History of the control of foot and mouth disease

From the many existing documents on the history of foot and mouth disease, it is possible to describe the practical measures adopted for disease surveillance and control from ancient times until the 20th century.

Surveillance was based on diagnosis or post-mortem examination, and also on knowledge of the conditions under which infection occurred: aetiology, pathogenesis, mode of infection, susceptible species, virulent material, etc. The historical facts are assembled and compared, with comments on each of these points.

Control was based upon the application of isolation, then slaughter or aphtisation, then vaccination. A study of these various procedures makes it possible to compare their efficacy.

Résumé

D'après les nombreux documents existant sur l'histoire de la fièvre aphteuse il est possible de décrire les mesures adoptées pour suivre l'évolution de la maladie et la maîtriser, depuis l'Antiquité jusqu'au XXème siècle.

La surveillance de la maladie était fondée sur le diagnostic clinique ou l'examen des lésions, mais aussi sur la connaissance des condition de l'infection: étiologie, pathogénie, mode de transmission du contage, matières virulentes, etc. Les faits historiques concernant ces différents points sont rassemblés, comparés et commentés.

La maîtrise de la fièvre aphteuse a été assurée soit par des mesures d'isolement, puis d'abattage sanitaire, soit par des opérations d'aphtisation puis de vaccination. L'étude de ces différentes stratégies permet de comparer leur efficacité respective.     

The foot and mouth disease (FMD) epidemic in the United Kingdom 2001

The foot and mouth disease epidemic commenced in February 2001 when diseased pigs were identified in an abattoir. The infection had become widespread in sheep in England and Wales before this discovery. It was decided to eradicate the disease by slaughter rather than use vaccine. The virus was a Pan-Asia O strain that caused few lesions in sheep and this made the identification of infected flocks very difficult leading to a long drawn-out epidemic. Over four million animals were slaughtered in 2000 herds and flocks. The last outbreak was in September.

Résumé

L'épizootie de fièvre aphteuse a commencé en février 2001 quand elle a été identifiée sur des porcs maladies dans un abattoir. L'infection avait beaucoup diffusé auparavant chez le mouton en Angleterre et au pays de Galles. Il a été d'écidé d'éradiquer la maladie par abattage plautôt que par vaccination. Le virus était une souche Pan-Asia de type O, provoquant des lésions limitées chez le mouton, ce qui a rendu trés difficile l'identification des troupeaux infectés et conduit à une longue queue d'épizootie. Plus de quatre millions d'animaux ont été abattus dand 2000 troupeaux. Le dernier foyer a été identifié en Septembre.     

Aspects of emergency vaccination against foot-and-mouth disease

Emergency vaccination is one of several measures which may be deployed to control outbreaks of foot-and-mouth disease. It can be a valuable adjunct to the application of the essential zoosanitary controls which must include rapid diagnosis, tracing, movement control and disinfection and which may also include slaughter of infected and in-contact animals and their safe disposal. Criteria which determine the successful application of emergency vaccination include access to vaccine(s) that (i) contain virus strain(s) of sufficient antigenic relatedness to the outbreak strain(s) (ii) are of the required type of vaccine formulation (iii) have acceptable innocuity and potency (iv) have appropriate availability, including quantity and immediacy of supply and (v) meet considerations of cost. Contingency planning should include provision for emergency vaccination and must address the complex decisions of not only when, where, and how to apply vaccine but also its economic consequences. Computer modelling may be a useful aid to cost benefit and decision support systems in this context. Planning must be detailed and regularly reviewed and should ensure, (i) that the legal and financial aspects are catered for (ii) that any contractual supply agreements are in place (iii) that information is collected and its currency maintained on the species, numbers and whereabouts of susceptible livestock (iv) that vaccination teams are formed and trained (v) that the vaccine cold chain is established and maintained (vi) that supplies of vaccination equipment are held in readiness and (vii) that briefing materials are available to inform the various stakeholders on relevant aspects of emergency vaccination. Knowledge concerning the characteristics and performance of emergency vaccines is summarised and areas identified for further research.     

Action of FAO in the control of foot and mouth disease

This paper describes the role played by FAO in the control of foot and mouth disease. Since 1954 the FAO European Commission for the control of foot-and-mouth disease co-ordinated the regional programme for eradication of FMD in Europe. One of the major achievements of the Commission has been to prevent the introduction and spread of exotic strains of foot and mouth disease into Europe through the Balkans. FAO also supports the activities of the Foot-and-Mouth Disease World Reference Laboratory located in the Institute of Animal Health, Pirbright, UK.

