Resistance to natural tick infestation varies with age and coat and hair traits in a tropically adapted beef cattle breed

Rhipicephalus (Boophilus) microplus causes considerable livestock production losses. Knowledge of the traits that influence tick resistance contributes to the development of breeding strategies designed to improve herd productivity. Within this context, this study evaluated the resistance of Caracu, a tropically adapted cattle breed, to R. microplus. Tick count, hair length, coat thickness, and coat color were evaluated in 202 naturally tick-infested females (cows and heifers) over a period of 18 months. Blood samples were collected from all animals during the winter season for hematological analysis. Data were analyzed using Pearson correlations, generalized linear models, and principal component analysis. Correlation coefficients of tick count with coat color, coat thickness, and hair length were estimated within each season. Hematological parameters were only included in the winter season analysis and were analyzed by the restricted maximum likelihood method using log-transformed data. No differences in blood parameters were observed between animals with and without ticks. However, tick count was negatively correlated with erythrocytes (-0.29) and hematocrit (-0.24) and positively correlated with mean corpuscular hemoglobin (0.21) and mean corpuscular hemoglobin concentration (0.25). These findings suggest that higher tick counts lead to a decrease in erythrocytes but also to an increase in the amount of hemoglobin per erythrocyte, which could reduce the damage caused by low erythrocyte levels due to tick hematophagy, delaying or preventing anemia. Although tick infestation on pasture was demonstrated by the infestation of all staff members during herd management, none of the animals exhibited high tick counts, providing evidence of resistance of Caracu animals to R. microplus. Tick infestation was influenced by age class (cows > heifers), season (spring and summer > fall and winter), coat thickness (>1.5 mm > <1.5 mm), and hair length (>6 mm > <6 mm). Three components were extracted by principal component analysis, which accounted for 69.46% of data variance. The findings of this study will contribute to the development of efficient strategies aimed at reducing economic losses due to tick infestation and could be applied in animal breeding to select for tick resistance traits, reducing chemical control strategies and consequently improving sustainable livestock production.

High-resolution prediction models for Rhipicephalus microplus and Amblyomma cajennense s.l. ticks affecting cattle and their spatial distribution in continental Ecuador using bioclimatic factors

In Ecuador, the main tick species affecting cattle are Rhipicephalus microplus and Amblyomma cajennense sensu lato. Understanding their spatial distribution is crucial. To assess their distribution, data from 2895 farms visited between 2012 and 2017 were utilized. Ticks were collected during animal inspections, with each farm's location georeferenced. Bioclimatic variables and vapor pressure deficit data were obtained from Climatologies at High resolution for the Earth´s Land Surface Areas (CHELSA) dataset. They were overlaid to develop predictive maps for each species using Random Forest (RF) models. The cross-validation results for RF prediction models showed high accuracy for both R. microplus and A. cajennense s.l. presence with values of accuracy = 0.97 and 0.98, sensitivity = 0.96 and 0.99, and specificity = 0.96 and 0.93, respectively. A carefully selected subset of bioclimatic variables was used to describe the presence of each tick species. Higher levels of precipitation had positive effect on the presence of R. microplus but a negative effect on A. cajennense s.l. In contrast, isothermality (BIO3) was more important for the presence of A. cajennense s.l. compared to R. microplus. As a result, R. microplus had a broader distribution across the country, while A. cajennense s.l. was mainly found in coastal areas with evident seasonality. The coexistence of both species in some regions could be attributed to transitional zones, whereas high altitudes limited tick presence. This information can aid in developing appropriate tick management plans, particularly considering A. cajennense s.l.'s broad host range species and R. microplus's specificity for cattle. Moreover, the predictive models can identify areas at risk of associated challenging hemoparasite, requiring special attention and mitigation measures.

Daylight photodynamic inactivation of cattle tick Rhipicephalus microplus by porphyrins: An alternative for the ectoparasite control

The bovine tick Rhipicephalus microplus, a primary ectoparasite of veterinary concern, contributes significantly to disease transmission and reduced cattle productivity, resulting in substantial economic losses. The overuse of chemical acaricides has led to the emergence of resistant strains, posing a considerable challenge to veterinary medicine. Consequently, the development of alternative parasite control methods is essential to ensure livestock quality and enhance food safety worldwide. Our study introduces an innovative approach to photodynamic inactivation (PDI) of the bovine tick, harnessing natural daylight for a potential field application. Reproductive parameters (female and egg mass, egg production index, and larval hatch) were evaluated in engorged female ticks under photodynamic action using the hematoporphyrin (HP) and tetra-cationic porphyrins free-base meso-tetra-ruthenated (4-pyridyl) (RuTPyP) and its zinc(II) complex (ZnRuTPyP) as photosensitizers (PS). The results showed that there was no significant difference between the groups treated with tetra‑ruthenium porphyrins and the control group. However, HP exhibits a control percentage of 97.9% at a concentration of 2.5 μmol.L-1, aligning with the expected control rates achieved by conventional chemical acaricides. Photophysical and physicochemical parameters such as the number of singlet oxygen produced and lipophilicity were discussed for each PS and related to tick control percentages. Furthermore, the interaction between HP and chitin, an important macromolecule presents in the tick's cuticle, considered as the primary target tick structure during PDI was observed by the absorption and fluorescence emission spectroscopic techniques. Therefore, the results presented here extend the potential for controlling R. microplus through photodynamic inactivation while utilizing sunlight as a source of natural irradiation.

Changes in saliva protein profile throughout Rhipicephalus microplus blood feeding

BACKGROUND

When feeding on a vertebrate host, ticks secrete saliva, which is a complex mixture of proteins, lipids, and other molecules. Tick saliva assists the vector in modulating host hemostasis, immunity, and tissue repair mechanisms. While helping the vector to feed, its saliva modifies the site where pathogens are inoculated and often facilitates the infection process. The objective of this study is to uncover the variation in protein composition of Rhipicephalus microplus saliva during blood feeding.

