Seroprevalence of Q fever in naturally infected dairy cattle herds and implications for within-herd control

Coxiella burnetii is the causal agent of Q fever, a worldwide spread zoonosis. Prevention of Coxiella burnetii shedding in cattle is a critical point for controlling the spread of the pathogen between animals, and from animals to human. Hygienicmeasures are classically implemented, but their relative impact on Coxiella burnetii diffusion remains unknown. Vaccination with a phase 1 vaccine has been shown to be effective to prevent shedding in susceptible animals, even in infected cattle herds, making pivotal to identify them prior to vaccination. Thus, the objectives of this study were to describe thedistribution of within-herd apparent seroprevalence among cows and nulliparous females and to explore the association of management practices and herd characteristics with these seroprevalence. The study was conducted through a cross-sectional design in 100 naturally infected cattle dairy herds. While nulliparous females were found quite systematically susceptible (median prevalence = 0.01), a high value and variability were observed in cows (median prevalence = 0.42). Only a few herd characteristics and management practices were found to be related tohigher seroprevalence (number of cows < 46, seasonal calving, abortion products not systematically removed, and contact through the fence with other ruminants). Our findings support, in addition to classically recommended hygienic measures, the relevance to target nulliparous females for vaccination to control the spread of Coxiella burnetii within an infected herd given there quite systematically susceptible status.