The role of national and international veterinary laboratories

In the field of diagnostic test validation, World Organisation for Animal Health (OIE) Reference Laboratories (RLs) have a pivotal role and provide the international community with impartial advice and support in the selection, development and validation of diagnostic tests, which can be applied to the specialist diseases for which they are designated. National RLs provide an invaluable function in supporting the introduction, ongoing validation and application of validated diagnostic tests in line with international standards. Experienced staff with extensive knowledge of such systems and access to specialist facilities for conducting work are available to monitor changes or advancements in technology. They consider their relevance and value to evolving diagnostic test requirements. Reference Laboratories often have a broad mandate of activity linking research or development programmes and surveillance activities to benefit the continual assessment and, if necessary, improvement of diagnostic tools. Reference Laboratories maintain or have access to unique biological archives (known positive and negative sample populations) and produce international reference standards, both of which are vital in establishing the necessary and detailed validation of any diagnostic test. Reference Laboratories act either singularly or in collaborative partnerships with other RLs or science institutes, but also, when required, and with impartiality, with the commercial sector, to ensure new tests are validated according to OIE standards. They promote and apply formal programmes of quality assurance (including proficiency testing programmes) for newly validated tests, ensuring ongoing monitoring and compliance with standards, or as required set out any limitations or uncertainties. Reference Laboratories publish information on test validation in the scientific literature and on relevant websites, as well as disseminating information at workshops and international conferences. Furthermore, they can offer training in the processes and systems underpinning test validation.

Introduction History of rabies control by vaccination

Since antiquity, rabies has remained one of the deadliest infectious diseases known to humankind, with a case fatality rate approaching 100% following the onset of clinical disease. It is present on all continents where terrestrial mammals exist, with the majority of animal and human cases being reported in the resourcelimited countries of Africa and Asia, with thousands of human rabies deaths being recorded annually. It is likely, however, that the global figure of approximately 59,000 annual human rabies fatalities is an underestimate. The impact of the disease has been reduced substantially across vast regions of the globe since the development of effective rabies vaccines. The success of different vaccines and vaccination policies in the defined 'at risk' populations has been born out of scientific innovation. Mass vaccination campaigns of animals, using parenteral vaccines to immunise companion animals, and advances in oral vaccines for wildlife, have allowed the elimination of rabies in terrestrial carnivores in several regions worldwide, including Western Europe and much of North America. In addition, human vaccines, largely used for post-exposure treatments, have reduced the burden of rabies in endemic areas.

Molecular epidemiology of bat lyssaviruses in Europe

Bat rabies cases in Europe are principally attributed to two lyssaviruses, namely European bat lyssavirus type 1 (EBLV-1) and European bat lyssavirus type 2 (EBLV-2). Between 1977 and 2011, 961 cases of bat rabies were reported to Rabies Bulletin Europe, with the vast majority (>97%) being attributed to EBLV-1. There have been 25 suspected cases of EBLV-2, of which 22 have been confirmed. In addition, two single isolations of unique lyssaviruses from European insectivorous bats were reported in south-west Russia in 2002 (West Caucasian bat virus) and in Germany in 2010 (Bokeloh bat lyssavirus). In this review, we present phylogenetic analyses of the EBLV-1 and EBLV-2 using partial nucleoprotein (N) gene sequences. In particular, we have analysed all EBLV-2 cases for which viral sequences (N gene, 400 nucleotides) are available (n = 21). Oropharyngeal swabs collected from two healthy Myotis daubentonii during active surveillance programmes in Scotland and Switzerland also yielded viral RNA (EBLV-2). Despite the relatively low number of EBLV-2 cases, a surprisingly large amount of anomalous data has been published in the scientific literature and Genbank, which we have collated and clarified. For both viruses, geographical relationships are clearly defined on the phylogenetic analysis. Whilst there is no clear chronological clustering for either virus, there is some evidence for host specific relationships, particularly for EBLV-1 where more host variation has been observed. Further genomic regions must be studied, in particular for EBLV-1 isolates from Spain and the EBLV-2 isolates to provide support for the existence of sublineages.

