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34. Amblyomma dubitatum Neumann, 1899. Neotropical: 1) Argentina, 2) Bolivia, 3) Brazil, 4) Paraguay, 5) Uruguay (Nava et al. 2010 a, Martins et al. 2014, Mastropaolo et al. 2014, Gruhn et al. 2019, Guglielmone et al. 2021). Several records of Amblyomma dubitatum have been published under the name Amblyomma cooperi, as noted by Camicas et al. (1998) and Estrada-Peña et al. (2002). Neumann (1899) described Amblyomma dubitatum from a female tick collected in Spain, but he was not convinced about the origin of this specimen. Amblyomma dubitatum was treated as an African or Oriental species by various authors until Camicas et al. (1998) listed it as a Neotropical species, a view supported by Estrada-Peña et al. (2002), who redescribed this tick, as discussed in Guglielmone et al. (2003)., Published as part of Guglielmone, Alberto A., Nava, Santiago & Robbins, Richard G., 2023, Geographic distribution of the hard ticks (Acari: Ixodida: Ixodidae) of the world by countries and territories, pp. 1-274 in Zootaxa 5251 (1) on page 45, DOI: 10.11646/zootaxa.5251.1.1, http://zenodo.org/record/7704190, {"references":["Neumann, L. G. (1899) Revision de la famille des ixodides (3 e memoire). Memoires de la Societe Zoologique de France, 12, 107 - 294.","Nava, S., Venzal, J. M., Labruna, M. B., Mastropaolo, M., Gonzalez, E. M., Mangold, A. J. & Guglielmone, A. A. (2010 a) Hosts, distribution and genetic divergence (16 S rDNA) of Amblyomma dubitatum (Acari: Ixodidae). Experimental and Applied Acarology, 51, 335 - 351. https: // doi. org / 10.1007 / s 10493 - 009 - 9331 - 6","Guglielmone, A. A., Robbins, R. G., Apanaskevich, D. A., Petney, T. N., Estrada-Pena, A. & Horak, I. G. (2014) The hard ticks of the world (Acari: Ixodida: Ixodidae). Springer, Dordrecht, Heidelberg, New York, London, 738 pp. https: // doi. org / 10.1007 / 978 - 94 - 007 - 7497 - 1","Mastropaolo, M., Beltran-Saavedra, L. F. & Guglielmone A. A. (2014) The ticks (Acari: Ixodida: Argasidae, Ixodidae) of Bolivia. Ticks and Tick-borne Diseases, 2014, 5, 186 - 194. https: // doi. org / 10.1016 / j. ttbdis. 2013.10.005","Gruhn, K. D., Ogrzewalska, M., Rozental, T., Farikoski, I. O., Blanco, C., Freitas, L. S., Lemos, E. R. S. & Ribeiro, V. M. F. (2019) Evaluation of rickettsial infection in free-range capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766 [sic]) (Rodentia: Caviidae) and ticks (Acari: Ixodidae) in the Western Amazon, Brazil. Ticks and Tick-borne Diseases, 10, 961 - 966. https: // doi. org / 10.1016 / j. ttbdis. 2019.04.007","Guglielmone, A. A., Nava, S. & Robbins, R. G. (2021) Neotropical hard ticks (Acari: Ixodida: Ixodidae). A critical analysis of their taxonomy, distribution, and host relationships. Springer Nature Switzerland AG, Cham, 486 pp. https: // doi. org / 10.1007 / 978 - 3 - 030 - 72353 - 8","Camicas, J. L., Hervy, J. P., Adam, F. & Morel, P. C. (1998) Les tiques du monde. Nomenclature, stades decrits, hotes, repartition (Acarida, Ixodida). Orstom, Paris, 233 pp.","Estrada-Pena, A., Venzal, J. M. & Guglielmone, A. A. (2002) Amblyomma dubitatum Neumann: description of nymph and redescription of adults, together with the description of the immature stages of A. triste Koch. Acarologia, 42, 323 - 333.","Guglielmone, A. A., Estrada-Pena, A., Keirans J. E. & Robbins, R. G. (2003) Ticks (Acari: Ixodida) of the Neotropical Zoogeographic Region. Special Publication of the Integrated Consortium on Ticks and Tick-Borne Diseases- 2, Atalanta, Houten, The Netherlands, 173 pp."]}

Rickettsia rickettsii infection causes the highest human fatality rate among all Rickettsia species of the world and is endemic in Southeast Brazil. In this part of the country most human spotted fever cases are related to unnaturally high populations of ticks, usually a mix of two species, Amblyomma dubitatum Neumann and Amblyomma sculptum Berlese and their local host, capybara (Hydrochoerus hydrochaeris). At the same time, an increase in the number of SF notifications as well as its urbanization was observed, and a better characterization of disease epidemiology is mandatory for control measures and to halt its expansion. It was recently noticed in southeast Brazil that SF endemic areas were characterized by overgrowth populations of A. sculptum and decreased populations of A. dubitatum. Hence, characterization of areas with potential to endemicity, eco-epidemiological studies and control measures may rely on the evaluation of A. sculptum/A. dubitatum rate. However, in potentially endemic scenarios, discriminating the two tick species, particularly the nymphs considered the main vector stage, is a challenge in face of several hundreds to thousands of ticks that should be examined for quantitative studies. We herein present additional morphological features to an existing identification key for Amblyomma nymphs that considerably diminishes the labor to distinguish nymphs of these two tick species. Specifically, the oval-shaped scutum of A. dubitatum and a conspicuous scapula of A. sculptum are prominent discriminating features.

