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Rhipicephalus sanguineussensu stricto (s.s.), the temperate lineage of the brown dog tick, is the most common tick found on dogs from urban areas in Rio Grande do Sul (RS) state, southern Brazil. Chemical treatments against ticks are important to control this pest, but can lead to selection for acaricide resistance. Unfortunately, little is known about acaricide resistance in this tick species in Brazil, although such information is very important to companion animal clinical practice. The objective of this study was to analyze acaricide susceptibility of R. sanguineuss.s. from the metropolitan area of Porto Alegre, RS. Engorged females ticks were collected in ten different locations, from naturally infested dogs or the environment (homes, shelters and kennels). The progenies were used in toxicological larval tests with deltamethrin, fipronil and ivermectin. Mortality data was used to determine the median lethal concentrations (LC50) for each tick population and resistance was characterized based on relative susceptibility of the different tick populations against each acaricide. Seven samples were considered resistant to deltamethrin, with resistance ratios (RR) ranging from 2.32 to 5.67. From five tick populations tested with fipronil, three were considered resistant, with RR varying from 2.56 to 13.83. For ivermectin, resistance ratios were lower, ranging from 1.54 to 2.97. The results reveal a notable variance of susceptibility to deltamethrin, fipronil and ivermectin in the R. sanguineuss.s. populations studied. This study documents for the first time the existence of acaricide-resistant populations of R. sanguineuss.s. in Brazil.

More than seventy tick species have been reported in Brazil. Despite the emergence of tick-borne diseases in Neotropical region, there are still limited data available on tick species parasitizing humans in Brazil. Rio Grande do Sul is the southernmost state of Brazil, comprising the only part of Brazilian territory inside the Pampa biome, as well as the transition between subtropical and temperate zones. Here, we report on human parasitism by ticks in Rio Grande do Sul state between 2004 and 2017. Seventy cases of human parasitism by ticks were recorded, with a total of 81 tick specimens collected. These included 11 tick species belonging to three genera of Ixodidae (hard-ticks), Amblyomma, Haemaphysalisand Rhipicephalus; and one genus of Argasidae, Ornithodoros. The most prevalent tick species associated to cases of human parasitism were Amblyomma parkeri(24%), Rhipicephalus sanguineussensu lato (22%), Amblyomma aureolatum(15%) and Amblyomma ovale(12%). A spatial analysis showed two major hot spots of human parasitism by ticks in Rio Grande do Sul state. The findings of this study highlight the need for permanent monitoring of human parasitism by ticks in order to provide a better understanding of tick and tick-borne disease eco-epidemiology, and the early identification of potential cases of tick-borne diseases, particularly in spotted fever endemic regions.

Rangelia vitaliiis the etiologic agent of canine rangeliosis, a severe piroplasmosis that affects domestic dogs in Brazil, Uruguay and Argentina. While R. vitaliiis one of the most pathogenic tick-borne pathogens for dogs in the world, its tick vector has remained unknown. The present study evaluated the vector competence of Rhipicephalus sanguineussensu lato (both tropical and temperate species), Amblyomma aureolatum, Amblyomma ovale, Amblyomma tigrinum,and Amblyomma sculptumfor R. vitalii.These six tick species were selected for the study because they comprise the main tick species infesting dogs within the distribution area of canine rangeliosis in South America. Acquisition feeding of the above six tick species was performed on domestic dogs showing clinical signs of canine rangeliosis, after being experimentally infected through intravenous inoculation or infestation with R. vitalii-infected ticks. Thereafter, engorged ticks were evaluated for transstadial and transovarial passages of R. vitaliithrough molecular analysis after molting or oviposition and egg hatching. The resultant ticks were evaluated for their competence to transmit R. vitaliito susceptible dogs. Among the six tick species, only A. aureolatumwas able to acquire and perpetuate R. vitaliiby transstadial and transovarial passages, as demonstrated by >5% infection rates of ticks after hatching or molting. When exposed to transmission feeding, only A. aureolatumticks were competent to transmit R. vitaliito dogs, which became severely ill, and the results confirmed by molecular methods and blood smear examination to have acquired rangeliosis. Results of the present study, coupled with epidemiological data, indicate that A. aureolatumis a natural vector of R. vitalii.Our results also indicate that R. vitaliiis the first Piroplasmorida agent to be transovarially transmitted in Amblyommaticks.

•Occurrence of Lyme-like syndrome cases has been increasing in Brazil.•The etiologic agent and the potential vectors are unknown.•Borreliaspp. was investigated in ticks of rodents from Brazilian Pampa.•Borrelia burgdorferisensu lato DNA was detected in Ixodes longiscutatusticks.•It is the first report of Borrelia burgdorferisensu lato in Ixodesticks from Brazil.

