, and pathogenesis studies.

Longitudinal survey of Teschovirus A, Sapelovirus A, and Enterovirus G fecal excretion in suckling and weaned pigs

Fecal samples from 27 pigs were longitudinally analyzed for Teschovirus A (TV-A), Sapelovirus A (SV-A), and Enterovirus G (EV-G) RNA presence. Suckling piglet fecal samples were negative for the three enteric picornaviruses. However, these picornaviruses were detected in 22/27 weaned pig fecal samples. This study provides new data on TV-A, SV-A, and EV-G infection dynamics.

Pathologic and molecular findings associated with atypical porcine pestivirus infection in newborn piglets

Atypical porcine pestivirus (APPV) has been associated with congenital tremor (CT) type A-II in newborn piglets. Although the number of APPV-based studies is increasing, the associated pathologic findings in infected piglets are underreported. This study describes the histopathologic features of spontaneous APPV infection in CT-affected piglets and complements a previous report by our group. Four two-day-old piglets with CT were evaluated by histopathology, immunohistochemistry (IHC), and molecular assay. The main histopathologic findings at the brain and spinal cord included neuronal necrosis, gliosis, neuronophagia, satellitosis, demyelination, Wallerian degeneration, and Purkinje cell necrosis. An IHC assay designed to detect the proliferation of glial fibrillary acidic protein (GFAP) in affected areas of the brain and spinal cord revealed that the proliferation of GFAP + cells and fibers was predominant in APPV-infected piglets relative to asymptomatic piglets of the same age group. The RT-nested-PCR assays identified APPV RNA in the cerebrum, cerebellum, and brainstem of all piglets; other viruses known to produce similar manifestations were not detected. These results suggest that the APPV-induced histopathologic findings are predominantly degenerative and necrotic and correlate with our previous findings. Consequently, it is proposed that neuronal necrosis, gliosis, neuronophagia, and satellitosis should be considered as important histologic features of APPV-induced infection in symptomatic CT piglets.

Congenital Microphthalmic Syndrome in a Swine

A 17-week-old crossbred finishing pig was presented for lameness of approximately one week. Clinical evaluation, including ophthalmologic examination, revealed ataxia, partial flaccid paresis of the pelvic limbs, skin lesions at feet and claws, and severely reduced vision/blindness. Both eyes had multiple persistent pupillary membranes (iris-to-iris and iris-to-lens) and hypermature cataracts. Histopathological examination of the eyes revealed microphthalmia, microphakia with cataract formation, myovascularised membrane in the vitreous, retinal detachment, and retinal dysplasia. Microscopic examination of tissues collected postmortem demonstrated nonsuppurative polioencephalomyelitis with the most prominent inflammatory lesions in the lumbar spinal cord. Subsequently, presumed Teschen/Talfan disease was confirmed by porcine teschovirus identification in the spinal cord using the reverse transcription-polymerase chain reaction (RT-PCR). To the authors' knowledge, this is the first case report describing in detail histopathological changes in the porcine congenital microphthalmic syndrome.

Molecular characterization of a porcine teschovirus HuN-1 isolate proliferating in PK-15 cell

BACKGROUND

Porcine teschoviruses (PTVs) are small non-enveloped viruses with single-stranded, positive sense genomic RNA, belonging to the family Picornaviridae. Natural infections of teschoviruses are limited to pigs.

RESULTS

In this study, a PTV HuN-1 was found that it could be proliferated in PK-15 cell, and it came from the pig fecal samples from Hunan province, in central China. The complete genome of the HuN-1 was amplified by RT-PCR and sequenced. The complete genome of HuN-1 isolate is 7098 nt, which shares the highest sequence identity (85.9%) with the PTV 8 strain of Jilin/2003/2 and Fuyu/2009/2. The HuN-1 isolate contains only one ORF (from 320 to 7039 nt) coding a 2240 amino acid polyprotein. Aligned sequences show that more mutations occurred in the structural region than in the nonstructural region. Phylogenetic analysis showed that HuN-1 isolate did not clustered with the hitherto reported strains, according to P1 sequences, forming a subgroup in the PTV cluster.

