Title : Could we be missing chronic Q fever endocarditis? The case for targeted screening in Australian aortic valve replacement patients

Background: Rates of aortic valve replacement (AVR) in Australia have increased substantially over the past two decades, driven by an ageing population and expanding access to surgical AVR (SAVR) and transcatheter aortic valve implantation (TAVI). Q fever, caused by Coxiella burnetii, remains endemic in Australia, with increasing notification rates and a predominance among older males with prolonged rural exposure. Chronic Q fever is a recognised cause of culture-negative infective endocarditis and is associated with underlying valvular heart disease and prosthetic valves. However, the prevalence of chronic Q fever endocarditis among Australian patients undergoing AVR remains unknown.

Case: A 68-year-old retired truck-driver underwent SAVR for native valve severe aortic stenosis. He had no known history of Q fever and no pre-operative suspicion of chronic Q fever infection. Intra-operatively, the native aortic valve appeared macroscopically abnormal and was sent for C. burnetii polymerase chain reaction (PCR) testing. Valve tissue PCR subsequently confirmed chronic Q fever infection. On being questioned further after this diagnosis, it was found he and his family had lived in a rural town around 25 years previously where he worked on a local mixed livestock farm and had moved to the city when he started to drive trucks. This diagnosis would likely have been missed had tissue not been submitted for molecular testing, highlighting the potential for occult chronic Q fever in patients undergoing valve surgery, particularly those with significant rural exposure.

Discussion: The estimated total private cost (inclusive of hospital fees, specialist fees, theatre costs, heart valve prosthesis, pre- and post-procedure investigations, after-care) of primary AVR ranges from AUD $45,000–$78,000, while re-do AVR may cost AUD $38,000–$70,000 or more and is associated with increased perioperative morbidity and mortality compared with first time valve replacement. In contrast, under the Australian Medicare Benefits Schedule Q fever serology costs AUD $15.65 and C.burnetii PCR testing of excised valve tissue costs AUD $28.65. Given the low cost of testing relative to valve replacement procedures, targeted screening of high-risk patients - particularly older males with significant rural exposure and known valvulopathy - may represent a costeffective strategy. Practical implementation could include pre-operative questionnaires, serology for high-risk patients and routine PCR test of excised valve tissue.

Conclusions: This case highlights the potential for undiagnosed chronic Q fever among patients undergoing first-time AVR in Australia. As AVR numbers continue to rise in Australia, defining the burden of chronic Q fever endocarditis in patients with valvular disease is increasingly important. Targeted screening strategies may offer substantial clinical and economic benefits by identifying occult infection before prosthetic valve failure and the need for high-risk re-do surgery.

Dr Carolyn Jack is currently undertaking Infectious Diseases Advanced Training in Sydney, Australia, on a background of working in rural Australian communities after separation from the Royal Australian Air Force as a Squadron Leader in 2016. She holds a Master of Public Health and Tropical Medicine from James Cook University and a Master of Medicine (Infection and Immunity) from The University of Sydney, and has a special interest in One Health issues that affect rural communities worldwide focusing on zoonotic and parasitic diseases.