Global situation of foot-and-mouth disease (FMD)--a short review

This article reviews the actual world FMD situation. In 2000, fifty nine countries officially reported outbreaks of FMD. The disease occurred in Europe (Greece), Asia (Russia, Mongolia, Bangladesh, Cambodia, China, Japan, Laos, Nepal, Pakistan, Philippines, Republic of Korea, Taiwan, Thailand, Vietnam, Iran, Iraq, Turkey, in Caucasian region--Georgia, Azerbaijan and Armenia as well as in Kazakhstan, Kyrgyzstan, Turkmenistan and Tajikistan), Africa (Egypt, Kenya, Mauritania, South Africa, Tanzania, Uganda, Malawi, Namibia, Zambia and Zimbabwe) and in South America (Brazil, Colombia, Uruguay, Bolivia, Peru, Ecuador and Venezuela). In 2001, FMD was still spreading throughout the endemic regions and appeared in some of the west European countries--Great Britain, The Netherlands, France and Ireland. In South America, FMD occurred in Argentina, Uruguay, Brazil and Colombia. In Asia the FMD spread in Turkey, Iran, Afghanistan, Georgia, Azerbaijan, Mongolia, Kuwait, Bahrain, Yemen, Qatar, United Arab Emirates, Oman, Iran, Bhutan, Nepal, Malaysia, Philippines, Thailand and Taiwan. The FMD situation in Africa was unclear, but probably most countries in West, East and South Africa were affected. The most recent data of the OIE from May 2002 confirmed FMD outbreaks in population of pigs in Republic of Korea.     

Molecular epidemiology of foot-and-mouth disease virus type A in South America

A databank of 78 VP(1) complete sequences of type A foot-and-mouth disease virus (FMDV) from South American isolates was constructed. Forty-nine samples corresponded to FMDV that circulated between the years 1999-2008, mainly in Venezuela, where most type A outbreaks have occurred lately and twenty-nine to strains historically relevant for the continent. The phylogenetic analysis showed that all South American FMDV belonged to the Euro-SA topotype. Sixteen subgenotypes could be identified, based on a 15% nucleotide divergence cut-off criterion: eight are extinguished, three were active until the year 2002 and the remaining five circulated in Venezuela during the years 2001-2007, illustrating the potential for FMDV diversification under appropriate selective pressure. The last emergencies reported in already-free areas of Colombia in 2004 and 2008 were closely related to isolates acting in Venzuela. Evidence of positive selection over codon 170, within the immunogenic site 4 of VP1 protein, was recorded. A codon deletion in amino acid position 142, within the G-H loop, was found in some isolates within subgenotypes 14, 15 and 16. Conversely amino acid deletion 197 was restricted to all isolates within a particular genetic cluster. The present work is the first comprehensive phylogenetic analysis of FMDV type A in South America, filling a gap of knowledge with respect to both, historical and acting viruses. The results provided evidence that supports the ecosystem dynamics in the region, and also served as an input to establish genetic links of emergencies in already-declared free areas, highlighting the need for strengthening control activities.     

Molecular epidemiology of serotype O foot-and-mouth disease virus isolated from cattle in Ethiopia between 1979-2001

Partial 1D gene characterization was used to study phylogenetic relationships between 17 serotype O foot-and-mouth disease (FMD) viruses in Ethiopia as well as with other O-type isolates from Eritrea, Kenya, South and West Africa, the Middle East, Asia and South America. A homologous region of 495 bp corresponding to the C-terminus end of the 1D gene was used for phylogenetic analysis. This study described three lineages, viz. African/Middle East-Asia, Cathay and South American. Within lineage I, three topotypes were defined, viz. East and West Africa and the Middle East-Asia together with the South African isolate. The Ethiopian isolates clustered as part of topotype I, the East African topotype. Two clades (based on < 12 % nucleotide difference) A and B were identified within the East African isolates, with clade A being further classified into three significant branches, A1 (80% bootstrap support), A2 (89% bootstrap support) and A3 (94% bootstrap support). Clade B consisted of two Kenyan isolates. Within topotype I, the 17 Ethiopian isolates showed genetic heterogeneity between themselves with sequence differences ranging from 4.6-14 %. Lineage 2 and 3 could be equated to two significant topotypes, viz. Cathay and South America. Comparison of amino acid variability at the immunodominant sites between the vaccine strain (ETH/19/77) and other Ethiopian outbreak isolates revealed variations within these sites. These results encourage further work towards the reassessment of the type O vaccine strain currently being used in Ethiopia to provide protection against field variants of the virus.     