CONCLUSION

In this study, complete genome of PTV HuN-1 was cloned and sequenced. Detection and characterization of further PTV strains from different geographic areas are important to understand the worldwide distribution and heterogeneity (serotype) of PTVs and their association with symptomatic infections in pigs.

Viruses associated with congenital tremor and high lethality in piglets

The recently described atypical porcine pestivirus (APPV) has been associated with congenital tremor (CT) type A-II in piglets in different countries. Another important neurological pathogen of pigs is porcine teschovirus (PTV), which has been associated with non-suppurative encephalomyelitis in pigs with severe or mild neurological disorders. There have been no reports of APPV and/or PTV coinfection associated with CT or encephalomyelitis in Brazilian pig herds. The aim of this study was to describe the pathological and molecular findings associated with simultaneous infection of APPV and PTV in piglets with clinical manifestations of CT that were derived from a herd with high rates of CT-associated lethality. In 2017, three piglets from the same litter with CT died spontaneously. The principal pathological alterations in all piglets were secondary demyelination and hypomyelination at the cerebellum, brainstem and spinal cord confirmed by histopathology and luxol fast blue-cresyl violet stain. Additional significant pathological findings included multifocal neuronal necrosis, neuronophagia and gliosis found in the cerebral cortex and spinal cord of all piglets, while atrophic enteritis and mesocolonic oedema were observed in some of them. APPV and PTV RNA were detected in the central nervous system of affected piglets, and PTV was also detected in the intestine and faeces. The pathological alterations and molecular findings together suggest a dual infection due to APPV and PTV at this farm. Moreover, the combined effects of these pathogens can be attributed to the elevated piglet mortality, as coinfections involving PTV have a synergistic effect on the affected animals.

Senecavirus A: An Emerging Vesicular Infection in Brazilian Pig Herds

Vesicular diseases are clinically and economically important infections that affect farm animals. North American studies have suggested that Senecavirus A infection might be associated with a vesicular disease in pigs known as porcine idiopathic vesicular disease (PIVD). In the beginning of 2015, outbreaks of porcine vesicular disease have occurred in six Brazilian states from three geographical regions. Official diagnostic tests were performed with negative results for classical vesicular diseases of compulsory reporting. This study investigated Senecavirus A infection in PIVD outbreaks in which other aetiological agents were ruled out. A primer set was designed to amplify a 542-bp product size of VP3/VP1 region of Senecavirus A genome in RT-PCR assay. Primer specificity was analysed in silico and in porcine biological specimens. For this, clinical specimens were collected from eight pig herds affected with PIVD, including vesicular fluid (n = 4) and swabs (n = 7) and scrapings of ruptured vesicles and ulcerative lesions (n = 5) from weaned and adult pigs. Clinically healthy animals (n = 52) of PIVD-affected and non-affected pig herds also were evaluated for Senecavirus A infection. The 16 samples from PIVD-affected animals were positive for Senecavirus A in the RT-PCR assay, while none of the clinically healthy pigs were detected with the virus. Sequencing analysis revealed high nucleotide (87.6-98.5%) and amino acid (95-99.4%) similarities to SVV-01 prototype and other Senecavirus A strains from North American pigs. Primer set presented herein was suitable for molecular characterization of Senecavirus A. The results suggest that Senecavirus A was the aetiological agent of the vesicular disease outbreaks in the evaluated pig herds. This is the first study to report the Senecavirus A infection in clinically affected pigs outside of North America. Senecavirus A was considered a novel emerging pathogen associated with an important vesicular disease in Brazil.

