Q fever seroprevalence in Australia suggests one in twenty people have been exposed

Abstract

Q fever (caused by Coxiella burnetii) is thought to have an almost world-wide distribution, but few countries have conducted national serosurveys. We measured Q fever seroprevalence using residual sera from diagnostic laboratories across Australia. Individuals aged 1–79 years in 2012–2013 were sampled to be proportional to the population distribution by region, distance from metropolitan areas and gender. A 1/50 serum dilution was tested for the Phase II IgG antibody against C. burnetii by indirect immunofluorescence. We calculated crude seroprevalence estimates by age group and gender, as well as age standardised national and metropolitan/non-metropolitan seroprevalence estimates. Of 2785 sera, 99 tested positive. Age standardised seroprevalence was 5.6% (95% confidence interval (CI 4.5%–6.8%), and similar in metropolitan (5.5%; 95% CI 4.1%–6.9%) and non-metropolitan regions (6.0%; 95%CI 4.0%–8.0%). More males were seropositive (6.9%; 95% CI 5.2%–8.6%) than females (4.2%; 95% CI 2.9%–5.5%) with peak seroprevalence at 50–59 years (9.2%; 95% CI 5.2%–13.3%). Q fever seroprevalence for Australia was higher than expected (especially in metropolitan regions) and higher than estimates from the Netherlands (2.4%; pre-outbreak) and US (3.1%), but lower than for Northern Ireland (12.8%). Robust country-specific seroprevalence estimates, with detailed exposure data, are required to better understand who is at risk and the need for preventive measures.

National Seroprevalence of Coxiella burnetii in Chile, 2016–2017

“…Our findings suggest that Q fever was endemic to Chile before the documented outbreak of atypical pneumonia associated with C. burnetii infection reported in July 2017 in the three southern regions (La Araucanía, Los Ríos and Los Lagos) of the country [ 22 ]. Similar national seroprevalence levels were previously reported in the USA (3.1%) [ 14 ] and in The Netherlands (2.4%) [ 12 ], but lower than Australia (5.6%) [ 13 ]. Analysis of the characteristics of Chilean C. burnetii seropositive individuals revealed that seropositivity in the ≥65 years of age group was significantly higher than younger age groups.…”

“…In the Netherlands, home to the largest outbreak of documented Q fever among a human population between 2007 and 2010 [ 11 ], a seroprevalence of 2.4% ( n = 5654) was reported pre-outbreak [ 12 ]. Similar seroprevalence levels have been reported in Australia 5.6% ( n = 2785) [ 13 ], USA 3.1% ( n = 4437) [ 14 ] and Bhutan 6.9% ( n = 864) [ 15 ]. An exception to these studies are Northern Ireland, with 12.8% ( n = 2394) [ 16 ] and Cyprus a 52.7% ( n = 583) [ 17 ].…”

“…The reported linear increase in seropositivity to C. burnetii from the 24–44 year group onwards is consistent with the data from other national surveys in the Netherlands and USA surveys where similar linear increases in seropositivity with a peak in the older age groups [ 12 , 14 ]. The exception to this observation is the recently published Australian survey where C. burnetii seropositivity peaked in the middle years (50–59 years) before declining again in the older age groups [ 13 ]. Probably, the linear increase is due to accumulated exposure over the lifetime.…”

Coxiella burnetii seroprevalence and Q fever in Australian wildlife rehabilitators

“…We report an overall seroprevalence for this cohort of 6.1%, which is 70% greater than the recently reported 3.6% in an Australian study of Red Cross blood donors from non-metropolitan NSW and QLD (using the same laboratory techniques as the current study) [ 30 ]. Two other Australian studies (also employing the same laboratory methods as the current study), have reported higher general population C. burnetii seroprevalence: Islam et al [ 39 ] estimated an overall seroprevalence of 7% in the Hunter New England region of NSW, and more recently Gidding et al [ 31 ] reported a 5.6% nationwide C. burnetii seroprevalence, however these two studies used archived sera that were opportunistically obtained from pathology laboratories. We believe that the Red Cross blood donor study is a closer approximation to the assumed healthy participants in the current study, as blood donors must be of good general health and meet specific eligibility criteria to donate blood [ 7 ].…”

Particle Based Model for Airborne Disease Transmission

“…While this latter survey was not nationally representative, 16% (2,039) of the 12,821 specimens tested were positive for Coxiella [255]. Finally, serological analysis of stored sera from population-based epidemiology studies and medical diagnostic laboratory testing shows Coxiella burnetti infection prevalence rates in other countries is similar to those seen in the United States (Netherlands 2.4%; Australia 5.6%) [260], [261].…”