RESUMO
Amblyomma sculptum is a species of tick in the family Ixodidae, with equids and capybaras among its preferred hosts. In this study, the acaricidal activity of the essential oil (EO) from Piper aduncum and its main component, Dillapiole, were evaluated against larvae of A. sculptum to establish lethal concentration values and assess the effects of these compounds on tick enzymes. Dillapiole exhibited slightly greater activity (LC50 = 3.38 mg/mL; 95% CI = 3.24 to 3.54) than P. aduncum EO (LC50 = 3.49 mg/mL; 95% CI = 3.36 to 3.62) against ticks. The activities of α-esterase (α-EST), ß-esterase (ß-EST), and glutathione-S-transferase (GST) enzymes in A. sculptum larvae treated with Dillapiole showed a significant increase compared to the control at all concentrations (LC5, LC25, LC50 and LC75), similar results were obtained with P. aduncum EO, except for α-EST, which did not differ from the control at the highest concentration (LC75). The results of the acetylcholinesterase (AChE) activity show an increase in enzyme activity at the two lower concentrations (LC5 and LC25) and a reduction in activity at the two higher, lethal concentrations (LC50 and LC75) compared to the control. These results suggest potential mechanisms of action for these natural acaricides and can provide guidance for the future development of potential plant-derived formulations.
Assuntos
Acaricidas , Acetilcolinesterase , Amblyomma , Óleos Voláteis , Piper , Animais , Acaricidas/farmacologia , Acetilcolinesterase/metabolismo , Compostos Alílicos , Amblyomma/efeitos dos fármacos , Amblyomma/crescimento & desenvolvimento , Benzodioxóis/farmacologia , Inibidores da Colinesterase/farmacologia , Dioxóis , Esterases/metabolismo , Glutationa Transferase/metabolismo , Inativação Metabólica , Larva/efeitos dos fármacos , Óleos Voláteis/farmacologia , Óleos Voláteis/química , Piper/químicaRESUMO
Tick-borne viruses (TBV) have gained public health relevance in recent years due to the recognition of human-associated fatal cases and the increase in tick-borne disease and transmission. However, many tick species have not been studied for their potential to transmit pathogenic viruses, especially those found in Latin America. To gain better understanding of the tick virome, we conducted targeted amplification using broadly-reactive consensus-degenerate pan-viral targeting viruses from the genera Flavivirus, Bandavirus, Uukuvirus, and Orthonairovirus genus. Additionally, we conducted unbiased metagenomic analyses to investigate the presence of viral RNA sequences in Amblyomma cajennense, A. patinoi and Rhipicephalus microplus ticks collected from a horse slaughter plant in Medellín, Colombia. While no viral products were detected by PCR, results of the metagenomic analyses revealed the presence of viral genomes belonging to the genera Phlebovirus, Bandavirus, and Uukuvirus, including Lihan Tick Virus (LTV), which was previously reported in Rhipicephalus microplus from Colombia. Overall, the results emphasized the enormous utility of the next-generation sequencing in identifying virus genetic diversity presents in ticks and other species of vectors and reservoirs.
Assuntos
Vírus de RNA , Rhipicephalus , Animais , Humanos , Cavalos , Rhipicephalus/genética , Amblyomma , Colômbia , Viroma/genéticaRESUMO
In Ecuador, the main tick species affecting cattle are Rhipicephalus microplus and Amblyomma cajennense sensu lato. Understanding their spatial distribution is crucial. To assess their distribution, data from 2895 farms visited between 2012 and 2017 were utilized. Ticks were collected during animal inspections, with each farm's location georeferenced. Bioclimatic variables and vapor pressure deficit data were obtained from Climatologies at High resolution for the Earth´s Land Surface Areas (CHELSA) dataset. They were overlaid to develop predictive maps for each species using Random Forest (RF) models. The cross-validation results for RF prediction models showed high accuracy for both R. microplus and A. cajennense s.l. presence with values of accuracy = 0.97 and 0.98, sensitivity = 0.96 and 0.99, and specificity = 0.96 and 0.93, respectively. A carefully selected subset of bioclimatic variables was used to describe the presence of each tick species. Higher levels of precipitation had positive effect on the presence of R. microplus but a negative effect on A. cajennense s.l. In contrast, isothermality (BIO3) was more important for the presence of A. cajennense s.l. compared to R. microplus. As a result, R. microplus had a broader distribution across the country, while A. cajennense s.l. was mainly found in coastal areas with evident seasonality. The coexistence of both species in some regions could be attributed to transitional zones, whereas high altitudes limited tick presence. This information can aid in developing appropriate tick management plans, particularly considering A. cajennense s.l.'s broad host range species and R. microplus's specificity for cattle. Moreover, the predictive models can identify areas at risk of associated challenging hemoparasite, requiring special attention and mitigation measures.
