Bluetongue in Sheep

Bluetongue in Sheep
Bluetongue in Sheep
Bluetongue in Sheep
Bluetongue in Sheep

In the autumn of 2006 Bluetongue (serotype 8) was found in the Netherlands, Belgium, Luxemburg, Western Germany and in parts of North Eastern France. The outbreak was identified as a new incursion in the EU. How Bluetongue entered Europe is still subject to investigation.

In August 2008 the first case of Bluetongue serotype 8 was diagnosed in East Anglia in a cow.

Bluetongue was first described in South Africa but has since been recognised in most countries in the tropics and sub-tropics. Since 1999 there have been widespread outbreaks of Bluetongue in Greece, Italy, Corsica (France) and the Balearic Islands (Spain). Cases also occurred in Europe in Bulgaria, Croatia, Macedonia, Kosovo and Yugoslavia. Serotypes 8, 1, 2, 4, 9 and 16 have been involved. These cases have been well north and west of its normal distribution. It appears that the virus has spread from both Turkey and North Africa. Bluetongue does not affect humans. A virus within the Orbivirus genus of the family Reorvirades causes bluetongue. At present 24 distinct serotypes have been identified as a result of serum neutralisation tests.

The virus is transmitted by a small number of species of biting midges of the genus Culicoides. Bluetongue virus cannot naturally be transmitted directly between animals. Virus transmission between animals occurs via the insect vector; some species of midges. However, the likelihood of mechanical transmission of the virus between herds/flocks and within a herd/flock by unhygienic practices (e.g. use of contaminated surgical equipment or hypodermic needles) cannot be excluded.

When a midge bites an infected animal, the virus passes to the midge in the blood meal and the virus multiples in the midge. The cycle of replication of the virus in the insect vector and in the ruminant host, results in amplification of the amount of virus available to naïve hosts and vectors.

Peak populations of vector Culicoides occur in the late summer and autumn and therefore this is the time when Bluetongue is most commonly seen.

Clinical signs can vary by species – although symptoms are generally more severe in sheep, cattle can occasionally show signs of disease. Cattle are important in epidemiology of the bluetongue as they act as an often silent source of BTV – a reservoir for disease and keep the infection circulating. It is important to be vigilant, especially in the case of sheep. If you suspect any signs of the disease you must report this immediately to your local Animal Health Office.

Clinical signs in sheep:

  • Eye and nasal discharges
  • Drooling as a result of ulcerations in the mouth
  • High body temperature
  • Swelling of the mouth, head and neck
  • Lameness
  • Haemorrhages into or under the skin
  • Inflammation at the junction of the skin and the horn of the foot – the coronary band
  • Respiratory problems – difficulty with breathing and nasal discharge
  • A blue tongue is rarely a clinical sign of infection
  • Deaths of sheep in a flock may reach as high as 30 per cent. Animals that survive the disease can lose condition with a reduction in meat and wool production.

Bluetongue UK Situation 2011.

On 12th June 2010, Scotland, England and Wales moved into a Lower Risk Protection Zone (LRZ) for BTV-8.

This LRZ provides some increased protection against imports from higher risk zones and is being viewed as the first move towards disease freedom.

There were no outbreaks of BTV in the UK in 2010 and no evidence of bluetongue virus circulation in the winter of 2009. Further testing was to be carried out in 2010 but the results have not yet been reported.

Between April and October 2010, new outbreaks of BTV were reported in Greece, Cyprus, Italy, Portugal and Spain.

In the UK We must not be complacent. We need to continue to take steps to keep disease out, so that we maintain a good chance of becoming free and removing our BTV zones and trade restrictions.

Vaccination played a key role in keeping us free from circulating bluetongue disease in 2008 – 2010 and will provide the greatest security against loss, should there be a resurgence of disease in 2011.

Vaccination before the start of the risk period or when the midges and disease become active is still being recommended by NFU and DEFRA.. For those who vaccinated last year, a reminder that only a single vaccination booster is required in both cattle and sheep.

It is vital that we continue to remain vigilant for signs of disease. Suspicion of disease must be notified immediately to your local DEFRA Animal Health Office.

For the current situation, please consult the DEFRA website.

My thanks to Dr. Van Aert Marcel for the use of his photographs.