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

Aim: To determine whether Brucella ovis can be transmitted from stag to sta g by successive grazing of infected and non-infected stags in the same padd ock, or by grazing infected and non-infected stags in adjacent paddocks. Methods: Six red deer stags (Cervus elaphus) were artificially infected wit h B. ovis and 5 were confirmed to be shedding the organism in their semen. Infected stags alternated paddocks, and therefore grazing and wallows (succ essive grazing), once or twice weekly with 6 non-infected stags from 3 Marc h to 18 August, 1999. Direct contact between the 2 groups of animals was pr evented. The 2 groups alternated paddocks 32 times. Six other non-infected stags were grazed in a paddock adjacent to the infected stags throughout th is period, separated by a standard deer fence. Non-infected stags were bloo d sampled at 2- to 6-week intervals to test for B. ovis antibodies using a complement fixation test and an enzyme linked immunosorbent assay. Results: No stag from either non-infected group became infected with B. ovi s. Conclusions: The risk of stags becoming infected with B. ovis by successive grazing of the same paddock as, or by grazing in paddocks adjacent to, inf ected stags appears to be low. We conclude from this result, and similar ex perimental evidence and experience of this disease in sheep, that transmiss ion of B. ovis requires animals to be grazed or confined together in a way that allows direct contact between animals. Clinical relevance: It is likely that infected and non-infected stags can b e managed on the same property without transmission occurring between the g roups, provided that they do not come into direct contact with one another.