Foot-and-mouth Disease Control Strategies Research Articles

One world--one health: the threat of emerging swine diseases. An Asian perspective.

SummaryOwing to the expanding globalization, the trans‐boundary spread of an epizootic can easily result from uncontrolled animal movements and human traffic. Foot and mouth disease (FMD) is a major trans‐boundary disease in most Asian countries. Its sporadic re‐emergence suggests that collaborative FMD control strategies should be uniformly implemented in endemic countries to ensure the overall national herd vaccination coverage, biocontainment when outbreaks occur, and strict biosecurity control of animal movement between countries. Sustained commitments from governments, cooperative diplomatic relationships, and public awareness campaigns are critical to FMD control, to ensure collaboration among veterinarians, traders and farmers throughout Southeast Asia (SEA). Recently, highly pathogenic porcine reproductive and respiratory syndrome (HP‐PRRS) and porcine epidemic diarrhoea (PED) spread from China to Southeast Asian countries, causing major economic losses. Foot and mouth disease, HP‐PRRS, and PED currently remain endemic and may continue to sporadically re‐emerge, owing to inadequate public health management and/or biosecurity failures. Therefore, the risk factors must be identified to better understand the epidemiology of these diseases in an effort to develop effective control measures. International coordination through the establishment of a collaborative network supported by the World Organization for Animal Health (OIE) and the Food and Agriculture Organization (FAO) should be implemented to prevent trans‐boundary transmission among countries. This review discusses trans‐boundary swine diseases of particular importance to SEA, including FMD, HP‐PRRS and PED, with a primary focus on major factors contributing to the spread of these diseases and important control measures, reflecting the impact of globalization on disease control and surveillance.

Combining livestock trade patterns with phylogenetics to help understand the spread of foot and mouth disease in sub-Saharan Africa, the Middle East and Southeast Asia

International trade in animals and their products is recognised as a primary determinant of the global epidemiology of transboundary diseases such as foot and mouth disease (FMD). As well as causing serious production losses, FMD is highly contagious, being transmitted through multiple routes and hosts, which makes it one of the most important diseases affecting trade in livestock. Its occurrence has dramatic consequences for the agricultural economy of a normally disease-free country, as well as for the livelihoods and income generation of developing countries where the disease continues to be endemic. In the dynamic of FMD virus (FMDV) dispersal across the globe, phylogenetic inference from molecular sequences of isolated viruses makes a significant contribution to investigating the evolutionary and spatial pathways underlying the source of FMD epidemics. Matching data on livestock movement with molecular epidemiology can enhance our fundamental understanding when reconstructing the spread of the virus between geographical regions, which is essential for the development of FMD control strategies worldwide. This paper reviews the global situation of FMD in the last ten years, combining phylogenetic insights with information on livestock production systems and international trade to analyse the epidemiological dynamics of FMD and the sources of FMDV introductions at a regional level in sub-Saharan Africa, the Middle East and Southeast Asia.

Antiviral activity of bovine type III interferon against foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is one of the most serious threats to the livestock industry. Despite the availability of a vaccine, recent outbreaks in disease-free countries have demonstrated that development of novel FMD control strategies is imperative. Here we report the identification and characterization of bovine (bo) interferon lambda 3 (IFN-λ3), a member of the type III IFN family. Expression of boIFN-λ3 using a replication-defective human adenovirus type 5 vector (Ad5-boIFN-λ3) yielded a glycosylated secreted protein with antiviral activity against FMD virus (FMDV) and vesicular stomatitis virus in bovine cell culture. Inoculation of cattle with Ad5-boIFN-λ3 induced systemic antiviral activity and up-regulation of IFN stimulated gene expression in multiple tissues susceptible to FMDV infection. Our results demonstrate that the type III IFN family is conserved in bovines and boIFN-λ3 has potential for further development as a biotherapeutic candidate to inhibit FMDV or other viruses in cattle.

Molecular Characterization of Foot-and-Mouth Disease Virus: Implications for Disease Control in Bangladesh

Foot-and-mouth disease (FMD) is endemic in Bangladesh, and to implement an effective FMD control programme, it is essential to understand the complex epidemiology of the disease. Here, we report on the characterization of FMD virus (FMDV) recovered from FMD outbreaks in Bangladesh in late 2009. All isolated viruses belonged to the FMDV serotype O. The phylogenetic reconstruction showed that all isolates belonged to the Middle East-South Asia (ME-SA) topotype, but fell into two distinct sublineages, one named Ind-2001 (the other has not been named). Within both sublineages, the 2009 Bangladesh isolates were most closely related to viruses from Nepal collected during 2008 and 2009. Additionally, both sublineages contained older viruses from India collected in 2000 and 2001. In South Asia, there is extensive cross-border cattle movement from Nepal and India to Bangladesh. Both these findings have implications for the control of FMD in Bangladesh. Because of the porous borders, a regional FMD control strategy should be developed. Further, animal identification and monitoring animal movements are necessary to identify the cross-border movements and market chain interactions of ruminants, leading to improved border and movement controls. Additionally, a vaccination strategy should be developed with the initial objective of protecting small-scale dairy herds from disease. For any successful FMD control programme, long-term Government commitment and adequate resources are necessary. A sustainable programme will also need farmer education, commitment and financial contributions.

