Emerg Infect DisEmerging Infect. DisEIDEmerging Infectious Diseases1080-60401080-6059Centers for Disease Control and Prevention22172399331120910-178610.3201/eid1712.101786Letters to the EditorQ Fever in Woolsorters, BelgiumQ fever in Woolsorters, BelgiumWattiauPierreBoldisovaEvaTomanRudolfVan EsbroeckMarjanQuoilinSophieHammadiSamiaTissot-DupontHervéRaoultDidierHenkinbrantJean-MarieVan HesscheMiekeFretinDavidVeterinary and Agrochemical Research Centre, Brussels, Belgium (P. Wattiau, M. Van Hessche, D. Fretin);Slovak Academy of Sciences, Bratislava, Slovakia (E. Boldisova, R. Toman);Institute of Tropical Medicine, Antwerp, Belgium (M. Van Esbroeck);Institute of Public Health, Brussels (S. Quoilin, S. Hammadi);Université de la Méditerranée, Marseille, France (H. Tissot-Dupont, D. Raoult);Occupational Health Medicine Group Provikmo, Verviers, Belgium (J.-M. Henkinbrant)Address for correspondence: Pierre Wattiau, Veterinary and Agrochemical Research Centre, Bacterial Diseases, Groeselenbergstr. 99, Brussels B-1180, Belgium; email: piwat@var.fgov.be122011171223682369Keywords: Q feverCoxiella burnetiibacteriaseroprevalencewoolsorterszoonosesBelgium

To the Editor: Recent outbreaks of Q fever in the Netherlands and the United Kingdom raised public awareness about this ubiquitous bacterial disease known for decades to circulate worldwide (14). The disease, which ranges from a self-recovering influenza-like illness to pneumonia and severe meningoencephalitis, myocarditis, or endocarditis, is usually transmitted from animals to humans by airborne particles derived from contaminated feces and birth products. Clinical symptoms develop in only ≈40% of infected humans (1). In ≈1%–2% of these persons, symptoms evolve toward the chronic form of the disease, which can be life-threatening (5).

Q fever seroprevalence in the general population in Europe ranges from 2.4% to >30% in some countries in the Mediterranean region (5). Despite improved awareness during the past 3 years and geographic proximity with the Netherlands, few human cases were reported in Belgium (14, 27, and 33 cases in 2007, 2008, and 2009, respectively) (6). A retrospective survey of blood donors in the Netherlands showed a seroprevalence of 2.4% before the start of outbreaks (7). In France, the prevalence of the disease in the Nord-Pas-de-Calais region bordering Belgium is low and accounts for only 0.5% of Q fever cases in France (8). Seroprevalence of the general population in Belgium, although unknown, is thus probably comparable with that in neighboring countries in absence of outbreaks and is not expected to exceed 5%.

We report a serologic, epidemiologic, and microbiological Q fever survey conducted in a scouring factory that processed wool and goat hair products in Belgium. No acute Q fever episodes were previously reported by the factory workers. Data on clinical symptoms and risk factors were obtained in face-to-face interviews, and associations with seropositivity were explored by using regression analysis. Airborne dust collected inside the factory during goat hair processing (9) contained 102–103 genome equivalents of Coxiella burnetii, the Q fever agent, per liter of air as estimated by real-time PCR (Laboratoire Service International, Lissieu, France) (Table A1). Sheep wool processing generated less dust and resulted in a C. burnetii air load that never reached 10 genome equivalents/L in our analyses. No information is available about the infectivity or viability of air-suspended C. burnetii in the studied environment.

Q fever serologic analysis was conducted by using an in-house ELISA for serum samples from 69 workers obtained annually during 2007–2009. Results of samples from the third year were confirmed in parallel by using an immunofluorescent assay (IFA) (Focus Diagnostics, Cypress, CA, USA) in the reference laboratory in Belgium and with follow-up samples in cases of noninterpretable or suspected serologic profiles. The 3-year cumulative seroprevalence was 50.7% (Table). This high value likely results from occupational exposure inside the factory. However, one cannot exclude that characteristics such as traveling abroad, farming, or living near farm animals might account for part of the seroprevalence. Nevertheless, such characteristics could not be associated with positive serologic results in our epidemiologic analysis.

The serologic status of 2 workers (T3 and T42) was compatible with ongoing chronic Q fever as assessed by IFA and ELISA (Table). Another IFA conducted in the reference laboratory in France confirmed a serologic status compatible with chronic Q fever for worker T3 and detected anti–phase I and II IgA in this worker. However, chronic status was not confirmed for worker T42 by this laboratory (Table A1).

Profiles of other workers in the cohort were characterized by increased anti–phase II IgG, IgM, or both (9/69, 13%) over a 2-year period. These profiles suggest relapse and may result from continuous exposure to the Q fever agent, which led to reinfection or repeated stimulation of the immune response. Molecular testing did not detect C. burnetii DNA in any blood sample, and clinical examinations did not detect endocarditis in worker T3 as analyzed by positron emission tomography and transthoracic and transesophagian echocardiography. However, infection of tissues other than the heart in this worker cannot be ruled out.

Our results indicate high seroprevalence of Q fever among workers at the scouring factory studied. Continuous exposure to the Q fever agent was the likely cause of atypical antibody responses evoking a chronic or relapsing disease in the absence of any clinical symptom. These results indicated the need to analyze paired serum samples and to rely on medical follow-up before establishing a definitive diagnosis.

Given the continuous occupational risk to which these workers are exposed, hiring of pregnant women or persons with underlying medical conditions, such as valvulopathy or immunologic depression, should be avoided. Moreover, annual serologic testing should be conducted on all exposed persons to detect any evolution toward the chronic form of the disease, which can be life-threatening. Although less dangerous than anthrax, Q fever is still a highly prevalent occupational disease that affects persons working with animal hairs in industrial environments and commonly referred to as woolsorters (10).

