Comparative evaluation of Amblyomma ovale ticks infected and noninfected by Rickettsia sp. strain Atlantic rainforest, the agent of an emerging rickettsiosis in Brazil

Serological and Molecular Survey of Rickettsial Agents in Wild Boars (Sus scrofa) from Midwestern Brazil

Wild boars (Sus scrofa L.) are considered among the most harmful invasive species worldwide, causing irreversible ecosystem damage, acting as zoonotic spreaders and reservoirs, threatening human and animal health, and having an important economic impact. Accordingly, the present study has assessed the rickettsial exposure, tick infestation of wild boars, and rickettsial DNA presence in ticks from infested animals from the Cerrado biome in midwestern Brazil. Anti-Rickettsia spp. antibodies were detected in serum samples of wild boars by immunofluorescence assay. Overall, 106/285 (37.2%) wild boar serum samples from 13 to 18 (72.2%) municipalities showed seroreactivity to at least one of the four Rickettsia spp. antigens tested, the largest number of wild boars serologically tested to Rickettsia spp. in this type of study. Among the 106 seroreactive animals, 34 showed possible homologous reactions between R. parkeri, R. amblyommatis, and R. bellii, with endpoint titers between 128 and 512. A sample of 45 ticks collected from four culled wild boars was identified as Amblyomma sculptum, and all tested negative for rickettsial DNA presence. In conclusion, this study has provided a reliable sampling seroprevalence and indicated high exposure of wild boars to rickettsial agents, with a potential interaction with Rickettsia spp. from the spotted fever group within the Cerrado biome from midwestern Brazil.

Sharing of living area and exposure of domestic and wild canids to ticks, Rickettsia parkeri and Rangelia vitalii in the Atlantic Forest of southern Brazil

Spotted fever caused by the bacterium Rickettsia parkeri, and canine rangeliosis caused by the protozoan Rangelia vitalii, are emerging or re-emerging tick-borne diseases in Brazil, where the main tick vectors are Amblyomma ovale and Amblyomma aureolatum, respectively. In the present study, we evaluated exposure to R. parkeri and R. vitalii infection among domestic (Canis lupus familiaris) and wild (Cerdocyon thous) canids sharing living areas within an Atlantic Forest area of southern Brazil. Four different domestic dogs and three different wild canids were captured. Most of the ticks collected from either domestic or wild canids were identified as A. ovale and A. aureolatum. DNA of R. parkeri was amplified from 14% of the A. ovale specimens. Two domestic dogs and two wild canids were seroreactive to R. parkeri antigens with high endpoint titers (>1024). Rangelia vitalii DNA was detected in two wild canids; one of them was resampled 93 days later, again infected by R. vitalii. We report exposure/infection of domestic dogs and wild canids to R. vitalii and/or R. parkeri-infected ticks in an Atlantic Forest area shared by both canid species, indicating that they also shared the same populations of the tick vectors, A. aureolatum and A. ovale. While A. ovale, A. aureolatum, R. parkeri, R. vitalii and C. thous, are all native to the Atlantic Forest, further studies are needed to evaluate the impact of an exotic canine species - C. lupus familiaris - on the enzootic cycles of R. vitalii and R. parkeri, as well as the possible role of domestic dogs in emergence and re-emergence of R. parkeri-spotted fever in humans and canine rangeliosis, respectively.

Pathogenic Rickettsia, Anaplasma, and Ehrlichia in Rhipicephalus microplus ticks collected from cattle and laboratory hatched tick larvae

BACKGROUND

The order Rickettsiales contains a group of vector-borne gram-negative obligate intracellular bacteria, which often cause human emerging infectious diseases and economic losses for dairy and meat industries. The purpose of this study is to investigate the distribution of the pathogens including Rickettsia spp., Anaplasma spp., and Ehrlichia spp. in the order Rickettsiales in ticks from Yueyang, a prefecture-level city of Hunan Province in Sothern China, and assess the potentiality of transovarial transmission of these rickettsial organisms.

METHODS

Ticks were collected from cattle in a farm in Yueyang City and the tick DNA was used as template to amplify the htrA, rrs, gltA, ompA and ompB genes of Rickettsia as well as rrs and groEL genes of Anaplasma and Ehrlichia.

RESULTS

All ticks (465) collected were the cattle tick, Rhipicephalus microplus. PCR showed the minimum infection rate (MIR) was 1.5% (7/465) for Candidatus Rickettsia xinyangensis, 1.9% (9/465) for C. Anaplasma boleense, 1.3% (6/465) for Anaplasma platys, 0.6% (3/465) for A. marginale, and 1.17% (2/465) for each of A. bovis, Ehrlichia minasensis, and a non-classified Ehrlichia sp. A human pathogen, C. Rickettsia xinyangensis and A. platys were detected in 100% (3/3) and 33.3% (2/6) laboratory-hatched larval pools from infected females respectively.

CONCLUSION

Our study revealed a diversity of pathogenic rickettsial species in R. microplus ticks from Hunan Province suggesting a threat to people and animals in China. This study also provided the first molecular evidence for the potential transovarial transmission of C. Rickettsia xinyangensis and A. platys in R. microplus, indicating that R. microplus may act as the host of these two pathogens.

Rickettsial infection in ticks from a natural area of Atlantic Forest biome in southern Brazil

From June 2013 to January 2014, blood sera samples and ticks were collected from domestic dogs and wild small mammals, and ticks from the vegetation in a preservation area of the Atlantic Forest biome (Turvo State Park), and the rural area surrounding the Park in Derrubadas municipality, state of Rio Grande do Sul, southern Brazil. Dogs were infested by Amblyomma ovale and Amblyomma aureolatum adult ticks, whereas small mammals were infested by immature stages of A. ovale, Amblyomma yucumense, Amblyomma brasiliense, Ixodes loricatus, and adults of I. loricatus. Ticks collected on vegetation were A. brasiliense, A. ovale, A. yucumense, Amblyomma incisum, and Haemaphysalis juxtakochi. Three Rickettsia species were molecularly detected in ticks: Rickettsia bellii in I. loricatus (also isolated through cell culture inoculation), Rickettsia amblyommatis in A. brasiliense, and Rickettsia rhipicephali in A. yucumense. The latter two are tick-rickettsia associations reported for the first time. Seroreactivity to Rickettsia antigens were detected in 33.5% (55/164) small mammals and 8.3% (3/36) canine sera. The present study reveals a richness of ticks and associated-rickettsiae in the largest Atlantic Forest Reserve of the state of Rio Grande do Sul, which is characterized by a rich fauna of wild mammals, typical of more preserved areas of this biome. Noteworthy, none of the detected Rickettsia species have been associated to human or animal diseases. This result contrasts to other areas of this biome in Brazil, which are endemic for tick-borne spotted fever caused by Rickettsia rickettsii or Rickettsia parkeri.