METHODS

Ticks were fed on calves, and adult females were collected, weighed, and divided in nine weight groups, representing the slow and rapid feeding phases of blood feeding. Tick saliva was collected, and mass spectrometry analyses were used to identify differentially secreted proteins. Bioinformatic tools were employed to predict the structural and functional features of the salivary proteins. Reciprocal best hit analyses were used to identify conserved families of salivary proteins secreted by other tick species.

RESULTS

Changes in the protein secretion profiles of R. microplus adult female saliva during the blood feeding were observed, characterizing the phenomenon known as "sialome switching." This observation validates the idea that the switch in protein expression may serve as a mechanism for evading host responses against tick feeding. Cattle tick saliva is predominantly rich in heme-binding proteins, secreted conserved proteins, lipocalins, and protease inhibitors, many of which are conserved and present in the saliva of other tick species. Additionally, another remarkable observation was the identification of host-derived proteins as a component of tick saliva.

CONCLUSIONS

Overall, this study brings new insights to understanding the dynamics of the proteomic profile of tick saliva, which is an important component of tick feeding biology. The results presented here, along with the disclosed sequences, contribute to our understanding of tick feeding biology and might aid in the identification of new targets for the development of novel anti-tick methods.

First record of Rhipicephalus (Boophilus) microplus in Ghana, a potential risk to livestock production

Ticks are a public health threat due to their tendency to spread pathogens that affect humans and animals. With reports of Rhipicephalus (Boophilus) microplus invasion in neighbouring countries, there is the risk of this species invading Ghana through livestock trade. Previous identification of tick species in Ghana has been based on morphological identification, which can be ineffective, especially with damaged tick specimens or engorged nymphs. This study focused on the Kassena-Nankana District, which serves as a trade route for cattle into Ghana, to determine the presence of R. microplus. Three genera of ticks were identified as Amblyomma (70.9%), Hyalomma (21.3%) and Rhipicephalus (7.8%). The engorged nymphs that could not be identified morphologically were analyzed using primers that target the mitochondrial 16S rRNA gene. This study reports the first record of R. (B.) microplus in Ghana. Furthermore, R. microplus constituted 54.8% of the Boophilus species collected in this study. This finding is an addition to the diverse tick species previously collected in Ghana, most of which are of veterinary and public health importance. With reports of acaricide resistance in R. microplus and its role in spreading infectious pathogens, the detection of this species in Ghana cannot be overlooked. Nationwide surveillance will be essential to ascertain its distribution, its effects on cattle production, and the control measures adopted.

Periviscerokinin (Cap2b; CAPA) receptor silencing in females of Rhipicephalus microplus reduces survival, weight and reproductive output

BACKGROUND

The cattle fever tick, Rhipicephalus (Boophilus) microplus, is a vector of pathogens causative of babesiosis and anaplasmosis, both highly lethal bovine diseases that affect cattle worldwide. In Ecdysozoa, neuropeptides and their G-protein-coupled receptors play a critical integrative role in the regulation of all physiological processes. However, the physiological activity of many neuropeptides is still unknown in ticks. Periviscerokinins (CAP2b/PVKs) are neuropeptides associated with myotropic and diuretic activities in insects. These peptides have been identified only in a few tick species, such as Ixodes ricinus, Ixodes scapularis and R. microplus, and their cognate receptor only characterized for the last two.

METHODS

Expression of the periviscerokinin receptor (Rhimi-CAP2bR) was investigated throughout the developmental stages of R. microplus and silenced by RNA interference (RNAi) in the females. In a first experiment, three double-stranded (ds) RNAs, named ds680-805, ds956-1109 and ds1102-1200, respectively, were tested in vivo. All three caused phenotypic effects, but only the last one was chosen for subsequent experiments. Resulting RNAi phenotypic variables were compared to those of negative controls, both non-injected and dsRNA beta-lactamase-injected ticks, and to positive controls injected with beta-actin dsRNA. Rhimi-CAP2bR silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues.

RESULTS

Rhimi-CAP2bR transcript expression was detected throughout all developmental stages. Rhimi-CAP2bR silencing was associated with increased female mortality, decreased weight of surviving females and of egg masses, a delayed egg incubation period and decreased egg hatching (P < 0.05).

CONCLUSIONS

CAP2b/PVKs appear to be associated with the regulation of female feeding, reproduction and survival. Since the Rhimi-CAP2bR loss of function was detrimental to females, the discovery of antagonistic molecules of the CAP2b/PVK signaling system should cause similar effects. Our results point to this signaling system as a promising target for tick control.

Tick CAPA propeptide cDNAs and receptor activity of endogenous tick pyrokinins and analogs: Towards discovering pyrokinin function in ticks

Pyrokinins (PKs) are pleiotropic neuropeptides with significant roles in invertebrate physiology. Although functions of PKs are known in insects, there is a lack of knowledge of PK-encoding genes and PKs functions in ticks. Herein the first tick cDNAs of the capability (capa) gene were cloned from the southern cattle tick, Rhipicephalus microplus (Acari: Ixodidae), and the blacklegged tick, Ixodes scapularis. Each cDNA encoded one periviscerokinin and five different pyrokinins. Two PKs were identical in sequence in the two species. The three PKs unique to R. microplus (Rhimi-CAPA-PK1, -PK2, and -PK5) were tested on the recombinant R. microplus pyrokinin receptor using a calcium bioluminescence assay. The Rhimi-CAPA-PKs acted as agonists with EC_50s ranging from 101-188 nM. Twenty PK analogs designed for enhanced bioavailability and biostability were tested on the receptor. Five of these were designed based on the sequences of the three unique Rhimi-CAPA-PKs. Eight PK analogs were also agonists; four of them were full agonists that exhibited comparable efficacy to the native Rhimi-CAPA-PKs, with EC₅₀ ranging from 401 nM-1.9 μM. The structure-activity relationships (SAR) of all analogs were analyzed. Our results suggested that a positively charged, basic lysine at the variable position X of the PK active core (FXPRLamide) conferred enhanced affinity to the analogs in their interaction with the tick receptor. These analogs are promising tools to elucidate the pyrokinin function in ticks in vivo as these analogs are expected to have prolonged hemolymph residence time in comparison to the native peptides.

