Differentiation of the seven serotypes of foot-and-mouth disease virus by reverse transcriptase polymerase chain reaction

A reverse transcription-multiplex PCR strategy devised for concomitant detection and differentiation of foot and mouth disease virus serotypes O, A and Asia 1 in India

Serotype identification occupies the central part of foot and mouth disease (FMD) diagnosis workflow and vaccination decision tree. In this study, a reverse transcription-multiplex PCR (RT-mPCR) strategy wherein three assays with unique combinations of serotype specific primers targeting the VP1 region was developed to differentiate FMD virus serotypes O, A and Asia 1 based on differential size of the PCR amplicons on agarose gel. Their diagnostic performance relative to the mPCR assay in use in India was evaluated on 169 clinical samples and 210 cell culture grown virus isolates. The relative diagnostic sensitivity was found to be 99.69%, 98.78% and 99.08% for primer combinations 1, 2 and 3, respectively. These assays proved their worth by detecting serotype in three FMD suspected specimens that went undiagnosed in the existing mPCR and also by identifying multiple serotypes in the same sample. Their detection limits varied from log10 2 to log10 4 viral RNA dilution and from 100 to 0.1 TCID50 virus depending on the serotype. The validated novel mPCR assays show promise to be included in the routine diagnostic tool-box to augment the efficiency of diagnosis of FMD virus serotypes that display extreme genetic diversity and a tendency of transboundary dispersal.

Advances in the differential molecular diagnosis of vesicular disease pathogens in swine

Foot-and-mouth disease virus (FMDV), Senecavirus A (SVA) and swine vesicular disease virus (SVDV) are members of the family Picornaviridae, which can cause similar symptoms - vesicular lesions in the tissues of the mouth, nose, feet, skin and mucous membrane of animals. Rapid and accurate diagnosis of these viruses allows for control measures to prevent the spread of these diseases. Reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR are traditional and reliable methods for pathogen detection, while their amplification reaction requires a thermocycler. Isothermal amplification methods including loop-mediated isothermal amplification and recombinase polymerase amplification developed in recent years are simple, rapid and do not require specialized equipment, allowing for point of care diagnostics. Luminex technology allows for simultaneous detection of multiple pathogens. CRISPR-Cas diagnostic systems also emerging nucleic acid detection technologies which are very sensitivity and specificity. In this paper, various nucleic acid detection methods aimed at vesicular disease pathogens in swine (including FMDV, SVA and SVDV) are summarized.

Development of reverse-transcriptase, real-time PCR assays to distinguish the Southern African Territories (SAT) serotypes 1 and 3 and topotype VII of SAT2 of Foot-and-Mouth Disease Virus

Foot-and-Mouth Disease Virus (FMDV), the causative agent of Foot-and-Mouth Disease, is a highly feared, economically devastating transboundary pathogen. This is due to the virus' extremely contagious nature and its ability to utilize multiple transmission routes. As such, rapid and accurate diagnostic testing is imperative to the control of FMD. Identification of the FMDV serotype is necessary as it provides the foundation for appropriate vaccine selection and aids in outbreak source tracing. With the vast genetic diversity, there is a desperate need to be able to characterize FMDV without relying on prior knowledge of viral serotypes. In this study, the Neptune bioinformatics tool was used to identify genetic signatures specific to each Southern African Territories (SAT) 1, 2 and 3 genomes but exclusionary to the other circulating FMDV serotypes (A, O, Asia1, and the heterologous SAT1, SAT2 and/or SAT3). Identification of these unique genomic regions allowed the design of TaqMan-based real-time reverse transcriptase PCR (rRT-PCR) primer/probe sets for SAT1, SAT2 and SAT3 viruses. These assays were optimized using prototypic FMDV cell culture isolates using the same reagents and thermocycling conditions as the FMDV pan-serotype 3D rRT-PCR assay. Cross-reactivity was evaluated in tandem with the FMDV pan-serotype 3D rRT-PCR utilizing representative strains from FMDV serotypes A, O, Asia1, SAT1, SAT2 and SAT3. The SAT1, SAT2, and SAT3 primer/probe sets were specific for the homologous serotype and exclusionary to all others. SAT1 and SAT3 primer/probe sets were able to detect several topotypes, whereas the SAT2 assay was revealed to be specific for topotype VII. The SAT2 topotype VII specificity was possibly due to the use of sequence data deposited post-2011to design the rRT-PCR primers and probes. Each assay was tested against a panel of 99 bovine tissue samples from Nigeria, where SAT2 topotype VII viruses were correctly identified and no cross-reactivity was exhibited by the SAT1 and 3 assays. These novel SAT1, SAT3 and SAT2 topotype VII rRT-PCR assays have the potential to detect and differentiate circulating FMD SAT viruses.

Detection of an emerging novel sublineage Ind2001BD1 and lineage PanAsia of foot-and-mouth disease virus serotype O in cattle in Manikgonj district of Bangladesh, 2018

Background:

Foot-and-mouth disease (FMD) is an endemic disease of cloven-hoofed animals in Bangladesh and multiple outbreaks occur every year because of the FMD virus (FMDV).

Aim:

The aim of the present investigation was to determine the molecular characterization of the VP1 coding region of FMDV serotype O outbreak in cattle.

Methods:

A total of four tongue epithelial specimens were collected from clinically FMD-positive cattle during June 2018 in Manikgonj district of Bangladesh.

Results:

All four isolates were recorded positive for FMDV serotype O. The phylogenetic analysis showed that two isolates were clustered within an emerging novel sublineage Ind2001BD1 under lineage Ind2001 of FMDV serotype O, which was identified during 2012–2016 in Bangladesh. One isolate was clustered within the lineage PanAsia of FMDV serotype O and was closely related to an isolate identified in Nepal in 2009. The phylogenetic reconstruction revealed that all the four isolates belong to the Middle East–South Asia topotype.

Conclusion:

Therefore, multiple lineages of the FMDV serotype O are circulating among the cattle in the outbreak area, which make it more complex for the FMD control program in Bangladesh. A comprehensive study on the genetic characteristics of FMDV across the country is required for effective FMD prevention and control strategy.

