Progress of the Aujeszky's disease virus eradication programme in Brittany (France)V. Auvigne and C. Bougeard
Union des groupements de Producteurs de Viande de Bretagne, BP 6613, 35066 Rennes Cedex, France
Abstract - Brittany is the main pig production area in France. About 14 million fatteners are produced per year in this province. There are 9200 farms holding about sows. Farrow-to-finish herds are prevalent representing half of the farms and 70% of the production. More than 4 million piglets are transported per year. An eradication program for Aujeszky's disease is currently in action. The key points of this program are: (1) yearly general serological screening, (2) quarterly blood testing of nucleus and multipliers herds, (3) compulsory vaccination, (4) special authorisation needed to move piglets out of non-AD free farms given by veterinary services. The yearly general serological screening for Aujeszky's disease has been compulsory since 1994. The herds were sampled from October 1st to May 31st. Fifteen sows were bled in each breeding stock and fifteen fatteners in each fattening stock. Vaccines used were marker vaccines and serological analysis were GE ELISA. A herd was declared positive when at least one of the sera was positive. For the Farrowing-to-Finish farms (FAFI), serological status of the breeding unit was considered to be independent of the fattening unit. A database of all the herds was available. For each herd, its production type (Farrowing-to-Feeder (FAFE), Farrowing-to-Finish (FAFI) and Feeder-to-Finish (FEFI), size and location were known. The seroprevalence of breeding stocks of FAFE and FAFI herds was respectively 23.2% and 28.1% in 1994/1995, 11.3% and 14.4% in 1995/1996, 4.8% and 8.3% in 1996/1997, 2.7% and 5.3% in 1997/1998. The seroprevalence of fattening stocks of FAFI and FEFI herds was respectively 13.2% and 17.2% in 1994/1995, 5.4% and 6.7% in 1995/1996, 3.4% and 5.3% in 1996/1997, 2.6% and 2.6% in 1997/1998. Despite some local resurgence, seroprevalence has decreased every year since 1994, whatever the production type. However, the evolution seems to be asymptotic. The decrease of infection rates which was considerable the two first years, has been less important since then. Moreover the seroprevalence of breeding stocks of FAFI, which was close to that of FAFE in 1994/95, was twice more important in 1997/98. This figure gives evidence of some difficulties to eradicate Aujeszky's disease in some FAFI herds, where fatteners are very close to sows. In the same way, FEFI fattening stocks were more contaminated than FAFI stocks in 1994/95. In 1997/1998, infection rates of both production types were equivalent. This figure is certainly related to the control of animal movements which tends to decrease the risk of FEFI herds being purchased with infected piglets. The eradication plan now has to focus on herds remaining infected despite vaccination. A "test and removal" program will begin at the end of 1999. Vaccination will have to be continued until the last positive animal of the region is slaughtered.
Corresponding author: V. Auvigne Tel.: (33) 2 99 65 03 01; fax (33) 2 99 30 15 34;
© INRA, EDP Sciences 2000