Molecular survey of porcine teschovirus, porcine sapelovirus, and enterovirus G in captive wild boars (Sus scrofa scrofa) of Paraná state, Brazil

AbstractPorcine teschovirus (PTV), porcine sapelovirus (PSV), and enterovirus G (EV-G) are infectious agents specific to pig host species that are endemically spread worldwide. This study aimed to investigate the natural infection by these porcine enteric picornaviruses in wild boars (Sus scrofa scrofa) of Paraná state, Brazil, and to evaluate peccaries (Pecari tajacu and Tayassu pecari) as alternative host species for these viruses. Fecal samples (n=36) from asymptomatic wild boars (n=22) with ages ranging from 2 to 7 months old (young, n=14) and 2 to 4 years old (adult, n=8) and from peccaries (6 to 8 months old, n=14) were collected from a farm and a zoo, respectively, both located in Paraná state. Reverse transcription-polymerase chain reaction (RT-PCR) and nested-PCR (n-PCR) assays targeting the 5'non-translated region of the virus genome were used for screening the viruses. Porcine enteric picornaviruses were detected in 12 out of the 22 wild boar fecal samples. According to each of the viruses, EV-G was most frequently (11/22, 50%) detected, followed by PTV (10/22, 45.5%) and PSV (4/22, 18.2%). Regarding the age groups, young wild boars were more frequently (9/14, 64.3%) infected with PTV, PSV, and EV-G than adult animals (3/8, 37.4%). One n-PCR amplified product for each of the viruses was submitted to sequencing analysis and the nucleotide sequences were compared with the related viruses, which showed similarities varying from 97.7% to 100% for PTV, 92.4% to 96.2% for PSV, and 87.1% to 100% for EV-G. Peccaries tested negative for the viruses and in this study they did not represent infection reservoirs. This study is the first to report the molecular detection of PTV, PSV, and EV-G from captive wild boars in a South American country and the first to screen peccaries as alternative host species for porcine enteric picornavirus.

The presence of six potentially pathogenic viruses in pigs suffering from post-weaning multisystemic wasting syndrome

Background

Porcine circovirus type 2 (PCV2) is an etiological agent of porcine circovirus diseases (PCVDs). Post-weaning multisystemic wasting syndrome (PMWS) as the most important PCVD is considered a multifactorial disease. It was demonstrated that not only PCV2 but several viruses are associated with PMWS. Studies of viral co-infections in PMWS pigs led often to controversial results. The aim of this work was to determine the presence of emerging (PRRSV), re-emerging (PTV) and newly-emerging (TTSuV1, TTSuV2, PBoV1) viruses in samples of dead pigs suffering from PMWS. The impact of vaccination against PCV2 and the influence of age on the occurrence of single and multiple viral infections in pigs were also investigated.

Results

Viruses were detected by PCR, RT-PCR and real-time PCR in the pooled tissue samples (lymph nodes, liver and spleen) of pigs with PMWS (n = 56) which were divided into three groups: suckling piglets, post-weaning pigs and fattening pigs. In addition, lymph node samples were collected from apparently healthy fattening pigs (n = 59). The effect of vaccination against PCV2 with Ingelvac CircoFlex vaccine was also investigated. Between non-vaccinated pigs, the highest prevalence of individual viruses and multiple viral infections were found in diseased post-weaning and fattening animals with PMWS. Severe clinical disease was observed in swine co-infected with PCV2 and PRRSV. The prevalence of TTSuV1 and TTSuV2 was high in all groups of pigs and did not appear to have a significant effect on the syndrome. Simultaneous infection with TTSuV1 and PBoV1 was frequently confirmed in pigs with PMWS. No healthy pig was found to be infected with PRRSV, PTV or PBoV1. Vaccination against PCV2 did not influence the prevalence of TTSuVs, but significantly protected pigs against multiple viral infections.

Conclusions

Post-weaning PMWS pigs were more often co-infected with viral pathogens than suckling or fattening pigs. Co-infection with PRRSV enforces clinical signs of PMWS, the influence of other viral co-infections is not clear. Vaccination against PCV2 significantly reduced viral co-infections in pigs.

