Implementation of two-step vaccination in the control of bovine viral diarrhoea (BVD).

Bovine viral diarrhoea (BVD) control/eradication programmes based on the test and removal of persistently infected cattle without use of vaccination were first introduced by the Scandinavian countries in the early 1990s. Within the last 10 years the programmes have proven to be very successful and have served as a blueprint for several other European regions. However, in areas with high cattle densities, intense animal trade and high BVD prevalence this control approach is risky, because there is a high probability that herds, which have been cleared of persistently infected (PI) animals and have become partly or fully susceptible to reintroduction of the virus, will come in contact with a BVD virus (BVDV) infected animal. A combination of the test and removal strategy with subsequent systematic vaccination of cattle could overcome this problem. The goals of vaccination in such a programme is protection against reintroduction of BVDV into herds free from PI cattle and foetal protection of pregnant animals accidentally exposed to the virus. Two-step vaccination is based on the use of inactivated BVDV-1 vaccine for priming followed by a live attenuated vaccine booster 4 weeks later. The immune response elicited by such a vaccination scheme has proven to be long lasting and foetal infection after challenge with BVDV-1 and BVDV-2 was prevented in pregnant animals 5 months after vaccination. These findings suggest that the implementation of a two-step vaccination in the initial phase of control programmes in addition to test and removal of PI animals in areas with high cattle densities and endemic BVD is practical and efficacious.

[Analysis of bulk milk samples using polymerase chain reaction: an additional tool for bovine viral diarrhea monitoring]. / Untersuchung von Sammelmilchproben mittels Polymerasekettenreaktion: Eine ergänzende Methode für die BVD-Uberwachung.

Programmes for the eradication and control of infections with bovine viral diarrhea virus (BVDV) concentrate on the identification and elimination of persistently infected (PI) animals. The identification of these animals is mainly based on the detection of viral antigen using ELISA techniques. Protocols detecting viral nucleic acid using RT-PCR have been described recently. Due to high costs the German model recommends screening of animals of 9 up to 36 months of age. Screening of bulk milk samples using RT-PCR technology would allow a system independent of age. The aim of the present study was to test whether bulk milk samples (1433 including max. 50 animals each) collected in four counties of Lower Saxony are suitable for a complementary identification of PI animals via RT-PCR. Thirty-one bulk milk samples derived from 27 dairy herds were BVDV positive, corresponding to 2.3 % of the herds analysed in this study. Two samples first scored doubtful. Follow up tests revealed lactating PI animals in most cases (18). In other cases the epidemiological status of the herd, i.e. high sero-prevalence and/or presence of PI animals among non-lactating cattle, suggested a transient infection detected in the first bulk milk sample. These results demonstrate that monitoring of lactating cattle of any age using RT-PCR is a very sensitive, economically effective additional method for the identification of PI animals.

[Fifteen years of paratuberculosis eradication programs. Experiences from the Lower Saxony Animal Epidemic Finance Office]. / 15 Jahre Paratuberkulosebekämpfung Erfahrungen der Niedersächsischen Tierseuchenkasse.

15 years of systematic paratuberculosis control programs in Lower Saxony were reported and critically judged. The proposed measures were considered with respect to suitability and enforceability.

[BVD/MD and its control in Lower Saxony (after the support of the Lower Saxony animal epidemic fund)]. / BVD/MD und ihre Bekämpfung in Niedersachsen (nach den Unterlagen der Niedersächsischen Tierseuchenkasse).

A report is given on the development of the subsidies granted by the "Niedersächsische Tierseuchenkasse" für BVD/MD since 1973. The article shows the cyclic procedure and regional differences as well as the participation of vaccinations and embryo transfer at the frequent occurrence of persistent viraemic animals in single herds. According to the authors' opinion the struggle against BVD/MD must have two aims: 1. to search for and to cull out persistent viraemic animals 2. to prevent the arise of new persistent viraemic animals.