Phylogenetic analysis of classical swine fever virus (CSFV) field isolates from outbreaks in South and Central America

To date, there is little information concerning the epidemiological situation of classical swine fever (CSF) in the Americas. Besides summarizing the available data, genotyping of isolates from outbreaks in domestic pigs in several countries of South and Central America was performed. For this, a 190 base fragment of the E2 envelope glycoprotein gene was used. European strains and isolates, and historical isolates from the United States (US) were included for comparison. In contrast to the situation in most parts of Europe, where group 2 isolates predominate, it was found that all the isolates from the American continent analyzed belonged to group 1 and were further resolved into three subgroups. The Cuban isolates clustered in subgroup 1.2, whereas the isolates from Honduras and Guatemala clustered in subgroup 1.3. The remaining isolates from Argentina, Brazil, Colombia and Mexico generated four poorly resolved clusters in subgroup 1.1, together with the vaccine strains, with historical European and US isolates, and with a recent Russian isolate. While the vaccine strains and the historical European isolates formed a relatively distinct cluster, one of the US isolates clustered together with the Mexican, and another one with Colombian isolates. Historically, CSF (hog cholera) was observed almost simultaneously in the US and in Europe in the first half of the 19th century, and its origin remains a matter of discussion. Our results showed that the US isolates are closely related to isolates from South America, while appearance of isolates in Cuba on one hand and in Honduras and Guatemala on the other hand, seems to have been due to unrelated events. This allows to speculate that at least in the American continent, CSF virus may have appeared independently in several regions, and spreading may have been a secondary effect.

[Analysis of bulk milk samples using polymerase chain reaction: an additional tool for bovine viral diarrhea monitoring]

Programmes for the eradication and control of infections with bovine viral diarrhea virus (BVDV) concentrate on the identification and elimination of persistently infected (PI) animals. The identification of these animals is mainly based on the detection of viral antigen using ELISA techniques. Protocols detecting viral nucleic acid using RT-PCR have been described recently. Due to high costs the German model recommends screening of animals of 9 up to 36 months of age. Screening of bulk milk samples using RT-PCR technology would allow a system independent of age. The aim of the present study was to test whether bulk milk samples (1433 including max. 50 animals each) collected in four counties of Lower Saxony are suitable for a complementary identification of PI animals via RT-PCR. Thirty-one bulk milk samples derived from 27 dairy herds were BVDV positive, corresponding to 2.3 % of the herds analysed in this study. Two samples first scored doubtful. Follow up tests revealed lactating PI animals in most cases (18). In other cases the epidemiological status of the herd, i.e. high sero-prevalence and/or presence of PI animals among non-lactating cattle, suggested a transient infection detected in the first bulk milk sample. These results demonstrate that monitoring of lactating cattle of any age using RT-PCR is a very sensitive, economically effective additional method for the identification of PI animals.

Bovine viral diarrhoea virus is internalized by clathrin-dependent receptor-mediated endocytosis

Bovine viral diarrhoea virus (BVDV) is a pestivirus within the family Flaviviridae. In contrast to the members of the genus flavivirus, nothing is known about the viral entry route for pestiviruses. In this study, the process of BVDV infection following attachment to the cell surface was examined. BVDV clearly co-localizes with clathrin, with early endosome antigen-1 (EEA-1), an early endosome marker, and also with lysosomal-associated membrane protein-2 (LAMP-2), a lysosomal marker. BVDV internalization is inhibited by compounds that block clathrin- but not caveolae-dependent endocytosis. These findings demonstrate that BVDV enters the cells via the clathrin-coated pit pathway.

