Seroprevlance of Coxiella burnetii among abattoir and slaughterhouse workers: A meta-analysis

Q fever caused by the gram negative bacteria, Coxiella burnetii, is an occupational hazard for those who live and work in rural settings and those who are in contact with animals, especially abattoir and slaughterhouse workers. Australia is the only country to register a vaccine to prevent Q fever (Q-vax®, Seqirus, Australia) that is used in high risk populations. Seroprevalence studies conducted to determine the burden of Q fever (C. burnetii infection) in different settings have demonstrated high levels of heterogeneity with estimates of the percent positive ranging from 30% to 70%. There is a need for a more systematic evaluation of the findings of these studies in order to provide summary estimates of the seroprevalence in different settings. We searched for published articles using PubMed, MEDLINE-EMBASE, and Scopus databases using search terms obtained from an initial review of published reports of recent Q fever outbreaks. Data on the seroprevalence of C. burnetii infection (Q fever) was extracted from the selected studies and a random effects meta-analysis was performed with stratification by outbreak status, year, country and serological techniques used. Results were visualised with a forest plot with 95% CI and measures of heterogeneity (I(2)) for the random effects model. A total of 19 articles that met the search criteria were included. The reported seroprevalence rate ranged from 4.7% to 91.7% among abattoir and slaughterhouse workers. No inter-group heterogeneity was observed (p = 0.956), supporting the pooling of all studies into one pooled measure. The pooled estimate of seropositivity for C. burnetii infection in people working in abattoirs and slaughterhouses was 26% (95% CI: 18–35%) regardless of the evidence of an “outbreak”, the time of year or country. Seropositivity for C burnetii was independent of a person's age and years of occupational experience. Within abattoirs and slaughterhouses, slaughtering of cattle, sheep and goats are the most important risk factors associated with seropositivity and for those who showed over symptoms upon infection. We recommend that vaccination programmes are directed towards people employed in the meat processing industry to mitigate the significant health and economic impacts of Q fever.