The dramatically different clinical outcome of experimental infections makes vaccine evaluation difficult. There are currently two challenge models employed for vaccine efficacy trials in ruminants, both possessing inherent Antidiabetic Compound Library in vitro problems [5], [6], [7] and [8]. The abortion model is cumbersome with synchronization of the pregnancy and scheduling of high biosecurity facilities. The drawback of a viremia model can be a lack of consistency, as not all experimentally inoculated animals may develop detectable viremia [5], [9], [10] and [11], although sensitivity
of detection may had been also an issue. For example Yedloutschnig et al. [12] and [13] titrated the virus inoculum for sheep and cattle inoculations in Vero cells, but used more sensitive intraperitoneal inoculation of 4–6 days old mice to detect viremia in the infected ruminants. Currently, RNA detection is used to compensate for the lower sensitivity of virus isolation in cell culture. Different age ZD1839 chemical structure animals were used in previous studies, ranging from one-day-old lambs to several years old adults. Our experimental
target age was 3–4 months, when sheep and goats are usually vaccinated on farms. Virus doses used in the inocula in the reviewed reports were of a wide range, titrated on different substrates, and therefore difficult to directly compare. Often, viremia outcome was not in correlation with the dose. This may be possibly related to individual and breed variations, and to a low number of animals used in most studies (two to four animals for the same route and dose). Overall it appears that lower doses lead to somewhat later development of viremia, delaying its detection from day one to 2–3 days post inoculation. An intraperitoneal route of inoculation was often used in the early experiments, while more recently subcutaneous route is used in majority of studies. Additional or alternative routes have been also tested, such as mucosal, intravenous, or intradermal inoculation [5], [6], [7], [8], [9], [10], [11], [12], Tolmetin [13], [15], [18] and [19]. There are
very few, older publications on the experimental inoculations of goats, suggesting that the duration of viremia may be shorter than in sheep: between 1 and 3 dpi, both days inclusive [16] and [17]. There is one report currently published on vaccine safety in goats [20], but there are no reports on vaccine efficacy studies in goats; the second most susceptible ruminant species to Rift Valley fever virus. Recently, our group started to work on the experimental infections of goats [21], as vaccine immunogenicity, safety and efficacy testing in this target species may be also required. The aim of this study was to develop a viremia model in goats and sheep of vaccine age (3–4 months) suitable for vaccine efficacy studies.
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