Identification of foot and mouth disease virus carrier and subclinically infected animals and differentiation from vaccinated animals

Countries that are free of foot and mouth disease (FMD) are reluctant to use vaccine in the event of an outbreak because of the difficulties this can cause in re-establishing freedom from FMD status to the satisfaction of trading partners. The problem does not lie in distinguishing between vaccinated and recovered animals as vaccinated animals can be tagged or otherwise marked to show that they have been vaccinated; the difficulty is in identifying vaccinated animals that have had contact with live virus and become carriers. The traditional probang test is not sufficiently sensitive and is labour- and laboratory-intensive, but alternative serological tests such as those for antibodies to non-structural proteins (NSPs), or specific immunoglobulin A (IgA) are also not 100% sensitive. However, these newer tests do provide increased security by reducing the likelihood of trading carrier animals and can be used to help define the limits of an outbreak; the use of vaccine to help control an outbreak of FMD in a previously free country still has significant consequences on trade in FMD susceptible animals and their products.     

Predicting the spread of foot and mouth disease by airborne virus

Foot and mouth disease (FMD) can spread by a variety of mechanisms which, under certain climatic and epidemiological conditions, includes the windborne spread of disease. Recent advances in knowledge of the aerobiological features of FMD are described. The strain of virus and species of infected animal are major determinants of airborne virus emission. Pigs emit most virus, cattle and sheep lesser but similar amounts to each other. Peak excretion of airborne virus by sheep occurs before the clinical phase of disease, whereas with cattle and pigs, it coincides with the development of early clinical disease. The probability of aerogenous infection differs greatly between livestock species. Cattle are the most susceptible, followed by sheep, whereas pigs are very resistant. Computer-based simulation models have been developed to analyse and predict the risk of airborne spread of FMD and have been used successfully during outbreaks to support decision-making. Further research is required to refine and extend the models for operational use.     

Computerization of foot and mouth disease virus strain relationship data

Since 1976 the two dimensional microneutralization test has been adopted in our laboratory as the reference test for foot and mouth disease virus (FMDV) strain differentiation. Large numbers of homologous-heterologous comparisons have been performed and manual storage and retrieval of the data had become cumbersome. The objective of computerization was to provide a databank with fast easy access to enable accurate statistical calculations to be performed on the raw data entries and to simplify the evaluation of statistical and biological significance. The computer system is written in Fortran for an IBM 4341 computer running under the VM/CMS operating system.     

Expression of foot and mouth disease virus antigens in transgenic plants

Owing to its geographical distribution and its highly contagious character, the foot and mouth disease (FMD) virus is responsible for one of the most dreaded of all livestock diseases. The currently-used vaccine is polyvalent and is based on an inactivated virus. Current research on FMD vaccines focuses on the creation of vaccines that are easier and cheaper to produce, and that avoid manipulation of large quantities of virus. The use of transgenic plants to express relevant antigens has been evaluated for the purpose of vaccine production. The authors' working group has taken the FMD virus as a model to evaluate the feasibility of using transgenic plants to express viral antigens and to develop experimental vaccines. The purpose of this paper is to set forth the working group's results in the expression of FMD antigens in transgenic plants.     

Use of vaccination against foot and mouth disease in zoo animals,endangered species and exceptionally valuable animals

A historical review of foot and mouth disease (FMD) in non-domestic species is given and the use of FMD vaccines to protect those species is described. Several non-domestic species are susceptible to FMD. Legislation in many countries, based on the definition of FMD-free status as determined by the Office International des Epizooties (OIE: World organisation for animal health), forms an important barrier against the use of vaccines. National authorities may even feel obliged to slaughter animals of threatened species protected by international agreements during an outbreak of FMD to preserve their FMD-free status. The importance of international breeding programmes for endangered species is forcing the international community to reconsider the role that vaccination against FMD should play in animal health prevention programmes of captive populations. Much research is still required in regard to vaccine types and diagnostic procedures. Species-specific differences in susceptibility to FMD make this a challenging research topic for zoological institutions.     

Vaccination against foot and mouth disease reduces virus transmission in groups of calves

The aim of vaccination during an epidemic of foot and mouth disease (FMD) is not to induce clinical protection, but to reduce virus transmission. Since no quantitative data were available on the effectiveness of vaccination in cattle, we investigated whether a single vaccination against FMD could reduce virus transmission in groups of calves by estimating the reproduction ratio R, i.e. the average number of secondary cases caused by one infectious animal in a susceptible population. We performed two experiments with six groups of either four vaccinated or four non-vaccinated calves each. Vaccination was carried out with O(1) Manisa vaccine. Two weeks after vaccination, two calves per group were inoculated intra-nasally with FMDV field isolate O/NET 2001. The two other calves were contact-exposed to the inoculated calves. Contact infections were observed by clinical inspection, virus isolation and RT-PCR on heparinised blood, oro-pharyngeal fluid and probang samples and antibody response to non-structural proteins. In all six non-vaccinated groups, transmission to contact-exposed calves was recorded; in the vaccinated groups, virus transmission was observed to one contact-exposed calf. In the non-vaccinated groups R(c) was 2.52 and significantly above 1, whereas in the vaccinated groups R(v)=0.18 and significantly below 1, indicating that vaccination may successfully be applied as additional intervention tool to reduce virus transmission in a future epidemic of FMD.     

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.     

