Molecular Detection of Spotted-Fever Group Rickettsiae in Ticks Collected from Domestic and Wild Animals in Corsica, France

Abstract

To obtain a better understanding of the current magnitude of tick-borne rickettsioses in Corsica, we used molecular methods to characterize the occurrence of Rickettsia spp. in ixodid ticks collected from domestic and wild animals. The presence of Rickettsia spp. was evaluated using real-time polymerase chain reaction targeting the gltA gene and by sequencing of gltA and ompA partial genes for species identification and phylogenetic analysis. Infection rates were calculated as the maximum-likelihood estimation (MLE) with 95% confidence intervals (CI). In total, 1117 ticks belonging to four genera (Rhipicephalus, Hyalomma, Ixodes, and Dermacentor) were collected from cattle, sheep, wild boars, and companion animals during July-August 2017 and July 2018-January 2019. Overall, Rickettsia DNA was detected in 208 of 349 pools of ticks (MLE = 25.6%, 95% CI: 22.6-28.8%). The molecular analysis revealed five different rickettsial species of the spotted-fever group (SFG). We highlighted the exclusive detection of Candidatus Ri. barbariae in R. bursa and of Ri. aeschlimanii in H. marginatum. Rickettsia slovaca was detected in D. marginatus collected from wild boars. This study provides the first evidence of the presence of Ri. monacensis in I. ricinus ticks isolated from a dog in Corsica. In conclusion, our data revealed wide dispersal of SFG Rickettsiae and their arthropod hosts in Corsica, highlighting the need for surveillance of the risk of infection for people living and/or working close to infected or infested animals.

Keywords: Corsica; Rickettsia; domestic animals; host; ticks; wild animals.

Figure 1

(a) Seasonal distribution of ticks collected from cattle (May–August 2017 and July–December 2018); (b) Seasonal distribution of ticks collected from wild boars (August 2018–January 2019).

Figure 1

(a) Seasonal distribution of ticks collected from cattle (May–August 2017 and July–December 2018); (b) Seasonal distribution of ticks collected from wild boars (August 2018–January 2019).

Figure 2

(A) A phylogenetic tree of spotted fever-group Rickettsine based on the gltA gene sequences. The analysis was performed using a maximum-likelihood method with the Kimura 2-parameter model. This analysis involved 27 nucleotide sequences. A II ambiguous positions were removed for each sequence pair. There were a total of 744 positions in the final dataset. The sequences detected in this study are indicated in red. The simlified tick phylogeny consisting of four species is indicated on the top right. The colored boxes indicate the presence of Rickettsia DNA in each tick species. (B) A phylogenetic tree of spotted-fever group Rickettsiae based on the ompA gene sequences. The analysis was performed using a maximum-likelihood method with the Kimura 2-parameter model. This analysis involved 18 nucleotide sequences. All ambiguous positions were removed for each sequence pair. There were a total of 493 positions in the final dataset. The sequences detected in this study are indicated in red. The simplified tick phylogeny consisting of four species is indicated on the top right. The colored boxes indicate the presence of Rickettsia DNA in each tick species.

Figure 2

(A) A phylogenetic tree of spotted fever-group Rickettsine based on the gltA gene sequences. The analysis was performed using a maximum-likelihood method with the Kimura 2-parameter model. This analysis involved 27 nucleotide sequences. A II ambiguous positions were removed for each sequence pair. There were a total of 744 positions in the final dataset. The sequences detected in this study are indicated in red. The simlified tick phylogeny consisting of four species is indicated on the top right. The colored boxes indicate the presence of Rickettsia DNA in each tick species. (B) A phylogenetic tree of spotted-fever group Rickettsiae based on the ompA gene sequences. The analysis was performed using a maximum-likelihood method with the Kimura 2-parameter model. This analysis involved 18 nucleotide sequences. All ambiguous positions were removed for each sequence pair. There were a total of 493 positions in the final dataset. The sequences detected in this study are indicated in red. The simplified tick phylogeny consisting of four species is indicated on the top right. The colored boxes indicate the presence of Rickettsia DNA in each tick species.

Figure 3

Map of Corsica, France, indicating the tick collection sites and the animal species. GPS coordinates: Cattle: Oletta (42°38′00″ N, 9°21′22″ E), Filicetu (42°32′40″ N, 8°56′09″ E), Corti (42°18′23″ N, 9°09′05″ E), Nessa (42°33′04″ N, 8°56′57″ E), Portivechju (41°35′30″ N, 9°16′49″ E), Omessa (42°22′16″ N, 9°12′39″ E), Lama (42°34′39″ N, 9°10′22″ E), Monticellu (42°37′05″ N, 8°57′16″ E), Lucciana (42°32′48″ N, 9°25′05″ E), Calinzana (42°30′31″ N, 8°51′21″ E), Lentu (42°31′22″ N, 9°16′57″ E), San lurenzu (42°23′06″ N, 9°17′28″ E), San Martinu di lota (42°43′26″ N, 9°27′21″ E), Casamaccioli (42°19′06″ N, 9°00′07″ E), Patrimoniu (42°41′54″ N, 9°21′44″ E), Olmeta-di-tuda (42°36′44″ N, 9°21′16″ E), Farinole (42°43′58″ N, 9°21′58″ E), Penta-Acquatella (42°27′55″ N, 9°21′49″ E), Zilia (42°31′52″ N, 8°54′06″ E), Castellu di rustinu (42°27′52″ N, 9°18′56″ E), Pietralba (42°32′51″ N, 9°11′11″ E), Santa-Reparata-di-Balagna (42°36′16″ N, 8°55′45″ E), Cateri (42°34′21″ N, 8°53′33″ E), Ruglianu (42°57′25″ N, 9°25′08″ E), Filicetu (42°32′40″ N, 8°56′09″ E), Ascu (42°27′16″ N, 9°01′59″ E), Corscia (42°21′20″ N, 9°02′36″ E), Vilone Ornetu (42°24′06″ N, 9°28′18″ E), Furiani (42°39′32″ N, 9°24′54″ E), Monte grossu (42°30′06″ N, 8°55′22″ E), Tallone (42°13′55″ N, 9°24′53″ E). Wild boars: Chiatra (42°17′34″ N, 9°28′34″ E), Tralonca (42°20′39″ N, 9°12′26″ E), Quercitellu (42°25′37″ N, 9°21′02″ E), Bustanicu (42°19′24″ N, 9°18′03″ E), Favalellu (42°17′43″ N, 9°16′20″ E), Venzolasca (42°29′06″ N, 9°27′26″ E), Sermanu (42°18′54″ N, 9°16′06″ E), Palasca (42°35′24″ N, 9°02′36″ E), Pianellu (42°17′26″ N, 9°21′39″ E), Cagnanu (42°52′34″ N, 9°25′50″ E), Santa-Lucia-di-Mercuriu (42°19′37″ N, 9°13′18″ E), Aleria (42°06′53″ N, 9°30′48″ E), Mazzola (42°18′05″ N, 9°18′40″ E). Dogs: Biguglia (42°37′41″ N, 9°25′14″ E), Casanova (42°15′19″ N, 9°10′30″ E), Castellu di Rustinu (42°27′52″ N, 9°18′56″ E), Ponte-Leccia (42°26′10″ N, 9°18′01″ E), Palneca 41°58′14″ N, 9°10′26″ E). Cat: Muru (42°32′47″ N, 8°54′54″ E). Sheep: Biguglia (42°37′41″ N, 9°25′14″ E).