Susceptibility of Amblyomma sculptum, Vector of Rickettsia rickettsii, Ticks from a National Park and an Experimental Farm to Different Synthetic Acaricides.

Amblyomma sculptum is a relevant tick species from a One Health perspective, playing an important role as a vector of Rickettsia rickettsii, the main agent of spotted fever rickettsiosis in Brazil. In this study, we evaluated the susceptibility of two A. sculptum populations from Goiás state (midwestern Brazil) to different acaricides. The first tick population (GYN strain) originated from an experimental farm, where the ticks are annually exposed to acaricides. The second (PNE strain) was collected in a national park (Emas National Park), where the ticks had not been exposed to acaricides. Immersion tests were conducted with 21-day-old laboratory-reared larvae and nymphs originating from adult ticks collected in the areas mentioned above. The chosen acaricides were two synthetic pyrethroids (cypermethrin and deltamethrin), one organophosphate (chlorfenvinphos), one formamidine (amitraz), and two combinations of pyrethroids and organophosphates (cypermethrin, chlorpyrifos and citronellal; cypermethrin, fenthion and chlorpyrifos). Mortality data were used to determine the lethal concentration (LC) values at which 50%, 90%, and 99% of the ticks died (LC50, LC90, and LC99, respectively), and resistance ratios (RR) were calculated based on the LC values. The RR revealed differences between the acaricide-exposed (GYN) and unexposed (PNE) tick strains. The PNE strain larvae and nymphs were susceptible to all the tested acaricides. The GYN strain larvae were tolerant to cypermethrin, whereas the nymphs were tolerant to deltamethrin, chlorfenvinphos, and the combination of cypermethrin, chlorpyrifos, and citronellal (2 < RR ≤ 10). The GYN strain nymphs were resistant to amitraz (RR > 10). This is the first report of A. sculptum nymphs with resistance to amitraz and tolerance to deltamethrin, chlorfenvinphos, and the combination of cypermethrin, chlorpyrifos, and citronellal.

Phylogenetic Inferences Based on Distinct Molecular Markers Confirm a Novel Babesia Species (Babesia goianiaensis nov. sp.) in Capybaras (Hydrochoerus hydrochaeris) and Associated Ticks.

Piroplasmids (order Piroplasmida) are a diverse group of tick-borne protozoa that may cause disease in animals and occasionally in humans. Novel Piroplasmida clades and species have been found in wild animals from Brazil based on the phylogenetic assessment of near-complete 18S rRNA, mitochondrial and heat-shock protein genes. For instance, a putative novel Babesia species has been detected in capybaras and Amblyomma ticks in three Brazilian states. The present work aimed to describe, using phylogenetic assessments based on distinct molecular markers, this novel Babesia species in capybaras and associated ticks (Amblyomma sculptum and Amblyomma dubitatum) sampled in Goiânia city, Goiás state, midwestern Brazil. While the phylogenetic analysis based on both near-complete 18S rRNA and hsp-70 genes positioned the sequences obtained from capybara blood samples into a new clade sister to the Babesia sensu stricto clade, the phylogenetic inference based on the COX-3 amino acid positioned the obtained sequences from capybara blood samples and A. sculptum ticks also into a clade sister to the Theileria sensu stricto clade, highlighting the inappropriateness of this marker inferring evolutionary relationships among piroplasmids. Pairwise distance analysis demonstrated that the divergence rates between the 18S rRNA sequences detected in capybaras and other Piroplasmida already described were very high and ranged from 9.4 to 12.9%. Genotype analysis based on the near-full 18S rRNA sequences of the Piroplasmida detected in capybaras and associated ticks demonstrated the occurrence of high genotype diversity at an intra-species level. In conclusion, phylogenetic analyses based on distinct molecular markers supported the description of Babesia goianiaensis nov. sp. in capybaras and associated Amblyomma ticks. Additionally, a novel phylogenetic clade, apart from the previously described ones, was described in the present study and contributed to untangling the complex evolutionary history of the Piroplasmida.

Rickettsial Infection in Ticks from a National Park in the Cerrado Biome, Midwestern Brazil.

