Seroprevalence of Q fever among metropolitan and non‐metropolitan blood donors in New South Wales and Queensland, 2014–2015

Abstract

Objectives To estimate the prevalence of exposure to the causative agent of Q fever (Coxiella burnetii) and of current infections among blood donors in Australia. Design, setting Cross‐sectional study in metropolitan Sydney and Brisbane, and in non‐metropolitan regions with high Q fever notification rates (Hunter New England in New South Wales; Toowoomba in Queensland). Participants Blood donors attending Red Cross collection centres during October 2014 – June 2015 who provided sera and completed a questionnaire on Q fever vaccination status, diagnosis and knowledge, and exposure history. Main outcome measures Age‐ and sex‐standardised seroprevalence of phase II IgG antibodies to C. burnetii (indicating past exposure) and independent risk factors for seropositivity; presence of C. burnetii DNA (indicating current infection and risk of transmission by blood transfusion). Results 2740 donors (94.5% response rate) completed the questionnaire and supplied sera for analysis. Crude antibody seroprevalence was 3.6%. Standardised seroprevalence was higher in non‐metropolitan than metropolitan regions (NSW, 3.7% v 2.8%; Queensland, 4.9% v 1.6%; statistically significant only in Queensland). Independent predictors of antibody seropositivity were regular contact with sheep, cattle, or goats (adjusted odds ratio [aOR], 5.3; 95% CI, 2.1–14), abattoir work (aOR, 2.2; 95% CI, 1.2–3.9), and assisting at an animal birth (aOR, 2.1; 95% CI, 1.2–3.6). Having lived in a rural area but having only rare or no contact with sheep, cattle or goats was itself a significant risk factor (v never lived rurally: aOR, 2.5; 95% CI, 1.1–5.9). 40% of people in groups recommended for vaccination were aware of the vaccine; 10% of people in these groups had been vaccinated. C. burnetii DNA was not detected in 1681 non‐metropolitan samples, suggesting that transmission by blood donation is unlikely. Conclusions Given their exposure to multiple risk factors, vaccination against Q fever should be considered for all rural residents.

Coxiella burnetiiseroprevalence in unvaccinated veterinary workers in Australia: Evidence to support Q fever vaccination

“…These associations are consistent with similar studies in veterinary populations around the globe (Abe et al, ; Bernard et al, ; Chang et al, ; Pozzo et al, ; de Rooij et al, ; Valencia et al., ; Van den Brom et al, ; Whitney et al, ), and the overall seroprevalence was similar to that of veterinarians in the United States (22.2%) (Whitney et al, ) and veterinary students in the Netherlands (18.7%) (de Rooij et al, ). These findings confirm that veterinary workers in Australia have an increased risk of exposure to C. burnetii compared to general populations, with previous studies reporting an overall seroprevalence of two to seven per cent for general populations in Queensland and New South Wales (Gidding et al, ; Islam et al, ; Tozer et al, ). The results additionally suggest that there may be a considerable proportion of unvaccinated veterinary workers that may be eligible for, and could benefit from, Q fever vaccination.…”

“…This study also confirms that veterinary workers who were predominantly exposed to non‐ruminant species and those in metropolitan areas remain at higher risk of C. burnetii , reporting 11% and 13% seroprevalence respectively. In comparison, general populations in Australia report a seroprevalence of two to five per cent in metropolitan areas (Gidding et al, ; Tozer et al, ). This is supported by reports of Q fever outbreaks associated with cat and dog births (Gibbons & White, ; Kopecny et al, ; Malo et al, ), Q fever disease among cat breeders (Shapiro, Norris, Bosward, & Heller, ), and the detection of C. burnetii in a large variety of domestic and wild animal species in Australia (Cooper, Barnes, Potter, Ketheesan, & Govana, ; Shapiro, Bosward, Heller, & Norris, ; Shapiro, Norris, Heller, & Bosward, ; Tozer et al, ).…”

“…Globally, the association of rurality with C. burnetii seroprevalence appears to vary and is influenced by land use, geography and seasonal conditions (Angelakis & Raoult, ; Cikman et al, ; Clark & Soares Magalhaes, ; Hackert et al, ; Tozer et al, ). In Australia, rural populations of New South Wales and Queensland report increased C. burnetii seroprevalence and Q fever disease notifications (Gidding et al, ; Islam et al, ; Lowbridge, Tobin, Seale, & Ferson, ; Tozer et al, ). Rural location may increase exposure to C. burnetii due to the proximity of farms, livestock facilities, and animal transport routes (Clark & Soares Magalhaes, ; O'connor, Tribe, & Givney, ).…”

“…Where a strong correlation (Spearman rank correlation coefficient >0.7; p < .05) was identified between variables, the variable with the least significant association with the outcome was excluded from multivariable modelling. Gender and age were included in multivariable modelling as confounders a priori due to previous Australian studies reporting increased seroprevalence with male gender and increasing age (Gidding et al, ; Islam, Ferguson, Givney, & Graves, ; Tozer, Lambert, Sloots, & Nissen, ). These were also included to account for bias in the cohort due to the exclusion of previously vaccinated workers that were proportionately likelier to be female and young.…”

Q fever: more common than we think, and what this means for prevention

“…Australia has one of the highest Q fever notification rates in the world. The article on seroprevalence data in this issue of the MJA reinforces the fact that Q fever is an infection of public health significance, and suggests that infections are more common than is recognised.…”