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.

Molecular Detection of Rickettsia parkeri Strain Atlantic Rainforest in Ticks Parasitizing Small Mammals in Northeastern Brazil

PURPOSE

Small mammals are important reservoirs of ticks and their pathogens in nature. However, studies reporting these associations are still rare in Brazil. In the present study, we investigated the presence of Rickettsia DNA in ticks parasitizing rodents and marsupials captured in different areas throughout the Atlantic rainforest biome, Bahia, Northeastern (NE), Brazil.

METHODS

The study was conducted in five municipalities within of the Atlantic Forest biome, Bahia state, in NE Brazil. Two campaigns were done in each municipality. For host captures Sherman and Tomahawk traps were used, and pitfall traps. After being captured, the hosts were anesthetized and their entire body examined for ticks. When ticks were detected, they were manually removed and stored in eppendorf tubes (1.5 ml) containing absolute PA ethanol for future laboratory analysis (identification of ticks and detection of Rickettsia spp.).

RESULTS

A total of 609 mammals were captured. Overall, 208 ticks of the genus Amblyomma and Ixodes were collected: A. ovale, I. loricatus and A. varium. Rickettsia DNA was detected in A. ovale and it was 99-100% of identity to the sequence deposited in GenBank as Rickettsia parkeri strain Atlantica rainforest.

CONCLUSION

These results suggest that R. parkeri strain Atlantic rainforest occurs in the region, and A. ovale is likely the vector.

Unraveling the epidemiological relationship between ticks and rickettsial infection in Africa

Tick-borne rickettsioses are emerging and re-emerging diseases of public health concern caused by over 30 species of Rickettsia. Ticks are obligate hematophagous arthropods with over 700 species of Ixodid ticks known worldwide. The escalating geographical dispersal of tick vectors and concomitant increase in the incidences of tick-borne diseases have fueled interest in the ecology of tick-borne pathogens. This review focuses on aspects of the Rickettsia pathogen, including biology, taxonomy, phylogeny, genetic diversity, epidemiology of the disease, and the role of vertebrate host in the perpetuation of rickettsioses in Africa. Our review also highlights some of the species of Rickettsia that are responsible for disease, the role of tick vectors (both hard and soft ticks) and the species of Rickettsia associated with diverse tick species across the continent. Additionally, this article emphasizes the evolutionary perspective of rickettsiae perpetuation and the possible role of amplifying vertebrate host and other small mammals, domestic animals and wildlife in the epidemiology of Rickettsia species. We also specifically, discussed the role of avian population in the epidemiology of SFG rickettsiae. Furthermore, we highlighted tick-borne rickettsioses among travelers due to African tick-bite fever (ATBF) and the challenges to surveillance of rickettsial infection, and research on rickettsiology in Africa. Our review canvasses the need for more rickettsiologists of African origin based within the continent to further research towards understanding the biology, characterization, and species distribution, including the competent tick vectors involved in their transmission of rickettsiae across the continent in collaboration with established researchers in western countries. We further highlighted the need for proper funding to encourage research despite competing demands for resources across the various sectors. We finalize by discussing the similarities between rickettsial diseases around the world and which steps need to be taken to help foster our understanding on the eco-epidemiology of rickettsioses by bridging the gap between the growing epidemiological data and the molecular characterization of Rickettsia species.

A new focus of spotted fever caused by Rickettsia parkeri in Brazil

Spotted fever (SF) is a tick-borne zoonosis caused by bacteria of the genus Rickettsia . The disease varies in severity from mild clinical forms to severe cases. In Brazil, Rickettsia rickettsii SF is the most serious rickettsiosis and can result in death if not diagnosed and treated at the onset of symptoms. The SF mild form is caused by Rickettsia parkeri strain Atlantic Rainforest, and this etiological agent has been reported in the South, Southeast and Northeast regions of the country, in areas of preserved or little antropized Atlantic Rainforest. Amblyomma ovale is the proven vector and dogs are the hosts associated with the bioagent cycle. During a SF case investigation in Paraty municipality, Rio de Janeiro State, an Atlantic Rainforest biome area in Southeastern Brazil, the human pathogen R. parkeri strain Atlantic Rainforest was detected by PCR in a sample of human skin inoculation eschar and in a female A. ovale tick collected from a dog. These results expand the known area of occurrence of this mild form rickettsiosis in Brazil. In addition, the results of the present study indicate the importance of implementing programs to control canine ectoparasites and to raise awareness of the risks of infection, signs and symptoms of SF caused by R. parkeri strain Atlantic Rainforest.

Small mammals, ticks and rickettsiae in natural and human-modified landscapes: Diversity and occurrence of Brazilian spotted fever in Brazil

We studied communities of small mammals and their ticks in endemic (E) and non-endemic (NE) areas for Brazilian spotted fever (BSF), aiming to infer if diversity parameters of parasites and hosts could be related to occurrence and prevalence of rickettsial infection, especially Rickettsia rickettsii. We compared E and NE areas in human-modified landscapes (HMLs) and natural areas (BIO) with no report of BSF cases. Composition and equitability were important components of diversity explaining differences among areas. The marsupial Didelphis albiventris was dominant in HMLs, but not in natural areas, and this opossum was the main host for the tick Amblyomma sculptum, principal vector of R. rickettsii, especially in E areas. Communities of ticks were dominated by A. sculptum, followed by Amblyomma dubitatum in E areas. In NE areas, this dominance was inverted, with more A. dubitatum than A. sculptum infesting small mammals, but the numbers of ticks were much lower than in E areas. Composition and abundance of ticks in natural areas were very dissimilar from HMLs, with the lowest tick burdens. Didelphis albiventris in E areas presented higher seroprevalence and endpoint titres against R. rickettsii than in other areas. At least three Rickettsia species, non-pathogenic to humans, were detected in natural areas (Rickettsia bellii, Rickettsia amblyommatis and 'Candidatus Rickettsia andeanae'), and only one non-pathogenic species in HMLs (R. bellii). Our results suggest that higher diversity of ticks, hosts and rickettsiae could be relevant factors in buffering the effect in BSF occurrence. Particularly for D. albiventris, its importance has to be quantified in further studies considering the epidemiological scenario of BSF.

