Tick Resistance Research Articles

MRNA vaccination induces tick resistance and prevents transmission of the Lyme disease agent.

Ixodes scapularis ticks transmit many pathogens that cause human disease, including Borrelia burgdorferi. Acquired resistance to I. scapularis due to repeated tick exposure has the potential to prevent tick-borne infectious diseases, and salivary proteins have been postulated to contribute to this process. We examined the ability of lipid nanoparticle–containing nucleoside-modified mRNAs encoding 19 I. scapularis salivary proteins (19ISP) to enhance the recognition of a tick bite and diminish I. scapularis engorgement on a host and thereby prevent B. burgdorferi infection. Guinea pigs were immunized with a 19ISP mRNA vaccine and subsequently challenged with I. scapularis. Animals administered 19ISP developed erythema at the bite site shortly after ticks began to attach, and these ticks fed poorly, marked by early detachment and decreased engorgement weights. 19ISP immunization also impeded B. burgdorferi transmission in the guinea pigs. The effective induction of local redness early after I. scapularis attachment and the inability of the ticks to take a normal blood meal suggest that 19ISP may be used either alone or in conjunction with traditional pathogen-based vaccines for the prevention of Lyme disease, and potentially other tick-borne infections.

Evaluation of acaricidal resistance status of Rhipicephalus microplus ticks from the hilly state (Uttarakhand) of India and evaluation of efficacy of a natural formulation for the management of resistant ticks.

The resistance status against deltamethrin, cypermethrin, coumaphos and ivermectin was assessed of Rhipicephalus microplus from five districts of Uttarakhand, through adult immersion test and larval packet test. The field isolates were highly resistant to deltamethrin (median resistance ratio [RR50] = 9.10-29.13-fold) followed by cypermethrin (2.23-3.55). Surprisingly the isolates were susceptible to coumaphos (0.34-3.17). Emerging resistance against ivermectin (1.55-3.27) was also observed in all the isolates. Elevated levels of esterases (enzyme ratio = 2.93-5.84-fold), glutathione S-transferases (5.10-10.06) and monooxygenases (1.68-4.02) in resistant fields isolates were highly correlated (47.4-86.0%) with the resistant factor (RR50) determined by bioassay. All the isolates except Uttarkashi possess mutation at the 190th position in domain II of the sodium channel gene. As a mitigation strategy an Ageratum conyzoides-based characterized natural formulation was tested against all the isolates and was found effective at the concentration of 10.1-11.5%. The possibility of using the natural formulation for the management of multi-acaricide resistant ticks is discussed.

From Bench to Field: A Guide to Formulating and Evaluating Anti-Tick Vaccines Delving beyond Efficacy to Effectiveness.

Ticks are ubiquitous blood-sucking ectoparasites capable of transmitting a wide range of pathogens such as bacteria, viruses, protozoa, and fungi to animals and humans. Although the use of chemicals (acaricides) is the predominant method of tick-control, there are increasing incidents of acaricide tick resistance. Furthermore, there are concerns over accumulation of acaricide residues in meat, milk and in the environment. Therefore, alternative methods of tick-control have been proposed, of which anti-tick cattle vaccination is regarded as sustainable and user-friendly. Over the years, tremendous progress has been made in identifying and evaluating novel candidate tick vaccines, yet none of them have reached the global market. Until now, Bm86-based vaccines (Gavac™ in Cuba and TickGARDPLUS™ Australia-ceased in 2010) are still the only globally commercialized anti-tick vaccines. In contrast to Bm86, often, the novel candidate anti-tick vaccines show a lower protection efficacy. Why is this so? In response, herein, the potential bottlenecks to formulating efficacious anti-tick vaccines are examined. Aside from Bm86, the effectiveness of other anti-tick vaccines is rarely assessed. So, how can the researchers assess anti-tick vaccine effectiveness before field application? The approaches that are currently used to determine anti-tick vaccine efficacy are re-examined in this review. In addition, a model is proposed to aid in assessing anti-tick vaccine effectiveness. Finally, based on the principles for the development of general veterinary vaccines, a pipeline is proposed to guide in the development of anti-tick vaccines.

