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.

Ticks (Acari: Ixodidae) on marsh deer (Blastocerus dichotomus) at a conservation center: infestation and Rickettsia parkeri infection dynamics along nine years.

The objective of this work was to evaluate the relationship between the populations of the ticks Amblyomma triste Koch, 1844, Rhipicephalus microplus (Canestrini, 1888), Amblyomma sculptum Berlese, 1888, the pathogenic bacteria Rickettsia parkeri and a marsh deer (Blastocerus dichotomus) population after its removal from a pristine environment. For this purpose, ticks were collected from the cervical region of deer at the Marsh Deer Conservation Center in Promissão, São Paulo State, Brazil for nine consecutive years (2000 - 2008). Deer in captivity at the Center were kept in 2,000 m² paddocks surrounded by two-meter-high fences in the Tiete-river marsh. In total, 1,012 ticks of 26 deer were collected. Prevalence of the species A. triste among tick-infested hosts was the highest in the first triennium but decreased to the second and further to the third triennium. In contrast, the R. microplus prevalence amidst infested host population, increased from the first to the third triennium and was the species that attained the highest infestation intensity. Amblyomma sculptum was the tick with the lowest infestation prevalence and intensity throughout the period. The change in the proportion between the two most prevalent species was attributed to the new environment, specifically its restricted size and within it a dry area more suitable for R. microplus. DNA of 424 ticks processed in 276 pools was tested for Rickettsia genetic material by polymerase chain reactions (PCR). Twenty samples of the study were positive for the rickettsial gltA gene. Of these, 18 were from A. triste ticks and revealed the presence of the ompA spotted fever group gene as well. Eleven samples were sequenced and showed 100% identity with R. parkeri sensu stricto. Two samples from R. microplus did not amplify ompA gene neither yielded product in a PCR specific for Rickettsia bellii. Sequencing of the gltA gene in the DNA of these two ticks was also 100% identical with R. parkeri s.s. In conclusion, the changes in the deer environment modified the tick populations but maintained, at least temporary, R. parkeri bacteria in A. triste ticks. Rhipicephalus microplus was refractory to the R. parkeri infection and bacterial DNA in this tick species indicated DNA spill over from other tick species. It was demonstrated that captive marsh deer may sustain cattle tick populations on its own. This would hardly occur under pristine conditions because of the inadequacy the marsh deer´s naturally humid habitat for the cattle tick. However, deer transportations of R. microplus ticks from one farm to another may occur whenever habitat loss pushes this wild animal towards farms.

Clinical and epidemiological comparison of Rickettsia parkeri rickettsiosis, related to Amblyomma triste and Amblyomma tigrinum, in Argentina.

The aim of this work was to compare the epidemiological and clinical characteristics of Rickettsia parkeri rickettsiosis related to Amblyomma triste and Amblyomma tigrinum ecological regions in Argentina. We reviewed cases of R. parkeri rickettsiosis from 2007 to 2017 evaluated at Muñiz Hospital, directly or through referral. Univariate analysis was used to examine the association between different variables and the disease related by each vector species. The eighteen cases of R. parkeri rickettsiosis included had fever, inoculation eschar and all except one had rash. Regional differences in epidemiological variables were identified, depending on the vector. There was a significantly increased risk of exposure to A. tigrinum in peri-domestic areas (odd ratio 12, p = 0.02), whereas an increased risk of exposure to A. triste was evident in wildlife areas (odd ratio 12, p = 0.02). Seasonality of R. parkeri rickettsiosis differed based on its vector. Cases associated with A. triste occurred predominantly during spring and summer, whereas those associated with A. tigrinum occurred during fall, winter, and springtime. Exanthema was maculopapular (13/18), maculo-vesicular (3/18) or petechial (1/18). No clinical differences were identified depending on the vector.

The Amblyomma maculatum Koch, 1844 (Acari: Ixodidae) group of ticks: phenotypic plasticity or incipient speciation?

