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Analysis of the epidemiological dynamics during the 1982-1983 epidemic of foot-and-mouth disease in Denmark based on molecular high-resolution strain identification.
An epidemic of foot-and-mouth disease (FMD) causing a total of 23 cases in 1982-1983, primarily on the island of Funen, Denmark, was subjected to molecular epidemiological investigations. In an attempt to exploit the quasi-species nature of foot-and-mouth disease virus strains for molecular high-resolution strain identification in order to analyse the dynamics of this epidemic, full-length VP1 coding regions were sequenced for 17 isolates collected at different farms during the epidemic. The sequence information together with epidemiological information gathered during the epidemic suggests that the epidemic was caused by at least three introductions across Danish borders and one case of airborne transmission between two islands in Denmark over a distance of 70 km. The assortment of nucleotide markers among the three strains is indicative of common recombination events in their evolutionary history, and the prerequisite of co- or superinfection of animals with variant strains in turn implies that they have a common source or epidemiologically related sources originating from an area with endemic FMD.
Co-replication of several isotypes of foot-and-mouth disease virus.
Genome segments of the foot-and-mouth disease virus isolates O1Lombardy and O3 Venezuela that encode, among other products, capsid protein VP1 were amplified using PCR, and the products were cloned and sequenced. The alignment of up to 11 O3-specific sequences revealed six silent nucleotide changes a well as six changes that cause amino acid substitutions in capsid protein VP1 at positions 45, 83, 141, 145, 170 and 178. The heterogeneity of three O1-specific sequences consisted of seven silent exchanges and amino acid changes at positions 85 and 134 on VP1. Amplification, subclonning and sequencing of cloned O3-specific cDNA was performed to examine the nature of the sequence heterogeneity. As no difference was found among five subcloned sequences, we conclude that the Taq polymerase copied the DNA correctly. The sequence heterogeneity observed with both virus isolates is, therefore, consistent with the quasispecies structure of foot-and-mouth disease virus. Furthermore, amino acid changes at a number of sites have been found to be involved in the formation or modulation of neutralizing epitopes. The novel aspect of this study is the ability to estimate, by cloning of PCR products, the number of virus isotypes, possibly varying in antigenicity, that are able to co-propagate. Seven isotypes of O3 Venezuela were identified. Some are of particular interest because they exhibit a change at VP1 codon 145 that causes the replacement of arginine, possibly essential for virus attachment to cells, by isoleucine.
The molecular epidemiology of foot-and-mouth disease virus serotypes A and O from 1998 to 2004 in Turkey.
BACKGROUND: Foot-and-Mouth Disease (FMD) causes significant economic losses in Turkish livestock. We have analysed the genetic diversity of the 1D sequences, encoding the hypervariable surface protein VP1, of Turkish isolates of serotype A and O collected from 1998 to 2004 in order to obtain epidemiological and immunological information. RESULTS: The 1D coding region of 33 serotype O and 20 serotype A isolates, obtained from outbreaks of FMD between 1998 and 2004, was sequenced. For serotype A, we confirmed the occurrence of the two subtypes IRN99 and IRN96. These subtypes are most divergent within the region encoding the immuno-dominant GH-loop. Also a close relationship to Foot-and-Mouth Disease virus (FMDV) serotype A isolates obtained from outbreaks in Iraq and Iran were detected and a clustering of isolates collected during the same period of time were found. The analysis of the deduced amino-acid sequences of these subtypes revealed evidence of positive selection in one site and one deletion, both within the GH-loop region. By inferring the ancestral history of the positively selected codon, two potential precursors were found. Furthermore, the structural alignment of IRN99 and IRN96 revealed differences between the tertiary structures of these subtypes. The similarity plot of the serotype O isolates suggested a more homogeneous group than the serotype A isolates. However, phylogenetic analysis revealed two major groups, each further divided in subgroups, of which some only consisted of Turkish isolates. Positively selected sites and structural differences of the Turkish isolates analysed, were not found. CONCLUSION: The sequence and structural analysis of the IRN99 strains is indicative of positive selection suggesting an immunological advantage compared to IRN96. However, results of antigenic comparison reported elsewhere do not substantiate such a conclusion. There is evidence that IRN99 was introduced to Turkey, in all probability from Iran. Since, a member of the IRN96 lineage was included as a component of the FMDV vaccine produced since 2000, the outbreaks caused by IRN96 strains in 2004 could be due to incomplete vaccine coverage. The Turkish type O strains, all with a VP1 structure similar to the O1/Manisa/69 vaccine, appear in several sublineages. Whether these sublineages reflect multiple samplings from a limited number of outbreaks, or if they reflect cross-boundary introductions is not clear.
The economics of foot and mouth disease.