Identification of loci associated with pathological outcomes in Holstein cattle infected with Mycobacterium avium subsp. paratuberculosis using whole-genome sequence data

Bovine paratuberculosis (PTB), caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic granulomatous enteritis that affects cattle worldwide. According to their severity and extension, PTB-associated histological lesions have been classified into the following groups; focal, multifocal, and diffuse. It is unknown whether these lesions represent sequential stages or divergent outcomes. In the current study, the associations between host genetic and pathology were explored by genotyping 813 Spanish Holstein cows with no visible lesions (N = 373) and with focal (N = 371), multifocal (N = 33), and diffuse (N = 33) lesions in gut tissues and regional lymph nodes. DNA from peripheral blood samples of these animals was genotyped with the bovine EuroG MD Bead Chip, and the corresponding genotypes were imputed to whole-genome sequencing (WGS) data using the 1000 Bull genomes reference population. A genome-wide association study (GWAS) was performed using the WGS data and the presence or absence of each type of histological lesion in a case–control approach. A total of 192 and 92 single nucleotide polymorphisms (SNPs) defining 13 and 9 distinct quantitative trait loci (QTLs) were highly-associated (P ≤ 5 × 10−7) with the multifocal (heritability = 0.075) and the diffuse (heritability = 0.189) lesions, respectively. No overlap was seen in the SNPs controlling these distinct pathological outcomes. The identified QTLs overlapped with some QTLs previously associated with PTB susceptibility, bovine tuberculosis susceptibility, clinical mastitis, somatic cell score, bovine respiratory disease susceptibility, tick resistance, IgG level, and length of productive life. Pathway analysis with candidate genes overlapping the identified QTLs revealed a significant enrichment of the keratinization pathway and cholesterol metabolism in the animals with multifocal and diffuse lesions, respectively. To test whether the enrichment of SNP variants in candidate genes involved in the cholesterol metabolism was associated with the diffuse lesions; the levels of total cholesterol were measured in plasma samples of cattle with focal, multifocal, or diffuse lesions or with no visible lesions. Our results showed reduced levels of plasma cholesterol in cattle with diffuse lesions. Taken together, our findings suggested that the variation in MAP-associated pathological outcomes might be, in part, genetically determined and indicative of distinct host responses.

Successive treatments with ivermectin (3.15%) to control the tick Rhipicephalus (Boophilus) microplus in cattle: Pharmacokinetic and efficacy assessment

This study aimed to evaluate the pharmacokinetics, the potential accumulation in the body of treated animals and the efficacy of ivermectin long-acting formulation (3.15%) against the cattle tick Rhipicephalus (Boophilus) microplus in a scheme of three successive treatments. Fifteen 12-month-old heifers, naturally infested with R. microplus, were divided into two groups (G). Cattle from GI (n = 10) were subjected to three treatments with ivermectin 3.15% (IVOMEC GOLD®, Merial Argentina S.A.) at a rate of 1 mL/50 kg on days 0, 35, and 70. Cattle from GII (n = 5) were not treated. From day 1 to 202 post-treatment blood samples were taken to measure ivermectin concentrations by HPLC and female ticks (4.5–8 mm) were counted to evaluate the efficacy of the treatment. The level of tick resistance to ivermectin was evaluated before and after finishing the scheme of successive treatments by larval immersion test (LIT) bioassay from engorged females collected from GI. The area under the concentration vs. time curves (AUC0–35d) obtained post-second treatment was 1.51 ± 0.39-fold higher than those observed post-first treatment (P<0.05). The mean plasma concentrations of ivermectin 3.15% at 20 days after the first, second and third treatment were 17.0, 27.5 and 37.8 ng/mL, respectively (P<0.01). The elimination half-life of ivermectin post-third treatment was significantly longer than that was previously reported after a single dose (P<0.01). Values of therapeutic efficacy percentage reached 75.6% post-first treatment and between 95.9 and 100% after the second treatment. Ticks evaluated by LIT showed a significant increase in lethal concentrations after treatments. Although the efficacy level was high, the successive treatments with long-acting ivermectin formulation generate a significant accumulation of drug in plasma and could increase the levels of resistance to this drug in the tick population.

