RESUMO
BACKGROUND: This study describes the effectiveness of a novel active pharmaceutical ingredient, fluralaner (isoxazoline class), against important ectoparasites infesting cattle in Brazil. METHODS: A total of 13 studies involving a 5% fluralaner-based pour-on formulation (Exzolt 5%; further referred to as Exzolt) were conducted. Specifically, the effectiveness of this formulation was studied against Rhipicephalus microplus (6 studies), Cochliomyia hominivorax larvae (4 studies), Dermatobia hominis larvae (1 study) and Haematobia irritans flies (2 studies). RESULTS: The therapeutic efficacy of Exzolt was found to exceed 98% at 4 days post treatment (DPT), while persistent efficacy (> 90% efficacy) against repeated infestations of R. microplus was observed for up to 79 DPT. In field studies, ≥ 98% therapeutic efficacy was demonstrated at all study sites by 7 DPT, and a persistent efficacy (> 90% efficacy) was observed for 42, 49 or 56 DPT. Exzolt prevented C. hominivorax eggs from developing to the larval stage, thus mitigating the development of myiasis in cattle naturally and artificially infested with this screworm. The efficacy of Exzolt against D. hominis larvae was 98% at 3 DPT, while persistent efficacy (> 90% effectiveness) was found to last for up to 70 DPT. Against H. irritans, Exzolt showed therapeutic efficacy (≥ 90%) within the first day of treatment at both study sites, while persistent efficacy (≥ 90%) was observed for 7 DPT at one site and for 21 DPT at the other site. CONCLUSIONS: Overall, the results from these studies confirm that Exzolt is therapeutically efficacious against the most important ectoparasites infesting cattle in Brazil. The novel active pharmaceutical ingredient, fluralaner, provides a new treatment option for farmers to control cattle ectoparasites, especially where there is resistance to other chemical classes. In addition, an effective control of ectoparasites will improve overall cattle health and well-being as well as production.
Assuntos
Doenças dos Bovinos , Muscidae , Infestações por Carrapato , Animais , Bovinos , Brasil/epidemiologia , Óvulo , Larva , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/prevenção & controle , Doenças dos Bovinos/parasitologia , Preparações Farmacêuticas , Infestações por Carrapato/tratamento farmacológico , Infestações por Carrapato/prevenção & controle , Infestações por Carrapato/veterináriaRESUMO
Data regarding parasitemia (blood smears), rectal temperature (RT), packed cell volume (PCV) and vaginal mucosa coloration (VMC) of Gyr x Holstein female calves between 3-7mo were accessed to evaluate different techniques for monitoring the bovine tick fever agents (TFA). The 1st experiment determined the correlation between the TFA parasitemia with RT and PCV. The 2nd, evaluated the associated risk of A. marginale parasitemia with RT and PCV in relation to the Gyr/Holstein genetic proportion (5/8,3/4,7/8 and 15/16) using Receiver Operating Characteristic Curve (ROC). The 3rd, two groups were performed: cattle monitored by RT (T01) and by PCV (T02), during their 80-210 days of age, data regarding TFA parasitemia, RT, PCV, VMC and weight were registered. In 1st experiment, RT showed weak correlation with TFA parasitemia, while PCV showed a strong correlation with A. marginale and B. bigemina, but not with B. bovis parasitemia. In experiment 2, the ROC curve analysis showed that when the genetic proportion of B. t. taurus increased, least reliable RT was to monitor calves infected with A. marginale. The PCV for monitoring A. marginale was the best technique, showing sensitivity of 74.2% and specificity of 97.0% than other techniques that used RT and VCM as a monitoring tool. In general, calves monitored by PCV (T02) showed higher PCV values, lower A. marginale parasitemia, less pneumonia as co-infection and less salvation treatment were performed than in animals monitored by RT (T01). Furthermore, animals from T02 gained 23.5 kg more than those from T01. The low frequency of B. bovis and B. bigemina found in this study made impossible to compare the monitoring techniques for these pathogenic agents.