Development of two rapid lateral flow test strips for detection of foot-and-mouth disease virus SAT 1 and SAT 3

Foot-and-mouth disease (FMD) is a highly contagious disease that affects cattle, sheep, goats, pigs, and over 70 species of wildlife. FMD continues to be a major economic concern for livestock productivity in many countries. FMDV has seven serotypes O, A, Asia 1, C, and Southern Africa Territories (SAT) 1, 2, and 3. Although SAT 1, and SAT 3 outbreaks are not as common as serotypes O, A, Asia 1, and SAT 2, outbreaks have also been reported. The recent outbreaks of SAT 1 occurred in Cameroon, Zimbabwe, South Africa, and Uganda, while most recent SAT 3 occurred in Namibia in 2019. The development of rapid and easy-to-perform FMDV detection tests is critical to control the outbreak and spread of FMD. The current project has produced monoclonal antibodies (mAb) against FMDV serotypes SAT 1, and SAT 3. Using these mAbs, two lateral flow immunochromatographic (LFI) strip tests for the detection of FMDV SAT 1, and SAT 3 have been developed. SAT 1 strip test detected 14 out of 15 SAT 1 field isolates. The SAT 3 strip test detected all four SAT 3 isolates tested, but the signal is weak for UGA 10/97 and showed no cross-reactivity with other FMDV serotypes. The diagnostic specificities of the SAT 1 and the SAT 3 tests are 100 %, which are higher than double antibody sandwich (DAS) ELISA. The diagnostic sensitivity of the SAT 1 test strip is lower than that of DAS ELISA, while the diagnostic sensitivity of the SAT 3 test strip is similar to that of DAS ELISA. The first reported SAT 1 and SAT 3 strip test combined with the previously developed SAT 2 strip test can be used for quick diagnosis in endemic countries in Africa. Rapid identification of FMDV serotypes is critical for disease control and vaccine selection. Also, these strip tests can be used in the laboratory to quickly screen samples from the field.

Seroprevalence and molecular characterization of foot-and-mouth disease virus in Chad

This study aimed at determining the seroprevalence of foot-and-mouth disease (FMD) in domestic ruminants and at characterizing the virus strains circulating in four areas of Chad (East Batha, West Batha, Wadi Fira and West Ennedi). The study was carried out between October and November 2016. A total of 1,520 sera samples (928 cattle, 216 goats, 254 sheep and 122 dromedaries) were collected randomly for FMD serological analyses. Nine epithelial tissue samples were also collected from cattle showing clinical signs, for FMDV isolation and characterization. Serological results showed an overall NSP seroprevalence of 40% (375/928) in cattle in our sample (95% CrI [19-63]). However, seroprevalences of 84% (27/32), 78% (35/45) and 84% (21/25) were estimated in cattle over 5 years of age in East Batha, West Batha and Wadi Fira, respectively. In cattle under 1 year of age, 67% (18/27) seroprevalence was estimated in Wadi Fira, 64% (14/22) in East Batha and 59% (13/22) in West Batha. It was found that the high seroprevalences have been obtained in areas where pastures are shared by several different herds but also in farms where two to three species (bovine, caprine and ovine) are raised together. ELISA PrioCHECK® FMDV types O and A and in-house solid phase competition ELISA serotyping results showed that the four O, A, SAT1 and SAT2 serotypes have circulated in Chad in 2016. However, the type SAT2 dominated with an overall seroprevalence of 43% (29/67) and was present in the four areas investigated. The phylogenetic analyses of the VP1 coding sequence allowed determining the serotype SAT2 topotype VII, close to viral strains found in Cameroon in 2015 with a similarity of 98.60%.

Outbreak investigation, molecular detection, and characterization of foot and mouth disease virus in the Southern part of Bangladesh

Objective:

The objective of the study was to investigate Foot and Mouth Disease virus (FMDV) outbreak in cattle in the Sarankhola Upazila under Bagerhat district of Bangladesh with isolation, identification, and molecular characterization of FMDV during April 2018.

Materials and Methods:

This Upazila is located at southern border of Bangladesh and surrounded by mangrove forest Sundarban. The outbreak investigation team collected epidemiological data from outbreak location. In addition, the team collected a total of 30 (15 calves, 15 adult) tongue epithelial tissue samples from a clinically FMD-affected cattle. The confirmation of FMDV and its three serotypes (A, O, and Asia-1) was performed by Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). An amplified product of the VP1 region of FMDV genome was sequenced by Sanger sequencing method after cultivation and reconfirmation of FMDV into the BHK21 cell line. Genetic variability was studied by constructing a phylogenetic tree.

Results:

The investigation survey was carried out in overall 8,393 (8,393/15,580; 53.89%) cases including 3,050 (3,050/8,393; 36.34%) cases in calf and 5,343 (5,343/8,393; 59.77%) cases in adult cattle. The overall case fatality rate (CFR) was recorded as 2.27% (354/15,580) with significantly highest CFR in the calf (71.46%; 253/354) compared to an adult. The collected all 30 samples found with FMDV positive and mixed infection of all samples with serotype Asia-1 and serotype O were observed. In BHK 21 cell line, the eight FMDV positive samples showed a typical cytopathic effect during the third passage. Finally, DNA sequence data of two isolates found closely related with the isolates of bordering country India and Myanmar.

Conclusion:

The investigation identified the risk factors involved in an outbreak of FMDV, namely, sharing the common paddy land after harvesting, no FMD vaccination, the interaction between cattle and wildlife, and cross bordering movement.

Development of fast and sensitive protocols for the detection of viral pathogens using a small portable convection PCR platform

One of the most crucial steps for preventing viral pandemics is the early detection of the causative virus on site. Various molecular and immunological approaches have been developed for virus detection. In this study, we investigated the utility of the recently introduced convection polymerase chain reaction (cPCR) platform for the rapid and sensitive detection of various animal viruses in the field, including the foot-and-mouth disease virus (FMDV) and avian influenza viruses (AIVs). Primer sets were designed to simultaneously detect two highly conserved regions of the FMDV, including the 5' untranslated region (5'-UTR) and 3D gene, and to specifically amplify the NP and hemagglutinin (HA) genes of H5 and H9 subtypes of AIVs. The portable cPCR system was able to amplify from as low as 1 to 10 copies of viral cDNAs in the singleplex mode and 10 to 100 copies of viral cDNAs in the duplex mode within 21 min. Thus, our data suggest that the cPCR protocols developed in this study are highly sensitive and enable quick detection of animal viruses in biological samples.