Assuntos
Amblyomma , Distribuição Animal , Doenças dos Bovinos , Clima , Rhipicephalus , Infestações por Carrapato , Animais , Equador , Bovinos , Rhipicephalus/fisiologia , Amblyomma/fisiologia , Amblyomma/crescimento & desenvolvimento , Infestações por Carrapato/veterinária , Infestações por Carrapato/epidemiologia , Infestações por Carrapato/parasitologia , Doenças dos Bovinos/parasitologia , Doenças dos Bovinos/epidemiologiaRESUMO
Amblyomma sculptum is a relevant tick species from a One Health perspective, playing an important role as a vector of Rickettsia rickettsii, the main agent of spotted fever rickettsiosis in Brazil. In this study, we evaluated the susceptibility of two A. sculptum populations from Goiás state (midwestern Brazil) to different acaricides. The first tick population (GYN strain) originated from an experimental farm, where the ticks are annually exposed to acaricides. The second (PNE strain) was collected in a national park (Emas National Park), where the ticks had not been exposed to acaricides. Immersion tests were conducted with 21-day-old laboratory-reared larvae and nymphs originating from adult ticks collected in the areas mentioned above. The chosen acaricides were two synthetic pyrethroids (cypermethrin and deltamethrin), one organophosphate (chlorfenvinphos), one formamidine (amitraz), and two combinations of pyrethroids and organophosphates (cypermethrin, chlorpyrifos and citronellal; cypermethrin, fenthion and chlorpyrifos). Mortality data were used to determine the lethal concentration (LC) values at which 50%, 90%, and 99% of the ticks died (LC50, LC90, and LC99, respectively), and resistance ratios (RR) were calculated based on the LC values. The RR revealed differences between the acaricide-exposed (GYN) and unexposed (PNE) tick strains. The PNE strain larvae and nymphs were susceptible to all the tested acaricides. The GYN strain larvae were tolerant to cypermethrin, whereas the nymphs were tolerant to deltamethrin, chlorfenvinphos, and the combination of cypermethrin, chlorpyrifos, and citronellal (2 < RR ≤ 10). The GYN strain nymphs were resistant to amitraz (RR > 10). This is the first report of A. sculptum nymphs with resistance to amitraz and tolerance to deltamethrin, chlorfenvinphos, and the combination of cypermethrin, chlorpyrifos, and citronellal.
RESUMO
BACKGROUND: The tick Amblyomma cajennense sensu stricto (A. cajennense s.s.) frequently parasitizes animals and humans in the Amazon biome, in addition to being a vector of Rickettsia amblyommatis. In the present study, we evaluated both the population dynamics of A. cajennense s.s. in a degraded area of the Amazon biome and the presence of rickettsial organisms in this tick population. METHODS: The study was carried out in a rural area of the Santa Inês municipality (altitude: 24 m a.s.l.), Maranhão state, Brazil. Ticks were collected from the environment for 24 consecutive months, from June 2021 to May 2023. The region is characterized by two warm seasons: a rainy season (November-May) and a dry season (June-October). We characterized the temporal activity of A. cajennense s.s. on the vegetation by examining questing activity for each life stage (larvae, nymphs, adults [males and females]) in relation to the dry and rainy season. Ticks collected in this study were randomly selected and individually tested by a TaqMan real-time PCR assay that targeted a 147-bp fragment of the rickettsial gltA gene. RESULTS: Overall, 1843 (62.4%) adults (52.6% females, 47.4% males), 1110 (37.6%) nymphs and 398 larval clusters were collected. All adult females and nymphs were morphologically identified as A. cajennense s.s. Larval activity was observed from April to December, with a peak from June to September (dry season); nymph abundance peaked from September to November (transition period between dry and rainy seasons); and adult ticks were abundant from October to May (spring/summer/early autumn). The infection rate by R. amblyommatis in A. cajennense s.s. ticks was at least 7% (7/99). CONCLUSION: Our data suggest a 1-year generation pattern for A. cajennense s.s., with a well-defined seasonality of larvae, nymphs and adults in the Amazon biome. Larvae predominate during the dry season, nymphs are most abundant in the dry-rainy season transition and adults are most abundant in the rainy season. The presence of R. amblyommatis in adult ticks suggests that animals and humans in the study region are at risk of infection by this species belonging to the spotted fever group of Rickettsia.