The economic effects of foot and mouth disease (FMD) are summarised. Losses arise from the direct effects of the disease on production, costs of disease control and restriction of trade. Direct effects are of greatest importance in dairy and pig production systems. Costs of disease control, whether by stamping-out or vaccination are high. Even countries that are free of the disease incur prevention and emergency preparedness costs. The published studies indicate that where FMD eradication is feasible, this is the least-cost policy option, even allowing for the costs of prevention, emergency preparedness and the risk of outbreaks. Where eradication is not feasible, it is economically beneficial to protect high-producing livestock by vaccination. Vaccination of lower-producing animals may also be justified, especially where these animals produce milk or traction power, or where this would serve to protect high-producing livestock from disease challenge.
Endemic Circulation and Genetic Characterization of Foot-and-Mouth Disease Virus in Buffalo Populations of Bangladesh.
Foot-and-mouth disease (FMD) virus (FMDV) is endemic in Bangladesh, causing severe economic losses in the livestock sector. While it primarily affects cattle, buffaloes (Bubalus bubalis) remain highly susceptible. Therefore, this study aimed to determine the prevalence and molecular characteristics of FMDV in buffaloes across three districts (Sylhet, Rajshahi, and Noakhali) of Bangladesh from January to June 2024. In a cross-sectional study, a total of 622 nasal swabs from 67 herds were collected and tested for FMDV RNA using reverse transcription polymerase chain reaction (RT-PCR). Overall, 255 samples were positive, resulting in an individual-level prevalence of 41.0%(255/622), while 88.1% (59/67) of herds were FMDV-positive. Animal-level prevalence was highest in Sylhet (47.1%), followed by Noakhali (38.9%) and Rajshahi (37.1%). To further characterize circulating strains, eight representative RT-PCR-positive samples were sequenced, revealing the co-circulation of serotypes O (n = 5) and Asia-1 (n = 3). Phylogenetic analysis showed that the isolates belonged to the ME-SA/Ind2001e lineage of the serotype O and the Asia-1 Group V lineage, clustering with contemporary strains from Bangladesh and neighboring countries, suggesting possible intra- and transboundary transmission. Pairwise genetic distance evaluation revealed high regional similarity, while Mantel tests indicated significant associations between genetic, geographic, and temporal distances. Comparative genomic analysis revealed largely conserved genomic regions, whereas VP1 analysis indicated that purifying selection predominated across both serotypes, with serotype O exhibiting greater genetic diversity (π = 0.11642) than Asia-1 (π = 0.05258), suggesting localized antigenic variability and possible immune-mediated viral evolution. These findings highlight the need for strengthened surveillance, improved biosecurity, and integrated vaccination strategies to enhance FMD control and reduce economic losses in Bangladesh.
High-titer bicistronic retroviral vectors employing foot-and-mouth disease virus internal ribosome entry site.
Bicistronic retroviral vectors were constructed containing the foot-and-mouth disease virus (FMDV) internal ribosome entry site (IRES) followed by the coding region of beta-galactosidase (beta-gal) or therapeutic genes, with the selectable neomycin phosphotransferase gene under the control of the viral long terminal repeat (LTR) promoter. LNFX, a vector with a multiple cloning site 3' to foot-and-mouth disease virus IRES, was used to construct vectors encoding rat erythropoietin (EP), rat granulocyte colony-stimulating factor (G-CSF), human adenosine deaminase (ADA) and beta-gal. In transduced primary rat vascular smooth muscle cells the cytokines were expressed at high levels, similar to those obtained from vectors employing the viral LTR promoter. LNFZ, a vector encoding beta-gal, had a 10-fold increase in titer over that of LNPoZ, a comparable vector containing the poliovirus (Po) internal ribosome entry site. Primary canine vascular smooth muscle cells infected with LNFZ and LNPoZ expressed similar activities of beta-gal and neomycin phosphotransferase (NPT). Overall, these vectors had titers between 10(6) and 2 x 10(7) c.f.u./ml, indicating that foot-and-mouth disease virus IRES provides high-titer bicistronic vectors with high-level two gene expression.
Localization of foot-and-mouth disease virus RNA by in situ hybridization within bovine tissues.
Foot-and-mouth disease is a highly contagious disease of cloven hooved animals. In cattle, both acute and long-term persistent infections occur. Foot-and-mouth disease virus (FMDV), a picornavirus, has been shown, using virus isolation procedures, to replicate in the pharynx and soft palate of cattle. In this study, in situ hybridization has been used to detect FMDV RNA within the cells of tissues removed from infected bovines. A digoxigenin-labelled anti-sense RNA probe was prepared corresponding to a region of the FMDV genome encoding part of the RNA-dependent RNA polymerase (3D). The efficacy and specificity of this probe for in situ hybridisation was determined using virus-infected cells in tissue culture. Strong cytoplasmic staining was only detected in FMDV-infected cells. Various tissue samples were collected from FMDV-infected cattle between 5 and 17 days post-infection. Viral RNA was detected by in situ hybridisation within cells of the soft palate, tonsil and pharynx up to 17 days post-infection. This technique is useful for the study of FMDV localization in cattle both during and after the acute clinical phase of disease and may assist in identifying specific sites of virus persistence.