Molecular detection of dugbe orthonairovirus in cattle and their infesting ticks (Amblyomma and Rhipicephalus (Boophilus)) in Nigeria

Dugbe orthonairovirus (DUGV), a tick-borne zoonotic arbovirus, was first isolated in 1964 in Nigeria. For over four decades, no active surveillance was conducted to monitor the spread and genetic variation of DUGV. This study detected and genetically characterized DUGV circulating in cattle and their infesting ticks (Amblyomma and Rhipicephalus (Boophilus)) in Kwara State, North-Central Nigeria. Blood and or ticks were collected from 1051 cattle at 31 sampling sites (abattoirs and farms) across 10 local government areas of the State. DUGV detection was carried out by RT-qPCR, and positive samples sequenced and phylogenetically analysed. A total of 11824 ticks, mostly A. variegatum (36.0%) and R. (B.) microplus (63.9%), were obtained with mean tick burden of 12 ticks/cattle. Thirty-four (32 A. variegatum and two R. (B.) microplus) of 4644 examined ticks were DUGV-positive, whereas all of the cattle sera tested negative for DUGV genome. Whole genome sequence (S, M and L segments) and phylogenetic analyses indicate that the positive samples shared up to 99.88% nucleotide identity with and clustered around the Nigerian DUGV prototype strain IbAr 1792. Hence, DUGV with high similarity to the previously characterised strain has been detected in Nigeria. To our knowledge, this is the first report of DUGV in North-Central Nigeria and the most recent information after its last surveillance in 1974.

Rhipicephalus (Boophilus) microplus (Ixodida: Ixodidae) Larvae Collected From Vegetation in the Coastal Wildlife Corridor of Southern Texas and Research Solutions for Integrated Eradication

The potential for reinvasion of the United States by cattle fever ticks, Rhipicephalus (Boophilus) annulatus and Rhipicephalus microplus (Canestrini), which remain established in Mexico, threatens the viability of the domestic livestock industry because these ticks vector the causal agents (Babesia bovis and Babesia bigemina) of bovine babesiosis. The Cattle Fever Tick Eradication Program safeguards the health of the national cattle herd preventing the reemergence of bovine babesiosis by keeping the United States free of cattle fever ticks. Here, the collection of free-living southern cattle tick, R. microplus, larvae by sweeping flannel flags over vegetation in the wildlife corridor of Cameron and Willacy Counties, TX, is reported. Finding R. microplus larvae on vegetation complements reports of infestations in wildlife hosts inhabiting the southern Texas coastal plains. Land uses and environmental conditions have changed since cattle fever ticks were eradicated from the United States by 1943. These changes complicate efforts by the Cattle Fever Tick Eradication Program to keep cattle in the United States free of the cattle fever tick disease vectors. Current scientific research on technologies that could be used for area-wide management of fever tick larvae in south Texas and how this could be applied to integrated eradication efforts are discussed.

Rhipicephalus microplus serpins interfere with host immune responses by specifically modulating mast cells and lymphocytes

Rhipicephalus microplus ticks feed on a bovine host for three weeks. At the attachment site, inflammatory and immune responses are triggered resulting in the recruitment of cells and production of a set of immunological mediators. To oppose the host's immune responses, ticks inoculate bioactive salivary molecules capable of interfering with these defense mechanisms. Serpins are among the most frequent molecules present in tick saliva and have been shown to negatively affect the host's anti-tick immunity. R. microplus has at least eighteen full-length serpins (RmS) and eleven are transcribed during blood feeding. Among them, RmS-3, RmS-6, and RmS-17 are present in the saliva of engorged females. Here, the effect of these serpins on the immune responses was evaluated in cells involved in innate/inflammatory (mast cells and macrophages) and adaptive (T cells) immunity. RmS-3 modulated mast cells due to its inhibitory activity on peritoneal rat chymase and on vascular permeability in acute inflammation. In addition, both RmS-6 and RmS-17 inhibited vascular permeability. Of the three serpins studied, neither affected activation nor inflammatory cytokine production by murine macrophages. On the other hand, RmS-3 and RmS-17 presented an inhibitory effect on the metabolic activity of lymphocytes, with the latter being the most potent, while RmS-6 had no effect on it. This activity was associated with a decrease in lymphocyte proliferation, but not with induction of cell death. The present study highlights the powerful modulatory role of tick salivary serpins in the host's immune system and inspire the discovery of targets for the treatment of inflammatory/immune disorders.

Climate change implications for the distribution of the babesiosis and anaplasmosis tick vector, Rhipicephalus (Boophilus) microplus

Climate change ranks among the most important issues globally, affecting geographic distributions of vectors and pathogens, and inducing losses in livestock production among many other damaging effects. We characterized the potential geographic distribution of the ticks Rhipicephalus (Boophilus) microplus, an important vector of babesiosis and anaplasmosis globally. We evaluated potential geographic shifts in suitability patterns for this species in two periods (2050 and 2070) and under two emissions scenarios (RCPs 4.5 and 8.5). Our results anticipate increases in suitability worldwide, particularly in the highest production areas for cattle. The Indo-Malayan region resulted in the highest cattle exposure under both climate change projections (2050), with increases in suitability of > 30%. This study illustrates how ecological niche modeling can be used to explore probable effects of climate change on disease vectors, and the possible consequences on economic dimensions.

