Infecção natural por Theileria equi (Piroplasmida: Theileriidae) e Babesia caballi (Piroplasmida: Babesiidae) em carrapatos coletados em pastagens frequentadas por equinos e bovinos nas Microrregiões de Itaguaí e Serrana, Estado do Rio de Janeiro

Abstract

Equine piroplasmosis stands out among the diseases that affect the majority of horse herds in Brazil, and is caused by protozoans, of intraerythrocytic location, named Theileria equi and Babesia caballi . This study aimed to determine the rate of natural infection by T. equi and B. caballi in ticks collected from pastures frequented by horses and/or cattle in Serrana and Itaguai micro-regions in state of Rio de Janeiro, Brazil. Furthermore, the other objective was to evaluate the possible associated factors to rate of infected ticks collected in different properties, according to the characteristics of each micro-region studied. The tick collections were performed in 28 properties in the studied areas between January and August 2013. Ticks were collected from pastures by dragging flannel method over the vegetation, CO2 traps and manual collection after viewing. The ticks collected were identified, counted, separated by life stage and pools of ticks samples were formed. Genomic DNA was extracted and the samples were analysed by real time PCR and nested PCR. Four thousand seven hundred sixteen (4.716) ticks were collected, 84.8% (n=3.997) of Amblyomma genus, 10.9% (n=514) of Dermacentor genus and 4.3% (n=205) of Rhipicephalus genus. From the samples collected, 4.276 were larvae, 431 nymphs and 9 adults. In 92.3% (N=13) properties of Itaguai micro-region was found the presence of ticks in the grazing area to animals, differing significantly (p<0.05) of Serrana microregion, where only 53.3% (N=15) of properties had tick infestation. Among all the variables analyzed about the animals breeding, only the presence of ticks in horses was statistically associated (p<0.05, FR=3.6) with the presence of ticks on the pastures of the properties. Regarding collection methods, in the CO2 trap was possible to collect a large percentage of nymphs in compared to larvae population. However, in the drag flannel method, the percentage of collected larvae was higher than the other developmental stages. Regarding the detection of target DNA to T. equi, 5.8% (n=24) of tested samples were considered positives by the real time PCR (qPCR) and nested PCR techniques. On the amount of each tick genus analyzed, it was found that 5.1% (n=18) of Amblyomma samples, 13.2% (n=5) of Dermacentor samples and 4.0% (n=1) of Rhipicephalus samples, showed amplification of target DNA of T. equi in qPCR. About the total number of tick samples analyzed (N=414), 1.9% (n=8) showed amplification of the gene that encodes the protein of roptria BC48, especific to B. caballi by nested PCR. It was observed that 1.7 % (n=6) of the samples of Amblyomma genus and 5.3% (n=2) of samples of Dermacentor genus amplify the target fragment. It is possible to conclude that Amblyomma genus was the more often found in the micro-regions pastures, and that Amblyomma and Dermacentor genus are able to infect itself naturally by T. equi and B. caballi in the studied regions.The detection of T. equi in tick larvae of the three genus indicates that there is occurrence of transovarial transmission in these species.