Molecular epidemiological studies on foot-and-mouth disease type O Taiwan viruses from the 1997 epidemic

Sequence diversity was assessed of the complete VP1 gene directly amplified from 49 clinical specimens during an explosive foot-and-mouth disease (FMD) outbreak in Taiwan. Type O Taiwan FMD viruses are genetically highly homogenous, as seen by the minute divergence of 0.2-0.9% revealed in 20 variants. The O/HCP-0314/TW/97 and O/TCP-022/TW/97 viral variants dominated FMD outbreaks and were prevalent in most affected pig-raising areas. Comparison of deduced amino acid sequences around the main neutralizable antigenic sites on the VP1 polypeptide showed no significant antigenic variation. However, the O/CHP-158/TW/97 variant had an alternative critical residue at position 43 in antigenic site 3, which may be due to selective pressure in the field. Two vaccine production strains (O1/Manisa/Turkey/69 and O1/Campos/Brazil/71) probably provide partial heterologous protection of swine against O Taiwan viruses. The type O Taiwan variants clustered in sublineage A1 of four main lineages in the phylogenetic tree. The O/Hong Kong/9/94 and O/1685/Moscow/Russia/95 viruses in sublineage A2 are closely related to the O Taiwan variants. The causative agent for the 1997 epidemic presumably originated from a single common source of type O FMD viruses prevalent in neighboring areas.     

Foot-and-mouth disease (FMD) in the Maghreb and its threat to southern European countries

Foot-and-mouth disease (FMD) is a highly contagious and transboundary viral disease of domesticated and wild cloven-hoofed animals. The present study summarizes the knowledge generated from the epidemiology, diagnosis, and surveillance of the disease in the Maghreb (2014–2015) in assessing its threat to southern European countries. Currently, two serotypes of the FMD virus (O and SAT-2) and four lineages are circulating in the Maghreb region. The introduction of serotype SAT-2 in Libya and Mauritania in 2012 and 2015 respectively sets their neighbors and subsequently south European countries at constant risk of FMD re-emergence. The potential pathways of FMD introduction to southern European countries from the Maghreb are the illegal introduction of infected animals and animal products, particularly meat or meat products carried by refugees.

     

猪O型口蹄疫基因工程疫苗候选株的构建及其免疫原性分析

近年来,O型口蹄疫病毒已演化出多种谱系.目前应用的疫苗已不能有效保护多谱系口蹄疫的流行,这给我国猪口蹄疫的防控带来了极大的困难.为了进一步发展免疫原性好、抗原谱广的猪O型口蹄疫疫苗候选株,本研究以O/HN/93现用疫苗毒株的感染性克隆为骨架,构建了含VP3(58位)和VP1(43、48、137、139、140、141和142位)氨基酸改造的全长克隆.线性化的全长cDNA和T7RNA聚合酶质粒共转染BHK细胞后获得拯救病毒.RT-PCR和乳鼠致病性试验表明拯救病毒遗传稳定,具有与亲本病毒相似的致病性.用拯救的基因工程病毒灭活疫苗免疫猪28 d后分别用中国谱系、泛亚谱系和缅甸98谱系猪源毒的流行毒攻击,结果均获得了完全保护(16/16).O/HN/93灭活疫苗免疫猪能完全保护泛亚谱系和缅甸98谱系猪源病毒的攻击(16/16),但不能完全保护(12/16)中国谱系猪源病毒的攻击.结果表明基因工程病毒制备的灭活疫苗提高了对中国型猪源谱系病毒的免疫保护,拓展了抗原谱,是具有良好开发前景的疫苗候选株.     

