Spotted Fever: Epidemiology and Vector-Rickettsia-Host Relationship in Rio de Janeiro State.

Diego C Montenegro,Karla Bitencourth,Nicolau M Serra-Freire,Maria S B Sousa,Marinete Amorim,Karen M Cardoso,Cristina Giordano-Dias,Gilberto S Gazêta,Ana P Borsoi,Stefan V De Oliveira,Reginaldo P Brazil

doi:10.3389/fmicb.2017.00505

Diego C Montenegro, Karla Bitencourth + Show 9 more

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https://doi.org/10.3389/fmicb.2017.00505

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Abstract

The eco-epidemiological scenario of spotted fever (SF), a tick-borne disease that affects humans and other animals in several countries around the world, was analyzed in Rio de Janeiro (RJ) State, Brazil. During the last 34 years, 990 SF cases were reported in RJ (the Brazilian state with the highest population density), including 116 cases confirmed by serology (RIFI) or PCR, among 42.39% of the municipalities with reported cases of SF. The epidemiologic dynamics of SF in RJ State are very heterogeneous in time and space, with outbreaks, high mortality rates and periods of epidemiological silence (no SF cases reported). Furthermore, it exhibited a changing epidemiological profile from being rural to becoming an urban disease. This study identified arthropods infected with Rickettsia felis, R. bellii and R. rickettsii, and found that the abundance of ectoparasites was associated with specific hosts. The R. rickettsii-vector-host relationship was most evident in species-specific parasitism. This suggests that the association between dogs, cattle, horses, capybaras and their main ectoparasites, Rhipicephalus sanguineus and Ctenocephalides felis, Rhipicephalus microplus, Dermacentor nitens, and Amblyomma dubitatum, respectively, has a key role in the dynamics of R. rickettsii transmission in enzootic cycles and the maintenance of carrier ectoparasites, thus facilitating the existence of endemic areas with the ability to produce epidemic outbreaks of SF in RJ. This study found confirmed human infections for only the R. rickettsii carrier Amblyomma sculptum, which reinforces the importance of this species as a vector of the pathogen in Brazil. This study can be adapted to different eco-epidemiological scenarios of spotted fever throughout the Americas.

Highlights

Rickettsioses are diseases caused by obligate intracellular bacteria of the genus Rickettsia
Even within that period (2007–2014), we found eight cases of spotted fever (SF) caused by R. rickettsii and one case caused by R. parkeri
The first reports of SF in the study area were in the 1940’s, and it was considered a disease of rural areas for several decades (Tostes and Bretz, 1941; Greca et al, 2008)

Summary

Introduction

Rickettsioses are diseases caused by obligate intracellular bacteria of the genus Rickettsia. Different species of the Spotted-Fever Group of Rickettsia (SFGR) are considered etiologic agents of spotted fever (SF), a zoonosis widely distributed throughout the world, with seasonal and sporadic outbreaks that may involve high mortality rates (Raoult and Roux, 1997; Rudakov et al, 2003; Parola et al, 2009, 2013; Eremeeva and Dasch, 2015). The SFGR transmission-cycle is maintained by the capacity of ticks to act as vectors, reservoirs and/or amplifiers of the bacteria. Spotted fever is the most prevalent tick-borne illness in Brazil (Fiol et al, 2010; Brasil, 2014a), having been first reported in the country in the early 20th century (Fialho, 1929; Piza et al, 1931). A variety of species of Rickettsia, and their vectors, have since been identified in areas with reported cases of SF (Cunha et al, 2009; Gehrke et al, 2009; Medeiros et al, 2011; Szabó et al, 2013, Moura-Martiniano et al, 2014), illustrating the complexity of its enzootic and epidemic cycles, as well as the diversity of potential vectors

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