Attila Cságola

Genetic characterization of type 2 porcine circoviruses detected in Hungarian wild boars

Summary.Porcine circoviruses (PCV) are present in pigs worldwide; they are grouped into two types: PCV1 comprising non-pathogenic viruses and PCV2 responsible for several clinical manifestations. Both types are frequently detected in domestic pigs, the prevalence and role of PCV in wild boars however, is not well studied. During the years 2002–2003 over 2000 organ samples of Hungarian wild boars were collected, grouped and samples from 307 different animals were tested by polymerase chain reaction for the presence of PCV. 35.5% of the wild boars were positive for one or both PCV types and PCV2 was detected in 20.5% of the animals. The PCV2 viruses were divided into 7 groups (WB-H1-7) based on sequencing data and genomes representing these groups were sequenced completely. The wild boar PCV2 groups were distributed evenly in the geographical region, regardless of the time and place of collection. The phylogenetic analysis of the PCV2 sequences of wild boar and domestic pig origin showed the possibility of an epidemiological link between wild boar and domestic pig infections. Interestingly, the complete nucleotide sequence of the viruses and the predicted amino acid sequence of the replication associated protein (ORF1) grouped the viruses similarly, whereas the capsid protein (ORF2) comparisons revealed different relations among the groups, suggesting the possibility of genomic recombination in PCV2.

Detection, prevalence and analysis of emerging porcine parvovirus infections

A number of newly identified porcine parvoviruses had been described during the last decade, but the presence and prevalence of these viruses are unknown in Hungary and only partly known for Europe. The present study was conducted to detect and measure the prevalence of these viruses, namely porcine parvovirus (PPV) 2, PPV3, PPV4, porcine bocavirus (PBoV) 1, PBoV2, PBo-likeV and the 6V and 7V parvoviruses. The prevalence of PPV1 and porcine circovirus type 2 (PCV2) was also investigated. Faecal samples, blood serum samples, organ tissues, foetuses and semen were collected from different swine herds in Hungary and tested by polymerase chain reaction methods specific for the different viruses. The results indicated that all of the examined parvoviruses were present in Hungary, hence in Europe. The prevalence was 18.1% for PCV2, 0.5 % for PPV1, 6.4% for PPV2, 9.7% for PPV3, 6.4% for PPV4, 1.5% for PBo-likeV, 4.8% for PBoV1 and PBoV2 and 1.8% for 6V and 7V. Based on the analysis of partial PPV4 and PBo-likeV sequences, these viruses showed a high degree of sequence conservation, whereas PPV3 and the majority of PPV2, PBoV1, PBoV2, 6V and 7V sequences showed higher variability. Possible sites of recombination were also identified between PBoV1 and PBoV2 genomes.

First detection and analysis of a fish circovirus

Circoviruses are present worldwide in birds and pigs but their occurrence in fish has not yet been reported. Recently, increased mortality was observed in barbel fry (Barbus barbus) in Hungary. This paper reports the detection of previously unknown circular viral DNA genomes in barbels by the use of a circovirus-specific wide-range nested PCR. The analysis of two complete genomes (Barbel circovirus, BaCV1 and BaCV2) indicated that they belonged into a new genetic group within the family Circoviridae, distinct from known circoviruses and circovirus-like genomes. Their genome size was 1957 bases and contained two major ORFs similar to the capsid and replication-associated protein genes of circoviruses. A connection between the presence of the virus and clinical manifestations of the infection could not be proved.

Detection of porcine circovirus in rodents — Short communication

Porcine circoviruses (PCV) are present worldwide, infecting domestic pigs and wild boars alike. Studies under laboratory conditions indicated that PCV can be taken up by mice and the virus can replicate in these animals. The possible role of rodents in maintaining and transmitting PCV2 infection in the field has not been investigated yet. The present study reports the detection of PCV2, the pathogenic form of the virus, in mice and rats. A number of rodents, such as mice, rats and voles, were collected at PCV2-infected farms and also outside pig herds and tested for the presence of the virus by polymerase chain reaction (PCR). The results indicated that PCV2 can be present both in mice and rats (65.0% and 23.8% positivity, respectively) on the infected premises, but those rodents that were collected outside pig farms remained negative for PCV2.

Distribution and genetic diversity of porcine hokovirus in wild boars

Porcine hokovirus (PHoV), a newly discovered member of the family Parvoviridae and the proposed genus Hokovirus, is considered phylogenetically distinct from other parvoviruses. Here, we report a comprehensive spatio-temporal study of PHoV infection in Romanian wild boars. The prevalence of PHoV differed significantly in samples from 2006/2007 (22.76%) and 2010/2011 (50.54%), and also increased with age. Sequence analysis of PHoVs from 2006/2007 showed a close relationship to PHoVs from pigs from England and wild boars from Germany, while the PHoVs from 2010/2011 were mostly similar to isolates from Hong Kong. The most variable regions were detected in the NS1 gene and proved to be suitable for analysis of the genetic diversity of the virus. It was observed that PHoVs from older wild boar samples differed from those collected recently. These results suggested that porcine hokovirus could be a newly emerging virus of both domestic and wild pigs with yet unknown implications.

