This article, which appeared in La Semaine Vétérinaire No 1299 of 25th January 2008, I have translated for your readers because I thought some farmers and Vets in England might be interested.Susan Baekeland
Battle against blue tongue. Vaccination strategies in the Mediterranean basin - 6 countries share their experience of vaccination against the Blue Tongue.Following the conference on vaccine strategy against the FCO (BTV-8) in Europe organised in Brussels 16th January, last, 4 countries in the south of Europe (France, Spain, Portugal, Italy) were invited to show other European countries their experience of the vaccination against this disease. Well before the arrival of the serotype 8 in the north of Europe in 2006, the Mediterranean basin was hit by serotypes 2,9,4,16 plus 1. There are 24 serotypes. The vaccines (attenuated) were already there, several campaigns of obligatory vaccination were put in place in these countries on herds of sheep with good results. In the third world countries, South Africa and the USA, had equally brought their evidence on this vaccination.
Corsica has been successively touched by three serotypes.For France, the vaccination against the FCO (BTV-8) in the next Spring is not a discovery. In effect, she has already had recourse in Corsica, successively touched by serotypes 2 (2000), 4 (2003) plus 16 (2004). The first vaccination campaign was in the winter of 2000-2001 with a live attenuated South African vaccine against the serotype 2, which had a limited effect due to the weak cover of the vaccine,(less than 70%). A revision of the strategy, in the following year (above 85%) furnished better results. The secondary effects of the South African live vaccine against serotype 16 stopped the campaign 3 weeks after it had been put in place. From 2004 inactive' vaccines from Merial (for serotypes 2 and 4) have replaced attenuated vaccines. Actually serotype 2 has been eradicated from Corsica leaving serotypes 24 and 16 continually in circulation in the sentinel herds. With the epidemiology situation on the island it is easier to control the destiny (of the disease) than on the continent, the programmes put in place show their efficacy in limiting the clinical signs and also the associated economic losses . It also places in evidence the limits of this type of vaccination, to know the absence of the cross-protection between serotypes, its incapacity of stop the viral circulation and at the end the difficulties in finding a route between the vaccination of the herds and the maintenance of viral surveillance in the sentinel herds.
Serotype 8 has recently appeared in the North of SpainIn Spain, the Balearic Islands were the first attacked in 2000, by the serotype 2, followed three years later by the serotype 4. As in France, the attenuated vaccines already existing were used against these two serotypes with conclusive results. So that by 2005 no viral circulation was detected on the Islands. Like the live vaccines these could not be used except in winter (in the absence of vectorial activity), the inactive vaccines have been preferred for use from 2006; During the whole of 2007, then the viral circulation of serotype 4 has disappeared in the peninsular, the serotype 1 is active in the South and in the North. An inactive vaccine has been developed urgently, later also the development of a vaccine against the serotype 8 which, latterly, has appeared in the north of the Iberian peninsular.
Portugal alternates attenuated and inactive vaccines.Since 2005, Portugal proceeded with vaccination against serotype 4, alternatively with live vaccines attenuated and inactive. The indemnified and reglemented zones were placed under an active surveillance, serologic, virological and entomological. Like Spain, these campaigns were obligatory and financed by the government and the European Community. Since November 2007, in collaboration with her neighbour Spain, Portugal has vaccinated equally against the serotype 1 and started experiences in the vaccination of cattle.
Italy, touched since 2000, developed the proper vaccines.Since 2000, the south of Italy and Sardinia have been attacked by four serotypes of the catarrhale fever (Blue Tongue) (2,9, then 4 and 1). The peninsular is nevertheless divided into two zones (North and South) with different risks. These are constantly revalued by active surveillance put in place in 2001. This surveillance is complementary to the vaccination and was put in place in the affected zones. This has shown its effectiveness in the measure of the vaccination cover surpassing 80% of susceptible animals. Italy uses live attenuated vaccines that she developed herself.
Blue Tongue is endemic in South Africa and in the United States.South Africa is the historic cradle of the disease. Nearly all the serotypes are represented. For a number of years the Veterinary Institute at Onderstepoort has developed a large range of live attenuated vaccines against the Blue Tongue. In the countries where the disease has been endemic for centuries, different combinations of multivalent vaccines are frequently employed in the herds of sheep.
The disease is equally maintained in an epidemic manner in the United States in two distinct ecosystems (North and the extreme South) concerning the species of different Culicoides. Various monovalent live vaccines have been developed since the 50's for sheep. A fault of their efficacy ,they have permitted the study of their tetrogenic effect at the first stages in the gestation. As the catarrhale fever (in the USA) only clinically affects sheep, for minorities the other side of the Atlantic the recourse to vaccination remains anecdotal.Michel Bertrou.