Experimental evaluation of foot-and-mouth disease vaccines for emergency use in ruminants and pigs: a review

Changes to foot-and-mouth disease (FMD) control policies since 2001 mean that emergency vaccination must be considered more readily as a control measure in the future. Since field application of vaccine for emergency use has only rarely been applied, the effectiveness of single dose administration, as a control measure in an outbreak situation, is poorly understood. In this review we consider all the available experimental data from studies utilizing either experimental or readily available, commercially produced vaccines, in order to assess their likely effectiveness as an additional means of controlling FMD transmission and spread in an emergency. Overall it is concluded that such vaccines offer an additional and valuable means of FMD control for both ruminants and pigs. They are able to reduce clinical disease, sub-clinical infection and excretion and onward transmission of virus. However, to be most effective, vaccination should be rapidly applied to give maximum opportunity for immunity to develop. We also identify areas for future research and emphasize the importance of vaccine efficacy studies in providing data for models that can help to predict the efficacy of differing FMD control strategies.

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.

Unapparent foot and mouth disease infection (sub-clinical infections and carriers): implications for control.

Unlike animals which are carriers of foot and mouth disease (FMD), sub-clinically infected animals may be highly contagious. The implications of sub-clinical infections for the control of FMD are serious because such animals are likely to disseminate the disease when in contact with susceptible livestock. Recent dissemination of FMD virus (FMDV) in Europe shows that sub-clinically infected animals render trade in animals or animal products a potential risk for importing countries. This clearly demonstrates that the paradigm 'free of FMD without vaccination' is not synonymous with 'risk-free'. The risk of introduction of subclinical FMD into FMD-free countries may increase significantly, with the occurrence of large susceptible animal populations, changed agricultural practices, expansion of trade in live animals and animal movements, increased trade in animal products and greater mobility of people. Such changes in circumstances require that national and international authorities remain continuously vigilant to determine any altered risk for importation of FMD. A few historical reports and some recent observations in southern Africa indicate the possibility of dissemination of FMD by bovine carriers into herds of susceptible cattle. These reports have greatly influenced FMD trade policies and thus, FMD control and eradication strategies. However, other field evidence does not support this claim and several controlled experiments were unable to show that carriers are able to initiate disease. When millions of cattle were systematically vaccinated with good quality vaccines, FMD disappeared in spite of a large sentinel population in the form of calves and unvaccinated sheep and pigs. A low number of carriers most likely persisted, but they did not hamper the eradication of the disease. Vaccination policies and trade regulation must be based on risk assessments taking these factors into consideration.

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.

A farming perspective on the 2001 foot and mouth disease epidemic in the United Kingdom.

The outbreak of foot and mouth disease (FMD) that occurred in the United Kingdom (UK) in 2001 was the single largest epidemic of FMD the world had ever experienced. This outbreak raises important issues about future FMD control strategies, including the use of vaccination. The outbreak has also stimulated a wider debate in the UK on the role and direction of agriculture. The author presents the views of the National Farmers' Union of England and Wales on the handling of the outbreak by the UK Government and summarises some of the key lessons to be learned from a farming perspective.

Serological evidence of FMD subclinical infection in sheep population during the 1999 epidemic in Morocco

During 1999, 11 outbreaks of foot and mouth disease (FMD) were declared in the east and central part of Morocco. All the FMD clinical cases reported were cattle. In order to analyse the serological status of sheep from the FMD outbreak areas, 598 sheep sera were tested using a liquid-phase blocking ELISA (LPBE) to detect antibodies against FMDV structural proteins. The study confirmed the presence of FMDV specific antibodies in 77 clinically normal sheep, indicating that unrecognised FMDV-infected sheep could represent a potential risk of FMD dissemination in Morocco. Subsequently, sera from flocks of sheep that had been exposed to FMD outbreaks were assayed by an indirect ELISA using the recombinant FMDV non-structural protein 3ABC expressed in E. coli to evaluate the potential use of this serological test in future epidemiological studies and the development of FMD control strategies. The results indicated that the 3ABC-ELISA was able to detect antibodies indicative of infection with FMDV in asymptomatic sheep in field conditions.