Assuntos
Ixodidae , Infecções por Rickettsia , Rickettsia , Carrapatos , Animais , Humanos , Masculino , Feminino , Estações do Ano , Amblyomma , Rickettsia/genética , Infecções por Rickettsia/epidemiologia , Infecções por Rickettsia/microbiologia , Carrapatos/microbiologia , Brasil/epidemiologia , Ninfa/microbiologia , Larva/microbiologia , EcossistemaRESUMO
Aedes aegypti are vector insects of arboviruses such as dengue, Zika, and chikungunya. All available vector control methods have limited efficacy, highlighting the urgent need to find alternative ones. Evidence shows that arachnids like ticks are sources of biologically active compounds. Moreover, chemical modulation of the locomotor and immune systems of vector insects can be used to control arbovirus transmission. The present study evaluated the effectiveness of crude saliva of female Amblyomma cajennense sensu stricto (s.s.) ticks in reducing locomotor activity and inducing an immune response in Ae. aegypti females. Additionally, the study evaluated the protein constitution of tick saliva. For this purpose, the crude saliva obtained from several semi-engorged A. cajennense females was used. A volume of 0.2 nL of crude tick saliva was administered to mosquitoes by direct intrathoracic microinjection. The effect of the tick's saliva on the locomotor activity of the mosquito was observed using Flybox, a video-automated monitoring system, and the hemolymph hemocyte levels were quantified by reading slides under a light microscope. The protein concentration of the crude tick saliva was 1.27 µg/µL, and its electrophoretic profile indicates the presence of proteins with a molecular weight ranging between â¼17 and 95 kDa. Microplusins, ixodegrins, cystatin, actins, beta-actin, calponin, albumin, alpha-globulins, and hemoglobin were the main proteins identified by proteomics in the saliva of A. cajennense. The microinjected saliva had low toxicity for Ae. aegypti females and significantly reduced their locomotor activity, especially in the transition between the light and dark phases. The crude tick saliva did not change the period and rhythmicity of the circadian cycle. The tick saliva significantly increased the number of hemocytes two days after injection and reduced it after five days. These results suggest that further evaluation of the biological properties of tick saliva proteins against Ae. aegypti would be of interest.
Assuntos
Aedes , Ixodidae , Infecção por Zika virus , Zika virus , Animais , Feminino , Saliva , Amblyomma , Hemócitos , Mosquitos Vetores , Locomoção , Zika virus/fisiologiaRESUMO
The present study reports a case of conspecific hyperparasitism for Amblyomma sculptum. Two partially engorged females were collected from two naturally infested dairy cows and placed in a single petri dish to be transported to the laboratory, where they were held in a biological oxygen demand (BOD) incubator chamber under controlled conditions of 27 ± 1 °C and 85 ± 5% RH. After one day, it was observed that the smaller female (female 1) was attached to the dorsal surface of the larger female (female 2). The hypostome and chelicerae of the female 1 were entirely inserted into the cuticle of the female 2, characterizing tick attachment. Pictures were taken to illustrate the finding. After a few hours, the female 1 detached spontaneously and showed no visible signs of additional enlargement (engorgement). The females did not lay eggs and the survival period was not recorded. To our knowledge this is the first report of hyperparasitism for A. sculptum and the fourth for the genus Amblyomma.
Assuntos
Ixodidae , Carrapatos , Animais , Bovinos , Feminino , Amblyomma , BrasilRESUMO
Amblyomma sculptum is a species of public health interest because it is associated with the transmission of the bacteria that causes Brazilian Spotted Fever (BSF). The use of repellents on humans is a prophylactic measure widely used to provide protection against a series of arthropod vectors, including mosquitoes and ticks. However, in Brazil, the effectiveness of commercial repellents against A. sculptum is little known. Therefore, it is necessary to carry out specific studies to evaluate the repellency of these commercial products, registered for use against mosquitoes, against the star tick. The main goal of the present work was to evaluate the effectiveness of six commercial repellents against A. sculptum. Unfed nymphs, aged between two and eight weeks, were tested against products based on DEET (OFF!® and Repelex®), Icaridin (Exposis® and SBP®), and IR3535 (Johnsons and Henlau). Three bioassays were conducted to evaluate tick behavior: (i) filter paper, (ii) fingertip, and (iii) field. All bases tested showed high repellent activity, differing significantly (p < 0.05) from the control. It was observed the formulation with DEET resulted in the best results in the filter paper bioassay. In the fingertip bioassay, the DEET base repelled a greater number of ticks compared to Icaridin. In the field bioassay, there was no significant difference between the Icaridin base and DEET, and both formulations differed from the control (p < 0.05). The six formulations tested showed significant percentages of repellency against ticks; however, for the fingertip and field bioassays, the products OFF!®, Repelex®, and Exposis® were tested as they showed better performance in the filter paper test. OFF!® showed the best percentage of repellency (100%), followed by Repelex® (96.8%), and Exposis® (93.1%), considering the two-hour period of the bioassay-field-test. Proving the effectiveness of repellents on the market against A. sculptum presented in this study is crucial, since this is the main ectoparasite of humans that can transmit Rickettsia rickettsii when infected. The effectiveness of commercial insect repellents against other tick species that parasitize humans can also be explored.
