Records of ticks on humans in Rio Grande do Sul state, Brazil

Perception of Ticks and Tick-Borne Diseases Worldwide

In this comprehensive review study, we addressed the challenge posed by ticks and tick-borne diseases (TBDs) with growing incidence affecting human and animal health worldwide. Data and perspectives were collected from different countries and regions worldwide, including America, Europe, Africa, Asia, and Oceania. The results updated the current situation with ticks and TBD and how it is perceived by society with information bias and gaps. The study reinforces the importance of multidisciplinary and international collaborations to advance in the surveillance, communication and proposed future directions to address these challenges.

Comparison of Seroprevalence and Identification of Risk Factors for Theileria equi in Horses From Vector-Free and Infested Areas in Southern Brazil

The apicomplexan hemoprotozoan Theileria equi is a tick-borne pathogen that causes disease in equids, and together with Babesia caballi, causes equine piroplasmosis (EP). Many ticks are associated with EP around the world, and in South America three species may be related: Dermacentor nitens, Amblyomma sculptum, and Rhipicephalus microplus, as they are commonly found in horses. Among the species cited above, only R. microplus is found in Rio Grande do Sul state, Southern Brazil. In addition, this state has the only area legally free of R. microplus in Brazil. This study aimed to compare the seroprevalence for T. equi on farms located in a tick-free area (23 farms, 215 horses) and a tick-infested (25 farms, 141 horses) adjacent areas, as well as to identify potential risk factors for exposure to T. equi. Blood was collected from 356 horses from both areas, and later an indirect enzyme-linked immunosorbent assay was performed to detect anti-T. equi antibodies. Besides the blood collection, questionnaires and interviews were conducted in an attempt to identify potential risk factors. The R. microplus-free zone had 6% seropositive horses against 70% in the tick-infested zone. Previous observation of ticks on horses of the herd increased four times the odds of a horse to be seropositive for T. equi, and by three times if ticks were observed on cattle which share paddocks with horses on the farm. The results showed a large difference in T. equi seroprevalence between tick-infested and free areas, and also emphasized the relevance of R. microplus in the epidemiology of T. equi. The study also reveals the potential of the establishment of a T. equi-free zone for horse breeding in Southern Brazil.

Canine Parvovirus 2 in Free-Living Wild Mammals from Southern Brazil

Pathogens from domestic canines represent a significant and constant threat to wildlife. This study looked for four common canine pathogens, Babesia vogeli, Ehrlichia canis, Leishmania infantum, and canine parvovirus 2 (CPV-2) in mammals from the Pampa Biome, southern Brazil. Animals killed by vehicular trauma on a road traversing this biome were evaluated over a 1-yr period. Tissues collected from 31 wild mammals and six dogs were further analyzed by specific real-time PCR assays for each pathogen. Babesia vogeli and L. infantum were not detected in any investigated animal. Ehrlichia canis was detected in one dog and CPV-2 in nine animals: four dogs, three white-eared opossums (Didelphis albiventris), one pampas fox (Lycalopex gymnocercus), and one brown rat (Rattus norvegicus). These results demonstrate the occurrence of important carnivore pathogens (E. canis and CPV-2) in domestic dogs and wild mammals from the Pampa Biome in southern Brazil.

Soft and hard ticks (Parasitiformes: Ixodida) on humans: A review of Brazilian biomes and the impact of environmental change