Assuntos
Anaplasmose , Babesia , Babesiose , Doenças dos Bovinos , Carrapatos , Animais , Babesia/genética , Bovinos , Doenças dos Bovinos/diagnóstico , Feminino , Parasitemia/veterináriaRESUMO
Amitraz is one of the most used acaricides for the control of ticks of domestic animals, however, extensive use of this active ingredient has favored the development of resistant populations of Rhipicephalus microplus worldwide. The possible mechanisms of metabolic and/or target-site alterations mechanisms of amitraz resistance were investigated in a Brazilian field population of R. microplus (São Gabriel strain). Bioassays with the synergists piperonylbutoxide, triphenylphosphate and diethyl-maleate were used to evaluate the metabolic mechanisms involved. Target-site insensitivity was investigated by amplification and sequencing of a fragment of the octopamine/tyramine (OCT/TYR) receptor gene. Piperonylbutoxide synergism (synergism ratio = 2.8) indicated the participation of the P450 pathway in the detoxification of amitraz. Previously reported single nucleotide polymorphisms that confer amino acid changes in the OCT/TYR receptor, threonine to proline (T8P) and leucine to serine (L22S), were found in the amitraz-resistant strain but not in the susceptible reference strain. The results suggest that amitraz resistance in the studied strain is multi-factorial and may result from cytochrome P450 detoxification and mutations in octopamine receptors.
Assuntos
Acaricidas/farmacologia , Resistência a Medicamentos , Rhipicephalus/efeitos dos fármacos , Toluidinas/farmacologia , Animais , Brasil , FemininoRESUMO
Anaplasma marginale is the causative agent of the severe bovine anaplasmosis. The tick Rhipicephalus microplus is one of the main vectors of A. marginale in tropical and subtropical regions of the world. After the tick bite, the bacterium invades and proliferates within the bovine erythrocytes leading to anemia, impairment of milk production and weight loss. In addition, infection can cause abortion and high mortality in areas of enzootic instability. Immunization with live and inactivated vaccines are employed to control acute bovine anaplasmosis. However, they do not prevent persistent infection. Consequently, infected animals, even if immunized, are still reservoirs of the bacterium and contribute to its dissemination. Antimicrobials are largely employed for the prophylaxis of bovine anaplasmosis. However, they are often used in sublethal doses which may select pre-existing resistant bacteria and induce genetic or phenotypic variations. Therefore, we propose a new standardized in vitro assay to evaluate the susceptibility of A. marginale strains to different antimicrobials. This tool will help health professionals to choose the more adequate treatment for each herd which will prevent the selection and spread of resistant strains. For that, we initially evaluated the antimicrobial susceptibility of two field isolates of A. marginale (Jaboticabal and Palmeira) infecting bovines. The least susceptible strain (Jaboticabal) was used for the standardization of an antimicrobial assay using a culture of Ixodes scapularis-derived tick cell line, ISE6. Results showed that enrofloxacin (ENRO) at 0.25, 1 or 4 µg/mL and oxytetracycline (OTC) at 4 or 16 µg/mL are the most efficient treatments, followed by OTC at 1 µg/mL and imidocarb dipropionate (IMD) at 1 or 4 µg/mL. In addition, this proposed tool has technical advantages compared to the previously established bovine erythrocyte culture. Thereby, it may be used to guide cattle farmers to the correct use of antimicrobials. The choice of the most suitable antimicrobial is essential to eliminate persistent infections, prevent the spread of resistant strains and help controlling of bovine anaplasmosis.