The 3A non-structural-protein coding region of the southern African SAT type isolates differs from that of other foot-and-mouth disease viruses

The 3A non-structural protein of foot-and-mouth disease viruses is a relatively conserved protein comprising 153 amino acids. Recent studies have demonstrated correlation between mutations in the 3A non-structural-protein-coding region, including a 10-amino acid deletion, and attenuation of the viruses in cattle. Although the 3A coding region of several type A, O and C isolates has previously been described, nucleotide sequence data of the 3A coding region of the South African Types (SAT) 1, 2 and 3 viruses are limited. Therefore, the 3A non-structural-coding region of different SAT serotypes was determined, analysed and compared to that of European, South American and Asian isolates. The 3A regions of the SAT isolates investigated differed markedly from that of types A, O, C and Asia-1, but were similar within the group.     

Extensive antigenic and genetic variation among foot-and-mouth disease type A viruses isolated from the 1994 and 1995 foci in S?o Paulo, Brazil.

Nine foot-and-mouth disease virus (FMDV) type A isolates recovered from the field FMD foci in S?o Paulo State, Brazil, during 1994 and 1995 (a period preceding the last reported focus of FMD in 1996 in this state) were compared among themselves and with the reference vaccine strain A(24)Cruzeiro. The techniques used were sandwich ELISA, virus neutralization (VN), polyacrylamide gel electrophoresis (PAGE) of the structural polypeptides and direct sequencing of the VP1-coding region (1D gene). Results of VN were recorded as serological relationships "R" and those from ELISA were expressed as percentage of the homologous reaction "r". ELISA and VN gave comparable results (correlation coefficient, 0.936) allowing assignment of these field viruses to four groups which were distinct from the A(24)Cruzeiro strain. PAGE and 1D nucleotide sequencing were also able to distinguish between these viruses. The high level of genetic and antigenic variation found when comparing the A(24)Cruzeiro vaccine strain and type A strains recovered from the last identified foci of FMD came from a formerly endemic area where vaccination with polyvalent vaccines (O(1)Campos, A(24)Cruzeiro and C(3)Indaial) had been extensively applied. The similarity between the results of the serological and genetic analyses suggest that the antigenic differences found are mainly located in the 1D protein.     

Retrospective genetic analysis of SAT-1 type foot-and-mouth disease outbreaks in West Africa (1975-1981)

The complete 1D genome region encoding the immunogenic and phylogenetically informative VP1 gene was genetically characterized for 23 South African Territories (SAT)-1 viruses causing foot-and-mouth (FMD) disease outbreaks in the West African region between 1975 and 1981. The results indicate that two independent outbreaks occurred, the first involved two West African countries, namely Niger and Nigeria, whilst the second affected Nigeria alone. In the former epizootic, virus circulation spanned a period of 2 years, whilst in the latter virus was recovered from the field over a 3 year period. Comparison of the West African viruses with SAT-1 viruses from other regions on the continent revealed that the two West African lineages identified in this study are regionally distinct. Furthermore, variation in VP1 gene length was identified in SAT-1 viruses for the first time, further emphasizing the uniqueness of these pathogens in West Africa. This first retrospective analysis in which the molecular epidemiology of SAT-1 viruses in West Africa is reported, provides a useful measure of the regional variation of these viruses and is an essential first step in the establishment of a West African sequence database that will be a useful reference for future outbreak eventualities.     

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.     

The BSE Emergency in Lombardy

Foot and mouth disease (FMD) is a limiting factor for the economic progress of the animal industry in South America. The presence of the disease results in the imposition of national and international sanitary barriers to animals and animal products, and, most especially, a reduction in the availability of protein from animal origin and in income. Rapid and accurate identification of infected animals, those with either clinical or subclinical disease as well as with persistent infection, is essential for maintaining an efficient eradication programme. The polymerase chain reaction was used to rapidly identify infected animals. With a primer set that corresponds to a conserved region of the 3D sequence of the viral genome, it was possible to amplify, regardless of the serotype, 116 strains of FMD virus, of which 109 were strains collected from outbreaks of FMD throughout South America from 1945 to the most recent outbreaks in 2000/2001. The PCR technique should be of considerable value in facilitating the diagnosis of FMD in South America. where laboratory resources are limited and a rapid response is needed, particularly in areas where national programmes for controlling or eradicating the disease are being implemented.     

