Novel genotypes of Hepatozoon spp. in small mammals, Brazil.

BACKGROUND: Small mammals (rodents and marsupials) have been poorly explored for the occurrence of apicomplexan (genus Hepatozoon and genera of the order Piroplasmorida) and Anaplasmataceae agents in Brazil. Thus, this study investigated the occurrence of Hepatozoon spp., Piroplasmorida, and Anaplasmataceae agents in small mammals in seven forest fragments in Brazil. METHODS: During 2015-2018, small mammals were captured in six forest fragments in the State of São Paulo (Cerrado and Atlantic Forest biomes) and one fragment in the State of Mato Grosso do Sul (Pantanal biome). Mammal blood, liver, spleen, and lung samples were tested molecularly for the presence of DNA of Hepatozoon, Piroplasmorida, and Anaplasmataceae agents. RESULTS: A total of 524 mammals were captured, comprising seven species of marsupials, 14 rodents, two carnivores, and one Cingulata. Four novel haplotypes (1, 2, 3, 4) of Hepatozoon spp. were detected in small mammals from different biomes. In São Paulo state, haplotype 1 was detected in rodents from Cerrado and a transition area of Cerrado and Atlantic Forest biomes, whereas haplotype 2 was detected in rodents from the Atlantic Forest biome. On the other hand, haplotypes 3 and 4 were restricted to rodents and marsupials, respectively, from the Pantanal biome of Mato Grosso do Sul. No host species shared more than one haplotype. Despite these distinct geographical and host associations, our phylogenetic analyses indicated that the four Hepatozoon haplotypes belonged to the same clade that contained nearly all haplotypes previously reported on rodents and marsupials, in addition to several reptile-associated haplotypes from different parts of the world. No mammal samples yielded detectable DNA of Piroplasmorida agents. On the other hand, the Anaplasmataceae-targeted polymerase chain reaction (PCR) assay amplified a sequence 100% identical to the Wolbachia pipientis endosymbiont of the rodent filarid Litomosoides galizai. CONCLUSIONS: We report a variety of Hepatozoon haplotypes associated with small mammals in three Brazilian biomes: Cerrado, Atlantic Forest, and Pantanal. Through phylogenetic analyses, the Hepatozoon agents grouped in the rodent-marsupial-reptile large clade of Hepatozoon spp. from the world. The detection of a W. pipientis associated with the rodent filarid L. galizai indicates that the rodent was infected by filarial nematodes.

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.

Immature ticks on wild birds and the molecular detection of a novel Rickettsia strain in the Ibitipoca State Park, southeastern Brazil.

Birds are recognized hosts of ticks, especially for the immature stages which may harbor various species and strains of Rickettsia. To explore landscapes inhabited by birds and their ticks would expand the knowledge on host-parasite relationships and the rickettsiae. The aim of this paper was to record the diversity of ticks collected on wild birds and assess the phylogenetic position of a novel Rickettsia strain detected in immature ticks. Birds were captured in the Ibitipoca State Park, located in the Minas Gerais state, southeastern Brazil, as part of a long-term research project on the ecology of ticks, birds and Rickettsia. We found three tick species parasitizing birds: Amblyomma aureolatum (63 larvae, 10 nymphs), Haemaphysalis leporispalustris (28 larvae, seven nymphs) and Amblyomma romarioi (27 larvae). Among these, A. aureolatum was the most abundant species including 54% (73/135) of the collected ticks. New tick-host records were: A. romarioi on Turdus amaurochalinus and H. leporispalustris on Thamnophilus caerulescens, Saltator similis and Zonotrichia capensis. Of the 82 ticks tested for Rickettsia spp. by PCR, two larvae (2.5%) of A. romarioi were infected with 'Candidatus Rickettsia paranaensis', a novel putative Rickettsia species closely related to Rickettsia africae, Rickettsia sibirica and Rickettsia parkeri, as corroborated by our phylogenetic analysis. Finally, we present a list of all records of immature stages of H. leporispalustris on passerine birds in Brazil.

"Candidatus Borrelia ibitipoquensis," a Borrelia valaisiana-Related Genospecies Characterized from Ixodes paranaensis in Brazil.