Spotted fever is an acute febrile illness, which is considered severely underreported and misdiagnosed in the Brazilian Pampa, caused by tick-borne Rickettsiae. Here, we report an eco-epidemiological investigation of Rickettsia spp. in ticks from a spotted fever focus in Toropi, southern Brazil. Ticks were collected from capybara carcasses and processed individually to obtain genomic DNA. Rickettsia was investigated using PCR that amplified the rickettsial fragments of the gltA, ompA and htrA genes. DNA from Rickettsia parkeri was found in four of 14 Amblyomma dubitatum ticks collected from capybara carcasses in Toropi and the nearby municipality of Quevedos. We also tested 210A. dubitatum ticks obtained from road-killed capybaras of other localities from the Pampa biome; none of them were positive for Rickettsiae. Thus, in Rio Grande do Sul, two Rickettsia species can be potentially associated to spotted fever: Rickettsia sp. strain Atlantic Rainforest, associated with Amblyomma ovale ticks in the Atlantic Rainforest biome, and R. parkeri, associated both with Amblyomma tigrinum and A. dubitatum ticks in the Pampa biome. Our results reinforce that R. parkeri may be the agent associated with spotted fever in the Brazilian Pampa.

Brazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii, is transmitted to humans mainly by the tick Amblyomma sculptum in southeastern Brazil. In most BSF-endemic areas A. sculptum populations are sustained chiefly by capybaras (Hydrochoerus hydrochaeris), which are also the host of another tick species, Amblyomma dubitatum, not implicated in R. rickettsii transmission. Herein, we evaluated the effects of relative humidity (RH), temperature, and water immersion on the successful development of the engorged stages of A. dubitatum and compared them with recently published data under the same experimental conditions for A. sculptum. We showed that free-living developmental stages (engorged larvae, nymphs and females, and eggs) of A. dubitatum had higher survival rates when these stages were submerged in water for different periods of times (24–72 h). On the other hand, higher survival rates were observed for A. sculptum when ticks were incubated at lower RH values, 65 or 78 %, regardless of summer or winter mean temperatures. These results suggest that A. dubitatum is more adapted to humid habitats and seasonally flooding soils than A. sculptum, whereas this latter species should be more adapted than A. dubitatum to drier habitats. The implications of these results for the spatial distribution of A. dubitatum and A. sculptum, in relation to BSF epidemiology, are discussed.

Rickettsia infection of each tick was evaluated by the hemolymph test and polymerase chain reaction (PCR) targeting gltA and ompA genes. All hemolymph tests were negative and PCR of one A. dubitatum detected both Rickettsia genes. Sequence of ompA exhibited a 99% identity with Rickettsia parkeri and R. africae and a 98% identity with R. sibirica. Rickettsia of the spotted fever group in A. dubitatum is described for the first time in an urban area within the municipality of Campo Grande in the state of Mato Grosso do Sul (MS), Brazil. This finding reinforces the importance of more detailed studies to determine the role of A. dubitatum in the transmission of spotted fever agents.

Brazilian spotted fever (BSF) is a potentially lethal human disease caused by Rickettsia rickettsii transmitted by ticks, including Amblyomma sculptum. However, in Southeast Brazil, where most BSF cases occur, capybaras are key hosts for both A. sculptum and Amblyomma dubitatum. We therefore compared the risk of human exposure to these ticks at a non-endemic anthropogenic site in Southeast Brazil where both tick species are maintained by capybaras and occur at high abundance. Cloth dragging, human baits and CO2 traps were used to assess tick abundance and risk for human exposure. The two tick species displayed profound differences in behavior and microhabitat use. Notably, A. sculptum but not A. dubitatum quested for hosts openly from vegetation (ambush behavior) and infested human baits. Furthermore, A. dubitatum was more aggregated at a specific site whereas A. sculptum was more widespread along differing and drier microhabitats. Adults and nymphs of both species were infected with Rickettsia bellii. Overall, the results indicate that even though both species co-existed in the same area, A. sculptum posed a greater risk for biting humans and thus also for transmitting tick-borne pathogens.

