The effect of a double-stranded RNA of fungal origin on the development of foot-and-mouth disease in pigs and calves

New approaches to rapidly control foot-and-mouth disease outbreaks

Economically, foot-and-mouth disease is the most important viral-induced livestock disease worldwide. The disease is highly contagious and foot-and-mouth disease virus replicates and spreads extremely rapidly. Recent outbreaks in previously foot-and-mouth disease-free countries and the potential use of foot-and-mouth disease virus by terrorist groups have demonstrated the vulnerability of countries and the need to develop control strategies that can rapidly inhibit or limit spread of the disease. The current vaccine, an inactivated whole-virus preparation, has a number of limitations for use in outbreaks in disease-free countries. This review discusses the potential of the antiviral agent, Type I interferon, to produce rapid protection and proposes a combination strategy of an antiviral agent and a foot-and-mouth disease vaccine to induce both immediate and long-lasting protective responses.

The pathogenesis and diagnosis of foot-and-mouth disease

The pathogenesis of foot-and-mouth disease (FMD) is reviewed, taking account of knowledge gained from field and experimental studies and embracing investigations at the level of the virus, the cell, the organ, the whole animal and the herd or flock. The review also addresses the immune response and the carrier state in FMD. Progress made in understanding the pathogenesis of the disease is highlighted in relation to developments in diagnosis and methods of control.

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.

A review of emergency foot-and-mouth disease (FMD) vaccines

The primary objectives of this paper are to describe emergency foot-and-mouth disease (FMD) vaccines and review literature on emergency vaccine efficacy to protect animals against (1) clinical signs and (2) infection (local virus replication). The reviewed experiments suggest that in cattle, sheep and pigs, the vaccine could be effective in preventing disease within 4-5 days post-vaccination. These studies also suggest that the risk of spreading infection decreases as the interval between vaccine and challenge increases and that vaccination could reduce the amount of virus excreted compared to non-vaccinated animals. We suggest areas of future research to improve our knowledge of emergency vaccines.

Emergency vaccination against foot-and-mouth disease: rate of development of immunity and its implications for the carrier state

Emergency foot-and-mouth disease (FMD) vaccines prepared from antigens held in the International Vaccine Bank at Pirbright were administered to cattle and pigs and the levels of protection were assessed following challenge by contact with infected pigs. Both Al(OH)3/saponin and oil-based cattle vaccines proved to be extremely effective and protected soon after vaccination (4 days postvaccination), whereas the pigs were seldom protected before 21 and 28 days postvaccination, probably due to lower levels of antibody and overwhelming challenge conditions. Early production of cattle occurred in the absence of significant levels of circulating antibody as measured by enzyme-linked immunosorbent assay, a neutralization assay and a passive protection test. A large number of the cattle vaccinated with the O1 Lausanne strain of FMD and subsequently challenged with this virus became persistently infected and there appeared to be a correlation with the time interval between vaccination and challenge. When the same cattle were vaccinated approximately 4 months later with a different strain of FMD, C1 Oberbayern, and challenged with this strain, the number of persistently infected animals was considerably lower. The results are discussed in the context of the use of emergency vaccines to prevent the dissemination of FMD from disease foci.