Effect of low temperature and relative humidity on reproduction and survival of the tick Rhipicephalus microplus.

The objective of this study was to evaluate the survival of Rhipicephalus microplus females under low temperature, to determine the influence of temperature and relative humidity (RH) on the biological parameters of this tick. In total 300 viable engorged female ticks collected from cattle were used. On the day of collection (D0), 30 female ticks were divided into three groups: G1, kept at 28 °C and 80% RH; G2, kept at 20 °C and 80% RH; and G3, kept at 20 °C and 30% RH. The remaining females were stored in a refrigerator at 4 °C. Over the next 9 days (D+1 to D+9), 30 female ticks were removed daily from the refrigerator and distributed among the three treatments. Egg mass, feed conversion rate, egg incubation period, larval hatch rate, number of dead females per group, weight of female tick removed from the refrigerator, and female tick weight loss were recorded. At 20 °C and 80% RH hatching was delayed. Among the female ticks kept in the refrigerator and then allocated to groups G1, G2, and G3, there was a reduction in reproductive efficiency and a rise in mortality as time in the refrigerator increased. The female ticks expressed their best reproductive capacity when subjected to the refrigeration temperature for a maximum of 3 days and then kept at 28 °C and 80% RH. Thus, although female ticks can be stored in the refrigerator before being sent to research centers for use in bioassays, the storage time should be as short as possible, not exceeding 3 days.

Diversity of free-living ticks and serological evidence of spotted fever group Rickettsia and ticks associated to dogs, Porto Velho, Western Amazon, Brazil.

Rondônia is the only state in the North Region of Brazil to have registered confirmed cases of Brazilian Spotted Fever (BSF). The present study investigated the epidemiological cycle of Rickettsia spp. by surveying free-living ixodofauna and tick parasitism of dogs in the municipality of Porto Velho, Rondônia State. Ticks and dogs were tested for the presence of Rickettsia spp. DNA and dog serum was tested for reactivity to anti-Rickettsia spp. antibodies. Tick collection and dog blood sampling were performed in peri-urban and rural environments at 11 locations. Eight free-living Amblyomma species and one Haemaphysalis species were collected: A. scalpturatum, A. naponense, A. oblongoguttatum, A. coelebs, A. latepunctatum, A. pacae, A. ovale, Amblyomma sp., and H. juxtakochi. Three tick species were found parasitizing dogs: Rhipicephalus sanguineus sensu lato, A. oblongoguttatum and A. ovale. Molecular analysis did not identify the presence of the gltA gene fragment in any tick specimen. Results from an indirect immunofluorescent assay (IFA) showed that 20.8% of peri-urban and 15.4% of rural dog sera exhibited reactivity to Rickettsia rhipicephali, Rickettsia amblyommatis, Rickettsia bellii and Rickettsia parkeri antigens. Antibody prevalence in dogs was 16.4%. This study is the first to describe the prevalence of Rickettsia spp. infection in dogs from Porto Velho municipality. Our findings enhance current knowledge of Rickettsia spp. circulation in the Western Amazon.

Correlation between Rhipicephalus microplus ticks and Anaplasma marginale infection in various cattle breeds in Brazil.

The tick Rhipicephalus microplus is responsible for the transmission of Anaplasma marginale, which causes hemolytic anemia, abortion, decreased production, and mortality in cattle in Brazil. However, A. marginale can also persist in cattle herds without any clinical signs. This study investigated the relationship between the number of ticks present on each cattle and the circulating number of A. marginale msp1ß gene copies in the blood of Brangus and Nellore cattle reared in the Brazilian Cerrado through a year period. Twenty-three animals (11 Brangus and 12 Nellore) were raised for 12 months with ticks counted every 18 days, and blood collected every 36 days. Blood sera was used for total antigen iELISA, genomic DNA was extracted from whole blood by the phenol/chloroform method and then analyzed by PCR to confirm A. marginale presence with the msp5 gene. Positive samples were quantified by qPCR using msp1ß gene. Brangus cattle presented 4.5 fold more ticks than Nellore group. Although Brangus cattle carried a higher overall A. marginale msp1ß gene presence than Nellore cattle, no relationship of tick count and copy number could be achieved due to high variability in copy number. Moreover, both breeds showed similar weight gain and a similar serological pattern throughout the year. None of the animals showed any clinical signs of anaplasmosis during the experimental period, indicating that a low level of tick infestation may be sufficient to maintain a stable enzootic situation.

