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

TL;DR

This study found high rates of Rickettsia infection in ticks collected from shelter dogs in Romania, indicating a significant zoonotic risk.

Contribution

The study provides new data on Rickettsia prevalence in ticks from shelter dogs in Tulcea County, Romania.

Findings

93.2% of tick pools tested positive for Rickettsia spp. DNA.

Dermacentor reticulatus ticks showed 100% pool positivity for Rickettsia.

Shelter dogs are identified as sentinel hosts for Rickettsia circulation.

Abstract

Ticks are one of the most important vectors of zoonotic pathogens in Europe, including Rickettsia 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 Rickettsia 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 (Rhipicephalus sanguineus s.l., Ixodes ricinus, Dermacentor marginatus, and Dermacentor reticulatus), 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 gltA gene, specific for Rickettsia spp. Overall, 123/132 (93.2%) pools tested positive for Rickettsia 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 Rhipicephalus sanguineus s.l. (MIR 15%), 88.2% for Ixodes ricinus (MIR 20.5%), 87.5% for Dermacentor marginatus (MIR 58.3%), and 100% for Dermacentor reticulatus (MIR 21.7%). These findings demonstrate a substantial circulation of Rickettsia 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.

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