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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 The virus neutralization test has been replaced by ELISA and the antibody response to some viral non-structural proteins allows to discriminate between vaccinated and infected animals on a herd basis.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.

Agglutination Tests↗

[An epidemic of hand, foot and mouth disease].

Five patients with hand-, foot- and mouth disease, caused by infection with Coxsackievirus type A16, are described in an epidemic outbreak of this disease. Hand-, foot- and mouth disease, is characterized by a most distinctive enanthem-exanthemcomplex. In 65% of the cases a vesiculopapular exanthem is noted. Most cases are described in epidemic outbreaks. Although the vast majority of occurrences of the disease have been due to Coxsackie A16 viral infections, occasionally Coxsackie A5, A10 and enterovirus 71, seldom Coxsackievirus B1 or B3, have been etiologically incriminated. In this article attention is paid to the clinical characteristics, the epidemiology and the differential diagnostic aspects of hand-, foot- and mouth disease.

Child, Preschool↗

Past and present vaccine development strategies for the control of foot-and-mouth disease.

Foot-and-mouth disease (FMD) virus (FMDV) was the first animal virus to be identified. Since then, it has become a model system in animal virology and more information has been obtained about FMDV. The disease causes heavy economic crises in enzootic countries both due to loss of animal health and productivity. The only way of its control in an enzootic area is strict vaccination and restricted animal movement. The first experimental vaccine against FMD was made in 1925 using formaldehyde inactivation of cattle tongue infected with the virus and this approach remained the basic one until late 1940s. Antigenic plurality and continuous co-circulation of different serotypes in a given geographical region and persistence of virus in infected or vaccinated animals make the disease very difficult to control. The latter is solely based upon the application of isolation, slaughter or aphtisation, and vaccination. With the advent of recombinant DNA technology, recombinant protein and/or DNA-based vaccines are being tested in various heterologous systems for development of FMD vaccines. The subunit vaccines, synthetic peptide vaccines, DNA vaccines, cytokine-enhanced DNA vaccines, recombinant empty capsid vaccines, chimeric viral vaccines, genetically engineered attenuated vaccines, recombinant viral vector vaccines, self-replicating genetic vaccines and transgenic plants with expressed FMDV proteins represent the present vaccine development strategies for control of FMD.

Animals↗

Evolution of foot-and-mouth disease virus.

Foot-and-mouth disease virus evolution is strongly influenced by high mutation rates and a quasispecies dynamics. Mutant swarms are subjected to positive selection, negative selection and random drift of genomes. Adaptation is the result of selective amplification of subpopulations of genomes. The extent of adaptation to a given environment is quantified by a relative fitness value. Fitness values depend on the virus and its physical and biological environment. Generally, infections involving large population passages result in fitness gain and population bottlenecks lead to fitness loss. Very different types of mutations tend to accumulate in the foot-and-mouth disease virus (FMDV) genome depending on the virus population size during replication. Quasispecies dynamics predict higher probability of success of antiviral strategies based on multivalent vaccines and combination therapy, and this has been supported by clinical and veterinary practice. Quasispecies suggest also new antiviral strategies based on virus entry into error catastrophe, and such procedures are under investigation. Studies with FMDV have contributed to the understanding of quasispecies dynamics and some of its biological implications.

Amino Acid Sequence↗

Developments in diagnostic techniques for differentiating infection from vaccination in foot-and-mouth disease.