Biological parameters for Rhipicephalus microplus in the field and laboratory and estimation of its annual number of generations in a tropical region

The present study aimed to evaluate biological parameters of Rhipicephalus microplus in the non-parasitic phase in both field and laboratory conditions. It also aimed to assess correlations between duration (in days) of these parameters and climatic variables (humidity, rainfall, and soil temperature) and to estimate the annual number of generations of R. microplus in a tropical region. The non-parasitic phase of R. microplus in field and laboratory conditions was evaluated throughout the course of two years. A pasture was infested with engorged female of R. microplus, and biological parameters, including female pre-oviposition, female oviposition, egg mass incubation, larval pre-hatching phase, larval maturation, and larval longevity, were evaluated concomitantly with the collection of data on climatic conditions. The same parameters were also evaluated in a climatized chamber in the laboratory. The total duration of the non-parasitic phase in the field was longer in the dry season (1st and 4th life-cycle repetitions) than in the rainy season (2nd, 3rd, and 5th repetitions). Tick biological parameters for the non-parasitic phase in the laboratory were similar to those obtained in the field during the rainy season. The evaluated biological parameters were influenced mainly by environmental and ground-level temperatures, which modified egg mass incubation, larval pre-hatching, and larval longevity periods and, consequently, the total duration of the non-parasitic phase of the tick. The annual number of generations for the tick was estimated at five per year, which is alarming because it represents an increase, and so new studies into strategic control are needed.

Activation of the ambusher tick Rhipicephalus microplus (Acari: Ixodidae) exposed to different stimuli

The present study aimed to evaluate the behaviour of larvae of Rhipicephalus microplus exposed to different stimuli. A Y-olfactometer was positioned vertically and R. microplus larvae were exposed to environmental air, CO₂ alone, N,N-diethyl-3-methylbenzamide (DEET) alone, and CO₂ combined with the repellents DEET and (E)-2-octenal. Tests were also conducted with the olfactometer positioned horizontally; in this case, however, only CO₂ was tested. In all tests conducted with the Y-olfactometer positioned vertically, CO₂ activated R. microplus larvae even in the presence of DEET and (E)-2-octenal, although activation was lower when these repellents were used. In the absence of CO₂ , larval behaviour against DEET was similar to that of the larvae in the control group. In the tests performed with the olfactometer positioned horizontally, the larvae had no significant response to the presence of CO₂ . The larvae were not attracted to or repelled by any compound tested in either the vertical or horizontal position of the olfactometer. The lack of horizontal displacement, attraction or repellence may have been a result of the ambush behaviour of this tick species. However, when larvae were exposed to stimuli and the olfactometer was positioned vertically, the interference of attractant and repellent stimuli in larval behaviour was assessed.

Tick and Host Derived Compounds Detected in the Cement Complex Substance

Ticks are obligate hematophagous arthropods and vectors of pathogens affecting human and animal health worldwide. Cement is a complex protein polymerization substance secreted by ticks with antimicrobial properties and a possible role in host attachment, sealing the feeding lesion, facilitating feeding and pathogen transmission, and protection from host immune and inflammatory responses. The biochemical properties of tick cement during feeding have not been fully characterized. In this study, we characterized the proteome of Rhipicephalus microplus salivary glands (sialome) and cement (cementome) together with their physicochemical properties at different adult female parasitic stages. The results showed the combination of tick and host derived proteins and other biomolecules such as α-Gal in cement composition, which varied during the feeding process. We propose that these compounds may synergize in cement formation, solidification and maintenance to facilitate attachment, feeding, interference with host immune response and detachment. These results advanced our knowledge of the complex tick cement composition and suggested that tick and host derived compounds modulate cement properties throughout tick feeding.

Partial characterization of the voltage-gated sodium channel gene and molecular detection of permethrin resistance in Rhipicephalus annulatus (Say, 1821)

The cattle tick, Rhipicephalus annulatus (Say) is a vector of bovine babesiosis and responsible for direct and indirect losses to cattle producing areas located in temperate and subtropical dry regions. Resistance against pyrethroids has been reported for this species in Asia and Africa, but never before in North America. An outbreak strain, Rio Lado, collected close to the border between Mexico and the United States, in Maverick County, Texas, showed low level of resistance to permethrin, a pyrethroid pesticide. We used genomic material from different strains of cattle ticks collected within the Permanent Quarantine Zone (Rio Lado, Vega and Klein Grass strains) to partially characterize the coding gene of the voltage-gated sodium channel (Na-channel), target-site of pyrethroid pesticides, and search for putative mutations associated with resistance using quantitative PCR high resolution melt (HRM) analysis. The two amplified fragments, corresponding to domains II and III of the Na-channel, were 100 % identical to its ortholog in Rhipicephalus microplus (Canestrini). No nucleotide polymorphisms in the Na-channel gene were observed in the pyrethroid-resistant Rio Lado strain, when compared to the susceptible strains Klein Grass and Vega. This study reports the first case of pyrethroid resistance in R. annulatus collected in the United States. Also, we provide new genomic data for this species of tick that allows for the development of a new method to screen for mutations associated with pyrethroid resistance.

Seasonal activity of ticks infesting domestic dogs in Bejaia province, Northern Algeria

This epidemiological study aimed to determine the species of tick infestation in dogs, their prevalence and dynamic in the Bejaia province, northeastern Algeria. A total of 631 dogs were examined from different localities of the Bejaia province between March 2016 and February 2017. Of the 631 examined dogs, 15% were infested with one or more tick species. A total of 339 adult ticks were collected and identified, including 199 male tick species and 140 female tick species. Our results revealed that most of these were Rhipicephalus species, with Rhipicephalus sanguineus (51.32%) being the most prevalent followed by Rhipicephalus bursa (35.1%) and Rhipicephalus turanicus (12.98%). Ixodes ricinus represented only 0.6% of all ticks collected. The highest infested seasons were spring (22.55%) and summer (22.54%) and the lowest infested seasons were autumn (8.62%) and winter ( 0.9%). There is no significant difference between the sex of the animal and the prevalence of infestation (p = 0.837). Also, the prevalence of infestation by ticks in young animals was higher than that in adult animals (p = 0.550). A significant difference between the prevalence of infestation and animal breed was observed (p = 0.042). This study is the first epidemiological investigation conducted on the prevalence of hard ticks infesting domestic dogs in Bejaia (northeastern Algeria) based on conventional methods. It is therefore necessary to implement an effective tick control strategy during infestation periods in order to prevent vector-borne diseases.