Rapid and real-time detection of Porcine Sapelovirus by reverse transcription loop-mediated isothermal amplification assay

The present study describes the development and validation of a one-step, single-tube, and real-time reverse transcription loop-mediated isothermal amplification (RT-LAMP) detecting Porcine Sapelovirus. RT-LAMP characterized by one strand displacement reaction with the specific stem-loop structure and Bst DNA polymerase could be finished in 60 min under isothermal condition at 63 °C. RT-LAMP assay showed higher sensitivity with 10(1) copies/μL than RT-PCR for the detection of Sapelovirus. The specificity of RT-LAMP assay was validated by the absence of any cross-reaction with other closely related virus in Picornaviridae group and other common virus causing porcine diarrhea. 7 positive Sapelovirus infection out of 63 fecal samples were identified using RT-LAMP, while 5 positive samples were determined by a conventional RT-PCR. A cost-effective method for Saplovirus detection with high sensitivity and specificity was developed and evaluated.

Multiple models of porcine teschovirus pathogenesis in endemically infected pigs

Porcine teschoviruses (PTVs) belong to the genus Teschovirus within the family Picornaviridae. PTVs are universal contaminants in pig herds in endemic and multi-infection status. To further the understanding of PTV pathogenesis in endemically infected pigs, a set of samples was studied by real time reverse transcription PCR (qRT-PCR) to quantitate viral loads in tissues and by in situ hybridization (ISH) to locate PTV signals in target cells, both targeting the 5'-NTR. cRNA of PTV-1 and PTV-7, in vitro transcribed from cloned fragments of 5'-NTR of 2 viruses, was used to construct standard curves and to run parallel in qRT-PCR, which had detection limits of 10(1) copies/per reaction, with a linearity in between 10(1) and 10(7) copies/per reaction and correlation coefficients of 0.997-0.9988. The qRT-PCR specifically amplified RNA from PTV-1 to -11, while excluding those of Sapelovirus, PEV-9 and PEV-10. Inguinal lymph node (LN) had the highest viral load of all (assuming 100%), followed by ileac LN (89-91%), tonsil (66-68%), ileum (59-60%), spleen (38-40%), and kidney (30-31%), with the least in brain (22.9%) of the inguinal LN. The 22.9% load in brain was higher than that anticipated from a simple fecal-oral-viremia operative model. The results suggested in addition that intranasal infection and retrograding axonal infection from the tonsils were equally operative and significant. ISH revealed PTV signals in a wider variety of tissue cell types than before. PTV signals were noted most impressively in neurons of the cerebral cortex and hippocampus and in the dark zone of the germinal center and adjacent paracortex of regional LN. Multiple operative models indicated that PTVs seemed to have no difficulty invading the brain. The key to whether encephalitis would ensue resided in the animal's immune status and topographic differences of neurons' susceptibilities to PTVs. When common co-infected agents are present, as is typical in the field, PTVs may synergize in causing diseases.

Phylogeny and evolution of porcine teschovirus 8 isolated from pigs in China with reproductive failure

A porcine teschovirus (PTV) was isolated from a dead piglet from a herd of 200 sows showing reproductive failure in Fuyu, Heilongjiang Province, China. Sequencing of most of the genome of this isolate, designated Fuyu/2009, revealed that is was a PTV-8 isolate, closely related to a previously identified Chinese PTV-8 strain (Jilin/2003). Both Chinese strains vary from the European PTV-8 strains by different clustering of the 3CD sequences. Infection with these viruses may be associated with pronounced diseases.

Development of a reverse transcription loop-mediated isothermal amplification assay for detection of Porcine teschovirus

Loop-mediated isothermal amplification (LAMP) is a sensitive method for DNA amplification. In the present report, the development of a single-tube, one-step, real-time accelerated reverse transcription (RT)-LAMP for the detection of Porcine teschovirus (PTV) is described. Six designed primers amplified target gene sequences successfully at constant temperature (65 °C) within 1 hr, and the amplification results could be visualized directly by the naked eye. The sensitivity of the LAMP was 10 times higher than that of conventional polymerase chain reaction, and no cross-reactivity was found when the genomes of other common swine pathogens were subjected to the RT-LAMP system. When 43 clinical samples were tested by the RT-LAMP method, results indicated that the test is simple, rapid, accurate, and sensitive for the detection of PTV.