Records of accidental parasitism by ticks in humans from Brazil are scarce, with most being reported by researchers who are parasitized during their research and by professionals who work with animals. In order to compile these records, an extensive literature review was carried out. Our revision includes studies published between 1909 and 2022, including nine species of the Argasidae family and 32 species of the Ixodidae family that were reported biting humans in the six biomes of the Brazilian territory. The species with the highest number of records of human parasitism was Amblyomma sculptum, followed by Amblyomma coelebs, Amblyomma cajennense sensu stricto, and Amblyomma brasiliense. The Atlantic Forest was the most frequent biome where human parasitism occurred, probably due to the greater number of inhabitants, universities, and researchers in the region; however, this does not mean that this biome is more conducive to the development of ticks and their parasitism in humans. In addition to Amblyomma ovale, a vector of Rickettsia parkeri in the country, two of the main species that act as vectors of Rickettsia rickettsii, A. sculptum, and Amblyomma aureolatum, have been reported, which is quite worrying considering that the wide distribution of the species and life stages most frequently mentioned in parasitism (i.e., nymphs and adults) are the ones that favour pathogen transmission. This research provides a significant contribution to the knowledge of tick species associated with human parasitism in Brazil; however, due to environmental change potentiated by deforestation and fires, it is expected that there will be a geographic expansion of some tick species and the pathogens that use them as a vector and an increase in human parasitism.

Historical overview and update on relapsing fever group Borrelia in Latin America

Relapsing fever group Borrelia (RFGB) are motile spirochetes transmitted to mammalian or avian hosts through the bite of hematophagous arthropods, such as soft ticks (Argasidae), hard ticks (Ixodidae) and the human clothing lice. RFGB can infect pets such as dogs and cats, as well as birds, cattle and humans. Borrelia recurrentis, B. anserina and B. theileri are considered to have worldwide distribution, affecting humans, domestic birds and ruminants, respectively. Borrelia spp. associated with soft ticks are transmitted mainly by Ornithodoros ticks and thrive in endemic foci in tropical and subtropical latitudes. Nowadays, human cases of soft tick-borne relapsing fever remain neglected diseases in several countries, and the impact these spirochetes have on the health of wild and domestic animals is largely understudied. Human infection with RFGB is difficult to diagnose, given the lack of distinguishing clinical features (undifferentiated febrile illness). Clinically, soft tick or louse-borne relapsing fever is often confused with other etiologies, such as malaria, typhoid or dengue. In Latin America, during the first half of the twentieth century historical documents elaborated by enlightened physicians were seminal, and resulted in the identification of RFGB and their associated vectors in countries such as Mexico, Panama, Colombia, Venezuela, Peru and Argentina. Almost 80 years later, research on relapsing fever spirochetes is emerging once again in Latin America, with molecular characterizations and isolations of novel RFGB members in Panama, Bolivia, Brazil and Chile. In this review we summarize historical aspects of RFGB in Latin America and provide an update on the current scenario regarding these pathogens in the region. To accomplish this, we conducted an exhaustive search of all the published literature for the region, including old medical theses deposited in libraries of medical academies. RFGB were once common pathogens in Latin America, and although unnoticed for many years, they are currently the focus of interest among the scientific community. A One Health perspective should be adopted to tackle the diseases caused by RFGB, since these spirochetes have never disappeared and the maladies they cause may be confused with etiologies with similar symptoms that prevail in the region.

Diversity of tick species (Acari: Ixodidae) in military training areas in Southeastern Brazil

Tick-borne pathogens belong to one of the two main groups of occupational biohazards, and occupational exposure to such agents puts soldiers at risk of zoonotic infections, such as those caused by rickettsiae. There are few studies on acarological fauna and occupational risk in military areas in Brazil. Thus, the present study aimed to analyze the diversity of ticks present in the military training areas of municipalities in the Southeast Region of Brazil. The ticks were collected from the selected areas using the dragging and flagging techniques as well as by visual detection on the operators' clothing, and environmental information was also recorded. A total of ten species were collected from the 66 surveyed areas, belonging to five genera and nine species: Amblyomma sculptum, Amblyomma dubitatum, Amblyomma brasiliense, Amblyomma longirostre, Amblyomma aureolatum, Dermacentor nitens, Rhipicephalus spp., Ixodes spp. and Haemaphysalis spp. The frequent presence of tick species in military training areas along with traces and sightings of wild animals, most commonly capybaras (Hydrochoerus hydrochaeris), in most of the studied areas, indicates high levels of exposure of the military to tick vectors of spotted fever group rickettsiae and the possible occurrence of infections among the troops.