BACKGROUND: The goal of this study was to reassess the taxonomic status of A. maculatum, A. triste and A. tigrinum by phylogenetic analysis of five molecular markers [four mitochondrial: 12S rDNA, 16S rDNA, the control region (DL) and cytochrome c oxidase 1 (cox1), and one nuclear: ribosomal intergenic transcribed spacer 2 (ITS2)]. In addition, the phenotypic diversity of adult ticks identified as A. maculatum and A. triste from geographically distinct populations was thoroughly re-examined. RESULTS: Microscopic examination identified four putative morphotypes distinguishable by disjunct geographical ranges, but very scant fixed characters. Analysis of the separated mitochondrial datasets mostly resulted in conflicting tree topologies. Nuclear gene sequences were almost identical throughout the geographical ranges of the two species, suggesting a very recent, almost explosive radiation of the terminal operational taxonomic units. Analysis of concatenated molecular datasets was more informative and indicated that, although genetically very close to the A. maculatum - A. triste lineage, A. tigrinum was a monophyletic separate entity. Within the A. maculatum - A. triste cluster, three main clades were supported. The two morphotypes, corresponding to the western North American and eastern North American populations, consistently grouped in a single monophyletic clade with many shared mitochondrial sequences among ticks of the two areas. Ticks from the two remaining morphotypes, south-eastern South America and Peruvian, corresponded to two distinct clades. CONCLUSIONS: Given the paucity of morphological characters, the minimal genetic distance separating morphotypes, and more importantly the fact that two morphotypes are genetically indistinguishable, our data suggest that A. maculatum and A. triste should be synonymized and that morphological differences merely reflect very recent local adaptation to distinct environments in taxa that might be undergoing the first steps of speciation but have yet to complete lineage sorting. Nonetheless, future investigations using more sensitive nuclear markers and/or crossbreeding experiments might reveal the occurrence of very rapid speciation events in this group of taxa. Tentative node dating revealed that the A. tigrinum and A. maculatum - A. triste clades split about 2 Mya, while the A. maculatum - A.triste cluster radiated no earlier than 700,000 years ago.

[Amblyomma triste and Amblyomma tigrinum (Acari: Ixodidae) in sympatry in Santa Fe Province, Argentina]. / Amblyomma triste en simpatría con Amblyomma tigrinum (Acari: Ixodidae) en la Provincia de Santa Fe, Argentina.

The aim of this communication is to report, for the first time, the occurrence of Amblyomma triste in Santa Fe province, Argentina, and to add a new isolation place for Amblyomma tigrinum. Both species of ticks are vectors of Rickettsia parkeri, a spotted fever group rickettsia. Ticks were recovered from tourists in August 2014 and December 2015 at the Federico Wildermuth Foundation (31° 59'S, 61° 24'O), San Martin Department, Santa Fe province. Five adult ticks were morphologically identified as A. tigrinum (3 females and 1 male) and A. triste (1 female). This is the first finding including both Amblyomma maculatum group species, A. triste and A. tigrinum, together in the same locality in Argentina. This finding suggests that this site might have favorable features for the development of both species of R. parkeri vector. Further studies including sampling of a larger number of ticks and detection of R. parkeri DNA are needed to better document the epidemiology of this rickettsia in Santa Fe.

Amblyomma triste en simpatría con Amblyomma tigrinum (Acari: Ixodidae) en la provincia de Santa Fe, Argentina / Amblyomma triste and Amblyomma tigrinum (Acari: Ixodidae) in sympatry in Santa Fe Province, Argentina

El objetivo del presente trabajo es comunicar el hallazgo de Amblyomma triste por primera vez en la provincia de Santa Fe, Argentina, y sumar una nueva localidad para Amblyomma tigrinum en la misma provincia. Ambas especies de garrapatas son reconocidos vectores de Rickettsia parkeri, agente etiológico de la fiebre manchada. Los especímenes fueron colectados durante el mes de agosto de 2014 y diciembre de 2015 a partir de turistas en la Fundación Federico Wildermuth (31° 59'S, 61° 24'O), departamento de San Martín, provincia de Santa Fe. Se colectaron 5 garrapatas adultas que fueron identificadas morfológicamente como A. tigrinum (3 hembras y 1 macho) y A. triste (1 hembra). El presente hallazgo de A. triste y A. tigrinum representa el primero en incluir a ambas especies del complejo Amblyomma maculatum en una misma localidad y permite alertar sobre la presencia de vectores de R. parkeri en la zona. Nuevos estudios que incluyan el muestreo de un mayor número de garrapatas y la detección de R. parkeri permitirán dilucidar más aspectos sobre la situación de esta rickettsia en Santa Fe.

The aim of this communication is to report, for the first time, the occurrence of Amblyomma triste in Santa Fe province, Argentina, and to add a new isolation place for Amblyomma tigrinum. Both species of ticks are vectors of Rickettsia parkeri, a spotted fever group rickettsia. Ticks were recovered from tourists in August 2014 and December 2015 at the Federico Wildermuth Foundation (31° 59'S, 61° 24'O), San Martin Department, Santa Fe province. Five adult ticks were morphologically identified as A. tigrinum (3 females and 1 male) and A. triste (1 female). This is the first finding including both Amblyomma maculatum group species, A. triste and A. tigrinum, together in the same locality in Argentina. This finding suggests that this site might have favorable features for the development of both species of R. parkeri vector. Further studies including sampling of a larger number of ticks and detection of R. parkeri DNA are needed to better document the epidemiology of this rickettsia in Santa Fe.