Synthetic peptide vaccines against foot and mouth disease.
Synthetic peptide vaccines against foot-and-mouth disease (FMD) have been under examination for several years. Recent reports indicate that effective synthetic vaccines for use in cattle are being developed. However, there are still some unresolved questions regarding the response of cattle and other animals to these vaccines. This brief review describes some recent studies of synthetic vaccines against FMD and draws attention to some deficiencies in our understanding of the response to these vaccines.
Epidemiological implications of the molecular characterization of foot-and-mouth disease virus isolated between 1996 and 2000 in Bangladesh.
Foot-and-mouth disease virus was collected during two years throughout Bangladesh. Viral RNA from 40 samples was subjected to reverse transcription-dependent polymerase chain reactions that amplify parts of the capsid protein encoding genome region, and the products obtained were sequenced. This showed that all virus isolates up to January 1999 belonged to a genotype of serotype O, observed here already in 1987, 1996 and 1997, and elsewhere since 1990. In February 2001, this virus variant was introduced into Great Britain and then transmitted to other European countries. The capsid protein sequences of an isolate of 2001 from the Netherlands is provided. Later isolates from Bangladesh, however, belonged to a genotype of serotype A that had been transmitted to Albania in 1996. No virus of type Asia1 was found, although it circulated in Bangladesh in 1996. Instead, this genotype of Asia1 virus was observed in Iran late in 1999, and transmitted from Turkey to Greece in July 2000. The results indicate continued intercontinental transmission of foot-and-mouth disease viruses that circulate in central Asia.
DNA fragment encoding human IL-1beta 163-171 peptide enhances the immune responses elicited in mice by DNA vaccine against foot-and-mouth disease.
DNA vaccine has been tested for protection against foot-and-mouth disease. However, the relatively low efficacy of DNA vaccine in inducing immune responses in large animals has restricted its practical use. Interleukin-1 plays an essential role in amplifying both the cellular and humoral immune responses to foreign antigens, and may therefore represent a good candidate as an adjuvant of DNA vaccines. Since the inflammatory activity of IL-I may restrict its application in DNA vaccine treatment, we explored the possibilities of augmenting immune responses without unwanted inflammatory effects using the IL-1beta fragment (amino acids (aa) 163-171), which is essential for IL-1 receptor-1 binding. The DNA fragment encoding the human IL-1beta fragment (aa 163-171) was fused to foot-and-mouth disease virus (FMDV) DNA vaccine, and injected into mice to analyse its immune response. Compared with control mice receiving FMDV DNA vaccine alone, significant increases in the FMDV-specific antibody response and also in T cell proliferation were observed in mice receiving IL-1beta (163-171)-FMDV. These results suggested that DNA fragment encoding IL-1beta 163-171 peptide might represent a good candidate for an adjuvant of FMDV DNA vaccine.
A preliminary study of the pathogenesis of foot-and-mouth disease virus using in situ hybridization.
Five adult guinea pigs were inoculated intraepithelially in the right hindfoot pad with foot-and-mouth disease virus. Animals were euthanatized with carbon dioxide at 4, 10, 24, 48, and 72 hours post-inoculation. Generalized disease developed in the guinea pigs, as evidenced by depression and inappetance by 24 hours post-inoculation and by the formation of vesicles in the noninoculated hindfoot pad by 48 hours post-inoculation. By in situ hybridization, using a 500 base pair biotinylated RNA probe, viral nucleic acid was detected in the noninoculated fore- and hindfoot pads as early as 10 hours post-inoculation, well before any pathologic changes associated with foot-and-mouth disease virus infection were detected. These tissues remained consistently positive for the presence of viral nucleic acid up to the end of the experiment. At this time, in the forefoot pad, even though virus had first been detected with certainty in that tissue 62 hours previously, there was still no microscopic evidence of foot-and-mouth disease virus-induced damage in the histologic section. Similarly, tongue tissue was positive by in situ hybridization at 4, 48, and 72 hours post-inoculation, yet there was never any microscopic evidence of degeneration or vesicle formation. From this preliminary study, it appears that, in the guinea pig, the virus is widely disseminated to foot pads and tongue, with epidermal lesions resulting only in selected areas.
Investigation of an outbreak of foot-and-mouth disease in vaccinated dairy cattle in Thailand.