Spotted fever group Rickettsia and Borrelia sp. cooccurrence in Amblyomma sculptum in the Midwest region of Brazil.

More than 70 tick species are found in Brazil, distributed over five genera and including main vectors of infectious disease agents affecting both animals and humans. The genus Amblyomma is the most relevant for public health in Brazil, wherein Amblyomma aureolatum, Amblyomma ovale and Amblyomma sculptum have been incriminated as vectors of Rickettsia and Borrelia pathogens. The objective of this study was to investigate the presence of Rickettsia spp. and Borrelia spp. in ticks in the Brazilian mid-western savannah. DNA extraction, PCR for Borrelia spp. (flgE gene) and Rickettsia spp. (ompA and gltA genes) and subsequent sequencing were performed. A total of 1875 ticks were collected and identified as A. sculptum except for two Amblyomma coelebs ticks. Molecular evidence for Borrelia spp. and Rickettsia parkeri was found in A. sculptum. This is the first molecular evidence for R. parkeri in A. sculptum ticks in the Midwest region and Borrelia spp. circulating in a tick of the Amblyomma genus in Brazil.

Economic efficiency of Rhipicephalus microplus control and effect on beef cattle performance in the Brazilian Cerrado.

The cattle tick Rhipicephalus microplus causes significant economic losses to cattle production systems and is a main barrier to the introduction of Bos taurus breeds and their crosses in Brazil. These breeds have the genetic potential to generate animals that are more productive, but they are also more susceptible to R. microplus. One of the alternatives for conventional tick control is the use of strategic control, aiming at delaying or even preventing the development of its resistance to acaricides. The present study aimed to evaluate the economic losses caused by tick infestation on the productive performance of two breeds of beef cattle and to evaluate the economic efficiency of tick strategic control and its impacts on beef cattle production systems. Animal weights were obtained from the literature and were used to calculate the weight loss in kilograms (kg) and the economic loss (US$) caused by R. microplus infestation. The cost/loss ratio of performing strategic control was also calculated. The data show that tick infestation causes economic losses to the breeds and groups of animals evaluated and reduces animal performance (weight loss). The results show a loss of US$34.61/animal in the backgrounding phase and US$7.97/animal in the finishing phase for Brangus animals and its crosses. In conclusion, the data show that strategic control is economically efficient for Brangus animals in the backgrounding phase, independent of the methods used for acaricide application.

Economic performance evaluation of Brangus and Nellore cattle breed naturally infested with Rhipicephalus microplus in an extensive production system in Central-West Brazil.

The objective of the present study was to evaluate the performance of Brangus and Nellore cattle in an extensive production system. Sixty growing bulls, 30 of the Brangus and 30 of the Nellore breeds that were naturally infested with Rhipicephalus microplus were subdivided into four groups: control Nellore (15 animals), treated Nellore (15), control Brangus (15), and treated Brangus (15). The animals in the treated groups underwent acaricidal treatments for 1 year. Tick counts, acaricidal treatments and animal weighing were performed every 18 days, and the costs of acaricidal, anti-myiasis, and preventive treatments for tick fever were recorded for cost evaluation. The treated Brangus and Nellore groups did not show a significant difference in weight gain, whereas Nellore weight gain was superior in the control groups. The cost of acaricidal treatment throughout the experimental period was $494 US. The costs of the preventive treatment for tick fever and myiasis were $98 US and $15 US, respectively. The highest rates of tick infestation were found in the control group of the Brangus animals, which served as the basis for the suggested implementation of a strategic control program for animals in the growth phase. Nellore animals showed low rates of infestation. Under the conditions of this study, the Nellore animals were more efficient than the Brangus animals because they achieved satisfactory weight gain, similar to the Brangus, and a low tick count even in the control group. This finding demonstrates that expenses related to the acaricidal, anti-myiasis and tick fever treatments are unnecessary in Nellore cattle, making these animals more profitable.

In vitro efficacy of Metarhizium anisopliae sensu lato against unfed Amblyomma parvum (Acari: Ixodidae).