The Infectious Diseases/EMPRES Group of the Animal Health Service, Animal Production and Health Division of FAO, promotes a global approach to the control and eradication of transboundary animal diseases over the world. For foot and mouth disease, the strategy is based on co-ordinated regional programmes. For FAO, no sustainable progress can be achieved in FMD control over the world without addressing and supporting the control of the disease in endemic countries.

Résumé

L'article décrit le rôle joué par la FAO dans la lutte contre la fièvre aphteuse. Depuis 1954, la Commission Européenne de Lutte contre la fièvre aphteuse de la FAO coordonne le programme régional d’éradication en Europe. Un des succès majeur de cette Commission a été de prévenir l'introduction et la diffusion des souches exotiques de virus de la fièvre aphteuse à travers les Balkans. La FAO soutient également les activités du Laboratoire Mondial de référence pour la fièvre aphteuse qui se situe à l'Institut pour la Santé Animale de Pirbright au Royaume Uni.

Le Groupe Maladies Infectieuses/EMPRES du Service de Santé Animale au sein de la Division Production et Santé Animale de la FAO défend une approche globale de lutte et d’éradication des maladies transfrontalières à travers le monde. Pour la fièvre aphteuse, la stratégie est basée sur une approche régionale coordonnée. Pour la FAO, aucun progres significatif durable ne peut être obtenu dans la lutte contre la fièvre aphteuse à travers le monde sans que la question de la lutte dans les pays où la maladie est endémique ne soit prise en compte et soutenue.     

Epidemiological basis useful for the control of foot-and-mouth disease

Although known for many years, foot-and-mouth disease is still able to represent a real threat to many farming economies in the world. The recent 2001 Western European epizootics linked to O PanAsia virus strain can illustrate the fact that many questions are still unanswered in the field of foot-and-mouth epidemiology. It also demonstrates that the increase in international trade, including livestock, animal products and animal food, means an increase in the probability of transmitting, through the same way, some animal diseases, foot-and-mouth included. In our economies, a rapid identification of the virus and a fast elimination of infected, contaminated and even some contact animals are still the key factors to react in front of such a disease.

Résumé

Bien que connue depuis des années, la fièvre aphteuse représente toujours une menace réelle pour beaucoup d'économies agricoles de la planète. L'épisode récent de 2001 en Europe Occidentale, lié au virus O PanAsia, illustre le fait que de nombreuses questions sont toujours sans réponse au niveau de l'épidémiologie de la maladie. Cet épisode démontre aussi que le développement du commerce international des animaux et des produits animaux se traduit par une augmentation de la probabilité de transmettre, de la même façon, diverses maladies animales dont la fièvre aphteuse. Dans nos économies, une identification rapide du virus, suivie d'une élimination précoce des animaux malades, contaminés, voire contact, restent les clefs d'une maîtrise de la fièvre aphteuse.     

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.

Résumé

Les différentes méthodes de diagnostic de la FA (fièvre aphteuse) sont exposées. Le recours au laboratoire est indispensable; la seule présence de signes cliniques ne permettant pas d'établir le diagnostic. Le virus peut être mis en évidence par isolement en culture cellulaire, par le test de fixation du complément, l'ELISA ou la technique récente de polymérisation en chaine (PCR). La recherche des anticorps est aussi reconnue comme outil diagnostic. Le test de séroneutralisation a été supplanté par l'ELISA et la réponse anticorps contre certaines des protéines virales non structurales permet la différenciation entre troupeaux vaccinés et troupeaux infectés. Des tests plus rapides et précis, la possibilité de détecter le virus lors de la phase préclinique seraient d'utilité certaine.     

Malignant catarrhal fever virus specific secretory IgA in nasal secretions of wildebeest calves

Wildebeest IgA was isolated from nasal secretions and precolostrum. It was indentified by cross-reaction with anti-human and anti-bovine IgA sera.

Nasal secretions collected from wildebeest calves over 3 months old had malignant catarrhal fever virus neutralizing antibody activity. They also contained specific IgA to the virus as detected by indirect immunofluorescence. It is suggested that production of malignant catarrhal fever virus specific IgA in the nasal cavity, contributes to the elimination and cassation of the virus shed in the nasal secretions of wildebeest calves over 3 months. old.     