Borrelia burgdorferi sensu lato (Bbsl) spirochetes include the agents of Lyme borreliosis in temperate regions of the Northern Hemisphere, and merge their transmission cycles mainly with ticks of the Ixodes ricinus complex. Twenty genospecies compose Bbsl currently, and with the exception of Borrelia chilensis, and Borrelia garinii, all have been described only for North America, Europe, North Africa, and Asia. Here, we collected specimens of Ixodes paranaensis, a tick associated with swifts in a Brazilian natural park from the state of Minas Gerais, and performed a molecular characterization of 11 borrelial genes. Based on comparisons of inter and intraspecific genetic divergences, and Bayesian phylogenetic trees inferred for 16S rRNA, flaB, p66, and concatenated clpA, clpX, pepX, pyrG, recG, nifS rlpB, and uvrA genes, we demonstrate the occurrence of a new genospecies of Bbsl. "Candidatus Borrelia ibitipoquensis" Ip37 is closely related to Borrelia sp. Am501, and Borrelia valaisiana, a spirochete transmitted by ticks of the I. ricinus complex in Eurasia that uses birds as reservoirs. In a similar ecological scenario involving ticks and avian hosts, the migratory swift Streptoprocne biscutata is the sole-documented bird associated with I. paranaensis, and, although not assessed in this study, could correspond to the vertebrate reservoir of this newly described genospecies in Brazil. Pathogenic roles of "Ca. B. ibitipoquensis" are still unknown. However, its possible vector I. paranaensis is not an anthropophilic tick, so human infections would be unlikely to occur. Our finding enhances the knowledge on Bbsl in South America, highlights the occurrence of ecologically and genetically related genospecies with vastly separated geographical distributions, and calls for the attention to explore a barely known diversity of spirochetes of this group in the region.

Comparative survival of the engorged stages of Amblyomma dubitatum and Amblyomma sculptum in the laboratory: Implications for Brazilian spotted fever epidemiology.

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.

Epidemiology of capybara-associated Brazilian spotted fever.

BACKGROUND: Brazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii, has been associated with the transmission by the tick Amblyomma sculptum, and one of its main hosts, the capybara (Hydrochoerus hydrochaeris). METHODS: During 2015-2019, we captured capybaras and ticks in seven highly anthropic areas of São Paulo state (three endemic and four nonendemic for BSF) and in two natural areas of the Pantanal biome, all with established populations of capybaras. RESULTS: The BSF-endemic areas were characterized by much higher tick burdens on both capybaras and in the environment, when compared to the BSF-nonendemic areas. Only two tick species (A. sculptum and Amblyomma dubitatum) were found in the anthropic areas; however, with a great predominance of A. sculptum (≈90% of all ticks) in the endemic areas, in contrast to a slight predominance of A. dubitatum (≈60%) in the nonendemic areas. Tick species richness was higher in the natural areas, where six species were found, albeit with a predominance of A. sculptum (≈95% of all ticks) and environmental tick burdens much lower than in the anthropic areas. The BSF-endemic areas were characterized by overgrowth populations of A. sculptum that were sustained chiefly by capybaras, and decreased populations of A. dubitatum. In contrast, the BSF-nonendemic areas with landscape similar to the endemic areas differed by having lower tick burdens and a slight predominance of A. dubitatum over A.sculptum, both sustained chiefly by capybaras. While multiple medium- to large-sized mammals have been incriminated as important hosts for A. sculptum in the natural areas, the capybara was the only important host for this tick in the anthropic areas. CONCLUSIONS: The uneven distribution of R. rickettsii infection among A. sculptum populations in highly anthropic areas of São Paulo state could be related to the tick population size and its proportion to sympatric A. dubitatum populations.

A new species of Amblyomma (Acari: Ixodidae) associated with monkeys and passerines of the Atlantic rainforest biome, Southeastern Brazil.

Recent studies have reported several larvae of an unidentified Amblyomma species on passerine birds in Atlantic rainforest fragments in southeastern Brazil. These larvae yielded a unique 16S rRNA haplotype designated as Amblyomma sp. haplotype Nazaré, which showed nucleotide identity levels of 91% to Amblyomma parkeri Fonseca & Aragão, 1952 and 88% to Amblyomma longirostre (Koch, 1844). Herein, we describe Amblyomma sp. haplotype Nazaré as a new species, Amblyomma romarioi n. sp. Martins, Luz & Labruna, through a formal description of the male and female adult stages. Amblyomma romarioi is morphologically and genetically most closely related to A. parkeri, A. longirostre and Amblyomma geayi Neumann, 1899. Among males, the rectangular basis capituli and rounded coxa I spurs separates A. romarioi from A. parkeri, A. longirostre, and A. geayi, which have basis capituli triangular or slightly hexagonal, and pointed coxa I spurs. Among females, the V-shaped genital aperture and coxa I rounded spurs of A. romarioi contrasts to the U-shaped genital aperture and coxa I pointed spurs in A. parkeri, A. longirostre, and A. geayi. Larvae of A. romarioi have been collected on 24 species of passerines. The few records of nymphs and adults were on the black-fronted titi monkey Callicebus nigrifrons (Spix, 1823). The current distribution of A. romarioi is restricted to the Brazilian Atlantic rainforest, southeastern Brazil, in areas with altitude between 363 and 1600 m, within the distribution of C. nigrifrons. We discuss ecological features of Amblyomma romarioi, comparatively to A. parkeri, A. longirostre and A. geayi. The present study increases the Brazilian tick fauna to 74 species.

