Pesquisa de Coxiella burnetii, agente etiológico da febre Q, em amostras de soro de pacientes com suspeita de dengue no estado de Minas Gerais, Brasil: uma doença negligenciada

Abstract

Introduction: Q fever is a zoonosis of worldwide distribution caused by the pathogen Coxiella burnetii, a bacterium that, besides presenting resistance and environmental stability, is one of the most infectious agents to human beings. Its main form of transmission to human population occurs through the inhalation of aerosols contaminated with products from infected animals, mainly cattle, goats and sheep. Human infection has a wide spectrum of manifestations, from asymptomatic cases to serious and fatal complications. As it presents a clinical picture similar to dengue in the acute phase, associated with its lack of knowledge on the part of health professionals, cases of Q fever may be mistakenly diagnosed and treated as dengue. This fact which increases the costs of the public health system, as well as the risk of the occurrence chronic Q fever, especially in patients with heart valve injury and immunocompromised. Objective: Investigate the prevalence of Q fever in suspected cases of dengue in Minas Gerais, investigate its seroprevalence, evaluate the factors associated with this zoonosis, describe the epidemiological profile of patients and compare the ELISA method against the gold standard method of Q fever diagnosis, Indirect Immunofluorescence (IFI). Methodology: 437 serum unique samples from patients with suspected dengue were selected, collected between one and ten days of symptoms, from different municipalities of Minas Gerais, sent to the Ezequiel Dias Foundation in the period between January 2017 and August 2018 for diagnosis dengue and that presented negative result. The tests performed to investigate C. burnetii (Q fever) were: Real-Time Polymerase Chain Reaction (qPCR), Indirect Immunofluorescence and ELISA. This is a cross-sectional study of prevalence. The results found were analyzed using descriptive statistics. Results: Was not detected the DNA from C. burnetii in any of the 437 serum samples analyzed by the qPCR method. By the IFI method, 25 samples (5.72%) were reactive for at least one class of antibodies anti-C. burnetii and showed antibody titers below the cutoff to consider Q fever active. The mesoregion Metropolitan of Belo Horizonte concentrates most of these reactive patients. To investigating the associated factors, the cattle represented more than 80% in relation to the sum of the head of cattle, goat and sheep of the municipalities that presented reactive patients. The analysis of the parameter “zone (area) of housing”, of the epidemiological profile of reactive patients, showed that 12.50% and 5.19% of patients residing in rural and urban areas, respectively, were reactive. The sensitivity, in a general analysis, of the ELISA method was 13.04%, while the specificity was 98.55%. Conclusion: These results indicate that 5.72% of the patients had previous exposure to the causative agent of Q fever and that living in the countryside increases the chances of such exposure. In addition, they demonstrate that this pathogen has circulation in humans in the state of Minas Gerais. Among the main animals related to the transmission of C. burnetii to humans, cattle were the main associated factor. The ELISA method employed is not indicated as a screening method for the serological diagnosis of Q fever, and can be used as a confirmatory method if any negative result obtained by another method is doubtful. Finally, the inclusion of Q fever as a compulsory notification disease in humans and the joint action of the human health and animal health sectors in the coping against this zoonosis, in a "One Health" perspective, will contribute to the Q fever to stop neglected and be better investigated in Brazil, thus reducing the damage caused by it.