Dengue hemorrhagic fever with special emphasis on immunopathogenesis

Dengue virus infections are a serious cause of morbidity and mortality in most tropical and subtropical areas of the world; Southeast and South Asia, Central and South America, and the Caribbean. Dengue virus infection can be asymptomatic or causes two forms of illness, dengue fever (DF) and dengue hemorrhagic fever (DHF), which is the severe form of dengue illness and often fatal. Pathogenesis of DHF has been analyzed, and two mechanisms are considered to be responsible. These include dengue serotype cross-reactive immune responses and virulence of the virus. The immunopathological mechanisms include a complex series of immune responses. Rapid increase in the levels of cytokines, especially TNF-, and chemical mediators play a key role in inducing unique clinical manifestations of DHF such as plasma leakage, shock, and hemorrhagic manifestations. It is understood that the process is initiated by infection with a virulent dengue virus, often in the presence of antibodies that enhance dengue virus infection in secondary infection, and then triggered by rapidly elevated cytokines and chemical mediators that were produced by intense immune activation. However, complete understanding of the entire pathological mechanism is far from complete, and further studies are still needed.     

The duration of the foot-and-mouth disease virus carrier state in African buffalo (i) in the individual animal and (ii) in a free-living herd

The maintenance of a virus depends on a number of factors, including the duration of infectivity and the size of the available host population. In this work, foot-and-mouth disease virus was shown to persist in individual African buffalo (Syncerus caffer) for up to at least five years; thus, the duration of infectivity is more than adequate to cover the normal periods between calving peaks. In a small isolated free-living population which varied from 30 to 100 buffalo, two immunological types of foot-and-mouth disease virus were maintained for at least 24 years and through several generations.     

The pathogenesis and immunology of bluetongue virus infection of ruminants

Bluetongue (BLU) virus is transmitted from infected to susceptible ruminants by hematophagous vector midges (Culicoides species). Cattle are important reservoir hosts of the virus because infection typically is asymptomatic and characterized by prolonged cell associated viremia, and because at least some species of insect vector preferentially feed on cattle. Interaction of BLU virus with the cell membrane of erythrocytes in infected cattle likely facilitates both prolonged viremia as well as infection of the insect vector. BLU disease is most common in sheep and some wildlife species. A variety of host, agent and environmental factors clearly can influence expression of disease in these species. The pathogenesis of BLU virus infection of cattle and sheep is remarkably similar, thus the basis for expression of disease in sheep but not cattle remains to be firmly established. Some difference in susceptibility of endothelial cells to infection in the two species is one potential explanation.

Ruminants develop a variety of antiviral responses after BLU virus infection. Antibodies to outer capsid protein VP2 are responsible for virus neutralization, and confer resistance to reinfection with the homologous serotype of BLU virus. Antibodies to epitopes on proteins which are common to all viruses of the BLU serogroup form the basis of current diagnostic serologic tests. Cell mediated responses have been incompletely characterized, in part because BLU virus replicates within dividing lymphocytes and virus-mediated cytolysis inhibits in vitro blastogenesis. Immunological competence of ruminants to BLU virus arises prior to midgestation, and suggestions that persistent immune tolerant BLU virus infection occurs after in utero exposure of cattle have not been substantiated and are not consistent with recent findings.     

Ring vaccination against foot-and-mouth disease

The study of the available information, notably after the epizootic of foot-and-mouth disease (FMD) which raged in Western Europe in 2001, shows that, in the current conditions of the international sanitary rules relative to this disease, in a FMD-free country of Western Europe accidentally infected, ring vaccination is a solution which, with regard to preventive slaughter, contains more inconveniences (notably economic) than advantages. The appeal to ring vaccination would be interesting only as far as the international sanitary rules would be modified by taking into account the results expected from the coordinated use of highly purified vaccines and differential research kits (vaccine-linked versus infection-linked antibodies). Propositions are this way made.

Résumé

L'étude des informations disponibles, notamment après l'épizootie de fièvre aphteuse qui a sévi en Europe occidentale en 2001, montre que, dans les conditions actuelles de la réglementation sanitaire internationale relative à cette maladie, dans un pays indemne d'Europe occidentale accidentellement infecté, la vaccination périfocale est une solution qui, par rapport à l'abattage préventif, comporte davantage d'inconvénients (notamment économiques) que d'avantages. Le recours à la vaccination périfocale ne serait intéressant que dans la mesure où la réglementation sanitaire internationale serait modifiée en prenant en compte les résultats attendus de l'emploi coordonné de vaccins hautement purifiés et de coffrets de dépistage différentiel (anticorps post infection/anticorps post vaccinaux). Des propositions sont faites en ce sens.     