Foot-and-mouth disease (FMD) is a highly contagious and economically significant disease of cattle, pigs, sheep, goats and wild ruminant species. The FMD virus genome encodes a unique polyprotein from which the different viral polypeptides are cleaved by viral proteases, including eight different non-structural proteins (NSPs). Both structural and non-structural antigens induce the production of antibodies in infected animals. In contrast, vaccinated animals which have not been exposed to replicating virus will develop antibodies only to the viral antigens in the inactivated material. Vaccination against FMD is a key element in the control of the disease in addition to slaughter and movement restrictions. However, countries that vaccinate in the event of an outbreak will have to re-establish their FMD free status to the satisfaction of their trading partners. Because currently available vaccines stimulate the production of antibodies indistinguishable from those produced by infected animals in response to live virus and because vaccinated animals can be infected and become carriers of FMD virus, efforts have been made to develop diagnostic test that can differentiate vaccinated animals from those that are convalescent and from those that have been vaccinated and become carriers following subsequent contact with live virus. Currently the detection of antibodies to non-structural protein's (NSPs) is the preferred diagnostic method to distinguish virus infected, carrier, animals from vaccinated animals. However this is currently only possible at the herd level because of the great variability in the initiation, specificity and duration of the immune response in individual animals to the NSPs shown in many studies. Considerable effort and attention is now being directed toward the development of new methods and techniques for the rapid and accurate detection of anti-NSP antibodies, harmonization and standardization of current diagnostic techniques, as well as the production of defined reagents.

Animals↗

Passive immunization of guinea pigs with llama single-domain antibody fragments against foot-and-mouth disease.

Foot-and-mouth disease (FMD) is a highly contagious disease that occasionally causes outbreaks in Europe. There is a need for therapies that provide rapid protection against FMD in outbreak situations. We aim to provide such rapid protection by passive immunization with llama single-domain antibody fragments (VHHs). Twenty-four VHHs binding serotype O FMDV in vitro were isolated from immunized llamas by phage display and expressed in bakers yeast for further characterization. They recognized four functionally independent antigenic sites. Six strongly FMDV neutralizing VHHs bound to a peptide representing the GH-loop of viral protein 1 known to be involved in binding to the cellular receptor of FMDV. Clone M8, recognizing this antigenic site, and clone M23, recognizing another antigenic site, showed synergistic in vitro virus neutralization. Three FMDV specific VHHs were PEGylated in order to decrease their rapid blood clearance and thus enable in vivo guinea pig protection experiments. Passive immunization with individual VHHs showed no protection, but a mixture of M8 and M23 showed partial transient protection. The protection afforded by these VHHs was however low as compared to the complete protection afforded by convalescent guinea pig serum. In contrast, these VHHs showed far more efficient in vitro FMDV neutralization than convalescent guinea pig serum. This lack of correlation between in vitro neutralization and in vivo protection lends further credence to the notion that opsonophagocytosis of FMDV is important for protection in vivo.

Amino Acid Sequence↗

Adenovirus-mediated type I interferon expression delays and reduces disease signs in cattle challenged with foot-and-mouth disease virus.

Foot-and-mouth disease (FMD) is an economically important disease of livestock. Eliminating FMD outbreaks in previously disease-free countries often relies on restriction of animal movement and massive slaughter of infected and in-contact susceptible animals. To develop a more effective and humane FMD control strategy, we explored the possibility of using type I interferon (IFN-alpha/beta) as a novel anti-FMD agent. We have demonstrated previously that swine inoculated with replication-defective human adenovirus type 5 (Ad5) vector expressing porcine IFN-alpha (Ad5-PoIFN-alpha) were completely protected from FMD virus (FMDV) challenge. To extend this approach to bovines, we constructed Ad5 vectors that express bovine IFN-alpha or IFN-beta (Ad5-BoIFN-alpha and Ad5-BoIFN-beta). Cells infected with these viruses produced high levels of biologically active BoIFN-alpha/beta, but despite expression in vitro, no detectable IFN-induced biologic activity was found in cattle inoculated with Ad5-BoIFN-alpha. Because PoIFN-alpha inhibits FMDV replication in bovine cells, we evaluated the potential use of PoIFN-alpha against FMD in cattle. In cattle inoculated with Ad5-PoIFN-alpha, the appearance of vesicles was delayed after challenge with FMDV and disease was less severe than in control animals. One Ad5-PoIFN-alpha-inoculated animal never developed clinical disease. Similarly, although all the Ad5-PoIFN-alpha-inoculated animals developed viremia, it was delayed for 1 day as compared with the control group. These results suggest that in vivo expression of PoIFN-alpha partially protected cattle from FMD.