A new species of Amblyomma (Acari: Ixodidae) associated with monkeys and passerines of the Atlantic rainforest biome, Southeastern Brazil

Recent studies have reported several larvae of an unidentified Amblyomma species on passerine birds in Atlantic rainforest fragments in southeastern Brazil. These larvae yielded a unique 16S rRNA haplotype designated as Amblyomma sp. haplotype Nazaré, which showed nucleotide identity levels of 91% to Amblyomma parkeri Fonseca & Aragão, 1952 and 88% to Amblyomma longirostre (Koch, 1844). Herein, we describe Amblyomma sp. haplotype Nazaré as a new species, Amblyomma romarioi n. sp. Martins, Luz & Labruna, through a formal description of the male and female adult stages. Amblyomma romarioi is morphologically and genetically most closely related to A. parkeri, A. longirostre and Amblyomma geayi Neumann, 1899. Among males, the rectangular basis capituli and rounded coxa I spurs separates A. romarioi from A. parkeri, A. longirostre, and A. geayi, which have basis capituli triangular or slightly hexagonal, and pointed coxa I spurs. Among females, the V-shaped genital aperture and coxa I rounded spurs of A. romarioi contrasts to the U-shaped genital aperture and coxa I pointed spurs in A. parkeri, A. longirostre, and A. geayi. Larvae of A. romarioi have been collected on 24 species of passerines. The few records of nymphs and adults were on the black-fronted titi monkey Callicebus nigrifrons (Spix, 1823). The current distribution of A. romarioi is restricted to the Brazilian Atlantic rainforest, southeastern Brazil, in areas with altitude between 363 and 1600?m, within the distribution of C. nigrifrons. We discuss ecological features of Amblyomma romarioi, comparatively to A. parkeri, A. longirostre and A. geayi. The present study increases the Brazilian tick fauna to 74 species.

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.

Rickettsia amblyommatis infecting ticks and exposure of domestic dogs to Rickettsia spp. in an Amazon-Cerrado transition region of northeastern Brazil.

This study was performed in Maranhão state, a transition area two Brazilian biomes, Amazon and Cerrado. During 2011-2013, 1,560 domestic dogs were sampled for collection of serum blood samples and ticks in eight counties (3 within the Amazon and 5 within the Cerrado). A total of 959 ticks were collected on 150 dogs (9.6%). Rhipicephalus sanguineus sensu lato (s.l.) was the most abundant tick (68% of all collected specimens), followed by Amblyomma cajennense sensu lato (s.l.) (12.9%), Amblyomma parvum (9.2%), and Amblyomma ovale (5.2%). Other less abundant species (<1%) were Amblyomma oblongoguttatum, Rhipicephalus microplus, Haemaphysalis juxtakochi, and Amblyomma rotundatum. Females of A. cajennense s.l. ticks were morphologically identified as A. cajennense sensu stricto (s.s.) or A. sculptum. Molecular analyses of 779 canine ticks revealed three Rickettsia species: Rickettsia amblyommatis in 1% (1/100) A. cajennense s.l., 'Candidatus Rickettsia andeanae' in 20.7% (12/58) A. parvum, Rickettsia bellii in 6.8% (3/44) A. ovale and 100% (1/1) A. rotundatum ticks. An additional collection of A. sculptum from horses in a Cerrado area, and A. cajennense s.s. from pigs in an Amazon area revealed R. amblyommatis infecting only the A. cajennense s.s. ticks. Serological analysis of the 1,560 canine blood samples revealed 12.6% canine seroreactivity to Rickettsia spp., with the highest specific seroreactivity rate (10.2%) for R. amblyommatis. Endpoint titers to R. amblyommatis were significantly higher than those for the other Rickettsia antigens, suggesting that most of the seroreactive dogs were exposed to R. amblyommatis-infected ticks. Highest canine seroreactivity rates per locality (13.1-30.8%) were found in Amazon biome, where A. cajennense s.s. predominated. Lowest seroreactivity rates (1.9-6.5%) were found in Cerrado localities that were further from the Amazon, where A. sculptum predominated. Multivariate analyses revealed that canine seroreactivity to Rickettsia spp. or R. amblyommatis was statistically associated with rural dogs, exposed to Amblyomma ticks.

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.

Geographical distribution of Amblyomma cajennense (sensu lato) ticks (Parasitiformes: Ixodidae) in Brazil, with description of the nymph of A. cajennense (sensu stricto).

