[Detection of Coxiella burnetii in the air of a sheep barn during shearing].

Local epidemics of Q fever occur sporadically in Germany, mainly in rural residential communities. There is increasing evidence that these outbreaks, which are caused by Coxiella burnetii, are related particularly to the lambing season and shearing periods of nearby sheep holdings. It is assumed that this zoonotic agent is massively emitted from the placenta of infected ewes at birth and during shearing of wool contaminated with infected faeces of ticks. However, little is known about the airborne transmission and travel distance of this infectious agent, and only few attempts have been made to isolate it directly from the air. This paper describes for the first time the isolation and detection of C. burnetii in the air of an enclosed sheep barn during shearing of a herd which had tested positive for C. burnetii serologically and by PCR. Samples of inhalable dust samples were taken using I.O.M. samplers with glass fibre and polycarbonate filters at a flow rate of 2.5 l/min. The sampling time was nearly 4.5 h. Two sampling positions were set up on both sides of the shearing place at a distance of 3 m and 1.5 m above the ground. A third position with the same sampling equipment was not activated and served as a sampling and transport control. In the laboratory, the glass fibre filters were used to determine the dust concentration. The polycarbonate filters were treated in a specific breakdown procedure which inactivates PCR inhibitors, followed by amplification and sequencing of a specific DNA section of C. burnetii, which was found in the dust from both active sampling positions. The investigation clearly shows that the sampling and detection methods used in this small field study are suitable for the detection of C. burnetii in the air of sheep barns. The results confirm experimentally the high risk of airborne transmission of C. burnetii from sero-positive sheep herds during shearing. However, little is known about the effective travel distance of infective airborne C. burnetii particles. There is an urgent need for more detailed investigations on the emission and airborne dispersion of infectious C. burnetii particles in order to improve our understanding of the health risks caused by this zoonotic agent originating from sheep herds.