Amblyomma parvum Aragão (Acari: Ixodidae) is a tick species found with wide distribution in the Neotropical region. Even though it is a wildlife-related tick, it is also a frequent parasite of domestic animals, is aggressive to human beings and may harbor pathogenic microorganisms. Therefore, it is a target species for control on domestic animals, particularly those at the rural-wildlife interface. Herein, the efficacy of two isolates (E9 and IBCB 425) of an entomopathogenic fungus, Metarhizium anisopliae sensu lato, already evaluated for ticks that parasitize domestic animals, was tested against unfed A. parvum adults. Both isolates displayed high acaricidal efficacy after immersion in fungal conidial suspensions for 5 min. Isolate E9 killed all ticks by the 7th day post-treatment, and isolate IBCB 425 did so by the 11th day. Tick mortality of 80 and 90% was achieved as early as the 3rd and 4th days, respectively, with both treatments. Thus, if a commercial M. anisopliae s.l. acaricide against domestic animal ticks is developed, it would also be effective against A. parvum.

Life cycle of Amblyomma mixtum (Acari: Ixodidae) parasitizing different hosts under laboratory conditions.

Amblyomma mixtum is a tick species in the Amblyomma cajennense complex. The known geographic range of A. mixtum extends from Texas in the USA to western Ecuador and some islands in the Caribbean. Amblyomma mixtum is a vector of disease agents of veterinary and public health importance. The objective of this study was to describe the life cycle of A. mixtum under laboratory conditions. Bovines, rabbits and sheep were infested with larvae, nymphs, and adult ticks under controlled conditions to assess several biological parameters. Eggs, larvae, nymphs and adults were kept in an incubator (27 °C temperature and 80% relative humidity) when they were off the host. The average life cycle of A. mixtum was 88 and 79 days when fed on rabbits and cattle, respectively. Sheep were found to be unsuitable because no ticks attached. The rabbit is a more practical host to maintain a colony of A. mixtum under laboratory conditions. The data from this study can be considered as an example for the life cycle of A. mixtum. However, caution must be exercised when making comparisons to the biology of A. mixtum in its natural habitat.

Identification of Leishmania spp. promastigotes in the intestines, ovaries, and salivary glands of Rhipicephalus sanguineus actively infesting dogs.

Sand flies are recognized as the major vector of canine visceral leishmaniasis. However, in some areas of Brazil where sand flies do not occur, this disease is found in humans and dogs. There has been speculation that ticks might play a role in transmission of canine visceral leishmaniasis and the DNA of Leishmania spp. has been reported in whole ticks. We investigated the presence of Leishmania spp. promastigotes in the intestines, ovaries, and salivary glands of Rhipicephalus sanguineus ticks collected from tick-infested dogs in two cities of Brazil. We used 66 dogs that tested positive and 33 that tested negative for Leishmania spp. according to direct cytological examination assays. Ten ticks were collected from each dog and dissected to collect the intestines, ovaries, and salivary glands for immunohistochemistry (IHC) and diagnostic real-time polymerase chain reaction (RT-PCR). IHC results showed Leishmania spp. in 98, 14, and 8 % of the intestines, ovaries, and salivary glands, respectively. Real-time PCR showed that 89, 41, and 33 % of the tick intestine, ovary, and salivary glands, respectively, were positive for Leishmania spp. The verification of promastigotes of Leishmania spp. by two independent techniques in ticks collected from these urban region dogs showed that there is need for clarification of the role of ticks in the transmission of canine visceral leishmaniasis in Brazil.

Efficacy of Tagetes minuta (Asteraceae) essential oil against Rhipicephalus sanguineus (Acari: Ixodidae) on infested dogs and in vitro.

Ticks from Rhipicephalus sanguineus complex are widely distributed in the world and one species from this complex is the most common tick on dogs in Brazil, notably in urban areas. This tick is a vector of several diseases. Among others it transmits the agent of canine Ehrlichiosis, a major dog infectious disease and the agent of Rocky Mountain spotted fever. This tick can spread rapidly and develop intolerable infestations within no time. Currently tick control is done with acaricides and demand for such drugs has grown fast. However, R. sanguineus has already developed resistance to the main active compounds and the development of new acaricides is necessary. Many essential oils of plants have acaricidal effect and may be an important source of molecules for the synthesis of new acaricide products. In this study, we evaluated the effectiveness of a new herbal phytotherapic, consisting of the essential oil of Tagetes minuta L., against R. sanguineus in vitro and on dogs undergoing experimental infestations. The product displayed 100% efficacy against larvae, nymphs and adults of the tick on all tested conditions.

Profile of cattle breed sensitivity to the tick Rhipicephalus microplus.