RESUMO
Amblyomma cajennense Fabricius, 1787 (Acari: Ixodidae) is a widely distributed tick taxon. Recent studies have reassessed this taxon as a complex of six species. Amblyomma mixtum Koch, 1844 has been suggested by some authors as the only species of this complex that is present in Cuba. Other authors have pointed a niche overlapping for A. mixtum and A. cajennense s.s. in the country. Detailed taxonomic studies on the Cuban species belonging to this complex are needed in order to evaluate their current distribution according to the recent classification. This study aimed to characterize Cuban populations from the A. cajennense complex by using tick samples obtained from 3 occidental provinces and 1 central province of the country. Morphological identification and measurements of the main relevant taxonomic structures were conducted by using Scanning Electron Microscopy. Phylogenetic analyzes were carried out with 16S ribosomal RNA, internal transcribed spacer 2 and the subunit I of mitochondrial cytochrome c oxidase gene sequences. The results of these studies demonstrated that all samples belonged to the species A. mixtum (Koch, 1844). This study constitutes the first molecular characterization of this Amblyomma species in Cuba. Further studies will be necessary in order to corroborate if A. cajennense s.s. is also present in the island.
Assuntos
Amblyomma/anatomia & histologia , Amblyomma/genética , Distribuição Animal , Amblyomma/crescimento & desenvolvimento , Animais , Cuba , DNA Espaçador Ribossômico/análise , Cães/parasitologia , Complexo IV da Cadeia de Transporte de Elétrons/análise , Feminino , Cavalos/parasitologia , Larva/anatomia & histologia , Larva/genética , Larva/crescimento & desenvolvimento , Masculino , Ninfa/anatomia & histologia , Ninfa/genética , Ninfa/crescimento & desenvolvimento , Filogenia , RNA Ribossômico 16S/análise , Carneiro Doméstico/parasitologiaRESUMO
Rickettsia amblyommatis has been reported infecting various tick species throughout the western hemisphere, including Amblyomma cajennense sensu stricto (s.s.). The present study aimed to evaluate whether R. amblyommatis can be maintained by transovarial transmission and transstadial passage in A. cajennense s.s. ticks, and whether these ticks are competent vectors of this rickettsial agent. We selected engorged females that were naturally infected or uninfected by R. amblyommatis, and reared their offspring (infected and control groups, respectively). Immature ticks were allowed to feed on guinea pigs, whereas adults fed on rabbits. All stages and individuals of each generation of the infected group yielded rickettsial DNA, which was not detected in any tick from the control group. No host from the control group seroconverted to R. amblyommatis. Among 16 guinea pigs and eight rabbits infested with R. amblyommatis-infected ticks, only one guinea pig seroconverted to R. amblyommatis. Some unfed adult ticks of the infected group were dissected, and DNA was extracted from their salivary glands and from their carcasses. DNA of R. amblyommatis was detected in all carcasses, but not in the salivary glands. Results of this study indicate very low vector competence of A. cajennense s.s. for R. amblyommatis. Previous studies reported domestic animals with high titers to R. amblyommatis in areas where these animals are naturally infested chiefly by A. cajennense s.s. ticks. One may consider that the vector competence of A. cajennense s.s. for R. amblyommatis could vary among tick populations and/or rickettsial strains.
Assuntos
Vetores Artrópodes/microbiologia , Infecções por Rickettsia/veterinária , Rickettsia/isolamento & purificação , Carrapatos/microbiologia , Animais , Brasil , Feminino , Cobaias , CoelhosRESUMO
The Brazilian state of Goiás, untouched by spotted fever (SF) until 2012, has subsequently reported cases of the disease in several regions. This study aimed to survey the diversity of potential vectors and rickettsia in areas of Goiás under environmental surveillance or case investigation for SF. Collected specimens were assayed with molecular biology technology using DNA extraction, amplification and sequencing of fragments of the genes gltA, ompA, ompB and sca4 to detect rickettsia in ticks and fleas. Amplification of cytochrome oxidase subunit II and 16S rRNA was performed to assist tick identification. Rickettsia felis (Rickettsiales: Rickettsiaceae) was found in Ctenocephalides felis (Bouché, 1835) (Siphonaptera: Pulicidae). Rickettsia bellii was found in Amblyomma rotundatum Koch, 1844 (Ixodida: Ixodidae) and in Amblyomma cajennense sensu lato. Rickettsia sp. strain NOD was found in Amblyomma nodosum Neumann, 1899. Of the Amblyomma cajennense complex, Amblyomma sculptum Berlese, 1888 was confirmed in the northern, northeast, midwest and southeast regions of Goiás, whereas Amblyomma cajennense sensu stricto (Fabricius, 1787) was found only in the northern region of the state. Amblyomma dubitatum Neumann, 1899 associated with a species of the A. cajennense complex was the most common epidemiological finding, although Rickettsia rickettsii was not detected. This is the first report of Rickettsia sp. strain NOD in Goiás.