Assuntos
Anaplasma marginale/efeitos dos fármacos , Anaplasmose/prevenção & controle , Antibacterianos/farmacologia , Vetores Aracnídeos/citologia , Doenças dos Bovinos/prevenção & controle , Rhipicephalus/citologia , Anaplasmose/tratamento farmacológico , Anaplasmose/microbiologia , Animais , Antibacterianos/uso terapêutico , Vetores Aracnídeos/parasitologia , Brasil , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/microbiologia , Linhagem Celular , Enrofloxacina/farmacologia , Eritrócitos/microbiologia , Imidocarbo/análogos & derivados , Imidocarbo/farmacologia , Imidocarbo/uso terapêutico , Masculino , Testes de Sensibilidade Microbiana , Oxitetraciclina/farmacologia , Oxitetraciclina/uso terapêutico , Reação em Cadeia da Polimerase em Tempo Real , Rhipicephalus/parasitologiaRESUMO
Anaplasmosis is one of the most prevalent tick-borne diseases of cattle caused by Anaplasma marginale. MSP1a surface protein has been shown to be involved in eliciting immunity to infected cattle. Carbon nanotubes (CNTs) has been increasingly highlighted due to their needle like structure, which contain multiple attachment sites for biomolecules and may interact with or cross biological membranes, increasing antigen availability to immune system. Here, we have successfully designed a nanocomplex of a synthetic peptide noncovalently attached to multiwalled CNT (MWCNT). Peptide comprising the core motif of the MSP1a was efficiently adsorb onto the nanoparticle surface. The MWCNT-Am1 nanocomplex exhibited high stability and good dispersibility and in vivo immunization showed high levels of IgG1 and IgG2a, followed by increased expression of pro-inflammatory and anti-inflammatory cytokines. This is a proof-of-concept of a nanovaccine that was able to generate a strong immune response compared to the common antigen-adjuvant vaccine without the nanoparticles.
Assuntos
Anaplasmose/imunologia , Antígenos de Bactérias/imunologia , Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/imunologia , Nanotubos de Carbono/química , Células Th1/imunologia , Células Th2/imunologia , Anaplasma/imunologia , Anaplasma/patogenicidade , Anaplasmose/prevenção & controle , Animais , Antígenos de Bactérias/química , Sobrevivência Celular/efeitos dos fármacos , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Feminino , Camundongos , Camundongos Endogâmicos BALB C , Reação em Cadeia da PolimeraseRESUMO
Rhipicephalus sanguineus sensu stricto (s.s.), the temperate lineage of the brown dog tick, is the most common tick found on dogs from urban areas in Rio Grande do Sul (RS) state, southern Brazil. Chemical treatments against ticks are important to control this pest, but can lead to selection for acaricide resistance. Unfortunately, little is known about acaricide resistance in this tick species in Brazil, although such information is very important to companion animal clinical practice. The objective of this study was to analyze acaricide susceptibility of R. sanguineus s.s. from the metropolitan area of Porto Alegre, RS. Engorged females ticks were collected in ten different locations, from naturally infested dogs or the environment (homes, shelters and kennels). The progenies were used in toxicological larval tests with deltamethrin, fipronil and ivermectin. Mortality data was used to determine the median lethal concentrations (LC50) for each tick population and resistance was characterized based on relative susceptibility of the different tick populations against each acaricide. Seven samples were considered resistant to deltamethrin, with resistance ratios (RR) ranging from 2.32 to 5.67. From five tick populations tested with fipronil, three were considered resistant, with RR varying from 2.56 to 13.83. For ivermectin, resistance ratios were lower, ranging from 1.54 to 2.97. The results reveal a notable variance of susceptibility to deltamethrin, fipronil and ivermectin in the R. sanguineus s.s. populations studied. This study documents for the first time the existence of acaricide-resistant populations of R. sanguineus s.s. in Brazil.
Assuntos
Acaricidas/farmacologia , Resistência a Medicamentos , Ivermectina/farmacologia , Nitrilas/farmacologia , Pirazóis/farmacologia , Piretrinas/farmacologia , Rhipicephalus sanguineus/efeitos dos fármacos , Animais , Brasil , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Rhipicephalus sanguineus/crescimento & desenvolvimentoRESUMO
Spotted fever (SF) is a tick-borne disease associated with Rickettsia spp.. In the Pampa biome, Southern Brazil, cases of SF seem to be strongly linked with the practice of hunting wild animals. An investigation of rickettsiae in tick species found on wild animals could provide more information regarding the rickettsiosis enzootic cycle. The aim of this study is to describe the results of a molecular survey of Rickettsia spp. in the Neotropical deer tick, Haemaphysalis juxtakochi Cooley, 1946 (Acari: Ixodidae), from the Brazilian Pampa. Ticks were obtained from 14 road-killed gray brocket deer, Mazama gouazoubira (Artiodactyla: Cervidae), found in nine different municipalities of Rio Grande do Sul state, Southern Brazil. Ticks were processed individually to obtain genomic DNA, and then Rickettsia spp. was investigated using a set of PCR reactions that amplified the rickettsial fragments of the gltA, ompA, and htrA genes. Of the 24 tick samples tested, DNA of Rickettsia parkeri sensu stricto (s.s.) was found in 11 H. juxtakochi specimens collected in two different areas of the Brazilian Pampa. This is the first report of R. parkeri s.s. (the main agent associated with SF in the Uruguayan, Argentinian, and Brazilian Pampa) in H. juxtakochi ticks. These findings indicate that R. parkeri s.s. may be much more common and widely distributed in the Pampa biome than previously assumed. Moreover, H. juxtakochi ticks and gray brocket deer could participate in the potential spillover of R. parkeri s.s. from endemic to non-endemic areas in the South American Pampa.