Among cattle, Bos taurus breeds and their crosses are more sensitive to tick infestations than Bos indicus breeds that are more resistant to infestation and more adaptable to tropical climates. The presence of susceptible individuals in herds and inadequate tick control lead to direct and indirect losses in the meat production chain, in addition to increased mortality due to cattle tick fever. The objective of this study was to describe, compare and rank the sensitivity of different breeds of stabled cattle to the tick Rhipicephalus microplus and to present, as an innovative result, a scale called the Tick Ruler. Secondary data on the number of retrieved engorged females, engorged female ticks' weight, egg mass weight and number of larvae were extracted from research reports of experiments conducted over 18 years with eight breeds to describe and report the sensitivity of the breeds to artificial infestation by R. microplus larvae. For analyses, the recovery rate of engorged female ticks and the percentile of dispersion of individuals in their respective races were calculated, and comparison of these percentiles between races was performed. The ranking of the percentiles resulted in the organization of the breeds by their susceptibility to R. microplus; we call this scale the "Tick Ruler." The ruler is a simple, easy-to-understand tool that can be used by technicians and producers to evaluate the tick sensitivity of a breed of interest and can assist producers in decision-making to find a balance between increased production gains and the risk of economic losses depending on the breed composition in a cattle herd.

Control of Rhipicephalus microplus tick larvae in the field based on distancing from the host - Lone tick system.

The aim of this study was to evaluate a host-tick distancing control system using Rhipicephalus microplus in cattle. Its impact on the profiles of the pathogens Anaplasma marginale and Babesia bigemina was also assessed using enzyme-linked immunosorbent and real-time polymerase chain reaction. Experiments were conducted in Mato Grosso do Sul, Brazil. A total of 37 Senepol animals with natural tick infestation were used in this study. The ticks on the animals were counted, and pasture rotation was performed at 28-day intervals. This approach was repeated until the end of the experiment to maintain a low number of ticks, resulting in a final average of 6.3 ticks/host. Cattle maintained an immune response to the cattle tick fever (CTF) agents. DNA copies of A. marginale (X̄ 1.1) and B. bigemina (X̄ 0.05) did not vary significantly with the decrease in tick count throughout the study period. Based on these results, we conclude that a distancing period of 84 days between ticks and cattle in conditions of the Cerrado biome can control ticks in animals and maintain enzootic stability. Thus, it is possible to create productive breeds with lower tick control costs.

Babesia bigemina (smith and Kilbourne, 1893) detection in Amblyomma sculptum (Berlese, 1888) ticks in the Mato Grosso do Sul state, Brazil.

Ticks parasitize various hosts, including humans, and are known to transmit pathogens that can be harmful not only to animals but also to humans. To evaluate the possible presence of pathogens in ticks, we aimed to collect and identify tick fauna specimens in Lagoa Comprida Municipal Natural Park, an anthropogenic urban area located in Aquidauana, Mato Grosso do Sul, Brazil. A total of 1216 ticks, of which 51.2% were Amblyomma sculptum, 1.2% were Amblyomma dubitatum, and 41% were Amblyomma spp. were collected. These results show that the prevalence of A. sculptum is significantly higher than that of A. dubitatum across all four seasons. Molecular analyses revealed positive samples for the genus Babesia, including the confirmation of Babesia bigemina in an A. sculptum specimen, marking the first record of this relationship. This unexpected finding demands greater attention and deeper analysis in the context of the epidemiology of tick-borne diseases.

Ixodid fauna and zoonotic agents in ticks from dogs: first report of Rickettsia rickettsii in Rhipicephalus sanguineus in the state of Mato Grosso do Sul, mid-western Brazil.

Ticks from 148 dogs from the urban area of the municipality of Campo Grande, state of Mato Grosso do Sul, Brazil, were collected, classified and analyzed using polymerase chain reaction (PCR) for the identification of Rickettsia spp., Trypanosoma cruzi and Leishmania spp. A total of 2015 ticks were collected. The species Rhipicephalus sanguineus (98.9 %) and Amblyomma cajennense (1.1 %) were identified. Molecular analysis revealed that no tick samples were infected by T. cruzi. Regarding Leishmania spp., tick samples from 36 dogs spread across all regions of the municipality were positive for L. chagasi. One tick sample was positive for Rickettsia spp. (gltA gene) in the PCR reaction. This sample was submitted to further PCR based on the ompA gene and the amplicon was sequenced. Identity of 100 % was found with homologous sequences of R. rickettsii available in GenBank. This paper is the first to report the natural infection of R. sanguineus by R. rickettsii in the municipality of Campo Grande, state of Mato Grosso do Sul, mid-western Brazil.

