Rickettsiae-infected ticks in an endemic area of spotted fever in the State of Minas Gerais, Brazil

Ixodid diversity and detection of spotted fever group Rickettsia spp. in ticks collected on birds in the Brazilian Atlantic Forest

The Brazilian Atlantic Forest helds one of the most diverse and unique avifauna in the world. Many vertebrate species are reservoirs of tick-borne pathogens, and birds are an important group among them due to their mobility which facilitates the dispersion of ticks and the infectious agents they carry. This study brings data on the tick diversity parasitizing birds and the molecular detection of Rickettsia spp. in these arthropods. Birds (n = 773) were captured, identified, and banded at Mata do Paraíso Research, Training, and Environmental Education Center located in Viçosa, Minas Gerais, Brazil. Birds were checked for the presence of ticks, which were individually collected, identified, and molecularly processed through Polymerase Chain Reaction (PCR) for the detection of Rickettsia spp. A total of 130 individuals were infested by ticks, and 479 tick specimens were collected, showing a seasonal distribution of the life stages throughout the year. Ticks were identified as Amblyomma longirostre (59/479); Amblyomma calcaratum (20/479); Amblyomma varium (3/479); Amblyomma sculptum (2/479) and Amblyomma spp. larvae (395/479). Seasonal distribution of the life stages of ticks was observed along the year and significant negative correlations were found between temperature and collected ticks and temperature and infested birds. From the evaluated samples of ticks, 25.44% (n= 43/169) scored positive for Rickettsia spp., and sequence analysis indicated high nucleotide identity with Rickettsia rhipicephali, R. massiliae, R. africae and R. honei marmionii. The potential for dispersal of ticks by birds added to the aggressiveness of species of the genus Amblyomma and the zoonotic potential of some species of Rickettsia are quite worrying when we consider that the study area is widely attended by students, researchers, people from the city and neighboring municipalities.

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.

Vector competence of Amblyomma americanum (Acari: Ixodidae) for Rickettsia rickettsii

Rickettsia rickettsii - the etiologic agent of Rocky Mountain spotted fever (RMSF) - is widely spread across the Americas. In the US, Dermacentor spp. ticks are identified as primary vectors of R. rickettsii and Rhipicephalus sanguineus s.l. has been implicated in transmission of this pathogen in several locations in the Southwest. Conversely, ticks of the genus Amblyomma are recognized vectors of RMSF in Central and South America, but not in the US. A. americanum is one of the most aggressive human-biting ticks in the US, whose geographical range overlaps with that of reported RMSF cases. Despite sporadic findings of R. rickettsii DNA in field-collected A. americanum and circumstantial association of this species with human RMSF cases, its vector competence for R. rickettsii has not been appropriately studied. Therefore, we assessed the ability of A. americanum to acquire and transmit two geographically distant isolates of R. rickettsii. The Di-6 isolate of R. rickettsii used in this study originated in Virginia and the AZ-3 isolate originated in Arizona. Under laboratory conditions, A. americanum demonstrated vector competence for both isolates, although the efficiency of acquisition and transovarial transmission was higher for Di-6 than for AZ-3 isolate. Uninfected larvae acquired the pathogen from systemically infected guinea pigs, as well as while feeding side by side with Rickettsia-infected ticks on non-rickettsiemic hosts. Once acquired, R. rickettsii was successfully maintained through the tick molting process and transmitted to susceptible animals during subsequent feedings. Guinea pigs and dogs infested with infected A. americanum developed fever, scrotal edema and dermatitis or macular rash. R. rickettsii DNA was identified in animal blood, skin, and internal organs. The prevalence of infection within tick cohorts gradually increased due to side-by-side feeding of infected and uninfected individuals from 33 to 49% in freshly molted nymphs to 71-98% in engorged females. Moreover, R. rickettsii was transmitted transovarially by approximately 28% and 14% of females infected with Di-6 and AZ-3 isolates, respectively. Hence, A. americanum is capable of acquiring, maintaining and transmitting R. rickettsii isolates originating from two different geographical regions of the US, at least under laboratory conditions. Its role in ecology and epidemiology of RMSF in the US deserves further investigation.