Genetic diversity of international bovine viral diarrhoea virus (BVDV) isolates: identification of a new BVDV-1 genetic group

In the last decade, several studies were performed to characterise bovine viral diarrhoea virus (BVDV) isolates and define genetic groups by genotyping. Much data is now available from GenBank, predominantly sequences from the 5' untranslated region (5'-UTR). In order to find out whether genetic grouping of isolates from different countries could be harmonised, 22 new isolates from five countries were analysed in combination with published sequences. Eighteen of these isolates were typed as BVDV genotype 1 (BVDV-1), and one isolate from Argentina and three isolates from Brazil were typed as BVDV-2. BVDV-1 isolates were clustered into five previously defined genetic groups: BVDV-1a, b, d, e and f. Two isolates from Finland and one from Egypt formed a group which was tentatively labelled as BVDV-1j, since statistical support was low. By using a fragment of the Npro gene for typing, we found that these isolates fall into the same group as a deer strain, and are statistically significant. Some Swiss BVDV strains taken from GenBank were found in a new genetic group which was designated as BVDV-1k. The BVDV-2 isolates included in this study seemed to fall into two genetic groups.

Phylogenetic analysis of the E2 gene of classical swine fever viruses from Lao PDR

The E2 genes of 21 classical swine fever viruses (CSFV) were genetically characterized and compared with reference CSF viruses. The viruses originated from CSF outbreaks that occurred in the Lao People's Democratic Republic (Lao PDR) during 1997 though to 1999. All viruses characterized belonged to genogroup 2 and were members of subgroups 2.1 and 2.2. Results demonstrated a geographic delineation between subgroups 2.1 that was only found in the North-Central region, and subgroup 2.2 that was mostly found in the South-Central regions of Lao PDR. Although it was not possible to determine the origin of these viruses, it is probable that they may have been introduced to Lao PDR following cross-border trade. Alternatively, they have evolved independently of other viruses in the region.

The surface glycoprotein E2 of bovine viral diarrhoea virus contains an intracellular localization signal

The intracellular transport of the surface glycoprotein E2 of bovine viral diarrhoea virus was analysed by expressing the cloned gene in the absence of other viral proteins. Immunofluorescence analysis and surface biotinylation indicated that E2 is located in an early compartment of the secretory pathway and not transported to the cell surface. In agreement with this result, E2 was found to contain only high-mannose oligosaccharide side-chains but no N-glycans of the complex type. To define the intracellular localization signal of the E2 protein, chimeric proteins were generated. E2 chimeras containing the MT (membrane anchor plus carboxy-terminal domain) of the G protein of vesicular stomatitis virus (VSV) or of the F protein of bovine respiratory syncytial virus (BRSV) were transported to the cell surface. On the other hand, VSV G protein containing the MT domain of E2 was detected only in the ER, indicating that this domain contains an ER localization signal. A chimeric E2 protein, in which not the membrane anchor but only the carboxy-terminal end was replaced by the corresponding domain of the BRSV F protein, was also localized in the ER. Therefore, it was concluded that the membrane anchor contains the ER localization signal of E2. Interestingly, the ER export signal within the VSV G protein cytoplasmic tail was found to overrule the ER localization signal in the E2 protein membrane anchor.

Phocine distemper in German seals, 2002

Approximately 21,700 seals died during a morbillivirus epidemic in northwestern Europe in 2002. Phocine distemper virus 1 was isolated from seals in German waters. The sequence of the P gene showed 97% identity with the Dutch virus isolated in 1988. There was 100% identity with the Dutch isolate from 2002 and a single nucleotide mismatch with the Danish isolate.

Genetic typing of recent classical swine fever virus isolates from Croatia

During a period of 5 years (1997-2001) several outbreaks of classical swine fever (CSF) were recorded in Croatia. For genetic typing, fragments of 150 nucleotides within the 5'-non-translated region (5'-NTR) and 190 nucleotides within the E2 glycoprotein coding gene of nine field isolates that were derived from domestic pigs and wild boars were used. For better epizootiological understanding, isolates from other European countries were included in the study. The results show that the isolates belong to subgroups 2.1 and 2.3 of CSF virus. Isolates from subgroup 2.1 were collected from domestic pigs during sporadic outbreaks in June 1997 and are genetically closely related. A genomic similarity between these isolates and CSF virus isolates from pigs in other European countries from the same year could also be confirmed. In contrast, the isolate from October 1997 was found to be a member of subgroup 2.3, and is closely related to European CSF virus isolates from outbreaks in the last decade in Western and Central European countries. These results show that two different sources of CSF virus caused outbreaks in Croatia during the same year. Furthermore, a close relationship was found between an isolate from a domestic pig in 1999 and isolates of subgroup 2.3 that originated from Croatian wild boars.

