Q fever: a disease with underappreciated significance?

Q fever prevalence and significance are potentially underappreciated in the UK and other countries such as France, Italy and Germany. Although its impact should generally be regarded appropriately as lower than acknowledged major infectious causes of ruminant infertility such as bovine viral diarrhoea virus (BVDv) or bovine herpesvirus-1 (BoHV-1), it may not be recognised as significant at all because of poor disease surveillance. Velasova et al (2017) reviewed the herd-level prevalence of selected endemic infectious diseases of dairy cows in Great Britain and although approaching 80% of surveyed herds were seropositive for Coxiella burnetii, only 1–2% of farmers believed that the disease was present on their farm and 0% perceived that the disease was a problem.

Q fever is a zoonotic disease caused by C. burnetii, a bacterium found worldwide in a wide range of animals. The term ‘Q fever’ (for query fever) was proposed in 1937 by Edward Holbrook Derrick to describe febrile illnesses in abattoir workers in Brisbane, Queensland, Australia, where it remains a zoonosis of significance. Since 2007, Q fever has been emerging as a public health problem in several parts of Europe, with a high profile outbreak in the Netherlands (Hermans et al, 2014), as well as increased recognition as a consequence of more robust screening. Although Q fever is asymptomatic in 60% of human cases, it can lead to acute or chronic infections and cause a flu-like syndrome, hepatitis, pneumonia, endocarditis or abortions. In ruminants, C. burnetii may be the cause of abortions, infertility, metritis or chronic mastitis for the infected herds. However, how well recognised is this risk of economic losses and reduced sustainability of production (Cabrera, 2014)? Diagnosis of infertility, including pregnancy loss in cattle and other ruminants, is complex. The diagnostic rate achieved for abortions is generally low, averaging at about 35% of cases where a foetus and placenta are submitted for an abortion investigation; in cattle, there is frequently a delay between fetal death and expulsion (Cabell, 2007). The need for disease mitigation, including reproductive losses, is recognised as an important part of an approach to sustainable herd health (Statham et al, 2017).