Airborne transmission of bovine herpesvirus 1 infections in calves under field conditions

A small scale transmission experiment was performed with bovine herpesvirus 1 (BHV1) in a cattle population under field conditions. 10 calves were hou sed under strict hygienic conditions, with a distance of 4 m between each c alf. Five calves were experimentally infected with BHV1, two calves with st rain Harberink and three with strain Lam, respectively. Experimentally infe cted calves were placed at 4 m distance from five susceptible sentinel calv es. Airborne transmission to sentinel calves was detected using virus isola tion and BHV1 specific polymerase chain reactions in samples of nasal fluid s, and BHV1 specific antibodies in serum samples. Strain Harberink was hard ly transmitted to sentinel calves, whereas strain Lam was transmitted to al l sentinels. Estimating the rate of transmission per day, the total number of calves infected by one (strain Lam) infected calf was 1.18. Comparing this estimated transmission ratio between cattle at a distance of 4 m to the estimated transmission ratio R of BHV1 in susceptible commingle d cattle reported before, the effect of the factor distance on the transmis sion ratio could be calculated. Extrapolating these results, a distance of 4.4 m between cattle populations would be necessary to reduce transmission for this strain to R<1. (C) 2000 Elsevier Science B.V. All rights reserved.