No caspase activation but overexpression of Bcl-2 in bovine cells infected with noncytopathic bovine virus diarrhoea virus

Cytopathic bovine viral diarrhoea viruses (cp BVDV) induce apoptosis in permissible cell cultures via the intrinsic pathway, which involves the mitochondria as key organelles. An important event is the irreversible opening of the permeability transition pore (PTP) and the breakdown of the transmembrane potential DeltaPsi(m). The resulting release of cytochrome C from the mitochondria serves as a trigger to form the apoptosome which then leads to caspase activation and cell death. In contrast, noncytopathic (ncp) BVDV do not seem to affect cells in vivo or in vitro, suggesting that they inhibit apoptosis. Interestingly, inhibition of caspases in cells infected with cp BVDV delayed the apoptotic cascade but did not prevent the cytopathic effect (CPE). This suggests that the induction of apoptosis and the processes finally leading to the CPE may proceed separately, implying that the inhibition of apoptosis by ncp BVDV has to start earlier in the cascade. In this study we show that in fact apoptosis inhibition in cells infected with ncp BVDV must occur at the mitochondrial level, before the activation of the caspase cascade occurs. To elucidate the role of mitochondria after infection of cells with ncp BVDV, expression of Bcl-2 and Bax were analysed. It was shown that while Bax expression was not affected, the anti-apoptotic Bcl-2 protein was upregulated, presumably suppressing initiation of cell death and enabling persistent infection in vitro.

Molecular epidemiology of classical swine fever in the Russian Federation

The ability to discriminate between various classical swine fever virus (CSFV) strains and isolates is a prerequisite for following the spread of the virus after an outbreak. To determine the relatedness between Russian CSFV isolates from different geographical regions, three fragments of the viral genome (5' NTR, the variable region of the E2 gene and a fragment of the NS5B gene) were sequenced and used for genetic typing. Thirty-one field isolates were obtained from CSF outbreaks which occurred between 1994 and 1999. In addition, three attenuated strains were included in the study, namely the LK and CS vaccine strains, and the moderately virulent 238H isolate. The vaccine strains have been used in Russia for more than 30 years. Our results showed that all field isolates are in subgroup 1.1 together with Alfort 187 and with the highly virulent strain Shimen. In contrast, the CS and LK vaccine strains belong to subgroup 1.2. While there is no evidence for the reversion of the two vaccine strains to wild type, it is feasible that the highly virulent Shimen strain, which has been used as a challenge strain for many years, contributed to field strain generation. The Russian field isolates from the 1990s can be distinguished from the CSF virus isolates which occurred in the EU Member States in the same decade, as here all outbreaks were caused by CSF viruses belonging to subgroup 2.

Classical swine fever--an update

Classical swine fever (CSF) is a serious and contagious viral disease of pigs and wild boar with a widespread worldwide distribution. The immunopathology of the disease is poorly understood, but the ability of the CSF virus to infect cells without triggering apoptosis and to kill uninfected cells is probably highly significant. The virus may be spread by various direct and indirect methods, but in most cases the exact mechanisms involved in local spread between farms are not known. Excellent diagnostic tools and typing methods are available, but tests that could be performed on-farm, in pre-clinically infected pigs or on meat would also be advantageous. A more complete picture of the viruses circulating in different parts of the world is needed. There is great interest to develop and use marker vaccines for the control of CSF in domestic pigs and in wild boar. Epidemiological modelling is increasingly used to evaluate control options.

Characterization of the horse ( Equus caballus ) IGHA gene

Nucleotide sequences of the immunoglobulin constant heavy chain genes of the horse have been described for IGHM, IGHG and IGHE genes, but not for IGHA. Here, we provide the nucleotide sequence of the genomic IGHA gene of the horse ( Equus caballus), including its secretion region and the transmembrane exon. The equine IGHA gene shows the typical structure of a mammalian IGHA gene, with only three exons, separated by two introns of similar size. The hinge exon is located at the 5' end of the CH2 exon and encodes a hinge region of 11 amino acids, which contains five proline residues. The coding nucleotide sequence of the secreted form of the equine IGHA gene shares around 72% identity with the human IGHA1 and IGHA2 genes, as well as the bovine, ovine, porcine and canine IGHA genes, without distinct preference for any of these species. The same species also cluster together in a phylogenetic tree of the IGHA coding regions of various mammals, whereas rodent, rabbit, marsupial and monotreme IGHA genes each build a separate cluster.

