Relapsing Fever Group Borreliae in Human-Biting Soft Ticks, Brazil.

We conducted a molecular survey for Borrelia spp. in Ornithodoros ticks previously reported as biting humans. We collected specimens in natural ecosystems and inside human dwellings in 6 states in Brazil. Phylogenetic analyses unveiled the occurrence of 4 putatively new species of relapsing fever group borreliae.

Distribution modeling of Amblyomma rotundatum and Amblyomma dissimile in Brazil: estimates of environmental suitability.

The number of reports of tick parasitism in amphibians and reptiles has increased over the past few years, including new host and location records for Amblyomma rotundatum and Amblyomma dissimile. However, knowledge of the geographical distribution remains incomplete, and in many regions of Brazil, the presence of these vectors has not been investigated. Several candidate models were built using a correlative maximum entropy approach, and best-fitting models were selected based on statistical significance, predictive ability, and complexity based on current climatic trends and future projected climate changes. Final models showed a good ability to discriminate A. rotundatum and A. dissimile current and future potential distributions. The entire country had higher predicted suitability for A. rotundatum while A. dissimile was mainly restricted to the Amazon and Pantanal biomes. A. rotundatum is a species with enormous potential for dissemination in the next decades, potentially through the legal and illegal transport of reptiles and amphibians. The proposed model is useful for targeting surveillance efforts increasing the efficiency and accuracy of future ecological research and tick management efforts.

Diversity of ticks and detection of Rickettsia amblyommatis infecting ticks on wild birds in anthropogenic landscapes in Bahia state, northeast Brazil.

Birds are important hosts in the maintenance and spread of ticks worldwide, including several species of Amblyomma which harbor rickettsial agents as members of the spotted fever group (SFG). The current survey shows the diversity of tick and rickettsial agents infecting ticks on wild birds from an Atlantic rainforest in the state of Bahia, Brazil. A total of 365 birds were captured, representing two orders, 22 families and 51 species, among which 68 specimens (18.6%) were parasitized. Overall, 132 immature ticks (81 larvae and 51 nymphs) were identified to species level, representing six recognized species of the genus Amblyomma: Amblyomma longirostre (n = 45), Amblyomma nodosum (n = 40), Amblyomma varium (n = 5), Amblyomma parkeri (n = 2), Amblyomma coelebs (n = 3) and Amblyomma calcaratum (n = 1). Amplification by PCR and sequencing of rickettsial genes (gltA and ompA), detected the presence of Rickettsia DNA in 12 (9.1%) of the ticks. Rickettsia amblyommatis was the only agent detected in nine larvae and two nymphs of A. longirostre and one nymph of A. varium with 99-100% similarity.

"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.

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

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

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.

Detection of "Candidatus Rickettsia wissemanii" in ticks parasitizing bats (Mammalia: Chiroptera) in the northern Brazilian Amazon.

A total of 482 bats representing 32 species and two families were captured in the Amazon forests of the Amapá state in northern Brazil. Nineteen Artibeus planirostris bats (3.9 %) were infested with 160 ticks, all identified as Ornithodoros hasei. Three pools of larvae were screened for rickettsial DNA via polymerase chain reaction (PCR) targeting three rickettsial genes: gltA, ompA and htrA. Only one of them yielded an amplicons of the expected size for all three molecular assays. Comparisons of the obtained sequences including a phylogenetic analysis confirmed the occurrence of "Candidatus Rickettsia wissemanii" in Brazil.

Ticks (Acari: Ixodidae) of the state of Amazonas, Brazil.