Dynamics of Exposure to Rickettsia parkeri in Cattle in the Paraná River Delta, Argentina.

Several cases of human rickettsiosis caused by Rickettsia parkeri were recently documented in the Paraná River delta of Argentina, where the tick vector is Amblyomma triste Koch. As cattle suffer recurrent A. triste infestations, they are at risk of becoming infected with R. parkeri Herein we investigated the dynamics of R. parkeri and its A. triste vector in a herd of beef cattle. Cattle were followed for 18 mo and samples were analyzed for the presence of antibodies against four Rickettsia species (R. parkeri, Rickettsia bellii, Rickettsia amblyommii, and Rickettsia felis) and also for the presence of rickettsial DNA. Additionally, cattle were examined for attached ticks and questing adult ticks were collected. All ticks were analyzed for the presence of rickettsial DNA. No evidence of rickettsemia was found in any cow, but the high R. parkeri infection rate documented in A. triste both questing in the study area (13.9%) and feeding on cattle (19.8%) and the identification of antibodies against R. parkeri antigen in 90% of cattle are evidence that infection is taking place. Altogether, our data suggest that A. triste ticks are capable of naturally exposing cattle to R. parkeri However, the progress of R. parkeri infection and its impact on bovine health and production remain to be established.

Rickettsial infection in ticks from wild birds from Cerrado and the Pantanal region of Mato Grosso, midwestern Brazil.

The involvement of different species of ticks and wild animals, such as birds, play an important role in the epidemiology of tick-borne diseases. Birds may serve as reservoirs for some tick-borne diseases, and may carry and spread hematophagous ectoparasites mechanically. This study aimed to show the diversity of ticks on birds and molecular detection of rickettsial infection in ticks from Pantanal and Cerrado, two similar Brazilian biomes characterized by hydrological seasons. During two years, August 2012 to May 2014, ticks were collected from birds and from the environment in total of 14 visits for collecting samples, distributed in all hydrological seasons. A total of 674 birds were captured representing 113 species from 26 families. In total, 71 birds were parasitized (10.5%), and 155 ticks of the following 7 tick species (in decreasing order of prevalence) were identified: Amblyomma longirostre Koch, Amblyomma nodosum Neumann, Amblyomma cajennense Fabricius sensu lato (s.l.), Amblyomma calcaratum Neumann, Ornithodoros mimon Kohls, Clifford & Jones, Amblyomma ovale Koch, and Amblyomma triste Koch. Among free-living ticks collected in the environment, A. cajennense s.l. was the most common. This is the first occurrence of O. mimon on birds, and of A. triste on Passeriformes in Brazil. Molecular analyses revealed that 6 A. longirostre ticks were infected by 'Candidatus Rickettsia amblyommii', whereas 1 A. nodosum was infected by a Rickettsia parkeri-like agent, previously reported as Rickettsia sp. strain NOD. Spotted fever group (SFG) agents were, for the first time, reported in ticks from birds captured in Pantanal biome, and the potential involvement of these agents as human pathogens should be considered in further studies.

Seroepidemiological survey of Rickettsia spp. in dogs from the endemic area of Rickettsia parkeri rickettsiosis in Uruguay.

Rickettsia parkeri rickettsiosis is a vector-borne zoonosis that occurs in some countries of the American continent. Following the first description and determination of the pathogenicity to humans in 2004 in USA, this bacterium has been reported in several South American countries. Human cases have been diagnosed in both Uruguay and Argentina in the past years. This study consisted in a serosurvey of 1000 domestic dogs living in the endemic area of rickettsiosis in Uruguay, where Amblyomma triste is the tick vector. Sera were analyzed by Indirect Immunofluorescence Assay (IFA), against antigens of three different rickettsial species: R. rhipicephali, R. felis and R. parkeri. It was determined that 20.3% of the dogs had antibodies that reacted to at least one of the three species tested, taking as cut off ≥64 titers. Furthermore, 140 of the seropositive dogs (14%) had a titer at least 4 times higher to R. parkeri than those of any of the other species, thus, it was considered that the immune response was stimulated by that species in particular. This is the first serological survey in primary hosts for adults of A. triste in Uruguay, and therefore the first prevalence values are reported. Adult A. triste ticks collected from the environment as well as from dogs were analyzed by PCR in order to confirm the current circulation of the agent in the area. In this matter, two out of 28 ticks from dogs, and 3 out of 53 ticks from the environment were positive, and the corresponding sequence analysis revealed 100% similarity with R. parkeri strain maculatum.