Bovine viral diarrhoea eradication and control programmes in Europe

The economic impact of BVDV infections has led a number of countries in Europe to start eradication or control programmes. While in both cases the primary step is identification and elimination of persistently infected (PI) animals, the strategy applied thereafter is dependent on the density and seroprevalence of the regional cattle population. One of the first countries to design and implement an eradication programme was Sweden in 1993, a country with a relatively low cattle density and no vaccination. For screening, an indirect antibody ELISA for serum, milk and bulk milk samples is being used. The basics of the Swedish model are no vaccination, voluntary participation, and financing of the entire scheme by the subscribing farmers. BVDV-free herds are certified and permanently checked. While in 1993 only about 35% of the herds were seronegative, about 87% were BVDV-free in 2001. The aim of control programmes in high density areas with high seroprevalence is to minimize economic losses by reducing the incidence of PI animals and thereby virus circulation (German model). Participation is voluntary, and parts of the costs are carried by the public animal insurance (Tierseuchenkasse). Screening is performed using an antigen capture ELISA with blood or serum. In Lower Saxony, for example, a herd is declared BVDV unsuspicious if all animals up to 36 months are BVDV antigen negative and the female offspring older than six months is vaccinated twice (an inactivated vaccine is used for basic immunization, and an attenuated live virus vaccine for boosting).

[Perspectives on BVD eradication in Germany]

Infections with the bovine virus diarrhoea (BVD) virus are endemic with high seroprevalence in many countries of the European Union (EU). The significant economic damage caused by BVD infections has led to a paradigm shift with respect to a possible control. In some EU Member States control programmes have been initiated mostly on a voluntary basis and some compulsory. The most important element of all control efforts is the identification and removal of persistently infected (PI) animals. The subsequent steps depend on the respective seroprevalence and cattle density. Sweden was one of the first countries to introduce a national control program (1993), that is now being used as standard procedure in other countries. The starting position for the program was comparatively favorable since the country's cattle density is low and vaccination was not allowed. BVD infected herds were screened using a bulk milk ELISA and subsequently the PI animals in positive herds were identified and removed. The goal of the control program is the cattle population's certified freedom of BVD. The Scandinavian model is not applicable for most regions of Germany, since BVD virus prevalence and cattle density are unfavorably high. Here the primary goal is to minimize the economic losses caused by BVD and to lower the infective pressure. Therefore a Federal guideline was issued and some Federal States have provided additional regulations for compensation of PI animals and additional costs, respectively. Primary goal of the guideline is the eradication of PI animals and the systematic vaccination of all female offspring in order to avoid further economic damage and the emergence of new PI animals in case of re-infection of the herd. Goal of this strategy is the BVD unsuspicious herd with a high immune status.

[BVD diagnosis: an overview]

The first step and a crucial condition for the success of a control or eradication program for BVD (bovine viral diarrhea) is the identification and elimination of animals persistently infected with the virus. For this, besides detailed knowledge of the epidemiology, efficient diagnostic tests are necessary. This review summarizes the presently available diagnostic tests for detection of antibodies against the virus or for detection of viral components. Their performance and their applicability in eradication programs is discussed.

