Eva Veronesi

Variation in transmission competence of Culicoides, and the genetic basis for differences in transmissibility of BTV strains


E. Veronesi, P. Mertens, P. Mellor, S. Carpenter– Institute for Animal Health-Pirbright – Woking (United Kingdom)
Bluetongue is a non-contagious infectious arthropode-borne viral disease of domesticated and wild ruminants caused by a virus belongs to family Reoviridae genus Orbivirus. So far, 24 different serotypes have been discovered all over the world, between latitudes 35°S and 44°N. Just recently, August 2006, the spreading of the disease in Europe has reached latitude of 52°N with a total number of 17 European countries affected by 7 serotypes.
The transmission between vertebrate hosts is due to the bite of certain species of Culicoides (Diptera: Ceratopogonidae).
Several aspects of the epidemiological system of BTV in Europe still remain poorly understood. In particular, the mechanisms controlling barriers to infection, replication and release of BTV from the gut wall cells and the degree of adaptation required by the virus to allow entry into new vector species.
In this work, we have investigated the effect that multiple passages of BTV, isolated from an infected animal in the field, have in virus genome. BTV-8 blood isolated in the UK in 2006 was passaged several times in KC cells (C. sonorenis) and BHK-21.
The cDNAs from the multiple cell passages were analysed to investigate possible changes in the genome sequence. Results are given for 2 out of 10 segments of the whole genome: Seg-7 encoding for protein VP7 that is considered to be the main species (serogroup) specific antigen for all BTV serotypes and Seg-10, encoding for NS3 protein that seems to be involved in the released of the virus from infected cells after its replication.

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