Search

This study aimed to evaluate the combination effect of Heterorhabditis bacteriophora HP88 and H. indica LPP1, with the acaricides deltamethrin, amitraz and chlorfenvinphos, and the essential oil (EO) of Lippia triplinervis, against engorged females of Rhipicephalus microplus. In order to verify the effect of acaricides and EO, the adult immersion test was used, and in the groups treated only with entomopathogenic nematodes (EPNs), 150 infective juveniles were used per female. In the treatments with nematodes in combination with the acaricides or EO, the females were immersed in the solutions (acaricide or EO) and then transferred to Petri dishes for application of the nematodes. The treatment with acaricides resulted in a control percentage lower than 70%, except in the group treated with chlorfenvinphos in the second experiment (84.3%). The control percentage was 73% for L. triplinervis EO, and greater than 90% in all the groups treated with nematodes. For treatments with EPNs combined with the acaricides or EO, the efficacy was greater than 95% (except for deltamethrin + HP88), and reached 100% in the treatment with LPP1 + amitraz. It can be concluded that the EPNs at the concentrations tested were compatible with the acaricides deltamethrin, amitraz and chlorfenvinphos, and with the EO of L. triplinervis. These combinations enhance the effect of these control agents., (Copyright © 2020. Published by Elsevier B.V.)

The present study evaluated, in the laboratory, the virulence of Heterorhabditis bacteriophora LPP30 against engorged females of Rhipicephalus microplus; in addition, we evaluated, in semi-field tests, the effects of four isolates of Heterorhabditis spp. (i.e., H. bacteriophora HP88, Heterorhabditis baujardi LPP7, Heterorhabditis indica LPP1 and H. bacteriophora LPP30) in insect cadaver formulation against the non-parasitic phase of R. microplus. In the first experiment (in vitro), engorged females were exposed, in Petri dish, to H. bacteriophora LPP30 at 75, 150, 300, 600, 1200 and 2400 nematodes/tick (10 ticks per concentration tested). In the second experiment (semi-field), five engorged females and four cadavers of Galleria mellonella infected with nematodes were placed in pots with soil and grown Brachiaria decumbens; the pots were hold outdoor, exposed to natural environment conditions during the tests. In the third experiment (semi-field), 65 days after the cadavers had been placed in the pots for the second experiment, new engorged females (five per pot) were placed in the pots of the groups treated with H. bacteriophora HP88 or H. baujardi LPP7, to assess their persistence in the soil. In the first test, the percent control was higher than 95% in all treatment groups. In the second experiment, at day 22, the mean mortality rate was 78% in the groups treated with H. bacteriophora LPP30 or H. indica LPP1, and reached 100% and 98% when treated with H. bacteriophora HP88 and H. baujardi LPP7, respectively. In this experiment, the egg-laying inhibition index was higher than 90% in the groups treated with H. bacteriophora HP88 (97.2%) or H. baujardi LPP7 (91.9%). In the third experiment with H. bacteriophora HP88 and H. baujardi LPP7, the egg-laying inhibition index was 59.1% and 43.1%, respectively. We concluded that the isolate LPP30 was highly virulent under laboratory conditions, whereas in semi-field tests, HP88 and LPP7 were the most effective isolates. Moreover, HP88 and LPP7 remained active against engorged females of R. microplus in the soil for 65 days after application of EPN-infected cadavers of G. mellonella., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

The acaricidal activity of combinations of thymol, carvacrol and eugenol was evaluated on larvae and engorged females of the cattle tick Rhipicephalus microplus. The first step assessed the compounds separately, in concentrations of 3.125, 6.25, 12.5 and 25 mg/mL. Then tests were performed with the compounds combined in the ratio of 1:1 at concentrations of 3.125 and 6.25 mg/mL, along with the control group treated with the solvent (3% DMSO). In the second step, combinations were tested incorporated in a formulation at the concentration de 6.25 mg/mL, using the larval packet and adult immersion tests. The associations carvacrol + thymol (3.125 mg/mL), carvacrol + eugenol and thymol + eugenol (6.25 mg/mL) presented synergism, while the other associations had an additive effect. In the experiments with formulation, all combinations caused 100% larval mortality, but the efficacy was under 15% against engorged females. Therefore, the combinations of thymol + carvacrol (3.125 mg/mL) as well as carvacrol + eugenol and eugenol + thymol (6.25 mg/mL) had a synergistic effect on engorged females, but when incorporated in the formulation, the acaricide activity was strong against larvae but weak against engorged females., (Published by Elsevier Inc.)