Genetic diversity of recent bovine viral diarrhoea viruses from the southeast of Austria (Styria)

To characterise the bovine virus diarrhoea virus (BVDV) isolates circulating in the southeastern region of Austria, namely in the province of Styria, 71 blood samples collected between 1998 and 2000 from persistently infected cattle in 62 herds were subjected to genetic typing. For this, 288bp fragments from the 5' untranslated region (5'-UTR) were amplified by polymerase chain reaction after reverse transcription (RT-PCR). The products were sequenced and used for phylogenetic analysis. Seventy virus isolates were typed as BVDV species 1 (BVDV-1). Only one isolate was typed as BVDV species 2 (BVDV-2), representing the first isolate of this pestivirus genotype found in Austria. In addition, phylogenetic analysis revealed that viruses belonging to five genetic groups within BVDV-1 are circulating in Styria. Most viruses (53) were found in group BVDV-1f, nine viruses in BVDV-1h, four viruses in BVDV-1b, three viruses in BVDV-1d and one virus in BVDV-1g. No virus was found in genetic group BVDV-1a, which is dominant in the UK and widely distributed in USA. Likewise, the BVDV isolates predominating in a neighbouring country, namely Germany, belonged to different genogroups than those circulating in Styria. We conclude that in a particular region and environment certain BVDV-1 genetic groups predominate. New groups, including BVDV-2, can be introduced, e.g. by trade of animals. The low incidence of BVDV-2 in Styria is in concert with the sporadic occurrence of these viruses in other regions of Europe.

Clinical signs and epidemiology of classical swine fever: a review of new knowledge

Although classical swine fever (CSF) has been well known for decades and epidemics still occur, clinical diagnosis continues to cause problems for veterinary practitioners. This is due to the extensive differential diagnosis, further complicated by the emergence of new diseases such as porcine reproductive and respiratory syndrome (PRRS) and porcine dermatitis and nephropathy syndrome (PDNS). In addition, acute, chronic and prenatal courses of CSF have to be distinguished. As a cause of considerable economical losses within the EU, control of CSF requires knowledge of the primary outbreaks and spread of the disease. Genetic typing of CSF virus isolates has proved to be a potent method of supporting epidemiological investigations. Phylogenetic analysis of CSF virus strains and isolates originating from different continents has allowed three genetic groups and several subgroups within these groups to be distinguished. Whereas isolates belonging to group 3 seem to occur solely in Asia, all CSF virus isolates of the 1990s isolated in the EU belonged to one of the subgroups within group 2 (2.1, 2.2, or 2.3) and were clearly distinct from former CSF reference viruses, which belong to group 1. Within the EU, different strategies are followed for the eradication of CSF in domestic pigs and in wild boar. While a strict non-vaccination policy is followed for domestic pigs, eradication of the disease in wild boar is more complex, and oral immunisation together with special hunting strategies have been applied. Recently, marker vaccines with a companion discriminatory test designed to allow differentiation between vaccinated animals and animals having recovered from field virus infection have been developed. Preliminary studies indicated that the discriminatory tests had a reduced sensitivity and specificity. Further improvements are therefore necessary before marker vaccines can be considered for emergency use in EU Member States. Prevention of CSF remains the main objective within the EU.

Induction of the intrinsic apoptotic pathway in cells infected with cytopathic bovine virus diarrhoea virus

Cytopathic bovine viral diarrhoea virus (cp BVDV) induces apoptosis in bovine cell cultures. This also seems to be a prominent feature in the pathogenesis of mucosal disease. To gain an insight into the molecular pathways of the cell alterations, the involvement of different members of the apoptotic cascade was analyzed. It was shown that inhibition of the mitochondrial permeability transition pore significantly delayed the cytopathic effect without affecting virus replication. Moreover, the membrane potential (deltapsi(m)) was affected, and translocation of cytochrome c to the cytosol, overexpression of apoptotic protease-activating factor 1 and a significant increase of caspase-9 activity were demonstrated, indicating that the apoptosome is formed. We conclude that at least in vitro, infection of cells with cp BVDV leads to the activation of the intrinsic pathway of apoptosis.

Apoptosis inhibitors delay the cytopathic effect of bovine viral diarrhoea virus (BVDV)

Based on their action in cell culture, two biotypes of bovine viral diarrhoea virus (BVDV) can be distinguished. The noncytopathic (ncp) BVDV isolated from persistently infected animals cause no visible damage to cultured bovine cells. In contrast, cytopathic (cp) BVDV induces severe damage and apoptosis in cell cultures. Cp BVDV can be isolated from cattle suffering from mucosal disease (MD) and is associated with the severe lesions that primarily affect the gastrointestinal tract. To get an insight into the molecular events during BVDV induced cytopathic effect (CPE), the effect of three chemical reagents (3-aminobenzamide, ascorbic acid and N-acetyl-leucyl-leucyl-methional) with completely different mode of actions in infected cells was analysed. All three substances were able to delay the cytopathic effect induced in permissive bovine cells.