The genus Amblyomma is the most representative tick genus in Brazil and some species act as vectors of pathogenic organisms to animals and humans. Information on the seasonal dynamics of Amblyomma spp. as well as on rickettsial organisms infecting these ticks in some regions in Brazil is still fragmentary. Herein, we investigated the seasonal dynamics and rickettsial infections in Amblyomma dubitatum ticks collected in the Atlantic forest biome in north-eastern Brazil. Using carbon dioxide traps, ticks were collected monthly for two consecutive years. In total, 15,789 ticks were collected: 69 females (0.4%), 116 males (0.7%), 1,067 nymphs (6.8%), and 14,537 larvae (92.1%). All nymphs, females and males were identified as A. dubitatum, whereas larvae were identified as Amblyomma spp. Larvae were more frequent in summer (77% of the larvae collected), whereas nymphs were collected with similar frequency in summer (32.8%), autumn (30.0%) and spring (28.4%). Adults were more frequent in spring (47.6%). A total of 648 ticks (485 nymphs, 60 females, and 103 males) were tested by PCR for the gltA gene of Rickettsia spp. and 87 (13.4%; 95% CI: 10.9–16.3%) were positive. A consensus sequence (size, 350 bp) of 66 gltA gene sequences indicate that the organism detected herein is similar to Rickettsia tamurae, Rickettsia monacencis and Rickettsia sp. strain Pampulha. One of these positive samples was also positive for the ompA gene of spotted fever group rickettsiae, but attempts to sequence the amplicon were not successful. We also tested this sample by a PCR targeting the rickettsial htrA gene, but no amplification product could be detected. This study indicates that A. dubitatum may be a common tick in areas where capybaras are present in north-eastern Brazil, occurring during the whole year. It also suggests the circulation of a spotted fever group rickettsia in this A. dubitatum population, whose identity has yet to be determined.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior UFU - Universidade Federal de Uberlândia A febre maculosa brasileira (FMB), doença com elevada letalidade causada pela bactéria Rickettsia rickettsii, tem no Brasil dois cenários ecológicos reconhecidos. Perceber estes cenários é deveras relevante, pois são o principal e até o único indício de que uma doença febril possa ser a FMB. Ademais, devido ao curso hiperagudo da doença o tratamento deve ser iniciado antes da confirmação laboratorial do agente da infecção. O cenário responsável pela maioria dos casos encontra-se no Sudeste e se caracteriza pela presença de grandes populações de capivaras e intensa infestação ambiental por carrapatos. Porém a presença das capivaras e carrapatos não se traduz automaticamente em transmissão da R. rickettsii para seres humanos e muitas dúvidas cercam a epidemiologia da doença. Um aspecto nebuloso da epidemiologia é a participação de duas espécies de carrapato e a influência de outras espécies de riquetsias sobre a transmissão do agente da FMB para humanos. Invariavelmente o carrapato Amblyomma sculptum é considerado o vetor, particularmente no estágio de ninfa. Porém, na maioria das situações, o carrapato transmissor do patógeno não é recuperado. Por outro lado, em áreas com capivaras a infestação ambiental se dá tanto pelo A. sculptum como também pelo carrapato Amblyomma dubitatum sendo que experimentalmente ambos são capazes de transmitir a R. rickettsii. Entender a relação existente entre as duas espécies de carrapatos com as riquetsias e os riscos a que as pessoas estão expostas é de grande importância para que medidas preventivas possam ser tomadas. Neste trabalho foram investigados diversos aspectos da eco-epidemiologia da FMB em dez pontos com predisposição para a riquetsiose e distribuídos pelo município de Uberlândia, Minas Gerais, Brasil. Brazilian spotted fever (BSF), a disease with high lethality caused by the bacterium Rickettsia rickettsii, has two recognized ecological scenarios in Brazil. Understanding these scenarios is very relevant, as they are the main and even the only indication that a febrile illness may be BSF. In addition, due to the hyperacute course of the disease, treatment must be started before laboratory confirmation of the disease. The scenario responsible for most cases is found in the Southeast and is characterized by the presence of large populations of capybaras and intense environmental infestation by ticks. However, the presence of capybaras and ticks does not automatically indicate transmission of R. rickettsii to humans and many doubts surround the epidemiology of the disease. An important but still ill-known aspect of epidemiology is the participation of two species of tick and the influence of other species of Rickettsia on the transmission of the BSF agent to humans. Invariably the tick Amblyomma sculptum is considered the vector, particularly in the nymphal stage. However, in most situations, the tick that transmits the pathogen is not recovered. On the other hand, in areas with capybaras, the environmental infestation occurs both by A. sculptum and Amblyomma dubitatum, and experimentally both are capable of transmitting R. rickettsii. Understanding the relationship between the two species of ticks with rickettsiae and the risks to which people are exposed is of great importance so that preventive measures can be taken. In this work, several aspects of BSF eco-epidemiology were investigated at ten locations with a predisposition for rickettsial disease and distributed throughout the city of Uberlândia, Minas Gerais, Brazil. Dissertação (Mestrado) 2022-03-25

Rickettsia parkei is the etiological agent of spotted fever in Uruguay, where is transmitted to humans by the tick Amblyomma triste. In the present study, ticks were collected from capybaras (Hydrochoerus hydrochaeris) and domestic dogs during 2011-2012 in different parts of Uruguay. Three out of 11 (27.3%) Amblyomma dubitatum ticks collected from capybaras, and 4 out of 6 (66.7%) Amblyomma tigrinum ticks collected from dogs were shown by molecular analyses to be infected by Rickettsia parkeri strain Maculatum 20. Until the present work, A. triste was the only tick species that was found infected by R. parkeri in Uruguay. This is the first report of R. parkeri infecting these two tick species in Uruguay, expanding the current distribution of this rickettsial pathogen in the country.

We supply information about hosts and distribution of Amblyomma dubitatum. In addition, we carry out an analysis of genetic divergence among specimens of A. dubitatum from different localities and with respect to other Neotropical Amblyomma species, using sequences of 16S rDNA gene. Although specimens of A. dubitatum were collected on several mammal species as cattle, horse, Tapirus terrestris, Mazama gouazoubira, Tayassu pecari, Sus scrofa, Cerdocyon thous, Myocastor coypus, Allouata caraya, Glossophaga soricina and man, most records of immature and adult stages of A. dubitatum were made on Hydrochoerus hydrochaeris, making this rodent the principal host for all parasitic stages of this ticks. Cricetidae rodents (Lundomys molitor, Scapteromys tumidus), opossums (Didelphis albiventris) and vizcacha (Lagostomus maximus) also were recorded as hosts for immature stages. All findings of A. dubitatum correspond to localities of Argentina, Brazil, Paraguay and Uruguay, and they were concentrated in the Biogeographical provinces of Pampa, Chaco, Cerrado, Brazilian Atlantic Forest, Parana Forest and Araucaria angustifolia Forest. The distribution of A. dubitatum is narrower than that of its principal host, therefore environmental variables rather than hosts determine the distributional ranges of this tick. The intraspecific genetic divergence among 16S rDNA sequences of A. dubitatum ticks collected in different localities from Argentina, Brazil and Uruguay was in all cases lower than 0.8%, whereas the differences with the remaining Amblyomma species included in the analysis were always bigger than 6.8%. Thus, the taxonomic status of A. dubitatum along its distribution appears to be certain at the specific level. Fil: Nava, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; Argentina Fil: Venzal, José M.. Universidad de la Republica, Salto; Uruguay Fil: Labruna, Marcelo B.. Universidade de Sao Paulo; Brasil Fil: Mastropaolo, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; Argentina Fil: González, Enrique M.. Museo Nacional de Historia Natural Uruguay; Uruguay Fil: Mangold, Atilio Jose. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; Argentina Fil: Guglielmone, Alberto Alejandro. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