This work aimed to investigate candidate biological control agents against the cattle tick Rhipicephalus microplus by studying three entomopathogenic nematodes (EPN) isolates from two species, Heterorhabditis bacteriophora (isolates LPP30 and HP88) and Heterorhabditis baujardi (isolate LPP7). The study comprised the pharmacotechnical development of four test formulations, and their biological evaluation, in three stages: 1) selection of the fittest EPN isolate at 16 ± 1 °C after 120 h of incorporation in the formulations; 2) determination of the effects of temperature and incubation time on the survival of the selected isolate in formulations; 3) evaluation of the in vitro efficacy (infectivity) of the selected EPN formulations and their components against R. microplus females after 72 h exposure. H. baujardi LPP7 presented the highest survival rates in 0.1% carboxymethyl cellulose sodium (CMC) formulations (100% at 25 °C, up to 10 days after incorporation). At the highest tested temperature (34.2 °C), 54% of LPP7 survived for up to 72 h in CMC formulations. The infectivity of LPP7-containing formulation against R. microplus was 99%, reducing oviposition, egg production index and larval hatching. Considering the pressing need for safer acaricide products, incorporation of EPNs in pharmaceutical formulations is presented as a promising approach for the biological control of cattle tick infestations, potentially reducing environmental impact and resistance development associated with chemical acaricides., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Rhipicephalus (Boophilus) microplus is the main cattle ectoparasite in tropical areas. Gir × Holstein crossbred cows are well adapted to different production systems in Brazil. In this context, we performed genome-wide association study (GWAS) and post-GWAS analyses for R. microplus resistance in an experimental Gir × Holstein F 2 population. Single nucleotide polymorphisms (SNP) identified in GWAS were used to build gene networks and to investigate the breed of origin for its alleles. Tick artificial infestations were performed during the dry and rainy seasons. Illumina BovineSNP50 BeadChip (Illumina Inc., San Diego, CA) and single-step BLUP procedure was used for GWAS. Post-GWAS analyses were performed by gene ontology terms enrichment and gene transcription factors networks, generated from enriched transcription factors, identified from the promoter sequences of selected gene sets. The genetic origin of marker alleles in the F 2 population was assigned using the breed of origin of alleles approach. Heritability estimates for tick counts were 0.40 ± 0.11 in the rainy season and 0.54 ± 0.11 in the dry season. The top ten 0.5-Mbp windows with the highest percentage of genetic variance explained by SNP markers were found in chromosomes 10 and 23 for both the dry and rainy seasons. Gene network analyses allowed the identification of genes involved with biological processes relevant to immune system functions (TREM1, TREM2, and CD83). Gene-transcription factors network allowed the identification of genes involved with immune functions (MYO5A, TREML1, and PRSS16). In resistant animals, the average proportion of animals showing significant SNPs with paternal and maternal alleles originated from Gir breed was 44.8% whereas the proportion of animals with both paternal and maternal alleles originated from Holstein breed was 11.3%. Susceptible animals showing both paternal and maternal alleles originated from Holstein breed represented 44.6% on average, whereas both paternal and maternal alleles originated from Gir breed animals represented 9.3%. This study allowed us to identify candidate genes for tick resistance in Gir × Holstein crossbreds in both rainy and dry seasons. According to the origin of alleles analysis, we found that most animals classified as resistant showed 2 alleles from Gir breed, while the susceptible ones showed alleles from Holstein. Based on these results, the identified genes may be thoroughly investigated in additional experiments aiming to validate their effects on tick resistance phenotype in cattle., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