•Effect of Metarhizium anisopliaein ticks of field populations has been investigated.•Ticks of field populations show a high variation in susceptibility to M. anisopliae.•There is no correlation between susceptibility to M. anisopliaeand acaricide resistance.

Porcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus disease, a complex multisystem syndrome in domestic pigs. Despite the significant economic losses caused by porcine circovirus disease, the mechanisms of pathogenesis underlying the clinical findings remain largely unclear. As various reports have highlighted the potential key role of vascular lesions in the pathogenesis of porcine circovirus disease, the aim of this work was to investigate effects of PCV2 infection on vascular endothelial cells, focusing on cell viability and expression of adhesion/junction molecules. PCV2 infection reduced endothelial cell viability, while viral infection did not affected the viability of several other classical cell lines. Also, PCV2 infection in endothelial cells displayed a dual/biphasic effect: initially, infection increased ICAM-1 expression, which can favor leukocyte recruitment and emigration to tissues and possibly inducing characteristic porcine circovirus disease inflammatory lesions; then, secondarily, infection caused an increase in zonula occludens 1 tight junction protein (ZO-1) expression, which in turn can result in difficulties for cell traffic across the endothelium and a potential impairment the immune response in peripheral tissues. These virus-induced endothelial changes could directly impact the inflammatory process of porcine circovirus disease and associated vascular/immune system disturbances. Data suggest that, among the wide range of effects induced by PCV2 on the host, endothelial modulation can be a pivotal process which can help to explain PCV2 pathogenesis in some porcine circovirus disease presentations.

Aragão is an endemic tick restricted to the highlands of the state of Rio Grande do Sul, Brazil. This species is very aggressive toward humans, causing fever, great pain and intense inflammatory response at the bite site. It is also very aggressive toward dogs, and tick toxicosis syndrome has been reported in this host. In order to elucidate the biology of this tick, the present study describes its life cycle under laboratory conditions, using guinea pigs as hosts for two generations. In the nonparasitic phase, the ticks were maintained in sand, in an incubator under controlled conditions. The larvae molted to the nymphal stage without feeding, and five nymphal stages (N1, N2, N3, N4 and N5) were observed in both generations. In both generations emergence of adults started from N3 when sex ratio was 0.85:1 (23 males and 27 females) in F1 and 0.63:1 (34 males and 54 females) in F2. For both generations, N4 generated more females, while N5 only produced females. The pre-ecdysis period of the nymphs ranged from 31.1 to 38.6 days. Two gonotrophic cycles were observed, and the first one presented a higher average number of eggs deposited (N=139) than the second (N=73.8). The mean duration of the life cycle (egg to egg) of O. brasiliensiswas 215.4 days for the first generation and 195 days for the second.

The cattle tick, Rhipicephalus microplus, causes severe economic losses to beef and dairy production in several countries. The control of the cattle tick is based mostly on chemical acaricides. Currently, there are reports of tick populations resistant to all six classes of acaricides available on the market. The aim of this work was to evaluate two protocols for the control of the cattle tick, R. microplus, under field conditions. For that, an acaricide rotational-based approach and selective (partial)-based protocols were tested against a multi-resistant tick strain. Eighteen Brangus cattle were divided into three experimental groups: Group 1, a rotational-based approach aiming at six treatments per year (spring–spring period) using four different classes of acaricide (IPV6 protocol); Group 2, a selective (partial) and rotational-based protocol, in which only half of the animals with the highest tick counts were treated (IPV7S protocol); and Group 3 (non-treated). The protocols were able to maintain low tick infestation during the 57 weeks of study. The two experimental groups showed lower tick counts than the non-treated group, but not between them. Weekly efficacy of the experimental protocols reached 95% in Group 1 and 88% in Group 2. Herein, we proposed two protocols of cattle tick control (IPV6 and IPV7S) for use in multi-resistant tick populations in Southern Brazil.

Ornithodoros brasiliensis, also known as the “mouro” tick, is an argasid tick found exclusively in the southern Brazilian highlands. O. brasiliensisparasitism is frequently associated with severe symptoms directly induced by the tick bite, a condition compatible with the definition of tick toxicosis. The objectives of this work include (i) the determination of the distribution of O. brasiliensisin farms located in the tick-endemic region, (ii) the description of the characteristics of O. brasiliensishabitats, (iii) the analysis of risk factors associated with O. brasiliensis, and (iv) the retrospective description of cases of human and animal parasitism by O. brasiliensis. Of the 30 farms included in this study, O. brasiliensiswas identified on 5 farms (frequency 16.7%), in which several ticks found in high density buried in soil were collected. Information regarding the tick habitats and the local population was recorded. The data indicated that O. brasiliensisfeeds on humans, dogs, armadillos (Dasypus hybridus), and possibly skunks (Conepatus chinga). The analysis of risk factors indicated that the presence of house basements with an unpaved (natural soil) floor on farms and insufficient sanitary conditions significantly enhanced the probability of identifying O. brasiliensis. Additionally, we describe retrospectively cases of tick parasitism in 28 humans and 11 dogs including the most common symptoms associated with tick toxicosis. This is the first study concerning O. brasiliensisepidemiology, distribution, and habitat, and the report represents the most comprehensive characterization of Ornithodorosbite-associated toxicosis syndrome.

