Full text
| |
| Author(s): |
Iara Silveira
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2011-06-27 |
| Examining board members: |
Marcelo Bahia Labruna;
Solange Maria Gennari;
Fabio Gregori;
Richard de Campos Pacheco;
Matias Pablo Juan Szabo
|
| Advisor: | Marcelo Bahia Labruna |
| Abstract | |
In recent work, 9.7% of the Amblyomma triste of the marsh by the Paraná River in Paulicéia, State of São Paulo, was found infected with Rickettsia parkeri, the etiological agent of spotted fever rickettsiosis in humans. Based on this report, the present study aimed to determine soroprevelence of anti-R. parkeri antibodies in humans, horses, dogs and opossuns, and the prevalence of rickettsial infection in ectoparasites, in different areas of Paulicéia. While ticks were identified by using current morphological Keys for adults and nymphs, larva were identified to species by molecular methods (PCR targeting the mitochondrial 16S rRNA gene followed by DNA sequencing). Ticks were tested by PCR for the presence of Rickettsia DNA. Animal and human sera samples were tested by immunofluorescence assay (IFA) for the presence of antibodies reactive to R. rickettsii, R. parkeri, R. belli, R. amblyommii, R. riphicephalii and R. felis. From 1699 collected ticks, a vast marjority (1511) was Amblyomma. cajennense. The remaining were the especies A. coelebs (6), A. triste (2), A. dubitatum (114), Rhipicephalus (Boophilus) microplus (55), Dermacentor nitens (10) and Amblyomma rotundatum (1). Only two nymphs of A. coelebs were found infected by Rickettsia, yielding DNA sequences 99% identical to the gene ompA of R. amblyommii. 25 of human sera collected were negative, except for one for one that showed endpoint titer ≤64 to both R. parkeriand R. rickettsii. Among horses, 24% sera contained anti Rickettsia antibodies, with titles ranging from 64 to 1024, nine samples showed anti-R. parkeri titles at least four times higher than the remaining Rickettsia species, indicating that these animals had been infected by R. parkeri. For 55 dogs, 7.7% anti Rickettsia antibodies, with endpoint titles ranging from 64 to 256. For two canine serum R. parkeri was considered the possible agent responsible for the infection. Through statistical analyses of the serological results with independent variables, the presence of seropositive horses was significantly associated with (i) grazing in the marsh (ii) and being for more than 8.5 years in the region; these two independent variables were considered to be risk factors for rickettsiosis in the study region. A total of four opossums (Didelphis albiventris) were captured. All four had antibodies reactive to R. parkeri, R. rickettsia, R. amblyommii and R. rhipicephalii, however, with less than 4-fold differences between endpont titers to different Rickettsia species. Opossums were found infested by nymphs of A. cajennense and A. coelebs, all negative to Rickettsia by PCR. Based in these results, it is concluded that domestic animals and opossums had been in contact with Rickettsia of the spotted fever group in the study region, where the marsh area seems to be the main focus of Rickettsia-infected ticks (AU) | |