Porcine teschovirus polioencephalomyelitis in western Canada

Beginning in 2002, a small number of pig farms in western Canada began reporting 4-7-week-old pigs with bilateral hind-end paresis or paralysis. Low numbers of pigs were affected, some died, most had to be euthanized, and those that survived had reduced weight gains and neurological deficits. Necropsies revealed no gross lesions, but microscopic lesions consisted of a nonsuppurative polioencephalomyelitis, most severe in the brain stem and spinal cord. The lesions were most consistent with a viral infection. Tests for circovirus, Porcine reproductive and respiratory syndrome virus, coronavirus, Rabies virus, and Pseudorabies virus were negative. Using immunohistochemistry, virus neutralization, fluorescent antibody test, and nested reverse transcription polymerase chain reaction, Porcine teschovirus was identified in tissues from affected individuals. To the authors' knowledge, this is the first report of teschovirus encephalitis in western Canada and the first reported case of polioencephalomyelitis in pigs in Canada, where teschovirus was confirmed as the cause.

Evaluation of a fluorogenic real-time reverse transcription-polymerase chain reaction method for the specific detection of all known serotypes of porcine teschoviruses

Performance of a real-time reverse-transcription polymerase chain reaction method for the rapid, simple and reliable detection of porcine teschovirus (PTV) was assessed. The method was based on the use of a set of oligonucleotides consisting of two specific primers and a fluorogenic TaqMan-MGB probe. Reverse transcription and PCR reactions were performed sequentially in one step. As a result the whole procedure was simple and rapid, taking less than 3h for completion. The method reacted in a dose-dependent manner with prototype strains for the eleven known PTV serotypes (PTV1-11), with higher analytical sensitivity than other gel-based RT-PCR methods described, which were performed in parallel to allow for a comparison. The assay did not cross-react with other related viruses or porcine viruses tested. The diagnostic performance of the method was analyzed using a panel of field samples consisting of pig fecal and pig slurry samples. As a conclusion, this technique is adequate and convenient for porcine teschovirus detection, both for diagnosis as well as in environmental investigations.

Pathogenicity and molecular characterization of emerging porcine reproductive and respiratory syndrome virus in Vietnam in 2007

In 2007, Vietnam experienced swine disease outbreaks causing clinical signs similar to the 'porcine high fever disease' that occurred in China during 2006. Analysis of diagnostic samples from the disease outbreaks in Vietnam identified porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV-2). Additionally, Escherichia coli and Streptococcus equi subspecies zooepidemicus were cultured from lung and spleen, and Streptococcus suis from one spleen sample. Genetic characterization of the Vietnamese PRRSV isolates revealed that this virus belongs to the North American genotype (type 2) with a high nucleotide identity to the recently reported Chinese strains. Amino acid sequence in the nsp2 region revealed 95.7-99.4% identity to Chinese strain HUN4, 68-69% identity to strain VR-2332 and 58-59% identity to strain MN184. A partial deletion in the nsp2 gene was detected; however, this deletion did not appear to enhance the virus pathogenicity in the inoculated pigs. Animal inoculation studies were conducted to determine the pathogenicity of PRRSV and to identify other possible agents present in the original specimens. Pigs inoculated with PRRSV alone and their contacts showed persistent fever, and two of five pigs developed cough, neurological signs and swollen joints. Necropsy examination showed mild to moderate bronchopneumonia, enlarged lymph nodes, fibrinous pericarditis and polyarthritis. PRRSV was re-isolated from blood and tissues of the inoculated and contact pigs. Pigs inoculated with lung and spleen tissue homogenates from sick pigs from Vietnam developed high fever, septicaemia, and died acutely within 72 h, while their contact pigs showed no clinical signs throughout the experiment. Streptococcus equi subspecies zooepidemicus was cultured, and PRRSV was re-isolated only from the inoculated pigs. Results suggest that the cause of the swine deaths in Vietnam is a multifactorial syndrome with PRRSV as a major factor.