Evolution of the six horse IGHG genes and corresponding immunoglobulin gamma heavy chains

It is generally assumed that the different mammalian IgG isotypes have developed during evolution by duplications of a common ancestor gamma heavy chain constant region gene (IGHG). In contrast to other species studied so far, which express between one and four IGHG genes, the horse (Equus caballus) genome contains six IGHG genes, and it has been postulated that they all can be expressed. For determination of the evolutionary history of the six horse IGHG genes, genomic DNA and cDNA of the IGHG genes were sequenced. The structure of these genes with reference to exons and introns was determined. Comparison of the deduced amino acid sequences of the horse IGHG genes revealed the greatest divergences in the hinge regions, and in the proximal CH2 domains. A phylogenetic comparison of the amino acid sequences of the six horse IGHG genes to those of other species shows that the horse IGHG genes form a distinct cluster. This indicates that the mammalian species included in this study probably share only one common ancestor IGHG gene with the horse. The six horse IGHG genes probably then evolved by gene duplication after species separation. In addition, various segmental exchanges were found between the horse IGHG genes, which might be the result of unequal crossing over and/or gene conversion events during the evolution of the six horse IGHG genes.

Molecular epidemiology of classical swine fever in Italy

To gain an insight into the molecular epidemiology of classical swine fever (CSF) in Italy, virus isolates originating from outbreaks that occurred between 1985 and 2000 in wild boar or in domestic pigs in mainland Italy and in Sardinia were analysed by genetic typing. For this, a fragment (190 nucleotides) of the E2 glycoprotein gene was sequenced and phylogenetic analyses were performed, including older Italian isolates and isolates from recent outbreaks in Europe for comparison. The results show that in mainland Italy, several independent epidemiological events occurred in the last decade. In the north of the country, viruses of genotype 2.2 have persisted in wild boar, causing sporadic outbreaks in domestic pigs. In contrast, viruses of subgroups 2.1 and 2.3 appeared only intermittently in different regions of the mainland. In 1997, classical swine fever virus (CSFV) isolates belonging to the subgroup 2.1 and genetically and epidemiologically related to the Dutch isolate in Venhorst, affected domestic pigs exclusively. The isolates of subgroup 2.3, derived from wild boar as well as from domestic pigs were closely related to isolates from Germany and Poland. In Sardinia, CSF is an endemic in wild boar and affects domestic pigs also. Genetic typing showed that viruses of subgroups 1.1 and 2.3 have been present, the last ones being unrelated to the mainland viruses of the same subgroup. Due to the large quantities of pig and wild boar meat imported in some parts of Italy, it cannot be established if these viruses were always present in either the mainland or Sardinia, or if they represent recent introductions.

Comparison of different methods for the isolation of Burkholderia cepacia DNA from pure cultures and waste water

DNA from Burkholderia cepacia was prepared from suspensions of pure cultures and artificially contaminated waste water. The efficacy of four standard methods (lysis buffer containing proteinase K, phenol/chloroform/isoamylalcohol extraction, microwave treatment, heat treatment) and six commercially available kits (Puregene, High Pure PCR Template Preparation Kit, InstaGene, QIAamp Tissue Kit, DNAzol, Elu-Quik) was compared in terms of sensitivity in a subsequent PCR. The results showed that a simple and inexpensive procedure using a lysis buffer containing proteinase K was superior to all other methods tested.