Multi-scale patterns of tick occupancy and abundance across an agricultural landscape in southern Africa

Land use influences the prevalence and distribution of ticks due to the intimate relationship of ticks with their environment. This relationship occurs because land use alters two essential tick requirements: vertebrate hosts for blood meals and a suitable microclimate when off-host. Given the risks to human and animal health associated with pathogens transmitted by ticks, there is an ongoing need to understand the impact of environmental drivers on tick distributions. Here, we assessed how landscape features, neighborhood effects, and edges influenced tick occupancy and abundance across an agricultural landscape in southern Africa. We found that Rhipicephalus appendiculatus and Rhipicephalus simus increased in abundance closer to protected savanna, while Haemaphysalis elliptica increased in abundance closer to human habitation. The composition of the landscape surrounding savanna patches also differentially influenced the occupancy of each tick species; H. elliptica was more likely to be found in savanna patches surrounded by subsistence agriculture while R. appendiculatus and R. simus were more likely to be found in savanna surrounded by sugarcane monocultures. At the local scale we found that R. appendiculatus and R. simus avoided savanna edges. The availability of hosts and variation in vegetation structure between commercial agriculture, subsistence agriculture, and savanna likely drove the distribution of ticks at the landscape scale. Understanding how anthropogenic land use influences where ticks occur is useful for land use planning and for assessing public and animal health risks associated with ticks and tick-borne diseases.

Cattle herd shearing can help to control Rhipicephalus microplus ticks

Given the difficulties of controlling the tick Rhipicephalus microplus due to acaricide resistance, this study aimed to ascertain whether shearing could reduce infestation in cattle. 17 taurine cattle were sheared on the anterior third of one randomly selected side. Shearing was undertaken using a machine with a blade, leaving coats with a thickness of 1 mm. Subsequently, eight evaluations were performed once a week, counting adult females of R. microplus with a diameter > 4.5 mm on the anterior third of both sides (shorn and unshorn). The coat length was also monitored by taking five hair samples from each animal fortnightly (1, 15, 29, 43 and 57 days post shorn) from a central area of both shoulders (shorn and unshorn). The tick counts and hair length data were transformed for normalisation and were analysed using mixed models. The tick and hair length means were significantly higher for the unshorn side. Tick counts were significantly lower on the sheared side until the fifth evaluation, with the final three presenting no differences between the sides. The hair length was significantly lower for the sheared side during the five evaluations. We conclude that as the hair length increased, there was also an increase in the number of ticks on the sheared side. Although this method is not practical for large herds, it can be deemed an option in extreme conditions of tick infestation. In addition, the study reinforces the suggestion that the selection and/or use of cattle with shorter hairs may contribute to reduced tick infestation.

Gene expression during the early stages of host perception and attachment in adult female Rhipicephalus microplus ticks

The cattle tick, Rhipicephalus microplus, is a serious pest of cattle, with significant economic consequences to the livestock industries of tropical and semitropical countries. Rhipicephalus microplus belongs to the Metastriata group of the Ixodidae family known as hard ticks. When adult hard ticks feed, mating has not yet occurred and an initial host attachment phase of 1-2 days is followed by a slow feeding phase that can last several days. Once mating occurs, feeding concludes with a rapid engorgement phase that is completed in 12-36 h. Our group's interest in mining the genome and transcriptome of R. microplus for novel targets for development of tick control technologies led us to investigate the early transcriptional events occurring upon tick attachment and subsequent feeding. We placed newly molted unfed adult R. microplus females upon a bovine host and harvested the attached ticks after 3, 6, 12, and 24 h. We also placed a group of these ticks in a gas-permeable tube taped onto the side of the bovine host. These ticks were able to sense the host but unable to penetrate the tube to begin attachment and were ultimately harvested after 3 h. This study produced a comprehensive transcriptome from newly molted adult ticks and will provide a useful resource for studies of tick feeding and host perception and also assist genome annotation refinements.

Rhipicephalus microplus, babesiosis and anaplasmosis in Uruguay: current situation and control or elimination programs on farms

Rhipicephalus microplus causes high economic losses for Uruguay; the country is divided into a R. microplus-free area and an endemic area. The aim of this research was to evaluate the R. microplus and tick fever situation in Uruguay and the feasibility of implementing R. microplus control or elimination programs to reduce the number of infested farms. A representative survey was performed to determine the number of infested farms, the number of farms with outbreaks of tick fever and the control and preventive measures being used. Control or elimination programs using generational treatment were implemented on 30 farms. Previously, a situation diagnosis was performed by evaluating the background of each farm, identifying acaricide resistance, serologically evaluating the enzootic stability of tick fever, and analyzing the risk of R. microplus introduction to farms. According to the survey, R. microplus was present on 9544 (36%) farms, and 3436 (36%) of these farms experienced outbreaks of tick fever. Only 323 (9.4%) farmers used the tick fever vaccine. Of the 30 farms for which control or elimination programs were carried out, 18 reduced the number of treatments applied per year and six achieved the elimination of the cattle tick. It is concluded that by administering elimination or control programs, it is possible to reduce the number of infested farms and the number of treatments to maintain control. New surveys should be performed to measure the degree of technology adoption by farmers and to analyze the advances in tick control or elimination programs on farms.