En octubre de 2015, una ninfa de garrapata fue colectada sobre un ejemplar macho de Procyon cancrivorus hallado muerto a la vera de la Ruta Nacional 119 en las cercanías de la ciudad de Mercedes, provincia de Corrientes, Argentina. La ninfa colectada fue identificada morfológica y molecularmente como Amblyomma dubitatum, y la misma se encontró infectada con la alfaproteobacteria Rickettsia bellii. Este reporte constituye el primer registro de la asociación A. dubitatum P. cancrivorus In October 2015, a tick nymph was collected from a male Procyon cancrivorus found dead at the roadside of the National Road 119 near Mercedes city, Corrientes province, Argentina. The nymph collected was morphologically and molecularly identified as Amblyomma dubitatum and it was found infected with the alpha-proteobacterium Rickettsia bellii. To the best of our knowledge, this report constitutes the first record of the A. dubitatum - P. cancrivorus association. Fil: Eberhardt, María Ayelen Teresita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina Fil: Fernandez Basile, Camilo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina Fil: Zurvera, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina Fil: Monje, Lucas Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina

During two field trips in the state of Sao Paulo, two of us became infested by two adults, three nymphs, and one larva of the capybara tick, Amblyomma dubitatum Neumann, 1899 (= Amblyomma cooperi Nuttall and Warbuton, 1908). Previously, there has been only a single report of an A. dubitatum adult tick from humans. Our observations on human infestation by all parasitic stages of A. dubitatum suggest that this behavior may be more frequent than previously thought, especially in the case of immatures, which are herein reported from humans for the first time.

To date, three tick-borne pathogenic Rickettsia species have been reported in different regions of Argentina, namely, R. rickettsii, R. parkeri, and R. massiliae. However, there are no reports available for the presence of tick-borne pathogens from the northeastern region of Argentina. This study evaluated the infection with Rickettsia species of Amblyomma dubitatum ticks collected from vegetation and feeding from capybaras (Hydrochoerus hydrochaeris) in northeastern Argentina. From a total of 374 A. dubitatum ticks collected and evaluated by PCR for the presence of rickettsial DNA, 19 were positive for the presence of Rickettsia bellii DNA, two were positive for Rickettsia sp. strain COOPERI, and one was positive for the pathogenic Rickettsia sp. strain Atlantic rainforest. To our knowledge, this study is the first report of the presence of the human pathogen Rickettsia sp. strain Atlantic rainforest and Rickettsia sp. strain COOPERI in Argentina. Moreover, our findings posit A. dubitatum as a potential vector for this pathogenic strain of Rickettsia. Fil: Monje, Lucas Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina Fil: Nava, Santiago. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Eberhardt, María Ayelen Teresita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina Fil: Correa, Ana Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina Fil: Guglielmone, Alberto Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Beldomenico, Pablo Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2020-03-11T18:53:43Z No. of bitstreams: 1 2014 - Renata Kazuko Sakai.pdf: 1241567 bytes, checksum: c6e9b7af6c90e701b9cd3a1dc4729949 (MD5) Made available in DSpace on 2020-03-11T18:53:43Z (GMT). No. of bitstreams: 1 2014 - Renata Kazuko Sakai.pdf: 1241567 bytes, checksum: c6e9b7af6c90e701b9cd3a1dc4729949 (MD5) Previous issue date: 2014-02-25 Amblyomma dubitatum engorged females, naturally infected by Rickettsia bellii, were used to establish a laboratory colony. Larvae, nymphs, and adults were exposed to two strains of Rickettsia rickettsii by feeding on needle-inoculated guinea pigs, and thereafter reared on uninfected guinea pigs. After acquisition feeding, engorged larvae and nymphs molted to nymphs and adults, respectively, which were shown to be infected (confirming transstadial perpetuation), and were able to transmit both strains of R. rickettsia to uninfected animals, as demonstrated by clinical, serological, and molecular analyses. However, the larval, nymphal, and adult stages of A. dubitatum showed to be only partially susceptible to R. rickettsia infection, since in all cases, only part of the ticks became infected by this agent, after being exposed to rickettsemic animals. While transovarial transmission of R. rickettsii was inefficient in the A. dubitatum engorged females of the present study, 100% of these females passed R. bellii transovarially. Because it has been reported that a primary infection by a Rickettsia species would preclude transovarial transmission of a second Rickettsia species, it is likely that the ineffectiveness of A. dubitatum to perpetuate R. rickettsia by transovarial transmission was related to its primary infection by R. bellii; however, it could also be related to unknown factors inherent to A. dubitatum. The relevance of A. dubitatum as a natural vector of R. rickettsii to humans or animals is discussed. F?meas ingurgitadas de Amblyomma dubitatum, naturalmente infectadas por Rickettsia bellii, foram utilizadas para estabelecer uma col?nia de laborat?rio. Larvas, ninfas e adultos foram expostos a duas cepas de Rickettsia rickettsii alimentando-se em cobaias inoculadas e, posteriormente mantidas em cobaias n?o infectadas. Ap?s a alimenta??o, larvas e ninfas ingurgitadas mudaram para ninfas e adultos, respectivamente, que mostraram estar infectados (confirmando a perpetua??o transestadial), e foram capazes de transmitir ambas as cepas de R. rickettsii para animais n?o infectados, como demonstrado pela cl?nica, sorologia, e an?lises moleculares. No entanto, as fases de larvas, ninfas e adultos de A. dubitatum demonstraram ser apenas parcialmente suscept?vel a infec??o por R. rickettsii, uma vez que em todos os casos, apenas uma parte dos carrapatos se tornaram infectados por este agente, ap?s serem expostos a animais na fase de rickettisemia. Enquanto a transmiss?o transovariana de R. rickettsii foi ineficiente nas f?meas ingurgitadas de A. dubitatum do presente estudo, 100% dessas f?meas passaram R. bellii transovarianamente. Uma vez que foi relatado que uma infec??o prim?ria por uma esp?cie Rickettsia impediria a transmiss?o transovariana de uma segunda esp?cie de Rickettsia, ? prov?vel que a inefic?cia do A. dubitatum para perpetuar R. rickettsii por transmiss?o transovariana foi relacionada com infec??o prim?ria por R. bellii; no entanto, tamb?m pode estar relacionado a fatores desconhecidos inerentes ? A. dubitatum. A relev?ncia de A. dubitatum como um vetor natural de R. rickettsii aos seres humanos ou animais ? discutida.