This study evaluated the efficacy of four entomopathogenic nematode (EPN) strains in insect cadaver formulations against Rhipicephalus microplus and compared the efficacy of the most virulent EPNs applied in cadavers of Galleria mellonella and Tenebrio molitor. In the first experiment, infected G. mellonela larvae were used as the source of EPNs. Engorged females of R. microplus were placed in pots filled with soil and different numbers of G. mellonella larvae infected with one of four species of nematodes. All treatments with EPNs of the genus Heterorhabditis caused significant reduction (p<0.05) in the egg mass weight and hatching percentage of larvae. The EPNs of the genus Steinernema, except for the group exposed to Steinernema carpocapsae ALL, whose source nematodes included six larvae of G. mellonella, caused a significant reduction (p<0.05) in the egg mass weight produced per female. Steinernema feltiae SN applied with two, four, and six cadavers and S. carpocapsae ALL with two cadavers caused a reduction in hatching percentage of larvae of R. microplus (p<0.05). The percentage of control was above 95% in all groups treated with Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 and in the treatment with four larvae infected with S. feltiae SN. The second experiment followed the same methodology, using G. mellonella and T. molitor larvae infected by the two most virulent EPNs. H. bacteriophora HP88 and H. indica LPP1 in different formulations caused reduction in the egg mass weight and hatching percentage of larvae. The percentage of control were 82.4 and 84.9% for H. bacteriophora HP88 and H. indica LPP1, respectively, formulated in T. molitor, and reaching 99.9% in groups formulated with G. mellonella. The EPNs tested in insect cadaver formulation showed pathogenicity to engorged females of R. microplus and EPNs of the genus Heterorhabditis formulated in G. mellonella larvae were more effective., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In vitro effect of the association of the entomopathogenic nematodes Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 with the essential oil of Lippia sidoides on engorged females of Rhipicephalus microplus was assessed. Engorged females with homogeneous weights (p >0.05) were divided into six groups of ten ticks each (each female = an experimental unit). In the treated groups, the ticks were exposed to the oil (40 μl/ml=4%) and nematodes (300 entomopathogenic nematodes (EPNs/tick) separately and also to the nematodes together with the oil, while in the control group, the females were immersed in Tween 80 (3%). All the treatments caused a significant reduction in the egg mass weight (p <0.05). The hatching percentage of larvae was reduced (p <0.05) in the groups treated with H. bacteriophora HP88, H. indica LPP1, and H. bacteriophora HP88 associated with the oil, but in the group treated only with the oil, the hatching of percentage of larvae rate was similar to that of the control group (p >0.05). The percentage of control in the group exposed only to the oil was 50.7%, while in the other treated groups, the percentage of control was greater than 95 %, reaching 100 %in the group treated with H. indica LPP1 associated with the oil. The results of the L. sidoides essential oil in the concentrations tested in association with both H. bacteriophora HP88 and H. indica LPP1 indicate that these combinations can be used to control R. microplus.