Localization of viral proteins in cells infected with bovine viral diarrhoea virus

Bovine viral diarrhoea virus (BVDV) is a member of the genus Pestivirus within the family Flaviviridae. In this report, protein localization studies were performed to assess the mechanism for the release of mature virus particles from infected cells. Since BVDV is an enveloped virus, budding from either intra- or extracellular membranes is feasible. A prerequisite for the latter mechanism is the integration of viral glycoproteins into the host cell membrane. Using monoclonal antibodies (MAbs) directed against the viral envelope glycoproteins E2 and E(RNS), no specific signals were detected on the surface of BVDV-infected cells by indirect fluorescence, confocal microscopy or fluorescence-activated cell sorter analyses. Furthermore, biotin-labelled cell surface proteins of virus-infected and non-infected cells were not detected by immunoprecipitation using MAbs directed against E(RNS) and E2 or the non-structural protein NS2-3. None of these proteins was detected on the cell surface. In addition, to analyse the intracellular localization of the two viral glycoproteins E(RNS) and E2 and the non-structural proteins NS2-3 and NS3, subcellular fractionation of virus-infected cells followed by radioimmunoprecipitation with the MAbs were performed. These results led to the conclusion that the BVDV envelope glycoproteins E(RNS) and E2 as well as the non-structural proteins NS2-3 and NS3 were almost quantitatively associated with intracellular membranes. These findings indicate that BVDV is released by budding into the cisternae of the endoplasmic reticulum and that there seems to be no correlation between the location and function of the analysed proteins.

Prevalence of genotypes 1 and 2 of bovine viral diarrhea virus in Lower Saxony, Germany

The aim of this study was to find whether an antigenic drift had occurred in Lower Saxony in the past 40 years. For this, the genetic diversity of bovine viral diarrhea virus (BVDV) isolates mainly from Lower Saxony was estimated by RT-PCR and sequencing of a 420 bp fragment of the E2 glycoprotein gene. Sixty-one field virus isolates collected during routine diagnostics between 1960 and 2000 in Lower Saxony, Northern Germany, were analyzed. Phylogenetic analysis allowed discrimination of genotypes BVDV 1 and 2. Excepting two isolates, which were of BVDV type 2, most of the isolates were classified as BVDV type 1. This group could be further subdivided into four subgroups and one disparate isolate. Independent of the year of isolation and geographical localization, 54 isolates clustered in two subtypes (BVDV subtypes 1b and 1d). Only one isolate was classified as BVDV type 1a, thus being similar to the North American NADL strain, and to the vaccine strain Oregon C24V, which was extensively used for vaccination in Germany. The remaining isolates belonged to new clusters tentatively designated as BVDV subtypes 1g and 1f. To compare the cluster designation with that of other studies, phylogenetic analysis of representatives of each of the subgroups based on the 5' untranslated region (5'UTR) was performed. It grouped the viruses similarly. The results indicate that the BVDV population seems to be relatively stable over 40 years in Lower Saxony.

[Genetic typing of German isolates of classical swine fever virus]

During the last decade several outbreaks of classical swine fever (CSF) occurred in Germany in domestic pigs and in wild boar, respectively. Two major epidemics which also affected other EU Member States were recorded. To support epidemiological investigations genetic typing was applied and virus isolates originating from different outbreaks in Germany were assigned to groups and virus types. Two genomic regions were selected for the phylogenetic analysis, namely 150 nucleotides from the 5' non-translated region (5'-NTR) and 190 nucleotides from the E2 glycoprotein gene. All German CSF virus isolates of the nineties (Group 2) were distinct from former reference strains (Group 1). Within Group 2 both genomic regions allowed to distinguish three subgroups, namely 2.1, 2.2 and 2.3. Within subgroup 2.3 five virus types could be discriminated using the 5'-NTR sequences. These are 2.3*Uelzen and 2.3*Spreda, mainly with isolates from Lower Saxony, as well as 2.3*Rostock, 2.3*Güstrow and 2.3*Spante, mainly with isolates from Eastern Germany. Analysis of the E2 gene fragment allowed a better discrimination between single isolates, but only two virus types could be defined: 2.3*MV/BB, comprising the isolates from Eastern Germany, and 2.3*NI, with the isolates from Lower Saxony. Genetic typing allowed to discriminate between isolates involved in different CSF epidemics, and was useful for tracing the origin and spread of CSF viruses. Due to the close relationship between German CSF virus isolates, epidemiological data are a prerequisite for the interpretation of the results obtained by genetic typing. In addition, at least both genomic regions suggested here should be analysed to determine the identity of a new isolate.