Rhipicephalus sanguineus (ACARI: IXODIDAE) BITING A HUMAN BEING IN PORTO ALEGRE CITY, RIO GRANDE DO SUL, BRAZIL

We report the finding of a female brown dog tick, Rhipicephalus sanguineus (Acari: Ixodidae) on the scalp of a male patient inPorto Alegre, Rio Grande do Sul, Brazil. Human parasitism by this tick is rare and has seldomly been reported in the literature, despite its recognized importance since it can act as a vector of Rickettsia rickettsii, the agent of spotted fever.

Rickettsia in synanthropic and domestic animals and their hosts from two areas of low endemicity for Brazilian spotted fever in the eastern region of Minas Gerais, Brazil

The aim of this study was to understand the current epidemiology of rickettsial diseases in two rickettsial-endemic regions in Brazil. In the municipalities of Pingo D'Agua and Santa Cruz do Escalvado, among serum samples obtained from horses and dogs, reactivity by immunofluorescent assay against spotted fever group rickettsiae was verified. In some serum samples from opossums (Didelphis aurita) captured in Santa Cruz do Escalvado, serologic response against rickettsiae was also verified. Polymerase chain reaction identified rickettsiae only in ticks and fleas obtained in Santa Cruz do Escalvado. Rickettsiae in samples had 100% sequence homology with Rickettsia felis. These results highlight the importance of marsupials in maintenance of the sylvatic cycle of rickettsial disease and potential integration with the domestic cycle. Our data also support the importance of horses and dogs as sentinels in monitoring circulation of rickettsiae in an urban area.

Occurrence of ticks (Acari: Ixodidae) on human hosts, in three municipalities in the State of Pará, Brazil

Assuming the existence of tick parasitism in humans in the State of Pará, an aggregate observational study was developed along a transversal line in three cities of the State, during two years. Interviews and examinations of 2,160 townspeople and tourists were carried out, without discrimination of ethnic, sex, age, or social status, and classified for effects analyzed for four bands of age, six types of activities in the society, and two sexes. Larvae, nymphs, and adults of ticks had been identified with cases of parasitism involving six species, of the genus Amblyomma, the genus Ixodes, Rhipicephalus sanguineus, Anocentor nitens, and Ornithodorus talaje (the first case registered in Pará), infecting human beings. Adults and agricultural workers were most frequently attacked, followed by students. A. cajennense and R. sanguineus are the species most frequent in the parasitism affecting humans, and A. cajennense is the dominant species. The statistical prevalence was largest in Cachoeira do Arari, Ilha do Marajó. In Santarém the greatest average intensity of parasitism was for R. sanguineus, and in the other locations it wasfor A. cajennense. Agricultural workers faced the greatest risk from parasitism, and to place in practice elementary measures of prevention would reduce by 25% the number of cases.

Ixodiasis disclosed by epiluminescence microscopy without skin contact

We describe the case of a 48-year-old healthy man who sought for medical help in our clinic with multiple pruriginous erythematous papules after a 2-day trip to "Serra da Mantiqueira". (Mantiqueira Mountain). A meticulous physical exam with a portable epiluminescence microscopy showed several ticks on a larval form on the skin of the patient.

Detection and identification of rickettsial agents in ticks from domestic mammals in eastern Panama