Assuntos
Cervos/parasitologia , Ixodes/microbiologia , Rickettsia/isolamento & purificação , Animais , Animais Selvagens/parasitologia , Brasil/epidemiologia , Reservatórios de Doenças/microbiologia , Ixodes/genética , Reação em Cadeia da Polimerase , Rickettsia/classificação , Rickettsia/genética , Rickettsia/fisiologia , Inquéritos e QuestionáriosRESUMO
A anaplasmose bovina é uma das principais causas de perdas produtivas e mortes no Rio Grande do Sul em rebanhos bovinos. O Anaplasma marginale é o principal agente causador da enfermidade e provoca hipertermia, anemia, prostração, abortos e perdas produtivas nos bovinos acometidos. Tendo em vista o controle deste hemoparasita em uma propriedade leiteira localizada no município de Eldorado do Sul no Rio Grande do Sul, na qual a incidência da doença era alta, 471 animais foram imunizados com Anaplasma centrale na busca de desenvolvimento cruzado para Anaplasma marginale. No experimento foi verificado que a incidência que normalmente era acima de 30% na propriedade passou para níveis inferiores a 5%. No entanto, foram verificados abortos decorrentes da imunização, principalmente nos animais que possuíam menos de 90 dias de prenhes. Já o número de mortes globais na fazenda caiu consideravelmente tendo em vista que a principal causa de morte era a anaplasmose bovina. Dos animais inoculados com A. centrale em torno de 15% apresentaram sintomatologia clínica da enfermidade e precisaram ser tratados com oxitetraciclina no período entre 15 e 30 dias após a imunização. O custo com tratamento empregado na propriedade posterior à imunização caiu em torno de 85% o que provocou impacto significativo economicamente na propriedade.(AU)
Bovine anaplasmosis is a major cause of production losses and deaths in Rio Grande do Sul cattle herds. Anaplasma sp. is the main causative agent of cattle disease. It causes hyperthermia, anemia, prostration, abortions and reduces milk production in affected animals. In order to control this hemoparasite on a dairy farm located in the municipality of Eldorado do Sul in Rio Grande do Sul, where the disease incidence was high, 471 animals were immunized with Anaplasma centrale in the search for cross-protectiv immunity for Anaplasma marginale. The property anaplasmosis incidence, which usually was above 30%, became 5% after the immunization. However, abortions were observed resulting from innoculaition, especially in animals that had less than 90 days of pregnancy. The global number of deaths on the farm dropped considerably given that the main cause of death was the bovine anaplasmosis. 15% of animals inoculated with A. centrale showed clinical symptoms of the disease between 15 and 30 days after immunization and had to be treated with oxytetracycline. The amount of money spent with anaplasmosis treatment decay 85% after the immunization, which caused significant economic impact on the property.(AU)
Assuntos
Animais , Bovinos , Anaplasma centrale/isolamento & purificação , Anaplasmose/terapiaRESUMO
More than seventy tick species have been reported in Brazil. Despite the emergence of tick-borne diseases in Neotropical region, there are still limited data available on tick species parasitizing humans in Brazil. Rio Grande do Sul is the southernmost state of Brazil, comprising the only part of Brazilian territory inside the Pampa biome, as well as the transition between subtropical and temperate zones. Here, we report on human parasitism by ticks in Rio Grande do Sul state between 2004 and 2017. Seventy cases of human parasitism by ticks were recorded, with a total of 81 tick specimens collected. These included 11 tick species belonging to three genera of Ixodidae (hard-ticks), Amblyomma, Haemaphysalis and Rhipicephalus; and one genus of Argasidae, Ornithodoros. The most prevalent tick species associated to cases of human parasitism were Amblyomma parkeri (24%), Rhipicephalus sanguineus sensu lato (22%), Amblyomma aureolatum (15%) and Amblyomma ovale (12%). A spatial analysis showed two major hot spots of human parasitism by ticks in Rio Grande do Sul state. The findings of this study highlight the need for permanent monitoring of human parasitism by ticks in order to provide a better understanding of tick and tick-borne disease eco-epidemiology, and the early identification of potential cases of tick-borne diseases, particularly in spotted fever endemic regions.
