Community Research and Development Information Service - CORDIS

Vaccine viruses have been shown to elicit viraemias in sheep & to replicate in vector Culicoides to levels confirming transmission can occur

Live attenuated vaccine viruses have long been used to alleviate disease in sheep in various parts of the world and they are now being used in the face of BT V incursions into southern Europe. However, many authorities consider that there are a number of risks associated with the use of such vaccines.

In relation to these risks the work of this project has shown that:
1. Vaccine viruses themselves may cause clinical signs of disease in some breeds of sheep.
2. Vaccine viruses in vaccinates may elicit a viraemia of sufficient titre and duration to infect vector midges.
3. Vector midges can support vaccine virus replication to levels confirming transmission will take place.
4. There was no evidence of increasing virulence on vaccine virus passage through vector midges � but see 1.
5. �Vaccine-like� viruses can be isolated in the field suggesting that natural reassortants between vaccine and field strains may occur in dually infected hosts.

Related information

Reported by

Pirbright Laboratory, Ash Rd., Pirbright,
United Kingdom
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