Exploring the ecological and evolutionary relationships between Rickettsia and hard ticks in the Neotropical region

This study addresses a meta-analysis of the distribution of Rickettsia spp. in the Neotropical region, as well as their associations with ticks and vertebrates. A total of 219 published reports on Rickettsia in ticks in the target region were compiled, providing 599 records of 31 species of Rickettsia recorded in 50 species of Ixodidae. The aim is to capture the phylogenetic relationships between rickettsiae and the ticks carrying them in the target region, with a focus on the co-speciation ticks-rickettsiae. We compared the phylogeny of ticks, the records of rickettsiae, the environmental gradients colonized by ticks and the effect of the phylogenetic composition of vertebrates feeding ticks on the detection of Rickettsia in ticks. Results show that differences in rickettsial composition in ticks do not depend on the vertebrate's blood-source. This is the first time this result is demonstrated. This study pinpoints that some Neotropical rickettsial organisms are associated with well-defined phylogenetical clusters of ticks. Secondarily, and probably only in a few cases, rickettsiae share species of phylogenetically distant ticks distributed along a gradient of environmental traits in which the ticks overlap (i.e., the different strains of Rickettsia parkeri sensu lato). We outline the importance of some ticks that share hosts and habitat: these ticks may act as "bridges" for the circulation of rickettsial species. There are also many species of Rickettsia that have been detected so far in only one tick species, pointing to a tight relationship or to the lack of data preventing conclusions about the detection of these bacteria in other ticks. Two species, namely Rickettsia amblyommatis and Rickettsia bellii have been recorded in the majority of ticks in the region (mainly Amblyomma spp.) and seem to be not associated with definite tick species because they may be an essential symbiont of the ticks. We conclude that an adequate analysis of rickettsiae-ticks-habitat is necessary to address the human health issues derived from the infections by rickettsiae.

Ticks and rickettsial exposure in lowland tapirs (Tapirus terrestris) of three Brazilian biomes

This study evaluated ticks and rickettsial exposure in 220 free-ranging lowland tapirs, Tapirus terrestris, from 2006 to 2018 in selected areas of three major biomes of Brazil - Atlantic Forest, Pantanal, and Cerrado. Overall, a total of 5970 tick specimens representing the following nine species were collected from tapirs: Amblyomma brasiliense, Amblyomma coelebs, Amblyomma dubitatum, Amblyomma ovale, Amblyomma parvum, Amblyomma sculptum, Amblyomma triste, Haemaphysalis juxtakochi, and Rhipicephalus microplus. Amblyomma sculptum was the most prevalent and abundant tick species in all three biomes; however, mean intensity values for A. sculptum were significantly lower in Atlantic Forest than in the Pantanal or Cerrado, and at the same time, statistically similar among tapirs from Pantanal and Cerrado. Contrastingly, mean intensity values for A. coelebs were significantly higher in the Atlantic Forest than in the other biomes. The remaining tick species were collected in lower numbers, or were exclusive for one biome, e.g., A. brasiliense and H. juxtakochi only in the Atlantic Forest. A total of 177 blood sera (123 individuals plus 54 recaptures) were collected from tapirs and tested for the presence of reactive antibodies to six Rickettsia species by immunofluorescence assay. Overall, 69% (9/13), 49% (62/126), and 66% (25/38) tapir sera from Atlantic Forest, Pantanal and Cerrado, respectively, were seroreactive to at least one Rickettsia species, with no significant difference between the three areas. Although many tapir sera reacted simultaneously to ≥2 Rickettsia species, Rickettsia parkeri elicited highest % seroprevalence and endpoint titers, and was incriminated as the possible agent involved in a homologous reaction in tapirs from the three biomes, where A. ovale was previously found infected by R. parkeri. In fact, seroconversion to R. parkeri was demonstrated in five tapirs that were captured at least twice during the study. This study demonstrated that tapirs were found to be constantly infested by several tick species in the Atlantic Forest, Pantanal and Cerrado biomes; however, the richness of tick infestations was concordant to the tick species known to be established in each biome. Under natural conditions, lowland tapirs were shown to be exposed to tick-borne spotted fever group rickettsiae.

Maintenance of the infection by Rickettsia amblyommatis in Amblyomma cajennense sensu stricto ticks and evaluation of vector competence

Rickettsia amblyommatis has been reported infecting various tick species throughout the western hemisphere, including Amblyomma cajennense sensu stricto (s.s.). The present study aimed to evaluate whether R. amblyommatis can be maintained by transovarial transmission and transstadial passage in A. cajennense s.s. ticks, and whether these ticks are competent vectors of this rickettsial agent. We selected engorged females that were naturally infected or uninfected by R. amblyommatis, and reared their offspring (infected and control groups, respectively). Immature ticks were allowed to feed on guinea pigs, whereas adults fed on rabbits. All stages and individuals of each generation of the infected group yielded rickettsial DNA, which was not detected in any tick from the control group. No host from the control group seroconverted to R. amblyommatis. Among 16 guinea pigs and eight rabbits infested with R. amblyommatis-infected ticks, only one guinea pig seroconverted to R. amblyommatis. Some unfed adult ticks of the infected group were dissected, and DNA was extracted from their salivary glands and from their carcasses. DNA of R. amblyommatis was detected in all carcasses, but not in the salivary glands. Results of this study indicate very low vector competence of A. cajennense s.s. for R. amblyommatis. Previous studies reported domestic animals with high titers to R. amblyommatis in areas where these animals are naturally infested chiefly by A. cajennense s.s. ticks. One may consider that the vector competence of A. cajennense s.s. for R. amblyommatis could vary among tick populations and/or rickettsial strains.

Detection of tick-borne rickettsial pathogens in naturally infected dogs and dog-associated ticks in Medellin, Colombia

Tick-borne rickettsial pathogens (TBRP) are important causes of infections in both dogs and humans. Dogs play an important role as a biological host for several tick species and can serve as sentinels for rickettsial infections. Our aim was to determine the presence of TBRP in dogs and in dog-associated ticks and their potential risk to human diseases in Medellin, Colombia. DNA for E. canis (16S rRNA and dsb) and A. platys (groEl) was detected in 17.6% (53/300) and 2.6% (8/300) of dogs, respectively. Antibodies against Ehrlichia spp. 82 (27.3%) and Anaplasma spp. 8 (2.6%) were detected in dogs. Antibody reactivity against both agents were found in 16 dogs (5.3%). Eight dogs showed antibody for Rickettsia spp. with titers that suggest 3 of them had a probable exposure to R. parkeri. Rhipicephalus sanguineus s.l. (178/193) was the main tick in dogs, followed by R. microplus (15/193). The minimum infection rates (MIR) in R. sanguineus were 11.8% for E. canis and 3.4% for A. platys. E. canis and A. platys are the main TBRP infecting dogs and ticks and R. sanguineus s.l. is likely involved in the transmission of both agents. Interestingly, we found serological evidence of exposure in dogs for spotted fever group rickettsiae.