Molecular diversity and evolutionary history of rabies virus strains circulating in the Balkans

Molecular studies of European classical rabies viruses (RABV) have revealed a number of geographically clustered lineages. To study the diversity of Balkan RABV, partial nucleoprotein (N) gene sequences were analysed from a unique panel of isolates (n = 210), collected from various hosts between 1972 and 2006. All of the Balkan isolates grouped within the European/Middle East Lineage, with the majority most closely related to East European strains. A number of RABV from Bosnia & Herzegovina and Montenegro, collected between 1986 and 2006, grouped with the West European strains, believed to be responsible for the rabies epizootic that spread throughout Europe in the latter half of the 20th Century. In contrast, no Serbian RABV belonged to this sublineage. However, a distinct group of Serbian fox RABV provided further evidence for the southwards wildlife-mediated movement of rabies from Hungary, Romania and Serbia into Bulgaria. To determine the optimal region for evolutionary analysis, partial, full and concatenated N-gene and glycoprotein (G) gene sequences were compared. Whilst both the divergence times and evolutionary rates were similar irrespective of genomic region, the 95 % highest probability density (HPD) limits were significantly reduced for full N-gene and concatenated NG-gene sequences compared with partial gene sequences. Bayesian coalescent analysis estimated the date of the most common recent ancestor of the Balkan RABV to be 1885 (95 % HPD, 1852-1913), and skyline plots suggested an expansion of the local viral population in 1980-1990, which coincides with the observed emergence of fox rabies in the region.

Phylogenetic analysis of rabies viruses from Sudan provides evidence of a viral clade with a unique molecular signature

Rabies is endemic in Sudan and remains a continual threat to public health as transmission to humans is principally dog-mediated. Additionally, large-scale losses of livestock occur each year causing economic and social dilemmas. In this study, we analysed a cohort of 143 rabies viruses circulating in Sudan collected from 10 different animal species between 1992 and 2006. Partial nucleoprotein sequence data (400 bp) were obtained and compared to available sequence data of African classical rabies virus (RABV) isolates. The Sudanese sequences formed a discrete cluster within the Africa 1a group, including a small number of sequences that clustered with sequences from Ethiopian RABV. These latter sequences share an Aspartic Acid at position 106 (Asp(106)) with all other Africa 1a group members, in contrast to the remaining Sudanese strains, which encode Glutamic Acid at this position (Glu(106)). Furthermore, when representatives of other African and European lineages were aligned, Glu(106) is unique to Sudan, which supports the concept of a single distinct virus strain circulating in Sudan. The high sequence identity in all Sudanese isolates studied, demonstrates the presence of a single rabies virus biotype for which the principal reservoir is the domestic dog.

Molecular epidemiology of lyssaviruses in Eurasia

The Lyssavirus genus, a member of the Rhabdoviridae family, consists of seven established related viruses (genotypes 1-7). Rabies cases in Eurasia are principally attributed to three of these genotypes, namely genotype 1 (RABV, classical rabies) and to a lesser extent genotypes 5 and 6 (European bat lyssaviruses type-1 and -2). In addition, four newly identified divergent lyssaviruses have been isolated from insectivorous bats. The molecular diversity of classical rabies viruses (genotype 1, RABV) has been studied at the global level and reference has been made to the existence of a number of European strains in a range of mammalian species. It is accepted that these viruses cluster within a 'Cosmopolitan Lineage' having ancestral roots in Europe in the 17th century before its widespread dispersal to Asia, Africa and the Americas as a result of European exploration and colonization.

Molecular epidemiology of rabies in bat-eared foxes (Otocyon megalotis) in South Africa

A panel of 124 rabies viruses from wildlife host species (principally the bat-eared fox, Otocyon megalotis) and domestic carnivore species were collected between 1980 and 2005 from a region of South Africa associated with endemic bat-eared fox rabies. We have studied the molecular epidemiology of bat-eared fox rabies by virtue of nucleotide sequence analyses of PCR amplicons specific to the variable G-L intergenic region as well as the conserved nucleoprotein gene of each of the rabies viruses in this South African panel. Although it was demonstrated that all of these viruses were very closely related, they could be segregated into two major phylogenetic groups. The data presented in this paper complement antigenic and surveillance data on rabies in this host species in South Africa. Most importantly our data support a hypothesis that the bat-eared fox independently maintains rabies cycles in specific geographical loci. This is the first molecular epidemiological investigation describing rabies transmission dynamics in this wildlife carnivore host species in South Africa.

