Estudo epidemiológico de rickettsias do grupo da febre maculosa em caninos, equinos e seus carrapatos no Município de Resende, Estado do Rio de Janeiro, Brasil

Abstract

Diseases caused by rickettsiae are widely distributed worldwide and are associated with hematophagous arthropods. The bacteria Rickettsia rickettsii is the most pathogenic of the spotted fever group (SFG). In order to know the factors that led to the occurrence of the disease in this area and acquire more knowledge in the epidemiology of SF in Brazil, as their vectors and the sentinel animals, this study have had the following objectives: verify the occurrence of dogs and horses serological reactive to R. rickettsii, using the technique of indirect immunofluorescence assay (IFA); evaluate the potential of dogs and horses as sentinels for the occurrence SF; better understand the population of ixodidae in dogs and horses and evaluate by molecular tools the presence of the spotted fever group rickettsiae (SFGR) in ticks. It was found that 29 (27.62%) sera of dogs were reactive, with titles ranging from 1:64 to 1:4096 and 76 sera (72.38%) were not reactive. In the analysis of horses there was a total of 9 (9.4%) animals reactive and 87 (90.6%) not reactive to the IFA. It was collected a total of 470 ticks of dogs, which showed a percentage of infestation of 44%. It was identified the species Rhipicephalus sanguineus, Amblyomma cajennense, A. aureolatum, A. ovale and Rhipicephalus (Boophilus) microplus and nymphs of Amblyomma sp., R. sanguineus and R. (B.) microplus, and 33 larvae. A total of 975 ticks were collected from horses, the species: A. cajennense, R. (B.) microplus and Dermacentor (Anocentor) nitens. It was also collected nymphs of Amblyomma sp., R. (B.) microplus and D. (A.) nitens, and 15 larvae. Considering the total number of horses observed, 71% were parasitized by ticks. The polymerase chain reaction (PCR) was performed on samples of blood and ticks of dogs that had positive serology. Thus, it was submitted to the technique 82 ticks. Only one tick of the species R. sanguineus showed PCR positive, and amplified for the four primers studied (ompA, ompB, gltA and htrA). This tick infested canine founded the property where there were the cases of SF. The rate of infection in ticks was 1.22%. The sequence had similarity of 99,3% with deposits in GenBank of R. rickettsii. Based on the results observed in the studied region, it can be concluded that dogs were important sentinels for the agent of SF; canines regular contact with forests and pastures positively influenced the reactive infection by R. rickettsii; dogs coming from properties at least six kilometers away from the outbreak were reactive to SFGR, confirming the concept of endemic area; canine remained reactive to the SFGR to at least one year after the occurrence of five cases of Brazilian spotted fever diagnosed in 2006; the population of ixodidae found corroborates with other studies in areas endemic for SF. The presence of the bacteria R. rickettsii in the tick R. sanguineus in natural conditions have demonstrated a likely chance of participation of the transmission vector of R. rickettsii to humans in the area of study.