Designing and fabrication of new VIP biosensor for the rapid and selective detection of foot-and-mouth disease virus (FMDV)

Foot and mouth disease virus (FMDV), is a highly contagious virus due to its ease of transmission. FMDV has seven genetically distinguished serotypes with many subtypes within each serotype. The traditional diagnostic methods of FMDV have demonstrated many drawbacks related to sensitivity, specificity, and cross-reactivity. In the current study, a new viral imprinted polymer (VIP)-based biosensor was designed and fabricated for the rapid and selective detection of the FMDV. The bio-recognition components were formed via electrochemical polymerization of the oxidized O-aminophenol (O-AP) film imprinted with FMDV serotype O on a gold screen-printed electrode (SPE). The overall changes in the design template have been investigated using cyclic voltammetry (CV), atomic force microscopy (AFM), Field emission-scanning electron microscopy (FE-SEM), and Fourier-transform infrared spectroscopy (FT-IR). Optimal conditions were achieved through investigating the capturing efficiency, binding stability, selectivity and life-time of the developed biosensor. The results depicted a high selectivity of the biosensor to the serotype O over all other genus serotypes A, SAT2 and Lumpy skin disease virus (LSDV), as well as, the inactivated serotype O. The limits of detection (LOD) and quantification (LOQ) were around 2 ng/mL and 6 ng/mL, respectively, in addition to the tested repeatability and reproducibility values with a variance coefficient of 1.0% and 3.6%, respectively. In comparison with the reference methods (ELISA and PCR), the analysis of saliva real samples using the developed affordable biosensor offered 50 folds lower LOD with the possibility of an on-line monitoring in the field with no prior sample treatment.

Development of a New RT-PCR with Multiple Primers for Detecting Southern African Territories Foot-and-mouth Disease Viruses

Introduction

The extremely high genetic variation and the continuously emerging variants of foot-and-mouth disease virus (FMDV) of Southern African Territory (SAT) serotypes including SAT1, SAT2, and SAT3 make it necessary to develop a new RT-PCR for general use for monitoring viruses based on the updated genome information.

Material and Methods

A FMDV SAT-D8 one-step RT-PCR was established based on the 1D2A2B genes of the SAT serotype viruses with a multiplex primer set. FMDV A, O, C, and Asia 1 serotypes, other vesicular disease viruses, inactivated SAT viruses, and 125 bovine, ovine, caprine and porcine tissue samples collected from the Chinese mainland were included for evaluating the assay.

Results

The new RT-PCR was proven to be specific without cross-reactions with Eurasian FMDV, swine vesicular disease virus (SVDV), Seneca valley virus (SVV), or other common viral pathogens of cattle, sheep, goat, and pig. An around 257 bp-sized amplicon clearly appeared when the inactivated SAT viruses were detected. However, all 125 samples collected from FMDV-susceptible animals from the Chinese mainland which has not known SAT epidemics showed negative results.

Conclusions

A FMDV SAT-D8 one-step RT-PCR is a promising method for primary screening for FMDV SAT serotypes.

Generation of monoclonal antibodies against foot-and-mouth disease virus SAT 2 and the development of a lateral flow strip test for virus detection

Foot-and-mouth disease (FMD) remains a major economic concern for the livestock productivity in many developing countries and a continued threat to countries that are disease free because of its potential devastating impact on agricultural, food chain and tourism sectors. FMD virus (FMDV) is recognized as having seven serotypes: O, A, C, Asia 1, South African Territories (SAT) 1, 2, 3 and multiple subtypes within each serotype. FMD outbreaks due to SAT 2 have been reported in many African countries. The development of a rapid and easily performed test for FMD detection is critical for controlling FMD outbreaks and containing its spread. The present project developed a lateral flow immunochromatographic (LFI) strip test for the rapid detection of FMDV SAT 2. A panel of monoclonal antibodies (mAbs) against FMDV serotype SAT 2 was produced and characterized. One mAb (#10) was selected as the capture mAb because it reacted to all 23 SAT 2 isolates archived at the National Center for Foreign Animal Disease. The LFI strip test was developed using biotin-conjugated mAb #10, and the colloid gold-conjugated FMDV serotype-independent mAb as the detection mAb. A generic Rapid Assay Device (gRAD) with one test line and a control line was used for the test. The LFI strip test detected all 23 tested SAT 2 isolates and recent outbreak strains. The results indicated that the diagnostic specificity and sensitivity of the LFI strip test were greater than the double antibody sandwich (DAS) DAS ELISA. The ability of the LFI strip test to produce rapid diagnostic results will be useful for early on-site diagnosis during FMD outbreaks.

Development and evaluation of tailored specific real-time RT-PCR assays for detection of foot-and-mouth disease virus serotypes circulating in East Africa

Rapid, reliable and accurate diagnostic methods provide essential support to programmes that monitor and control foot-and-mouth disease (FMD). While pan-specific molecular tests for FMD virus (FMDV) detection are well established and widely used in endemic and FMD-free countries, current serotyping methods mainly rely either on antigen detection ELISAs or nucleotide sequencing approaches. This report describes the development of a panel of serotype-specific real-time RT-PCR assays (rRT-PCR) tailored to detect FMDV lineages currently circulating in East Africa. These assays target sequences within the VP1-coding region that share high intra-lineage identity, but do not cross-react with FMD viruses from other serotypes that circulate in the region. These serotype-specific assays operate with the same thermal profile as the pan-diagnostic tests making it possible to run them in parallel to produce CT values comparable to the pan-diagnostic test detecting the 3D-coding region. These assays were evaluated alongside the established pan-specific molecular test using field samples and virus isolates collected from Tanzania, Kenya and Ethiopia that had been previously characterised by nucleotide sequencing. Samples (n=71) representing serotype A (topotype AFRICA, lineage G-I), serotype O (topotypes EA-2 and EA-4), serotype SAT 1 (topotype I (NWZ)) and serotype SAT2 (topotype IV) were correctly identified with these rRT-PCR assays. Furthermore, FMDV RNA from samples that did not contain infectious virus could still be serotyped using these assays. These serotype-specific real-time RT-PCR assays can detect and characterise FMDVs currently circulating in East Africa and hence improve disease control in this region.