A study of antigenic variants of foot and mouth disease virus type A in India between 1977 and 1985

The structural polypeptides of thirty-three field isolates of foot and mouth disease virus (FMDV) collected in India between 1977 and 1985 were analysed by SDS-polyacrylamide gel electrophoresis. They were placed in eleven groups based on their patterns and compared with results of conventional serological (virus neutralisation and complement fixation) tests. Variation occurred in the structural proteins of the viruses isolated between 1977 and 1981; however, the polypeptide patterns of viruses isolated in 1984 and 1985 were identical.     

Future research on foot and mouth disease

The recent outbreaks of foot and mouth disease (FMD) in Argentina, Europe, Japan, the Republic of Korea, South Africa and Uruguay have brought to world attention the devastating effects of the disease in a na?ve population and the social and economic costs of control and eradication. The fact that much still remains unknown about the natural history of FMD virus came as a surprise to some. This paper attempts to identify where research should be directed in order to be better prepared in the future.     

The effect of vaccination on foot and mouth disease virus transmission among dairy cows

The aim of this study was to quantify the effect of a single vaccination of dairy cows on foot and mouth disease virus (FMDV) transmission. To estimate if vaccination could significantly reduce virus transmission, we performed two replicates of a transmission experiment with one group of vaccinated and one group of non-vaccinated dairy cows (ten animals per group). Half of both groups were intranasally inoculated, with FMDV field isolate O/NET2001, and housed with the other half of the group (contact-exposed cows) from the next day onwards. Virus transmission was quantified by estimating the reproduction ratio R, which is the average number of secondary cases caused by one infectious animal. In the non-vaccinated groups all cows became infected and Rnv was significantly above 1. In the vaccinated groups infection was demonstrated in three inoculated cows, and no transmission was observed (Rv was 0, not significantly below 1). Transmission was significantly reduced in the groups of vaccinated cows when compared to the groups of unvaccinated cows. Our findings indicate that after a single vaccination cows are protected against infection of FMD and that most likely no virus transmission will occur within a vaccinated herd.     

The risks posed by the importation of animals vaccinated against foot and mouth disease and products derived from vaccinated animals: a review

The Terrestrial Animal Health Code of the OIE (World organisation for animal health) (the Terrestrial Code) makes recommendations for international movements of live animals and animal products because of a possible generic risk of foot and mouth disease (FMD) for these different commodities. For instance, international movement of vaccinated live animals or products of such animals is restricted due to the possible masking of clinical disease as a result of vaccination and to the perceived risk of persistently infected animals among vaccinated livestock. In addition, bilateral agreements between exporting and importing countries on the importation of animal products can be based on the 'equivalence' of the animal health conditions in both countries, or on formal or informal risk assessments in accordance with the norms and recommendations of the Terrestrial Code. In this regard, an exporting country may be required to prepare a complete and transparent document describing the animal health situation, including the factors required to assess the risk involved. Furthermore, expert committees of importing countries regularly evaluate and verify these conditions in exporting countries. The level of confidence in the information obtained by the expert committee can then be entered into the risk analysis equation. An important FMD risk reduction factor for the importation of animals and animal products is early recognition of the disease at the source of the commodity by alert stakeholders, such as official and private veterinarians and the chain of the livestock industry. This is true for all countries irrespective of their vaccination status. The risk posed by the importation of vaccinated animals becomes negligible when an adequate protocol--in compliance with the norms and recommendations of the Terrestrial Code--is applied. However, recently, export of live animals from countries that do not practise vaccination has also proven to pose a significant risk and the rules governing such transport may have to be reviewed. Disease surveillance, biosecurity at the farm level, traceability and control of the source cattle and slaughterhouse inspections are the main risk reduction measures for meat and meat products from vaccinated cattle. If these animals are slaughtered and processed under good management practice--in accordance with the norms and recommendations of the Terrestrial Code--these products present a negligible risk for the introduction of FMD. Risk reduction by maturation and deboning is an important procedure, but is probably overemphasised. Mechanical contamination of cattle carcasses with 'carrier virus' from the pharyngeal area during slaughter and processing is very unlikely. Risk assessments showed that the importation of milk products from countries or zones that practise vaccination of dairy herds poses a negligible risk. Risk assessments also demonstrated that the importation of bovine embryos from vaccinated cows--in accordance with the norms and recommendations of the Terrestrial Code--poses a negligible risk. Likewise, the risk from the importation of semen from vaccinated bulls is also negligible when an adequate test protocol is applied in accordance with the Terrestrial Code.     

Survey of foot and mouth disease in France

The Foot and Mouth disease is considered a relatively mild disease in susceptible animals but it has a considerable economical impact in France and worldwide due to the huge economical losses that it generates. A system for the prevention of the disease was developed thirty years ago and has since been continuously improved. The current system for the prevention of FMD is based on training and information of all those involved in the surveillance of susceptible animals, over all the national territory, and on the control of imported animals and animal products. This system, developed in close collaboration with the European Commission and the other EU member states, allows control measures to be implemented almost instantaneously, if a case is suspected to avoid spreading of the disease.     

手足口病的三级预防策略

手足口病（HFMD）是由多种肠道病毒引起，以婴幼儿为主要发病人群的一种传染性疾病，具有潜伏期、传播速度快。本文回顾该疾病的传染源、传播途径和易感人群的同时，重点阐述了疫苗研制、健康教育、早期诊断方法、并发症早期发现和处理等三级预防策略的最新研究进展。     

Synthetic peptide vaccines against foot and mouth disease

Synthetic peptide vaccines against food-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.     

Prospects for improved foot and mouth disease vaccines

Improved foot and mouth disease (FMD) vaccines which have increased efficiency and stability are highly desirable. Work which aims to increase the stability of FMD virus particles for vaccine use is described and the use of these particles and of antigenic fragments of the virus for controlled release vaccine products is considered.