The tick fauna of Brazil is currently composed by 72 species. The state of Amazonas is the largest of Brazil, with an area of ≈ 19% of the Brazilian land. Besides its vast geographic area, only 19 tick species have been reported for Amazonas. Herein, lots containing ticks from the state of Amazonas were examined in three major tick collections from Brazil. A total of 5933 tick specimens were examined and recorded, comprising 2693 males, 1247 females, 1509 nymphs, and 484 larvae. These ticks were identified into the following 22 species: Amblyomma cajennense sensu lato, Amblyomma calcaratum, Amblyomma coelebs, Amblyomma dissimile, Amblyomma dubitatum, Amblyomma geayi, Amblyomma goeldii, Amblyomma humerale, Amblyomma latepunctatun, Amblyomma longirostre, Amblyomma naponense, Amblyomma oblongoguttatum, Amblyomma ovale, Amblyomma rotundatum, Amblyomma scalpturatum, Amblyomma varium, Dermacentor nitens, Haemaphysalis juxtakochi, Ixodes cf. Ixodes fuscipes, Ixodes luciae, Rhipicephalus microplus, Rhipicephalus sanguineus sensu lato. Ticks were collected from 17 (27.4%) out of the 62 municipalities that currently compose the state of Amazonas. The following four species are reported for the first time in the state of Amazonas: A. coelebs, A. dubitatum, H. juxtakochi, and Ixodes cf. I. fuscipes. The only tick species previously reported for Amazonas and not found in the present study is Amblyomma parvum. This study provides a great expansion of geographical and host records of ticks for the state of Amazonas, which is now considered to have a tick fauna composed by 23 species. It is noteworthy that we report 1391 Amblyomma nymphs that were identified to 13 different species.

Life-cycle of Amblyomma oblongoguttatum (Acari: Ixodidae) under laboratory conditions.

This study evaluated for the first time the life cycle of Amblyomma oblongoguttatum in the laboratory. For this purpose, larvae and nymphs were exposed to Gallus gallus (chicks), Rattus norvegicus (wistar rat), Calomys callosus (vesper mouse), Oryctolagus cuniculus (domestic rabbit), Cavia porcellus (guinea pig), and Didelphis albiventris (white-eared opossum). Nymphs were exposed to G. gallus, C. callosus, C. porcellus, O. cuniculus, R. norvegicus, and Nectomys squamipes (water rat). Adult ticks were exposed to domestic dogs. The life-cycle of A. oblongoguttatum in the laboratory could be completed in an average period of 188 days, considering prefeeding periods of 25 days for each of the parasitic stages. Under laboratory conditions, none of the host species was highly suitable for A. oblongoguttatum larvae, since the recovery rates of engorged larvae were always <15%, or most of the times ≤5%. Similar results were obtained for nymphs, with recovery rates of engorged nymphs always <6%. Our results, coupled with literature data, suggest that small mammals, especially small rodents, do not have an important role in the life-cycle of A. oblongoguttatum under field conditions. Domestic dogs showed to be highly suitable for the adult stage of A. oblongoguttatum, in agreement with literature data that have appointed dogs as important hosts for the adult stage of A. oblongoguttatum in South America.

Ticks infesting bats (Mammalia: Chiroptera) in the Brazilian Pantanal.

Ticks associated with bats have been poorly documented in the Neotropical Zoogeographical Region. In this study, a total of 1028 bats were sampled for tick infestations in the southern portion of the Brazilian Pantanal. A total of 368 ticks, morphologically identified as Ornithodoros hasei (n = 364) and O. mimon (n = 4), were collected from the following bat species: Artibeus planirostris, Platyrrhinus lineatus, Phyllostomus hastatus, Mimon crenulatum and Noctilio albiventris. Morphological identification of O. hasei was confirmed by molecular analysis. Regarding the most abundant bat species, only 40 (6.2%) out of 650 A. planirostris were infested by O. hasei, with a mean intensity of 7.2 ticks per infested bat, or a mean abundance of 0.44 ticks per sampled bat. Noteworthy, one single P. hastatus was infested by 55 O. hasei larvae, in contrast to the 2.5-7.2 range of mean intensity values for the whole study. As a complement to the present study, a total of 8 museum bat specimens (6 Noctilio albiventris and 2 N. leporinus), collected in the northern region of Pantanal, were examined for tick infestations. These bats contained 176 ticks, which were all morphologically identified as O. hasei larvae. Mean intensity of infestation was 22, with a range of 1-46 ticks per infested bat. Our results suggest that A. planirostris might play an important role in the natural life cycle of O. hasei in the Pantanal.

Biology of the non-parasitic phase of the cattle tick Rhipicephalus (Boophilus) microplus in an area of Amazon influence.