Amitraz is one of the most used acaricides for the control of ticks of domestic animals, however, extensive use of this active ingredient has favored the development of resistant populations of Rhipicephalus microplusworldwide. The possible mechanisms of metabolic and/or target-site alterations mechanisms of amitraz resistance were investigated in a Brazilian field population of R. microplus(São Gabriel strain). Bioassays with the synergists piperonylbutoxide, triphenylphosphate and diethyl-maleate were used to evaluate the metabolic mechanisms involved. Target-site insensitivity was investigated by amplification and sequencing of a fragment of the octopamine/tyramine (OCT/TYR) receptor gene. Piperonylbutoxide synergism (synergism ratio = 2.8) indicated the participation of the P450 pathway in the detoxification of amitraz. Previously reported single nucleotide polymorphisms that confer amino acid changes in the OCT/TYR receptor, threonine to proline (T8P) and leucine to serine (L22S), were found in the amitraz-resistant strain but not in the susceptible reference strain. The results suggest that amitraz resistance in the studied strain is multi-factorial and may result from cytochrome P450 detoxification and mutations in octopamine receptors.

Ticks are one of the main vectors of pathogens for humans and animals worldwide. However, they harbor non-pathogenic microorganisms that are important for their survival, facilitating both their nutrition and immunity. We investigated the bacterial communities associated with two neotropical tick species of human and veterinary potential health importance from Brazil: Amblyomma aureolatumand Ornithodoros brasiliensis. In A. aureolatum(adult ticks collected from wild canids from Southern Brazil), the predominant bacterial phyla were Proteobacteria (98.68%), Tenericutes (0.70%), Bacteroidetes (0.14%), Actinobacteria (0.13%), and Acidobacteria (0.05%). The predominant genera were Francisella(97.01%), Spiroplasma(0.70%), Wolbachia(0.51%), CandidatusMidichloria (0.25%), and Alkanindiges(0.13%). The predominant phyla in O. brasiliensis(adults, fed and unfed nymphs collected at the environment from Southern Brazil) were Proteobacteria (90.27%), Actinobacteria (7.38%), Firmicutes (0.77%), Bacteroidetes (0.44%), and Planctomycetes (0.22%). The predominant bacterial genera were Coxiella(87.71%), Nocardioides(1.73%), Saccharopolyspora(0.54%), Marmoricola(0.42%), and Staphylococcus(0.40%). Considering the genera with potential importance for human and animal health which can be transmitted by ticks, Coxiellasp. was found in all stages of O. brasiliensis, Francisellasp. in all stages of A. aureolatumand in unfed nymphs of O. brasiliensis,and Rickettsiasp. in females of A. aureolatumfrom Banhado dos Pachecos (BP) in Viamão municipality, Brazil (BP), and in females and unfed nymphs of O. brasiliensis. These results deepen our understanding of the tick-microbiota relationship in Ixodidae and Argasidae, driving new studies with the focus on the manipulation of tick microbiota to prevent outbreaks of tick-borne diseases in South America.

The study of vectors and vector-borne diseases associated with ectoparasites from free-living Neotropical small wild felids is scarce, and the few existing studies on this theme focused on the genus Panthera, Paleartic species or in captive animals. For this reason, the aim of this study was to identify the diversity of ectoparasites and potentially associated Rickettsiaand Bartonellaspecies in free-ranging neotropical wild cats collected in the State of Rio Grande do Sul, southern Brazil. A total of 82 ticks, 10 fleas and 22 mites were collected from 18 Geoffroy's cats (Leopardus geoffroyi), 11 margays (Leopardus wiedii), two southern tiger cats (Leopardus guttulus), two jaguarundis (Herpailurus yagouaroundi), three ocelots (Leopardus pardalis) and two pumas (Puma concolor). We identified four tick species: Rhipicephalus microplusand three species from genus Amblyomma, the most frequent being Amblyomma aureolatum; three flea species corresponding to Ctenocephalides felis, Xenopsylla cheopis, and Pulex irritans; and one mite of genus Eutrombicula.In ectoparasites we found DNA of Rickettsia parkeriand Rickettsia asembonensisin ticks and DNA of Bartonella clarridgeiae, Bartonellasp. and R. asembonensisin fleas. Our results highlight the evidences of vectors and vector-borne agents in wild animals, and their potential wide distribution in the Pampa biome and the southernmost portion of the Atlantic Rainforest in Brazil.