Seven years of evaluation of ectoparasites and vector-borne pathogens among ring-tailed coatis in an urban park in southeastern Brazil

Wild animals have been recognized as potential reservoirs of vector-borne pathogens. Proximity between these animals and urban areas increases the need to know which pathogens these are and whether they can infect domestic animals and humans. In Mangabeiras Municipal Park in Belo Horizonte, Brazil, coatis live near the urban area, which is mainly occupied by human residents and their domestic animals. Therefore, the objective of this study was to detect, through molecular and direct methods, the presence of ectoparasites and hemoparasites in coatis. A total of 216 samples were collected, of which 209 samples were from first-captures and seven were from recaptures. The following parasites were found: ticks of the genus Amblyomma, lice of the species Neotrichodectes pallidus and fleas of the species Rhopalopsyllus lutzi lutzi and Ctenocephalides felis felis. All the samples were negative for the family Anaplasmataceae and the species Leishmania sp. and Trypanosoma cruzi. The hemoparasites Trypanosoma evansi, Hepatozoon procyonis, Babesia sp. and Sarcocystis neurona were found. The area of the present study is not endemic for T. evansi, which therefore suggests that these coatis may be acting as reservoirs or sentinels of this parasite. This finding is of great epidemiological importance and should be investigated more closely. Thus, this study showed that there is a great variety of pathogens in the park that transit among coatis and, probably, among other animals that inhabit or live close to the park.

Serosurvey on rickettsiae of the spotted fever group and Rickettsia bellii among dogs in the state of Goiás, Brazil

The purpose of this study was to do a serological survey on three rickettsial species: Rickettsia rickettsii and Rickettsia parkeri, two species of the spotted fever group (SFG) that are considered to be great importance for public health; and Rickettsia bellii, a species of unknown pathogenicity that infects a variety of human-biting ticks. Serum samples from 273 dogs were tested using the indirect immunofluorescence assay (IFA). A total of 52 samples (19.04%) were seropositive for at least one of the three Rickettsia spp. antigens. Thirty-eight (73.07%), twelve (23.07%) and one (1.92%) of these dogs showed homologous reactions to R. bellii, R. rickettsii and R. parkeri, respectively. Our results showed that the seroprevalence of Rickettsia spp. was relatively low. However, the positive serological tests indicated that these dogs had become infected by these agents at some point in their lives. Lastly, our study adds to the previous knowledge on the epidemiology of rickettsiosis in the state of Goiás by doing the first record of detection of anti-R. rickettsii, R. parkeri and R. bellii antibodies by IFA among dogs, thus indicating that these agents may be circulating in the dog population analyzed.

Implications of domestic dogs in the epidemiology of Rickettsia parkeri strain Atlantic rainforest and Rangelia vitalii in Southeastern Brazil

This study aimed to evaluate the occurrence of diseases transmitted by Amblyomma ovale in 61 dogs monitored for three years through collections of ticks and blood, interviews, telemetry and camera traps in three areas of Serra do Mar State Park, Brazil. Blood samples were used to investigate infection by Rangelia vitalii by real-time TaqMan PCR and Rickettsia parkeri by IIFA. The collected ticks were submitted to conventional PCR to investigate the presence of R. parkeri . These data were compared with the monitoring results and interviews with the owners. Dogs considered as companion presented a risk of infection by R. parkeri strain Mata Atlantica 5.4 times higher than those not considered as companion (p = 0.009). Dogs that had at least one A. ovale collected during the campaigns had a 10 times higher risk of infection by R. parkeri strain Mata Atlantica than those who did not (p = 0.009). One dog positive for R. vitalii by real-time TaqMan PCR was parasitized by A. ovale frequently during monitoring. Sequenced ompaA - positive DNA samples had 100% identity of R. parkeri strain Mata Atlantica clone As106. From the findings, it is urgent to control domestic dogs around rainforests to reduce zoonoses transmission.

Epidemiological aspects of Rickettsia parkeri in the Atlantic forest biome of Espírito Santo state, Brazil

Since 2010, a new rickettsiosis caused by Rickettsia parkeri, a species included in the spotted fever group (SFG) and transmitted by the tick Amblyomma ovale, has been described in Brazil. Considering that A. ovale does occur in the Espírito Santo state (ES), the present study aimed at preliminarily describing the epidemiology of R. parkeri in the Atlantic forest of this state. Between June 2016 and September 2018, 33 villages from nine municipalities of the ES were included in a study for the molecular detection and isolation of SFG rickettsiae from adult Amblyomma ticks collected on dogs with free access to the forest. Serologic screenings against SFG rickettsiae in these animals and their owners (humans) were performed through immunofluorescence assay (IFA) using antigens of Rickettsia rickettsii and R. parkeri. Additionally, local health secretariats were informed on clinical manifestations of R. parkeri infection and told to communicate any suspected case. A total of 280 adult ticks were collected and taxonomically classified as A. ovale (n = 152), Amblyomma aureolatum (n = 127) and Amblyomma sculptum (n = 1). Overall, Rickettsia DNA was detected in 12/266 ticks. The sequencing of PCR products revealed that 0.7% (1/144) and 0.8% (1/121) of the analyzed A. ovale and A. aureolatum ticks were infected by R. parkeri strain Atlantic rainforest, respectively, and 8.3% (10/121) of the A. aureolatum ticks infected by Rickettsia bellii. Among the above PCR-positive ticks, only one isolate from one A. aureolatum tick was successfully established in the laboratory. DNA extracted from the third passage of this isolate was designated as strain M9A and molecularly characterized using primers targeting the Rickettsia gltA gene, whose sequence matched 100% the corresponding sequences of R. bellii. Seroprevalence against SFG rickettsiae in sampled dogs (n = 83) was 41% or 57%, depending on the rickettsial antigen (R. rickettsii strain Taiaçu or R. parkeri strain Atlantic rainforest, respectively). A total of 37 (45%) canine sera showed titers to R. parkeri at least fourfold higher than to R. rickettsii antigen. Among humans, 10% (4/41) of the samples reacted to at least one rickettsial antigen, with the highest endpoint titer varying from 64 to 128 for R. rickettsii and R. parkeri; no human serum showed ≥4-fold difference between the highest endpoint titers. Finally, during the study period, suspicions on cases of R. parkeri-rickettsiosis were not informed by the health secretariats. Our results confirm the presence and exposure to R. parkeri strain Atlantic rainforest, associated with two anthropophilic tick species (A. ovale and A. aureolatum) parasitizing domestic dogs with unrestrained access to forest areas. Consequently, the occurrence of R. parkeri infection in humans inhabiting the Atlantic forests of ES should not be discarded.

