scholarly journals Serological evidence of Rickettsia in horses from a semi-arid Brazilian region

2021 ◽  
Vol 30 (2) ◽  
Author(s):  
Ila Ferreira Farias ◽  
Eline Almeida Rodrigues de Souza ◽  
Maria Carolina de Azevedo Serpa ◽  
Flávio Silva Palha ◽  
Glauber Meneses Barboza de Oliveira ◽  
...  
Keyword(s):  
Central Region ◽  
Endemic Area ◽  
Spotted Fever ◽  
Immunofluorescence Assay ◽  
North Central Region ◽  
North Central ◽  
Rickettsia Rickettsii ◽  
The North ◽  
Tick Borne Disease ◽  
Brazilian Spotted Fever

Abstract Brazilian spotted fever (BSF) is a common tick-borne disease caused by Rickettsia rickettsii. Horses are the primary hosts of the main vector, Amblyomma sculptum, and are considered efficient sentinels for circulation of Rickettsia. Therefore, the aim of this study was to detect antibodies reactive to R. rickettsii antigens in horses from a non-endemic area in the north-central region of Bahia state, Brazil. Blood samples and ticks were collected from 70 horses from the municipalities of Senhor do Bonfim, Antônio Gonçalves, Pindobaçu, and Campo Formoso. The sera obtained were tested by an indirect immunofluorescence assay to detect anti-Rickettsia antibodies. Overall, 5.7% (4/70) of the horses reacted to R. rickettsii antigens. Ticks were collected from 18.6% (13/70) of the horses and were identified as A. sculptum and Dermacentor nitens. Despite being a non-endemic area, seropositive animals were identified in our study, suggesting circulation of rickettsial agents in the region. This is the first serological survey of this agent in horses from the north-central region of Bahia, and further studies are needed to understand the epidemiology of BSF in these locations.

Rickettsia rickettsii (Rickettsiales: Rickettsiaceae) Infecting Amblyomma sculptum (Acari: Ixodidae) Ticks and Capybaras in a Brazilian Spotted Fever-Endemic Area of Brazil

2019 ◽  
Vol 57 (1) ◽  
pp. 308-311 ◽  
Author(s):  
Francisco B Costa ◽  
Monize Gerardi ◽  
Lina de C Binder ◽  
Hector R Benatti ◽  
Maria Carolina de Azevedo Serpa ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Infection Rate ◽  
Guinea Pigs ◽  
Endemic Area ◽  
Spotted Fever ◽  
Immunofluorescence Assay ◽  
Southeastern Brazil ◽  
Rickettsia Rickettsii ◽  
Brazilian Spotted Fever ◽  
Low Incidence

Abstract The bacterium Rickettsia rickettsii is the agent of Brazilian spotted fever (BSF), a highly fatal disease that is transmitted in Brazil mainly by the tick Amblyomma sculptum Berlese, which uses capybaras (Hydrochoerus hydrochaeris Linnaeus) as major hosts. In 2015, we captured nine capybaras in a BSF-endemic area of southeastern Brazil. From each capybara, we collected blood sera that were tested through the immunofluorescence assay using Rickettsia spp. antigens, and A. sculptum ticks, processed for isolation of R. rickettsii through guinea pig inoculation. All capybaras (100%) were seroreactive to Rickettsia spp., with highest titers to R. rickettsii. A total of 166 A. sculptum ticks were macerated and inoculated into nine guinea pigs, from which only one presented high fever and seroconverted to R. rickettsii. Blood from this febrile animal was inoculated into additional guinea pigs (guinea pig passages), which also became febrile and seroconverted, or when euthanized during the fever period, their internal organs (spleen, lung) were shown to contain R. rickettsii DNA. The present rickettsial isolate has been maintained cryopreserved as infected guinea pig organs. There was at least one R. rickettsii-infected tick among the 166 macerated ticks, giving a minimal infection rate of 0.6% (1/166). This infection rate is within the range of previous studies, which reported that only 0.05% to at most 1.28% A. sculptum ticks were infected by R. rickettsii in other BSF-endemic areas. These low infection rates support the low incidence of BSF, despite of A. sculptum being the most frequent human-biting tick in southeastern Brazil.

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