The target of this project was to evaluate the consequences of a BDV infection on the foetus and on any resulting born calves during the second half of pregnancy.
To do this, four BDV-antibodies positive heifers, in their 19th week of pregnancy, were used. In previous research, carried out by Mag. J.
Rötzel, these heifers where stabled with sheep persistently infected with BDV and had been successfully infected. The health of the animals was continuously monitored over the duration of pregnancy right up the point of birth. A spontaneous abortion (267 d of gestation) was recorded which showed that viral RNA was present in the foetus organic samples and in the placenta. Following the physiological pregnancy, three live and healthy calves were born. During examinations to follow, blood samples were taken, together with corneal swabs, nasal swabs and faeces samples. Only one of the examined calves showed antibodies against pestiviruses in its precolostral blood. The results of the tests on the second calves´ samples, on the other hand, showed a negative ab-ELISA test and a positiv PCR test.
At the age of 7 months, these tests were repeated on the third calf. The results of these tests, extraordinarily enough, showed results which were quite on the contrary to the initial ones. No apparent virus specific RNA was present in the blood samples but antibodies were detectable. Furthermore, the animals in question were dissected and examined, but none of the cows nor their calves showed any abnormalities. There were also no signs of BDV in their organs.
In many Austrian counties, the numbers of ab- an virus-positive cows have been reduced to almost zero. This is due to the Austrian eradication measures, which were enforced in August 2004 to fight BVD.
The results of this project show that sheep play a bigger part being a reservoir for pestiviruses than initially assumed. One should consider to also include small ruminants in the fight against BVD.