A human case of spotted fever caused by Rickettsia parkeri strain Atlantic rainforest and its association to the tick Amblyomma ovale

BACKGROUND

Rickettsia parkeri strain Atlantic rainforest has emerged in Brazil during the last 10 years, with three laboratory-confirmed human cases. While these cases were epidemiologically associated with the tick Amblyomma ovale, in none of them the tick specimens that bit the patients could be identified.

RESULTS

We report a clinical case of spotted fever rickettsiosis that was acquired in an Atlantic forest area in Bahia state, northeast Brazil. The case was determined to be caused by R. parkeri strain Atlantic rainforest, based on molecular analysis of the crust removed from the tick bite site (inoculation eschar) of the patients' skin. DNA extracted from the crust yielded partial sequences of three rickettsial genes (gltA, ompA and ompB), which were 99-100% identical to R. parkeri strain Atlantic rainforest. The tick specimen that was attached to patient skin was identified as a female of A. ovale.

CONCLUSIONS

We report the fourth confirmed case of spotted fever rickettsiosis caused by R. parkeri strain Atlantic rainforest, providing to our knowledge for the first time, direct evidence of R. parkeri strain Atlantic rainforest transmission by A. ovale.

Multi-locus phylogenetic analysis groups the New World bacterium Rickettsia sp. strain ApPR with the Old World species R. africae; proposal of "Candidatus Rickettsia paranaensis"

Rickettsia parkeri sensu stricto (s.s.) is an emerging human pathogen in the Americas. Comprehension of the etiology of R. parkeri infections in South America is complicated by the existence of genetic variants (Atlantic rainforest, NOD and Parvitarsum) of this species that are associated with specific groups of Amblyomma ticks. The rickettsial bacterium strain ApPR was first reported in Amblyomma parkeri ticks in Southern Brazil in 2012 and was considered, based on sequencing of fragments of the gltA, htrA, ompA and ompB genes, to represent yet another genetic variant of R. parkeri. In the current work, a multi-locus phylogenetic analysis employing additional genes and intragenic regions was performed using DNA extracted from (a) larvae of A. parkeri and Amblyomma species haplotype Nazaré ticks collected from wild birds, (b) a nymph of Amblyomma sp. haplotype Nazaré recovered from a monkey (Callicebus nigrifons), representing the first report of that tick parasitizing a non-human primate and (c) from a cultured isolate of ApPR, isolated from colony-reared adults of Amblyomma geayi. Phylogenetic inference performed using Maximum-likelihood (ML), Maximum Parsimony (MP) and Bayesian (B) methods, consistently placed strain ApPR outside the New World R. parkeri complex and instead grouped it in proximity to the Old World species Rickettsia africae and Rickettsia sibirica. Estimates of evolutionary divergence provided additional support for the inferred phylogenetic relationship. Given the clear evolutionary distance between strain ApPR and R. parkeri we propose the recognition of "Candidatus Rickettsia paranaensis".

Serologic and molecular survey of Rickettsia spp. in dogs, horses and ticks from the Atlantic rainforest of the state of Bahia, Brazil

Tick-borne spotted fever in Brazil is known to be caused by two agents, Rickettsia rickettsii and Rickettsia parkeri. Nothing was known about these agents in one area of the Atlantic rainforest biome of Bahia state, where during March to June 2016, 356 rural dogs and 69 horses were sampled and their sera were processed through indirect immunofluorescence assay against antigens of R. rickettsii, R. parkeri, Rickettsia amblyommatis and Rickettsia bellii. Ticks collected from these dogs and horses were molecularly tested for the presence of rickettsial DNA. Overall, 16.4% (58/356) dogs and 24.6% (17/69) horses were seroreactive to Rickettsia spp. Five tick species, Rhipicephalus sanguineus sensu lato (s.l.), Amblyomma ovale, A. sculptum, R. microplus, and A. naponense, were collected from dogs, whereas horses were infested by A. sculptum and Dermacentor nitens. A total of 242 ticks from dogs and 62 from horses were analyzed by PCR targeting rickettsiae, which were detected in only 4/27 (14.8%) A. ovale. Fragments of the rickettsial gltA and ompA genes from these four ticks were 100% identical to the Atlantic rainforest strain of R. parkeri. The presence of A. ovale on dogs was positively associated with local canine seroreactivity to R. parkeri. Our results provide evidence for the transmission of R. parkeri strain Atlantic rainforest from A. ovale to domestic dogs within the rural area of Ilhéus, similarly to other areas of the Atlantic rainforest biome of Brazil, where human cases of R. parkeri-caused spotted fever have been reported.

A high gene flow in populations of Amblyomma ovale ticks found in distinct fragments of Brazilian Atlantic rainforest

The genetic structure of populations of the tick Amblyomma ovale from five distinct areas of the Brazilian Atlantic rainforest was evaluated via DNA sequencing and associated with the presence of domestic dogs acting as hosts at the edge of forest fragments. Ticks were collected from domestic dogs and from the environment between 2015 and 2017. Four collection areas were located in the surroundings and within the Serra do Mar State Park, São Paulo State (23°37'21"S, 45°24'43"W), where dogs were bimonthly monitored along 2 years using camera traps and GSM trackers. To determine the spatial limits of genetic structure, ticks collected upon dogs living near the Serra do Baturié, Ceará State (4°15'40"S, 38°55'54"W) were included as well. A total of 39 haplotypes of 16S rRNA and Cox 1 mitochondrial genes sequences were observed, with 27 of them coming from areas within the Serra do Mar State Park. No haplotype was shared between the Serra do Mar and the Serra do Baturié indicating isolation of tick populations at the scale of 2000 km. Although three different haplotype lineages of A. ovale occurred within the Serra do Mar State Park, no genetic structure was found across the study sites within this park, suggesting high tick gene flow across a range of 45 km. Monitoring data from domestic dogs and wild carnivores showed that these species share the same habitats at the forest edge, with dogs playing a likely limited role in tick dispersal. Our findings have important implications for understanding the genetic structure of wide spread A. ovale along Brazilian rainforest remnants, which can further be associated to tick-borne infectious agents, such as Rickettsia parkeri, and used for predicting future patterns of tick diversity in the Brazilian Atlantic rainforest.

