Attempted transmission of Brucella ovis between red deer stags by successive grazing or adjacent-paddock grazing

To determine whether Brucella ovis can be transmitted from stag to stag by successive grazing of infected and noninfected stags in the same paddock, or by grazing infected and non-infected stags in adjacent paddocks.

Six red deer stags (Cervus elaphus) were artificially infected with B. ovis and 5 were confirmed to be shedding the organism in their semen. Infected stags alternated paddocks, and therefore grazing and wallows (successive grazing), once or twice weekly with 6 non-infected stags from 3 March to 18 August, 1999. Direct contact between the 2 groups of animals was prevented. The 2 groups alternated paddocks 32 times. Six other non-infected stags were grazed in a paddock adjacent to the infected stags throughout this period, separated by a standard deer fence. Non-infected stags were blood sampled at 2to 6-week intervals to test for B. ovis antibodies using a complement fixation test and an enzyme linked immunosorbent assay.

No stag from either non-infected group became infected with B. ovis.

The risk of stags becoming infected with B. ovis by successive grazing of the same paddock as, or by grazing in paddocks adjacent to, infected stags appears to be low. We conclude from this result, and similar experimental evidence and experience of this disease in sheep, that transmission of B. ovis requires animals to be grazed or confined together in a way that allows direct contact between animals.

It is likely that infected and non-infected stags can be managed on the same property without transmission occurring between the groups, provided that they do not come into direct contact with one another.