The need to apply vaccines in different species – small ruminants
2012 • 1 10 Foot and mouth disease (FMD) has been successfully controlled and eliminated in many parts of the world using conventional disease control measures, including vaccination of domestic animals. Potent vaccines have also been the mainstay in controlling outbreaks in non-enzootic regions. Several characteristics of FMD complicate the use of vaccines to control the disease. Not only are there seven serotypes, with little cross-protection between the serotypes, but genetic and antigenic variants occur within these serotypes. In addition, FMD virus can infect over 70 cloven-hoofed species, many of which are free-living wild animals. The role of sheep and goats in the epidemiology of the disease is poorly understood and perceived differently in different parts of the world. This perception is reflected in the vaccination policies applied in these countries. Cattle are generally the species of choice in vaccination programmes, while sheep and goats are vaccinated in only a small number of countries, and then mostly either for strategic purposes or as part of a routine disease control programme. The general assumption is that sheep and goats do not play a significant role in the spread of the disease or as sentinel animals to detect clinical disease. However, this assumption does not hold true for all circumstances or under all epidemiological conditions. This paper describes the potential circumstances under which the vaccination of small livestock should be considered to mitigate the risk of viral spread or to contain an outbreak of the disease. The need to apply vaccines in different species – small ruminants
Evidence that high potency foot-and-mouth disease vaccine inhibits local virus replication and prevents the "carrier" state in sheep.
The ability of a single administration of a high, medium and low potency foot-and-mouth disease (FMD) vaccine to decrease or inhibit local virus replication and excretion in the oropharynx of sheep following aerosol challenge with homologous live virus 14 days later was examined. Unvaccinated sheep showed signs of clinical FMD, whereas all of the vaccinated sheep, regardless of antigen payload, were protected against clinical disease and development of viraemia. Virological and serological results confirmed that there had been no local virus replication in the oropharynx of sheep from the high potency vaccine group in contrast to moderate or substantial virus replication in the oropharynx of the low potency vaccinated or unvaccinated sheep respectively. The vaccines showed no evidence of promoting a local mucosal antibody response at the time of virus challenge, but were capable of stimulating a systemic gamma interferon response, the level of which was related to the antigen payload. This suggests that the systemic gamma interferon response could be a useful indicator of the ability of a FMD vaccine to elicit a sterile immunity and indicates that further work is warranted to investigate the role of systemic gamma interferon in this immunity. This is the first experiment to clearly show that high potency, high payload, FMD vaccines are capable of inhibiting local virus replication and consequently persistence and the carrier state in this target species.
Unidirectional hexagonal rare-earth disilicide nanowires on vicinal Si(100)-2×1
Rare-earth disilicide nanowires grown on vicinal Si(100) with a miscut of 2–2.5° toward the [110] azimuth at 600 °C were studied by scanning tunneling microscopy and compared with those grown on flat Si(001). In contrast to rare-earth disilicide nanowires grown on flat Si(100) surfaces, the nanowires grow unidirectionally along the [01̄1] direction of the vicinal Si(100) surface. Rare-earth disilicide nanowires form bundles composed of single nanowire units on both flat and vicinal surfaces. Yet, on the vicinal surface, the bundle width is comparable to the width of the terrace. The average nanowire length on the vicinal substrate is longer than that on the flat substrate. Scanning tunneling spectroscopy shows that the rare-earth disilicide nanowires have metallic properties.