Bluetongue outbreak: key role of the Institute for Animal Health

As the European and World Animal Health Organisation’s (OIE) International Reference Laboratory for bluetongue, scientists at the UK’s Institute for Animal Health’s (IAH) Pirbright Laboratory are bracing themselves to receive many more blood samples from animals in mainland Europe to test for the presence of bluetongue virus. This follows confirmation of the disease in Belgium and Germany, after the initial detection in the Netherlands.  The initial outbreak was confirmed last week at IAH Pirbright.  Institute for Animal Health bluetongue specialists Professor Philip Mellor and Dr Peter Mertens have been advising the UK’s Department of the Environment, Food and Rural Affairs, the European Community and the OIE.

The samples will be examined for the presence of the virus using the same technique that was used to identify the virus last week: the polymerase chain reaction, or PCR, which detects the genes of the virus (blue coils in this model of a bluetongue virus particle).

The country of origin of the virus is not yet known. Knowing this is important with respect to the prevention of future spread of the virus into northern Europe. A clue as to the origin will be obtained when IAH scientists identify the type of the bluetongue virus.  There are 24 types of bluetongue virus, five of which have been identified in some countries of southern Europe.  Not all types are present in each infected country.  Virus in the Dutch samples is being grown in the laboratory to produce the larger amounts of virus that are needed to identify the type of the virus.  IAH has the specialist reagents required to identify the type of bluetongue virus.

Bluetongue

Bluetongue disease in sheep is characterised by a fever that may last for several days. The virus mainly affects the cells lining small blood vessels causing them to leak, and this can lead to reddening and swelling of the lops, mouth, nasal linings and eyelids. Nasal discharge, excess salivation and frothing are common. Animals lose condition rapidly, which leads to muscle degeneration and lameness. Many animals also die from the disease.

Spread by midges

Biting midges feed on the blood, which contains the virus, of an infected animal, and then go to feed on another animal, spreading the virus in the process.  Several years ago the disease spread from Africa, Asia and the southernmost tips of Europe further northwards e.g. into Spain and Italy.  IAH scientists proposed in 2003 that global warming was responsible for this spread. This was due to the spread northwards into southern Europe of the species of midge (Culicoides imicola) that had previously been limited to Africa and Asia. Furthermore, IAH scientists showed that that two other Culicoides species of biting midges (Culicoides obsoletus and Culicoides pulicaris), which are common in central and northern Europe, are also able to spread the virus and are the major transmitters in the more northerly areas. There is the potential for these species of midge to spread the disease in northern Europe.

• For further information contact Dave Cavanagh at the IAH Press Office on +44 (0)1635 577241 or mobile +44 (0)7789 941568.

The Pirbright Laboratory (near Guildford, Surrey, UK) of the Institute for Animal Health is a key UK and international resource. IAH Pirbright is the international reference laboratory for many of the most devastating diseases of farm animals, including bluetongue, foot-and-mouth disease, rinderpest and peste des petite ruminants, swine vesicular disease, African horse sickness and African swine fever, lumpy skin disease, sheep and goat pox.