Rickettsia parkeri infecting free-living Amblyomma triste ticks in the Brazilian Pantanal.

The present study evaluated the infection of rickettsiae in 151 Rhipicephalus sanguineus, 59 Amblyomma ovale, 166 Amblyomma triste, one Amblyomma dissimile and four Amblyomma dubitatum ticks collected in the municipality of Poconé, State of Mato Grosso, within the Pantanal biome of Brazil. Ticks were individually processed by the hemolymph test with Gimenez staining, isolation of rickettsia in Vero cell culture by the shell vial technique, and polymerase chain reaction (PCR) targeting the citrate synthase rickettsial gene. Through the shell vial technique, rickettsiae were successfully isolated and established in Vero cell culture from one free-living A. triste female tick, which previously showed to contain Rickettsia-like organisms by the hemolymph test. Molecular characterization of the rickettsial isolate was achieved through DNA partial sequences of three rickettsial genes (gltA, ompA, ompB), which showed to be all 100% identical to Rickettsia parkeri. After testing all ticks by PCR, the frequency of R. parkeri infection was 7.23% (12/166) in A. triste adult ticks. The remaining ticks were negative by PCR. This is the first report of in vitro isolation of R. parkeri in the Pantanal biome, confirming the occurrence of this emerging rickettsial pathogen in this natural area of South America.

Morpho-histochemical characterization of the salivary glands of semi-engorged Amblyomma triste (Koch, 1844) (Acari: Ixodidae) female ticks.

This study presents the morphological and physiological characterization of the salivary glands of semi-engorged Amblyomma triste females. Unfed individuals were placed on New Zealand White rabbits for feeding and the females, after 4 days, were collected, dissected and the salivary glands were submitted to the application of histological (hematoxylin-eosin technique) and histochemical tests for the detection of protein (bromophenol blue technique, polysaccharides (periodic acid-Schiff technique), lipid (Nile blue technique) and calcium (von Kossa technique). The histological results show that the glandular tissue is composed by a system of ducts and three types of acini (I, II and III). The acini I are formed by a large central cell surrounded by several smaller agranular peripheral cells. Acini II are formed by cells a, c1, c2, c3 and c5, which are full of secretion granules. Acini III are constituted by cells d, e and f; the former two contain secretion granules, the latter is agranular. The glandular histochemical composition was also verified. Data obtained here will certainly help in the understanding of the cellular morphology and of the general physiology of these organs in this specie, providing important information for the creation of scientific bases which will contribute for the development of more specific and efficient methods of control.

In vitro isolation and infection intensity of Rickettsia parkeri in Amblyomma triste ticks from the Paraná River Delta region, Argentina.

In the present study, we report the first in vitro isolation and infection intensity of Rickettsia parkeri in Amblyomma triste ticks from Argentina. No genetic differences in the molecular targets evaluated were found between R. parkeri isolates from Argentina and those R. parkeri isolates reported in Uruguay and Brazil, both obtained from A. triste. Only a minor difference was observed when compared to R. parkeri isolated from Amblyomma maculatum from United States. Moreover, the prevalence of infection by R. parkeri in ticks collected from the vegetation in the Paraná Delta was high (20.4%). Interestingly, the distribution of R. parkeri infection intensity observed in A. triste ticks was distinctly bimodal, with approximately 60% of the infected ticks presenting high rickettsial loads (3.8×10(5)-4.5×10(7) ompA copies/tick) and the remainder with low rickettsial levels (5.6×10(1)-6.5×10(3) ompA copies/tick). This bimodality in R. parkeri infection intensity in ticks could determine differences in the severity of the disease, but also be important for the infection dynamics of this pathogen. Further research exploring the distribution of rickettsial infection levels in ticks, as well as its determinants and implications, is warranted.

Distribution and genetic variation of Amblyomma triste (Acari: Ixodidae) in Argentina.

A study was conducted to investigate the distribution of Amblyomma triste in Argentina under the hypothesis that this tick prevails in riparian localities along the Paraná River and adjacent humid environments from 34° 30' S to 25° 20' S, approximately. Ticks were collected from mammals and vegetation in those environments from November 2008 to October 2012. Additionally, genetic variation was tested from Argentinean, Brazilian, Chilean, and Uruguayan populations of A. triste by comparing sequences of 16S rDNA mitochondrial gene. The hypothesis was not confirmed because A. triste were collected at 36° 16' S, well beyond the southern limit predicted, and the distribution along the banks of the Paraná River was not continuous. The northernmost population of A. triste within Argentina was found at 25° 42' S. Still undetermined abiotic factors and plant communities may play a role in modulating the abundance of A. triste because host availability does not appear to be a restriction factor. The genetic variation among A. triste populations from Argentina, Brazil, and Uruguay indicates that they belong to a unique taxon that is considered bona fide A. triste (type locality Montevideo, Uruguay) while it is unclear if the Chilean population of A. triste is conspecific with the other populations investigated in this study. It would be of importance to compare those genetically homogeneous populations with other populations of alleged A. triste, especially populations established in the Nearctic Zoogeographic Region in Mexico and USA.

