Q fever in Brazil: assessment of capybara and tick exposure to Coxiella burnetii in anthropogenic and natural areas and epidemiological investigation of the first known clinical case in the Amazon region

• Ano de defesa: 2025
• Autor(a) principal: Silito, Igor Silva
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Coxiella burnetii; Capivaras; Capybaras; Carrapatos; Coxiellosis; Coxielose; Febre Q; Q Fever; Ticks
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/10/10134/tde-24102025-181524/

The bacterium Coxiella burnetii, responsible for causing Q fever in humans and coxiellosis in animals, is globally distributed, with the exception of New Zealand. However, in Brazil, it is little known, and the number of reported cases in humans and animals is certainly underestimated, being considered an important neglected zoonosis. Transmission of this bacterium occurs mainly through the inhalation of spore-like forms present in aerosols, with domestic ruminants (cattle, sheep and goats) considered the main hosts. However, the role of wild animals in the disease cycle remains poorly understood. The present study aimed to assess the natural exposure of capybaras to C. burnetii through serological and molecular analyses of samples collected from both anthropized and natural areas in municipalities of São Paulo, the Pantanal region of Mato Grosso and Mato Grosso do Sul and in Maranhão, Brazil. Ticks collected in these same regions were also analyzed. In total, 458 capybara serum samples were tested against C. burnetii antigens, and 343 ticks were processed for C. burnetii DNA detection. Although all molecular assays yielded negative results, serological analyses revealed prevalence rates of 40.25% in anthropized areas and 30.0% in natural areas. Another objective of this study was to evaluate, through an epidemiological investigation, a rural property located in Belterra, Pará, Brazil, where a recent human case of Q fever occurred, considered the first recognized in the Amazon region. After the clinical confirmation of chronic Q fever in the patient, blood samples were collected from 2 dogs, 5 cattle, 2 horses, and 22 goats living on the rural property, as well as ticks found on cattle and horses (46 in total). Based on serological and molecular analyses, two dogs and three goats tested seropositive for C. burnetii, demonstrating their roles as sentinels and potential reservoirs and environmental spreaders. The results of this study contribute to a better understanding of the ecology of hosts, ticks, and C. burnetii under natural and anthropogenic environmental conditions and how human activities can affect the distribution of this important pathogen.