Risk factors associated with the transmissionof Brazilian spotted fever in the Piracicaba river basin, State of São Paulo, Brazil

Abstract

Introduction: Brazilian spotted fever (BSF) is a disease transmitted by ticks for which the etiological agent is Rickettsia rickettsii. The present essay evaluates the risk factors associated with the transmission of cases of BSF in the time period between 2003 and 2013 in the Piracicaba river basin, state of São Paulo. Methods: This essay presents a retrospective study to identify the factors associated with the transmission of cases of BSF among all suspected cases identifi ed by the System for Epidemiological Surveillance of São Paulo (CVE). After the description of temporal distribution (onset of symptoms) and the environmental and demographic variations of the confi rmed and discarded cases, a multiple logistic regression model was applied. Results: We searched 569 probable locations of infection (PLI) with 210 (37%) confi rmed cases of BSF and 359 (63%) discarded cases. The associated variables for the confi rmation of BSF in the multiple logistic model using a confi dence interval (CI) of 95% were age (OR = 1.025 CI: 1.015-1.035), the presence of Amblyomma sculptum in the environment (OR = 1.629 CI: 1.097-2.439), the collection of ticks from horses (OR = 1.939 CI: 0.999-3.764), the presence of capybaras (OR = 1.467 CI: 1.009-2.138), an urban environment (OR = 1.515 CI: 1.036-2.231), and the existence of a dirty pasture (OR = 1.759 CI: 1.028-3.003). Conclusions: The factors associated with the confi rmation of BSF cases included an urban environment, age, presence of the A. sculptum vector, the collection of ticks from horses, the presence of a capybara population, and a dirty pasture environment.

Seroprevalence of Rickettsia rickettsii and Rickettsia parkeri in dogs during a Brazilian Spotted Fever outbreak in the State of Rio de Janeiro

“…This reinforces the theory that ecological and environmental conditions can support R. rickettsii circulation (Angerami et al, 2009;Souza et al, 2015). These conditions were found in northwestern RJ such as the presence of flowing water bodies, equines, capybaras, ticks, scrubland, pasture, riparian vegetation and stray dogs.…”

“…The presence of capybaras was widely reported by interviewed people, with occurrence in altered landscapes close to human habitats containing dogs and other domestic animals, in riverside communities with riparian vegetation and in human-inhabited urban areas. These characteristics were decisive for the occurrence of R. rickettsii in canine sera in other studies (Perez et al, 2008;Angerami et al, 2009;Souza et al, 2015;Nasser et al, 2015) and indicate the importance of ecology and the environment in the appearance of spotted fever in northwestern RJ.…”

“…This city has a distinct hydrography with the Carangola river running through the city's entire length and even bordering the city's commercial center. Studies have shown the importance of riverside communities regarding the possibility of human infection by R. rickettsii in endemic areas, where the majority of PLI are close to banks of flowing water bodies (Angerami et al, 2009;Souza et al, 2015;Nasser et al, 2015). hydrochaeris) as a potential R. rickettsii maintaining species in nature (Perez et al, 2008).…”

“…ticks and with wild hosts and their parasites to peri-domestic environment (Cunha et al, 2014). So, regardless if whether the dogs had constant contact with riparian woodlands, other important factors can be attributed to the presence of R. rickettsii in these endemic areas such as the epidemiological situation of the studied location and constant contact of animals with infection-prone environments, e.g., flowing water bodies, scrublands and the presence of wild capybaras (Sangioni et al 2005;Angerami et al, 2009;Souza et al, 2015;Nasser et al, 2015). Thus, this study presents the ecological and environmental characterization of the occurrence of R. rickettsii in spotted fever endemic areas in northwestern RJ.…”

“…The capybaras have a high reproductive capacity and few natural predators (Ferraz et al, 2007) and the presence and abundance of possible R. rickettsii vectors are related to areas with scrublands and riparian woodlands which can serve as hideouts for wild animals with which dogs can come in contact (Szabó et al, 2013;Souza et al, 2015) and can be found in northwestern RJ. The research was conducted during a spotted fever outbreak, when canines were infected by R. rickettsii, and where favorable environmental and ecological conditions for the maintenance of wild animals in contact with dogs and, consequently, for ticks which parasitize them (Szabó et al, 2013;Souza et al, 2015).…”