A second cow had tested positive for bluetongue on the same farm in Baylham, Suffolk, where the first case was confirmed over the weekend, Defra said.
Meanwhile, a seventh case of foot and mouth disease was confirmed at a site within the existing protection zone in Surrey.
Two temporary protection zones in Hampshire are also being investigated by Defra.
From 3.30pm this afternoon Defra will set up 'risk areas' in parts of the country most at risk of the diseases.
It will establish a bluetongue temporary area, covering Lincolnshire, Nottinghamshire, Leicestershire, Cambridgeshire, Norfolk, Suffolk, Northamptonshire and Bedfordshire.
An FMD risk area will be set up across Essex, Kent, East and West Sussex, Hampshire, Surrey, Berkshire, Hertfordshire, Buckinghamshire and Greater London.
”All these areas will be kept under active review and we will continue with a risk-based, staged approach. The aim is to reduce the size of the FMD risk area as work progresses,” said chief veterinary officer Debby Reynolds.