El objetivo general de esta tesis doctoral fue proporcionar información sobre las características ecológicas que condicionan la presencia y abundancia de la garrapata del carpincho Amblyomma dubitatum. Se da a conocer la distribución actual de la misma en Sudamérica, como así también un modelo de nicho climático que proporciona información sobre una potencial distribución en esta área. Se describió distribución estacional de todos los estadios parasíticos y de vida libre, como así también los parámetros de infestación de su hospedador principal Hydrochoerus hydrochaeris generando información detallada del ciclo biológico en la naturaleza. Se proporcionaron datos sobre potenciales hospedadores alternativos de esta garrapata, a la vez que se establecieron las condiciones ambientales que favorecen y limitan al parásito y su medio. Los resultados del estudio sobre la distribución geográfica mostraron que A. dubitatum está asociada a una área restringida de Sudamérica, que incluye las provincias Biogeográficas de Pampa, Chaco, Cerrado, Bosque Atlántico Brasileño, Bosque Paranaense y Bosque de Araucaria angustifolia. La mayor parte de los registros se encontraron en el noreste de Argentina, sureste de Brasil, este de Paraguay y centro y este de Uruguay. El modelo de nicho climático reveló una potencial distribución de A. dubitatum para el centro y noreste de Argentina, Uruguay y sur de Brasil, que coincide con los hallazgos reportados para esta garrapata. También se observó una zona con características óptimas para A. dubitatum al noroeste de Sudamérica, en los países de Colombia y Venezuela. A pesar de que en estos países se encuentra su principal hospedador H. hydrochaeris, no hay registros de A. dubitatum en esa zona. De la integración de los datos se puede inferir que los factores mas importantes que limitan la distribución de A. dubitatum son la vegetación y el clima, no los hospedadores. Los trabajos de campo para el estudio del ciclo biológico y de potenciales hospedadores alternativos de A. dubitatum fueron realizados en la Estancia “Rincón del Socorro” en los Esteros del Iberá, Corrientes. El ciclo biológico de A. dubitatum fue descripto mediante el estudio de la distribución estacional de los tres estadios en su etapa parasítica y de vida libre. Para esto se examinaron tres H. hydrochaeris por mes durante dos años consecutivos y simultáneamente se tomaron muestras de las garrapatas presentes en la vegetación en tres ambientes diferentes y a tres horarios distintos del día. Asimismo, se registraron los periodos de desarrollo en distintas condiciones de fotoperíodo y temperatura de especímenes ingurgitados de los tres estadios expuestos en condiciones de campo y laboratorio. La infestación de H. hydrochaeris con larvas de A. dubitatum se observó a lo largo de todo el año, con picos de abundancia en otoño e invierno, la mayor infestación se registró en mayo. Las ninfas fueron registradas de forma continua en los dos años de muestreo. Los mayores picos de abundancia fueron observaron en invierno, y los meses de mayor infestación fueron julio y agosto. El parasitismo de las hembras halladas sobre H. hydrochaeris fue encontrado, al igual que los inmaduros, durante todo el año. Los mayores picos de abundancia se registraron en primavera y verano, y los meses de mayor abundancia fueron noviembre, enero y febrero. Durante los muestreos de A. dubitatum en su estado no parasítico, se colectaron larvas a lo largo de todo el año sobre la vegetación, con picos de abundancia en los meses de febrero y marzo. Con respecto a los distintos ambientes donde se realizaron los muestreos, el monte fue el sitio donde se colectaron el mayor número de larvas, y no se hallaron diferencias en los distintos horarios del muestreo. Con la técnica empleada (arrastrar un paño o dragging), se colectaron un escaso número de ninfas (n=28) y no se colectaron adultos. Por otro lado, los distintos estadios ingurgitados (larvas y ninfas) expuestos en condiciones naturales, en las cuatro estaciones del año, mudaron a ninfas y adultos, respectivamente. Los mayores periodos de premuda se observaron en exposiciones realizadas en la estación fría, donde las larvas retrasaron su muda hasta comienzo de la primavera y las ninfas hasta finales de la misma estación. Las hembras ingurgitadas expuestas en todas las estaciones colocaron huevos que eclosionaron. Al igual que los estadios inmaduros, los mayores retrasos en el periodo de preoviposición y de incubación se observaron en exposiciones realizadas en la estación fría, que resultaron en larvas activas en verano. No se registraron diferencias significativas para los periodos de preoviposición ni en los periodos de incubación entre los grupos de hembras expuestas a los distintos regímenes de fotoperíodo en condiciones de laboratorio. Las diferencias entre los grupos de ninfas fueron estadísticamente significativas, pero carecen de significancia biológica, ya que los extremos en el rango de la media del periodo de premuda difieren solo por 2,0 días. Asimismo, se detectaron diferencias significativas en los periodos de premuda de larvas entre los grupos expuestos a diferentes regímenes de fotoperíodos, pero al igual que lo ocurrido con las ninfas, la diferencia de 10 días no posee importancia biológica en un ciclo anual. A pesar de los retrasos en el desarrollo de los tres estadios de A. dubitatum expuestas en condiciones naturales, que fueron observados en las estaciones climáticas más frías y con menos horas de luz diaria, se descarta una posible presencia de diapausa morfogenética debido a que en los resultados obtenidos en laboratorio bajo condiciones controladas no se observaron estos retrasos. Sintetizando lo