Comparative susceptibility of Rhipicephalus microplus collected from the northern state of India to coumaphos, malathion, deltamethrin, ivermectin, and fipronil.

The chemical-based tick management method is gradually losing its clutch due to the establishment of resistant ticks. For development of region-specific tick management strategies, the present study was aimed to evaluate the comparative resistance profile ofRhipicephalus microplusisolates collected from seven districts of Uttar Pradesh, a northern state of India. Comparative analysis of the dose-response data using adult immersion test (AIT) against coumaphos, malathion, deltamethrin, ivermectin, and fipronil revealed that all the isolates were resistant to discriminating concentration of deltamethrin having LC50of 295.12-436.52ppm with a resistance ratio of 22.02-32.58. An emerging low level of ivermectin resistance (resistance ratio, RR50 = 1.03-2.26) with LC50 in the range of 22.39-48.98ppm was found across the isolates. The coumaphos was highly effective against all except Amethi (AMT) isolate. Similarly, malathion was efficacious against most of the isolates except Pratapgarh (PRT) and Sultanpur (SUL) isolates showing LC50of 5128.61 and 5623.41ppm, respectively. All the isolates were responsive to fipronil. Comparative detoxifying enzymes profiles revealed a significant correlation between the increased activity of esterase and deltamethrin resistance. The GST activity was 51.2% correlated with RR50of malathion while esterase activity was significantly correlated (68.9%) with RR50 of coumaphos. No correlation between the ivermectin resistance and enzyme activity was established. Multiple sequence analysis of S4-5 linker region of the sodium channel gene of all the isolates revealed a point mutation at 190th position (C190A) which is associated with deltamethrin resistance. The possible tick management strategies in this part of the country are discussed.

Cypermethrin and ivermectin resistance in field populations of Rhipicephalus sanguineus sensu lato (Latrielle, 1806) collected from dogs in south India.

The abuse of acaricides for control of Rhipicephalus sanguineus sensu lato ticks led to a strong selection pressure for acaricide resistance. Data on acaricide resistance in R. sanguineus s.l. populations from India is meager though veterinarians frequently report treatment failures. The present study was aimed to characterize the level of resistance in R. sanguineus s.l. against most commonly used drugs, cypermethrin and ivermectin in Andhra Pradesh, south India. Fourteen adult female tick populations were collected from naturally infested dogs at veterinary clinics, residence and stray dog in nine state municipal corporations/municipalities. Information on the history of dog treatment with acaricides was obtained by interviewing dog owners. The larval packet test (LPT) and larval immersion test (LIT) were used on the larvae of ticks to test for resistance to cypermethrin and ivermectin, respectively. Mortality data of each tick population was analyzed by probit analysis. Corresponding to the most susceptible population, thirteen (92.6%) and six (42.9%) tick populations were regarded as resistant to cypermethrin and ivermectin, respectively. The phenotypic level of cypermethrin (resistance ratios at LC50% varied from 1.55 to 13.29) and ivermectin (resistance ratios at LC50% ranged from 1.16 to 4.79) resistance varied distinctly between the populations. Additionally, all the populations were tested using PCR to demonstrate the frequency of the point mutation in sodium channel gene that corresponds with resistance of R. sanguineus s.l. to cypermethrin. A nucleotide substitution (T2134C) on domain III segment VI of the sodium channel gene was noticed in phenotypically resistant tick populations on DNA sequencing. Ivermectin resistance in the brown dog ticks is reported for the first time from India.

Characterization of deltamethrin, cypermethrin, coumaphos and ivermectin resistance in populations of Rhipicephalus microplus in India and efficacy of an antitick natural formulation prepared from Ageratum conyzoides