The monitoring of resistance of cattle tick populations in Brazil to the chemical bases in use is largely limited to investigation of the phenotypic profile. There are few studies investigating the role played by the genotypic profile in acaricide resistance in the country. Therefore, the aim of the present study was to carry out molecular characterization and trace out the genetic profile of populations of Rhipicephalus microplus with respect to resistance to the organophosphate and pyrethroid chemical groups. For that purpose, larvae were genotyped belonging to 587 populations for pyrethroids and 306 for organophosphates, using the polymerase chain reaction technique. It was found that 75.49% and 97.44% of the larvae studied showed resistance to the organophosphates and pyrethroids, respectively. Among the populations resistant to pyrethroids, 91.9% were heterozygotes, showing that most of the resistant populations have only one allele responsible for resistance. Therefore, it is possible to conclude that the genotyped populations have high resistance to organophosphates, and even more so to pyrethroids. This information is fundamental for understanding the mechanisms of resistance of R. microplus to acaricides, to enable improvement of control techniques., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The aim of this study was to assess the influence of different exposure times of engorged female the Rhipicephalus microplus to infective juveniles of Heterorhabditis bacteriophora isolate HP88. The engorged females were divided into seven groups (six treatments and one control) of 20 ticks each with statistically similar average weights (p>0.05) and exposed to concentrations of 300 nematodes/tick for periods of 3, 6, 12, 24, 48 and 72 h. The following biological parameters were monitored: pre-oviposition period; egg mass weight; hatching percentage; and efficacy of treatment. There was no influence of the exposure time on the pre-oviposition period (p>0.05), while there were significant differences (p<0.05) between the groups exposed for 24, 48 and 72 h and the control group with respect to the egg mass weight, and 24h for hatching percentage. Treatment efficacy reached 100% after exposure for 48 and 72 h. These results demonstrate that infective juveniles of H. bacteriophora HP88, under laboratory conditions, interfere in the majority of the biological parameters of the non-parasitic phase of engorged R. microplus females when the exposure time is greater than or equal to 24h., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Tick resistance in cattle is mainly found in zebu (Bos indicus) animals, although it is also present in some taurine (B. taurus) breeds. In order to characterize functional genes involved in tick resistance/susceptibility in cattle, two cDNA libraries were generated using skin tissues of selected Holstein x Gyr animals. A total of 2700 high-quality reads from both resistant and susceptible cDNA were assembled into 458 sequences (contigs) and 834 singletons, with a mean size of 447.7 nucleotides. Assignment of homologous proteins by BLASTX revealed 790 (61.1%) and 300 (23.2%) hits in resistant and susceptible cDNA, respectively; 121 of these hits matched bovine proteins. A total of 502 (38.9%) unique sequences were found to have no significant homology with known sequences and were classified as novel sequences. In general, the most abundant sequences consisted of those coding for hypothetical proteins whose function had not yet been determined, in addition to ribosomal proteins, binding proteins and structural proteins, such as keratin and collagen. The most abundant protein found was collagen type III alpha, although ribosomal proteins accounted for half of the 40 most frequent hits. In addition, five matches within the top 40 best hits corresponded to immune response proteins. These sequences could be used for future studies on functional genomics of cattle tick resistance as well as for genomic sequencing projects.

One hundred semi-systematized interviews were applied with the aim of surveying the perceptions of milk producers in the municipality of Divinópolis, Minas Gerais regarding the biology of the tick Rhipicephalus (Boophilus) microplus. Content analysis was conducted on each of the variables surveyed and their descriptions, highlighting the higher frequencies in order to construct profiles of perceptions about each of the matters surveyed. In addition, each of the producers was categorized regarding their readiness to proceed with efficient control, from the assessment of their responses. Among the variables surveyed were the tick lifespan, duration of parasitic life, time of greatest incidence, survival in pastures and egg-laying volume. These questions are considered important for defining the knowledge needed for rational combat. It was concluded that the information needed for adopting effective practices to combat ticks was insufficient among the milk farm properties in Divinópolis. Moreover, the producers interviewed had a good perception of what they observed in their daily routine, but did not have complementary information about the tick life cycle.

Semi-systematized interviews were conducted with 100 dairy cattle producers in the municipality of Divinópolis, Minas Gerais, with the aim of ascertaining their perceptions regarding the importance of Rhipicephalus (Boophilus) microplus and of combating it. Content analysis was performed and the frequency distribution of each of the variables was used to construct profiles of the producers interviewed. The production losses caused by ticks were perceived incompletely by the producers, who were unaware of the pathogen transmission caused by the parasite and the indirect losses through combating it, such as the cost of acaricide and labor. The combat operations were performed in a traditional manner, with an excessive number of inefficient treatments that aimed to control the level of infestation at that moment. The quality of the acaricide dipping/spraying applied was affected by the quality of the equipment used to apply the products, lack of knowledge of the mode of action of these products, lack of the specific information needed and lack of motivation caused by unawareness of the disadvantages of chemical combat. It was concluded that the lack of knowledge about combat methods and the acceptance of endemicity of the parasitosis were impediments to changing the realities encountered.