Complexities in Isolation and Purification of Multiple Viruses from Mixed Viral Infections: Viral Interference, Persistence and Exclusion

Successful purification of multiple viruses from mixed infections remains a challenge. In this study, we investigated peste des petits ruminants virus (PPRV) and foot-and-mouth disease virus (FMDV) mixed infection in goats. Rather than in a single cell type, cytopathic effect (CPE) of the virus was observed in cocultured Vero/BHK-21 cells at 6^th blind passage (BP). PPRV, but not FMDV could be purified from the virus mixture by plaque assay. Viral RNA (mixture) transfection in BHK-21 cells produced FMDV but not PPRV virions, a strategy which we have successfully employed for the first time to eliminate the negative-stranded RNA virus from the virus mixture. FMDV phenotypes, such as replication competent but noncytolytic, cytolytic but defective in plaque formation and, cytolytic but defective in both plaque formation and standard FMDV genome were observed respectively, at passage level BP8, BP15 and BP19 and hence complicated virus isolation in the cell culture system. Mixed infection was not found to induce any significant antigenic and genetic diversity in both PPRV and FMDV. Further, we for the first time demonstrated the viral interference between PPRV and FMDV. Prior transfection of PPRV RNA, but not Newcastle disease virus (NDV) and rotavirus RNA resulted in reduced FMDV replication in BHK-21 cells suggesting that the PPRV RNA-induced interference was specifically directed against FMDV. On long-term coinfection of some acute pathogenic viruses (all possible combinations of PPRV, FMDV, NDV and buffalopox virus) in Vero cells, in most cases, one of the coinfecting viruses was excluded at passage level 5 suggesting that the long-term coinfection may modify viral persistence. To the best of our knowledge, this is the first documented evidence describing a natural mixed infection of FMDV and PPRV. The study not only provides simple and reliable methodologies for isolation and purification of two epidemiologically and economically important groups of viruses, but could also help in establishing better guidelines for trading animals that could transmit further infections and epidemics in disease free nations.

Development and Characterization of Probe-Based Real Time Quantitative RT-PCR Assays for Detection and Serotyping of Foot-And-Mouth Disease Viruses Circulating in West Eurasia

Rapid and accurate diagnosis of foot-and-mouth disease (FMD) and virus serotyping are of paramount importance for control of this disease in endemic areas where vaccination is practiced. Ideally this virus characterization should be achieved without the need for virus amplification in cell culture. Due to the heterogeneity of FMD viruses (FMDVs) in different parts of the world, region specific diagnostic tests are required. In this study, hydrolysable probe-based real time reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays were developed for specific detection and serotyping of the FMDVs currently circulating in West Eurasia. These assays were evaluated, in parallel with pan-FMDV diagnostic assays and earlier serotype-specific assays, using field samples originating from Pakistan and Afghanistan containing FMD viruses belonging to different sublineages of O-PanAsia, A-Iran05 and Asia-1 (Group-II and Group-VII (Sindh-08)). In addition, field samples from Iran and Bulgaria, containing FMDVs belonging to the O-PanAsia^ANT-10 sublineage were also tested. Each of the three primer/probe sets was designed to be specific for just one of the serotypes O, A and Asia-1 of FMDV and detected the RNA from the target viruses with cycle threshold (C_T) values comparable with those obtained with the serotype-independent pan-FMDV diagnostic assays. No cross-reactivity was observed in these assays between the heterotypic viruses circulating in the region. The assays reported here have higher diagnostic sensitivity (100% each for serotypes O and Asia-1, and 92% [95% CI = 81.4–100%] for serotype A positive samples) and specificity (100% each for serotypes O, A and Asia-1 positive samples) for the viruses currently circulating in West Eurasia compared to the serotyping assays reported earlier. Comparisons of the sequences of the primers and probes used in these assays and the corresponding regions of the circulating viruses provided explanations for the poor recognition of some of the viruses by the earlier assays. These new assays should help in the early detection and typing of serotype O, A and Asia-1 FMDVs circulating in West Eurasia to enable improved disease control.

Diagnostic assays developed for the control of foot-and-mouth disease in India

Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease of livestock, primarily affecting cattle, buffalo and pigs. FMD virus serotypes O, A and Asia1 are prevalent in India and systematic efforts are on to control and eventually eradicate the disease from the country. FMD epidemiology is complex due to factors like co-circulation, extinction, emergence and re-emergence of genotypes/lineages within the three serotypes, animal movement, diverse farm practices and large number of susceptible livestock in the country. Systematic vaccination, prompt diagnosis, strict biosecurity measures, and regular monitoring of vaccinal immunity and surveillance of virus circulation are indispensible features for the effective implementation of the control measures. Availability of suitable companion diagnostic tests is very important in this endeavour. In this review, the diagnostic assays developed and validated in India and their contribution in FMD control programme is presented.

Development of tailored real-time RT-PCR assays for the detection and differentiation of serotype O, A and Asia-1 foot-and-mouth disease virus lineages circulating in the Middle East

Rapid and accurate diagnosis is essential for effective control of foot-and-mouth disease (FMD). In countries where FMD is endemic, identification of the serotypes of the causative virus strains is important for vaccine selection and tracing the source of outbreaks. In this study, real-time reverse transcription polymerase chain reaction (rRT-PCR) assays using primer/probe sets designed from the VP1 coding region of the virus genomes were developed for the specific detection of serotype O, A and Asia-1 FMD viruses (FMDVs) circulating in the Middle East. These assays were evaluated using representative field samples of serotype O strains belonging exclusively to the PanAsia-2 lineage, serotype A strains of the Iran-05 lineage and serotype Asia-1 viruses from three relevant sub-groups. When RNA extracted from archival and contemporary field strains was tested using one- or two-step rRT-PCR assays, all three primer/probe sets detected the RNA from homotypic viruses and no cross-reactivity was observed with heterotypic viruses. Similar results were obtained using both single- and multiplex assay formats. Using plasmid standards, the minimum detection level of these tests was found to be lower than two copies. The results illustrate the potential of tailored rRT-PCR tools for the detection and categorization of viruses circulating in the Middle East belonging to distinct subgroups of serotypes O, A and Asia-1. These assays can also overcome the problem of serotyping samples which are found positive by the generic rRT-PCR diagnostic assays but negative by virus isolation and antigen-detection ELISA which would otherwise have to be serotyped by nucleotide sequencing. A similar approach could be used to develop serotyping assays for FMDV strains circulating in other regions of the world.

