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[Outbreak of foot-and-mouth disease in Northern Benin during the 1990-1991 dry season].

An outbreak of foot-and-mouth disease damaged the North-Benin during the 1990-1991 dry season (November to May). Coming from outside the Benin, it spread out very quickly in the country essentially because of trans-humant herds. No measures have been taken to limit this sickness which is endemic and which regularly exhibits outbreaks in Benin. Antibodies to types A, O and SAT2 of the foot-and-mouth disease virus were detected in the sera during this outbreak.

Animals↗

Foot-and-mouth disease: the risk for Great Britain after 1992.

Mass annual vaccination against foot-and-mouth disease, previously applied by eight member states in the European Community (EC), was progressively phased out during 1990-91. The other four member states (the United Kingdom, Denmark, the Republic of Ireland and Greece) either never have vaccinated or ceased to do so several years ago. The EC should increase its international competitiveness if it maintains its present foot-and-mouth disease-free, non-vaccinating status. Freedom from disease and a harmonised disease control policy will also permit unrestricted movement of livestock and animal products throughout the EC when the single market is completed in 1992. Vaccination against foot-and-mouth disease on continental Europe has greatly reduced the number of outbreaks during the last 30 years and this reduction has been of indirect benefit to Great Britain. However, the cessation of vaccination will result in a higher proportion of fully susceptible cattle and in the event of outbreaks will increase the likelihood of the rapid dissemination of virus and increase the risk that the infection will enter Great Britain. The main risks of entry are likely to be associated with live animals in which the disease can be mild or inapparent, ie, sheep and goats, and with airborne virus originating from pigs on the nearby continent especially in Brittany and the Benelux countries where they are present in very high densities.

Animals↗

[Immune response against foot-and-mouth disease virus in cattle: effect of vaccination].

Foot and Mouth Disease Virus (FMDV) is one of the most feared animal virus and vaccination still has to be used in many countries. In previous reports, using a murine model, we studied the cellular basis of immune responses against FMDV and were able to show that they are atypical. In cattle, although complete protection may be attained after only one dose of killed virus vaccine, very little is known about protection against FMDV, except for antibody responses, but practically nothing concerning the cellular basis of their immune response. Moreover, since neutralizing titers do not always correlate with protection, the potency of vaccines in controlled by viral challenge. Our aim is to study cellular immune responses against FMDV, and to search for a correlate to protection. As a first step, 55 virgin cattle from a non endemic area (Patagonia) were divided into three groups: C: non immunized controls; HS: immunized with saponine containing vaccine; and EO: with oil emulsified vaccine. After vaccination, they were carried to an endemic area (Buenos Aires), where they were challenged with live FMDV. Animals were bled immediately before and 7 days after challenge, and their white blood cells and lymphocyte subpopulations were counted. All animals showed a marked neutropenia and eosinophilia, significantly higher in HS than in EO and C groups; both parameters were significantly better in the 2nd assay. Total lymphocyte counts were normal. Lymphocyte subpopulations were assessed by immunofluorescence using monoclonal antibodies: their proportions were normal and did not change during illness in group C. Several factors could have induced the observed eosinophilia and neutropenia: parasites, stress, saponine, others.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

[Use of anti-foot-and-mouth disease vaccine in oil adjuvant in young cattle].

A comparative study of the activity of foot-and-mouth disease vaccines, both aqueous- and oil-adjuvanted, was carried out on young bovines from vaccinated mothers. The immunity of these animals against foot-and-mouth disease was controlled after the first vaccination and booster by serology (neutralizing antibody count and immunology virulence testing). After having followed the kinetics of decrease in seroneutralizing antibodies of maternal origin the animals were vaccinated at the age of 11 weeks either with aqueous-adjuvanted or oil-adjuvanted vaccine. A booster dose was given two months later. Blood samples were taken at regular intervals and two virulence tests were made, one 21 days after the first vaccination and the other six months after the booster dose.

Adjuvants, Immunologic↗

Aspects of the persistence of foot-and-mouth disease virus in animals--the carrier problem.