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

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

Proteomic analysis of saliva from partially and fully engorged adult female Rhipicephalus microplus (Acari: Ixodidae)

Rhipicephalus microplus salivary gland secretes a number of complex bioactive proteins during feeding. These components are important in feeding and affect anti-coagulation, anti-inflammation and also have anti-microbial effects. In this study, tick saliva was collected from partially engorged female (PEF) and fully engorged female (FEF) ticks. Liquid chromatography tandem-mass spectrometry (LC-MS/MS) and isobaric tags for relative and absolute quantification (iTRAQ) were used to identify and quantify R. microplus salivary proteins. A total of 322 unique peptides were detected and 151 proteins were characterized in both PEF and FEF. Of these, 41 proteins are considered as high-confidence proteins. Fifteen high-confidence proteins were upregulated and six high-confidence proteins were downregulated (p < 0.05; PEF:FEF ratio ≥ 1.2 or PEF:FEF ratio ≤ 0.83); 17 high-confidence proteins are slightly changed (PEF:FEF ratio > 0.83 and < 1.2). These high-confidence proteins are involved in several physiological roles, including egg development, transportation of proteins, immunity and anti-microorganism, anti-coagulant, and adhesion. In comparison with PEF, the number of upregulated proteins exceeded the number of proteins downregulated. Salivary protein may be induced by the blood-meal and these proteins contribute to successful feeding.

Efficacy of winter-spring strategic control against Rhipicephalus (Boophilus) microplus infestations on cattle in an area with ecological conditions highly favourable for the tick in northeast Argentina

This work was performed to test the efficacy of winter-spring control strategies against Rhipicephalus (Boophilus) microplus (Ixodida: Ixodidae) infestations on cattle in the area ecologically most favourable for the development of this tick in Argentina. Two control schemes using three and four annual applications of acaricides, respectively, were evaluated. Animals in Group 1 were treated with ivermectin 3.15% on day 0, fluazuron on day 34, and fipronil on day 85. Animals in Group 2 were treated with ivermectin 3.15% on day 0, fluazuron on day 34, flumethrin on day 85, and fipronil on day 114. Animals in Group 3 represented the control group. Both treatment schemes provided appropriate levels of efficacy against R. microplus and also prevented the occurrence of the major peak in the frequency of this tick in autumn. The two treatment schemes were similar in terms of efficacy and thus the addition of a fourth treatment does not seem to confer any further advantage. The results of this work indicate that these strategic control methods provide appropriate levels of control against R. microplus.

Molecular characterization, tissue-specific expression, and RNA knockdown of the putative heat shock cognate 70 protein from Rhipicephalus haemaphysaloides

Heat shock cognate 70-kDa protein (RH-Hsc70) was identified from a cDNA library synthesized from the sialotranscriptomes of unfed and fed Rhipicephalus haemaphysaloides. The RH-Hsc70 open reading frame is 1950 bp long and encodes a protein that is 649 amino acids in length, with a predicted molecular weight of 71.1 kDa and a theoretical pI of 5.43. RH-Hsc70 exhibits 98% amino acid identity with Hsc70 in Haemaphysalis flava and 83% identity with Hsc70 in arthropods and mammals. RH-Hsc70 was mainly expressed in nymphs and adult ticks, not in larvae. Real-time quantitative PCR analysis indicated that RH-Hsc70 mRNA expression was induced by blood feeding in adult ticks. In addition, RH-Hsc70 gene expression was higher in the ovaries of fed adult ticks than that in the midguts, salivary glands, and fat bodies of unfed or fed adult ticks. RH-Hsc70 gene knockdown inhibited tick blood feeding, significantly decreased tick engorgement rate, and increased tick death rate. These data illustrate the importance of RH-Hsc70 in tick blood feeding and aging, which makes it a promising candidate for the development of anti-tick vaccines.

Nymphal engorgement weight predicts sex of adult Amblyomma americanum, Amblyomma maculatum, Dermacentor andersoni, Dermacentor variabilis, and Rhipicephalus sanguineus ticks

The engorgement weights of laboratory-raised nymphs of five common ticks in the USA, Amblyomma americanum, Amblyomma maculatum, Dermacentor andersoni, Dermacentor variabilis, and Rhipicephalus sanguineus, experimentally fed to repletion on an adult sheep (Ovis aries) were evaluated to determine the sex of molted adult ticks. Length of feeding period of nymphs, molting success and durations, and sex ratios between tick species were also compared. Individual replete nymphs were weighed and allowed to molt to adults in a humidity chamber. Length of feeding duration was different by species (F_4,7785 = 1963.79; P < 0.0001); R. sanguineus nymphs became replete fastest, followed by A. americanum, D. variabilis, A. maculatum, and D. andersoni. Significant difference in molting success was not detected. The mean body weight of engorged nymphs of A. americanum (t = 32.3; df = 662), A. maculatum (t = - 9.70; df = 255), D. variabilis (t = 15.7; df = 751), and R. sanguineus (t = 5.17; df = 560; all P < 0.0001) molting into females was greater than that of nymphs molting into males, whereas heavier D. andersoni engorged nymphs became males (t = 8.71; df = 480; P < 0.0001). Amblyomma maculatum nymphs that molted to females fed to repletion faster (t = 3.33; df = 265; P ≤ 0.001) than nymphs that molted to males and a higher proportion (χ² = 48.4; df = 1, P < 0.0001) of A. maculatum and D. andersoni (χ² = 8.19; df = 1, P = 0.004) molted to females than males. Our study demonstrated biological and behavioral differences in and between engorging nymphs of five ixodid species. These findings may aid in studies evaluating the role of tick sex in transmission of tick-borne pathogens.