Assuntos
Vetores Aracnídeos/microbiologia , Insetos Vetores/microbiologia , Ixodidae/microbiologia , Rickettsia/fisiologia , Febre Maculosa das Montanhas Rochosas/transmissão , Sifonápteros/microbiologia , Animais , Vetores Aracnídeos/classificação , Vetores Aracnídeos/genética , Biodiversidade , Brasil/epidemiologia , DNA Bacteriano/química , DNA Bacteriano/isolamento & purificação , Ecossistema , Ectoparasitoses/microbiologia , Ectoparasitoses/parasitologia , Feminino , Insetos Vetores/classificação , Ixodidae/classificação , Ixodidae/genética , Masculino , Filogenia , Reação em Cadeia da Polimerase , Rickettsia/classificação , Rickettsia/genética , Febre Maculosa das Montanhas Rochosas/epidemiologia , Febre Maculosa das Montanhas Rochosas/microbiologia , Alinhamento de Sequência , Sifonápteros/classificaçãoRESUMO
Recent studies indicated that the taxon Amblyomma cajennense (Fabricius, 1787) is a complex of 6 valid species, of which only two, Amblyomma cajennense sensu stricto (s.s.) and Amblyomma sculptum Berlese, 1888 are present in Brazil; the former species is found exclusively in areas of the Amazon biome, and A. sculptum mostly in the Cerrado biome. Populations of A. cajennense s.s. and A. sculptum are usually sustained by the same host species, and are found in many areas with similar temperature and photoperiod regimens. On the other hand, differences in the rainfall regimen and vegetation cover of the Amazon and Cerrado biomes, reflecting different vapor saturation deficit of atmosphere in the soil, could be primary factors driving the geographical distribution of the two species. In this study, all developmental stages in the life cycle of A. cajennense s.s. and A. sculptum were exposed to different temperature, photoperiod, and relative humidity (65, 78 or 100%) regimens that simulated mean conditions during summer or winter of one area of the Amazon and one area of the Cerrado in Brazil. Ticks were also exposed to water immersion during different periods of time (24, 48, or 72â¯h). Our experiments showed that A. sculptum showed significantly higher molting success for engorged larvae and oviposition success for engorged females than A. cajennense s.s. when these engorged ticks were incubated at higher saturation deficit conditions (65 and/or 78% RH with summer and winter mean temperatures). On the other hand, when ticks were immersed in water for 24, 48 or 72â¯h, there was a clear tendency for engorged stages (larvae, nymphs or females) of A. cajennense s.s. to have greater molting or oviposition success than A. sculptum. These results indicate that engorged stages of A. sculptum showed a greater capacity to survive under higher saturation deficit conditions (lower RH values associated with mean summer and winter temperatures), and engorged stages of A. cajennense s.s. had a greater capacity to survive under the highest moisture conditions, namely immersed in water for a relatively short period (24-72â¯h). When applied to the natural distributions of A. cajennense s.s. and A. sculptum in Brazil, we can infer that the former species is more adapted to the humid conditions of the Amazon biome, where the soil inside forests is quite moist throughout the year, and often swampy or flooded during the raining season. On the other hand, immature stages of A. sculptum are more adapted to the drought period of the Cerrado biome, when higher saturation deficit conditions prevail on the soil.
Assuntos
Ixodidae/fisiologia , Larva/fisiologia , Estágios do Ciclo de Vida/fisiologia , Animais , Brasil , Ecossistema , Feminino , Umidade , Muda/fisiologia , Ninfa/fisiologia , Oviposição/fisiologia , Estações do Ano , América do SulRESUMO
Ticks endure stressful off-host periods and perform as vectors of a diversity of infectious agents, thus engaging pathways that expectedly demand for autophagy. Little is known of ticks' autophagy, a conserved eukaryotic machinery assisting in homeostasis processes that also participates in tissue-dependent metabolic functions. Here, the autophagy-related ATG4 (autophagin-1), ATG6 (beclin-1) and ATG8 (LC3) mRNAs from the human diseases vector Amblyomma sculptum and the cattle-tick Rhipicephalus microplus were identified. Comparative qPCR quantifications evidenced different transcriptional status for the ATG genes in the salivary glands (SG), ovaries and intestines of actively feeding ticks. These ATGs had increased relative transcription under nutrient-deprivation, as determined by validation tests with R. microplus embryo-derivative cells BME26 and A. sculptum SG explants incubations in HBSS. Starvation lead to 4-31.8× and ~ 60-500× increments on the ATGs mRNA loads in BME26 and A. sculptum SG explants, respectively. PI3K inhibitor 3MA treatment also affected ATGs expression in BME26. Some ATGs were more transcribed in the SGs than in the ovaries of cattle-ticks. Amblyomma sculptum/R. microplus interspecific comparisons showed that ATG4 and ATG6 were 0.18× less expressed in A. sculptum SGs, but ~ 10-100× more expressed in their ovaries when compared to R. microplus organs. ATG4 and ATG8a transcript loads were ~ 120× and ~ 40× higher, respectively, in A. sculptum intestines when compared to cattle-ticks of similar weight category. ATGs expression in A. sculptum intestines increased with tick weight, indicating Atgs contribution to intracellular blood digestion. Possible roles of the autophagy machinery and their organ-specific expression profile on vector biology are discussed.
