A new bluetongue protection zone has been set up after a case was found in Greater London, the government's environment department, Defra, said.
A new case of bluetongue disease has been found in Greater London
The new 20km zone covers parts of west and north London and extends into Buckinghamshire and Hertfordshire.
Two further new cases have been found inside the existing bluetongue protection zone covering much of East Anglia and the South East.
That zone has been extended further into Surrey and Cambridgeshire.
All of the animals are thought to have been infected before the "vector-free period", which was declared in December after it was judged there was a low risk of the disease spreading because of the cold weather.
There are now 75 confirmed cases of the virus, which is spread by midges and can be fatal to animals such as sheep and cows.
The cases were identified by routine testing required before animals can be moved out of the protection and surveillance zones.
The surveillance zone remains in place covering much of England.
Defra said further cases could be identified in the coming weeks.
Bluetongue was first confirmed in the UK in East Anglia on 28 September.
All other cases have been confined to south-east England.