Detection of natural inter- and intra-genotype recombination events revealed by cap gene analysis and decreasing prevalence of PCV2 in wild boars.

Porcine circovirus type 2 (PCV2), the causative agent of a number of PCVAD (porcine circovirus associated diseases), is ubiquitous in domestic pig and wild boar populations. In the present study, using recombination detection program, phylogenetic analysis and base-by-base comparison of 28 PCV2 ORF2s (capsid protein coding gene) from wild boars and 8 from domestic pigs of Transylvania, recent natural intra- (PCV2b-1B/PCV2b-1C) and inter-genotype (PCV2a-2D/PCV2b-1C) recombination events were detected. Notably, one potential recombinant (F1-21) was detected in domestic pig with possible parental strains of wild boar origin. The estimated recombinant breakpoints comprised epitopes A, B and C of ORF2, without major changes in amino acid sequences. The prevalence of PCV2 in the wild boar population during the 5-year period following the first outbreaks of postweaning multisystemic wasting syndrome (PMWS) in domestic pigs in Romania showed a decrease from 13.4% to 8.3%. To our knowledge, this is the first study to show the existence of ORF2-based intra- and inter-genotype recombination in wild boar populations and the possible recombination between PCV2 strains of wild boars and domestic pigs. Our results suggest a certain independence of PCV2 infection in wild boar populations and demonstrate the possibility of infection with multiple PCV2 genotypes under natural circumstances. On the other hand, PCV2 genotypes specific for wild boars could be detected in domestic pig at lower frequency suggesting the possible spread of wild boar PCV2 to domestic swine. The recombination events described here may contribute to the genetic diversity of PCV2 and may also be the source of emergence of new PCV2 strains.

Replication and transmission of porcine circovirus type 2 in mice.

Little information is known about infection, replication and transmission of porcine circovirus type 2 (PCV2) in species other than swine. Two sets of animal experiments were carried out to investigate the susceptibility of mice to PCV2 and to study their possible role in maintaining and transmitting the virus. In the first experiment 14 mice were inoculated with PCV2 by the intraperitoneal route with 5 x 10(2) TCID50 of the PCV2-ROM strain (Cadar et al., 2007). In a second experiment 24 mice were divided into two groups (A and B); mice in Group A (n = 18) were inoculated orally with 1 x 10(5) TCID50 PCV2-ROM and mice in Group B (n = 6) were left uninoculated until day 12 post inoculation (p.i.), when they were mixed with Group A. The animals were sacrificed at intervals for postmortem investigation and virus genome detection by polymerase chain reaction (PCR). The PCR results indicated that PCV2 could replicate in mice infected intraperitoneally or by the oral route, and that the virus can be transmitted directly from mouse to mouse.

Novel circovirus in European catfish (Silurus glanis)

Circular single-stranded DNA viral genomes had been identified worldwide in different species and in environmental samples. Among them, viruses belonging to the genus Circovirus of the family Circoviridae are present in birds and pigs, and recently, they were detected in barbels. The present study reports the identification of a new circovirus in fish. PCR amplification and sequencing were used to identify the novel circular DNA virus in European catfish (Silurus glanis). Full genome characterization and phylogenetic analysis showed that the virus belonged to the family Circoviridae and that it was distantly related to the previously described barbel circovirus.

Genetic diversity of pigeon circovirus in Hungary

Pigeon circoviruses (PiCV) had been identified worldwide and are responsible for immune suppression and a variety of diseases collectively referred to as young pigeon disease syndrome. Samples from racing pigeons were collected throughout Hungary and analyzed for the presence of PiCV by polymerase chain reaction. The capsid protein coding gene was amplified from ten PiCVs of different origins, and compared with known PiCV sequences. The results indicated that PiCV was highly variable, the viruses formed five distinct genetic groups. Differences of the 3′ end of the gene suggested the possibility of genetic recombination among these groups.

Phylogeny and evolutionary genetics of porcine parvovirus in wild boars

Porcine parvovirus (PPV) is widespread among swine and is responsible for reproductive failure of susceptible sows, characterized by embryonic and fetal death. Studies showed that PPV in domestic pig is genetically diverse and some strains differ from the ones used for vaccination. Organ samples from wild boars and domestic pigs were collected in Transylvania (Romania) and tested for the presence of PPV by polymerase chain reaction. Positive samples were grouped and 14 from the wild boar and 1 from the domestic pig PPVs were selected for VP1/VP2 sequence analysis and comparison with available GenBank data. The molecular clock analysis revealed that PPV has a relatively recent evolutionary history, originated approximately 120 years ago and the main divergence occurred in the last 20-60 years. Phylogenetic and residue substitution analysis showed that the viruses could be divided into 6 distinct clusters and that wild boar PPVs were partially different and independent from domestic pig PPVs. PPVs of wild boars proved to be more diverse than viruses of domestic pigs. The presence of the highly virulent 27a-like PPV strains in wild boars was also detected.