Genotyping of Porcine Teschovirus from Nervous Tissue of Pigs with and without Polioencephalomyelitis in Indiana

Porcine teschovirus (PTV) was isolated in cell culture and/or demonstrated by polymerase chain reaction in samples of brain and/or spinal cord in pigs in Indiana during the 2002–2007 period. Testing was initiated on pigs originating from populations exhibiting nervous clinical disease and/or pigs with microscopic lesions in central nervous tissues, indicating viral encephalitis and/or myelitis. Virus was demonstrated in pigs with and without lesions as well as with and without nervous clinical disease. Nucleotide sequence analysis of the 5′-nontranslated region of the viral genome revealed that these isolates had low-level genetic heterogeneity but were homologous to porcine PTV serotype 1 (PTV-1). These findings indicate that low-to-moderate virulence strains of PTV with some homology to PTV-1 are endemic in many swineherds of Indiana and are associated with subclinical and clinical nervous disease in weaned pigs.

Rapid pre-clinical detection of classical swine fever by reverse transcription loop-mediated isothermal amplification

The usefulness of reverse transcription loop-mediated isothermal amplification (RT-LAMP) for rapid pre-clinical detection of classical swine fever virus (CSFV) infection was evaluated. The RT-LAMP reaction could be finished in 60 min under isothermal condition at 65 °C by employing a set of four primers targeting the 5′ untranslated region of CSFV. The RT-LAMP assay of CSFV showed higher sensitivities than that of RT-PCR, with a detection limit of 5 copies per reaction. No cross-reactivity was observed from the samples of other related viruses including porcine circovirus type 2, porcine parvovirus, porcine pseudorabies virus, Japanese encephalitis virus, and porcine reproductive and respiratory syndrome virus. The detection rates of CSFV RT-LAMP, RT-PCR and virus isolation for samples including blood, tonsil, nasal and rectal swabs from uninoculated pigs without any clear clinical symptom were 89%, 78% and 71%, respectively. Furthermore, all of the assays showed higher sensitivity for blood and tonsil swabs samples than nasal and rectal swabs. These results indicate that the CSFV RT-LAMP assay is a valuable tool for its rapid, cost-effective detection and has potential usefulness for rapid pre-clinical detection and surveillance of classical swine fever in developing countries.

Antigenic properties of porcine teschovirus 1 (PTV-1) Talfan strain and molecular strategy for serotyping of PTVs

For reliable diagnosis of porcine teschovirus (PTV) infection we created an RT-PCR-based molecular strategy for serotyping that encompassed the dominant neutralizing antigenic site of PTV, followed by phylogenetic analyses of amplicons. We identified neutralizing antigenic sites of PTV-1 Talfan strain through epitope mapping of neutralizing monoclonal antibodies (MAbs), using synthetic peptides spanning the capsid proteins. All 11 MAbs obtained recognized peptides in the EF loop ("puff") of VP2 protein. Two MAbs concurrently reacted to peptides, one in the GH loop of VP1 and one in the VP1 C terminus. Three-dimensional modeling of Talfan capsid protein predicted exposure of all these sites on the virion surface in a close line centered around puff. We then designed a single pair of degenerate primers to VP2 and amplified the region of approximately 320 bp encompassing puff in 8 PTV prototype strains and 6 field isolates. Phylogenetic analyses of the puff sequences of 11 prototype strains and 34 field isolates obtained from databanks showed that all homotypic strains (both field and prototype) were always monophyletic, except for one 'untypable' Japanese strain. This RT-PCR-based strategy appears to be a reliable surrogate for serotyping and could facilitate the diagnosis and epidemiological study of PTV infection.