Assuntos
Proteínas de Artrópodes/genética , Autofagia/genética , Ixodidae/fisiologia , Animais , Proteínas de Artrópodes/metabolismo , Feminino , Ixodidae/genética , Ixodidae/crescimento & desenvolvimento , Larva/crescimento & desenvolvimento , Larva/fisiologia , Especificidade de Órgãos , Óvulo/fisiologia , Rhipicephalus/genética , Rhipicephalus/crescimento & desenvolvimento , Rhipicephalus/fisiologia , Transcrição GênicaRESUMO
BACKGROUND: Amblyomma cajennense is the main vector of Rickettsia rickettsii which causes Brazilian spotted fever. This adult tick preferably infests horses and capybaras, but has low host specificity during its immature stages, thus posing a threat to humans and dogs. In this study, the efficacy of sarolaner (Simparic™/Simparica®, Zoetis) when administered once orally to dogs at 2 mg/kg was evaluated against induced infestations of A. cajennense nymphs for up to 35 days after treatment. METHODS: Based on pretreatment tick counts, 20 dogs were randomly allocated to treatment with sarolaner (Simparic™) dosed at 2 mg/kg of body weight or a placebo on Day 0 of the study. Artificial infestations were performed using laboratory raised A. cajennense nymphs on study days -2, 5, 12, 19, 26 and 33. Efficacy was determined at 48 h post-treatment or post-infestation at each time point relative to the counts for dogs that received placebo. RESULTS: There were no adverse reactions to treatment. A single dose of sarolaner (Simparic™) provided 100% efficacy on study days 2, 7 and 14; and ≥ 99.6% on days 21, 28 and 35. Geometric mean live tick counts for sarolaner were significantly lower than those for placebo on all days (P < 0.0001). CONCLUSIONS: Under the conditions of the present study, sarolaner (Simparic™) administered once orally at 2 mg/kg provided 100% efficacy against existing infestations and ≥ 99.6% efficacy within 48 h against weekly challenges of A. cajennense for at least 35 days after treatment.
Assuntos
Vetores Aracnídeos/efeitos dos fármacos , Azetidinas/uso terapêutico , Doenças do Cão/tratamento farmacológico , Ixodidae/efeitos dos fármacos , Compostos de Espiro/uso terapêutico , Infestações por Carrapato/veterinária , Administração Oral , Animais , Vetores Aracnídeos/fisiologia , Azetidinas/administração & dosagem , Azetidinas/efeitos adversos , Brasil , Doenças do Cão/parasitologia , Cães , Ixodidae/fisiologia , Ninfa/efeitos dos fármacos , Ninfa/fisiologia , Carga Parasitária , Febre Maculosa das Montanhas Rochosas/transmissão , Compostos de Espiro/administração & dosagem , Compostos de Espiro/efeitos adversos , Infestações por Carrapato/tratamento farmacológico , Infestações por Carrapato/parasitologia , Fatores de Tempo , Resultado do TratamentoRESUMO
Amblyomma sculptum (Ixodida: Ixodidae) Berlese, 1888 is the most important tick vector in Brazil, transmitting the bioagent of the most severe form of spotted fever (SF) in part of the Cerrado (in the states of Minas Gerais and São Paulo). In another part of the Cerrado (Central-West region of Brazil), a milder form of SF has been recorded. However, neither the rickettsia nor the vector involved have been characterized. The aim of the current study was to analyse genetic variation and the presence of rickettsia in A. sculptum in Cerrado, from silent areas and with the milder form of SF. Samples were subjected to DNA extraction, amplification and sequencing of 12S rDNA, cytochrome oxidase subunit II and D-loop mitochondrial genes (for tick population analyses), and gltA, htrA, ompA and gene D (sca4) genes for rickettsia researches. Exclusive haplotypes with low frequencies, high haplotype diversity and low nucleotide diversity, star-shaped networks and significant results in neutrality tests indicate A. sculptum population expansions in some areas. Rickettsia amblyommatis, Candidatus Rickettsia andeanae and Rickettsia felis were detected. The A. sculptum diversity is not geographically, or biome delimited, pointing to a different potential in vector capacity, possibly associated with differing tick genetic profiles.