Assuntos
Ixodidae/fisiologia , Infestações por Carrapato/epidemiologia , Carrapatos/fisiologia , Animais , Argasidae/fisiologia , Brasil/epidemiologia , Humanos , Ornithodoros/fisiologia , Rhipicephalus/fisiologia , Rhipicephalus sanguineus/fisiologia , Análise Espacial , Rickettsiose do Grupo da Febre Maculosa/epidemiologia , Doenças Transmitidas por Carrapatos/epidemiologia , Carrapatos/classificaçãoRESUMO
Entomopathogenic fungi, such as Metarhizium anisopliae, for the control of arthropods, have been studied for more than 20 years. The aim of this study was to determine the best methodology to evaluate the in vitro effect of the fungus M. anisopliae on Rhipicephalus microplus tick larvae. We compared a modified Larval Packet Test (LPT) and a Larval Immersion Test (LIT). For the LPT filter papers were impregnated with 1 mL of M. anisopliae suspension in Triton X-100 at 0.02%, in concentrations of 106, 107 and 108 conidia/mL and subsequently folded to include the larval ticks. LIT was performed by immersing the larvae in M. anisopliae suspensions for 5 min using the same three concentrations, then the larvae were placed on filter paper clips. For LPT, the LT50 values obtained were 134.6, 27.2 and 24.8 days for concentrations of 106, 107 and 108 conidia/mL; and the mortality after 21 days was 17.3, 17.6 and 38%, respectively. The LT50 values of LIT were 24.5, 20 and 9.2 days with mortality after 21 days of 50.5, 64.7 and 98% for 106, 107 and 108 conidia/mL, respectively. For the same conidia concentration, LIT showed a higher mortality in a shorter time interval when compared with LPT. These differences between the methods tested must be taking into account in further screening and effect studies with M. anisopliae. The set of results shown here could optimize the protocol used to identify M. anisopliae strains pathogenic against R. microplus.
Assuntos
Larva/microbiologia , Metarhizium/fisiologia , Controle Biológico de Vetores/métodos , Rhipicephalus/microbiologia , Controle de Ácaros e Carrapatos/métodos , Animais , Esporos Fúngicos/fisiologiaRESUMO
Borrelia burgdorferi sensu lato (s.l.) complex includes the agents of Lyme disease/borreliosis in North America, Europe, and Asia, such Borrelia burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii, Borrelia bavariensis, Borrelia spielmanii, Borrelia bissettiae, and Borrelia mayonii. In 2013 B. burgdorferi s.l. was reported for the first time in the Neotropical region, from Ixodes aragaoi ticks in Uruguayan Pampa. In addition, from 2011 to 2016, 17 suspected human cases of borreliosis-like syndrome were reported in Rio Grande do Sul (RS) state, Brazil, which contains only part of country in the Pampa biome. The goal of this work is to report the results of a state surveillance program conducted in order to investigate the presence of B. burgdorferi s.l. in its classic vector, Ixodes spp. ticks, from the Brazilian Pampa. For this, we searched for Ixodes spp. ticks in 307 rodents from 11 municipalities of RS state. We then tested the ticks for the presence of B. burgdorferi s.l. DNA using PCR analysis. Of 35 Ixodes spp. ticks tested, one larva and one nymph of Ixodes longiscutatus ticks tested positive for Borrelia sp. DNA. The phylogenetic analysis of the flaB fragment grouped our samples (referred as Borrelia sp. haplotype Pampa) into B. burgdorferi s.l. group in a particular branch with other South American haplotypes, and this group was close to Borrelia carolinensis, B. bissettiae, and Borrelia californiensis. This is the first evidence of B. burgdorferi s.l. circulation in ticks of the genus Ixodes in Brazil. These results highlight the need for the implementation of public health policies for the diagnosis and prevention of potential cases of human borreliosis in Brazil. Further studies are needed to fill the gaps in our knowledge of the distribution, pathogenicity, reservoirs, and vectors of these emerging South American B. burgdorferi s.l. haplotypes.
