Pritchard G C, Smith R P, Errington J, Hannon S, Jones R M, Mearns R
Animal Health and Veterinary Laboratories Agency (AHVLA) - Bury St Edmunds, Rougham Hill, Suffolk IP33 2RX, UK.
Vet Rec. 2011 Oct 8;169(15):391. doi: 10.1136/vr.d4693. Epub 2011 Sep 6.