Foot-and-mouth disease: past, present and future

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals including cattle, pigs, sheep and many wildlife species. It can cause enormous economic losses when incursions occur into countries which are normally disease free. In addition, it has long-term effects within countries where the disease is endemic due to reduced animal productivity and the restrictions on international trade in animal products. The disease is caused by infection with foot-and-mouth disease virus (FMDV), a picornavirus. Seven different serotypes (and numerous variants) of FMDV have been identified. Some serotypes have a restricted geographical distribution, e.g. Asia-1, whereas others, notably serotype O, occur in many different regions. There is no cross-protection between serotypes and sometimes protection conferred by vaccines even of the same serotype can be limited. Thus it is important to characterize the viruses that are circulating if vaccination is being used for disease control. This review describes current methods for the detection and characterization of FMDVs. Sequence information is increasingly being used for identifying the source of outbreaks. In addition such information can be used to understand antigenic change within virus strains. The challenges and opportunities for improving the control of the disease within endemic settings, with a focus on Eurasia, are discussed, including the role of the FAO/EuFMD/OIE Progressive Control Pathway. Better control of the disease in endemic areas reduces the risk of incursions into disease-free regions.

A portable reverse transcription recombinase polymerase amplification assay for rapid detection of foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is a trans-boundary viral disease of livestock, which causes huge economic losses and constitutes a serious infectious threat for livestock farming worldwide. Early diagnosis of FMD helps to diminish its impact by adequate outbreak management. In this study, we describe the development of a real-time reverse transcription recombinase polymerase amplification (RT-RPA) assay for the detection of FMD virus (FMDV). The FMDV RT-RPA design targeted the 3D gene of FMDV and a 260 nt molecular RNA standard was used for assay validation. The RT-RPA assay was fast (4–10 minutes) and the analytical sensitivity was determined at 1436 RNA molecules detected by probit regression analysis. The FMDV RT-RPA assay detected RNA prepared from all seven FMDV serotypes but did not detect classical swine fever virus or swine vesicular disease virus. The FMDV RT-RPA assay was used in the field during the recent FMD outbreak in Egypt. In clinical samples, reverse transcription polymerase chain reaction (RT-PCR) and RT-RPA showed a diagnostic sensitivity of 100% and 98%, respectively. In conclusion, FMDV RT-RPA was quicker and much easier to handle in the field than real-time RT-PCR. Thus RT-RPA could be easily implemented to perform diagnostics at quarantine stations or farms for rapid spot-of-infection detection.

Detection of foot-and-mouth disease serotype O by ELISA using a monoclonal antibody

An ELISA assay with monoclonal antibody (MELISA) was used to type serotype O of foot-and-mouth disease virus (FMDV). All FMDV serotype O reference strains were positive by MELISA, while other viruses such as FMDV serotypes Asia 1, C, A and classical swine fever virus, swine vesicular disease virus, and porcine reproductive and respiratory syndrome virus remained negative. Further, FMDV serotype O positive samples were able to be detected by MELISA. This assay may be particularly suitable for diagnosis of FMDV serotype O infection in field stations.

Detection of foot-and-mouth disease serotype O by ELISA using a monoclonal antibody

An ELISA assay with monoclonal antibody (MELISA) was used to type serotype O of foot-and-mouth disease virus (FMDV). All FMDV serotype O reference strains were positive by MELISA, while other viruses such as FMDV serotypes Asia 1, C, and A and classical swine fever virus, swine vesicular disease virus, and porcine reproductive and respiratory syndrome virus remained negative. Furthermore, FMDV serotype O positive samples were able to be detected by MELISA. This assay may be particularly suitable for diagnosis of FMDV serotype O infection in field stations.

Rapid typing of foot-and-mouth disease serotype Asia 1 by reverse transcription loop-mediated isothermal amplification

A reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) assay was rapidly used to detect serotype Asia 1 of foot-and-mouth disease virus (FMDV) within 45 min at 61°C. All FMDV serotype Asia 1 reference strains were positive by RT-LAMP, while other viruses such as FMDV serotypes O, C, A and classical swine fever virus, swine vesicular disease virus, porcine reproductive and respiratory syndrome virus and Japanese encephalitis virus remained negative. Furthermore, FMDV sreotype Asia 1 positive samples were able to detect by RT-LAMP assay. This RT-LAMP assay may be suitable particularly for diagnosis of FMDV serotype Asia 1 infection in field stations.

A Brief Review on Diagnosis of Foot-and-Mouth Disease of Livestock: Conventional to Molecular Tools

Foot-and-mouth disease (FMD) is one of the highly contagious diseases of domestic animals. Effective control of this disease needs sensitive, specific, and quick diagnostic tools at each tier of control strategy. In this paper we have outlined various diagnostic approaches from old to new generation in a nutshell. Presently FMD diagnosis is being carried out using techniques such as Virus Isolation (VI), Sandwich-ELISA (S-ELISA), Liquid-Phase Blocking ELISA (LPBE), Multiplex-PCR (m-PCR), and indirect ELISA (DIVA), and real time-PCR can be used for detection of antibody against nonstructural proteins. Nucleotide sequencing for serotyping, microarray as well as recombinant antigen-based detection, biosensor, phage display, and nucleic-acid-based diagnostic are on the way for rapid and specific detection of FMDV. Various pen side tests, namely, lateral flow, RT-LAMP, Immunostrip tests, and so forth. are also developed for detection of the virus in field condition.

Development of one-step multiplex RT-PCR method for simultaneous detection and differentiation of foot-and-mouth disease virus serotypes O, A, and Asia 1 circulating in Vietnam

A one-step multiplex RT-PCR method using new primers was developed for the simultaneous detection and differentiation of Vietnamese FMDV serotypes O, A, and Asia 1 directly from clinical samples. The RT-PCR method used a cocktail of one universal minus-sense primer designed in the 2B gene and three serotype-specific plus-sense primers designed in the hypervariable regions of the capsid VP1 coding gene of FMDV. These serotype-specific primer pairs amplified 658, 535, and 427 bp PCR products corresponding to FMDV serotypes O, Asia 1, and A, respectively. In this study, six well-characterized FMDV strains belonging to serotypes O, A, and Asia 1 were used as reference strains for validation tests. Among these six FMDV strains were three vaccine strains for type O (O1/Manisa), A (A22/Iraq), and Asia 1 (As1/Shamir/89). The other reference strains included one pandemic strain of FMDV serotype Asia 1 (Asia1/MOG/05) and two pandemic strains of FMDV serotype O (O/UKG/34/2001 and O/SKR/2000). For field application, 37 positive-clinical samples and 18 cell culture-adapted viruses belonging to serotypes O, A, and Asia 1, as confirmed previously by antigen ELISA for FMDV detection, were used. The present method showed high sensitivity and specificity and can be adapted for detection and typing of FMDV serotypes O, A, and Asia 1 circulating in Vietnam.

