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| Author(s): |
Daniel Moura de Aguiar
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2006-06-09 |
| Examining board members: |
Marcelo Bahia Labruna;
Solange Maria Gennari;
Mitika Kuribayashi Hagiwara;
Rosangela Zacarias Machado;
Márcio Garcia Ribeiro
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| Advisor: | Marcelo Bahia Labruna |
| Abstract | |
The present study was conducted to investigate the canine ehrlichiosis epidemiology in Brazil, through molecular characterization of indigenous isolates and prevalence of infection in dogs (Canis familiaris) and Rhipicephalus sanguineus ticks. Firstly, it was performed the isolation of the Jaboticabal strain of Ehrlichia canis in DH82 cells from an experimentally infected dog, followed by molecular identification of the isolate by sequencing a fragment of the Ehrlichia dsb gene. After that, a new strain of E. canis was isolated from a naturally infected dog, assisted in the Veterinarian Hospital (HOVET) of the Faculty of Veterinary Medicine, University of São Paulo. This isolate was characterized by obtaining dsb, 16S rRNA and P28 nucleotide partial sequences. After the establishment of Jaboticabal strain in DH82 cells, an Indirect Immunofluorescence Test (IFAT) was developed, and 314 urban and rural dogs from Monte Negro Municipality were tested by this technique. Finally the prevalence of E. canis was determined in four different populations of Rhipicephalus sanguineus ticks, being one population from Monte Negro, RO. and three from different areas from São Paulo state using a PCR targeting an erlichial dsb gene fragment. Culture of E. canis Jaboticabal presented positive results by PCR on day 27. The dsb sequence was identical to other E. canis sequences available in GenBank. Cell culture inoculated with material from the dog assisted in the HOVET became positive by day 14 when dsb PCR was positive. This new strain was designated as isolate São Paulo of E. canis and showed to contain identical dsb and high similar partial sequences of 16S rRNA and P28 genes with others E. canis strains available in GenBank. Antibodies Anti-E. canis (titers ± 40) were detected in 31.2% (98/314) of the dogs, being 37.9% (58/153) in urban and 24.8% (40/161) in rural dogs of Monte Negro; these values were significantly different (P<0.05). The prevalence of infected ticks (given as minimal infection rate) was 2.3, 6.2, and 3.7% for populations 1 (Monte Negro), 2 (Jundiaí, SP), and 3 (São Paulo I, SP), respectively, which were statistically similar (P>0.05). In contrast, no infected tick was detected in population 4 (São Paulo II, SP). DNA sequences were determined for some of the PCR products generated from ticks and dogs from populations 1-3, being all identical to each other and to available sequences of E. canis. These results reinforce previous studies that reported E. canis infecting dogs in Brazil, but report for the first time in Brazil the natural infection of E. canis in its vector, R. sanguineus, which is the commonest tick infesting dog in this country. (AU) | |