Rhipicephalus microplus is posing a serious threat to productive animal husbandry. Excessive use of synthetic chemicals in tick management has led to the development of resistant tick populations. Characterization of resistance to deltamethrin, cypermethrin, coumaphos and ivermectin in ticks is necessary to develop a suitable and sustainable control strategy. Based on adult immersion test and larval packet test, the resistance ratios (RR50) for adults and larvae of R. microplus populations from two Indian states ranged from 3.8 to 19.4 and 1.35–25.0 against deltamethrin, 0.061–26.3 and 0.22–19.2 against cypermethrin, and 0.2–9.5 and 0.01–3.1 against coumaphos, respectively, were recorded. Moreover, the RR50 for adults ranged from 0.212 to 3.87 against ivermectin. The RR50 for different acaricides was significantly (p<0.01) correlated with esterases, Glutathione S-transferase and monooxygenase activity. A point mutation at the 190th position of the domain II S4–5 linker region of the sodium channel gene in synthetic pyrethroids (SP) resistant populations was also detected. An antitick natural formulation prepared from the plant Azeratum conyzoides and containing two major compounds, Precocene-I (7‑methoxy-2, 2-dimethyl 2H-chromene) and Precocene II (6, 7-dimethoxy-2, 2-dimethyl- 3-chromene), was developed and tested against the resistant ticks. The LC50 values of the natural formulation against the resistant populations were in the range of 4.31–5.33% irrespective of their RR50 values. Multi-acaricide resistant populations of R. microplus are established in India and the A. conyzoides based natural formulation can be used for its management.

Chemical composition of essential oils from Thymus mongolicus, Cinnamomum verum, and Origanum vulgare and their acaricidal effects on Haemaphysalis longicornis (Acari: Ixodidae)

Chemical acaricides are mainly used in traditional tick control, which leads to the emergence of tick resistance and concurrently results in environmental pollution. In the present study, the chemical constituents of essential oils (EOs) from Thymus mongolicus, Cinnamomum verum, and Origanum vulgare was analyzed, and their potential application was evaluated to control the vector tick Haemaphysalis longicornis, which is widely distributed over vast areas of Eurasia, Australia, and New Zealand. Gas chromatography-mass spectrometry analysis revealed that the phenols thymol and carvacrol accounted for 34.66% and 75.72% of the EOs of T. mongolicus and O. vulgare, respectively, whereas trans-cinnamaldehyde (49.42%) was the main constituent of C. verum EO. Immersion tests showed that the EOs of C. verum and O. vulgare had significant acaricidal activity against larval H. longicornis, with the 50% lethal concentration (LC50) being 16.07 and 18.02 mg/mL, respectively, and the 95% lethal concentration (LC95) being 120.37 and 130.09 mg/mL, respectively. The EOs of O. vulgare and T. mongolicus showed significant acaricidal activity against unfed adult H. longicornis, with LC50 being 43.50 and 44.21 mg/mL, respectively, and LC95 being 113.66 and 137.99 mg/mL, respectively. The fumigant toxicity test showed significant acaricidal activity of the three EOs against both unfed and engorged nymphal and adult H. longicornis. Enzyme assays revealed that the EOs of both C. verum and O. vulgare significantly inhibited glutathione S-transferase activity (P < 0.05). In contrast, the activities of carboxylesterase and multifunction oxidases were significantly inhibited by EOs extracted from all three plants (P < 0.05). Taken together, these findings suggest that plant EOs may serve as an environment-friendly alternative for synthetic acaricides in future tick control.

Whole genome sequencing and bulked segregant analysis suggest a new mechanism of amitraz resistance in the citrus red mite, Panonychus citri (Acari: Tetranychidae).

Amitraz is a broad-spectrum insecticide/acaricide for the control of aphids, psyllids, ticks and mites. Current evidence suggests that ticks and phytophagous mites have developed strong resistance to amitraz. Previous studies have shown that multiple mechanisms are associated with amitraz resistance in ticks, but very few reports have involved Panonychus citri. We therefore used whole genome sequencing and bulked segregant analysis (BSA) to identify the mechanism underlying P. citri's resistance to amitraz. High-quality assembly of the whole P. citri genome was completed, resulting in a genome of approximately 83.97 Mb and a contig N50 of approximately 1.81 Mb. Gene structure predictions revealed 11 577 genes, of which 10940 genes were annotated. Trait-associated regions in the genome were mapped with bulked segregant analysis and 38 candidate SNPs were obtained, of which T752C had the strongest correlation with the resistant trait, located at the 5' untranslated region (UTR) of the β-2R adrenergic-like octopamine receptor gene. The mutation resulted in the formation of a short hairpin loop structure in mRNA and gene expression was down-regulated by more than 50% in the amitraz-resistant strain. Validation of the T752C mutation in field populations of P. citri found that the correlation between the resistance ratio and the base mutation was 94.40%. Our results suggest that this 5' UTR mutation of the β-2R octopamine receptor gene, confers amitraz resistance in P. citri. This discovery provides a new explanation for the mechanism of pest resistance: base mutations in the 5' untranslated region of target gene may regulate the susceptibility of pests to pesticides.