Characterisation of cattle anal odour constituents associated with the repellency of Rhipicephalus appendiculatus

Adults of the Brown Ear Tick (Rhipicephalus appendiculatus) have a predilection for feeding inside and around the ears of cattle and other hosts. A previous study has shown that the tick locates the host ears by 'push-pull' deployment of a repellent blend emitted at the anal region and an attractant blend emitted at the ears. Interestingly, the two odours play reverse roles with Rhipicephalus evertsi, which prefer to feed around the anal region. The present study was undertaken to characterize the major constituents of the cattle anal odour and to evaluate their repellence to R. appendiculatus. The anal odour was trapped with reverse-phase C₁₈-bonded silica, Porapak Q and Super Q placed in an oven bag attached at the anal region of the cattle for 6 h. The adsorbents were then removed and extracted with dichloromethane, and the extracted compounds analyzed by linked gas chromatography-mass spectrometry (GC-MS). The major constituents of the odour were o-xylene, 4-hydroxy-4-methyl-2-pentanone, 4-methyl-2-methoxyphenol, ethylbenzene, 2,6,6-trimethyl-[1S(1α,β,5α)]bicycloheptanes, 5-ethoxydihydro-2(3H)-furanone, 3-methylene-2-pentanone, 5-methyl-2-phenyl-1H-indole, and 3-pentanone. The repellency of the available compounds (o-xylene, 4-hydroxy-4-methyl-2-pentanone, 4-methyl-2-methoxyphenol, ethyl benzene, 3-methylene-2-pentanone, and 3-pentanone) and blends was evaluated using a dual choice tick climbing assay at different doses. The anal odour showed repellence with RD₇₅ of 0.39. Of the compounds tested, 4-methyl-2-methoxyphenol was found to be most repellent (RD₇₅ = 0.56) and 3-pentanone least repellent (RD₇₅ = 622.7). The blend of the six constituents showed RD₇₅ of 0.34, comparable to that of the crude anal odour blend. A series of subtractive bioassays with one constituent of the 6-component blend missing was also carried out. Subtraction of 3-methylpentanone gave the most repellent blend (RD₇₅ = 0.097), whereas subtraction of 4-methylguaiacol gave the least repellent blend (RD₇₅ = 160.7) consistent with the high individual activity of this phenol. The study lays down useful groundwork for on-host deployment of controlled-release of a selected repellent or blend to disrupt the tick's ability to locate its preferred feeding site.

Rhipicephalus microplus (Acarina, Ixodidae) in Angola: evidence of its establishment and expansion

Livestock constitutes a fundamental asset for the livelihood of rural communities in Angola. Rhipicephalus microplus (Acarina, Ixodidae) is considered to be the most important external parasite impacting the cattle industry in the world. The present work used a cross-sectional study on tick species infesting cattle in smallholder and commercial farms, to investigate the presence of R. microplus in Angola. This species was found to be recently established in certain areas of Cuanza-Sul and Benguela provinces. Furthermore, taking the current understanding of the pattern of dispersal of R. microplus into account, it is probable that this species is already present in other areas of the country. Animal movement without the necessary control measures facilitates the dispersal of this tick species. Consequently, R. microplus is causing rapid displacement of the native tick species, Rhipicephalus decoloratus. The presence of R. microplus in Angola constitutes a serious problem and poses a potential threat to the livestock sector as well as being an important risk factor for the sustainability of the livelihood strategies developed by smallholders.

Relative transcription of autophagy-related genes in Amblyomma sculptum and Rhipicephalus microplus ticks

Ticks endure stressful off-host periods and perform as vectors of a diversity of infectious agents, thus engaging pathways that expectedly demand for autophagy. Little is known of ticks' autophagy, a conserved eukaryotic machinery assisting in homeostasis processes that also participates in tissue-dependent metabolic functions. Here, the autophagy-related ATG4 (autophagin-1), ATG6 (beclin-1) and ATG8 (LC3) mRNAs from the human diseases vector Amblyomma sculptum and the cattle-tick Rhipicephalus microplus were identified. Comparative qPCR quantifications evidenced different transcriptional status for the ATG genes in the salivary glands (SG), ovaries and intestines of actively feeding ticks. These ATGs had increased relative transcription under nutrient-deprivation, as determined by validation tests with R. microplus embryo-derivative cells BME26 and A. sculptum SG explants incubations in HBSS. Starvation lead to 4-31.8× and ~ 60-500× increments on the ATGs mRNA loads in BME26 and A. sculptum SG explants, respectively. PI3K inhibitor 3MA treatment also affected ATGs expression in BME26. Some ATGs were more transcribed in the SGs than in the ovaries of cattle-ticks. Amblyomma sculptum/R. microplus interspecific comparisons showed that ATG4 and ATG6 were 0.18× less expressed in A. sculptum SGs, but ~ 10-100× more expressed in their ovaries when compared to R. microplus organs. ATG4 and ATG8a transcript loads were ~ 120× and ~ 40× higher, respectively, in A. sculptum intestines when compared to cattle-ticks of similar weight category. ATGs expression in A. sculptum intestines increased with tick weight, indicating Atgs contribution to intracellular blood digestion. Possible roles of the autophagy machinery and their organ-specific expression profile on vector biology are discussed.

Experimental infection of Rickettsia parkeri in the Rhipicephalus microplus tick

This study aimed to evaluate, by means of artificial feeding, the interaction between a pathogenic rickettsia and the hard tick R. microplus. We used partially engorged females fed on calves free of Rickettsia spp. Group 1 (G1), containing 20 ticks, was fed bovine blood only. Group 2 (G2), containing 20 ticks, was fed blood containing uninfected VERO cells, and group 3 (G3), containing 40 ticks, was fed blood containing VERO cells infected with Rickettsia parkeri. Biological parameters of the non-parasitic phase and a possible bacterial transmission to the tick eggs and to guinea pigs were evaluated. At the end of oviposition, all G3 females were PCR-positive for genes specific for the genus Rickettsia. Although no guinea pigs were infected, the experimental infection of R. microplus by R. parkeri caused a deleterious effect on the oviposition and provided the first report of transovarian transmission of rickettsia in this tick.