Several outbreaks of Rocky Mountain spotted fever have occurred in recent years in Colombian communities close to the border with Panama. However, little is known about rickettsiae and rickettsial diseases in eastern Panamanian provinces, the Darien Province and the Kuna Yala, located north of the endemic area in Colombia. In 2007, 289 ticks were collected in several towns from dogs, horses, mules, cows, and pigs. DNA was extracted from 124 Dermacentor nitens, 64 Rhipicephalus sanguineus, 43 Amblyomma ovale, 35 A. cajennense, 10 Boophilus microplus, 4 A. oblongoguttatum, and 9 A. cajennense nymphs. SYBR-Green polymerase chain reaction assays targeting a fragment of the OmpA and 16S rRNA genes were used for detection of DNA of the spotted fever group rickettsiae (SFGR) and Anaplasmataceae (Anaplasma and Ehrlichia), respectively. In total, 37.4% ticks were positive for SFGR, including 20.3% R. sanguineus, 27.9% A. ovale, 25.8% D. nitens, 50% B. microplus, 50% A. oblongoguttatum, and 100% A. cajennense. The presence of Rickettsia amblyommii DNA was confirmed by sequencing in A. cajennense, A. oblongoguttatum, A. ovale, B. microplus, and R. sanguineus. DNA of R. rickettsii was only detected in one D. nitens collected from a horse in Santa Fe, Darien Province. Prevalence of Anaplasmataceae varied from 6.3% in R. sanguineus to 26.5% in A. cajennense. DNA of Ehrlichia chaffensis was found in three D. nitens and three A. cajennense from horses. This is the first study providing molecular characterization and prevalence information on SFGR in ticks from these areas and thus will be helpful for future evaluations of the risk of rickettsial diseases for individuals living in this region.

First identification of natural infection of Rickettsia rickettsii in the Rhipicephalus sanguineus tick, in the State of Rio de Janeiro

The Brazilian Spotted Fever (BSF) is a zoonotic disease caused by Rickettsia rickettsii and transmitted by ticks of the genus Amblyomma, more frequently, Amblyomma cajennense. The aim of this paper was to report the first molecular detection of R. rickettsii on R. sanguineus naturally infected in Rio de Janeiro, Brazil. Ticks were collected from dogs in a rural region of Resende municipality, Rio de Janeiro State, Brazil (22º30'9.46"S, 44º42'44.29"WO), where occurred five human cases of BSF in 2006. The ticks were identified under a stereoscopic microscope and separated in pools by stages, species and sex. DNA extraction was carried out using QIAamp DNA Mini Kit (QIAGEN®). The DNA was submitted to PCR amplification using 04 set of primers: Rr190.70p/Rr190.602n (OmpA, 532bp), BG1-21/BG2-20 (OmpB, 650bp), Tz15/Tz16 (17 kDa protein-encoding gene, 246bp) and RpCS.877p/RpCS.1258n (gltA, 381bp). PCR products were separated by electrophoresis on 1% agarose gels and visualized under ultraviolet light with ethidium bromide. PCR products of the expected sizes were purified by QIAquick® and sequenced by ABI PRISM®. The generated nucleotide sequences were edited with using Bioedit® software and compared with the corresponding homologous sequences available through GenBank, using Discontiguous Mega Blast (http://www.ncbi.nlm.nih.gov). It was confirmed R. rickettsii by sequencing of the material (GenBank FJ356230). The molecular characterization of R. rickettsii in the tick R. sanguineus emphasizes the role of dogs as carriers of ticks from the environment to home. Moreover, this result suggests that there is a considerable chance for active participation of R. sanguineus as one of tick species in the transmission of R. ricketsii to human being in the Brazilian territory.

Rhipicephalus sanguineus (Acari: Ixodidae), the brown dog tick, parasitizing humans in Brazil

The objective of this paper is to describe four cases of human parasitism by Rhipicephalus sanguineus (Latrielle) in Brazil. During an investigation regarding the species of ectoparasites of domestic dogs from the metropolitan region of Recife, Pernambuco state, four dog owners were found to be parasitized by ticks. The ticks were collected from these individuals and their dogs. All the ticks were identified as Rhipicephalus sanguineus . These are, to our knowledge, the first four cases of human parasitism by this tick species in Brazil. The possible implications of this finding are discussed here.