Foot-and-mouth disease virus (FMDV) is a member of the Aphthovirus genus in the Picornaviridae family. Seven distinct serotypes, each including a wide range of variants, have been defined. FMD, affects wild and domesticated ruminants and pigs, is difficult to control and is the major constraint to international trade in livestock and animal products. After the acute stage of infection, FMDV may cause a prolonged, asymptomatic but persistent infection in ruminants. Also, vaccinated or naturally immune animals subsequently exposed to live virus may become persistently infected (the so-called carriers), a situation which can result in export embargoes if vaccination is included in a country's control policy.

Animals↗

Pandemic strain of foot-and-mouth disease virus serotype O.

A particular genetic lineage of foot-and-mouth disease virus (FMDV) serotype O, which we have named the PanAsia strain, was responsible for an explosive pandemic in Asia and extended to parts of Africa and Europe from 1998 to 2001. In 2000 and 2001, this virus strain caused outbreaks in the Republic of Korea, Japan, Russia, Mongolia, South Africa, the United Kingdom, Republic of Ireland, France, and the Netherlands, countries which last experienced FMD outbreaks decades before (ranging from 1934 for Korea to 1984 for the Netherlands). Although the virus has been controlled in all of these normally FMD-free or sporadically infected countries, it appears to be established throughout much of southern Asia, with geographically separated lineages evolving independently. A pandemic such as this is a rare phenomenon but demonstrates the ability of newly emerging FMDV strains to spread rapidly throughout a wide region and invade countries previously free from the disease.

Animals↗

Protective immune response of the capsid precursor polypeptide (P1) of foot and mouth disease virus type 'O' produced in Pichia pastoris.

Foot and mouth disease virus (FMDV) is the aetiological agent of a highly contagious vesicular disease of cloven-hooved animals. The gene coding for the capsid polyprotein (P1) of FMDV from serotype 'O' vaccine strain (O75Madras) was cloned and expressed in yeast Pichia pastoris. The expressed P1 protein was characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Western Blot analysis. Immunisation of Guinea pigs with recombinant P1 induced FMDV type O specific immune response. The humoral response to vaccine was measured by indirect ELISA and a serum neutralisation test (SNT). The Guinea pig sera showed high titres both in ELISA and SNT. Upon challenge with virulent Guinea pig adapted homologous type 'O' virus, the animals showed a protective index of 2.52. This study shows that the yeast expressed FMDV P1 could be a safe vaccine in non-endemic countries and a cost-effective vaccine in endemic countries. This is the first report on the production of FMDV structural proteins in yeast and their application as a vaccine.

Animals↗

Clinical variation in foot and mouth disease: pigs.

In intensively reared pigs, the introduction of foot and mouth disease (FMD) results in severe clinical disease and vesicular lesions in adult and fattening animals, and high mortality in piglets. Vaccination of uninfected herds can assist FMD control and eradication programmes by reducing susceptibility of pigs older than 12 to 14 weeks and providing early protection to piglets through maternal antibody, but once FMD is established on a farm, vaccination alone will not prevent recurrent outbreaks of clinical disease.

Animals↗

Induction of immunity in swine by purified recombinant VP1 of foot-and-mouth disease virus.

VP1, a capsid protein of foot-and-mouth disease virus (FMDV), contains neutralizing epitopes of the virus. Due to its poor water solubility, recombinant Escherichia coli derived VP1 (rVP1) has previously been used mainly in a denatured form and is not well characterized. Here, using SDS to assist protein refolding and then removing SDS with a detergent removing column, we have successfully purified rVP1 in two aqueous-soluble forms, i.e. monomer and dimer. Studies showed that dimerization occurs by an inter-molecular disulfide bond between two cysteine residues at position 187 of each monomer. Heat treatment revealed that rVP1 dimer exhibited a more thermal-stable conformation than the monomeric form. Both monomeric and dimeric rVP1 reacted with anti-FMDV antibodies. Immunization studies demonstrated that vaccination of swine with either forms of rVP1 was effective in generating immune responses and protecting them from viral challenge.