Foot-and-mouth disease virus antigen detection enzyme-linked immunosorbent assay using multiserotype-reactive monoclonal antibodies

Monoclonal antibody (MAb)-based sandwich direct enzyme-linked immunosorbent assay (MSD-ELISA) methods that can detect foot-and-mouth disease virus (FMDV) antigens, both multiserotype (MSD-ELISA/MS) (for O, A, C, and Asia 1) and single-serotype (MSD-ELISA/SS) (for O, A, and Asia 1, specifically), were developed. MAb 1H5 was used as an antigen-trapping antibody that reacted with all seven serotypes of FMDV. The MAbs 71F2, 70C4, 16C6, and 7C2 were used as peroxidase-labeled detecting antibodies for multiple serotypes (O, A, C, and Asia 1), type O, type A, and type Asia 1, respectively, in both MSD-ELISA/MS and MSD-ELISA/SS. Our MSD-ELISAs showed high specificity. They produced a very low background of negative samples (buffer, plasma, and saliva) and were able to detect FMDV antigens from clinical samples (plasma and saliva), with results correlating with those of real-time reverse transcription-PCR. In terms of sensitivity, the MSD-ELISAs showed higher optical density values against each diluted serotype antigen than the indirect sandwich ELISA method, which is currently recommended in the manual of the World Organization for Animal Health. The sensitivity and specificity of the MSD-ELISAs seem to be sufficient for the antigenic diagnosis of FMDV.

Simple and rapid lateral-flow assay for the detection of foot-and-mouth disease virus

A simple lateral-flow assay (LFA) based on a monoclonal antibody (MAb 70-17) was developed for the detection of foot-and-mouth disease virus (FMDV) under nonlaboratory conditions. The LFA was evaluated with epithelial suspensions (n = 704) prepared from current and historical field samples which had been submitted to the Pirbright Laboratory (United Kingdom) and from negative samples (n = 100) collected from naïve animals in Korea. Four FMDV serotypes (type O, A, Asia 1, and C) were detected in the LFA, but not the remaining three FMDV serotypes (SAT 1, SAT 2, and SAT 3). The diagnostic sensitivity of the LFA for FMDV types O, A, C, and Asia 1 was similar, at approximately 87.3%, to that of 87.7% obtained with antigen enzyme-linked immunosorbent assay (Ag-ELISA). The diagnostic specificity of the LFA was 98.8%, compared to 100% for the Ag-ELISA. These results demonstrate that the LFA using the FMDV MAb 70-17 to detect FMDV is a supportive method for taking rapid measurements at the site of a suspected foot-and-mouth disease outbreak in Asia before diagnosing the disease in the laboratory, thereby offering the possibility of implementing control procedures more rapidly.

Assessment of the diagnostic potential of immuno-RCA in 96-well ELISA plates for foot-and-mouth disease virus

The need for fast and very early detection of foot-and-mouth disease virus (FMDV) infection has yielded different types of diagnostic tools over the past decades: whereas very sensitive techniques such as virus isolation (VI) and more recently also real-time RT-PCR can provide evidence for the presence of low virus quantities, VI requires additional confirmation of the nature of the virus strain and both techniques (currently) lack the ability for direct serotyping. The latter usually depends on ELISA, which is a far less sensitive method and may require virus culturing. This paper elaborates on experimental efforts towards the development of an 'immuno-rolling circle amplification (RCA)' assay in 96-well plates, the aim being to increase the sensitivity of immunological FMDV detection and serotyping by means of RCA. The study attempts to explain the encountered hurdles and the complexity of the different setups tested. Conclusively, immuno-RCA in 96-well plates as a reliable diagnostic assay for FMDV seems very difficult to achieve.

Development and comparison of genome detection assays for the diagnosis of foot-and-mouth disease suspected clinical samples

Detection of foot-and-mouth disease virus (FMDV) from clinical specimens by conventional sandwich enzyme-linked immunosorbent assay (ELISA) and virus isolation in cell culture is often compromised owing to limited sensitivity and inactivation during transit, respectively. A RT-PCR (oligoprobing) ELISA in both solid and aqueous phase hybridization formats targeting an across serotype conserved site at 3C-3D region was developed and its effectiveness was compared with that of the known targets at the IRES region. A non-isotopic RNA dot hybridization assay with colorimetric detection targeting both the IRES and the 3D region were also validated, which is capable of handling high throughput samples with ease. RT-PCR (oligoprobing) ELISA and dot hybridization assay showed 1000- and 10-fold greater sensitivity than the sandwich ELISA, respectively. Robustness of these diagnostic methods was explored by examining on sandwich ELISA-negative clinical samples. Both the assays developed in the present study were able to detect viral genomes in samples undetectable by conventional ELISA, thereby demonstrating 'proof of sensitivity'. Although the potential of these assays for providing definitive diagnosis in carrier hosts and in species where clinical disease is inapparent remains to be examined, nevertheless these assays can be adapted for comprehensive surveillance of foot-and-mouth disease in India.

Foot-and-mouth disease virus: a first inter-laboratory comparison trial to evaluate virus isolation and RT-PCR detection methods

Five European reference laboratories participated in an exercise to evaluate the sensitivity and specificity of their routinely employed RT-PCR tests and cell cultures for the detection and isolation of foot-and-mouth disease (FMD) virus. Five identical sets of 20 coded samples were prepared from 10 vesicular epithelia, which were derived from submissions from suspect cases of FMD or swine vesicular disease (SVD). Sixteen samples were derived from six FMD virus positive epithelia representing four different serotypes (two each of types O and A and one each of types Asia 1 and SAT 2), two from samples which had been found to be negative by antigen ELISA and virus isolation (VI) in cell culture and two from SVD virus positive epithelia. Some of the FMD virus positive samples were prepared from 10-fold serial dilutions of three of the initial suspensions. Each laboratory tested the samples by one or more of its available RT-PCR procedures and inoculated cell cultures that it routinely uses for FMD diagnosis in attempts to isolate virus, the specificity of which was confirmed by antigen ELISA. The best of the RT-PCR assays used in each laboratory gave comparable results while the sensitivity of cell cultures was variable from high in one laboratory, moderate in two and low in two others. This prototype panel of samples would appear suitable for external quality assurance of these tests but would benefit from the inclusion of more negative samples and an extension in the serial dilution range of one or more of the FMD positive sample titration series.