Ticks on humans in an Atlantic rainforest preserved ecosystem in Brazil: Species, life stages, attachment sites, and temporal pattern of infestation

We herein describe exposure and tick attachment to researchers and field staff within the greatest preserved inland Atlantic rainforest, located in Brazil, over a non-consecutive period of five years. Overall, 433 ticks from five species were collected, Amblyomma coelebs (n = 281), Amblyomma brasiliense (n = 79), Amblyomma incisum (n = 43), Amblyomma ovale (n = 4), Haemaphysalis juxtakochi (n = 4). Clusters of larvae belonged to the genus Amblyomma (n = 21) and Haemaphysalis (n = 1). Both Haemaphysalis and Amblyomma species were observed crawling on humans but only ticks from the latter genus were found attached. Most recovered ticks (59%) were found attached and, whereas A. brasiliense was the main host-seeking tick species in the forest, A. coelebs nymphs were the ones that overwhelmingly attached to humans (70% of all attachments). At the same time only 0.4% of human bites were of A. ovale, the Rickettsia parkeri strain Atlantic rainforest vector tick in Brazil. Tick attachment sites were recorded for 132 ticks and lower/upper limbs and the trunk were more parasitized than the head/neck. Tick bites were recorded throughout the year; while larvae did not show an evident seasonal pattern, nymphs attached to humans mainly in autumn and winter and the few adult bites were recorded in spring. Our results highlighted A. coelebs nymphs as major human-biters and evidenced the necessity of studies that discern human tick bites that occur after exposure to host-seeking ticks from those that occur after tick displacement from hosts that carry ticks to human dwellings.

Amblyomma aureolatum Genetic Diversity and Population Dynamics Are Not Related to Spotted Fever Epidemiological Scenarios in Brazil

Regional differences in tick-borne disease epidemiology may be related to biological variations between vector populations. Amblyomma aureolatum (Ixodida: Ixodidae), a neotropical tick, is known from several regions in Brazil. However, only in the metropolitan area of São Paulo (SP) state are there studies that establish its role as a vector of a pathogenic rickettsia (Rickettsia rickettsii). The aim of the study was to analyze the genetic diversity, population dynamics, and rickettsia infection in A. aureolatum populations from different spotted fever scenarios in Brazil. Samples were subjected to DNA extraction, amplification and sequencing of 12S rDNA, cytochrome oxidase subunit II and D-loop mitochondrial markers for tick population analyses, and gltA, htrA, ompA, and ompB genes for rickettsia researches. Of the 7–17 tick haplotypes identified, 5–13 were exclusive to each population and 2–12 for each epidemiological scenario, as well as three haplotypes shared by all populations. Amblyomma aureolatum populations are expanding, and do not appear to be genetically structured vis-a-vis the different epidemiological scenarios studied. Rickettsia bellii (in SP) and Rickettsia felis (in Santa Catarina) were identified as infecting A. aureolatum. No relationship between tick haplotypes and rickettsia types were observed.

Efficacy of collars with allomones on dogs to control Rhipicephalus sanguineus sensu lato infestations under field conditions