Adenoviridae↗

A vesiculo-bullous disease in pigs resembling foot and mouth disease. I. Field cases.

Eleven incidents of bullae and vesicles on the snouts and less frequently the feet of white-skinned pigs on seven farms are described. Bullous and vesicular lesions up to 5 cm in diameter and containing clotted gelatinous fluid were located on the dorsal aspect of the snout, behind the flange. Lesions ruptured, became ulcerated, developed scabs and healed within three weeks. There was no transmission to other pigs or ruminants. The condition was associated with contact with green vegetable material containing parsnips (Pastinaca sativa) or celery (Apium graveolens), followed by exposure to periods of extended sunshine. Parsnips and celery are known to contain furocoumarins, potent phototoxic compounds. It is suggested that absorption of furocoumarins on the skin of the snout and feet after contact with parsnips and celery and exposure to ultraviolet light caused the lesions in the cases reported. It is postulated that a similar condition may have been responsible for national foot and mouth disease scares in pigs at Warkworth and Temuka in New Zealand and at Legana in Tasmania.

Journal Article↗

A vesiculo-bullous disease in pigs resembling foot and mouth disease. II. Experimental reproduction of the lesion.

Vesiculo-bullous dermatitis of pigs characterised by presence of vesicles and bullae on the snout and feet of white skinned pigs was reproduced experimentally. Leaves of parsnips (Pastinaca sativa), or celery (Apium graveolens) infected with the fungus Sclerotinia sclerotiorum were fed or rubbed on the snouts and feet of white skinned pigs. Pigs were then exposed to sunlight or to UV light of intensity approximately 212 m W/M2 at a wavelength 340-360 nm for eight hours per day until vesicles developed. All treated pigs developed lesions on the snouts, and less frequently on the feet. Lesions were characterised by the appearance of erythema at 24 hours after treatment. Vesicles developed at 48 hours and became maximal by 72 hours. Pigs treated with plant material without exposure to UV light or exposed to UV light without contact with plant material did not develop lesions. The experimental lesions closely resemble those observed in several field cases in 1984 and 1985 in New Zealand and to lesions present in three well publicized foot and mouth disease scares at Warkworth, and Temuka in New Zealand and Legana in Tasmania.

Journal Article↗

Foot-and-mouth disease virus: biology and prospects for disease control.

Foot-and-mouth disease virus (FMDV) is the causative agent of a disease that constitutes one of the main animal health concerns, as evidenced by the devastating outbreaks that occurred in different areas of the world over the last few years. In this review, we summarise important features of FMDV, aspects of its interactions with cells and hosts as well as current and new strategies for FMD control by vaccination.

Animals↗

Prospects, including time-frames, for improved foot and mouth disease vaccines.

Inactivated foot and mouth disease (FMD) vaccines have been used successfully as part of eradication programmes. However, there are a number of concerns with the use of such vaccines and the recent outbreaks of FMD in disease-free countries have increased the need for improved FMD control strategies. To address this requirement, new generation FMD vaccines are being developed. Currently, one of the most promising of these vaccine candidates utilises an empty viral capsid subunit delivered to animals by a live virus vector. This candidate, a replication-defective recombinant human adenovirus containing the capsid and 3C proteinase coding regions of FMD virus (FMDV), induces an FMDV-specific neutralising antibody response in inoculated animals. Upon challenge with a virulent animal-passaged homologous virus, swine and cattle vaccinated with this recombinant adenovirus are protected from clinical signs of FMD as well as from FMDV replication. One inoculation of a high dose of this vaccine candidate protected swine from challenge as early as seven days after vaccination.