Rearing of Hyalomma marginatum (Acarina: Ixodidae) under laboratory conditions in Morocco

Hyalomma marginatum Koch is one of the main tick vectors of human and animal tick-borne diseases. The objective of this study was to establish standard procedures for rearing H. marginatum under laboratory conditions. Such laboratory tick populations are required to study acaricide resistance of Hyalomma ticks. In our rearing program, larvae and nymphs were fed on New Zealand white rabbits, whereas adults were fed on sheep. Non-parasitic stages were held at 18 and 28 °C to study the effect of temperature on development and survival. In our experiments, H. marginatum ticks have maintained the characteristics of a two-host life cycle. The engorged larvae did not detach and moulted on the rabbit, after which the emerged nymphs continued to feed on the same animal. The life cycle duration of H. marginatum was influenced by temperature, with each non-parasitic stage—i.e., larva and nymph molting—developing faster at 28 than at 18 °C; preoviposition and oviposition periods were shorter at 28 than at 18 °C. At 18 °C, no eggs hatched. The whole cycle from the collection of an engorged field tick until the emergence of second-generation larvae took 189 days. One such tick on average results in 3500 eggs which over time, taking into account the losses at each developmental stage, develop into 1200 adult ticks. Rearing these ticks a second generation therefore could result in millions of larval ticks.

Resistance to Ticks and the Path to Anti-Tick and Transmission Blocking Vaccines.

The medical and veterinary public health importance of ticks and tick-borne pathogens is increasing due to the expansion of the geographic ranges of both ticks and pathogens, increasing tick populations, growing incidence of tick-borne diseases, emerging tick transmitted pathogens, and continued challenges of achieving effective and sustained tick control. The past decades show an increasing interest in the immune-mediated control of tick infestations and pathogen transmission through the use of vaccines. Bovine tick resistance induced by repeated infestations was reported over a century ago. This review addresses the phenomena and immunological underpinning of resistance to tick infestation by livestock and laboratory animals; the scope of tick countermeasures to host immune defenses; and the impact of genomics, functional genomics, and proteomics on dissecting complex tick–host–pathogen interactions. From early studies utilizing tick tissue extracts to salivary gland derived molecules and components of physiologically important pathways in tick gut and other tissues, an increased understanding of these relationships, over time, impacted the evolution of anti-tick vaccine antigen selection. Novel antigens continue to emerge, including increased interest in the tick microbiome. Anti-tick and transmission blocking vaccines targeting pathogen reservoirs have the potential to disrupt enzootic cycles and reduce human, companion, domestic animal, and wildlife exposure to infected ticks.

Potential causes of Acaricide Resistance in Rhipicephalus and Amblyomma Ticks (Acari: Ixodidae) in Namwala District, Zambia

Acaricide resistance in ticks poses a great threat to livestock production in many parts of the world where ticks are a problem. The objectives of this study were to screen for acaricide resistance in Rhipicephalus and Amblyomma ticks using phenotypic and molecular assays, and to assess current tick control practices used by cattle farmers in the traditional sector of Namwala District. The larval packet test was used to screen for acaricide resistance in ticks covering concentrations up to twice the discriminatory dose for amitraz, diazinon and cypermethrin. Genetic mutations associated with resistance to amitraz (A22C-T8P and T65C-L22S), and organophosphates/ pyrethroids (G1120A) were screened using polymerase chain reaction and sequencing. Information on tick control practices at the household level was collected using a semi-structured questionnaire. Intermediate resistance (21-50%) to amitraz and cypermethrin was detected in both Rhipicephalus and Amblyomma ticks, with both tick genera showing susceptibility to diazinon (&lt;10%). None of the ticks in this study had the reported acaricide resistance-conferring molecular markers that were screened for. The findings suggest that the resistance detected in the studied tick population may be due to other mechanisms yet to be identified. Tick control practices observed amongst the farmers, such as incorrect use of acaricide concentrations and rotations, could be fuelling the development of acaricide resistance. Considering that acaricide treatment is the mainstay of tick control in the country, it is thus critical to comprehensively unravel the factors contributing to treatment failure as this would allow for the application of appropriate remedial actions for effective tick control in Zambia.