Validation of RT-PCR Assays for Molecular Characterization of Porcine Teschoviruses and Enteroviruses

Porcine enteroviruses (PEVs) and teschoviruses (PTVs) are described as causative agents of neurological disorders, fertility disorders and dermal lesions of swine. Difficulties in the serological detection of these viruses may lead to a significant underestimation of infections with clinical symptoms. With the recent availability of genome sequence data for all the serotypes, molecular diagnosis is a possibility. The present study describes a new approach to molecular 'serotyping' of PTVs and PEV-B viruses, involving the amplification and sequencing of a genomic fragment of the VP1 coding region. A molecular characterization of Italian entero-teschovirus isolates was performed using a set of previously published and newly designed polymerase chain reaction primers. A total of 33 porcine isolates and 10 reference strains were analysed. Porcine enterovirus-B samples were first diagnosed as positive for enterovirus by amplification of the 5'-non-translated region. Samples were then typed by amplification and sequencing of a portion of the VP1 coding region. Porcine enterovirus-A and PTVs were detected by a published assay in the 5'-NC region that allows them to be differentiated according to the size of amplification product, using the same set of primers. For serotype characterization of PTV, we evaluated four different regions: the N terminus of the capsid protein VP2, the region encoding for RNA-dependent RNA polymerase, and the capsid VP1 and VP4 regions. The newly designed primers in the VP1 region was proved to be broad in range and suitable for serotype assessment and therefore constitute a useful diagnostic tool for molecular diagnosis of porcine teschovirus/enterovirus strains and for the study of molecular epidemiology and evolution of these viruses.

Development of a real-time PCR assay based on primer-probe energy transfer for the detection of swine vesicular disease virus

A real-time PCR assay based on primer-probe energy transfer (PriProET) was developed to detect swine vesicular disease virus (SVDV). Specificity tests of SVDV and heterologous virus showed specific amplification of SVDV strains only. The amplification plot for the closely related Coxsackievirus B5 remained negative. The sensitivity of assay was five copies of viral genome equivalents. A key point of the assay is tolerance toward mutations in the probe region. Melting curve analysis directly after PCR, with determination of probe melting point, confirmed specific hybridisation of the SVDV strains. Eight of twenty SVDV strains tested, revealed shifted melting points that indicated mutations in the probe region. All predicted mutations were confirmed by nucleotide sequencing. With the PriProET system there is a chance to identify phylogenetically divergent strains of SVDV, which may appear negative in other probe-based real-time PCR assays. At the same time, any difference in melting points may provide an indication of divergence in the probe region. The high sensitivity, specificity, and tolerance toward mutations in the probe region of the SVDV PriProET assay may improve the early and rapid detection of a wide range of SVDV strains, allowing reduced turnaround time and the use of high-throughput, automated technology.

Comparison of a LightCycler-based real-time PCR for quantitation of Epstein-Barr viral load in different clinical specimens with semiquantitative PCR

Measurement of viral load is important in predicting and monitoring of Epstein-Barr virus (EBV)-associated diseases especially in immunocompromised patients. The objectives of this study were the development of a LightCycler-based real-time PCR assay using primers and probes which recognize the virus capsid antigen p23-encoding region and its comparison to the semiquantitative PCR. The LightCycler protocol shows a high degree of specificity and inter- and intra-assay reproducibility. Concerning sensitivity, a good correlation between both methods was demonstrated for standard plasmid DNA, reference DNA isolated from the EBV-genome containing Namalwa cell line, and DNA extracted from plasma/cerebrospinal fluid (CSF). The detection limit was determined with 1 copy/microl eluate for the standard plasmid DNA and with 500 copies/ml plasma or CSF. For DNA derived from peripheral blood mononuclear cells (PBMCs), a decrease of sensitivity by factor 10-100 was found when larger amounts of background DNA (500 and 100 ng) were used presuming an inhibitory effect of cellular DNA. This was supported by running dilutions of the plasmid standard carried out with EBV-negative Ramos cell DNA. Thus, the cut-off level was estimated with 100-500 copies/10(5) PBMCs, when 50 or 10 ng total DNA were tested. The results indicate that the real-time PCR described here is a first line tool for the determination of viral load in plasma and CSF. Semiquantitative nested PCR is used for screening of PBMCs viral load. Positive specimens containing more than 500 copies/10(5) cells are measured for exact values by real-time PCR. To circumvent inhibitory effects of cellular DNA, measurements should be carried out generally with 50-10 ng DNA.