Neutralising antibodies to wildebeest-derived malignant catarrhal fever virus in African wildlife

A total of 2,722 sera collected between 1963 and 1983, from 43 different species of wildlife in 11 African countries was examined for neutralising antibodies against the wildebeest-derived strain of malignant catarrhal fever (MCF) virus. Antibodies were demonstrated in 10 species of Bovidae which included eight species from the sub-family Hippotraginae and one species each from Bovinae and Antilopinae. Neutralising antibodies were also recorded in hippopotamus. It is suggested that the high prevalence of antibodies recorded in sera from waterbuck and reedbuck indicate infection with MCF. However, titres in other species may be due to antigenically related viruses.     

Effect of malignant catarrhal fever virus infection on the immune response of rabbits to sheep red blood cells

Rabbits infected with African Malignant catarrhal fever virus mounted a depressed antibody response to sheep red blood cells compared to the antibody response of uninfected rabbits. Immunodepression was observed in rabbits immunised 0, 3, 5, 7 and 10 days after infection. Antibody response was not depressed in the rabbits immunised 1 day after infection. Despite the depressed antibody response to SRBC, the rabbits died with rising virus neutralising antibody to the virus. The possible causes of the immunodepression are discussed.     

Powder and particle-mediated approaches for delivery of DNA and protein vaccines into the epidermis

The epidermis of the skin is both a sensitive immune organ and a practical target site for vaccine administration. However, administration of vaccines into the epidermis is difficult to achieve using conventional vaccine delivery methods employing a needle and syringe. A needle-free vaccine delivery system has been developed that efficiently delivers powdered or particulate DNA and protein vaccines into the epidermal tissue. The delivery system can be used to directly transfect antigen presenting cells (APCs) by formulating DNA or protein vaccines onto gold particles (particle-mediated immunization). Antigen can be directly presented to the immune system by the transfected APCs. Antigen can also be expressed and secreted by transfected keratinocytes and picked up by resident APCs through the exogenous antigen presentation pathway. Alternatively, protein antigens can be formulated into a powder and delivered into the extracellular environment where they are picked up by APCs (epidermal powder immunization). Using any of these formulations, epidermal immunization offers the advantage of efficiently delivering vaccines into the APC-rich epidermis. Recent studies demonstrate that epidermal vaccine delivery induces humoral, cellular, and protective immune responses against infectious diseases in both laboratory animals and man.     

Detergent solubilised bovine viral diarrhea virus elicits a similar immune response as the inactivated virus

The immune response to two detergent solubilised preparations of Bovine Viral Diarrhea Virus (BVDV) proteins were compared with the response to a chemically inactivated BVDV preparation. The antibody titres were measured with the standard immunofluorescence assay and with a newly developed enzyme linked immunosorbent assay (ELISA). The range of viral protein specificity of the antibodies was compared using SDS-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Western blot analysis. The results clearly demonstrate that the detergent solubilised viral proteins are equally as effective immunogens as the killed BVDV vaccine both in terms of antibody titers and specificity.     

Effects of pseudorabies virus infection upon cytotoxicity and antiviral activities of porcine alveolar macrophages

