Dermacentor marginatus and Dermacentor reticulatus, and Their Infection by SFG Rickettsiae and Francisella-Like Endosymbionts, in Mountain and Periurban Habitats of Northwestern Italy

We investigated the distribution of Dermacentor spp. and their infection by zoonotic bacteria causing SENLAT (scalp eschar neck lymphadenopathy) in Turin province, northwestern Italy. We collected ticks in a mountain and in a periurban park, from vegetation and different animal sources, and we sampled tissues from wild boar. Dermacentor marginatus (n = 121) was collected in both study areas, on vegetation, humans, and animals, while D. reticulatus (n = 13) was exclusively collected on wild boar from the periurban area. Rickettsia slovaca and Candidatus Rickettsia rioja infected 53.1% of the ticks, and R. slovaca was also identified in 11.3% of wild boar tissues. Bartonella spp. and Francisella tularensis were not detected, however, Francisella-like endosymbionts infected both tick species (9.2%). Our findings provide new insights on the current distribution of Dermacentor spp. and their infection with a spotted-fever group rickettsiae in the Alps region. Wild boar seem to play a major role in their eco-epidemiology and dispersion in the study area. Although further studies are needed to assess the burden of rickettsial diseases, our results highlight the risk of contracting SENLAT infection through Dermacentor spp. bites in the region

Subcutaneous Ticks in Wild Carnivores: Any Host-Related Differences?

SIMPLE SUMMARY: Ticks are obligate parasites living part of their life attached on the skin surface of different mammal species. In the last decades, there have been several reports of ticks found dead underneath the skin of foxes, raccoon dogs, golden jackals, domestic dogs, and a human being. The biological reasons behind this phenomenon are still unclear, although most of the reports are in canid species, suggesting that the immunological response of canids might favor it. The aim of this study was to investigate the presence of ticks under the skin of different wild carnivore species in Northwestern Italy, where they have never been described before. Out of 63 wild carnivores, 11 foxes were found infested with 51 dead ticks under the skin of the animals. All the preserved ticks collected underneath the skin of the foxes were identified as Ixodes spp., meaning that this tick species might be more frequently involved in the phenomenon, as already suggested by the scientific community. By contrast, no subcutaneous ticks were found in wolves, the other most prevalent wild canid species in Northwestern Italy, supporting the idea that the immune reaction of wolves may not favor the embedment of ticks underneath the skin. ABSTRACT: Ticks under the skin have been shown in different canid species such as red fox, domestic dog, and raccoon dog. Despite being increasingly reported in Europe in the last decade, the biological mechanisms associated to subcutaneous ticks (SCT), as well as the predisposing factors, are not yet clear. The main goal of this study was to investigate the presence of SCT in wild carnivores in Northwestern Italy. Sixty-three wild carnivores were examined, and SCT were submitted to histological examination or stored in ethanol for morphological and molecular identification. A portion of the cox1 gene and 16S rDNA were amplified, and positive PCR products were sequenced. Fifty-one small brown-coloured nodules of about 2 × 3 mm containing ticks in different decomposition stages were observed in 11 out of 30 foxes. Seven ticks were classified as Ixodes ricinus, while 14 ticks were determined only at the genus level (Ixodes spp.), and in two ticks no morphological key was applicable due to the advanced degradation status. By PCR, the rDNA fragment of six ticks (26.1%, 95% CI: 12.6–46.5%) was amplified, and BLAST analysis revealed a 99–100% nucleotide similarity to I. ricinus. At the histological examination, the inflammatory response varied from a mild to a moderate mixed infiltrate, primarily composed by neutrophils and lymphocytes. The results of this study confirm foxes as the main wild reservoir for SCT. The absence of SCT in other carnivores (badgers and martens) is in accordance with other studies. Ixodes ricinus is the most frequently reported tick species, corroborating the idea that longirostral ticks might be more frequently associated to SC embedment than brevirostral ticks

The Genetic Diversity of Rickettsiella Symbionts in Ixodes ricinus Throughout Europe

Rickettsiella species are bacterial symbionts that are present in a great variety of arthropod species, including ixodid ticks. However, little is known about their genetic diversity and distribution in Ixodes ricinus, as well as their relationship with other tick-associated bacteria. In this study, we investigated the occurrence and the genetic diversity of Rickettsiella spp. in I. ricinus throughout Europe and evaluated any preferential and antagonistic associations with Candidatus Midichloria mitochondrii and the pathogens Borrelia burgdorferi sensu lato and Borrelia miyamotoi. Rickettsiella spp. were detected in most I. ricinus populations investigated, encompassing a wide array of climate types and environments. The infection prevalence significantly differed between geographic locations and was significantly higher in adults than in immature life stages. Phylogenetic investigations and protein characterization disclosed four Rickettsiella clades (I-IV). Close phylogenetic relations were observed between Rickettsiella strains of I. ricinus and other arthropod species. Isolation patterns were detected for Clades II and IV, which were restricted to specific geographic areas. Lastly, although coinfections occurred, we did not detect significant associations between Rickettsiella spp. and the other tick-associated bacteria investigated. Our results suggest that Rickettsiella spp. are a genetically and biologically diverse facultative symbiont of I. ricinus and that their distribution among tick populations could be influenced by environmental components

Use of Wild Ungulates as Sentinels of TBEV Circulation in a Naïve Area of the Northwestern Alps, Italy.

Wild and domestic animals can be usefully employed as sentinels for the surveillance of diseases with an impact on public health. In the case of tick-borne encephalitis virus (TBEV), the detection of antibodies in animals can be more effective than screening ticks for detecting TBEV foci, due to the patchy distribution of the virus. In the Piedmont region, northwestern Italy, TBEV is considered absent, but an increase in tick densities, of Ixodes ricinus in particular, has been observed, and TBEV is spreading in bordering countries, e.g., Switzerland. Therefore, we collected sera from wild ungulates during the hunting season (October-December) from 2017 to 2019 in the Susa Valley, Italian western Alps, and screened them for TBEV antibodies by a commercial competitive ELISA test. We collected 267 serum samples by endocranial venous sinuses puncture from red deer, roe deer and northern chamois carcasses. The animals were hunted in 13 different municipalities, at altitudes ranging between 750 and 2800 m a.s.l. The serological survey for TBEV yielded negative results. Borderline results for five serum samples were further confirmed as negative for TBEV by a plaque reduction neutralisation test. To date, our results indicate that TBEV is not circulating in western Piedmont. However, monitoring of TBEV should continue since TBEV and its vector are spreading in Europe. The wide-range distribution of wild ungulates and their role as feeding hosts, make them useful indicators of the health threats posed by Ixodid ticks