Ticks, rickettsial and erlichial infection in small mammals from Atlantic forest remnants in northeastern Brazil

We evaluated infection by Rickettsia spp. and Ehrlichia spp in small mammals and their ticks from two Atlantic forest conservation areas in the state of Rio Grande do Norte, northeastern Brazil. A total of 39 small mammals were captured during 2012–2013, encompassing 33 marsupials (29 Didelphis albiventris, four Monodelphis domestica), three Cricetidae rodents (two Necromys lasiurus, one Rattus rattus), one Caviomorpha rodent (Thrichomys apereoides) and two armadillos (Euphractus sexcinctus). The ticks Amblyomma auricularium, Ixodes loricatus, and Ornithodoros mimon were collected from D. albiventris, whereas only A. auricularium was collected from armadillos. Through immunofluorescence assay with Rickettsia spp. antigens, 6/28 (21%) D. albiventris and the single R. rattus specimen reacted to at least one rickettsial antigen, with highest seroprevalence and endpoint titers to Rickettsia amblyommatis. A total of 150 ticks (126 A. auricularium, nine I. loricatus, 15 O. mimon) was tested for rickettsial infection by PCR, which detected only R. amblyommatis in most of the A. auricularium ticks. Lung and spleen samples were collected from small mammals (two N. lasiurus, six D. albiventris, three M. domestica, one T. apereoides, one R. rattus) and were tested by PCR for Anaplasmataceae agents. The spleen from one D. albiventris contained a new ehrlichial agent, here named as Ehrlichia sp. strain Natal. Phylogenetic analysis inferred from the dsb gene of Ehrlichia spp. indicates that this novel agent is potentially a new species. Future studies should monitor the possible role of rickettsial and/or ehrlichial microorganisms as agents of emerging diseases in these degraded areas of Atlantic forest, just as has occurred with other agents in degraded areas of this biome in southeastern Brazil.

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Amblyomma auricularium, Ixodes loricatus and Ornithodoros mimon ticks were found.

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Infection by Rickettsia amblyommatis was detected in A. auricularium ticks.

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Wild small mammals presented serological evidence of R. amblyommatis infection.

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A potentially novel Ehrlichia species infected the opossum Didelphis albiventris.

First molecular detection of Rickettsia sp. strain Atlantic rainforest in Amblyomma ovale ticks from Espírito Santo state, Brazil

Espírito Santo state (southeastern Brazil) is considered an endemic area for spotted fever group rickettsioses. In February 2017, we received in our laboratory seven unfed Amblyomma ovale adult ticks collected by a farmer from his clothes and body (not attached) during a working day in the rural area of Ibiraçu municipality, Espírito Santo state. By polymerase chain reaction (PCR) analyses, targeting gltA and ompA rickettsial genes, the DNA of Rickettsia was detected in 6/7 (85.7%) A. ovale. In all cases, DNA sequencing of PCR products revealed that consensus sequences of both genes were 100% identical to gltA and ompA corresponding sequences of Rickettsia sp. strain Atlantic rainforest retrieved from GenBank. This study reports the first molecular detection of Rickettsia sp. strain Atlantic rainforest in A. ovale ticks from Espírito Santo state. Our findings indicate a new Brazilian state in the southeast region at risk of human infection with this tick-borne emerging rickettsial agent.

Ticks parasitizing wild mammals in Atlantic Forest areas in the state of Rio de Janeiro, Brazil

Mammals captured in the Serra dos Órgãos National Park (PARNASO) and the Pedra Branca State Park (PBSP) between 2012 and 2015 were examined for the presence of ticks. In total, 140 mammals were examined, and 34 specimens were found to be parasitized by ticks. Didelphis aurita, Akodon montensis and Oligoryzomys nigripes were the species most parasitized. From these specimens, 146 ticks were collected, including 10 larvae. The ticks belonged to eight species: one in the genus Ixodes and seven in the genus Amblyomma. This study reports new associations of ticks and wild mammals in Brazil.

Neglected aspects of tick-borne rickettsioses

Rickettsioses are among the oldest known infectious diseases. In spite of this, and of the extensive research carried out, many aspects of the biology and epidemiology of tick-borne rickettsiae are far from being completely understood. Their association with arthropod vectors, the importance of vertebrates as reservoirs, the rarity of clinical signs in animals, or the interactions of pathogenic species with rickettsial endosymbionts and with the host intracellular environment, are only some examples. Moreover, new rickettsiae are continuously being discovered. In this review, we focus on the ‘neglected’ aspects of tick-borne rickettsioses and on the gaps in knowledge, which could help to explain why these infections are still emerging and re-emerging threats worldwide.

The rice rat Euryoryzomys russatus, a competent amplifying host of Rickettsia parkeri strain Atlantic rainforest for the tick Amblyomma ovale

Rickettsia parkeri strain Atlantic rainforest (SAR) is the etiological agent of a spotted fever group rickettsiosis in Brazil, where it is transmitted to humans by the tick Amblyomma ovale. A previous study demonstrated that R. parkeri SAR was successfully maintained in A. ovale ticks by transstadial and transovarial passages; however, because this agent induced lower reproduction rates in A. ovale, the participation of a vertebrate amplifier host, yet to be determined, was speculated. Since the rice rat Euryoryzomys russatus was demonstrated to be the most important host for immature stages of A. ovale in a focus of R. parkeri SAR transmission, the present study evaluated the competence of rice rats to act as amplifying host of R. parkeri SAR for A. ovale ticks. Rice rats were infested with R. parkeri SAR-infected A. ovale nymphs, and four days later with uninfected A. ovale larvae. Rickettsial transmission to rats was confirmed by seroconversion to R. parkeri antigens. Detached engorged larvae were allowed to molt to nymphs, in which rickettsial DNA was detected in up to 60% (mean: 20%) of the specimens. When part of these nymphs was allowed to feed on susceptible rice rats, rickettsial transmission was confirmed by seroconversion, indicating that there was successful horizontal transmission of R. parkeri SAR from infected nymphs to uninfected larvae in the previous acquisition infestations. Because we used naïve, susceptible rats, we infer that this horizontal transmission occurred via a systemic infection (rickettsemia) in the rat. Our results, coupled with previous epidemiological studies, suggest that under natural conditions rice rats could be acting as amplifying hosts of R. parkeri SAR to A. ovale ticks.