Assuntos
Grupo Borrelia Burgdorferi/isolamento & purificação , Ixodes/microbiologia , Animais , Grupo Borrelia Burgdorferi/classificação , Grupo Borrelia Burgdorferi/genética , Brasil , Monitoramento Epidemiológico , Feminino , Flagelina/análise , Ixodes/crescimento & desenvolvimento , Larva/crescimento & desenvolvimento , Larva/microbiologia , Ninfa/crescimento & desenvolvimento , Ninfa/microbiologia , Filogenia , Análise de Sequência de DNARESUMO
Louse flies or deer keds, Lipoptena spp., are widespread in Neotropical cervids, but the vector-borne pathogens of louse flies had only been previously reported in the Northern hemisphere. This is the first report of Bartonella spp. in deer louse flies (Lipoptena mazamae) in the neotropics collected from gray brocket deer ( Mazama gouazoubira ) in Southern Brazil. DNA from Bartonella sp. was detected in all 429 L. mazamae collected from 11 road-killed gray brocket deer. The same sequences of DNA of Bartonella spp. were identified in samples. Gray brocket deer are abundant in Brazil, so Bartonella-infected Lipoptena spp. may be widely distributed in the neotropics.
Assuntos
Bartonella/isolamento & purificação , Cervos/parasitologia , Dípteros/microbiologia , Animais , Bartonella/genética , DNA Bacteriano/genética , FilogeniaRESUMO
Spotted fever is an acute febrile illness, which is considered severely underreported and misdiagnosed in the Brazilian Pampa, caused by tick-borne Rickettsiae. Here, we report an eco-epidemiological investigation of Rickettsia spp. in ticks from a spotted fever focus in Toropi, southern Brazil. Ticks were collected from capybara carcasses and processed individually to obtain genomic DNA. Rickettsia was investigated using PCR that amplified the rickettsial fragments of the gltA, ompA and htrA genes. DNA from Rickettsia parkeri was found in four of 14 Amblyomma dubitatum ticks collected from capybara carcasses in Toropi and the nearby municipality of Quevedos. We also tested 210A. dubitatum ticks obtained from road-killed capybaras of other localities from the Pampa biome; none of them were positive for Rickettsiae. Thus, in Rio Grande do Sul, two Rickettsia species can be potentially associated to spotted fever: Rickettsia sp. strain Atlantic Rainforest, associated with Amblyomma ovale ticks in the Atlantic Rainforest biome, and R. parkeri, associated both with Amblyomma tigrinum and A. dubitatum ticks in the Pampa biome. Our results reinforce that R. parkeri may be the agent associated with spotted fever in the Brazilian Pampa.
