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The bacterium Rickettsia rickettsiiis the agent of Brazilian spotted fever (BSF), a highly fatal disease that is transmitted in Brazil mainly by the tick Amblyomma sculptumBerlese, which uses capybaras (Hydrochoerus hydrochaerisLinnaeus) as major hosts. In 2015, we captured nine capybaras in a BSF-endemic area of southeastern Brazil. From each capybara, we collected blood sera that were tested through the immunofluorescence assay using Rickettsiaspp. antigens, and A. sculptumticks, processed for isolation of R. rickettsiithrough guinea pig inoculation. All capybaras (100%) were seroreactive to Rickettsiaspp., with highest titers to R. rickettsii. A total of 166 A. sculptumticks were macerated and inoculated into nine guinea pigs, from which only one presented high fever and seroconverted to R. rickettsii. Blood from this febrile animal was inoculated into additional guinea pigs (guinea pig passages), which also became febrile and seroconverted, or when euthanized during the fever period, their internal organs (spleen, lung) were shown to contain R. rickettsiiDNA. The present rickettsial isolate has been maintained cryopreserved as infected guinea pig organs. There was at least one R. rickettsii-infected tick among the 166 macerated ticks, giving a minimal infection rate of 0.6% (1/166). This infection rate is within the range of previous studies, which reported that only 0.05% to at most 1.28% A. sculptumticks were infected by R. rickettsiiin other BSF-endemic areas. These low infection rates support the low incidence of BSF, despite of A. sculptumbeing the most frequent human-biting tick in southeastern Brazil.

High similarity of morphological traits has historically overshadowed the identities and distributions of poultry-associated soft ticks Argas(Persicargas) miniatusand Argas(Persicargas) persicusin America. In order to model the occurrence of both parasites in the continent, in the current study we performed morphological and molecular analyses to identify ticks collected in hen houses from Brazil and northern Chile. Combining these results with literature data, and the examination of Argasallotments deposited in the tick collections “Coleção Nacional de Carrapatos Danilo Gonçalves Saraiva” (Brazil), the “Coleção Acarológica do Instituto Butantan São Paulo” (Brazil), and the “Colección Zoológica de la Academia de Ciencia de Cuba” (Cuba), we present a critical list with the localities where A. (P.) miniatusand A. (P.) persicushave been reported in the American continent. Our results confirmed the presence of A. (P.) miniatusin Brazil and Cuba, and A. (P.) persicusin Chile, which in particular, constitutes the first molecularly confirmed report of the later species for South America. Although A.(P.) miniatusand A. (P.) persicushave been documented in 21 American countries, the identity of some reports must still be considered as uncertain until detailed morphological and/or molecular studies are performed. When contrasted to a Köppen-Geiger climate classification, A. (P.) miniatuspredominantly occurs in equatorial and A. (P.) persicusin arid climates. However, until undetermined reports of both species are correctly identified, any conclusion on their geo-climatological occurrence throughout the American continent would be rather speculative.

Brazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii,is transmitted to humans mainly by the tick Amblyomma sculptumin southeastern Brazil. In most BSF-endemic areas A. sculptumpopulations are sustained chiefly by capybaras (Hydrochoerus hydrochaeris), which are also the host of another tick species, Amblyomma dubitatum,not implicated in R. rickettsiitransmission. Herein, we evaluated the effects of relative humidity (RH), temperature, and water immersion on the successful development of the engorged stages of A. dubitatumand 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. dubitatumhad 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. sculptumwhen ticks were incubated at lower RH values, 65 or 78 %, regardless of summer or winter mean temperatures. These results suggest that A. dubitatumis more adapted to humid habitats and seasonally flooding soils than A. sculptum,whereas this latter species should be more adapted than A. dubitatumto drier habitats. The implications of these results for the spatial distribution of A. dubitatumand A. sculptum, in relation to BSF epidemiology, are discussed.

Recent studies have reported several larvae of an unidentified Amblyommaspecies on passerine birds in Atlantic rainforest fragments in southeastern Brazil. These larvae yielded a unique 16S rRNA haplotype designated as Amblyommasp. haplotype Nazaré, which showed nucleotide identity levels of 91% to Amblyomma parkeriFonseca & Aragão, 1952 and 88% to Amblyomma longirostre(Koch, 1844). Herein, we describe Amblyommasp. haplotype Nazaré as a new species, Amblyomma romarioin. sp. Martins, Luz & Labruna, through a formal description of the male and female adult stages. Amblyomma romarioiis morphologically and genetically most closely related to A. parkeri, A. longirostreand Amblyomma geayiNeumann, 1899. Among males, the rectangular basis capituli and rounded coxa I spurs separates A. romarioifrom 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. romarioicontrasts to the U-shaped genital aperture and coxa I pointed spurs in A. parkeri, A. longirostre,and A. geayi.Larvae of A. romarioihave 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. romarioiis 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. longirostreand A. geayi.The present study increases the Brazilian tick fauna to 74 species.