Phylogenetic analysis of recent classical swine fever virus (CSFV) isolates from Assam, India

Classical swine fever (CSF), a highly contagious viral disease of pigs, is endemic in India. As there is no information concerning the accurate genetic typing of classical swine fever virus (CSFV) isolates in India, 16 CSF viruses isolated during 2005-2007 from domestic pigs in different districts of Assam were typed in 5′ UTR (150 nucleotides). To confirm the genetic typing results and to study the genetic variability, selected viruses were also analyzed in E2 (190 nt) and NS5B gene (409 nt) regions. Phylogenetic analysis revealed that all the 16 CSFV isolates analyzed belonged to group 1 and subgroup 1.1 in contrast to the situation in other Asian countries. Additionally, analysis in E2 and NS5B region placed the Indian isolates in a clearly separated clade within subgroup 1.1. The results suggest that subgroup 1.1 CSF viruses are currently circulating in India, which is important for epidemiology and control of CSF.     

Molecular characterization of rabies virus isolates from Trinidad

Bovine rabies continues to be a serious problem facing the cattle industry in South and Central America. Although Trinidad played an important role in originally demonstrating the link between bats and bovine rabies, relatively little is known about rabies in Trinidad, an island 7miles off the coast of Venezuela. In order to obtain a more complete understanding of bovine rabies in the region, we report herein on a study undertaken in Trinidad to characterize isolates of rabies virus obtained from infected cattle. A portion of the nucleotide sequence of the nucleoprotein gene from six rabies virus isolates collected from bovine rabies from the years 1997, 1998 and 2000 was determined and compared both to themselves and the nucleotide sequence of other South American isolates. Results indicate that there are at least two independently evolving variants of rabies virus in Trinidad. The nucleotide sequence of either variant failed to match completely the sequence of South American isolates. However, the lack of South American isolates from coastal regions facing Trinidad leaves undetermined the question of South American influence on rabies in Trinidad. The results of this study helps complete the picture of bovine rabies in the South American region and provide basic information required locally for the creation of an effective rabies control and eradication strategy.     

Molecular typing of sand fly species (Diptera, Psychodidae, Phlebotominae) from areas endemic for Leishmaniasis in Ecuador by PCR-RFLP of 18S ribosomal RNA gene

Surveillance of the distribution of sand fly species is important for prediction of the risk and expansion of Leishmania infection in endemic and surrounding areas. In the present study, a simple and reliable method of typing New World Lutzomyia species circulating in endemic areas in Ecuador was established by using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique. PCR-RFLP of 18S ribosomal RNA (rRNA) genes with the restriction enzyme AfaI and subsequently HinfI successfully identified seven sand fly species in nine endemic areas in Ecuador. Although intraspecific genetic-diversity affecting the RFLP-patterns was detected in a species, the patterns were species specific. The method promises to be a powerful tool for the classification of New World Lutzomyia species.     

Sequence variability in the structural protein-encoding region of foot-and-mouth disease virus serotype Asia1 field isolates

A total of 30 field isolates of foot-and-mouth disease virus (FMDV) serotype Asia1 belonging to two different lineages and five isolates belonging to a divergent group as delineated earlier in 1D (encodingVP1 protein) gene-based phylogeny were sequenced in the structural protein (P1) coding region. Phylogenetic comparison of these isolates along with some of the published exotic sequences revealed the presence of five different lineages around the world. Similar grouping pattern was observed for the P1 region and 1D gene-based phylogeny, where the Indian isolates were clustered in two genetic lineages. The recently identified divergent group of virus falls into a separate sub-cluster. Similar grouping was also observed in L gene-based phylogeny. Comparison of amino acid sequences identified lineage-specific signature residues in all the structural proteins. Comparison of Asia1 field isolates at the identified key residues of other FMD viruses involved in the formation of the heparan sulfate-binding ligand confirmed many of them to be conserved and the presence of VP3(56) Arg suggested their cell culture adaptation. Although a considerable genetic variation was observed among the isolates of present study, all of them tested in micro-neutralization test were serologically related to the vaccine strain.     