Assuntos
Ixodidae/microbiologia , Rickettsia/classificação , Febre Maculosa das Montanhas Rochosas/epidemiologia , Animais , Brasil/epidemiologia , Ecossistema , Reação em Cadeia da Polimerase , Rickettsia/isolamento & purificação , Febre Maculosa das Montanhas Rochosas/microbiologia , Carrapatos/microbiologiaRESUMO
Acaricide resistance is a major obstacle to the control of Rhipicephalus microplus. Historically, the indiscriminate use of chemical compounds has contributed to the selection of populations resistant to different classes of acaricides. Therefore, multiple acaricide resistance is an important threat to the chemical control of the cattle tick. To investigate the occurrence and extent of multiple resistance to acaricides in Southern Brazil we performed larval tests with cypermethrin, chlorpyriphos, amitraz, fipronil and ivermectin on 104 cattle tick field samples from different ranches in Rio Grande do Sul, between the years 2013 and 2015. Adult immersion tests with a commercial formulation mixture of chlorpyriphos and cypermethrin were performed on 75 samples. Four levels of resistance were established according to the mortality of larvae: Level I: mortality between 82% and 95%; Level II: mortality between 57% and 82%; Level III: mortality between 25% and 57%; and Level IV: mortality lower than 25%. Resistance to cypermethrin was detected in 98.08% of the samples evaluated, mostly at resistance level IV. The frequency of samples resistant to amitraz, chlorpyriphos, ivermectin and fipronil was 76.92%, 60.58%, 60.58% and 53.85% respectively. Multiple resistance to three or more compounds was found in 78.85% of the samples. The results obtained in this study are alarming and reveal a new scenario for the challenge of tick control using chemicals. This is an issue of high importance to cattle production systems where this tick is responsible for a high economic impact.
Assuntos
Acaricidas/farmacologia , Resistência a Inseticidas , Rhipicephalus/efeitos dos fármacos , Animais , Bioensaio , Brasil , Larva/efeitos dos fármacosRESUMO
The filamentous fungus Metarhizium anisopliae is an arthropod pathogen used in the biological control of pests in agriculture and livestock. The effect of the fungus M. anisopliae on ticks has been shown in experiments in vitro. The aim of the present study was to compare the susceptibility of different field isolates of Rhipicephalus microplus to M. anisopliae. A total of 67 field isolates were evaluated. Rhipicephalus microplus larvae were immersed in an M. anisopliae suspension (108 conidia/mL) for 5min. The median lethal times (LT50) ranged from 2.6 to 24.9days. Mortality observed at the 15th day after treatment ranged from 26.3 to 100% in the tested samples. The effect of M. anisopliae on tick isolates was not associated with their susceptibility to any acaricide tested, animal stocking rate, cattle breed, rotational grazing, cultivated pasture, production system, presence of wet areas or biome. The integration of livestock and agriculture practices in the farm and the frequency of acaricide treatment seem to be associated with tick susceptibility to M. anisopliae. These results demonstrated that field populations of R. microplus show a high variation in their susceptibility to M. anisopliae.
Assuntos
Metarhizium/fisiologia , Rhipicephalus/microbiologia , Acaricidas/farmacologia , Animais , Interações Hospedeiro-Patógeno , Resistência a Inseticidas , Larva , Controle Biológico de Vetores , Rhipicephalus/classificação , Rhipicephalus/efeitos dos fármacosRESUMO
"Candidatus Rickettsia asemboensis" is an obligate intracellular bacterium of the Rickettsiales order, genetically related to species belonging to the Rickettsia felis group, agents of flea-borne spotted fever. Here we report for the first time the detection of "Ca. R. asemboensis", a flea-associated organism, in Rhipicephalus sanguineus ticks. It is the first occurrence of this emerging bacterium in Brazil, which increases the geographical distribution of this R. felis-like agent.
