Full text
| |
| Author(s): |
Lina de Campos Binder
Total Authors: 1
|
| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2020-11-06 |
| Examining board members: |
Marcelo Bahia Labruna;
Alejandro Ramirez Hernandez;
Adriano Pinter dos Santos
|
| Advisor: | Marcelo Bahia Labruna |
| Abstract | |
Brazilian Spotted Fever (BSF) is an acute infectious disease caused by the bacterium Rickettsia rickettsii and transmitted by different ticks species. Due to deleterious effects caused on ticks by this bacterium, the horizontal transmission of R. rickettsii through an amplifier host is crucial for its maintenance in the tick population in BSF endemic areas. The tick Amblyomma aureolatum is the vector of R. rickettsii In the Metropolitan Region of São Paulo; however, it is not known which vertebrate could act as an amplifier host for this tick species. The domestic dog is the main host for A. aureolatum adults in BSF endemic areas located in this metropolitan region, being an excellent sentinel for BSF human cases. In order to assess dog\'s ability to act as an amplifier host, adult ticks of A. aureolatum were allowed to feed on two groups of dogs: the infected group and the control group, which were respectively infested with R. rickettsii infected ticks and with uninfected ticks. All dogs in the infected group developed a bacteremia sufficient to infect A. aureolatum females, and part of them was able to transmit the bacteria to their progeny. In order to investigate the possible variables associated with dog exposure to R. rickettsii, a serological survey was conducted on dogs from the Recreio da Borda do Campo neighborhood, municipality of Santo André, a BSF endemic area. By conducting this survey, it was possible to obtain 31% of positive samples. Through a logistic regression, it was found that the variables that showed an association with dogs\' seropositivity were “ frequency of unsupervised access to the street”, “shorter distance to the nearest human BSF case” and “greater distance to the main access road to the neighborhood”. Finally, to assess the population dynamics of dogs, photographic capture and recapture campaigns were carried out in two areas of the neighborhood with different densities of seropositive animals. Four campaigns were carried out over nine months. The abundance of dogs did not differ between the two areas, however the area with the highest density of seropositive dogs also presented a greater entry of new individuals. In this study, we were able to demonstrate that part of A. aureolatum females fed on dogs infected with R. rickettsii are able to transmit the bacteria efficiently to part of their progeny, suggesting that the dog could act as an amplifier host for R. rickettsii for this tick species. Our results confirm the excellent role of the dog as a sentinel for BSF human cases, in addition to showing the association of dog exposure to R. rickettsii with unsupervised access to the street. The greater presence of seropositive dogs in the most distant areas of the access road to the neighborhood could be associated with a greater introduction of new individuals, especially through frequent abandonments, as was reported by residents of the neighborhood and verified in our dog population dynamics study. (AU) | |
| FAPESP's process: | 18/01596-8 - Evaluation of possible epidemiological variables associated with the spatial distribution of Rickettsia rickettsii infection in dogs and ticks in an area endemic to Brazilian Spotted Fever in the Metropolitan Region of São Paulo |
| Grantee: | Lina de Campos Binder |
| Support Opportunities: | Scholarships in Brazil - Master |