Comparative analysis of the full genome sequence of European bat lyssavirus type 1 and type 2 with other lyssaviruses and evidence for a conserved transcription termination and polyadenylation motif in the G-L 3' non-translated region

We report the first full-length genomic sequences for European bat lyssavirus type-1 (EBLV-1) and type-2 (EBLV-2). The EBLV-1 genomic sequence was derived from a virus isolated from a serotine bat in Hamburg, Germany, in 1968 and the EBLV-2 sequence was derived from a virus isolate from a human case of rabies that occurred in Scotland in 2002. A long-distance PCR strategy was used to amplify the open reading frames (ORFs), followed by standard and modified RACE (rapid amplification of cDNA ends) techniques to amplify the 3' and 5' ends. The lengths of each complete viral genome for EBLV-1 and EBLV-2 were 11 966 and 11 930 base pairs, respectively, and follow the standard rhabdovirus genome organization of five viral proteins. Comparison with other lyssavirus sequences demonstrates variation in degrees of homology, with the genomic termini showing a high degree of complementarity. The nucleoprotein was the most conserved, both intra- and intergenotypically, followed by the polymerase (L), matrix and glyco- proteins, with the phosphoprotein being the most variable. In addition, we have shown that the two EBLVs utilize a conserved transcription termination and polyadenylation (TTP) motif, approximately 50 nt upstream of the L gene start codon. All available lyssavirus sequences to date, with the exception of Pasteur virus (PV) and PV-derived isolates, use the second TTP site. This observation may explain differences in pathogenicity between lyssavirus strains, dependent on the length of the untranslated region, which might affect transcriptional activity and RNA stability.

Molecular epidemiological study of Arctic rabies virus isolates from Greenland and comparison with isolates from throughout the Arctic and Baltic regions

We report a molecular epidemiological study of rabies in Arctic countries by comparing a panel of novel Greenland isolates to a larger cohort of viral sequences from both Arctic and Baltic regions. Rabies virus isolates originating from wildlife (Arctic/red foxes, raccoon-dogs and reindeer), from domestic animals (dogs/cats) and from two human cases were investigated. The resulting 400 bp N-gene sequences were compared with isolates representing neighbouring Arctic or Baltic countries from North America, the former Soviet Union and Europe. Phylogenetic analysis demonstrated similarities between sequences from the Arctic and Arctic-like viruses, which were distinct from rabies isolates originating in the Baltic region of Europe, the Steppes in Russia and from North America. The Arctic-like group consist of isolates from India, Pakistan, southeast Siberia and Japan. The Arctic group was differentiated into two lineages, Arctic 1 and Arctic 2, with good bootstrap support. Arctic 1 is mainly comprised of Canadian isolates with a single fox isolate from Maine in the USA. Arctic 2 was further divided into sub-lineages: 2a/2b. Arctic 2a comprises isolates from the Arctic regions of Yakutia in northeast Siberia and Alaska. Arctic 2b isolates represent a biotype, which is dispersed throughout the Arctic region. The broad distribution of rabies in the Arctic regions including Greenland, Canada and Alaska provides evidence for the movement of rabies across borders.

