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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. [Copyright &y& Elsevier]

In 2009–2011, spread of a serotype O foot-and-mouth disease virus (FMDV) belonging to the South East Asia topotype led to the culling of over 3.5 million cattle and pigs in Japan and Korea. The O1 Manisa vaccine (belonging to the Middle East-South Asian topotype) was used at high potency in Korea to limit the expansion of the outbreak. However, no data are available on the spread of this virus or the efficacy of the O1 Manisa vaccine against this virus in sheep. In this study, the early protection afforded with a high potency (>6 PD 50 ) FMD O1 Manisa vaccine against challenge with the O/SKR/2010 virus was tested in sheep. Sheep ( n = 8) were vaccinated 4 days prior to continuous direct-contact challenge with donor sheep. Donor sheep were infected with FMDV O/SKR/2010 by coronary band inoculation 24 h prior to contact with the vaccinated animals, or unvaccinated controls ( n = 4). Three of the four control sheep became infected, two clinically. All eight O1 Manisa vaccinated sheep were protected from clinical disease. None had detectable antibodies to FMDV non-structural proteins (3ABC), no virus was isolated from nasal swabs, saliva or oro-pharyngeal fluid and none became carriers. Using this model of challenge, sheep were protected against infection as early as 4 days post vaccination. [ABSTRACT FROM AUTHOR]

Abstract: Foot-and-mouth disease (FMD) in adult sheep usually causes milder clinical signs than in cattle or pigs, and is often subtle enough to go undiagnosed. In contrast, FMD in lambs has been reported to cause high mortality during field outbreaks. In order to investigate the pathogenesis of FMD in lambs, two groups, aged 10–14 days, were infected with foot-and-mouth disease virus (FMDV) type O UKG. One group of lambs (n =8) was inoculated with FMDV in the coronary band, while the other (n =4) was infected by direct contact with FMDV-inoculated ewes. Daily serum samples and temperature measurements were taken. Lambs were killed sequentially and tissue samples taken for analysis. Using real-time RT-PCR, viral RNA levels in tissue samples and serum were measured, and a novel strand-specific real-time RT-PCR assay was used to quantify viral replication levels in tissues. Tissue sections were examined for histopathological lesions, and in situ hybridisation (ISH) was used to localise viral RNA within histological sections. The contact-infected lambs became infected approximately 24h after the ewes were inoculated. Vesicular lesions developed on the feet of all lambs and on the caudo-lateral part of the tongues of six of the eight inoculated lambs and three of the four contact-infected lambs. Although no lambs developed severe clinical signs, one of the contact-infected lambs died acutely at 5 days post-exposure. Histological examination of the heart from this lamb showed multi-focal areas of lymphocytic-plasmacytic myocarditis; similar lesions were also observed in the hearts of three of the inoculated lambs. Using ISH, viral RNA was localised within cardiac and skeletal muscle cells from the lamb which had died, and also from vesicular lesions on the coronary band and tongue of inoculated lambs. These results provide a detailed description of the pathogenesis of the disease in lambs. [Copyright &y& Elsevier]