BACKGROUND: Rhipicephalus (Boophilus) microplus is the most important tick species affecting cattle in the world. Under field conditions, the non-parasitic phase of R. (B.) microplus is unknown in the Amazon biome, including Brazil. The present study aimed to evaluate the non-parasitic phase of R. (B.) microplus in field (grass plots) and laboratory conditions. METHODS: The study was conducted from September 2020 to April 2022 in an Amazonian region (Maranhão State, Brazil). We evaluated the biological parameters of R. (B.) microplus under laboratory and field conditions. Engorged females were exposed to experimental conditions every 14 days, totaling 20 months of study. The following biological parameters were observed: pre-oviposition period, egg mass incubation period, and maximum larval survival period. RESULTS: Abiotic data (e.g., temperature and humidity) varied little throughout the year. Precipitation was the factor that varied the most throughout the year (dry ~ 30 mm3 and rain 400 mm3), and the parameters of pre-oviposition and pre-hatching are longer during the rainy season. A possible negative effect of the dry season on the percentage of hatched eggs was observed. Larval longevity in the plots of both control and free females was short (mean ~ 50-60 days), below that recorded for larvae under controlled conditions (mean ~ 95 days). CONCLUSIONS: Rhipicephalus (Boophilus) microplus was able to complete its non-parasitic phase by producing host-seeking larvae in the pasture during all months of the study. The results indicate that R. (B.) microplus can complete up to six generations per year in biome Amazon. To our knowledge, this is the highest number of annual generations for R. (B.) microplus in Latin America.

Morphological anomalies in hard ticks (Acari: Ixodidae) from Brazil.

Tick abnormalities have been unusual in nature, and they can be divided into local and general. In the present study, external morphological anomalies were described in 31 individual adult ticks of 15 different species of Ixodidae, which were collected on wild hosts (20 ticks), domestic hosts (7 ticks), and in the environment (4 ticks) in 11 states of Brazil from 1998 to 2022. Among the 31 tick specimens, 14 (45%) were categorized as local anomalies, and 17 (55%) as general anomalies. The ticks were taxonomically identified into 14 species of Amblyomma, and one species of Rhipicephalus. Local anomalies included malformations of scutum/alloscutum, ectromely, leg atrophy, and a third ectopic spiracular plate. General anomalies included opisthosoma duplication, no expansion of dorsal alloscutum in engorged females, and gynandromorphism; the latter is described for 13 tick specimens. Morphological anomalies in Amblyomma aureolatum, Amblyomma brasiliense, Amblyomma humerale and Amblyomma longirostre are reported for the first time. Although the results herein expand the list of anomalous tick species in the Neotropics, future studies should be conducted to clarify the origin of these anomalies.

Records and altitudinal assessment of Amblyomma aureolatum and Amblyomma ovale (Acari: Ixodidae) in the State of Rio de Janeiro, southeast Brazil.

Information on the altitudinal distribution of the hard ticks Amblyomma aureolatum and Amblyomma ovale in Brazil is scarce and mainly limited to occasional records. In this study we report our evaluation of records on the altitudinal distribution of A. aureolatum and A. ovale collected from dogs and humans and directly from the environment (host-questing ticks), based on active or passive procedures. The collections were conducted in rural areas of municipalities in the state of Rio de Janeiro, Brazil between 2013 and 2017. Active procedures consisted of dragging or flagging, visual examination of vegetation and removal of ticks present on the authors' clothing or on infested dogs. Overall, 222 ticks were collected. The altitudes at the collection sites ranged from 98 to 1220 m a.s.l. We noted a significant difference in the altitudinal distribution of A. aureolatum and A. ovale (Mann-Whitney U-test, U = 518.5, P < 0.001). The overlap of these two species occurred at altitudes of between 650 and 900 m a.s.l. The results indicated that the higher the altitude, the greater the probability for the occurrence of A. aureolatum and, conversely, the lower the likelihood for the occurrence of A. ovale. The findings of this study improve currrent knowledge on the bioecology of these tick species and have implications for studies on the epidemiology of spotted fever in Brazil.

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

PURPOSE: Small mammals are important reservoirs of ticks and their pathogens in nature. However, studies reporting these associations are still rare in Brazil. In the present study, we investigated the presence of Rickettsia DNA in ticks parasitizing rodents and marsupials captured in different areas throughout the Atlantic rainforest biome, Bahia, Northeastern (NE), Brazil. METHODS: The study was conducted in five municipalities within of the Atlantic Forest biome, Bahia state, in NE Brazil. Two campaigns were done in each municipality. For host captures Sherman and Tomahawk traps were used, and pitfall traps. After being captured, the hosts were anesthetized and their entire body examined for ticks. When ticks were detected, they were manually removed and stored in eppendorf tubes (1.5 ml) containing absolute PA ethanol for future laboratory analysis (identification of ticks and detection of Rickettsia spp.). RESULTS: A total of 609 mammals were captured. Overall, 208 ticks of the genus Amblyomma and Ixodes were collected: A. ovale, I. loricatus and A. varium. Rickettsia DNA was detected in A. ovale and it was 99-100% of identity to the sequence deposited in GenBank as Rickettsia parkeri strain Atlantica rainforest. CONCLUSION: These results suggest that R. parkeri strain Atlantic rainforest occurs in the region, and A. ovale is likely the vector.