BACKGROUND: Until recently, Amblyomma cajennense (Fabricius, 1787) was considered to represent a single tick species in the New World. Recent studies have split this taxon into six species. While the A. cajennense species complex or A. cajennense (sensu lato) (s.l.) is currently represented by two species in Brazil, A. cajennense (sensu stricto) (s.s.) and Amblyomma sculptum Berlese, 1888, their geographical distribution is poorly known. METHODS: The distribution of the A. cajennense (s.l.) in Brazil was determined by morphological examination of all lots of A. cajennense (s.l.) in two large tick collections of Brazil, and by collecting new material during three field expeditions in the possible transition areas between the distribution ranges of A. cajennense (s.s.) and A. sculptum. Phylogenetic analysis inferred from the ITS2 rRNA gene was used to validate morphological results. Morphological description of the nymphal stage of A. cajennense (s.s.) is provided based on laboratory-reared specimens. RESULTS: From the tick collections, a total 12,512 adult ticks were examined and identified as 312 A. cajennense (s.s.), 6,252 A. sculptum and 5,948 A. cajennense (s.l.). A total of 1,746 ticks from 77 localities were collected during field expeditions, and were identified as 249 A. cajennense (s.s.), 443 A. sculptum, and 1,054 A. cajennense (s.l.) [these A. cajennense (s.l.) ticks were considered to be males of either A. cajennense (s.s.) or A. sculptum]. At least 23 localities contained the presence of both A. cajennense (s.s.) and A. sculptum in sympatry. DNA sequences of the ITS2 gene of 50 ticks from 30 localities confirmed the results of the morphological analyses. The nymph of A. cajennense (s.s.) is morphologically very similar to A. sculptum. CONCLUSION: Our results confirmed that A. cajennense (s.l.) is currently represented in Brazil by only two species, A. cajennense (s.s.) and A. sculptum. While these species have distinct distribution areas in the country, they are found in sympatry in some transition areas. The current distribution of A. cajennense (s.l.) has important implications to public health, since in Brazil A. sculptum is the most important vector of the bacterium Rickettsia rickettsii, the etiological agent of Brazilian spotted fever.

Experimental infection with Rickettsia rickettsii in an Amblyomma dubitatum tick colony, naturally infected by Rickettsia bellii.

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.

Morphological description of the nymphal stage of Amblyomma geayi and new nymphal records of Amblyomma parkeri.

The external morphology of the nymph of Amblyomma geayi Neumann is described by optical and scanning electron microscopy. Unfed nymphs were obtained from an engorged A. geayi female, which had been collected on a sloth (Bradypus variegatus) from Belém municipality, State of Pará, northern Brazil, and was kept under laboratory conditions. With the present description, we propose a modification of a taxonomic key published in 2010 for the Amblyomma nymphs that occur in Brazil, through the inclusion of A. geayi. The nymph of A. geayi is morphologically very similar to the nymph of Amblyomma parkeri Fonseca and Aragão, with only slight morphological differences related to scutal surface and punctuations (more shagreened and less punctuated in A. geayi). These 2 nymphs differ from all other known Amblyomma nymphs from Brazil by the combination of auriculae present as small posterolateral rounded projections, eyes located at the level of the scutal midlength, and a rounded hypostome. These nymphal similarities as well the morphology of the adult stage corroborate previous studies that showed that A. geayi and A. parkeri are genetically closely related. Unpublished host records of the nymphs of both A. geayi and A. parkeri are provided. Established populations of A. geayi and A. parkeri seem to be geographically separated, since all confirmed records of A. geayi are from the northern half of South America (mainly the Amazonian region) and Central America, whereas all known records of A. parkeri are from the Atlantic rainforest biome in northeastern, southeastern, and southern Brazil.

Description of larva of Amblyomma romitii (Acari: Ixodidae) by optical and scanning electron microscopy, including porotaxy and phylogenetic analysis.

The description of the larva of Amblyomma romitii Tonelli-Rondelli is based on optical and scanning electron microscopy. Larvae were obtained under laboratory conditions from an engorged female collected on capybara from Rurópolis municipality, State of Pará, Northern Brazil. Several characters are presented including the chaetotaxy of idiosoma, palpi and Haller's organ. The larval porotaxy (topographical and numerical patterns of integumentary structures) was presented and compared to that of the other Amblyomma spp. larvae. The mitochondrial 16S rDNA partial sequence of A. romitii generated in the present study was aligned with sequences previously determined for other Amblyomma species available in Genbank and with some species presently sequenced. The larval morphology of A. romitii and other Neotropical Amblyomma spp. larvae is discussed as well as the DNA sequence and its phylogenetic position among other species of the genus.