mencionado anteriormente, el ciclo biológico de A. dubitatum en la naturaleza, bajo las condiciones de los humedales en la provincia de Corrientes, se definió por la presencia de larvas desde mediados de verano a finales de invierno, con picos de abundancia en otoño y principios de invierno, que originarán ninfas que estarán presentes desde otoño hasta comienzo de la primavera. Estas ninfas mudarán secuencialmente en garrapatas adultas que se encontraran sobre los hospedadores desde mediados de primavera hasta finales del verano. Teniendo en cuenta los periodos de preoviposición obtenidos en este estudio en garrapatas expuestas en laboratorio y en el campo, se deduce que las hembras que se alimentan e ingurgiten en este periodo, pondrán sus huevos en verano y otoño a partir de los cuales emergerán las larvas que comenzarán a estar activas en otoño e invierno. La asociación de A. dubitatum con H. hydrochaeris fue caracterizada por altos valores de prevalencia y abundancia y una falta de relación entre atributos del hospedador (sexo, condición corporal y tamaño corporal) y carga de parásitos. El análisis de la distribución anatómica mostró que ninfas de A. dubitatum fueron más segregadas espacialmente sobre el cuerpo del hospedador que larvas y adultos. El mayor grado de solapamiento de nicho (0,70) fue encontrado entre adultos y ninfas, indicando que estos estadios pueden tener un uso similar del microhábitat sobre un hospedador. De acuerdo con los resultados de este trabajo, larvas de A. dubitatum prefieren fijarse sobre las áreas III (lomo) y V (cuarto trasero), ninfas sobre el área IV (abdomen) y adultos sobre las áreas I (cabeza), II (cuello y miembro anterior) y IV, aunque es importante tener en cuenta que los tres estadios fueron hallados en las cinco áreas. La amplitud de nicho de larvas y ninfas de A. dubitatum fue más estrecha que la de adultos. Las diferencias en el grado de agregación de A. dubitatum están probablemente relacionadas a la distribución espacial de las garrapatas en el ambiente y no a las diferencias entre individuos dentro de una población de hospedadores. Un gran número de especímenes de H. hydrochaeris están presentes en el área donde se realizó esta investigación. Por lo tanto, los factores asociados al hospedador que determinan los altos niveles de infestación con A. dubitatum en poblaciones de H. hydrochaeris podrían asignarse a una combinación de propiedades del hospedador a nivel poblacional como abundancia, ubicuidad y agregación, más que a atributos específicos individuales relacionados a la condición corporal, masa corporal o sexo. También se realizaron muestreos para determinar si aves y roedores (Cricetidae y Caviidae) tienen un rol fundamental como hospedadores alternativos de A. dubitatum. Para la captura de estos roedores se utilizaron trampas de captura viva tipo Sherman y Tomahawk y para las aves se utilizaron redes de niebla. Se capturaron 65 roedores pertenecientes a cuatro especies (tres de la familia Cricetidae y una de la familia Caviidae) y 84 aves passeriformes pertenecientes a 32 especies distribuidas en 10 familias. Con la metodología de trampeo empleada también fueron capturados seis pequeños marsupiales pertenecientes a dos géneros de la familia Didelphidae. Los datos obtenidos indicaron altos niveles de infestación con larvas de A. dubitatum en roedores cricétidos y Cavia aperea, aunque los valores de prevalencia y abundancia media (AM) fueron significativamente mayores en roedores cricétidos que en C. aperea. Asimismo, los niveles de agregación fueron menores en los roedores cricétidos, demostrando una mayor exposición de los mismos a las larvas de A. dubitatum. La baja prevalencia y la alta agregación de larvas parasitando aves paseriformes indicaron que estas sólo son hospedadores ocasionales para las larvas de esta garrapata. Ninfas de A. dubitatum fueron colectadas sobre Akodon azarae y C. aperea, siendo los valores de prevalencia y abundancia media en C. aperea significativamente más altos que en A. azarae. Los resultados obtenidos tras los muestreos de campo sugieren que los roedores cricétidos y C. aperea son hospedadores relevantes para los preimagos de A. dubitatum, sin embargo, para completar su desarrollo una garrapata además de encontrar y fijarse a un hospedador, debe alimentarse adecuadamente sobre éste para completar su ingurgitamiento y mudar al estadio siguiente. Para evaluar la capacidad biológica de larvas y ninfas de A. dubitatum para alimentarse adecuadamente en roedores y aves, se realizaron infestaciones experimentales con inmaduros de A. dubitatum sobre tres especies de hospedadores representativos de los taxones muestreados en el campo: Mus musculus, Cavia porcellus y Gallus gallus. La información obtenida por las infestaciones experimentales sustentan los datos de los muestreos de campo y confirman la hipótesis sobre la aptitud de roedores cricétidos y C. aperea como hospedadores de los estadios inmaduros de A. dubitatum. Durante las infestaciones experimentales los tres grupos de hospedadores utilizados en este estudios resultaron ser competentes para alimentar estadios inmaduros de A. dubitatum, recuperándose larvas y ninfas ingurgitadas en todas las infestaciones realizadas, las que mudaron al siguiente estadio. Fil: Debárbora, Valeria Natalia. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentina. Fil: Mangold, Atilio José. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; Argentina. Fil: Nava, Santiago. Instituto Nacional de Tecnología Agropecuaria. Estación Experimental Agropecuaria Rafaela; Argentina. Fil: Oscherov, Elena Beatriz. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas, Naturales y Agrimensura; Argentina.

