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Q fever, caused by the bacterium Coxiella burnetii, is a very common disease in ruminant farming. It affects the reproductive performance of ruminants and is also a zoonosis that can cause severe health problems in humans. All scientists agree on the major role of aerial transmission in the spread of Coxiella burnetii between herds. However, the mechanisms involved in this process are poorly understood. We have explored them in order to better define measures to protect herds that are still free.

To this end, we monitored 95 Finistere dairy cattle herds over a one-year period and determined their infection status every 4 months. For each herd, and at each measurement time, we also knew the wind speed and direction, and an estimate of the level of contamination of neighbouring herds (number of Coxiella burnetii bacteria present in their environment and likely to be dispersed by the wind). We then showed that for a herd that was still free, the risk of airborne infection was increased if it was located in a windy area and if the herds in its vicinity, and located in the main wind direction, were heavily contaminated.

Wind therefore only has an impact if there are nearby sources of contamination. To control this risk, it is necessary to implement measures to reduce the prevalence of infection in herds. Thus, in a windy area with a high frequency of infection, vaccination of animals appears to be indicated to protect herds that are still free.

This study was carried out as part of the Investissement d'Avenir ANR-10-BINF-07 (MIHMES) project, coordinated by P. Ezanno of UMR BIOEPAR (Oniris-Inra), in partnership with the Groupements de Défense Sanitaire de Bretagne.

Contact : François Beaudeau, UMR Oniris-INRA BioEpAR, francois.beaudeau@oniris-nantes.fr

Related publication

Nusinovici, S., Hoch, T., Brahim, M. L., Joly, A., Beaudeau, F. (2015). The effect of wind on Coxiella burnetii transmission between cattle herds: a mechanistic approach. Transboundary and Emerging Diseases. http://dx.doi.org/10.1111/tbed.12423