Multiple Country and Breed Genomic Prediction of Tick Resistance in Beef Cattle.

Ticks cause substantial production losses for beef and dairy cattle. Cattle resistance to ticks is one of the most important factors affecting tick control, but largely neglected due to the challenge of phenotyping. In this study, we evaluate the pooling of tick resistance phenotyped reference populations from multi-country beef cattle breeds to assess the possibility of improving host resistance through multi-trait genomic selection. Data consisted of tick counts or scores assessing the number of female ticks at least 4.5 mm length and derived from seven populations, with breed, country, number of records and genotyped/phenotyped animals being respectively: Angus (AN), Brazil, 2,263, 921/1,156, Hereford (HH), Brazil, 6,615, 1,910/2,802, Brangus (BN), Brazil, 2,441, 851/851, Braford (BO), Brazil, 9,523, 3,062/4,095, Tropical Composite (TC), Australia, 229, 229/229, Brahman (BR), Australia, 675, 675/675, and Nguni (NG), South Africa, 490, 490/490. All populations were genotyped using medium density Illumina SNP BeadChips and imputed to a common high-density panel of 332,468 markers. The mean linkage disequilibrium (LD) between adjacent SNPs varied from 0.24 to 0.37 across populations and so was sufficient to allow genomic breeding values (GEBV) prediction. Correlations of LD phase between breeds were higher between composites and their founder breeds (0.81 to 0.95) and lower between NG and the other breeds (0.27 and 0.35). There was wide range of estimated heritability (0.05 and 0.42) and genetic correlation (-0.01 and 0.87) for tick resistance across the studied populations, with the largest genetic correlation observed between BN and BO. Predictive ability was improved under the old-young validation for three of the seven populations using a multi-trait approach compared to a single trait within-population prediction, while whole and partial data GEBV correlations increased in all cases, with relative improvements ranging from 3% for BO to 64% for TC. Moreover, the multi-trait analysis was useful to correct typical over-dispersion of the GEBV. Results from this study indicate that a joint genomic evaluation of AN, HH, BN, BO and BR can be readily implemented to improve tick resistance of these populations using selection on GEBV. For NG and TC additional phenotyping will be required to obtain accurate GEBV.

Tick treatment practices in the field: Access to, knowledge about, and on-farm use of acaricides in Laikipia, Kenya

The prevention of tick-borne diseases is a major challenge for livestock production globally. Tick control strategies include the use of acaricides, but the prescribed strategies do not achieve the desired results in several countries, including Kenya. To better understand how tick treatment practices, contribute to reported tick treatment failures, we assessed livestock owners’ acaricide procurement, level of knowledge about acaricides and tick resistance, and how they apply acaricides. We also assessed the quality of the commonly available acaricides. We focused on three livestock systems in Laikipia County, Kenya: two private ranches; one community ranch whose members communally graze their cattle and acquire and apply acaricides; and individual livestock owners in two pastoral communities who individually graze their cattle and acquire and apply acaricides. Through interviews and focus group discussions we assessed; access to acaricides, livestock owners’ knowledge, and acaricide use practices; interview data were triangulated with participant observations (n = 107). We analysed nine commonly used acaricides to determine the active ingredient concentration and we determined the concentration of active ingredients in acaricide dilutions collected on farms. All livestock owners had access to and used chemical acaricides for tick control, predominantly amitraz-based. Private ranchers bought one amitraz-based acaricide in bulk directly from the manufacturer, while all other livestock owners bought from agrovet shops. The livestock owners acquired knowledge about acaricides from their own experiences and through experience-based recommendations from peers, but not from the technical information provided by the manufacturers and agrovet shops. All pastoral livestock frequently changed acaricide brand and active ingredient class. A large majority of pastoralists (86%) mixed acaricide brands within and across active ingredient classes; a smaller majority (56%) mixed acaricides with crop pesticides and insecticides. Our lab tests confirmed the content description on the labels bought from agrovet shops. However, on-farm acaricide dilutions from all three livestock systems deviated from the level recommended for effective treatment. If too diluted, the acaricide does not kill ticks, promoting resistance development. If too concentrated, this increases environmental contamination and raises public health concerns. Livestock owners lack a technical understanding of the functioning of acaricides, compromising their use and effectiveness. The widely adopted mixing of acaricides with insecticides and pesticides raises serious health concerns.

