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Bovine Herpesvirus Type 1 (BHV1) is the aetiological agent of a number of diseases and not only of IBR, namely infectious pustular vulvovaginitis (IPV), infectious balanoposthitis (IBP), conjunctivitis, encephalomyelitis, mastitis, abortion, enteritis, and lesions in the interdigital space. The serological identical strains differ, however, in some aspects. Typical genital strains usually cause a mild illness, sometimes not even detected clinically, but serologically. They hamper eradication programmes and do not cause IBR when inoculated intranasally. The other--modern--strains are, however, always able to induce a severe disease in the genital tracts. But infection of field or vaccine virus leads to the development of humoral and cell-mediated immunity. The latter is, however, not transmitted to neonates via colostrum. BHV1 antibodies can be found in bovines in all continents, and in many wild species. Prevalences vary greatly depending on herd size and management. Because seronegative cattle play a role in international trade a number of European countries have eradicated BHV1, with very high costs involved. Marker and conventional vaccines can prevent disease but not infection followed by the state of latency. The genomes of several strains, including the marker strains can remain latent in the same animal and be reactivated after stress or injection of corticosteroids. For the detection of humoral antibodies the ELISA is widely used. It is useful for testing bulk milk samples for antibodies derived from field virus and conventional vaccines but not from gE-deleted marker vaccines. Importing countries should consider only vaccinated animals for import. They should require that the animals are seronegative prior to vaccination.

Within nine months, enzootic bovine leukosis (EBL) occurred in 23 well documented herds. Eight of them (= 35%) had previously conducted the eradication programme as laid down by law. This proportion is tenfold higher than anticipated from the average incidence rate since 1978. The conclusion is drawn that a higher risk for reinfection exists for herds previously infected and cleaned than for those that never had leukosis before. For such cases hypotheses are presented. In one case clear evidence for one of the hypotheses was obtained. In case of re-occurrence of EBL in a previously cleaned herd it is proposed to examine the white blood picture of the sero-positive animals. If hematologically positive cattle are detected, they should be removed from the herd including their offspring.

After a review on the viral agents playing a role in diseases of cattle those related to the occurrence in the genital tract are described. They may be causing abortion or local reactions leading to a reduced fertility and/or be of importance for the embryo transfer. Bovine herpesvirus type 1 (BHV1) and the bovine virus diarrhoea virus (BVDV) are the agents most widely distributed in Europe. Both are of economic importance, described in detail and vaccines available discussed.

The use of gl deleted live vaccines against Aujeszky's disease (AD) facilitates to differentiate vaccinated from field-virus infected animals. In this study different modes of vaccination were tried to find out how sheep can be protected from a lethal infection with ADV. It could clearly be demonstrated that Aujeszky disease virus (ADV) is spread by horizontal transmission from infected pigs to sheep. The nasal discharges of infected pigs contained a maximum of 10(8.75)TCID50/g mucus at days 3 and 4 p.i. and those of the contact-pigs 10(8.5)TCID50/g mucus at days 6 and 7 after contact. Non-vaccinated contact sheep were infected horizontally by the pigs. The highest titres ranged from 10(6.25) to 10(7.5)TCID50/g mucus. These animals were sacrificed at day 5 p.i. exhibiting acute symptoms of AD. The nasal discharge of vaccinated sheep contained much lower amounts of ADV (maximum: 10(4.25)TCID50/g mucus). All surviving animals had developed antibodies. Following challenge with the ADV-strain NIA3, no febrile response or virus-shedding was observed in sheep vaccinated 2x s.c. or 2x i.m. with a gl deleted live vaccine, whereas sheep, vaccinated only 1x i.m. (4 out of 4 animals) or 1x i.m. (3 out of 4 animals) or 1x i.n. and 1x i.m. (1 out of 4 animals) had to be sacrificed after showing acute symptoms of AD. In conclusion it can be stated that a double parental vaccination with a gl deleted live vaccine protects sheep against a field-virus AD infection.

Following an outbreak of FMD caused by an A5 strain in the spring of 1984, ten cattle were vaccinated with samples of the five commercial vaccines used for the vaccination campaign in that year, i.e. two animals per vaccine. Six weeks later the cattle were challenged by contact with animals inoculated with the virus strain isolated from the field outbreak. Seven of the ten cattle became severely ill, exhibiting the typical symptoms of FMD, one animal did not show any clinical symptoms, the remaining two weak ones that might have escaped recognition by the cattlemen. Virus could be recovered from the vaccinated animals from days 2 to 10 following contact with the non-vaccinated infected cattle. It was concluded that a single vaccination does not protect cattle against the isolate.