Rickettsia parkeri strain Atlantic rainforest infecting Amblyomma ovale (Acari: Ixodidae) in the Amazon Biome (Acre state, Brazil).

There is a lack of studies regarding tick-associated Rickettsia in the Amazon biome. Aiming to contribute to this knowledge, our research group collected ticks in the Western Amazon to better understand the tick fauna and their associated Rickettsia. In this study, we detected Rickettsia parkeri strain Atlantic rainforest DNA in the tick Amblyomma ovale Koch, 1844 in Rio Branco municipality, Acre state, northern Brazil. This is the first time that the R. parkeri strain Atlantic rainforest has been reported in the Amazon biome and is the first evidence of the circulation of a pathogenic spotted fever group (SFG) Rickettsia in this biome. This finding provides substantial information to help public health authorities understand which species of Rickettsia may be related to Amazon spotted fever cases.

Control Strategies for the Tick Rhipicephalus Microplus (Canestrini, 1888) on Cattle: Economic Evaluation and Report of a Multidrug-Resistant Strain.

PURPOSE: The aim of this study was to evaluate four strategies for application of acaricides to control the tick Rhipicephalus microplus among infested cattle, and to show which of these has the best cost-benefit ratio. METHODS: For this, 72 cattle were selected and divided into four groups: Group 1 (G1): fipronil, pour-on; Group 2 (G2): fluazuron, pour-on; Group 3 (G3): moxidectin, injectable; and Group 4 (G4): chlorpyrifos 30 g, cypermethrin 15 g and fenthion 15 g, spraying (atomizing chamber). Every seven days, the numbers of semi-engorged females were counted and laboratory tests were conducted using different commercial technical-grade products for resistance monitoring. RESULTS: G4 showed the best percentage reduction, with the highest rate on the seventh day post-treatment (DPT) (83.23%). G3 was the second best strategy, with a percentage of inverse reduction such that the best results were on the 28th DPT (82.85%), while G1 and G2 reached their best results on the 21st DPT (32.63% and 2.79%). CONCLUSION: It was noteworthy that the formulation used in G4 was the only one that was efficient for strategic control and that, based on the economic analysis, was shown to be economically viable over the medium term due to the need for investment. The presence of a multidrug-resistant strain in the state of Mato Grosso do Sul in vitro, for the chemical bases amitraz, cypermethrin and cypermethrin + DDVP, is reported here for the first time.

Amblyomma ticks in animal carcasses hunted in Mapinguari National Park, Western Amazon, Brazil: New records on species and host-parasite relationships.

Ticks are obligatory parasites and transmit several pathogens to animals and humans. This study aimed to report the parasitism of ticks on carcasses of animals hunted by hunters from communities near Mapinguari National Park, at the shared border of Amazonas and Rondonia states, northern Brazil. The ticks were collected from heads of carcasses of the following animals: South American tapir (Tapirus terrestris), collared peccary (Pecari tajacu) and long-nosed armadillo (Dasypus beniensis). Six Amblyomma tick species were identified: Amblyomma coelebs, Amblyomma naponense, Amblyomma latepunctatum, Amblyomma oblongoguttatum, Amblyomma scalpturatum, Amblyomma triste and Amblyomma spp. The most abundant tick species were A. oblongoguttatum and A. scalpturatum. DNA extraction and polymerase chain reaction (PCR) were performed on all ticks to test for the presence of rickettsial gltA gene fragments, but no amplification was observed. This study reports, for the first time, the parasitism of A. coelebs in the armadillo D. beniensis and the presence of A. triste in the states of Amazonas and Rondonia, updating the tick fauna to 24 and 39 species for these states, respectively.

Tick fauna in non-anthropogenic areas in Mato Grosso do Sul, Brazil, with the presence of the Rickettsia parkeri strain Atlantic rainforest in Amblyomma ovale.