Assuntos
Cães/parasitologia , Rhipicephalus sanguineus/microbiologia , Rickettsia felis/isolamento & purificação , Animais , Brasil/epidemiologia , DNA Bacteriano/isolamento & purificação , Rickettsia felis/genética , Sifonápteros/microbiologiaAssuntos
Rickettsia , Rickettsiose do Grupo da Febre Maculosa/epidemiologia , Rickettsiose do Grupo da Febre Maculosa/microbiologia , Animais , Brasil/epidemiologia , História do Século XXI , Humanos , Vigilância da População , Rickettsia/classificação , Rickettsia/genética , Rickettsia/isolamento & purificação , Rickettsiose do Grupo da Febre Maculosa/história , Rickettsiose do Grupo da Febre Maculosa/transmissão , Carrapatos/microbiologiaRESUMO
ORNITHODOROS BRASILIENSIS: Aragão is an endemic tick restricted to the highlands of the state of Rio Grande do Sul, Brazil. This species is very aggressive toward humans, causing fever, great pain and intense inflammatory response at the bite site. It is also very aggressive toward dogs, and tick toxicosis syndrome has been reported in this host. In order to elucidate the biology of this tick, the present study describes its life cycle under laboratory conditions, using guinea pigs as hosts for two generations. In the nonparasitic phase, the ticks were maintained in sand, in an incubator under controlled conditions. The larvae molted to the nymphal stage without feeding, and five nymphal stages (N1, N2, N3, N4 and N5) were observed in both generations. In both generations emergence of adults started from N3 when sex ratio was 0.85:1 (23 males and 27 females) in F1 and 0.63:1 (34 males and 54 females) in F2. For both generations, N4 generated more females, while N5 only produced females. The pre-ecdysis period of the nymphs ranged from 31.1 to 38.6 days. Two gonotrophic cycles were observed, and the first one presented a higher average number of eggs deposited (N=139) than the second (N=73.8). The mean duration of the life cycle (egg to egg) of O. brasiliensis was 215.4 days for the first generation and 195 days for the second.
Assuntos
Estágios do Ciclo de Vida , Ornithodoros/fisiologia , Animais , Brasil , Feminino , Cobaias , Laboratórios , Larva/fisiologia , Masculino , Fatores de TempoRESUMO
The efficacy of the fungus Metarhizium anisopliae to control ticks has been shown in several in vitro experiments. However, few studies have been undertaken in field conditions in order to demonstrate the applicability of its use as a biological control of ticks and its combination with chemical acaricides. The aim of the present study was to evaluate the efficacy of M. anisopliae to control an acaricide-resistant strain of Rhipicephalus microplus under laboratory and field conditions. First, the compatibility of M. anisopliae strain (TIS-BR03) with commercial acaricides and its potential to control the cattle tick were evaluated in vitro. In general, acaricide treatments had mild effects on fungus viability. In the field experiment, the median of treatment efficacy with acaricide only, M. anisopliae only and combination of M. anisopliae with acaricide were 71.1%, 56.3% and 97.9%, respectively. There is no statistical difference between groups treated with M. anisopliae and acaricide alone. Thus, in this work we have demonstrated the applicability of M. anisopliae use associated or not with chemical acaricides on field conditions in order to control an acaricide-resistant strain of the cattle tick R. microplus.
Assuntos
Acaricidas/uso terapêutico , Doenças dos Bovinos/terapia , Resistência a Medicamentos , Metarhizium/fisiologia , Rhipicephalus/microbiologia , Controle de Ácaros e Carrapatos , Infestações por Carrapato/veterinária , Acaricidas/farmacologia , Animais , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Clorpirifos/farmacologia , Clorpirifos/uso terapêutico , Feminino , Piretrinas/farmacologia , Piretrinas/uso terapêutico , Rhipicephalus/efeitos dos fármacos , Infestações por Carrapato/tratamento farmacológico , Infestações por Carrapato/terapia , Resultado do TratamentoRESUMO
The profitability of livestock activities can be diminished significantly by the effects of parasites. Economic losses caused by cattle parasites in Brazil were estimated on an annual basis, considering the total number of animals at risk and the potential detrimental effects of parasitism on cattle productivity. Estimates in U.S. dollars (USD) were based on reported yield losses among untreated animals and reflected some of the effects of parasitic diseases. Relevant parasites that affect cattle productivity in Brazil, and their economic impact in USD billions include: gastrointestinal nematodes - $7.11; cattle tick (Rhipicephalus (Boophilus) microplus) - $3.24; horn fly (Haematobia irritans) - $2.56; cattle grub (Dermatobia hominis) - $0.38; New World screwworm fly (Cochliomyia hominivorax) - $0.34; and stable fly (Stomoxys calcitrans) - $0.34. The combined annual economic loss due to internal and external parasites of cattle in Brazil considered here was estimated to be at least USD 13.96 billion. These findings are discussed in the context of methodologies and research that are required in order to improve the accuracy of these economic impact assessments. This information needs to be taken into consideration when developing sustainable policies for mitigating the impact of parasitism on the profitability of Brazilian cattle producers.