Adenoviruses, Human↗

The epidemiology of foot-and-mouth disease: implications for New Zealand.

Foot-and-mouth disease is an acute, highly communicable disease affecting cloven-hoofed animals, both domesticated and wild. It may well be the most contagious disease known in the animal kingdom. The key features that contribute to this include its ability to gain entry and initiate infection through a variety of sites, the small infective dose, the short incubation period, the release of virus before the onset of clinical signs, the massive quantities of virus excreted from infected animals, its ability to spread large distances due to airborne dispersal, and the persistence of the virus in the environment. These features, plus the ability of the virus to be disseminated through the movements of animals, animal products, people, and plant and equipment makes the disease very difficult to control. New Zealand has never experienced a foot-and-mouth disease epidemic, and the economic consequences of an outbreak would be disastrous, due to the eradication costs, the loss of productivity and the impact on the export of animals and animal products. The smuggling of meat products, embryos or semen into the country are perceived as the most likely ways in which the disease could be introduced. The New Zealand Ministry of Agriculture and Fisheries therefore operates a two-tier system of defense against foot-and-mouth disease. The first tier involves border protection through stringent import controls to prevent the entry of infectious material. If this barrier is breached, an emergency response programme is activated, involving a stamping-out eradication strategy. This paper attempts to draw on overseas historical outbreak experiences and research findings to gain insights into the epidemiology of foot-and-mouth disease as it would relate to New Zealand.

Journal Article↗

The interference by maternally-derived antibody with active immunization of farm animals against foot-and-mouth disease.

Foot-and-mouth disease (FMD) is a highly contagious disease affecting ruminants and pigs. In countries in which control of FMD relies predominantly on vaccination, young stock ingest specific anti-FMD virus antibodies in the colostrum. This maternally-derived antibody (MDA) provides immediate protection against infection with FMD virus, but also interferes with the development of active immunity following vaccination. However, susceptibility to infection precedes the ability to respond to vaccination in the presence of MDA. Currently available vaccines cannot overcome this inhibitory effect of MDA, and protection of young stock can only be provided by their isolation from FMD virus.

Animals↗

[Diagnosis of foot and mouth disease].

Because foot-and-mouth disease has the potential for an explosive spread, instant and reliable diagnosis is of special importance. In this article the clinical examination, types and shipment of samples as well as the current methods of laboratory diagnosis by detection of FMD-virus, antigen, nucleic acid and antibodies are reviewed. Special emphasis is laid on the differentiation between vaccinated and infected animals, in respect to conventional as well as novel vaccines.

Animals↗

Construction and immunogenicity of a recombinant fowlpox virus containing the capsid and 3C protease coding regions of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) is an important pathogen with worldwide economic consequences. Consequently, an important goal is the development of a vaccine that can provide rapid protection while overcoming the potential risk associated with the production of conventional inactivated vaccines. An important secondary feature of the vaccine would be the ability to distinguish vaccinated from infected animals. A recombinant fowlpox virus (vUTAL3CP1) containing FMDV capsid polypeptide and 3C coding regions of O/NY00 was constructed and evaluated for its ability to induce humoral and cellular responses in mice and guinea pigs. In addition, the ability to protect guinea pigs against homologous virus challenge was examined. Mice and guinea pigs were given booster vaccinations twice and once, respectively, and guinea pigs were challenged 20 days after the booster vaccination. Control groups included animals inoculated with commercial vaccine, fowlpox virus or phosphate-buffered saline (PBS). All animals vaccinated with vUTAL3CP1 developed specific anti-FMDV antibody and neutralizing antibody, as well as T lymphocyte proliferation response and CTL cytotoxic activity. Three of four guinea pigs vaccinated with vUTAL3CP1 were completely protected from viral challenge. The results demonstrated the potential of a fowlpox virus-based recombinant FMD vaccine.