Molecular identification of Rickettsia parkeri infecting Amblyomma triste ticks in an area of Argentina where cases of rickettsiosis were diagnosed

Specimens of the hard tick Amblyomma triste were found infected with Rickettsia parkeri in an area of Argentina (General Lavalle, Buenos Aires Province) where cases of human illness attributed to this microorganism have been reported. Molecular detection of R. parkeri was based on polymerase chain reactions that amplify a ca. 400-bp fragment of the 23S-5S intergenic spacer and a ca. 500-bp fragment of the gene encoding a 190-kDa outer membrane protein. Three (6.97%) of 43 A. triste ticks were determined to be positive for R. parkeri. These results provide strong evidence that A. triste is the vector of R. parkeri in the study area. The findings of this work have epidemiological relevance because human parasitism by A. triste ticks has been frequently recorded in some riparian areas of Argentina and Uruguay and new cases of R. parkeri rickettsiosis might arise in the South American localities where humans are exposed to the bites of this tick species.

Rickettsia parkeri: a Rickettsial pathogen transmitted by ticks in endemic areas for spotted fever rickettsiosis in southern Uruguay / Rickettsia parkeri: patógeno rickettsial transmitido por garrapatas en áreas endémicas de rickettsiosis por fiebre manchada en el sur de Uruguay

At first Rickettsia conorii was implicated as the causative agent of spotted fever in Uruguay diagnosed by serological assays. Later Rickettsia parkeri was detected in human-biting Amblyomma triste ticks using molecular tests. The natural vector of R. conorii, Rhipicephalus sanguineus, has not been studied for the presence of rickettsial organisms in Uruguay. To address this question, 180 R. sanguineus from dogs and 245 A. triste from vegetation (flagging) collected in three endemic localities were screened for spotted fever group (SFG) rickettsiosis in southern Uruguay. Tick extracted DNA pools were subjected to PCR using primers which amplify a fragment of the rickettsial gltA gene. Positive tick DNA pools with these primers were subjected to a second PCR round with primers targeting a fragment of the ompA gene, which is only present in SFG rickettsiae. No rickettsial DNA was detected in R. sanguineus. However, DNA pools of A. triste were found to be positive for a rickettsial organism in two of the three localities, with prevalences of 11.8% to 37.5% positive pools. DNA sequences generated from these PCR-positive ticks corresponded to R. parkeri. These findings, joint with the aggressiveness shown by A. triste towards humans, support previous data on the involvement of A. triste as vector of human infections caused by R. parkeri in Uruguay.

Inicialmente, Rickettsia conorii fue señalada como el agente causal de la fiebre manchada en Uruguay, diagnosticada mediante pruebas serológicas. Posteriormente, Rickettsia parkeri fue detectada mediante técnicas moleculares en garrapatas Amblyomma triste colectadas sobre humanos. El vector natural de R. conorii, Rhipicephalus sanguineus, no ha sido estudiado en cuanto a rickettsias en Uruguay. Para abordar este tema, 180 R. sanguineus fueron colectados sobre perros y 245 A. triste sobre vegetación en tres localidades consideradas endémicas para fiebres manchadas en el sur de Uruguay. El ADN de las garrapatas fue extraído en pools y sometido a una primera PCR utilizando cebadores que amplifican un fragmento del gen gltA, presente en prácticamente todas las especies de Rickettsia. Las muestras positivas fueron sometidas a una segunda PCR con cebadores que amplifican un fragmento del gen ompA, presente sólo en rickettsias del grupo de las fiebres manchadas (GFM). No se detectó ADN rickettsial en R. sanguineus. Sin embargo, muestras de A. triste fueron positivas a rickettsiales en dos de las tres localidades estudiadas, con prevalencias de pools positivos del 11.8 y 37.5% respectivamente. La secuenciación del ADN evidenció la presencia de R. parkeri. Basados en estos resultados junto a los anteriores y la agresividad de A. triste hacia los humanos, se concluye que esta garrapata es vector de rickettsiosis humana por R. parkeri en Uruguay.