Investigation of pseudorabies virus latency in nervous tissues of seropositive pigs exposed to field strain

The prevalence and quantity of latent pseudorabies virus (PrV) in nervous tissues of pigs exposed to field strain in Korea was investigated by nested and real-time PCR. Nervous tissues including trigeminal ganglion (TG), olfactory bulb (OB), and brain stem (BS) were collected from 94 seropositive pigs. PrV latent infection in nervous tissues was initially investigated by nested PCR targeting three glycoprotein genes (gB, gE, and gG). Based on the obtained result, latent infection was detected in 95.7% of screened animals. Furthermore, it was revealed that the examined tissues harbored different copy numbers of latent PrV genome ranging from <10(2.0) to 10(7.1) copies per microgram of genomic DNA in real-time PCR analysis. These results show that under normal conditions, levels of latent PrV in the nervous tissues of pigs can vary across a wide range. Therefore, the data presented here provides information regarding control of the endemic state of PrV in Korea.

Detection and monitoring of virus infections by real-time PCR

The employment of polymerase chain reaction (PCR) techniques for virus detection and quantification offers the advantages of high sensitivity and reproducibility, combined with an extremely broad dynamic range. A number of qualitative and quantitative PCR virus assays have been described, but commercial PCR kits are available for quantitative analysis of a limited number of clinically important viruses only. In addition to permitting the assessment of viral load at a given time point, quantitative PCR tests offer the possibility of determining the dynamics of virus proliferation, monitoring of the response to treatment and, in viruses displaying persistence in defined cell types, distinction between latent and active infection. Moreover, from a technical point of view, the employment of sequential quantitative PCR assays in virus monitoring helps identifying false positive results caused by inadvertent contamination of samples with traces of viral nucleic acids or PCR products. In this review, we provide a survey of the current state-of-the-art in the application of the real-time PCR technology to virus analysis. Advantages and limitations of the RQ-PCR methodology, and quality control issues related to standardization and validation of diagnostic assays are discussed.

Enteric viruses of humans and animals in aquatic environments: health risks, detection, and potential water quality assessment tools

Waterborne enteric viruses threaten both human and animal health. These pathogens are host specific and cause a wide range of diseases and symptoms in humans or other animals. While considerable research has documented the risk of enteric viruses to human health from contact with contaminated water, the current bacterial indicator-based methods for evaluation of water quality are often ineffectual proxies for pathogenic viruses. Additionally, relatively little work has specifically investigated the risk of waterborne viruses to animal health, and this risk currently is not addressed by routine water quality assessments. Nonetheless, because of their host specificity, enteric viruses can fulfill a unique role both for assessing health risks and as measures of contamination source in a watershed, yet the use of animal, as well as human, host-specific viruses in determining sources of fecal pollution has received little attention. With improved molecular detection assays, viruses from key host groups can be targeted directly using PCR amplification or hybridization with a high level of sensitivity and specificity. A multispecies viral analysis would provide needed information for controlling pollution by source, determining human health risks based on assessments of human virus loading and exposure, and determining potential risks to production animal health and could indicate the potential for the presence of other zoonotic pathogens. While there is a need to better understand the prevalence and environmental distribution of nonhuman enteric viruses, the development of improved methods for specific and sensitive detection will facilitate the use of these microbes for library-independent source tracking and water quality assessment tools.