Outbreaks of abortions by Coxiella burnetii in small ruminant flocks and a longitudinal serological approach on archived bulk tank milk suggest Q fever emergence in Central Portugal

Abstract

Q fever is a worldwide zoonotic infectious disease caused by Coxiella burnetii and sheep and goats are known to be the main reservoir for human infection. This study describes the epidemiological and laboratory findings of C.burnetii outbreaks affecting sheep and goat flocks and also provides the results of a prospective serosurvey in bulk tank milk samples to assess C.burnetii circulation in a population of sheep living in close contact to the human population in Central Portugal. In the epizooties, C.burnetii was identified in tissues of the resulting abortions by qPCR. As for the serological survey, 10.2% (95%CI: 4.5-19.2) of the 78 bulk tank milk samples collected in 2015 presented IgG antibodies against C.burnetii. The same farms were visited and sampled in 2016 and 25.6% (95%CI: 16.4-36.8) were positive. This steep increase in the number of anti-C.burnetii farms between the 2015 and 2016 collections showed to be statistically significant (p=0.020) and is strongly suggestive of Q fever emergence in Central Portugal. Measures on animal health and on disease spread control to the human population should be considered.