Avaliação da infecção por Rickettsia spp. em Amblyomma triste Koch (Acari: Ixodidae) e em algumas espécies de Ornithonyssus Sambon (Acari: Macronyssidae) / Evaluation of Rickettsial infection in Amblyomma triste Koch (Acari: Ixodidae) and in some species Ornithonyssus spp. Sambon (Acari: Macronyssidae)

O gênero Rickettsia compreende bactérias intracelulares obrigatórias e há por enquanto 22 espécies que, comprovadamente, são patogênicas ao homem. A transmissão da maioria das espécies de riquétsias está associada a carrapatos, mas também podem ser veiculadas por pulgas, piolhos e ácaros. O presente estudo teve por objetivos avaliar a infecção de Rickettsia parkeri em carrapatos da espécie Amblyomma triste (Acari: Ixodidae) e também avaliar a infecção de Rickettsia spp. em algumas espécies de Ornithonyssus Sambon (Acari: Macronyssidae). Foram obtidas fêmeas de A. triste de um cervo-do-pantanal (Blastocerus dichotomus) atropelado e as posturas testadas por PCR para o estabelecimento de uma colônia naturalmente infectada com R. parkeri (grupo infectado) e outra livre de infecção (grupo controle). Para avaliar a infecção de Rickettsia spp. em ácaros foram realizadas 15 campanhas de capturas de pequenos mamíferos terrestres nos estados de São Paulo e Paraná. Após anestesisa e escovação, os ácaros foram removidos dos hospedeiros e mantidos em nitrogênio líquido para a tentativa de isolamento através da técnica de shell vial. Foram estudadas quatro gerações de A. triste infectada e não infectada com R. parkeri. Os resultados revelaram que R. parkeri é moderadamente patogênica para A. triste e a fase do ciclo biológico do carrapato mais sucetível ao efeito deletério da bactéria é o estágio ninfal. Foram capturados 165 mamíferos silvestres das seguintes espécies: Akodon cursor, Akodon montensis, Didephis aurita, Euryzoryzomys russatus, Metachirus nudicaudatus, Monodelphis sp., Nectomys squamipes, Oecomys sp., Oligoryzomys sp, Oxymycterus sp., Sciurus aestuans and Thaptomys nigrita. Destes, somente 13 estavam infestados com três espécies de Ornithonyssus spp. Foi obtido um isolado de O. vitzthumi que parasitavam Oxymycterus sp., contudo não foi possível sua caracterização, pela não amplificação pelos marcadores clássicos para o gênero Rickettsia.

The genus Rickettsia comprises obligate intracellular bacteria and there are so far 22 species that are proven to be pathogenic to humans. The transmission of most species of rickettsiae is associated with ticks, but also can be transmitted by fleas, lice and mites. The present study aimed to evaluate the infection of Rickettsia parkeri in Amblyomma triste. (Acari: Ixodidae) and also to evaluate the infection of Rickettsia spp. in some species of Ornithonyssus spp. Sambon (Acari: Macronyssidae). A. triste females were obtained from a marsh deer (Blastocerus dichotomus). Through PCR on their offspring, it was established of a colony naturally infected with R. parkeri (infected group) and another colony uninfected (control group). To assess the infection of the Rickettsia spp. in mites, 15 capture campaigns of small terrestrial mammals were performed in the states of São Paulo and Paraná. After anesthesia and brushing, the mites were removed from hosts and kept in liquid nitrogen for isolation of rickettsiae using the shell vial technique. Four consecutive generations of A. triste were studied in the laboratory. The results showed that R. parkeri is moderately pathogenic to A. triste, especially to the nymphal stage. A total of 165 wild small mammals of the following species were captured: Akodon cursor, Akodon montensis, Didephis aurita, Euryzoryzomys russatus, Metachirus nudicaudatus, Monodelphis sp., Nectomys squamipes, Oecomys sp., Oligoryzomys sp, Oxymycterus sp., Sciurus aestuans and Thaptomys nigrita. Of these, only 13 were infested with three species of Ornithonyssus spp. A bacterial isolate was obtained from mites removed from a Oxymycterus sp. However, it was not possible the molecular characterization by classical markers for the genus Rickettsia.