Ticks (Ixodidae) on humans in South America

Twenty eight species of Ixodidae have been found on man in South America (21 Amblyomma, 1 Boophilus, 2 Dermacentor, 2 Haemaphysalis, 1 Ixodes and 1 Rhipicephalus species). Most of them are rarely found on man. However, three species frequently parasitize humans in restricted areas of Argentina (A. neumanni reported from 46 localities), Uruguay (A. triste from 21 sites) and Argentina-Brazil (A. parvum from 27 localities). The most widespread ticks are A. cajennense (134 localities in Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela), A. ovale (37 localities in Argentina, Brazil, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela) and A. oblongoguttatum (28 sites in Brazil, Colombia, French Guiana, Guyana, Suriname and Venezuela). Amblyomma aureolatum (18 localities in Argentina, Brazil, French Guiana and Paraguay), A. cajennense, and A. triste are vectors of rickettsioses to man in South America. A better understanding of the respective roles of these and other tick species in transmitting pathogens to humans will require further local investigations. Amblyomma ticks should be the main subjects of these studies followed by species of Boophilus, Dermacentor, Haemaphysalis and Rhipicephalus species. In contrast with North America, Europe and Asia, ticks of the genus Ixodes do not appear to be major players in transmitting diseases to human. Indeed, there is only one record of an Ixodes collected while feeding on man for all South America.

Seasonal dynamics of the Cayenne tick, Amblyomma cajennense on horses in Brazil

The population dynamics of all stages of the Cayenne tick, Amblyomma cajennense (Fabricius) (Acari: Ixodidae) on horses was evaluated over a period of 2 years in the district of Pedro Leopoldo, State of Minas Gerais, Brazil. Every 14 days, the left side of 20 horses was brushed for collection of immature stages; counts of adults were also undertaken. Infestation by larvae was detected from April to August, whereas nymphs were observed from June to October. Infestation by adults was detected throughout the year, and the highest population density occurred from September to March. The number of males was always higher than the number of females, but with considerable reduction in the male : female ratio between April and July. It was observed that 25% of the horses carried 41% of the infesting ticks, and 20% carried only 10% of the ticks during the entire period of the study.

Ecological analysis of acari recovered from coprolites from archaeological site of northeast Brazil

Coprolite samples of human and animal origin from the excavations performed at the archaeological site of Furna do Estrago, at Brejo da Madre de Deus in the state of Pernambuco, Brazil and sent to the Paleoparasitology Laboratory at Escola Nacional de Saúde Pública-Fiocruz, Rio de Janeiro, were analyzed for mites. After rehydratation and sedimentation of the coprolites, the alimentary contents and the sediments were examined and the mites collected and prepared in definitive whole mounts, using Hoyer's medium. Mites of the following suborders and orders were recovered: suborder Acaridia; order Gamasida; order Ixodida with the familiy Ixodidae (Ixodes sp. and Amblyomma sp. larvae, scutum, idiosoma, gnathosoma); order Oribatida (Aphelacarus sp., Apolohmannia sp., Eophypochthonius sp., Cosmochthonius sp., Pterobates sp., Poronoticae with pteromorphae not auriculate); order Astigmata with the families Atopomelidae (Chirodiscoides caviae), Anoetidae hypopus, Acaridae (Suidasia pontifica), Glycyphagidae (Blomia tropicalis), Pyroglyphidae (Hirstia passericola); order Actinedida with the family Tarsonemidae (Iponemus radiatae). The present work discusses the possibility of the preservation of the mite groups found up to the present day. We also discuss their relationship with the environment and their importance to present populations.

Amblyomma aureolatum (Pallas, 1772) and Amblyomma ovale Koch, 1844 (Acari: Ixodidae): hosts, distribution and 16S rDNA sequences

