1. CONTROL OF BVDV-INFECTION ON COMMON GRASSLAND - THE KEY FOR SUCCESSFUL BVDV-ERADICATION W. Rossmanith, R. Janacek, E. Wilhelm

2. Lower Austria Upper Austria Styria Carinthia TyrolSalzburg Vorarl- berg Burgen- land Vienna

3. Skandinavian control and eradication without vaccination started in Lower Austria in autumn 1996 Voluntary program supported by the local government, the breeding organisation and the animal health service

4. Principles of the scandinavian eradication program Dividing herds into presumably non infected and infected herds by using herd level tests on bulk tank milk, individual milk samples of young cows or spot tests from 5-10 young stock Protection of non infected herds, by avoiding contacts with herds with an unknown BVDV- status

5. Disease clearence in infected herds by testing all animals of a herd and follow-up examination of all new born calves during one year after initial screening Persistently infected (PI) animals have to be identified and slaughtered Certification of herds as BVDV-free as a helpful tool to enable save contacts between the herds

6. Task sharing of the BVDV-program in Lower Austria Milk samples are collected by recorders of the milk recording association Blood samples are collected by veterinarians Sample testing and reports are performed by the laboratory of the animal health service Permissions for animals to enter a market are issued by the district veterinary officers Certification of herds is a teamwork of the official veterinarians, the practical veterinarians and the recorders of the milk recording association

7. Rules and regulations for communal grazing, markets and exhibitions To trade animals from certified herds as free from BVDV- infection or to put them to communal grazing, the latest herd level test must have been done within the last three months Animals from herds with unknown BVDV-status must be tested individually before communal grazing Testing all calves under 5 months regardless of herd status Owners of infected herds are only allowed to sell non pregnant dams tested for the presence of viral antigen

8. Tests after the end of the common grazing season At least 10% of the cattle stock of each common grasland have to be tested for BVDV specific antibodies The animals with an antibody negative result at the beginning of the common grazing season have to be negative also at the end of the season. This result confirms the stock of common grassland to free of a PI-animal

9. Diagnostic methods BVDV-specific antibodies in blood or milk samples are analysed with an indirect ELISA (Svanovir ®, Svanova Biotech, Sweden) The presence of viral antigen in blood samples is tested with antigen ELISA (Herdcheck ®, IDEXX Scandinavia, Österbybruck, Sweden) Antigen ELISA results are retested with RT-PCR

10. Results from areas with common grassland In 1999 out of 4630 animals 24,4 % were seropositive, 33 PI animals were detected. In 2002 the prevalence of seropositive animals was reduced to 12,96 %, only 2 PI animals were found on the occasion of the spring-tests

11. Results from areas with common grassland The last seroconversions on a single common grassland were detected 1999 on the occasion of the autumn tests caused by an untested PI animal In an area with intensive pasture utilisation 102 roe deer samples were analysed with serum neutralisation-test for BVDV specific antibodies with negative result

12. Percentage of certified herds in regions with intensive pasture utilisation versus other areas Out of 4833 participating herds 2767 (57,3%) have reached a certified status in regions with intensive pasture utilisation In the other regions out of 5566 participating herds 2337 (43,0%) have reached a certified status

14. Costs of the BVDV-program in Lower Austria The annual costs of the program are 1,60 Euro for each head of cattle

15. BVDV Legislation in Austria A legislative proposal was established 2003 to make BVDV-eradication compulsory for all farmers in Austria. This law is now operative since 1. August 2004

16. Conclusion 1 Communal grazing is an important risc factor for BVDV- transmission where susceptible pregnant cattle from several herds may be mixed with PI-animals, BUT With a reliable system for identification of PI-animals and a high certainty of prevention of PI-animals on common grasland, the mode of BVDV infections can be stopped The results of testing for BVDV specific antibodies in roe deer blood samples indicate the role of roe deer is neglectible in transmitting BVDV to cattle

17. Conclusion 2 Transiently infected animals are very inefficient in transmitting the virus Cattle from infected herds can join communal grazing without infection risc for susceptible participant animals In the regions with intensive pasture utilisation the percentage of certified BVDV-free herds is higher than in the other regions

18. Acknowledgements Stefan Alenius, Prof., PhD Stefan Vilcek, Prof.,PhD Practising Veterinarians Cattlebreeders NÖ Rinderzuchtverband NÖ Landeskontrollverband NÖ Tiergesundheitsdienst