Especies de Amblyomma (acari: ixodidae) parasitando perros (canis familiaris) en áreas rurales de los estados Lara, Yaracuy, Carabobo y Falcón Venezuela / Species of Amblyomma (acari: ixodidae) parasitizing dogs (canis familiaris) from rural areas of Lara, Yaracuy, Carabobo y Falcón Venezuela

Un total de 50 caninos de áreas rurales de los estados Lara, Yaracuy, Carabobo y Falcón, Venezuela, fueron examinados visualmente y mediante palpación cutánea con el fin de detectar la presencia de garrapatas. Ninguno de los animales se encontró parasitado por Rhipicephalus sanguineus, la garrapata común del perro. Se colectaron 139 especimenes adultos del género Amblyomma Koch, 1844: 72 hembras y 65 machos de la especie Amblyomma ovale Koch, 1844, y dos hembras de la especie Amblyomma triste Koch, 1844. La identificación de los especimenes se realizó mediante observación en lupa estereoscópica y con la ayuda de claves taxonómicas. Los Estados donde se colectó el mayor número de ixódidos fueron Falcón con 52 especimenes y Lara con 49, representando 38 y 36%, respectivamente. A. ovale ha sido reportada como vector natural de Hepatozoon canis en áreas rurales. La especie A. triste fue colectada sólo en un canino del estado Yaracuy. Esta especie ha sido incriminada como el vector biológico de varios agentes rickettsiales patógenos, tanto para humanos como para animales domésticos y salvajes, por lo que se resalta la importancia del género Amblyomma en la transmisión de enfermedades zoonóticas.

Fifty dogs from the rural areas of Lara, Yaracuy, Carabobo and Falcón States of Venezuela were sampled through the visual and touch techniques in search of the presence of ticks. All the dogs were free of the brown dog tick Rhipicephalus sanguineus. A total of 139 adult ticks of the genus Amblyomma Koch, 1844 were collected: of them, 65 males and 72 females were identified as Amblyomma ovale Koch, 1844, whereas two females belonged to the species Amblyomma triste Koch, 1844. The observation through stereomicroscope, as well as the use of taxonomic keys, were employed in the identification of the collected specimens. Most of the ticks were collected in Falcón and Lara States, totalling 52 (38%) and 49 (36%), respectively. The species A. ovale has been reported as a natural vector of the protozoan Hepatozoon canis in rural areas. A. triste was collected only in one dog in Yaracuy State. This species has been incriminated as a biological vector of several rickettsial agents to the men and animals. The actual role of the genus Amblyomma as vector of zoonotic disease agents is highlighted.

Ocorrência de ixodidae parasitos de capivara (Hydrochoerus hydrochaeris linnaeus, 1766) na estação ecológica do Taim, Rio Grande - RS, Brasil / Occurence of ixodidae parasites of capybara (Hydrochoeurus hydrochaeris linnaeus, 1766) in the ecologic area of Taim, Rio Grande - RS, Brazil

O objetivo deste trabalho foi identificar as espécies de carrapatos observadas sobre capivaras na Estação Ecológica do Taim, Rio Grande- RS, Brasil. Foram examinadas 27 capivaras encontradas mortas por atropelamento na BR 471, em seu trecho que corta a Estação, sendo cole lados 497 carrapatos das espécies Amblyomma cooperi (=A. lutzi; = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum e ninfas do gênero Amblyomma. A. cooperi representou 68,41 por cento dos carrapatos identificados, com uma freqüência de parasitismo de 92,60 por cento dos hospedeiros, enquanto A. triste representou 24,75 por cento dos carrapatos em 44,43 por cento dos hospedeiros e A. tigrinum foi coletado em 14,81 por cento dos hospedeiros, totalizando 1,21 por cento dos carrapatos. As ninfas de Amblyomma sp. foram cotetadas em 18,51 por cento dos hospedeiros apresentando um percentual de 5,63 por cento do total de carrapatos. A relação macho : fêmea apresentou valores de 2,3 : 1 e 2 : l para o A. cooperi e A. triste, respectivamente. Todos hospedeiros apresentavam-se parasitados, com uma média de 18,4 carrapatos, variando de 1 a 64 carrapatos coletados por hospedeiro.

The aim of this article was the identification ofthe tick species observed on capybara in wildlife in the Ecologic Area of Taim, Rio Grande - RS; Brazil. Twenly seven capybaras found dead by trample in the road BR 471 in the Ecologic Area, wereexamined ticks coilected of the species Amblyomma cooperi (= A. lutzi and = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum and ninphs of the Genus Amblyomma. Amblyomma cooperi represented 68.41 percent of the ticks with a frequency of parasitism of 92.60 percent of the hosts; Amblyomma triste species represented 24.75 percent of the collected ticks m 44.43 percent of the hosts; Amblyomma tigrinum species were coilected m 14.81 percent of the hosts from a total of 1.21 percent of the found ticks and, the nimphs of Amblyomma were coilected in 18.51 percent of the hosts per forming 5.63 percent of the ali ticks coilected. The relation mate .female showed values of 2.3:1 and 2:1 to A. cooperiand and A. triste, respectivety. All examined hosts were found wiih ticks, with a mean of 18.4 ticks per host.