Development of a real-time, differential RT-PCR TaqMan assay for lyssavirus genotypes 1, 5 and 6

A number of RT-PCR methods have been reported for the detection of rabies and rabies-related viruses. Here, a single, closed tube, non-nested RT-PCR TaqMan assay to distinguish between Classical rabies virus and European bat lyssaviruses 1 and 2 in real time is described. The TaqMan assay is rapid, sensitive, specific and allows for the genotyping of unknown isolates concomitant with the RT-PCR. It can be applied quantitatively and the use of an internal control enables the quality of the isolated template to be assessed. The efficiency and dynamic range of the PCR has been established using isolated viral RNA and cloned control template. Comparative performance of the TaqMan assay against other diagnostic methodologies for the detection of rabies virus has been determined and the assay validated against a panel of archival samples and virus of unknown genotype from both Germany and the Sudan. Despite sequence heterogeneity between the different genotypes in the N-gene, a universal forward and reverse primer set have been designed allowing simplification of previously described assays. Rapid genotyping of two recent EBLV2 cases in the U.K. in Daubenton's bats and a recently imported human case of rabies has been performed using this test.

Molecular epidemiology of rabies viruses in Europe

Several different strains of classical rabies virus co-circulate in Europe. In order to investigate the roles of the host species and topography on the molecular epidemiology of these viruses, a 400 bp region of the nucleoprotein gene was sequenced and compared with more than 500 European virus isolates. Viruses from 21 European countries were represented including some unique panels of archived isolates from the former Republic of Yugoslavia, Estonia, the Czech Republic, Poland and Austria. Phylogenetic analysis of 198 unique sequences demonstrated numerous groups of viruses clustered at both geographical and host-species levels.

The diversity of rabies virus in Russia demonstrated by anti-nucleocapsid monoclonal antibody application and limited gene sequencing

A comparative analysis of anti-nucleocapsid monoclonal antibody (N-mAb) reaction profiles and DNA sequences was performed on 97 selected rabies virus (RABV) isolates from Russia and neighbouring states. A panel of 73 N-mAb from the Wistar Institute (Philadelphia, PA, USA), Veterinary Laboratories Agency (Weybridge, UK) and P-41 (Tübingen, Germany) was used. The sequence of a 400 bp fragment of the N gene was generated for all available isolates and a phylogenetic analysis of the fragment was carried out. The results of genetic and antigenic typing were in concordance, except for a few deviations. Three RABV variants with distinct antigenic patterns corresponded to well characterised genetic groups. The phylogenetic analysis also allowed the discrimination of RABVs with similar antigenic profiles originating from distant geographical locations in Russia and other states of the former Soviet Union. In some instances, more than one specific antigenic variant was detected within a phylogenetic group. A number of antigenic and genetic variants were associated with a specific host species (such as red fox, raccoon dog, wolf or polar fox) in different parts of Russia. A single, antigenically divergent, P-41-positive, rodent isolate from Siberia was described.

Development of a real-time, TaqMan reverse transcription-PCR assay for detection and differentiation of lyssavirus genotypes 1, 5, and 6

Several reverse transcription-PCR (RT-PCR) methods have been reported for the detection of rabies and rabies-related viruses. These methods invariably involve multiple transfers of nucleic acids between different tubes, with the risk of contamination leading to the production of false-positive results. Here we describe a single, closed-tube, nonnested RT-PCR with TaqMan technology that distinguishes between classical rabies virus (genotype 1) and European bat lyssaviruses 1 and 2 (genotypes 5 and 6) in real time. The TaqMan assay is rapid, sensitive, and specific and allows for the genotyping of unknown isolates concomitant with the RT-PCR. The assay can be applied quantitatively and the use of an internal control enables the quality of the isolated template to be assessed. Despite sequence heterogeneity in the N gene between the different genotypes, a universal forward and reverse primer set has been designed, allowing for the simplification of previously described assays. We propose that within a geographically constrained area, this assay will be a useful tool for the detection and differentiation of members of the Lyssavirus genus.