Assuntos
Variação Genética , Ixodidae/genética , Rickettsia/genética , Animais , Proteínas de Artrópodes/genética , Proteínas de Bactérias/genética , Brasil , Complexo IV da Cadeia de Transporte de Elétrons/genética , Feminino , Pradaria , Haplótipos , Ixodidae/crescimento & desenvolvimento , Ixodidae/microbiologia , Masculino , Proteínas Mitocondriais , Ninfa/genética , Ninfa/crescimento & desenvolvimento , Ninfa/microbiologia , Filogenia , RNA Ribossômico/genética , Rickettsia/classificação , Análise de Sequência de DNARESUMO
Rhipicephalus sanguineus sensu lato and Amblyomma sculptum can parasite humans and domestic animals and are vectors of pathogens, including zoonoses. Repellents are an important tool of tick control. This study aimed to compare the efficacy of N,N-diethyl- 3-methylbenzamide (DEET), a standard repellent, versus ß-citronellol in a Petri dish bioassay. A semicircle of filter paper (31.8cm2) was treated with 87µl of one of four concentrations (0.200, 0.100, 0.050 and 0.025mg/cm2) of ß-citronellol, DEET or solvent (ethanol). A head-to-head test was developed treating one side with increasing concentrations of ß-citronellol as above mentioned, against the highest concentration of DEET. Besides that a blank assay was performed. Three males and three females were placed in the middle of the plate and their location was evaluated 5, 10 and 30min after the test was initiated. As a result, the time had no significant effect on repellency response of the ticks exposed to both compounds and their concentrations. The repellency response raised according with the increase of concentration. Additionally, our findings indicate that the tick A. sculptum was more sensitive to the compounds tested and ß-citronellol showed a higher efficacy than DEET. In addition, ß-citronellol could be formulated to protect humans and other animals from R. sanguineus s. l. and A. sculptum infestation, as well as the diseases transmitted by these species.
Assuntos
DEET/farmacologia , Repelentes de Insetos/farmacologia , Ixodidae/efeitos dos fármacos , Monoterpenos/farmacologia , Monoterpenos Acíclicos , AnimaisRESUMO
Brazilian spotted fever (BSF) is a tick-borne disease caused by the bacterium Rickettsia rickettsii, the deadliest spotted fever of the world, transmitted in southeastern Brazil mainly by the tick Amblyomma sculptum, a member of the Amblyomma cajennense species complex. In the present study, over 5000 adults of A. sculptum ticks were collected by dry ice traps in the Municipal Ecological Park, alongside the Pampulha Lake region, a BSF-endemic area of Belo Horizonte city, state of Minas Gerais, southeastern Brazil. Ticks were taken alive to the laboratory, where a sample of 2100 specimens was processed for isolation of R. rickettsii. For this purpose, ticks were macerated and intraperitoneally inoculated into guinea pigs. Only one out of 21 inoculated guinea pigs presented high fever within 21days post inoculation with tick homogenates. This febrile animal was euthanized and its internal organs were macerated and inoculated into additional guinea pigs (guinea pig passage). A spleen sample from a febrile guinea pig was used to inoculate Vero cells, resulting in a successful isolation and in vitro establishment of rickettsiae. Rickettsia-infected Vero cells were used for molecular characterization of the rickettsial isolate through PCR and DNA sequencing of fragments of three rickettsial genes (gltA, ompA, and ompB), which were all 100% identical to corresponding sequences of R. rickettsii from GenBank. The present R. rickettsii isolate was designated as strain Pampulha. A minimal infection rate of 0.05% R. rickettsii-infected ticks was estimated for A. sculptum population of the Pampulha Lake region. Our results, coupled with epidemiological evidences, suggest that R. rickettsii strain Pampulha, isolated from A. sculptum ticks in the present study, is the strain responsible for human clinical cases of BSF in the Pampulha Lake region of Belo Horizonte city.