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.

Morphometric Patterns and Blood Biochemistry of Capybaras (Hydrochoerus hydrochaeris) from Human-Modified Landscapes and Natural Landscapes in Brazil.

The capybara, Hydrochoerus hydrochaeris, is the largest extant rodent of the world. To better understand the correlation between size and body mass, and biochemical parameters of capybaras from areas with different degrees of anthropization (i.e., different food supplies), we sampled free-ranging capybaras from areas of natural landscapes (NLs) and human-modified landscapes (HMLs) in Brazil. Analyses of biometrical and biochemical parameters of capybaras showed that animals from HMLs were heavier (higher body mass) than those from NL, a condition possibly related to fat deposit rather than body length, as indicated by Body Condition Index (BCI) analyses. Biochemical parameters indicated higher serum levels of albumin, creatine kinase, cholesterol, fructosamine and total protein among capybaras from HMLs than from NLs; however, when all adult capybaras were analyzed together only cholesterol and triglycerides were positively correlated with body mass. We propose that the biochemical profile differences between HMLs and NLs are related to the obesity condition of capybaras among HMLs. Considering that heavier animals might live longer and reproduce more often, our results could have important implications in the population dynamics of capybaras among HMLs, where this rodent species is frequently represented by overgrowth populations that generate several levels of conflicts with human beings.

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.

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.

Rickettsia rickettsii (Rickettsiales: Rickettsiaceae) Infecting Amblyomma sculptum (Acari: Ixodidae) Ticks and Capybaras in a Brazilian Spotted Fever-Endemic Area of Brazil.

The bacterium Rickettsia rickettsii is the agent of Brazilian spotted fever (BSF), a highly fatal disease that is transmitted in Brazil mainly by the tick Amblyomma sculptum Berlese, which uses capybaras (Hydrochoerus hydrochaeris Linnaeus) 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 Rickettsia spp. antigens, and A. sculptum ticks, processed for isolation of R. rickettsii through guinea pig inoculation. All capybaras (100%) were seroreactive to Rickettsia spp., with highest titers to R. rickettsii. A total of 166 A. sculptum ticks 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. rickettsii DNA. 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. sculptum ticks were infected by R. rickettsii in other BSF-endemic areas. These low infection rates support the low incidence of BSF, despite of A. sculptum being the most frequent human-biting tick in southeastern Brazil.

Habitat selection in natural and human-modified landscapes by capybaras (Hydrochoerus hydrochaeris), an important host for Amblyomma sculptum ticks.

Human activities are changing landscape structure and function globally, affecting wildlife space use, and ultimately increasing human-wildlife conflicts and zoonotic disease spread. Capybaras (Hydrochoerus hydrochaeris) are linked to conflicts in human-modified landscapes (e.g. crop damage, vehicle collision), as well as the spread and amplification of Brazilian spotted fever (BSF), the most human-lethal tick-borne disease in the world. Even though it is essential to understand the link between capybaras, ticks and BSF, many knowledge gaps still exist regarding the effects of human disturbance in capybara space use. Here, we analyzed diurnal and nocturnal habitat selection strategies of capybaras across natural and human-modified landscapes using resource selection functions (RSF). Selection for forested habitats was higher across human-modified landscapes, mainly during day- periods, when compared to natural landscapes. Across natural landscapes, capybaras avoided forests during both day- and night periods. Water was consistently selected across both landscapes, during day- and nighttime. Distance to water was also the most important variable in predicting capybara habitat selection across natural landscapes. Capybaras showed slightly higher preferences for areas near grasses/shrubs across natural landscapes, and distance to grasses/shrubs was the most important variable in predicting capybara habitat selection across human-modified landscapes. Our results demonstrate human-driven variation in habitat selection strategies by capybaras. This behavioral adjustment across human-modified landscapes may be related to increases in A. sculptum density, ultimately affecting BSF.