Ocorrência de ixodidae parasitos de capivara (Hydrochoerus hydrochaeris linnaeus, 1766) na estação ecológica do Taim, Rio Grande - RS, Brasil

The aim of this article was the identification ofthe tick species observed on capybara in wildlife in the Ecologic Area of Taim, Rio Grande - RS; Brazil. Twenly seven capybaras found dead by trample in the road BR 471 in the Ecologic Area, wereexamined ticks coilected of the species Amblyomma cooperi (= A. lutzi and = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum and ninphs of the Genus Amblyomma. Amblyomma cooperi represented 68.41% of the ticks with a frequency of parasitism of 92.60% of the hosts; Amblyomma triste species represented 24.75% of the collected ticks m 44.43% of the hosts; Amblyomma tigrinum species were coilected m 14.81% of the hosts from a total of 1.21% of the found ticks and, the nimphs of Amblyomma were coilected in 18.51% of the hosts per forming 5.63% of the ali ticks coilected. The relation mate .female showed values of 2.3:1 and 2:1 to A. cooperiand and A. triste, respectivety. All examined hosts were found wiih ticks, with a mean of 18.4 ticks per host.

O objetivo deste trabalho foi identificar as espécies de carrapatos observadas sobre capivaras na Estação Ecológica do Taim, Rio Grande- RS, Brasil. Foram examinadas 27 capivaras encontradas mortas por atropelamento na BR 471, em seu trecho que corta a Estação, sendo cole lados 497 carrapatos das espécies Amblyomma cooperi (=A. lutzi; = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum e ninfas do gênero Amblyomma. A. cooperi representou 68,41% dos carrapatos identificados, com uma freqüência de parasitismo de 92,60% dos hospedeiros, enquanto A. triste representou 24,75% dos carrapatos em 44,43% dos hospedeiros e A. tigrinum foi coletado em 14,81% dos hospedeiros, totalizando 1,21% dos carrapatos. As ninfas de Amblyomma sp. foram cotetadas em 18,51% dos hospedeiros apresentando um percentual de 5,63% do total de carrapatos. A relação macho : fêmea apresentou valores de 2,3 : 1 e 2 : l para o A. cooperi e A. triste, respectivamente. Todos hospedeiros apresentavam-se parasitados, com uma média de 18,4 carrapatos, variando de 1 a 64 carrapatos coletados por hospedeiro.

Ocorrência de ixodidae parasitos de capivara (Hydrochoerus hydrochaeris linnaeus, 1766) na estação ecológica do Taim, Rio Grande - RS, Brasil

The aim of this article was the identification ofthe tick species observed on capybara in wildlife in the Ecologic Area of Taim, Rio Grande - RS; Brazil. Twenly seven capybaras found dead by trample in the road BR 471 in the Ecologic Area, wereexamined ticks coilected of the species Amblyomma cooperi (= A. lutzi and = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum and ninphs of the Genus Amblyomma. Amblyomma cooperi represented 68.41% of the ticks with a frequency of parasitism of 92.60% of the hosts; Amblyomma triste species represented 24.75% of the collected ticks m 44.43% of the hosts; Amblyomma tigrinum species were coilected m 14.81% of the hosts from a total of 1.21% of the found ticks and, the nimphs of Amblyomma were coilected in 18.51% of the hosts per forming 5.63% of the ali ticks coilected. The relation mate .female showed values of 2.3:1 and 2:1 to A. cooperiand and A. triste, respectivety. All examined hosts were found wiih ticks, with a mean of 18.4 ticks per host.

O objetivo deste trabalho foi identificar as espécies de carrapatos observadas sobre capivaras na Estação Ecológica do Taim, Rio Grande- RS, Brasil. Foram examinadas 27 capivaras encontradas mortas por atropelamento na BR 471, em seu trecho que corta a Estação, sendo cole lados 497 carrapatos das espécies Amblyomma cooperi (=A. lutzi; = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum e ninfas do gênero Amblyomma. A. cooperi representou 68,41% dos carrapatos identificados, com uma freqüência de parasitismo de 92,60% dos hospedeiros, enquanto A. triste representou 24,75% dos carrapatos em 44,43% dos hospedeiros e A. tigrinum foi coletado em 14,81% dos hospedeiros, totalizando 1,21% dos carrapatos. As ninfas de Amblyomma sp. foram cotetadas em 18,51% dos hospedeiros apresentando um percentual de 5,63% do total de carrapatos. A relação macho : fêmea apresentou valores de 2,3 : 1 e 2 : l para o A. cooperi e A. triste, respectivamente. Todos hospedeiros apresentavam-se parasitados, com uma média de 18,4 carrapatos, variando de 1 a 64 carrapatos coletados por hospedeiro.