3C Viral Proteases↗

Studies of quantitative parameters of virus excretion and transmission in pigs and cattle experimentally infected with foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) can be spread by a variety of mechanisms and the rate of spread, the incubation period and the severity of disease depend on a multitude of parameters, including the strain of virus, the dose received, the route of introduction, the animal species and the husbandry conditions. More knowledge with regard to these parameters is urgently needed to improve resource-efficient disease control. This report describes detailed studies of FMDV load, excretion and transmission in pigs infected with FMDV O UKG 2001, O TAW 1997 and C Noville virus and in cattle infected with the O UKG 2001 virus to facilitate use of a "FMDV load framework" for the assessment of transmission risks. Virus replicated rapidly in pigs and cattle exposed by direct contact. The mean incubation period was around 3-4 days for cattle-to-cattle and 1-3 days for pig-to-pig transmission, depending on the intensity of contact. The results confirmed that a strong relation exists between dose and length of incubation period. Clinical disease was severe in pigs but relatively mild in inoculated cattle; contact infection of cattle appeared to increase the severity of lesions. FMDV RNA was recovered in nasal and mouth swabs from inoculated animals soon after they developed a viraemia and probably reflected the early production and excretion of virus. FMDV RNA in nasal and mouth swabs from contact animals could be detected several days before they showed other signs of infection, indicating the possibility of detecting exposed animals during the incubation period. FMDV RNA could also be detected in swab samples after the viraemic phase. This may have represented background environmental virus that had been trapped in the respiratory tract and mouth. Alternatively, it may have indicated a somewhat slower clearance or half-life of viral RNA or an extended low level of FMDV replication at these sites. The pattern of FMDV RNA concentrations in pigs was closely similar to that in cattle, but the amounts of FMDV RNA were higher.

Animals↗

Development of a novel quantitative real-time RT-PCR assay for the simultaneous detection of all serotypes of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) spreads extremely fast and the need for rapid and robust diagnostic virus detection systems was obvious during the recent European epidemic. Using a novel real-time RT-PCR system based on primer-probe energy transfer (PriProET) we present here an assay targeting the 3D gene of FMDV. The assay was validated for the efficacy to detect all known FMDV serotypes. The test method was linear over a range of at least 7 orders of magnitude and the detection limit was below the equivalent of 10 genomic copies. Analysing recent African probang samples the method was able to detect FMDV in materials from both cattle and buffalo. When compared to traditional virus cultivation the virus detection sensitivity was similar but the RT-PCR method can provide a laboratory result much faster than virus cultivation. The real-time PCR method confirms the identity of the amplicon by melting point analysis for added specificity and at the same time allows the detection of mutations in the probe region. As such, the described new method is suitable for the robust real-time detection of index cases caused by any serotype of FMDV.

Animals↗

Molecular epidemiology of foot-and-mouth disease virus.

Foot-and-mouth disease (FMD) is the most economically important veterinary pathogen due to its highly infectious nature, ability to cause persistent infections and long term effects on the condition and productivity of the many animal species it affects. Countries which have the disease have many trade restrictions placed upon them. In the last 15 years there have been significant advances in the understanding of FMD epidemiology. These have largely been due to the application of the molecular biological techniques of polymerase chain-reaction amplification and nucleotide sequencing. In the World Reference Laboratory for FMD (Pirbright, UK), a large sequence database has been built up. This database has been used to aid in the global tracing of virus movements. It has been possible to genetically group many FMDV's based on their geographic origin and this has led to their being referred to as topotypes. The implications of this are that inter-regional spread of viruses can often be easily recognised and any evolutionary changes which subsequently occur can be monitored. Using these techniques, for the first time, we have been able to unequivocally show the recent pandemic spread of a FMDV type O strain through the whole of Asia and into Africa and Europe. This type of surveillance will become increasingly important as further globalisation of markets occurs. An increased understanding of how FMDV strains move between geographic regions will play a pivotal role in the development of future disease control strategies.

Animals↗