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

Celso Eduardo De Souza,Adriano Pinter,Maria Rita Donalisio

doi:10.1590/0037-8682-0281-2014

Celso Eduardo De Souza, Adriano Pinter + Show 1 more

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https://doi.org/10.1590/0037-8682-0281-2014

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Abstract

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. This essay presents a retrospective study to identify the factors associated with the transmission of cases of BSF among all suspected cases identified 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 confirmed and discarded cases, a multiple logistic regression model was applied. We searched 569 probable locations of infection (PLI) with 210 (37%) confirmed cases of BSF and 359 (63%) discarded cases. The associated variables for the confirmation of BSF in the multiple logistic model using a confidence 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). The factors associated with the confirmation 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.

Highlights

Brazilian spotted fever (BSF) is a disease transmitted by ticks for which the etiological agent is Rickettsia rickettsii
This retrospective study sought to identify factors associated with the transmission of BSF among suspected cases notified by the Information System for Notifiable Diseases [Sistema de Informação de Agravos de Notificação (SINAN)] in the time period from 2003 to 2013
According to multiple logistic regression analysis, the variables associated with BSF transmission included age (OR = 1.03 confidence interval (CI): 1.02-1.04), the presence of A. sculptum ticks in the environment (OR = 1.63 CI: 1.10-2.44), ticks collected from horses (OR = 1.94 CI: 0.99-3.76), the presence of capybaras (OR = 1.47 CI: 1.01-2.14), an urban/peri-urban environment (OR = 1.52 CI: 1.04-2.23), and the existence of a dirty pasture environment (OR = 1.76 CI: 1.03-3.01) (Table 2)

Summary

Introduction

Brazilian spotted fever (BSF) is a disease transmitted by ticks for which the etiological agent is Rickettsia rickettsii. The associated variables for the confirmation of BSF in the multiple logistic model using a confidence 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 confirmation 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. The lethality rate in the southeast region of Brazil ranges between 30 and 50%, with the States of São Paulo and Minas Gerais showing the most reported cases(4) (5).

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