Introduction

The faecal oral route is considered to be the main mode of paratuberculosis transmission in livestock. Infected rabbits excrete Mycobacterium avium subsp. paratuberculosis (Map) in their faeces, leading to the potential for inter-species transmission via the faecal-oral route. Two grazing experiments were carried out to quantify the rate of ingestion of rabbit faecal pellets by grazing livestock and determine the effects of sward height on this rate and therefore estimate the risk of paratuberculosis transmission from rabbits to livestock.

Methods

Ten lambs and ten calves were each presented with three replicates of nine sward treatments, created through three sward heights and three densities of rabbit faeces and allowed to graze for short periods.

Results

Overall, calves ingested 1.27% and sheep 0.472% of the rabbit faecal pellets presented to them. Cattle showed no behavioural avoidance of rabbit faeces while grazing. Sward characteristics affected the probability and rate of ingestion of faeces and thus Map. Level of faecal contamination affected the proportion of pellets ingested by sheep, and the probability of cattle ingesting one or more faecal pellets. Shorter swards lead to increased ingestion by cattle but not sheep.

Discussion

As cattle show no behavioural avoidance of rabbit faecal pellets their rate of ingestion is proportional to the level of environmental contamination and thus rabbit density. These rates of ingestion equate to ingestion of up to 3700 rabbit faecal pellets per hectare grazed by calves and 1400/ha grazed by sheep. Sheep are better able to avoid rabbit faeces while grazing. Rabbits should not be discounted as a possible source of paratuberculosis infection.