An outbreak of foot-and-mouth disease that spread between two related vaccinated dairy herds was investigated. Although the cattle were of similar vaccination status, in one herd there was high morbidity, whereas in the other there was considerably lower morbidity. The relationship between the vaccine virus and the outbreak virus was expressed as an r value determined by the two-dimensional neutralisation test. Bovine serum homologous to the vaccine virus indicated a close antigenic relationship between the vaccine virus and the outbreak virus (r = 0.61). The source of the outbreak virus was not determined. The investigation suggested a requirement for close contact between stock for foot-and-mouth disease to spread in a tropical environment, in contrast to the capacity of the disease to spread considerable distances by aerosol transmission in temperate climates.
Field and laboratory analysis of an outbreak of foot and mouth disease in Bulgaria in 1991.
In July 1991, an outbreak of foot and mouth disease (FMD) occurred near Stefan Karadjovo village in Boliarovo (south-east Bulgaria, close to the Turkish border). The virus isolated was identified in Bulgaria as serotype O and this was subsequently confirmed by the World Reference Laboratory for Foot and Mouth Disease in Pirbright (United Kingdom). Serological studies using bovine sera and monoclonal antibody analysis were made. In addition, the sequence of approximately 170 nucleotides at the 3' end of the 1D gene was determined for the field isolate and for vaccine strains used in Bulgaria. These were compared with other sequences of type O FMD viruses from outbreaks in the Middle East. Serum samples were taken from domestic animals in the region close to the outbreak and examined for anti-FMD virus antibodies to assess the extent (if any) of spread of the virus before or after the outbreak. No evidence of infection was found in these animals. The virus involved in the Bulgarian outbreak was antigenically similar to the O1 vaccine strains but probably did not originate from these strains. The virus was closely related genetically to a group of viruses isolated in the Middle East since 1987, suggesting that it may have been introduced into Bulgaria from an area in the Middle East by unidentified means.
New approaches to vaccination against foot-and-mouth disease.
The economically important foot-and-mouth disease has been successfully controlled in Western Europe by comprehensive immunization using killed vaccine. The author discusses the wisdom of abandoning this policy, and outlines research into alternative vaccines using recombinant DNA technology, in particular using synthetic peptides.
Kinetics of cell infection and penetration by the virus of foot-and-mouth disease.
Thorne, H. V. (Research Institute, Animal Virus Diseases, Pirbright, England). Kinetics of cell infection and penetration by the virus of foot-and-mouth disease. J. Bacteriol. 84:929-942. 1962.-The kinetics of cell infection by the virus of foot-and-mouth disease were determined, using acidification to pH 5.7 to eliminate virus from the system and to stop the reaction at required times. The infection curve was sigmoidal in form with an initial lag stage followed by a linear region of slope, at moderate concentrations, proportional to the virus and cell concentrations. The infection rate was very small below 15 C but increased rapidly with increasing temperature. Cell infection was 90% complete in about 3 min at 37 C and about 20 min at 25 C. By comparison with kinetic equations derived for a simple model of the infection process, adsorption and penetration rate constants were calculated. The adsorption rate constants were of the same order as those obtained from direct measurements of virus adsorption. The half-time for the penetration reaction was about 30 sec at 37 C and 6 min at 20 C; the rate decreased to near zero values below 15 C. The energy of activation for penetration was 24,000 cal/mole.
The eradication of foot-and-mouth disease: a parallel problem.
Poliomyelitis and foot-and-mouth disease (FMD) can both be prevented by vaccination. The vaccines are highly effective but they differ in that, whereas in most countries attenuated viruses have been used to control poliomyelitis, FMD vaccines are prepared from the virulent viruses. The reasons for choosing inactivated vaccines for FMD are (i) the demonstration several decades ago that a virus which was attenuated for one species could be virulent for another and (ii) the great antigenic variability of the virus. This has meant that the viruses to be used for vaccination have to "match" those occurring in the field. It also means that they should only be handled under strict conditions of containment.
The foot-and-mouth disease situation in Iran.
Foot-and-mouth disease has been known in Iran since long ago. Typing of virus was done in 1950 at Mérieux Institute and since 1959 at Razi Institute. Type Asia 1 was isolated three times: in 1957, in 1964 and in 1973. In June 1962, FMD type SAT 1 entered Middle-Eastern countries; it was soon controlled, and completely eradicated by the end of 1963. At the present time, endemic types of FMD cause limited and sporadic outbreaks in some regions of Iran; their incidence is lowered every year. Except the endemic types A and O, all other types in Iran are considered as exotic. The control measures are: 1) stamping-out policy against exotic types, 2) mass-vaccination of all healthy susceptible animals by a polyvalent vaccine, 3) regular disinfection of premises and utensils, 4) strict application of sanitary measures.