Benzaldehyde and 2-hexanone are allomones produced by beagle dogs that reduce infestation by Rhipicephalus sanguineus sensu lato on these animals and on susceptible dogs which artificially release these repellents. These observations were obtained in previous laboratory tests or artificial infestations of susceptible dogs under controlled conditions. Here we evaluated the efficacy of collars delivering these repellents for suppressing the loads of R. sanguineus s.l. on naturally infested mixed-breed dogs under field conditions. Thirty dogs naturally infested with R. sanguineus s.l. were separated into two groups with 15 dogs each. The dogs from the treatment group received the collars with slow-release formulations of the allomones, and the dogs from the control group received collars without such compounds. Collar effectiveness tests were carried out over 30 days. All ticks found were removed from each dog, identified, and counted every collection day. The density of the different life stages of R. sanguineus s.l. varied greatly between groups and across evaluation times. Adult ticks were the stage most abundant and prevalent on infested dogs. The counts for larvae, nymphs and adults were similar between the control and the treatment groups within each tick collection day. Conversely, when we considered the total number of ticks over 30 days and gathered all life stages collected in the same animal, the dogs from the control group had significantly higher loads (35.3 ± 4.27) of ticks than the dogs from the treatment group (21.8 ± 2.96) (P < 0.01). In addition, the efficacy of treatment with repellent collars was high for adult ticks (30.8%) but was extremely low for reducing larval or nymphal infestation (0 or 2.6%, respectively). The present study demonstrates, for the first time, the efficacy of these volatile compounds on naturally infested dogs under field conditions. The development of a technologically enhanced device for slow release of the allomones tested here can be an advantageous alternative for reducing R. sanguineus s.l. infestation on dogs in residential environments.

Didelphis spp. opossums and their parasites in the Americas: A One Health perspective

Medium sized opossums (Didelphis spp.) are among the most fascinating mammals of the Americas, playing important ecological roles (e.g., dispersal of seeds and control of insect populations) in the environment they inhabit. Nevertheless, as synanthropic animals, they are well adapted to human dwellings, occupying shelters within the cities, peripheral areas, and rural settings. These marsupials can harbor numerous pathogens, which may affect people, pets, and livestock. Among those, some protozoa (e.g., Leishmania infantum, Trypanosoma cruzi, Toxoplasma gondii), helminths (e.g., Ancylostoma caninum, Trichinella spiralis, Alaria marcianae, Paragonimus spp.) and arthropods (e.g., ticks, fleas) present substantial public health and veterinary importance, due to their capacity to cause disease in humans, domestic animals, and wildlife. Here, we reviewed the role played by opossums on the spreading of zoonotic parasites, vectors, and vector-borne pathogens, highlighting the risks of pathogens transmission due to the direct and indirect interaction of humans and domestic animals with Didelphis spp. in the Americas.

Ticks, mites, fleas, and vector-borne pathogens in free-ranging neotropical wild felids from southern Brazil

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 Rickettsia and Bartonella species 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 microplus and 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 parkeri and Rickettsia asembonensis in ticks and DNA of Bartonella clarridgeiae, Bartonella sp. and R. asembonensis in 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.

Human Parasitism by Amblyomma parkeri Ticks Infected with Candidatus Rickettsia paranaensis, Brazil

Spotted fever is the main rickettsial disease in Brazil. We report 12 cases of human parasitism by Amblyomma parkeri in the Atlantic rainforest, an area of Brazil to which spotted fever is endemic. Nine of the ticks were infected with Candidatus Rickettsia paranaensis.

Spotted fever group rickettsial infection in dogs and their ticks from domestic-wildlife interface areas in southeastern Brazil

Rickettsia rickettsii is the causative agent of Brazilian spotted fever (BSF), for which humans and dogs are both susceptible. Dogs are sentinels in serological surveys, however, canine disease is rarely reported. Therefore, we aimed to evaluate natural infection by spotted fever group (SFG) Rickettsia spp. in dogs and ticks collected from domiciles close to forest fragments, featuring domestic-wildlife interface areas. Samples from 115 dogs and 135 ixodids were assessed by polymerase chain reactions (PCR) targeting the gltA gene for Rickettsia spp. and the ompA gene for the SFG rickettsial species. One dog (0.87%; 1/115) was positive for R. rickettsii. This dog presented nonspecific laboratory and clinical abnormalities (thrombocytopenia, hyperproteinemia, lymph node enlargement, emaciation, anorexia, and lethargy). Rickettsia parkeri was identified in 2.96% (4/135) of the ticks (Amblyomma sculptum, A. aureolatum, and Rhipicephalus sanguineus). This study confirmed the presence of SFG bacteria in non-endemic and preserved locations, where domestic and wild populations interact. We reinforce the fact that the dog is susceptible to natural R. rickettsii infection. Although this is a rare finding, preventive measures should be taken against BSF in the studied areas. Finally, R. parkeri infection is possibly being demonstrated in A. sculptum for the first time.