RESUMO
BACKGROUND: Rickettsia rickettsii is vectored by ticks, and some vertebrate hosts can be sources of infection to ticks during bacteremic periods. In Brazil, the main vector for R. rickettsii is the tick Amblyomma sculptum, a member of the A. cajennense complex. Horses, in turn, are one of the major hosts for A. sculptum. In this study, horses experimentally infected with R. rickettsii were assessed for clinical changes and their capability to transmit the infection to A. sculptum ticks. METHODS: Four horses were infected with R. rickettsii through either intraperitoneal injection or infestation with R. rickettsii-infected A. sculptum ticks. Simultaneously, the animals were infested with non-infected A. sculptum ticks. The horses were monitored for 30 days by clinical examination, hematological and biochemical tests, real-time PCR of blood for the detection of Rickettsia, and inoculation of blood in guinea pigs. IgG antibody titers were followed until the horses have shown seronegativity or until the end of the experiment. Uninfected ticks that fed on horses were subjected to real-time PCR and/or were fed on susceptible rabbits. RESULTS: The horses showed no clinical, hematological or blood biochemical alterations, and bacteremia was not detected by real-time PCR or by inoculation of horse blood into guinea pigs. Anti-R. rickettsii antibodies were detected in horses from 10 days to 2 years after infection. Uninfected ticks, after feeding on infected horses, showed 2.1 % positivity in real-time PCR, but failed to transmit the infection to rabbits at a next feeding stage. CONCLUSIONS: Rickettsia rickettsii-infected horses did not manifest illness and are not competent amplifier hosts of R. rickettsii for A. sculptum ticks.
Assuntos
Doenças dos Cavalos/microbiologia , Rickettsia rickettsii , Febre Maculosa das Montanhas Rochosas/veterinária , Animais , Anticorpos Antibacterianos/sangue , Cobaias , Doenças dos Cavalos/sangue , Cavalos , Ixodidae/microbiologia , Coelhos , Febre Maculosa das Montanhas Rochosas/sangue , Febre Maculosa das Montanhas Rochosas/microbiologia , Fatores de TempoRESUMO
Amblyomma sculptum (Ixodida: Ixodidae) Berlese, 1888, a member of the Amblyomma cajennense complex, is the major vector of Brazilian spotted fever (BSF) in southeastern Brazil. In this study, the genetic diversity of A. sculptum populations in the state of Rio de Janeiro (RJ), Brazil, was investigated because genetic variability in tick populations may be related to vector competence. Samples of A. sculptum from 19 municipalities in 7 regions of RJ were subjected to DNA extraction, amplification and sequencing of D-loop, cytochrome oxidase II and 12S rDNA mitochondrial genes. These sequences were used to map the genetic diversity of this tick. Amblyomma sculptum populations are genetically diverse in RJ, especially in the South Centre and Highland regions. Few unique haplotypes were observed in all populations, and the majority of genetic variation found was among ticks within each population. Phylogenetic reconstruction reinforced the assumption that all the haplotypes identified in RJ belong to A. sculptum. However, some RJ haplotypes are closer to A. sculptum from Argentina than to A. sculptum from elsewhere in Brazil. In RJ, A. sculptum has high genetic diversity, although little genetic differentiation. Observations also indicated a high level of gene flow among the studied populations and no evidence of population structure according to region in RJ.
Assuntos
Doenças Endêmicas , Haplótipos , Ixodidae/genética , Febre Maculosa das Montanhas Rochosas/epidemiologia , Animais , Proteínas de Artrópodes/genética , Brasil/epidemiologia , Complexo IV da Cadeia de Transporte de Elétrons/genética , Feminino , Genes Mitocondriais , Ixodidae/crescimento & desenvolvimento , Larva/genética , Larva/crescimento & desenvolvimento , Masculino , Ninfa/genética , Ninfa/crescimento & desenvolvimento , Filogenia , Filogeografia , RNA Ribossômico/genética , Febre Maculosa das Montanhas Rochosas/microbiologia , Análise de Sequência de DNARESUMO
Up to some years ago, the taxon Amblyomma cajennense represented a single tick species in the New World, from southern United States to northern Argentina. Recent studies, based on genetic, reproductive and morphological data reorganized this taxon into a complex of the following 6 valid species: A. cajennense sensu stricto, Amblyomma mixtum, Amblyomma sculptum, Amblyomma interandinum, Amblyomma tonelliae, and Amblyomma patinoi. According to this classification, the A. cajennense complex is currently represented in Colombia by only one species, A. patinoi. Because the Colombian land is surrounded by confirmed records of A. mixtum in Panama and Ecuador, and by A. cajennense s.s. in Venezuela and the Brazilian Amazon, it is possible that these two species could also occur in Colombia. This study aimed to determine the occurrence of ticks of the A. cajennense complex in the Orinoquía region of Colombia. A total of 246 adult ticks of the Amblyomma genus were collected in three sampled regions: 71 females and 110 males in Arauca (Arauca Department), 27 females and 20 males in Nunchía (Casanare Department), and 10 females and 8 males in Yopal (Casanare Department). Based on morphological and molecular analyses, these ticks were identified as A. mixtum. Molecular analyses consisted of DNA sequences of two molecular markers, the nuclear second internal transcribed spacer (ITS2) and the mitochondrial cytochrome c oxidase subunit I gene (COI). The presence of A. mixtum in Colombia is of medical relevance, since this species is incriminated as a vector of Rickettsia rickettsii in Central America.