Serologic results for Q fever in woolsorters, Belgium, 2007–2009*
Serologic statusELISA† (years 1–3)IFA‡ (year 3)Confirmed§ (years 1–3)
No. negative292734
No. nonspecifically reactiveNA9NA
No. with past infection313126
No. with recent or active infection7NA8
No. with chronic infection221
% Seroreactive57.947.850.7

*IFA, immunofluorescent assay; NA, not applicable.
†Conducted on samples collected annually for 3 y. Serologic titer for chronic Q fever: phase I IgG >12,800 and > phase II IgG; for recent or active infection, phase II IgG >1,600 and phase II IgM >800; for past infections, phase II IgG >1,600 and phase II IgM <800.
‡Conducted on paired samples in cases of suspected or noninterpretable initial results; conducted on single samples in all other cases. Serologic status was defined at year 3 according to the instructions of the test kit manufacturer (Focus Diagnostics, Cypress, CA, USA).
§Workers with test results above the threshold at least once over a 3-y period by ELISA and IFA. Serologic status was adjusted on the basis of the 3-y projection and retesting in the reference laboratory in France.

Suggested citation for this article: Wattiau P, Boldisova E, Toman R, Van Esbroeck M, Quoilin S, Hammadi S, et al. Q fever in woolsorters, Belgium [letter]. Emerg Infect Dis [serial on the Internet]. 2011 Dec [date cited]. http://dx.doi.org/10.3201/eid1712.101786

Acknowledgments

We thank the factory workers for participating in the study and S. Malbrecq for assistance with real-time PCRs.

This study was supported by the Occupational Medicine group Provikmo, the Veterinary and Agro-chemical Research Centre, the Slovak Ministry of Education (grant no. 2/0127/10), and the Slovak Academy of Sciences.

<italic>Coxiella burnetii</italic> TaqVet quantitative real-time PCR kit results, Belgium, 2007–2009*
Material processedOriginBatch no.ResultCtC. burnetii concentration, GenEq/mg
Goat hairAfghanistan and Russia07/13528 1.1A+30.0103–104
Goat hairAfghanistan and Russia07/13528 1.1B+29.0103104
Goat hairAfghanistan and Russia07/13528 1.1C+28.5103–104
Goat hairAfghanistan06/11664.5+27.0103–104
Goat hairAsia08/703.4+27.0103–104
Goat hairAsia08/703.4 4B+28.5103–104
Goat hairAsia08/703.4 4C+27.0103–104
WoolThe Netherlands33945+34.0<102
WoolFrance and the Netherlands33961+34.0<102
WoolItaly33944+36.0<102
WoolHungary33954>40<10
WoolFrance and Switzerland33935+36.0<102

*DNA was extracted by using the QIAamp DNA Stool Mini Kit (QIAGEN, Valencia, CA, USA) from 20-mg of airborne dust samples suspended in 0.5 mL of MiliQ water (Millipore, Billerica, MA, USA). PCR (Laboratoire Service International, Lissieu, France) was conducted according to the manufacturer’s instructions. Ct, cycle threshold; GenEq, genome equivalents; +, positive; –, negative.

ReferencesMaurin M, Raoult D. Q fever. Clin Microbiol Rev. 1999;12:5185310515901Schimmer B, Morroy G, Dijkstra F, Schneeberger PM, Weers-Pothoff G, Timen A, Large ongoing Q fever outbreak in the south of the Netherlands, 2008. Euro Surveill. 2008;13. pi: 18939.Wallensten A, Moore P, Webster H, Johnson C, van der Burgt G, Pritchard G, Q fever outbreak in Cheltenham, United Kingdom, in 2007 and the use of dispersion modelling to investigate the possibility of airborne spread. Euro Surveill. 2010; 15. pii: 19521.Wilson LE, Couper S, Prempeh H, Young D, Pollock KG, Stewart WC, Investigation of a Q fever outbreak in a Scottish co-located slaughterhouse and cutting plant. Zoonoses Public Health. 2010;57:4938 10.1111/j.1863-2378.2009.01251.x19912614European Centre for Disease Prevention and Control. Risk assessment on Q fever, 2010 [cited 2011 Jun 16]. http://www.ecdc.europa.eu/en/publications/Publications/1005_TER_Risk_Assessment_Qfever.pdfWorking Group on Foodborne Infections and Intoxications. Trends and sources. Report on zoonotic agents in Belgium, 2011 [cited 2011 Jun 16]. http://www.afsca.be/publicationsthematiques/_documents/2008-2009_Report-on-zoonotic-agents_en.pdfSchimmer B, Notermans DW, Harms MG, Reimerink JH, Bakker J, Schneeberger P, Low seroprevalence of Q fever in the Netherlands prior to a series of large outbreaks. Epidemiol Infect. 2011;▪▪▪:19 .10.1017/S095026881100013621324217Frankel D, Richet H, Renvoisé E, Raoult D. Q fever in France, 1985–2009. Emerg Infect Dis. 2011;17:350621392423Wattiau P, Klee SR, Fretin D, Van Hessche M, Menart M, Franz T, Occurrence and genetic diversity of Bacillus anthracis strains isolated in an active wool-cleaning factory. Appl Environ Microbiol. 2008;74:400511 10.1128/AEM.00417-0818487406Wattiau P, Govaerts M, Frangoulidis D, Fretin D, Kissling E, Van Hessche M, Immunologic response of unvaccinated workers exposed to anthrax, Belgium. Emerg Infect Dis. 2009;15:16374019861061