Amino Acid Sequence↗

Application of RNase T1 one- and two-dimensional analyses to the rapid identification of foot-and-mouth disease viruses.

The analysis of several isolates of foot-and-mouth disease virus by RNase T1 fingerprinting of the 32P-labeled RNA is described. It has been shown that use of the 35S induced RNA instead of the virus particle RNA has two advantages. (i) About 40 times more radioactivity is incorporated into the induced RNA. (ii) The RNA can be prepared much more rapidly, thus increasing the value of the technique in rapid diagnosis. One-dimensional maps, in which the RNase T1 oligonucleotides are separated according to size, have been shown to provide a valuable screening method for distinguishing between viruses. Those viruses giving similar one-dimensional maps also gave similar two-dimensional maps. The value of using the length of the polycytidylic acid tract of foot-and-mouth disease virus as a diagnostic tool is also discussed.

Aphthovirus↗

The generation and persistence of genetic variation in foot-and-mouth disease virus.

Genetic variation in foot-and-mouth disease virus (FMDV) is of interest for at least two reasons. First, changes to the genes encoding capsid proteins results in antigenic variation, and affects vaccine efficiency and effectiveness of vaccination programs; second, genetic changes can lead to important insights into the transport of virus between countries, regions, herds, and even possibly individuals. Current estimates of RNA virus mutation rates suggest that an average of about one base mis-incorporation is likely to occur each time a single FMDV genome replicates. This should result in the introduction of every possible 1-step mutation from the progenitor genotype into the viraemia of a single infected animal many times a day. In the absence of purifying selection, a single infected animal should therefore generate a genetically very diverse population of virus.Viral-capsid sequences obtained from infected animals sampled over long-term FMDV epidemics suggest that these genetic changes accrue in a remarkably linear 'clock-like' fashion and at rates of around 1% change per year. While such a rate is generally regarded as quite high, it is actually somewhat lower than one might expect based on the rate at which viral diversity could be generated within a single animal. The difference might be explained in a variety of possible ways: (1) the mutation rate has been overestimated; (2) purifying selection is stronger than predicted; (3) only a restricted subset of excreted virus is actually infectious; (4) infected animals only excrete virus from a small partitioned subset of amplified virus, and that most of the generated viral diversity is unable to exit the animal; or (5) only a small fraction of all infected animals participate in the actual disease-transmission process.

Animals↗

Secretory antibody responses in cattle infected with foot-and-mouth disease virus.

Antibody responses in serum, saliva, nasal secretions, or esophageal-pharyngeal fluid of foot-and-mouth disease virus-infected steers were examined by single radial immunodiffusion and mouse-neutralization tests. In steers infected with type O foot-and-mouth disease virus, high serum antibody titers were detected within 10 days after infection. Antibody was first detected in saliva at 30 days and gradually increased to a plateau at about 90 days. Small amounts of antibody continued to be secreted in saliva and in nasal secretions for at least 6 months. Antibody was not detected in esophageal-pharyngeal fluid. The major antibody activity in secretions was due to secretory immunoglobulin A as revealed by radioimmunoelectrophoresis.

Animals↗

[Preliminary study of the combination of anti-foot-and-mouth disease and anti-brucellosis vaccines].

The results obtained with Brucella B19 strain, used as adjuvant and stimulant in the preparation of hyperimmune anti-foot-and-mouth disease serums on guinea pigs, have led the authors to carry out a series of experiments with a combined anti-foot-and-mouth disease and anti-brucellosis vaccine (strain B 19 Buck and Cotton). The search for neutralizing antibodies for foot-and-mouth disease has been undertaken by different methods. In the search for antibrucellic antibodies reactions such as seroagglutination, fixation of the complement, etc. have been used. The results obtained with combined vaccine are identical with those obtained with each of the monovalent vaccines.

Animals↗

The airborne dispersal of foot-and-mouth disease virus from vaccinated and recovered pigs, cattle and sheep after exposure to infection.

