Testing two PCR protocols targeting different genes to detect SFG Rickettsia DNA in ticks samples

Ticks are obligate blood sucking arthropod parasites, capable to transmit a large variety of pathogens, being considered the most commons vectors in Europe. Among important tick-borne pathogens, spotted fever group (SFG) of Rickettsia genus represent one of the most diverse group, comprising a large number of zoonotic agents. Moreover, the pathogenicity for humans of some Rickettsia species is under continuous description. Up to date, several important SFG Rickettsia, which pose a risk for public health in Europe were described. Among these, R. conorii subsp. conorii, the agent responsible for the Mediterranean Spotted Fever is endemic in the southern part of Romania, with fatal cases being reported in humans. Moreover, human infections with R. massiliae, R. raoultii and R. slovaca were reported in Romania. However, few data regarding the epidemiology in ticks and in the natural reservoir hosts are available. Therefore, further studies are needed to estimate the extent of real risk of rickettsial infections for human population. In this context the aim of this study was to identify the most suitable protocol to be used in the screening of rickettsial infection. Based on the literature data two different genes glt A and omp A, were chosen to be tested due to their high specificity. A total of 474 Dermacentor marginatus, collected by flanging from 3 counties in North-Western Romania, were tested for rickettsial infection by PCR using specific primers targeting the two genes chosen. Nine ticks were found positive to SFG Rickettsia DNA presence by targeting glt A gene and five targeting omp A gene. These preliminary results suggest a higher sensitivity of the protocol using primers targeting glt A gene. Alongside D. reticulatus, D. marginatus is the most probable vector of Rickettsia raoultii and R. slovaca, the agents of SENLAT syndrome. The syndrome was reported in Romania in two patients. Based on these results the best approach for SFG Rickettsia infection screening is by amplification of glt A gene. In addition, the amplification of omp A gene may be used for sequencing since the obtained sequence is longer and phylogenetical studies may be more conclusive.