BVDV control program in Austria - Is a monitoring of the BDV status in sheep in Austria necessary?

Abstract

In cattle referred to the Clinic of Ruminants at the University of Veterinary Medicine Vienna by local veterinarians from Lower Austria, the number of animals positive for antibodies against pestiviruses decreased from 11.9% in 2004 to 7.4% in 2007. In other Austrian regions the seroprevalence of 17.6% in 2004 dropped to 12.2% in 2007. The seroprevalence rates were considerably higher in older animals than in younger indicating a marked decrease of new infections (8.2% in < 1.5 years old animals, 6.8% in 1.5-4.5 years, 19.8% in 4.5-7.5 years and 33.3% in > 7.5 years). These data nevertheless also demonstrate that new pestivirus infections occur, although at a lower rate. We report the case of a calf persistently infected with Border disease virus-3 (BDV-3) detected in a mixed cattle and sheep farm with the status "BVDV-free". Earlier investigations have shown that BDV-3 is endemic in Austrian sheep populations and seems to be a potential risk factor for the reintroduction of pestiviruses in BVDV free cattle herds. Serological findings among the investigated sheep population showed in four out of nine sheep samples considerably higher titres to the BDV strain Moredun than to the BVDV strain NADL. Seroconversion against pestiviruses was also detected in contact cattle and the mother of the persistently infected calf. Pestivirus specific RNA was neither detected in the blood samples collected from the patients of the Clinic for Ruminants nor in the sheep or cattle investigated on the farm described.