Hydrochoerus hydrochaeris serves as a host for a number of tick species that play an important role as vectors of emergent zoonotic diseases. This is the first report of the occurrence of Amblyomma cajennense adults and Amblyomma dubitatum nymphs retrieved from capybaras run over on two highways in the state of Santa Catarina, southern Brazil. Key words: Ticks, ixodidae, biology, morphology, nymphs

Foi pesquisada a presença de riquétsias em 3.545 carrapatos Amblyomma cajennense e 2.666 Amblyomma dubitatum. Através do teste de hemolinfa, reação em cadeia pela polimerase e isolamento de rickettsia em cultivo celular, todos os Amblyomma cajennense foram negativos, sendo que 634 (23,8%) Amblyomma dubitatum mostraram-se infectados com Rickettsia bellii. The presence of rickettsial infection was surveyed in 3,545 Amblyomma cajennense ticks and 2,666 Amblyomma dubitatum ticks. Using the hemolymph test, polymerase chain reaction and isolation of Rickettsia in cell cultures, all of the Amblyomma cajennense were negative, whereas 634 (23.8%) of the Amblyomma dubitatum ticks were shown to be infected with Rickettsia bellii.

Com o objetivo de obtermos isolados de Rickettsia spp. para confirmar as evidências sobre o papel do A. dubitatum e do A. triste na transmissão de riquétsia do GFM no Brasil e Uruguai, respectivamente, realizou-se em áreas endêmicas para febre maculosa nesses dois países, a avaliação da presença de riquétsia em carrapatos da espécie A. dubitatum no município de Pedreira, estado de São Paulo e em carrapatos da espécie A. triste, em uma área suburbana no sudeste do Uruguai, além da tentativa de isolamento em cultivo de células Vero e posterior caracterização molecular de isolados provenientes dessas duas espécies de carrapatos. Foram coletados um total de 841 (367 machos e 474 fêmeas) carrapatos adultos da espécie A. dubitatum e 78 (25 machos e 53 fêmeas) amostras de A. triste, os quais foram submetidos ao teste de hemolinfa. Todas as amostras foram submetidas à extração de DNA e testadas pela técnica da PCR para o gene gltA, presente em todas as espécies de riquétsias. Dos 841 A. dubitatum colhidos, em 153 (18,18%) amostras de hemolinfa foram observados organismos morfologicamente compatíveis com riquétsias, 452 foram negativas (53,74%) e 236 (28,06%) amostras de carrapatos foram inconclusivas. Todas as 78 amostras de carrapatos da espécie A. triste provenientes do Uruguai foram negativas no teste de hemolinfa. Dos 841 A. dubitatum, um total de 378 (44,94%) amostras foram positivas para o gene gltA e, posteriormente, foram testadas para o gene ompA, sendo que nenhuma das amostras foi positiva. Dos 378 A. dubitatum positivos na PCR, o produto amplificado de 93 foi seqüenciado, sendo todos identificados como Rickettsia bellii de acordo com seqüências disponíveis no GenBank. Das 78 amostras de carrapatos da espécie A. triste, provenientes do Uruguai, duas amostras, denominadas de carrapatos #5 e #35, foram positivas na PCR e, submetidas à tentativa de isolamento em células Vero, pela técnica de \"shell vial\". O estabelecimento do isolado de riquétsia somente foi obtido com sucesso do carrapato #5, sendo este isolado designado de At#5-URG, o qual foi depositado como amostra de referência em nosso laboratório. Amostras de DNA do isolado At#5-URG foram testadas para uma bateria de oligonucleotídeos iniciadores objetivando a amplificação de fragmentos de mais três genes de riquétsias: gltA, ompB e omp, os quais foram, posteriormente seqüenciados e os fragmentos de 1.084, 775 e 491 nucleotídeos dos genes gltA, ompB e ompA, respectivamente, foram obtidos e mostraram 100% de identidade com as seqüências correspondentes disponíveis no GenBank para a cepa Maculatum de Rickettsia parkeri dos EUA. Owing to the potential role of the tick Amblyomma dubitatum and Amblyomma triste in the transmission of the Spotted Fever Group (SFG) Rickettsia, this study evaluated infection by Rickettsia in ticks collected in Brazil and Uruguay, where rickettsial infection is endemic. A total of 841 (367 males e 474 females) A. dubitatum adult ticks were collected in Pedreira, an area of Brazilian Spotted Fever (BSF) endemicity in the state of São Paulo, and 78 adult ticks (25 males, 53 females) identified as A. triste were collected from vegetation in the suburban area of Toledo Chico, southern Uruguay. At the laboratory, all samples were individually processed by the hemolymph test with Gimenez staining and PCR targeting a fragment of the rickettsial gene gltA, present in all Rickettsia species. From 841 A. dubitatum ticks tested by the hemolymph test, 153 (18.18%) samples were positive, 452 (53.74%) were negative, and 236 (28.06%) were inconclusive. All 78 samples of A. triste ticks from Uruguay were negative by the hemolymph test. All 841 samples of A. dubitatum were submitted to PCR, being 378 (44.94%) positive and afterwards tested by PCR targeting a 150-bp fragment of the ompA (a major outer membrane protein A present only in SFG Rickettsia), being all samples negative. From the 378 PCR-positive samples of A. dubitatum, DNA sequence was determined for 93 samples, being all identified as Rickettsia bellii according to GenBank available sequences. For the A. triste samples, only 2 ticks (1 male, 1 female) yielded expected amplicons by PCR. Rickettsia isolation in cell culture was attempted by using the shell vial technique from these two PCR-positive ticks. Rickettsiae were successfully isolated and established in Vero cell culture from the female tick. This isolate, designated as At#5-URG, has been deposited as a reference strain in the Rickettsial Collection of Faculty of Veterinary Medicine in the University of São Paulo. DNA extracted from infected cells of the third passage was tested by a battery of PCRs that used primer pairs targeting fragments of 3 rickettsial genes: gltA, ompB (a major outer membrane protein B), and ompA. PCR products of expected size were obtained in all reactions and subjected to DNA sequencing. Fragments of 1,084, 775, and 491 bp of the gltA, ompB, and ompA genes, respectively, were obtained and showed 100% identity to the corresponding sequences available in GenBank for the Maculatum strain of Rickettsia parkeri from United States.