Rabies human diploid cell vaccine elicits cross-neutralising and cross-protecting immune responses against European and Australian bat lyssaviruses

The ability of antibodies elicited against the rabies human diploid cell vaccine (HDCV) to neutralise European bat Lyssaviruses (EBLV types-1 and -2), Australian bat Lyssavirus and classical rabies virus (RABV) has been evaluated using modified fluorescent antibody virus neutralisation (mFAVN) assays. Ninety-six percent (48 of 50) of the human post-vaccinated sera tested cross-neutralised these viruses (>or=0.5 IU/ml). Cross-protection experiments using inbred mice (RIII, k/k haplotype) were also assessed. Mice were given HDCV (twice by the intra-peritoneal route) and challenged (intra-cranially or peripherally) with a lethal dose (25 MLD(50)) of the individual viruses. The vaccine conferred statistically significant protection in 80--100% of animals challenged via the peripheral route. Levels of protection were lower following intra-cranial (i.c.) challenge. Our data provides strong evidence for broad spectrum cross-neutralisation and cross-protection of phylogroup I lyssaviruses using rabies HDCV.

Molecular epidemiology of canid rabies in Sudan: evidence for a common origin of rabies with Ethiopia

Rabies is an endemic zoonosis in Sudan with the principal reservoir species being the domestic dog. A panel of rabies virus isolates from dogs in Sudan have been used to establish a molecular phylogeny based on a partial sequence of the viral nucleoprotein. These isolates were then compared to those from countries bordering Sudan in north-east Africa. The Sudanese viruses form a tight cluster of isolates with a single outlier. When compared to other African viruses, the Sudanese isolates cluster most closely with isolates from Ethiopia to the East suggesting a common origin for rabies in both countries which supports historical records of the movement of rabies into Sudan. The Sudanese group of viruses belong to the Africa 1a group of viruses that are present throughout much of north Africa.

Development of a qualitative indirect ELISA for the measurement of rabies virus-specific antibodies from vaccinated dogs and cats

A protocol suitable for the detection of rabies virus-specific antibodies in serum samples from companion animals using an enzyme linked immunosorbent assay (ELISA) is described. This method has been used successfully for the qualitative assessment of rabies virus-specific antibodies in serum samples from a cohort of vaccinated dogs and cats. In two initial field studies, a variable population of field samples from the Veterinary Laboratories Agency (VLA), United Kingdom were tested. In the first study (n = 1000), the number of false-positive and false-negative results was 11 samples (1.1%) and 67 samples (6.7%), respectively. In the second study (n = 920), the number of false-positive and false-negative results was 7 samples (0.8%) and 52 samples (5.7%). In a third study, undertaken at l'Agence Française de Sécurité Sanitaire des Aliments (AFSSA), Nancy, France (n = 440), 1 false-positive sample (0.23%) and 91 (20.7%) false-negative samples were identified. Data generated using this prototype ELISA indicate a strong correlation for specificity when compared to the gold standard fluorescent antibody virus neutralisation (FAVN) test. Although the ELISA has a lower sensitivity than the FAVN test, it is a useful tool for rapidly screening serum samples from vaccinated companion animals. Using a cut-off value of 0.6 EU/ml, the sensitivity (R = % from VLA and 79% from AFSSA) and specificity (R = 97.3%) indices between the ELISA compared favourably with data generated using the FAVN test. The major advantages of the ELISA test are that it is a qualitative tool that can be completed in four hours, does not require the use of live virus and can be performed without the need for specialised laboratory containment. This contrasts with 4 days using conventional rabies antibody virus neutralisation assays. Using the current format, the ELISA assay described would be a valuable screening tool for the detection of rabies antibodies from vaccinated domestic animals in combination with other Office International des Epizooties (OIE) accepted serological tests.

Spill-over of European Bat Lyssavirus Type 1 into a Stone Marten (Martes foina) in Germany