DNA sequences of Amblyomma aureolatum (Pallas, 1772) and Amblyomma ovale Koch, 1844 were obtained to determine genetic differences between these tick species. Collections of these species are discussed in relation to distribution and hosts. Seven ticks collections (four from Brazil, one from Argentina, one from Uruguay and one from USA) house a total of 1272 A. aureolatum (224 males, 251 females, 223 nymphs and 574 larvae) and 1164 A. ovale (535 males, 556 females, 66 nymphs and 7 larvae). The length of the sequenced mitochondrial 16S rRNA gene fragment for A. aureolatum was 370bp and for A. ovale was 373bp. The DNA sequence analysis showed a 13.1% difference between the two species. Apart from one male A. ovale found on a toad, all adult ticks were found on mammals. The majority of adult specimens of both tick species were removed from Carnivora (96.1 and 84.3% of A. aureolatum and A. ovale, respectively), especially from dogs (53.1% of A. aureolatum, and 46.4% of A. ovale). Collections on wild Canidae were higher for A. aureolatum (23.3%) than for A. ovale (7.1%). On the other hand, collections of A. ovale adults on wild Felidae were higher (18.3%) than findings of A. aureolatum (9.2%). The contribution of other mammalian orders as hosts for adults of A. aureolatum and A. ovale was irrelevant, with the exception of Perissodactyla because Tapiridae contributed with 13.0% of the total number of A. ovale adults. Adults of both tick species have been found occasionally on domestic hosts (apart of the dog) and humans. Most immature stages of A. aureolatum were found on Passeriformes birds, while rodents and carnivores were the most common hosts for nymphs and larvae of A. ovale. A. aureolatum has been found restricted to the Neotropical region, covering the eastern area of South America from Uruguay to Surinam, including northeastern Argentina, eastern Paraguay, southeastern Brazil and French Guiana. A. ovale showed a distribution that covers the Neotropical region from central-northern Argentina throughout the Neotropics into the Nearctic region of Mexico with a few records from the USA, also with collection sites in Paraguay, Bolivia, most Brazilian states, Peru, Ecuador, French Guiana, Surinam, Guyana, Trinidad & Tobago, Venezuela, Colombia, Panama, Costa Rica, Nicaragua, Belize, Guatemala and several states of Mexico.

Horse resistance to natural infestations of Anocentor nitens and Amblyomma cajennense (Acari: Ixodidae)

The objective of this study was to investigate some aspects of horse resistance to natural infestations of Anocentor nitens and Amblyomma cajennense over a 2-year period. Free-living stages of A. nitens were used to evaluate the influence of season of the year on horse resistance. Every 2 weeks, 10 selected engorged females, weighing 150-329 mg, were removed from naturally infested horses and were individually placed into glass tubes closed with a cotton stopper, and maintained in an incubator. The biological parameters evaluated varied according to the season of the year, i.e., reproductive efficiency, maximum larval survival (MLS) and egg-hatching rates were significantly lower in spring/summer than in fall/winter. At 14-day intervals, females of A. nitens and A. cajennense were counted on each side of the body of five mares. A comparison between the animal with the lowest infestation and the animal with the highest infestation showed greater differences in animals infested with A. nitens than those infested with A. cajennense. Ten animals were found to carry 64.9% of the total parasite burden of A. cajennense and 88.6% of the highest infestations of A. nitens females. A seasonal variation on intensity of horse resistance to A. nitens was observed during the study. However, this was not observed for A. cajennense. Cross-resistance was observed in animals with the highest total number of A. cajennense and the highest number of A. cajennense adults (r=0.817), larvae (r=0.756), and A. nitens females (r=0.799). These results led to the conclusion that changes in horse resistance to A. nitens occur seasonally. As far as the total population of A. cajennense and the female stage of A. nitens are concerned, horses develop cross-resistance.

Analysis of the use of fenthion via epicutaneous in dogs for Rhipicephalus sanguineus control

The action of fenthion was studied in a 15% epicutaneous formulation upon Rhipicephalus sanguineus, which may transmit pathogens to men and other animals, such as Ehrlichia, Babesia and Ricketsia. Dogs were artificially infected for the trial. The fenthion bioassays were begun four months after artificial infestation. The test group, having a mean of 186 ticks per dog, received the formulation dosage according to body weight on the neck region. Tick counts were performed, considering diameters > or = 2mm, during 11 days of treatment, in the most affected body areas: back, ears and paws. Before the application of fenthion in the dogs, it were observed an average 43.3% ticks in the ears, 38.1% in the back area and 17.6% in the paws. The number of ticks in dogs decreased by 36.2%, 63.8%, 82.7%, 67%, 40% and 4.9%, respectively on days 1, 2, 3, 5, 7, 9 and 11 after treatment. R. sanguineus anti-tick activity, lower than that officially recommended, was verified. The number of ticks increased progressively after the 5th day, demonstrating residual insecticide inefficacy. The results obtained did not indicate the use of this formulation, at the tested dosage, as an elective measure for R. sanguineus control.