Clinical Findings Associated with Ornithodoros brasiliensis Tick Parasitism in Travelers, Southern Brazil

We report a series of clinical cases associated with parasitism by the Ornithodoros brasiliensis tick in a group of travelers in the Caxias do Sul municipality, Southern Brazil. These cases draw attention to underdiagnosed noninfectious syndromes caused by ticks with restricted local distributions.

Efficacy of orally administered fluralaner in dogs against laboratory challenge with Haemaphysalis longicornis ticks

Background

Haemaphysalis longicornis ticks represent an ectoparasitic health threat to dogs. This study evaluated the immediate and persistent efficacy of orally administered fluralaner for control of this tick.

Methods

Twenty-four dogs were sorted into 4 groups based on their tick carrying capacity measured in a preliminary challenge. Two days before treatment, dogs were challenged with Haemaphysalis longicornis and then at the time of treatment dogs received with oral fluralaner at 10, 25 or 50 mg/kg respectively to 3 of the groups, while the remaining group was sham treated. Ticks were counted and categorized on all dogs 2 days after treatment (4 days after challenge). Tick challenges were repeated at 28, 56, 84 and 112 days following treatment with tick counts 48 hours following each challenge. Tick control efficacy was evaluated by comparing the mean (geometric) total live attached and dead engorged ticks on each fluralaner treated group with the sham treated dogs.

Results

Oral fluralaner is highly acaricidal for H. longicornis that feed on treated dogs. The mean efficacy rate in dogs treated with fluralaner at the commercial dose range of 25 to 50 mg/kg was greater than 90% at 114 days after treatment, whereas efficacy at this time in dogs treated at 10 mg/kg was 79%.

Conclusions

Fluralaner administered orally to dogs within the commercial dose range at 25 to 50 mg/kg is effective for up to 114 days against laboratory challenge with H. longicornis ticks.

Molecular survey of Rickettsia spp. in the Neotropical deer tick Haemaphysalis juxtakochi from Brazilian Pampa

Spotted fever (SF) is a tick-borne disease associated with Rickettsia spp.. In the Pampa biome, Southern Brazil, cases of SF seem to be strongly linked with the practice of hunting wild animals. An investigation of rickettsiae in tick species found on wild animals could provide more information regarding the rickettsiosis enzootic cycle. The aim of this study is to describe the results of a molecular survey of Rickettsia spp. in the Neotropical deer tick, Haemaphysalis juxtakochi Cooley, 1946 (Acari: Ixodidae), from the Brazilian Pampa. Ticks were obtained from 14 road-killed gray brocket deer, Mazama gouazoubira (Artiodactyla: Cervidae), found in nine different municipalities of Rio Grande do Sul state, Southern Brazil. Ticks were processed individually to obtain genomic DNA, and then Rickettsia spp. was investigated using a set of PCR reactions that amplified the rickettsial fragments of the gltA, ompA, and htrA genes. Of the 24 tick samples tested, DNA of Rickettsia parkeri sensu stricto (s.s.) was found in 11 H. juxtakochi specimens collected in two different areas of the Brazilian Pampa. This is the first report of R. parkeri s.s. (the main agent associated with SF in the Uruguayan, Argentinian, and Brazilian Pampa) in H. juxtakochi ticks. These findings indicate that R. parkeri s.s. may be much more common and widely distributed in the Pampa biome than previously assumed. Moreover, H. juxtakochi ticks and gray brocket deer could participate in the potential spillover of R. parkeri s.s. from endemic to non-endemic areas in the South American Pampa.