European bat lyssavirus type 1 (EBLV-1, genotype 5) is known to endemically circulate in insectivorous bat populations in Germany. In August 2001, a rabies suspect stone marten (Martes foina) was found in the city of Burg (Saxony-Anhalt, Germany) and was sent to the regional veterinary laboratory for routine rabies diagnosis. Whereas brain samples repeatedly tested negative in the fluorescent antibody test for classical rabies virus (genotype 1), the mouse inoculation test and the rabies tissue culture inoculation test yielded positive results. Rabies viral RNA was also detected in the stone marten brain sample both by nested and heminested RT-PCR specific for the nucleoprotein gene and for the nucleoprotein phosphoprotein junction of rabies virus. The amplification products were sequenced to genotype the isolate. Sequence data obtained from the first-round RT-PCR products were analysed and the suspect stone marten isolate was confirmed as a rabies related virus (EBLV-1a). Phylogenetic comparison with sequences from recent genotype five isolates from Germany and Denmark showed that it was closely related to a previous isolate of EBLV-1 from a serotine bat in Saxony-Anhalt obtained in the same year in an area adjacent to the place where the EBLV-1 infected stone marten was found. Both EBLV-1 isolates share a 99.5% identity. This is the first report of an EBLV-1a spill-over from an insectivorous bat into wildlife in Europe.

European bat lyssaviruses: an emerging zoonosis

In Europe, two bat lyssaviruses referred to as European bat lyssaviruses (EBLVs) types 1 and 2 (genotypes 5 and 6 respectively) which are closely related to classical rabies virus are responsible for an emerging zoonosis. EBLVs are host restricted to bats, and have been known to infect not only their primary hosts but also in rare circumstances, induce spillover infections to terrestrial mammals including domestic livestock, wildlife and man. Although spillover infections have occurred, there has been no evidence that the virus adapted to a new host. Since 1977, four human deaths from EBLVs have been reported. None of them had a record of prophylactic rabies immunization. Only fragmentary data exist about the effectiveness of current vaccines in cross-protection against EBLVs. It is clear that EBLV in bats cannot be eliminated using conventional strategies similar to the control programmes based on vaccine baits used for fox rabies in Europe during the 1980s. Due to the protected status of bats in Europe, our knowledge of EBLV prevalence and epidemiology is limited. It is possible that EBLV is under-reported and that the recorded cases of EBLV represent only a small proportion of the actual number of infected bats. For this reason, any interaction between man and bats in Europe must be considered as a possible exposure. Human exposure through biting incidents, especially unprovoked attacks, should be treated immediately with rabies post-exposure treatment and the bat, where possible, retained for laboratory analysis. Preventative measures include educating all bat handlers of the risks posed by rabies-infected animals and advising them to be immunized. This review provides a brief history of EBLVs, their distribution in host species and the public health risks.

Risk factors associated with travel to rabies endemic countries

Increased travel to exotic destinations around the world is escalating the risk that an emerging virus may be imported into the UK. Rabies should be considered in the differential diagnosis of any encephalitic illness presenting in an appropriate epidemiological context. Molecular diagnostic tests that can rapidly discriminate rabies from other suspected infections will influence the use of anti-rabies prophylaxis for potential contacts with the victim. In 2001, the UK had two confirmed human rabies cases, imported from the Philippines and Nigeria, respectively. In case one, hemi-nested reverse transcriptase polymerase chain reaction (hn-RT-PCR) and automated sequencing confirmed the presence of rabies virus (RABV) within both the saliva and skin specimens within 36 h of sample submission. Subsequent phylogenetic analysis using a partial sequence of the nucleoprotein (N-) gene segment demonstrated that the virus was closely related to that of canine variants currently circulating in the Philippines. In the second case, the fluorescent antibody test and reverse transcriptase polymerase chain reaction (RT-PCR) confirmed the diagnosis on post-mortem tissue. Phylogenetic analysis of two genomic segments of this isolate confirmed that it was a classical RABV (genotype 1) of the Africa 2 subgroup. These cases have highlighted the capability of molecular diagnostic tests for the rapid identification and subsequent genotyping of RABV to host and geographical location. In the first instance, rabies diagnosis often rests on clinical and epidemiological grounds. Negative tests, even late in the illness, do not exclude the diagnosis as these tests are never optimal and are entirely dependent on the nature and quality of the sample supplied. For this reason, rapid molecular detection and virus typing will be essential in considering the appropriate medical treatment regimen for a patient. In addition, an early diagnosis may decrease the number of unnecessary contacts with the patient and reduce the requirement for invasive and costly interventions. Rabies should form part of a differential diagnosis for any patient presenting with a history of travel to a rabies endemic country and displaying an undiagnosed encephalopathy.