The objective of the present work was to evaluate the efficacy of a non-sulphur-based homeopathic preparation and a sulphur-containing natural product derived from Allium sativum (Linnaeus) against infestation by the cattle tick Rhipicephalus (Boophilus) microplus (Canestrini) (Acari: Ixodidae). A total of 24 crossbred calves (7 : 8 Holstein : Zebu), aged 6-8 months and maintained in individual stables under tick-free conditions, were divided into three groups. Group 1 (control group) received no treatment; Group 2 was treated with 0.01 g/day of the homeopathic preparation Fator C&MC(®), and Group 3 was treated with 20 g/day of Enxofre-Allium sativum(®). After adaptation to the diet for 1 month, each calf was subjected to artificial infestation with 8000 R. (B.) microplus larvae (aged 7-14 days) twice per week over a 5-month period. Numbers of engorged females were recorded every 14 days and samples of freely released engorged females were collected at 14-day intervals commencing 3 months after the start of the experiment. The engorged females were weighed, incubated for 15 days under biochemical oxygen demand conditions at 27 ± 1 °C and relative humidity >85%, and the weights of the egg masses produced were recorded. Other biological parameters, including reproduction estimate, reduction in oviposition and efficiency of treatment, were determined. A significant reduction in the number of engorged females was detected on animals treated with Enxofre-Allium sativum(®) (Group 3) in comparison with the other two groups. The overall efficiency of the treatment with the sulphur-containing product was 64%, whereas that of the homeopathic preparation was 26%. Under the experimental conditions established, Enxofre-Allium sativum(®) can reduce the intensity of the R. (B.) microplus infestation., (Medical and Veterinary Entomology © 2010 The Royal Entomological Society. No claim to original US government works.)

The use of a concentrate emulsion of Melia azedarach green fruits and a suspension of the fungus Beauveria bassiana was evaluated in the control of Rhipicephalus microplus on artificially infested cattle. The evaluation was conducted following the protocol established by the Brazilian Agriculture Ministry. Five groups of 4 or 5 animals were allocated to one of the following treatments: emulsion concentrate of M. azedarach at 0.25% (T AZED 0.25%), emulsion concentrate of M. azedarach at 0.5% (T AZED 0.5%), B. bassiana at 2.4 × 10(8) conidia (T BASS), association of the concentrate of M. azedarach at 0.25% with B. bassiana at 2.4 × 10(8) conidia (T AZED 0.25%+BASS), and control (untreated). The association of the two compounds provided better results than any one isolated treatment, indicating compatibility or perhaps a synergy between M. azedarach and B. bassiana. This treatment resulted in fewer engorged females (129 ± 70) than in the control group (233 ± 82), showing high performance against all developmental stages of the tick. Results revealed an apparent synergistic effect of M. azedarach and B. bassiana in the control of R. microplus that should be further investigated., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The bovine tick Rhipicephalus (Boophilus) microplus causes major losses in cattle production systems in tropical regions. Bos indicus breeds are more resistant to ticks than B. taurus breeds. Resistance genes could be an alternative to control this parasite. We examined the pattern of gene expression of three calcium-binding-protein genes: translationally controlled tumor protein 1 (TPT1), allergen Bos d3 (S100A7), calcium channel protein transient receptor potential vanilloid 6 (TRPV6), and the cysteine proteinase inhibitor gene (CST6). These genes were selected from cDNA libraries prepared from skin biopsies taken from resistant and susceptible Gyr x Holstein F₂ animals. These biopsies were also used to study the expression level of these genes through real-time PCR analysis. The relative expression levels of the S100A7, TPT1, TRPV6, and CST6 genes were 2.01 ± 0.6, 1.32 ± 0.9, 1.53 ± 1.2, and 2.03 ± 0.7 times higher in the susceptible group, respectively. Skin lesion tissue from the susceptible animals showed significantly more mRNA transcripts of these genes in comparison with the resistant animals (P = 0.001). However, this hypersensitivity does not seem to protect the susceptible animals against tick infestation.

The objective of this work was to evaluate the effect of different concentrations of the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora strain HP88 on the biological parameters of the non-parasite phase of engorged females of the cattle tick Rhipicephalus (Boophilus) microplus. Six groups were formed, each containing 20 engorged females, which were exposed to the following concentrations of infective juveniles of this nematode: 0, 75, 150, 300, 600 and 1200 EPNs/female, respectively. The following biological parameters were observed: female weight before oviposition, egg mass weight, pre-oviposition period, oviposition period, survival period, hatching percentage, egg production index (%EPI), nutritional index (%NI) and efficacy of treatment. There were no statistically significant differences in the female weight before the oviposition and pre-oviposition period (p>0.05) between the groups. The nematode action caused significant alterations (p<0.01) in the egg mass weight, oviposition period, survival period, hatching percentage, %EPI and %NI between the treated groups and the control group. Treatment efficacy was higher than 90% in all groups, reaching 99% at a dosage of 1200 EPNs/female. The present study demonstrates that under laboratory conditions, H. bacteriophora HP88 has a deleterious effect on the majority of the parameters of the non-parasitic phase of engorged R. (B.) microplus females, making this species a potential biological control agent of cattle ticks., ((c) 2010. Published by Elsevier B.V. All rights reserved.)