The aim of this study was to evaluate tick fauna and identify the possible presence of Rickettsia spp. in ticks of the genus Amblyomma from two environmental preservation areas in different regions of Mato Grosso do Sul state, Brazil. CO2 traps, visual observation and cloth dragging were used to capture ticks. Three hundred ticks were submitted to the hemolymph test, and samples that showed organisms morphologically compatible with Rickettsia were used for rickettsial DNA detection by PCR. DNA was extracted using guanidine-phenol isothiocyanate, and the primers CS78 and CS323 were used for PCR, which amplified a 401-base pair fragment of the citrate synthase (gltA) gene. If positive, the DNA sample was tested by primers Rr190.70p and Rr190.602n that produce a 530 bp amplicon of the ompA gene that is present only in rickettsiae of the spotted fever group. A total of 1,745 adult ticks were collected, including 1,673 specimens of Amblyomma sculptum, 63 of Amblyomma coelebs, five of Amblyomma naponense and four of Amblyomma ovale. Thirteen ticks of the species A. ovale, A. coelebs and A. sculptum showed structures compatible with Rickettsia inside the hemocytes; after DNA extraction, the presence of Rickettsia spp. in a sample of A. ovale was confirmed by PCR in both analyzed fragments. In the sequencing analysis, 100% identity for the Rickettsia parkeri strain Atlantic rainforest was obtained according to GenBank. The two environmental preservation areas showed A. sculptum as the predominant species, as well as the presence of marked seasonality for this species. This paper is the first report of the R. parkeri strain Atlantic rainforest in A. ovale ticks in the state of Mato Grosso do Sul, Brazil.

Seasonal fluctuations of Babesia bigemina and Rhipicephalus microplus in Brangus and Nellore cattle reared in the Cerrado biome, Brazil.

BACKGROUND: The tick Rhipicephalus microplus (Ixodida: Ixodidae, Canestrini, 1888) causes substantial economic and health losses in cattle production and is the main vector of Babesia bigemina (Piroplasmidae: Babesidae, Smith & Kilborne, 1893). Babesia bigemina is responsible for a tick-borne disease known as babesiosis that can cause hemolytic anemia, fever and death. In the study reported here, we investigated the relationship between the number of ticks per animal and the number of B. bigemina cytochrome b gene (cbisg) copies in the blood of Brangus and Nellore cattle reared without acaricidal treatment in the Brazilian Cerrado biome over a 1-year period. METHODS: Ticks on 19 animals (9 Brangus and 10 Nellore cattle) were counted every 18 days, and blood was collected every 36 days for 12 months. Serological samples were analyzed with an indirect enzyme-linked immunosorbent assay, and genomic DNA was analyzed by conventional PCR and quantitative PCR. The PCR products were sequenced by the Sanger method. RESULTS: The Brangus and Nellore breeds showed similar weight development and no clinical signs of babesiosis. Statistically significant differences (P < 0.05) between the breeds were observed for the number of ticks and the number of B. bigemina cbisg gene copies. CONCLUSIONS: No correlation between the number of ticks and the number of circulating copies of cbisg was observed, although Nellore cattle presented with fewer ticks than Brangus cattle and the number of cbisg copies was higher for Nellore cattle than for Brangus cattle.

Ticks (Acari: Ixodidae) within various phytophysiognomies of a Cerrado reserve in Uberlândia, Minas Gerais, Brazil.

Cerrado biome, the South American savannah, covers about 2 million km(2) and is very rich in endemic species but threatened by agriculture. In this report free-living tick species are presented, and their seasonal and relative distribution within the various phytophysiognomies in a small Cerrado reserve in Minas Gerais State, Brazil. Overall 2,694 free-living ticks were found during a 2 years sampling period with CO(2) traps and cloth dragging. Of these, 73.5% were Amblyomma cajennense and 0.6% Amblyomma dubitatum. All other ticks (25.9%) were retained as Amblyomma spp. Adults of A. cajennense peaked in spring, the nymphs in winter of both years. Amblyomma larval clusters were found in autumn and winter. Adult ticks (46.7%) and nymphs (39.5%) were most often found in woodlands, whereas most larval clusters were found in valley-side marshes (39%). Amblyomma cajennense, Anocentor nitens, Rhipicephalus (Boophilus) microplusand Rhipicephalus sanguineus ticks were found on domestic animals from neighboring properties. Search for Rickettsia in the hemolymph of 497 A. cajennense and one A. dubitatum ticks yielded negative results. Results confirmed earlier reports on the overwhelming prevalence of A. cajennense ticks in the Cerrado biome of Brazil and added information to habitat preferences of this tick species, a major vector in Brazil of the Rocky Mountain spotted fever.