[Toxic effects and in vitro inefficacy of deltamethrin on larvae of Rhipicephalus sanguineus from Goiânia, Goiás, Brazil]

It has been observed that formulations of deltamethrin developed for disinsectization of infested places and control of parasitic arthropods of bovines and equines have frequently been used by breeders of dogs to control ticks in their animals and kennels, but without due consideration of the correct dosage or means of application. With the purpose of evaluating the efficacy of this product on Rhipicephalus sanguineus, bioassays were realized with larvae at 27+/-1 degrees C, UR>80% and light period of 12 hours. The mortality and toxicological effects were observed for 30 h, at 6 h intervals. Important toxicological effects were observed on the larvae, such as lack of co-ordination, knock-down and paralysis followed by death, although the lethal capacity of the product after 30 h was low, with mean mortality of only 34%, 40.2%, 46% and 57.6% respectively, for the 0.5 ml/l; 1 ml/l; 2 ml/l/; and 3 ml/l dosages. There was no mortality in the control group. The results obtained did not indicate the use of this formulation, in the tested dosages, as a method of choice for R. sanguineus control.

Ticks associated with wild animals in the Nhecolândia Pantanal, Brazil

A study of ticks associated with wild animals was carried out from September 1996 to April 1998 at the Fazenda Alegria (21,000 ha), in the Nhecolândia Pantanal, State of Mato Grosso do Sul, Brazil, a sunken plain bordering the upper Paraguay river, located 19 x 08'S; 56 x 46'W. A total of 81 wild animals (13 species, 6 orders) were captured with the aid of nets, and ticks were found on 63 (78%). Tick species identified included Boophilus microplus (Canestrini), Amblyomma cajennense (F.), A. parvum (Aragão), A pseudoconcolor (Aragão), A. scalpturatum (Neumann), A. nodosum (Neumann), A. ovale (Koch), and A. tigrinum (Koch). Dragging from grasslands (campos) yielded negative results compared to the high concentration of ticks, mainly nymphs, that were collected from leaves in the forests (capão). Predominance of immature instars (Amblyomma genera) was observed in the end of winter (August-September). Ticks were associated mainly with coatis, deer (Mazama gouazoubira) and anteater, and these animals may play a role in the epidemiology of tick-transmitted pathogens in the Pantanal if one considers their co-existence with local domestic animals.

Ticks (Acari: Ixodidae) associated with wild animals in the Pantanal region of Brazil

This paper describes the identification of ticks from wild animals of the Pantanal region in Brazil as part of a comprehensive study about established and emerging tick-host relationships and related pathological aspects. Eighty-one animals were captured (representing 13 species, six orders), and ticks were found on 63 (78%). Tick species identified included Boophilus microplus (Canestrini), Amblyomma cajennense (F.), Amblyomma parvum Aragão, Amblyomma pseudoconcolor Aragão, Amblyomma scalpturatum Neumann, Amblyomma nodosum Neumann, Amblyomma ovale Koch, and Amblyomma tigrinum Koch. Dragging from grasslands yielded negative results compared with the high concentration of ticks that were collected from leaves in the forests.

Population dynamics of the free-living stages of Amblyomma cajennense (Fabricius, 1787) (Acari: ixodidae) on pastures of Pedro Leopoldo, Minas Gerais State, Brazil

A study on the population behavior of Amblyomma cajennense larvae, nymphs and adult free-living stages was carried out in Pedro Leopoldo County, Minas Gerais State, Brazil, from July 1995 to July 1997. Larvae were collected from pasture from April to October using the technique of drag sampling with flannelette. The maximal larval population was observed during autumn (May) representing, respectively, 48 and 82% of the total numbers recovered during the first and the second years of the experiment. Nymphs and adults were captured throughout the year by the use of traps with carbon dioxide as chemical attractant. The highest population of nymphs occurred during the winter (July), representing 39.5% of the total collected specimens. Adults had the highest population density on pasture during spring and summer, i.e., from August to May, with peaks in January and February, representing 46 and 38.3% of the total collected specimens during the first and the second year of study, respectively.