Development and evaluation of a multiplex PCR for differentiation of foot-and-mouth disease virus strains native to India

A multiplex PCR (mPCR) for the differentiation of Indian FMDV serotypes, O, A, Asia 1 and C was developed and evaluated on 142 clinical and 39 cell culture samples. On the latter samples both the tests worked well with 100% efficiency, whereas on clinical samples mPCR had better efficiency than ELISA. The test was found to be specific for FMDV. The detection limit of the assay was varied among the serotypes; it was most sensitive on types A and Asia 1 and least sensitive on type C. The mPCR clearly identified the serotype and in some cases detected dual infections. The test is sensitive and reliable and can be used for serotyping of ELISA negative samples.

Microarray-based detection and typing of foot-and-mouth disease virus

Foot-and-mouth disease virus (FMDV) is the most economically important veterinary pathogen because of its highly infectious nature and the devastating effects the virus has on the livestock industry. Rapid diagnostic methods are needed for detection and typing of FMDV serotypes and differentiation from other viruses causing vesicular diseases. We developed a microarray-based test that uses a FMD DNA chip containing 155 oligonucleotide probes, 35-45 base pair (bp) long, virus-common and serotype-specific, designed from the VP3-VP1-2A region of the genome. A set of two forward primers and one reverse primer were also designed to allow amplification of approximately 1100 bp of target sequences from this region. The amplified target was labelled with Alexa-Fluor 546 dye and applied to the FMD DNA chip. A total of 23 different FMDV strains representing all seven serotypes were detected and typed by the FMD DNA chip. Microarray technology offers a unique capability to identify multiple pathogens in a single chip.

Foot-and-mouth disease

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals. The disease was initially described in the 16th century and was the first animal pathogen identified as a virus. Recent FMD outbreaks in developed countries and their significant economic impact have increased the concern of governments worldwide. This review describes the reemergence of FMD in developed countries that had been disease free for many years and the effect that this has had on disease control strategies. The etiologic agent, FMD virus (FMDV), a member of the Picornaviridae family, is examined in detail at the genetic, structural, and biochemical levels and in terms of its antigenic diversity. The virus replication cycle, including virus-receptor interactions as well as unique aspects of virus translation and shutoff of host macromolecular synthesis, is discussed. This information has been the basis for the development of improved protocols to rapidly identify disease outbreaks, to differentiate vaccinated from infected animals, and to begin to identify and test novel vaccine candidates. Furthermore, this knowledge, coupled with the ability to manipulate FMDV genomes at the molecular level, has provided the framework for examination of disease pathogenesis and the development of a more complete understanding of the virus and host factors involved.

Genomic evidence that simian virus 2 and six other simian picornaviruses represent a new genus in Picornaviridae

Analysis of the VP1 capsid protein coding region of simian virus (SV) 2, SV16, SV18, SV42, SV44, SV45, and SV49 demonstrates that they are clearly distinct from members of the Enterovirus genus and from members of other existing picornavirus genera. To further characterize this group of viruses and to clarify their classification within the Picornaviridae, we have determined the complete genomic sequence of SV2 (8126 nucleotides). The genome was typical of members of Picornaviridae, encoding a single open reading frame. The putative polyprotein contained typical picornavirus protease cleavage sites, yielding mature proteins homologous to each of the known picornavirus proteins. SV2 contained an amino-terminal extension of the reading frame, which was analogous to the leader protein of members of the Aphthovirus, Cardiovirus, Erbovirus, Kobuvirus, and Teschovirus genera, but there was no significant amino acid homology with any of these known leader proteins. The 2A protein also aligned poorly with the 2A proteins of other picornaviruses. The deduced amino acid sequences of the SV2 structural and nonstructural proteins were related to but phylogenetically distinct from those of enteroviruses and human rhinoviruses. The major distinguishing features of SV2 were the presence of a type 2 internal ribosome entry site in the 5'-NTR, a putative leader protein encoded upstream of the structural proteins, and an unusually large 2A protein. On the basis of the molecular analysis, we propose that SV2, SV16, SV18, SV42, SV44, SV45, SV49, and porcine enterovirus 8 be classified as members of a new genus in Picornaviridae and that SV2 (strain 2383) be designated as the type strain.

Detection of carrier cattle and sheep persistently infected with foot-and-mouth disease virus by a rapid real-time RT-PCR assay

The detection of foot-and-mouth disease virus (FMDV) in persistently infected carriers among exposed ruminants is of great importance in disease control. For this purpose, a real time, fluorogenic reverse transcription polymerase chain reaction (real-time RT-PCR) assay was evaluated for the identification of FMDV carrier animals. The results indicate that this real time RT-PCR assay may be suitable for detection of FMDV carrier animals.

The pathogenesis and diagnosis of foot-and-mouth disease

The pathogenesis of foot-and-mouth disease (FMD) is reviewed, taking account of knowledge gained from field and experimental studies and embracing investigations at the level of the virus, the cell, the organ, the whole animal and the herd or flock. The review also addresses the immune response and the carrier state in FMD. Progress made in understanding the pathogenesis of the disease is highlighted in relation to developments in diagnosis and methods of control.

Identification and isolation of foot-and-mouth disease virus from primary suspect cases in Korea in 2000

The Republic of Korea had been free from foot and mouth disease (FMD) since 1934, until a recent outbreak in 2000. From March to April 2000, a total of 15 FMD outbreaks due to the serotype O virus were recorded. Coincidental outbreaks of FMD in cattle or pigs by the serotype O virus were reported in the region, including Taiwan, China, Japan, Russia and Mongolia. In this report, the results of emergency investigations of FMD cases on a dairy farm located approximately 5-km from the demilitarized zone in Korea are described. The causative agent of the disease was identified as the FMD virus O by reverse transcription-polymerase chain reaction (RT-PCR) assays using primers derived from the 3D polymerase, internal ribosome entry site (IRES), 1D/2B regions, enzyme-linked immunosorbent assay (ELISA) for antigen detection and typing. Sequence data of the partial 1D/2B region obtained from vesicular fluid showed close similarity (98% sequence identity) to the Kinmen isolate of the FMD virus O in Taiwan. The causative virus was isolated using black goat fetal lung cells following propagation in unweaned mice.

Diagnosis and screening of foot-and-mouth disease

Foot-and-mouth disease (FMD) diagnostic methods are reviewed. As the presence of clinical signs alone is inconclusive, laboratory diagnosis should always be carried out. The presence of FMD virus can be demonstrated by cell culture isolation, complement fixation test, ELISA or the more recent polymerase chain reaction (PCR) method. Serological diagnosis is also a valuable tool. The virus neutralization test has been replaced by ELISA and the antibody response to some viral non-structural proteins allows to discriminate between vaccinated and infected animals on a herd basis. More rapid and accurate tests as well as an earlier detection system in preclinical state are still needed.