Molecular survey of pyrethroid and fipronil resistance in isolates of Rhipicephalus microplus in the north of Uruguay

The resistance of Rhipicephalus microplus to acaricides is a serious control problem, so its early diagnosis by a molecular technique is important. This study aims to develop a multiplex allele–specific polymerase chain reaction (PCR) for single-nucleotide polymorphisms (SNPs) in the para-sodium channel gene and in the GABA-Cl gene, associated with pyrethroids (cypermethrin and flumethrin) and fipronil resistance, respectively. We used 22 tick field isolates from farms with tick control problems (sampling convenience). These farms are located in departments of northern Uruguay. Three mutations in the sodium channel gene (Domain II S4–5: C190A and G215T; domain III S6: T2134A) and one in the GABA-Cl gene (A286S/L: CG856CC/TG) were studied. Mutations G215T and T213A were not detected. In all field isolates, the resistant allele (R) for C190A mutation (knockdown resistance, kdr) was detected, mainly in heterozygous individuals (SR) (11.1% to 86.7%). The highest incidence of the kdr mutant allele occurred in the Tacuarembó tick field isolates, where on 7 out of 10 farms >30% of individuals were SR and on one farm > 30% of individuals were RR. The next highest was Artigas (half of farms had>30% SR individuals and a quarter had >30% RR individuals). The resistance to dieldrin locus (rdl) mutation (CG856CC/TG) was absent in five field isolates. The highest incidenceof the mutant allele was observed in ticks from farms in Rivera (all farms had SR in >30% of individuals and two farms had RR in >12.5 and >16.7% of individuals) followed by farms in Tacuarembó (3 of 10 farms had >30% SR and 2 with >30% RR). Less than half of the farms had rdl in homozygous individuals. No significant association was observed between phenotypic bioassays and the rdl resistance allele. Several field isolates were phenotypically susceptible to the presence of the rdl allele. Several causes are possible (bioassay sensitivity, discriminating concentration). Individuals with simultaneous kdr and rdl mutations were present in 17 field isolates, and their frequency varied between 0.06% and 60%. Genotypic analysis shows that tick resistance to both acaricides, especially pyrethroids, is a serious problem. It is important to monitor the resistance using molecular techniques to plan efficient control measures. This is the first report describing kdr and rdl detection in R. microplus in Uruguay.

Tick–human interactions: from allergic klendusity to the α-Gal syndrome

Ticks and the pathogens they transmit, including bacteria, viruses, protozoa, and helminths, constitute a growing burden for human and animal health worldwide. The ability of some animal species to acquire resistance to blood-feeding by ticks after a single or repeated infestation is known as acquired tick resistance (ATR). This resistance has been associated to tick-specific IgE response, the generation of skin-resident memory CD4+ T cells, basophil recruitment, histamine release, and epidermal hyperplasia. ATR has also been associated with protection to tick-borne tularemia through allergic klendusity, a disease-escaping ability produced by the development of hypersensitivity to an allergen. In addition to pathogen transmission, tick infestation in humans is associated with the α-Gal syndrome (AGS), a type of allergy characterized by an IgE response against the carbohydrate Galα1-3Gal (α-Gal). This glycan is present in tick salivary proteins and on the surface of tick-borne pathogens such as Borrelia burgdorferi and Anaplasma phagocytophilum, the causative agents of Lyme disease and granulocytic anaplasmosis. Most α-Gal-sensitized individuals develop IgE specific against this glycan, but only a small fraction develop the AGS. This review summarizes our current understanding of ATR and its impact on the continuum α-Gal sensitization, allergy, and the AGS. We propose that the α-Gal-specific IgE response in humans is an evolutionary adaptation associated with ATR and allergic klendusity with the trade-off of developing AGS.