This study was carried out from February 2020 to September 2021 in Parque Nacional das Emas (PNE), a national park located in the Cerrado biome, midwestern Brazil, as well as in surrounding rural properties. Serum and tick samples were collected from dogs, terrestrial small mammals, and humans. Ticks were also collected from the environment. Dogs were infested with Rhipicephalus linnaei adults, whereas small mammals were infested by immature stages of Amblyomma spp., Amblyomma triste, Amblyomma dubitatum, and Amblyomma coelebs. Ticks collected from vegetation belonged to several species of the genus Amblyomma, including A. coelebs, A. dubitatum, Amblyomma naponense, Amblyomma sculptum, and A. triste. Two Rickettsia species were molecularly detected in ticks: Rickettsia parkeri in A. triste from the vegetation and a Rickettsia sp. (designated Rickettsia sp. strain PNE) in A. sculptum and A. triste collected from lowland tapirs (Tapirus terrestris). Based on short gltA gene fragments, this rickettsial organism showed 99.7-100% to Rickettsia tillamookensis. Seroreactivity to Rickettsia antigens was detected in 21.9% of dogs, 15.4% of small mammals, and 23.5% of humans. The present study reveals the richness of ticks and demonstrates the circulation of rickettsial agents in one of the largest conservation units in the Cerrado biome in Brazil. To our knowledge, this is the first report of a rickettsial phylogenetically related to R. tillamookensis in Brazil.

Epidemiology of Rickettsia spp. in Atlantic rainforest areas of island and seashore mainland, southern Brazil.

Non-fatal cases of rickettsial infection with different clinical features than the classic BSF (Brazilian Spotted Fever) have been reported in seashore areas of Paraná state, southern Brazil. In addition, Amblyomma ovale tick infected by Rickettsia parkeri strain Atlantic rainforest has been also described in this area. Accordingly, the aim of this study was to investigate the occurrence of anti-Rickettsia spp. antibodies in human and dog populations, and Rickettsia spp. infection in ticks from oceanic islands and seashore mainland cities of southern Brazil. Serum samples were collected from 328 persons and their 282 dogs from three islands and two seashore mainland cities. A total of 211 ticks were collected from dogs, identified as A. ovale and R. sanguineus. In overall, 40 of 328 (12.2%) human samples were seropositive for Rickettsia spp., including 21 of 190 (11.1%) on islands and 19 of 138 (13.7%) on seashore mainland, and 62 of 282 (22.0%) dog samples, including 31 of 153 (20.3%) on islands and 31 of 129 (24.0%) in seashore mainland areas. In overall, nine of 82 (11.0%) ticks were positive to real-time PCR assay targeting a fragment of the rickettsial gltA gene, including two of 64 (3.1%) Rickettsia sanguineus and seven of 18 (38.9%) A. ovale, of which four were infected with the R. parkeri strain Atlantic rainforest. Despite no association between risk factors and Rickettsia spp. seropositivity was found in human beings, access to natural areas (p = .011) and tick infestation (p = .004) was significantly associated to dog seropositivity. The serological and molecular findings herein have confirmed previous tick and clinical case reports and enlarged the geographical occurrence of A. ovale infected by R. parkeri strain Atlantic rainforest in oceanic islands and seashore mainland cities of Paraná State, indicating a new likely transmission area of this new rickettsial infection in human beings and dogs of southern Brazil.

Detection of an Undescribed Babesia sp. in Capybaras and Amblyomma Ticks in Central-Western Brazil.

Capybaras (Hydrochoerus hydrochaeris) are the largest rodents on Earth. While capybaras are hosts for various tick species, there is limited information regarding the tick-borne pathogens they can carry. We investigated the presence of piroplasmids and Ehrlichia spp. in capybaras and their associated ticks in two peri-urban areas in Goiás state, central-western Brazil. Blood samples collected from 23 capybaras were used to investigate the presence of piroplasmids and Ehrlichia spp. in stained-blood smears and by PCR. Ticks collected from the capybaras were identified morphologically and also tested using PCR for the same pathogens. A total of 955 ticks were collected, including 822 (86.1%) Amblyomma sculptum, 132 (13.8%) Amblyomma dubitatum, and one (0.1%) unidentified larva of Amblyomma sp. Neither the capybaras nor ticks were positive for Ehrlichia spp. However, a stained-blood smear examination revealed the presence of ring-stage and pyriform-shaped merozoites in the erythrocytes of one (4.4%) capybara. In the same way, 47.8% (11/23) and 19.9% (36/181) of blood samples and ticks, respectively, were positive for piroplasmids in the PCR. We successfully sequenced a partial 18S rRNA gene fragment of four samples (two capybaras, one A. sculptum, and one A. dubitatum), and the phylogenetic reconstruction disclosed that the organism reported in the present study clusters within the genus Babesia. Further research is required for a formal delineation of this species (designated as Babesia sp. strain Capybara) and to investigate the hypothesis of A. dubitatum and A. sculptum ticks being vectors.