Immunity survey of vaccinated fattening pigs in the North of FranceF. Wolffa, G. Juillardb, M. Ledruc and J. Guillotind
a Groupement Départemental de Défense Sanitaire des Animaux du Nord, 44 rue Jean Sans Peur, B.P. 643, 59024 Lille Cedex, France
b Direction des Services Vétérinaires Départementaux du Nord, 52 rue de Maubeuge, B.P. 3, 59008 Lille Cedex, France
c Clinique Vétérinaire, 24 rue d'Aire, 59190 Hazebrouck, France
d Laboratoire Départemental Public du Nord, Domaine du Certia, B.P. 39, 369 rue Jules Guesdes, 59651 Villeneuve d'Ascq Cedex, France
Abstract - One of the key points of the success of an eradication scheme for Aujeszky's disease in a high density pig area is, in the first place, the vaccination of pigs, especially fattening pigs so as to immunise them and substantially reduce the spread of the virus between the different stock farms and throughout stock farm. This is the most numerous and the most difficult population to vaccinate. As pigs are mainly vaccinated by stock farmers, we regarded the control of the efficiency of the vaccination in relation to the actual immunisation of vaccinated pigs as indispensable. The choice of the fattening sites pigs to be controlled was made partly at random and partly on purpose, given the doses of attenuated vaccines obtained in each of the stock farms. For each of the controlled fattening sites, a sample of blood was taken at random by an agent of the Departmental Veterinary Services of the north of France from five fattening pigs weighing between 70 and 80 kilograms. Then, this person dispatched the samples to the Public Departmental Laboratory of the north of France whose task was to carry out individually, on each of the samples, two kinds of serological analyses: The steps taken after the control depend on the existence or not of anti-gE seropositive pigs and, in the second case, on the number of anti-gB seropositive pigs: Between November 7, 1997, and October 8, 1998, 122 fattening sites out of 405 registered in the area where vaccination is compulsory were controlled that way, representing 620 samples analysed. These 122 fattening sites could be divided as follows: 3 (2.46%) in the first category, 48 (39.34%) in the second category, 38 (31.15%) in the third category, 17 (13.53%) in the fourth category, and 16 (13.11%) in the fifth category. Out of the 620 analysed fattening pigs, 14 (2.46%) had anti-gE antibodies, 423 (68.23%) had anti-gB antibodies but did not have any anti-gE antibodies, and 183 (29.52%) had neither anti-gB antibodies nor anti-gE antibodies. This method, whose advantages are mainly educational and as little repressive as possible, seems to be efficient since the immunity protection of pigs has been steadily increasing as controls take place. The consequence of this notable improvement is the decrease in the number of livestock contaminated in this area - from 155 to 73 - during the same period of time.
Corresponding author: F. Wolff Tel.: (33) 3 20 30 42 53; fax: (33) 3 20 30 42 52;
© INRA, EDP Sciences 2000