Government Assistance To Farmers Against Tick-Borne Diseases During The COVID-19 lockdown

Ticks are responsible for transmitting viral, bacterial, and protozoal diseases to humans and animals and also cause significant economic damage to the livestock industry. The owner of the farmhouse prefers to use acaricides, a key component of tick control strategies. However, the indiscriminate and irresponsible use of acaricides has a detrimental effect on the increase in the contamination of the environment, acaricide resistance in ticks, and its residues in milk and meat of the animal. There is now ample evidence that vaccination can provide significant immunity to tick and tick-borne diseases [1]. The COVID-19 virus, like its predecessor, the SARS virus (and other emerging diseases), is thought to have spread to humans through animal markets of Wuhan a central city in China [2]. Fortunately, the ticks do not spread this virus, but the COVID-19 virus is responsible for all those factors that can cause it to spread rapidly to animals.

Innovative granular formulation of Metarhizium robertsii microsclerotia and blastospores for cattle tick control

The tick Rhipicephalus microplus poses a serious threat to the cattle industry, resulting in economic losses aggravated by tick resistance to chemical acaricides. Strains of Metarhizium spp., a well-known group of entomopathogenic fungi, can contribute to managing this ectoparasite. We explored two novel granular, microsclerotia- or blastospores-based formulations of Metarhizium robertsii for R. microplus control under semi-field conditions. Fungal persistence in soil was also observed for 336 days. The experiment used pots of Urochloa decumbens cv. Basilisk grass, treated with 0.25 or 0.5 mg of granular formulation/cm2 (25 or 50 kg/ha) applied to the soil surface prior to transferring engorged tick females onto the treated soil. The fungal granules yielded more conidia with subsequent sporulation under controlled indoor conditions than in the outdoor environment, where the levels of fungus rapidly declined over time. Metarhizium-root colonization ranged from 25 to 66.7% depending on the propagule and rate. Fungal formulations significantly reduced the number of tick larvae during the humid season, reaching at least 64.8% relative efficacy. Microsclerotia or blastospores-granular formulations of M. robertsii can reduce the impact of R. microplus, and thus prove to be a promising tool in the control of ticks.

Efficacy of commercially available chemical compound used against management of tick infestation in Mhow, Madhya Pradesh

The study was conducted to determine the efficacy of commercially available chemical compound used in management of tick infestation in this area where the Rhipicephalus microplus is the most prevalent species of ticks. The most important chemical compound used for controlling ticks in this area is cypermethrin, deltamethrin and amitraz. This is happen because cheap and easy availability of these compound. The engorged female R. microplus tick sample was collected from unorganised dairy farm of Mhow districts in Madhya Pradesh. The Adult Immersion Test (AIT) and larval packet test (LPT) was performed for the characterization of resistance in field tick population. The slope of mortality, lethal concentration for 50 % (LC50), and resistance ratios (RR) were determined from the regression graphs of probit mortality of ticks plotted against log concentrations of chemical compound used in study. The resistant ration (RR) of cypermethrin was in the range of 0.76 to 1.45. Most of the population were found susceptibly in LPT and AIT and the slope value was recorded lower than the susceptible reference strain. In case of deltamethrin, the resistance ratio (RR) was in the range of 22.35 to 34.64 at level II and III and the slop value of field population was found comparatively low than susceptible reference strain. In amitraz, the resistance ratio (RR) was obtained as 2.23.On the basis of RR the tested tick showed resistance in adult stage at level I. The AIT bioassay was used for the characterization of resistance in field tick population. Efficacy of chemical compound was recorded on basis of resistance ratio and level of resistance was assessed. The data on field status of acaricide resistance in Mhow block of Madhya Pradesh state will be helpful to adopt suitable strategy to overcome the process of development of resistance in ticks.