Assessment of Animal Characteristics and Management Risk Factors Associated with Coxiella burnetii Seroprevalence among Sheep in the United States, 2011

Coxiella burnetii (C. burnetii) is a zoonotic bacteria that can cause abortion storms or mild clinical signs in sheep, goats, and other livestock. It poses a zoonotic health risk to humans in contact with infected farm animals, such as animal caretakers, farmers, researchers, abattoir workers, and veterinarians, causing mild to severe flu-like symptoms during acute disease, with less than 5 percent developing a chronic disease such as endocarditis. Most significantly for large-scale outbreaks, it can also be widely transmitted to humans via wind particles carried from an infected premises or via casual contact with sub-clinically affected animals, such as in petting zoos. The U.S. Department of Agriculture’s National Animal Health Monitoring System (NAHMS) Sheep 2011 survey collected a wide range of information from a representative sample of U.S. sheep producers, including information on management, health, and biosecurity practices. Additionally, biologic sampling occurred on a subset of premises to evaluate the prevalence of organisms of concern to the industry, including C. burnetii. The purpose of the current evaluation was to combine the C. burnetii results from biologic sample testing with data collected in the general management questionnaire to gain a better understanding of seroprevalence levels and identify management practices that increase C. burnetii risk in U.S. sheep. Univariate and multivariate data analyses evaluated individual animal and flock level characteristics associated with seropositive animals and flocks in the U.S., such as flock management practices, breeding practices, reproductive outcomes, and health/biosecurity practices. Further univariate and multivariate analyses looked for potential effect-modifying practices or flock characteristics associated with C. burnetii presence at the flock level. The findings of the current report suggest that the greatest management factors associated with a positive flock status are culling animals at a younger age and being a flock located in the Central region. The higher risk in the Central region for sheep operations geographically aligns closely with the locations where many of the incident human cases in the U.S. occur, indicating that practitioners in this region should ask about possible exposure to livestock when patients present for flu-like symptoms. Producers should consider the source of their replacement animals to decrease the likelihood of bringing infected animals onto the operation by purchasing younger cull animals. This could help decrease the number of positive flocks and thus decrease the risk to human health