Phylogenetic Evidence for the Existence of Multiple Strains of Rickettsia parkeri in the New World

The bacterium Rickettsia parkeri has been reported to infect ticks of the "Amblyomma maculatum species complex" in the New World, where it causes spotted fever illness in humans. In South America, three additional rickettsial strains, namely, Atlantic rainforest, NOD, and Parvitarsum, have been isolated from the ticks Amblyomma ovale, Amblyomma nodosum, and Amblyomma parvitarsum, respectively. These three strains are phylogenetically closely related to R. parkeri, Rickettsia africae, and Rickettsia sibirica Herein, we performed a robust phylogenetic analysis encompassing 5 genes (gltA, ompA, virB4, dnaA, and dnaK) and 3 intergenic spacers (mppE-pur, rrl-rrf-ITS, and rpmE-tRNA^fMet) from 41 rickettsial isolates, including different isolates of R. parkeri, R. africae, R. sibirica, Rickettsia conorii, and strains Atlantic rainforest, NOD, and Parvitarsum. In our phylogenetic analyses, all New World isolates grouped in a major clade distinct from the Old World Rickettsia species (R. conorii, R. sibirica, and R. africae). This New World clade was subdivided into the following 4 clades: the R. parkerisensu stricto clade, comprising the type strain Maculatum 20 and all other isolates of R. parkeri from North and South America, associated with ticks of the A. maculatum species complex; the strain NOD clade, comprising two South American isolates from A. nodosum ticks; the Parvitarsum clade, comprising two South American isolates from A. parvitarsum ticks; and the strain Atlantic rainforest clade, comprising six South American isolates from the A. ovale species complex (A. ovale or Amblyomma aureolatum). Under such evidences, we propose that strains Atlantic rainforest, NOD, and Parvitarsum are South American strains of R. parkeriIMPORTANCE Since the description of Rickettsia parkeri infecting ticks of the "Amblyomma maculatum species complex" and humans in the New World, three novel phylogenetic close-related rickettsial isolates were reported in South America. Herein, we provide genetic evidence that these novel isolates, namely, strains Atlantic rainforest, NOD, and Parvitarsum, are South American strains of R. parkeri. Interestingly, each of these R. parkeri strains seems to be primarily associated with a tick species group, namely, R. parkerisensu stricto with the "Amblyomma maculatum species group," R. parkeri strain NOD with Amblyomma nodosum, R. parkeri strain Parvitarsum with Amblyomma parvitarsum, and R. parkeri strain Atlantic rainforest with the "Amblyomma ovale species group." Such rickettsial strain-tick species specificity suggests a coevolution of each tick-strain association. Finally, because R. parkerisensu stricto and R. parkeri strain Atlantic rainforest are human pathogens, the potential of R. parkeri strains NOD and Parvitarsum to be human pathogens cannot be discarded.

Experimental infection of Rickettsia parkeri in the Rhipicephalus microplus tick

This study aimed to evaluate, by means of artificial feeding, the interaction between a pathogenic rickettsia and the hard tick R. microplus. We used partially engorged females fed on calves free of Rickettsia spp. Group 1 (G1), containing 20 ticks, was fed bovine blood only. Group 2 (G2), containing 20 ticks, was fed blood containing uninfected VERO cells, and group 3 (G3), containing 40 ticks, was fed blood containing VERO cells infected with Rickettsia parkeri. Biological parameters of the non-parasitic phase and a possible bacterial transmission to the tick eggs and to guinea pigs were evaluated. At the end of oviposition, all G3 females were PCR-positive for genes specific for the genus Rickettsia. Although no guinea pigs were infected, the experimental infection of R. microplus by R. parkeri caused a deleterious effect on the oviposition and provided the first report of transovarian transmission of rickettsia in this tick.

Transmission dynamics and control of Rickettsia rickettsii in populations of Hydrochoerus hydrochaeris and Amblyomma sculptum

BACKGROUND

Brazilian Spotted Fever (BSF), caused by the bacterium Rickettsia rickettsii, is the tick-borne disease that generates the largest number of human deaths in the world. In Brazil, the current increase of BSF human cases has been associated with the presence and expansion of capybaras Hydrochoerus hydrochaeris, which act as primary hosts for the tick Amblyomma sculptum, vector of the R. rickettsii in this area.

METHODS

We proposed a semi-discrete-time stochastic model to evaluate the role of capybaras in the transmission dynamics of R. rickettsii. Through a sensitivity analysis, we identified the parameters with significant influence on the R. rickettsii establishment. Afterward, we implemented the Gillespie's algorithm to simulate the impact of potential public health interventions to prevent BSF human cases.

RESULTS

The introduction of a single infected capybara with at least one infected attached tick is enough to trigger the disease in a non-endemic area. We found that to avoid the formation of new BSF-endemic areas, it is crucial to impede the emigration of capybaras from endemic areas by reducing their birth rate by more than 58%. Model results were corroborated by ex-situ data generated from field studies, and this supports our proposal to prevent BSF human cases by implementing control strategies focused on capybaras.

CONCLUSION

The proposed stochastic model illustrates how strategies for the control and prevention of vector-borne infectious diseases can be focused on amplifier hosts management practices. This work provides a basis for future prevention strategies for other neglected vector-borne diseases.

Molecular analyses reveal an abundant diversity of ticks and rickettsial agents associated with wild birds in two regions of primary Brazilian Atlantic Rainforest

Brazilian wild birds are recognized as frequent and important hosts for immature stages of more than half of the 32 recognized species of Amblyomma ticks recorded in that country. Several species of Amblyomma harbor rickettsial agents, including members of the spotted fever group (SFG). Most studies on this topic relied primarily on morphological characterization and reported large portions of the collected ticks at the genus rather than species level. Clearly, this factor may have contributed to an underestimation of tick diversity and distribution and makes comparisons between studies difficult. The current investigation combined morphological and molecular analyses to assess the diversity of ticks and rickettsial agents associated with wild birds, captured in two regions of native Atlantic rainforest, in the state of Rio de Janeiro, Brazil. A total of 910 birds were captured, representing two orders, 34 families and 106 species, among which 93 specimens (10.2%), were parasitized by 138 immature ticks (60 larvae and 78 nymphs), representing 10 recognized species of the genus Amblyomma; together with two reasonably well classified haplotypes (Amblyomma sp. haplotype Nazaré and Amblyomma sp. strain USNTC 6792). Amplification by PCR and sequencing of rickettsial genes (htrA, gltA, ompA and ompB), demonstrated the presence of Rickettsia DNA in 48 (34%) of the ticks. Specifically, Rickettsia bellii was detected in a single larva and a single nymph of A. aureolatum; R. amblyomatis was found in 16 of 37 A. longirostre and was recorded for the first time in three nymphs of A. calcaratum; R. rhipicephali was detected in 9 (47%) of 19 Amblyomma sp. haplotype Nazaré ticks. The remaining ticks were infected with genetic variants of R. parkeri, namely strain ApPR in 12 A. parkeri and seven Amblyomma sp. haplotype Nazaré ticks, with the strain NOD found in two specimens of A. nodosum. Interestingly, a single larvae of A. ovale was shown to be infected with the emerging human pathogen Rickettsia sp. strain Atlantic rainforest (ARF), suggesting a possible role for birds in the dispersal of ticks infected with this variant of R. parkeri. The diversity of ticks and Rickettsia recorded in this study is, to our knowledge, the most abundant recorded to date in Brazil and highlighted the value of employing methods capable of providing species level identification of the ixodofauna of wild birds.