A method to detect major serotypes of foot-and-mouth disease virus

Nucleic acid sequence-based amplification (NASBA) is an isothermal technique that allows the rapid amplification of specific regions of nucleic acid obtained from a diverse range of sources. It is especially suitable for amplifying RNA sequences. A rapid and specific NASBA technique was developed, allowing the detection of foot-and-mouth disease virus genetic material in a range of sample material, including preserved skin biopsy material from infected animals, vaccines prepared from denatured cell-free material, and cell-free antigen-based detection kits. A single pair of DNA oligonucleotide primers was able to amplify examples of all major FMD virus subtypes. The amplified viral RNA was detected by electrochemiluminescence. The method was at least as sensitive as existing cell-free antigen detection methods.

Development of a rapid chromatographic strip test for the pen-side detection of foot-and-mouth disease virus antigen

Foot-and-mouth disease (FMD) is the most contagious animal virus disease of cloven-hoofed livestock and requires reliable and accurate diagnosis for the implementation of measures to control effectively its spread. Routine diagnosis of FMD is carried out at the OIE/FAO World Reference Laboratory for Foot-and-Mouth Disease (WRL for FMD), Pirbright by the combined use of ELISA and virus isolation in cell culture supplemented by reverse transcription polymerase chain reaction (RT-PCR) methods. These techniques require skilled personnel and dedicated laboratory facilities which are expensive. The development of a rapid and simple test for the detection of FMD virus antigen using Clearview chromatographic strip test technology for field application is described. This device detected FMD viral antigen in nasal swabs, epithelial suspensions and probangs from clinical samples submitted from the field, from animals infected experimentally and in supernatant fluids resulting from their passage in cell culture. The test system was more sensitive than ELISA for the diagnosis of all seven serotypes of FMD virus in the epithelial suspensions and nasal swabs and had equivalent sensitivity to the ELISA for the detection of contemporary virus strains in cell culture supernatant fluids. The study demonstrated the potential for this device to confirm a clinical diagnosis at the site of a suspected FMD outbreak, thereby offering the possibility of implementing control procedures more rapidly. Such pen-side diagnosis would have particular benefits in FMD emergencies, relevance to FMD control programmes which operate in endemic regions of the world such as South East Asia and for increasing disease awareness in other areas where efforts to control disease may be difficult. In each circumstance the availability of a pen-side device for diagnosis would reduce the necessity for sending routine diagnostic samples to an FMD laboratory and thereby reduce the delay in diagnosis, which can in some areas be considerable.

Molecular identification of new picornaviruses and characterization of a proposed enterovirus 73 serotype

Enteroviruses (EV) have traditionally been identified by using serotype-specific antisera in a virus-neutralization test. Three EV strains isolated in California, USA, in 1955, 1964 and 1978, and a 1995 Oman isolate, were found to be antigenically related to one another; however, the strains were not neutralized by standard EV typing antisera, suggesting that they may represent a new EV serotype. The isolates were characterized genetically by RT-PCR coupled with amplicon sequencing and comparison to a database of enterovirus nucleotide sequences. The strains were 75.3 to 87.2% identical to one another in complete VP1 nucleotide sequence, but no more than 68% identical in sequence to the prototype strain of any EV serotype. Their complete capsid sequences were closely related to one another, but only distantly related to those of any EV prototype strain. The California and Oman isolates were most closely related to members of EV cluster B, suggesting that they are unclassified members (i.e. a new serotype) of cluster B. The complete genome sequence was determined for one isolate, CA55-1988, and the predicted polyprotein sequence was 86.5 to 89.2% identical to those of other cluster B EV and 56.7 to 61.9% identical to the polyprotein sequences of EV belonging to other clusters. Isolation of this new EV serotype from samples obtained on two continents and over a period of 40 years suggests continued circulation over a wide geographical area. In keeping with standard picornavirus nomenclature, we propose that this new serotype be named 'enterovirus 73' (EV73).

Development of reverse transcription-PCR (oligonucleotide probing) enzyme-linked immunosorbent assays for diagnosis and preliminary typing of foot-and-mouth disease: a new system using simple and aqueous-phase hybridization

A reverse transcription-PCR (RT-PCR)-enzyme-linked immunosorbent assay system that detects a relatively conserved region within the RNA genome of all seven serotypes of foot-and-mouth disease virus (FMDV) has been developed. The high specificity of the assay is achieved by including a rapid hybridization step with a biotin-labeled internal oligonucleotide. The assay is highly sensitive, fast, and easy to perform. A similar assay, based on a highly variable region of the FMDV genome and employing a single asymmetric RT-PCR and multiple hybridization oligonucleotides, was developed to demonstrate the method's ability to type FMDV. Based on our theoretical and practical knowledge of the methodology, we predict that similar assays are applicable to diagnosis and strain differentiation in any system amenable to PCR amplification.

Primary diagnosis of foot-and-mouth disease by reverse transcription polymerase chain reaction

Universal and serotype-specific primer sets were used in simple reverse transcription polymerase chain reaction (RT-PCR) assays on field samples of epithelium and vesicular fluid to determine their suitability for primary diagnosis of all seven serotypes of foot-and-mouth disease (FMD). The specificity of reactions was confirmed by using other vesicular disease viruses, namely: swine vesicular disease virus, vesicular stomatitis virus and three vesiviruses. This resulted in the identification of a universal O/A/C/Asia 1 primer set (1F/1R) located in the 5' untranslated region (UTR) of the FMD virus genome for the successful detection of virus of these serotypes in clinical samples although this primer set detected FMD virus of the SAT1/2/3 serotypes less efficiently. The 5' UTR universal primer set could be used for the primary diagnosis of FMD in conjunction with the routine diagnostic methods of virus isolation in cell culture and ELISA, although a more favourable reaction would be expected with FMD viruses of the O/A/C/Asia 1 group than with those of the SAT serotypes. The other examined universal and serotype-specific primer sets, located principally in the P1 capsid-coding region, were generally inferior to the 5' UTR universal primer set. It is envisaged that this evaluation of primers will lead to the development of alternative PCR strategies, for example nested PCR formats, with concomitant improvement in the speed of primary diagnosis of FMD which under present procedures can be lengthy.