Emergence of a novel subgroup within the widely circulating lineage of foot-and-mouth disease virus serotype Asia 1 in India

The complete VP1 encoding (1D) gene of 54 foot-and-mouth disease (FMD) virus serotype Asia1 field isolates, most of which were isolated during 2000 and 2001, was sequenced. The phylogenetic analysis identified a novel subgroup (>10% nucleotide divergence) within the widely circulating lineage of this serotype. The newly emerged viruses were responsible for disease outbreaks in both cattle and buffaloes and were present in six different states in the country. Amino acid sequence comparison of these isolates revealed significant sequence divergence at many of the amino acid positions in comparison to those of lineage VI-A and C. Emergence of such viruses may affect the efficacy of vaccine strain currently used for protection against FMD in India.     

Evaluation of foot and mouth vaccination for yak (<Emphasis Type="Italic">Bos grunniens</Emphasis>) in Pakistan

In northern Pakistan, many farming communities rely on domestic yak (Bos grunniens) as a principle source of income. A 2006 participatory disease surveillance report from this region indicated that foot-and-mouth disease (FMD) is the most prevalent annual disease of yak. Our objectives of this study were to determine exposure levels of yak to FMD virus; implement a vaccination program based on current, regional FMD virus serotypes and subtypes; and quantify immune responses following vaccination. Blood samples were used to determine pre-vaccination exposure of animals to FMD virus by antibody presence to non-structural proteins of FMD virus using a 3-ABC trapping indirect ELISA. Vaccine used consisted of FMD serotypes ‘O’ (PanAsia-2), ‘A’ (Iran-05), and ‘Asia-1’ (Shamir), but changed later during the study to match newly circulating viruses in the country (‘O’-PanAsia-2; ‘A’-Turk-06 and Asia-1-Sindh-08). Three hundred sixty-three blood samples were tested from selected villages to determine pre-vaccination FMD virus exposure in yak with an average of 37.7%. Immune responses from initial vaccination and booster dose 30 days later showed clear protective levels (as mean percent inhibition) of antibodies against structural proteins of serotypes ‘O,’ ‘A,’ and ‘Asia-1.’ These responses remained above threshold positive level even at day 210 following initial vaccination. Results of sero-surveillance and anecdotal information of repeated FMD outbreaks demonstrate the persistence of FMD virus of yak in northern Pakistan. Laboratory results and field observations clearly indicated that yak can be protected against FMD with a good quality vaccine with FMD serotype(s) matching current, regionally circulating FMD virus.     

Molecular evolutionary analysis reveals Arctic-like rabies viruses evolved and dispersed independently in North and South Asia

BackgroundArctic-like (AL) lineages of rabies viruses (RABVs) remains endemic in some Arctic and Asia countries. However, their evolutionary dynamics are largely unappreciated.ObjectivesWe attempted to estimate the evolutionary history, geographic origin and spread of the Arctic-related RABVs.MethodsFull length or partial sequences of the N and G genes were used to infer the evolutionary aspects of AL RABVs by Bayesian evolutionary analysis.ResultsThe most recent common ancestor (tMRCA) of the current Arctic and AL RABVs emerged in the 1830s and evolved independently after diversification. Population demographic analysis indicated that the viruses experienced gradual growth followed by a sudden decrease in its population size from the mid-1980s to approximately 2000. Genetic flow patterns among the regions reveal a high geographic correlation in AL RABVs transmission. Discrete phylogeography suggests that the geographic origin of the AL RABVs was in east Russia in approximately the 1830s. The ancestral AL RABV then diversified and immigrated to the countries in Northeast Asia, while the viruses in South Asia were dispersed to the neighboring regions from India. The N and G genes of RABVs in both clades sustained high levels of purifying selection, and the positive selection sites were mainly found on the C-terminus of the G gene.ConclusionsThe current AL RABVs circulating in South and North Asia evolved and dispersed independently.