Prevalence of Rickettsia spp. Infection in Ticks Collected from Shelter Dogs in Tulcea County, Romania

Ticks are one of the most important vectors of zoonotic pathogens in Europe, including <i>Rickettsia</i> spp. In Romania, several pathogenic species belonging to the Spotted Fever Group (SFG) transmitted primarily through tick bites have been identified. The aim of the present study was to determine the prevalence of <i>Rickettsia</i> spp. infection in ticks collected from public shelter dogs in Tulcea County, Romania, as an indicator of pathogen circulation within shelter environments and their potential epidemiological relevance. A total of 730 ticks collected between March 2023 and September 2024 from 216 public shelter dogs, belonging to four species (<i>Rhipicephalus sanguineus</i> s.l., <i>Ixodes ricinus</i>, <i>Dermacentor marginatus</i>, and <i>Dermacentor reticulatus</i>), were morphologically identified and pooled by species, sex, and developmental stage resulting in 132 pools. DNA extracted from pools was tested by Real-Time PCR, targeting the <i>gltA</i> gene, specific for <i>Rickettsia</i> spp. Overall, 123/132 (93.2%) pools tested positive for <i>Rickettsia</i> spp. DNA, while the Minimum Infection Rate (MIR) at tick level was 16.8%. High pool positivity rates were consistently observed across all four species: 93.6% positive pools for <i>Rhipicephalus sanguineus</i> s.l. (MIR 15%), 88.2% for <i>Ixodes ricinus</i> (MIR 20.5%), 87.5% for <i>Dermacentor marginatus</i> (MIR 58.3%), and 100% for <i>Dermacentor reticulatus</i> (MIR 21.7%). These findings demonstrate a substantial circulation of <i>Rickettsia</i> spp. in dog-shelter associated ticks, highlighting the role of dogs as sentinel hosts. Continuous molecular surveillance and identifying circulating species is needed for a better determination of the zoonotic risk.