Isolation of a European bat lyssavirus type 2 from a Daubenton's bat in the United Kingdom

European bat lyssavirus type 2 (EBLV-2) has been isolated once previously from a bat in the UK in June 1996. In September 2002, a Daubenton's bat (Myotis daubentonii) found in Lancashire developed abnormal behaviour, including unprovoked aggression, while it was in captivity. Brain samples from the bat were tested for virus of the Lyssavirus genus, which includes EBLV-2 (genotype 6), and classical rabies virus (genotype 1). A positive fluorescent antibody test confirmed that it was infected with a lyssavirus, and PCR and genomic sequencing identified the virus as an EBLV-2a. Phylogenetic comparisons with all the published sequences from genotype 6 showed that it was closely related to the previous isolate of EBLV-2 in the UK and suggested links to isolates from bats in The Netherlands. The isolation of EBLV-2 from a bat found on the west coast of England provides evidence that this virus may be present within the UK Daubenton's bat population at a low prevalence level.

Phylogenetic comparison of the genus Lyssavirus using distal coding sequences of the glycoprotein and nucleoprotein genes

The phylogenetic relationships between all seven genotypes within the genus Lyssavirus were compared at the nucleotide level utilising two distal regions of the viral genome. The resulting analysis of each region produced similar, although not identical, phylogenetic results, suggesting that the evolutionary pressures on individual proteins within the genome vary. These differences are in part due to the increased variability observed within the glycoprotein sequence over the nucleoprotein sequence. Pair-wise comparison using the glycoprotein partial sequence between different isolates demonstrate that within genotypes, viruses show between 80 and 100% sequence identity, whilst between genotypes, viruses show between 50 and 75% identity. This provides a consistent guide to assigning new viruses to existing genotypes. Alignment of the amino acid sequence for the truncated glycoprotein sequence to the Pasteur Virus vaccine strain show significant residue variation between positions 139 and 170. However, residue variation tends to vary with genotype implying that these changes have not evolved due to immunological pressure from the host but have occurred following the separation of viruses into discrete groups. Comparison of the phylogenetic analysis for this partial region of the glycoprotein suggest that it gives comparable results to studies that have used larger regions of the Lyssavirus genome.

Rabies antibody testing and the UK Pet Travel Scheme

The Pet Travel Scheme (PETS) commenced on February 28, 2000, allowing pet dogs and cats from named countries to enter the UK without spending six months in quarantine as long as they met specific criteria. Since the start of the scheme to the end of February 2002, more than 45,000 animals have successfully entered the UK under PETS. In this article, Dr Tony Fooks and colleagues consider the results of serological testing under the scheme at the Veterinary Laboratories Agency and look to future developments.

First isolation of a rabies-related virus from a Daubenton's bat in the United Kingdom

On May 30, 1996, a sick Daubenton's bat (Myotis daubentonii) was recovered from the cellar of a public house in Newhaven, East Sussex. Its condition deteriorated rapidly, and it was euthanased and examined. Positive results, establishing the presence of a rabies or rabies-related virus in its brain, were obtained from the fluorescent antibody test, the rabies tissue culture isolation test, and a hemi-nested reverse-transcription PCR. The complete sequence of the nucleoprotein gene was determined and a phylogenetic analysis, based on the 470 nucleotide bases of the amino terminus of the nucleoprotein, established the genotype of the virus as European bat lyssavirus 2. Bat rabies had not previously been recorded in the UK but does occur in mainland Europe. A study of the back-trajectories of the wind on May 29 and 30, established that the infected bat possibly came from near the Franco-Swiss border.