Ecology of a tick-borne spotted fever in southern Brazil

Rio Grande do Sul is the southernmost state of Brazil, bordering Uruguay. Clinical cases of spotted fever group (SFG) rickettsiosis were recently reported in Rio Grande do Sul. None of these cases was lethal, and all were confirmed by seroconversion to R. rickettsii antigens. Because serological cross-reactions are well known to occur between different SFG agents, the SFG agent responsible for the clinical cases remains unknown in Rio Grande do Sul, where no rickettsial agent is known to infect ticks. During 2013-2014, ticks and blood sera samples were collected from domestic dogs and wild small mammals, and from the vegetation in a SFG-endemic area of Rio Grande do Sul. Dogs were infested by Amblyomma ovale adult ticks, whereas small mammals were infested by immature stages of A. ovale, Ixodes loricatus, and adults of I. loricatus. Ticks collected on vegetation were adults of A. ovale, and immature stages of A. ovale, Amblyomma dubitatum, and Amblyomma longirostre. Three Rickettsia species were detected: Rickettsia bellii in I. loricatus, Rickettsia amblyommii in A. longirostre, and a Rickettsia parkeri-like agent (Rickettsia sp. strain Atlantic rainforest) in A. ovale. Seroreactivity to SFG antigens were detected in 19.7 % (27/137) canine and 37.5 % (15/40) small mammal sera, with highest titers to R. parkeri. Results indicate that the R. parkeri-like agent, strain Atlantic rainforest, is circulating between A. ovale ticks, dogs and small mammals in the study area, suggesting that this SFG pathogen could be one of the etiological agents of SFG clinical cases in Rio Grande do Sul.

Genetic identification of Rickettsia sp. strain Atlantic rainforest in an endemic area of a mild spotted fever in Rio Grande do Sul state, Southern Brazil

Rickettsia sp. strain Atlantic rainforest causes a less severe rickettsiosis, with two cases confirmed until now. The tick species Amblyomma ovale is appointed as the main vector of this bacterium. The southern region of Brazil has reported patients with spotted fever who have milder symptoms. In 2013, during an investigation of rickettsiosis cases, an A. ovale tick was found attached to a man in an area where there were two cases. The parasite was processed for molecular analysis and the rickettsial infection was confirmed based on phylogenetic analysis of genes ompA, ompB and geneD (sca4). In the present study the human pathogenic Rickettsia sp. strain Atlantic rainforest was identified in the state of Rio Grande do Sul, Southern Brazil. Since A. ovale, its main vector, is found frequently parasitizing dogs, animals that can cross international borders freely in southern Brazil, this bacteria can bring major concerns in terms of public health.

Infection of Amblyomma ovale with Rickettsia species Atlantic rainforest in Serra do Mar, São Paulo State, Brazil

Rickettsia rickettsii and Rickettsia sp. strain Atlantic rainforest, that is considered to represent a genetic variant of Rickettsia parkeri, are confirmed as being capable of infecting humans in Brazil. This study reports the detection and characterization, by PCR and nucleotide sequencing, of Rickettsia sp. strain Atlantic rain forest in Amblyomma ovale parasitizing a human, in ticks infesting dogs and in free-living ticks collected from the environment where the human infestation was recorded. The data contribute to our knowledge of infection rates in A. ovale with Rickettsia sp. strain Atlantic rainforest and identified an additional location in the state of São Paulo populated with ticks infected with this emerging pathogen.

Isolation of the Pathogen Rickettsia sp. Strain Atlantic Rainforest From Its Presumed Tick Vector, Amblyomma ovale (Acari: Ixodidae), From Two Areas of Brazil

In this study, Amblyomma ovale Koch ticks were collected from domestic dogs in two localities of the Atlantic rainforest biome of Brazil: 1) the Paty Valley of the Chapada Diamantina National Park, Bahia state (northeastern Brazil), and 2) Adrianópolis, Paraná state (southern Brazil). Ticks were screened for the presence of Rickettsia-like structures by the hemolymph test with Giménez staining, and then processed for isolation of rickettsiae in Vero cell culture by the shell-vial technique. Rickettsiae were isolated from one A. ovale tick of each of the two localities. The two isolates were successfully established in the laboratory with several passages, each one reaching >90% infection of the cells. The two isolates were identified as the spotted fever group (SFG) agent Rickettsia sp. strain Atlantic rainforest, as their gltA (350 bp), ompB (781 bp), and ompA (567 bp) gene fragments were 100% equal to GenBank corresponding sequences of the original strain Atlantic rainforest, reported to be infecting a human in southeastern Brazil, and also 100% equal to the available ompA sequence of strain Bahia, reported to be infecting a human in Paty Valley, the same area of the present study in Bahia state. Ten dogs from Paty Valley were serologically tested against rickettsial antigens by the indirect immunofluorescence antibody test. At least 60% of them were seroreactive to SFG rickettsiae. The role of A. ovale as vector of Rickettsia sp. strain Atlantic rainforest in the Paty Valley area, as well as in other parts of Latin America, is discussed.

Rickettsia sp. Strain Atlantic Rainforest Infection in a Patient from a Spotted Fever-Endemic Area in Southern Brazil

Santa Catarina State in southern Brazil is the state with the second highest number of laboratory-confirmed cases of spotted fever illness in Brazil. However, all these cases were confirmed solely by serological analysis (seroconversion to spotted fever group rickettsiae), which has not allowed identification of the rickettsial agent. Here, a clinical case of spotted fever illness from Santa Catarina is shown by seroconversion and molecular analysis to be caused by Rickettsia sp. strain Atlantic rainforest. This is the third confirmed clinical case due to this emerging rickettsial agent in Brazil. Like the previous two cases, the patient presented an inoculation eschar at the tick bite site. Our molecular diagnosis was performed on DNA extracted from the crust removed from the eschar. These results are supported by previous epidemiological studies in Santa Catarina, which showed that nearly 10% of the most common human-biting ticks were infected by Rickettsia sp. strain Atlantic rainforest.