PII: SO264-410X(97)00166-7 Vaccine, Vol. 16, No. 2/3, pp. 265-271, 1998 0 1997 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0264-410X/98 $19+0.00 zyxwvutsrqpon An inactivated gEmnegative marker vaccine and an experimental gD-subun:it vaccine reduce the incidence of bovine herpesvirus 1 infections in the field J.C. Bosch*, M.C.M. De Jong?, P. Franken& K. Frankenas, J.J. Hage$, M.J. Kalashoek?, M.A. Maris-Veldhuis?, J.P.T.M. Noordhuizen§, W.H.M. Van der PoeIll, J. Verhoeff$, K. Weerdmeester’f, G.M. Zimmer$ and J.T. Van Oirschotj.“” zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED An inactivated glycqvrotein E-negative vaccine and an experimental glycoprotein D-subunit vaccine against bovine herpesvirus 1 (VI) were examined for their effective- ness in a randomized, double-bline, placebo-controlled field trial comprising 130 dairy farms. The use of these marker vaccines enabled us to monitor the incidence of infections in vaccinated populations. The aims of this trial were to evaluate whether these vaccines: (1) reduce the proportion of outbreaks in daiy herds; and (2) reduced virus transmission within dairy herds and to what extent. Vaccination with either of the two vaccines significantly reduced the proportion of herds wherein an outbreak occurred as well as the virus transmission within herds, as compared to placebo-treated herds. The estimated number of seconday cases caused by one infectious animal, expressed as the reproduction ratio R, was for both vaccines significantly >l. This indicates that when BHVl is introduced into vaccinated herds, major outbreaks may still occur 0 1997 Elsevier Science Ltd. All rights reserved Bovine herpesvirus 1 (13HVl) belongs to to the alpha- herpesvirinae, a subfamily of the herpesviridae. Infec- tions in cattle may lead to severe symptoms of infectious bovine rhinotracheitis (IBR), as well as infectious pustular vulvovaginitis (IPV) or infectious balanoposthitis (IPB). Subclinical infections also occur’. Like most herpesviruses, BHVI remains latent after primary infection- a phase which is characterized by the absence of clinical symptoms and lifelong persistence of viral DNA in trigeminal and other sensory ganglia’,‘. After stress or corticosteroid treat- ment, the latent virus can be reactivated, reexcreted and transmitted to susceptible animals4. Therefore, cattle infected with BHVl must be considered as *Holland Genetics, P.O. Box 5073,6802 EB Arnhem, The Netherlands. tlnstitute for Animal Science and Health, ID-DLO, P.O. Box 65, 82100 AB Lelystad, The Netherlands. *Animal Health Service, P.O. Box 9, 7400 AA Deventer, The Netherlands. §Wageningen Agricultural University, Depart- ment of Animal Health and Epidemiology, P.O. Box 338, 6700 AH Wageningen, ‘The Nethlerands. TDepartment of Herd Health and Reproduction, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80151, 3508 TD Utrecht, The Netherlands. (Received 26 February 1997; revised version received 16 June 1997; accepted 24 June 1997) lifelong potential sources of virus spread. However, the mere fact that reactivation can occur does not neces- sarily imply that reactivation is important in the epide- miology of BHVI. Several countries, for example, Denmark and Switzerland that had a low prevalence and never permitted vaccination, have succeeded in the eradica- tion of BHVl by test and removal procedures. The BHVl-negative status of these countries puts pressure on other countries to also control or eradicate the virus. In countries with a high prevalence, like the Netherlands’, eradication of BHVl is only economic- ally feasible by first lowering the prevalence, possibly followed by test and removal procedures. Vaccination with conventional vaccines has been the most important control strategy world-wide. Although these vaccines can induce good clinical protection”, it is not known whether herd immunity is induced. Further- more, cattle vaccinated with conventional vaccines cannot be distinguished from cattle infected with the field virus by serological tests. For that reason, conven- tional vaccines are not suitable for an eradication programme based on a test and removal strategy. Marker vaccines, which lack at least one glyco- protein present in the corresponding wildtype virus, Vaccine 1998 Volume 16 Number 2/3 265