engleski

Human seroprevalence of Coxiella burnetii in Croatia 2013-2017 and importance of serological follow-up

Introduction Q fever (QF), zoonosis caused by intracellular bacteria Coxiella burnetii, is a reportable disease in Croatia from 1954. Main reservoirs are domestic ruminants. Acute QF mainly acquired by aerosol inhalation can be symptomatic and asymptomatic with ability to progress to persistent localized or chronic infection. The aim of the study is to describe Q fever prevalence in Croatia in five-year period and to emphasize significance of follow-up of patients with anti- phase I antigen. Methods From 2013 to 2017 anti- C.burnetii was tested in 2051 sera out of 1763 patients with pneumonia. All samples were tested with IgM and IgG anti-phase II and the positive ones were further tested with IgG and IgA anti- phase I enzyme immunoassay (ELISA ; Virion/Serion, Germany). The criteria for establishing the diagnosis of acute QF infection were: anti-phase II antibody seroconversion, IgM positive or both IgM and IgG positive. Only anti-phase II IgG positive were considered as past QF infection. Positive anti-phase I antibody without IgM was interpreted as possible chronic / persistent QF and clinicians were suggested to send paired serum and observe clinical risk factors for C.burnetii progression. Results Acute QF was diagnosed in 170 (9.6%) patients. Past QF was found in 46 (2.6%). Anti-phase I as suspected persistent infection was detected in 19 (1.1%) patients. Median age was 48 years. Acute QF was diagnosed mainly in 31 to 60 year olds (126 ; 74.1%). Anti-phase II IgG patients increase with age. Males with anti- C.burnetii predominate (p=0.002 ; male to female ratio 3:1). The number of acute QF-patients ranges from 28 in 2015 to 43 in 2013. QF patients were mainly from coastal region (80/442, 18.1% of tested patients). Only 263 (14.9%) patients had paired sera and out of them 28 (10.6%) seroconverted. Conclusion Coxiella burnetii infection is significant cause of pneumonia in Croatia. Diagnosis of Q fever is made by serology and due to probable slow seroconversion consecutive serum is mandatory. Serological QF follow-up and careful interpretation of results according to clinical data is important. Due to current recommendation for screening of all patients with QF to recognize possible risk factors for progression to persistent infection, serological testing, especially anti-phase I, needs to be followed-up.

human seroprevalence ; Coxiella burnetii ; Croatia 2013-2017

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