Molecular methods to distinguish between classical rabies and the rabies-related European bat lyssaviruses

A rapid and sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the detection of classical rabies virus (genotype 1) and the rabies related European bat lyssaviruses (EBLs) (genotypes 5 and 6) was developed. When combined with specific oligonucleotide probes and a PCR-enzyme linked immunosorbent assay (PCR-ELISA), genotype 5 and 6 viruses can be distinguished from each other and from genotype 1 viruses. Ninety-two isolates from the six established genotypes of rabies and rabies-related viruses were screened by RT-PCR and PCR-ELISA to determine the specificity of the assays. All genotype 1, 5 and 6 viruses were detected by RT-PCR while none of the genotype 2, 3 and 4 viruses were detected. All the genotype 5 and 6 viruses were detected by the two PCR-ELISA probes when used in combination while none of the genotype 1-4 viruses were detected. When used individually, the PCR-ELISA probes also distinguished between the genotype 5 and 6 viruses. This new discriminatory test should allow the rapid genotyping of all lyssaviruses likely to be encountered in Europe and as such could provide useful epidemiological information in the event of an outbreak.

Assessment of template quality by the incorporation of an internal control into a RT-PCR for the detection of rabies and rabies-related viruses

A method is described to assess RNA template quality by the incorporation of a ribosomal RNA (rRNA) internal (in tube) control into a standard rabies and rabies-related virus specific RT-PCR. Specific virus and rRNA templates were co-amplified in a duplex reaction from RNA extracts derived from 60 isolates representing all six of the established lyssavirus genotypes. To ensure a wide species applicability of this technique we demonstrated that the rRNA assay was capable of functioning using the cells or tissues of 14 different mammals. Parallel studies between the duplex and the unlinked lyssavirus assay demonstrated only a minor reduction in the sensitivity of the former test. The ribosomal and viral targets (unlike beta-actin RNA) were shown to have similar degradation kinetics making rRNA amplification a good control for viral target integrity. As a consequence, the use of this system would reduce the likelihood of obtaining false negative RT-PCR results from lyssavirus infected material.

Detection and identification of rabies and rabies-related viruses using rapid-cycle PCR

The rapid identification of suspect rabies infection is essential in human cases, to ensure appropriate post-exposure treatment of contacts, and in animal cases to allow specific control strategies to be decided and implemented. We describe here the use of high speed air thermo-cycler PCR as a diagnostic tool for the detection of rabies and rabies-related viruses. Using this technique we were able to diagnose rabies in a human within 5 h. Furthermore, the application of automated sequencing of the resultant product enabled a definitive characterisation of classical rabies within 16 h. The utility of this assay was confirmed further by the successful detection of representatives of the six lyssavirus genotypes.

Heminested PCR assay for detection of six genotypes of rabies and rabies-related viruses

A heminested reverse transcriptase PCR (hnRT-PCR) protocol which is rapid and sensitive for the detection of rabies virus and rabies-related viruses is described. Sixty isolates from six of the seven genotypes of rabies and rabies-related viruses were screened successfully by hnRT-PCR and Southern blot hybridization. Of the 60 isolates, 93% (56 of 60) were positive by external PCR, while all isolates were detected by heminested PCR and Southern blot hybridization. We also report on a comparison of the sensitivity of the standard fluorescent-antibody test (FAT) for rabies antigen and that of hnRT-PCR for rabies viral RNA with degraded tissue infected with a genotype 1 virus. Results indicated that FAT failed to detect viral antigen in brain tissue that was incubated at 37 degrees C for greater than 72 h, while hnRT-PCR detected viral RNA in brain tissue that was incubated at 37 degrees C for 360 h.

Multiplex polymerase chain reaction for human herpesvirus-6, human cytomegalovirus, and human beta-globin DNA

Human cytomegalovirus and human herpesvirus-6 are closely related viruses which cause similar diseases, have similar cellular repositories of latent infection, and may be detected largely in the same types of clinical specimens. DNA amplification appears likely to play an increasing role in the diagnosis of recent and remote infection with these agents. A sensitive multiplex polymerase chain reaction was therefore developed for the two viruses and for human beta-globin DNA. Optimization of parameters such as the primers, primer concentrations, magnesium concentration, and buffer constituents was crucial in achieving a sensitive assay. Preliminary results indicated that the assay could simultaneously monitor DNA extraction from clinical specimens and allow detection of HCMV or HHV-6 in patients with diseases possibly caused by either pathogen.