Alveolar macrophages (AM) infected with Pseudorabies virus (PRV) were compared to noninfected AM for cytotoxicity against foreign or transformed cells and production of interferon (IFN). Five PRV strains were used to infect AM including strains that are known to be highly virulent for pigs, i.e. strain 4892 and strain S-62 as well as strains that are regarded as mild or nonvirulent, i.e. BUK and Bartha. The multiplicity of infection ranged from 0.005 to 0.05 TCID₅₀/cell. The target cells in the cytotoxicity assays were either chicken red blood cells, PRV-infected vero cells, or human myeloblastoma cells (K562 cell line). For the producton of IFN, AM cultures were treated with polyinosinic: polycytidylic acid (Poly I:C) diluted in tissue culture media at a concentration of 5 μg/10⁶ cells. Culture supernatants were collected at various times poststimulation and tested for antiviral activity using the Vesicular Stomatitis Virus replication inhibition test. Swine AM were able to lyse chicken red blood cells in an antibody-independent way but not in an antibody-dependent way, whereas lysis of PRV-infected vero cells was accomplished both ways. The cytotoxicity against chicken red blood cells was reduced in the PRV-infected AM as compared to noninfected cells, particularly in AM infected with virulent PRV strains. Specific ⁵¹Cr release values for AM infected with S-62 and 4892 strains were 14 and 19, while the noninfected AM had values of 36. Similarly, in the antibody-dependent cytotoxicity assay against PRV-infected vero cells there was no activity of AM against K562 cells. The production of IFN was readily stimulated with Poly I:C. The optimal time for supernatant collection was between 12 and 16h poststimulation. The antiviral activity was abrogated by treatment of the supernatant with antiserum against human leukocyte IFN; it was therefore considered to be due to interferon-alpha (IFN) released from the macrophages. The antiviral activity present in supernatants of PRV-infected AM was reduced compared to noninfected AM. The difference between AM cultures infected with virulent strains of PRV and noninfected AM cultures was statistically significant at P 0.025. The results provide support to the premise that the role of AM in lung defense can be compromised by PRV infection.     

The influence of normal guinea-pig serum and tissue culture assay system on foot-and-mouth disease virus neutralisation

The inclusion of normal guinea-pig serum in neutralisation reactions involving foot-and-mouth disease virus (FMDV) increased the neutralisation titre and rate of neutralisation by guinea-pig antiserum derived from animals convalescent from FMDV. Such inclusion had little or no effect on neutralisation involving guinea-pig antiserum collected early in infection or early or convalescent bovine antisera. Higher neutralisation titres and more rapid neutralisation were found from assay in bovine thyroid cells than in IB-RS-2 cells. Not all the increase in neutralising activity was removed by heating at 56 degrees C, indicating that other factors in addition to complement were responsible. In some tests a virus fraction resisting neutralisation was found and, when rabbit anti-guinea-pig gamma-globulin was added, an increase in neutralisation resulted, suggesting that most of the persistent virus fraction was due to the presence of infective virus-antibody complexes.     

Association of foot-and-mouth disease virus induced RNA polymerase with host cell organelles

The localization of foot-and-mouth disease viral-induced RNA polymerase has been determined in situ and in partially fractionated cell components by using polymerase antisera tagged with either peroxidase or ferritin. Electron microscopic examination revealed the polymerase to be heavily concentrated on membranes of the smooth membranous vacuoles (SMV) which are newly formed during infection and which were previously shown to be the site where newly synthesized viral RNA appeared. Polymerase antigen was also seen to be associated with the endoplasmic reticulum (ER), the assumed site of original synthesis, and to a lesser extent with mitochondria and the Golgi apparatus. There was no significant polymerase attachment to nuclear and plasma membranes.     

Isolation and biological properties of virulent subpopulations from lentogenic Newcastle disease virus strains

From each of two lentogenic Newcastle disease virus (NDV) strains of the type LaSota and Hitchner B1 a virulent subpopulation could be obtained. The two subpopulations were—in comparison to the two parent viruses—more resistant to the lipid solvent chloroform and more stable against thermal degradation. Also, the glycoproteins haemagglutinin and F (fusion) were more stable against thermal inactivation. Electron microscopic observations revealed in terms of size and morphology all of the characteristics of NDV. Both subpopulations possessed, however, the same elution kinetics as their respective parent strains. The intracerebral and intravenous pathogenicity indices as well as the mean death times of the two subpopulations allow to classify these viruses as virulent Newcastle disease viruses.     

The infrequency of transmission of herpesviruses between humans and animals; postulation of an unrecognised protective host mechanism

The infrequency of natural transmission of herpesviruses between humans and animals is surprising as there is extensive contact between humans and non-human species with unequivocal evidence that host cells from non-susceptible species will support replication of herpesviruses which do not seem to naturally infect that species. This review examines natural cross-infections between human and other species and suggests that, firstly, it is possible that humans and animals do become asymptomatically or symptomatically cross-infected from other species, but the infection is not diagnosed or not diagnosable by conventional methods; secondly, an as yet unidentified novel mechanism(s) may operate to prevent infection using chemical, electrical or as yet unidentified pathways and may even be ‘switched on’ by exposure to the virus.