The aim of this study was to evaluate the influence of different doses of Heterorhabditis amazonensis RSC-5 on the biological parameters of engorged females of Rhipicephalus (Boophilus) microplus. The female ticks, individually identified, were divided into six groups of 20 each and exposed to the following nematode concentrations: 0, 75, 150, 300, 600, and 1,200/female. The following parameters were observed: initial weight, final weight, alteration weight, egg mass weight, pre-oviposition period, oviposition period, survival period, incubation period, hatching percentage, reproductive efficiency index (REI), nutritional efficiency index (NI), and percentage of control. There were no significant differences observed for the initial weight, pre-oviposition period, incubation period, and NI (p > 0.05) between the various treated groups and the control group. However, there were significant differences (p < 0.01) for the oviposition and survival periods between all the treated groups and the control group. For the final weight, alteration weight, egg mass weight, and REI, only the treatment with 1,200 nematode/female did not differ significantly from the respective figures for the control group (p > 0.05). The highest control rate was 67.8%, obtained in the treatment with a concentration of 300 entomopathogenic nematodes/female. The results demonstrate that this nematode has a deleterious effect on the majority of the biological parameters analyzed.

There have been studies of the compatibility between entomopathogenic nematodes and insecticides commonly used to control crop pests, but this same approach has not been widely studied regarding the control of ticks. Therefore, this work examines the association between a species of entomopathogenic nematode, Steinernema glaseri, and an organophosphate acaricide to control the cattle tick Rhipicephalus microplus. Engorged females were separated into 12 groups, with ten repetitions each, immersed for 5 min in varied concentrations of acaricide (commercial dose and one-half, one-fourth, one-eighth and one-sixteenth of that dose), associated or not with the nematodes, maintained under controlled conditions. There were two control groups, one containing nematodes and water and the other only water. The absence of egg laying and significant reduction in the survival period of the females in the nematode treatments associated with the lowest acaricide doses demonstrated the compatibility between the two agents. We observed the presence of S. glaseri adults on the cuticle of the females in the treatments with one-eighth and one-sixteenth the commercial dose. These results indicate greater efficacy of the treatments with lower acaricide concentrations in association with S. glaseri, with less environmental impact, reduced costs and less resistance selection pressure on the tick populations.

Differences in domestication and selection processes have contributed to considerable phenotypic and genotypic differences between Bos taurus and Bos indicus cattle breeds. Of particular interest in tropical and subtropical production environments are those genetic differences between subspecies that underlie the phenotypic extremes in tolerance and susceptibility to parasite infection. In general, B. taurus cattle are more susceptible to ectoparasites than B. indicus cattle in tropical environments, and much of this difference is under genetic control. To identify genomic regions involved in tick resistance, we developed a B. taurus x B. indicus F(2) experimental population to map quantitative trait loci (QTL) for resistance to the Riphicephalus (Boophilus) microplus tick. About 300 individuals were measured for parasite load in two seasons (rainy and dry) and genotyped for 23 microsatellite markers covering chromosomes 5, 7 and 14. We mapped a suggestive chromosome-wide QTL for tick load in the rainy season (P < 0.05) on chromosome 5. For the dry season, suggestive (P < 0.10) chromosome-wide QTL were mapped on chromosomes 7 and 14. The additive effect of the QTL on chromosome 14 corresponds to 3.18% of the total observed phenotypic variance. Our QTL-mapping study has identified different genomic regions controlling tick resistance; these QTL were dependent upon the season in which the ticks were counted, suggesting that the QTL in question may depend on environmental factors.