Foot-and-mouth disease virus was detected during two periods in the air of looseboxes which housed susceptible, vaccinated or recovered pigs, cattle or sheep exposed to infection. The first was 30 min to 22 h after exposure and occurred in all animals. The second was two to seven days after exposure and occurred with those susceptible and vaccinated animals which developed clinical lesions, and with vaccinated and recovered pigs and sheep, which did not develop clinical lesions. Vaccination of animals before exposure resulted in less or no virus being detected. The virus during the first period was attributed to virus trapped on the animal during exposure, and the virus during the second period to limited multiplication in the respiratory tract. Control of movement for two weeks after contact with infection is suggested as a means of preventing spread of foot-and-mouth disease in areas that contain vaccinated animals.

Air Microbiology↗

Vaccination against foot-and-mouth disease virus confers complete clinical protection in 7 days and partial protection in 4 days: Use in emergency outbreak response.

Recent outbreaks of foot-and-mouth disease virus (FMDV) demonstrate that this highly contagious viral infection of cloven hoofed animals continues to be a significant economic problem worldwide. Debate about the most effective way to respond to outbreaks of FMDV in disease free countries continues to center on the use of vaccines. In this report, we present data showing that a commercially available, standard dose vaccine formulation can fully protect cattle against direct challenge with the virus in as little as 7 days with no carrier transmission to naïve animals. Cattle challenged 4 days after vaccination have reduced disease severity, no detectable virus in blood and little virus shedding from nasal secretions. These significant effects at 4 days post vaccination, confirmed in two separate trials, support the value of using currently available vaccines as a first line of defense against foot-and-mouth disease (FMD) outbreaks.

Animals↗

Molecular epidemiology of foot-and-mouth disease viruses in the Adamawa province of Cameroon.

Foot-and-mouth disease virus (FMDV) causes a highly contagious viral disease of even-toed ungulates and is one of the most important economic diseases of livestock. Most studies of FMDV are done in countries where control measures are being implemented. In contrast, in areas such as sub-Saharan Africa, where FMDV is endemic and new strains are likely to emerge, there are only sporadic submissions to the World Reference Laboratory, Pirbright, United Kingdom. This paper describes the molecular epidemiology of FMDV in the Adamawa province of Cameroon based on a population sample of cattle herds. Serotypes SAT2 and A were isolated in the cross-sectional study. SAT2 isolates were all similar, with phylogenetic distances of <6%, and were most closely related to published sequences of isolates from Eritrea and Saudi Arabia. Serotype A isolates were more variable, with phylogenetic distances of 0 to 11%, and were most closely related to historic isolates from Cameroon. Use of a population-based sample gives a representative sample of virus diversity and will improve our understanding of the evolution of FMDV and its epidemiology. A supplementary study of pigs passing through the railhead collection yard at Ngaoundere detected a serotype O virus. A third pilot longitudinal study monitored viral persistence in three cattle herds over 12 months, and serotype O and A viruses were recovered from a herd 12 months after it was first recorded as being infected with SAT2 virus. The pig type O isolate was not closely related to that recovered from the cattle, suggesting that the pigs had not introduced the O virus into the cattle herds.

Animals↗

Synthetic peptide vaccines: foot-and-mouth disease virus as a model.

Foot-and-mouth disease virus (FMDV) has been one of the pioneering viral systems in the development of synthetic peptides as vaccines. Protection against FMDV infection is associated with the induction of neutralising antibodies. Therefore, attempts have been made to identify peptides capable of eliciting protective humoral responses. Peptides based on a continuous, immunodominant B cell site on the capsid protein VP1 have been shown to confer limited protection in natural hosts. This probably reflects the difficulties in reproducing the immunogenicity of an entire viral particle by using a much simpler synthetic antigen, due to: (i) the polymorphism of the class II MHC; (ii) the adequate presentation to the immune system of the peptides, and (iii) the difficulties of achieving protection against a highly variable RNA virus, which may favour selection of virus antigenic variants. The improvement of FMD peptide vaccines, and the development of in vitro alternatives to in vivo immunogenic assays require further understanding of the immune mechanisms leading to protection against this important animal virus disease.

Animals↗