Amblyomma dubitatum apresenta importante papel como vetor de riquétsias na natureza. O objetivo do presente trabalho foi avaliar a atividade carrapaticida do carvacrol sobre larvas e ninfas não ingurgitadas de A. dubitatum. A realização dos experimentos ocorreu através do teste de pacote de larvas e ninfas, sendo colocadas no centro de papel filtro, dobrado ao meio, fechado nas laterais com clipes binder e umedecido com 90 μL da solução testada em cada lado. Os grupos foram mantidos em câmara climatizada (27±1°C e UR>80±10) individualizadas. As concentrações testadas foram de 2,5; 7,5; 10; 15 e 20 mg/mL, com 10 repetições para larvas e sete para ninfas por tratamento. Foram formados dois grupos controle para cada estágio: água e etanol 70% (larvas) e água e DMSO 3% (ninfas). A mortalidade de larvas não ingurgitadas tratadas com a menor concentração de carvacrol foi 45,7%, sendo estatisticamente similar (p>0,05) para o grupo controle. Houve diferença estatística (p0,05) a concentração 7,5 mg/mL. Para ninfas não ingurgitadas, a menor concentração não resultou em mortalidade, alcançando percentual de mortalidade de 65,7% na concentração de 20 mg/mL. A partir da concentração 10 mg/mL houve diferença estatística (p80±10%) individuals. The concentrations tested were of 2,5; 7,5; 10; 15 e 20 mg/mL, with ten repetitions for larvae and seven for nymphs per treatment. Were formed two control groups for each stage: water and etanol 70% (larvae) and water and DMSO 3% (nymphs). The mortality of unengorged larvae treated with a lowest concentration of carvacrol was 45,7%, being similar statistically (p>0,05) to the control group. The was difference statistic (p0,05) the concentration7,5 mg/mL. For the nymphs unengorged the lowest concentration did't resulted in mortality, reaching mortality percentual of 65,7% in concentration of 20 mg/mL. From concentration of 10 mg/mL there was difference statistic of (p

O ciclo biológico do Amblyomma dubitatum, que se alimentava experimentalmente em coelhos domésticos, foi avaliado em condições laboratoriais e comparado com dados recentemente obtidos de infestações experimentais em capivaras (Hydrochaeris hydrochaeris), hospedeiros naturais para essa espécie. Os coelhos foram considerados hospedeiros experimentais adequados para larvas e ninfas porque quatro dos cinco parâmetros avaliados (número de carrapatos que ingurgitaram, período de alimentação, percentagem de carrapatos que realizaram muda e período de pré-muda) foram semelhantes aos resultados obtidos com capivaras. As percentagens diárias de desprendimento e de muda das larvas e ninfas confirmam os coelhos como hospedeiros experimentais adequados para esses estágios de A. dubitatum. Os resultados do experimento indicam que os coelhos são hospedeiros inadequados para os adultos.

O ciclo biologico do Amblyomma dubitatum, que se alimentava experimentalmente em coelhos domesticos, foi avaliado em condicoes laboratoriais e comparado com dados recentemente obtidos de infestacoes experimentais em capivaras (Hydrochaeris hydrochaeris), hospedeiros naturais para essa especie. Os coelhos foram considerados hospedeiros experimentais adequados para larvas e ninfas porque quatro dos cinco parâmetros avaliados (numero de carrapatos que ingurgitaram, periodo de alimentacao, percentagem de carrapatos que realizaram muda e periodo de pre-muda) foram semelhantes aos resultados obtidos com capivaras. As percentagens diarias de desprendimento e de muda das larvas e ninfas confirmam os coelhos como hospedeiros experimentais adequados para esses estagios de A. dubitatum. Os resultados do experimento indicam que os coelhos sao hospedeiros inadequados para os adultos.

Amblyomma dubitatum engorged females, naturally infected by Rickettsia bellii, were used to establish a laboratory colony. Larvae, nymphs, and adults were exposed to two strains of Rickettsia rickettsii by feeding on needle-inoculated guinea pigs, and thereafter reared on uninfected guinea pigs. After acquisition feeding, engorged larvae and nymphs molted to nymphs and adults, respectively, which were shown to be infected (confirming transstadial perpetuation), and were able to transmit both strains of R. rickettsii to uninfected animals, as demonstrated by clinical, serological, and molecular analyses. However, the larval, nymphal, and adult stages of A. dubitatum showed to be only partially susceptible to R. rickettsii infection, since in all cases, only part of the ticks became infected by this agent, after being exposed to rickettsemic animals. While transovarial transmission of R. rickettsii was inefficient in the A. dubitatum engorged females of the present study, 100% of these females passed R. bellii transovarially. Because it has been reported that a primary infection by a Rickettsia species would preclude transovarial transmission of a second Rickettsia species, it is likely that the ineffectiveness of A. dubitatum to perpetuate R. rickettsii by transovarial transmission was related to its primary infection by R. bellii; however, it could also be related to unknown factors inherent to A. dubitatum. The relevance of A. dubitatum as a natural vector of R. rickettsii to humans or animals is discussed.