Expression profile of Rhipicephalus microplus vitellogenin receptor during oogenesis

The vitellogenin receptor (VgR), which belongs to the low-density lipoprotein receptors (LDLR) family, regulates the absorption of yolk protein accumulated in developing oocytes during oogenesis. In the present study, the full sequence of Rhipicephalus microplus VgR (RmVgR) and the partial sequence of Rhipicephalus appendiculatus VgR (RaVgR) ORF were determined and cloned. The RmVgR amino acid sequence contains the five highly conserved structural motifs characteristic of LDLR superfamily members, the same overall structure as observed in other species. Phylogenetic analysis separated VgRs in two major groups, corresponding to receptors from acarines and insects. Consistent with observations from other arthropods, RmVgR was specifically expressed in the ovarian tissue and its peak of expression occurs in females that are detaching from the host. Silencing with RmVgR dsRNA reduced VgR expression, which resulted in reduced fertility, evidenced by a decrease in the number of larvae. The present study confirms RmVgR is a specific receptor involved in yolk protein uptake and oocyte maturation in R. microplus, playing an important role in tick reproduction.

Morphological and molecular identification of Rhipicephalus (Boophilus) microplus in Nigeria, West Africa: a threat to livestock health

The cattle tick Rhipicephalus (Boophilus) microplus was first reported in West Africa in Ivory Coast, in 2007. Since then it has made an aggressive eastward advancement having been reported in four other West African countries: Mali, Burkina Faso, Togo and Benin. We herein report the first molecular identification of this tick species in Nigeria, West Africa, and highlight the threat it poses to livestock health. A nation-wide tick survey was conducted in 12 out of 36 states across the various agro ecological zones of Nigeria over a 1 year period (April 2014-March 2015). In total 1498 ticks belonging to three genera collected from cattle were morphologically identified. Overall, Amblyomma species constituted the highest percentage of sampled ticks, 50.2% (752/1498), followed by Rhipicephalus (including the subgenus Boophilus) species, 29.4% (440/1498) and Hyalomma species, 20.4% (306/1498). The presence of Rh. (B.) microplus was identified morphologically from four out of the 12 states. This finding was confirmed for the first time in Nigeria using a molecular method targeting the ITS-2 region of the ticks in three of the 12 states. This study ascertained the presence of Rh. (B.) microplus in Nigeria in addition to a broad variety of cattle tick species, most of which are of veterinary importance. The implication of this finding is that there may be additional economic burden to livestock farmers due to increased cost of tick control occasioned by the acaricide resistance by this tick species widely reported from different climes. Additionally, there may be a potential upsurge in incidence of hemoparasitic infections in cattle leading to increased morbidity, cost of treatment and mortalities.

Diversity of tick species on domestic animals in Shandong Province, China, using DNA barcoding

Ticks are considered to be second only to mosquitoes as vectors of diseases. In recent years, severe fever with thrombocytopenia syndrome, a new emerging tick-borne disease has been detected in many areas of China, including Shandong Province, Eastern China. Here, we report the tick species diversity based on surveys between 2014 and 2016 covering 16 locations in seven cities of Shandong. Based on DNA barcoding, 1859 ticks belonging to three species were identified: Haemaphysalis longicornis, Rhipicephalus turanicus and Haemaphysalis verticalis. Samples of the same species clustered together in a neighbor-joining phylogenetic tree, with intraspecific distances between 0 and 3.0% and interspecific distances ranged between 15.5 and 24.3%. Goats and dogs were the major hosts of ticks and H. longicornis was regarded as predominant tick species of Shandong. In order to reduce tick populations and prevent tick-borne diseases, effective control measures should be implemented on human and domestic animals, respectively.

Rhipicephalus microplus and Dermacentor nitens (Acari: Ixodidae) Coparasitize White-Tailed Deer on St. John, U.S. Virgin Islands

Ticks parasitizing introduced white-tailed deer, Odocoileus virginianus (Zimmermann), on St. John, U.S. Virgin Islands, were recorded during and after drought conditions. Tick infestation prevalences were 22% at the start of the drought (July 2015), 66% at the height of the drought (March 2016), and 35% after the drought had ended (July 2016; n = 67 deer). Samples of ticks from 22 tranquilized deer in July 2016 revealed the presence of two species, the southern cattle tick, Rhipicephalus (Boophilus) microplus (Canestrini), and the tropical horse tick, Dermacentor (Anocentor) nitens Neumann. Both tick species have considerable veterinary importance, especially for cattle and horses, respectively, as nuisance biters and also as vectors of parasitic piroplasms or of Anaplasma marginale Theiler. All 22 deer examined were infested by R. microplus, whereas 14 (64%) of the samples also included specimens of D. nitens. Because of the large numbers of ticks recorded, wild deer on St. John could develop associated health problems (pruritis, alopecia, anemia, low weight gain, tick-borne pathogens and parasites) and could also serve as a source of these ticks for cattle and horses.

Acaricidal activity of Metarhizium anisopliae isolated from paddocks in the Mexican tropics against two populations of the cattle tick Rhipicephalus microplus

The acaricidal effects of 55 strains of Metarhizium anisopliae (Metschnikoff) Sorokin, 1883 (Hypocreales: Clavicipitaceae) isolated from paddocks of cattle farms were evaluated in two Rhipicephalus microplus (Canestrini 1887) (Ixodida: Ixodidae) populations, of which one was multi-resistant and one was susceptible to chemical acaricides. Percentage mortality and reproductive efficiency indices in R. microplus were evaluated by adult immersion tests at a dose of 1 × 10⁸ conidia/mL for each fungal strain. Some strains were selected to calculate lethal concentrations to kill 50% (LC₅₀ ) and 99% (LC₉₉ ) of engorged ticks. Strains MaV22, MaV26 and MaV55 induced 100% mortality in R. microplus on day 14. Strains MaV05, MaV09 and MaV22 caused mortality of >90% from day 12 onward in both tick populations. The most effective acaricidal fungal strain, MaV55, inhibited egg laying by 54.86 and 55.86% in acaricide-resistant and -susceptible R. microplus populations, respectively. None of the fungal strains had statistically significant effects on larval hatching. In conclusion, nine strains of M. anisopliae demonstrated high acaricidal effects against R. microplus and reduced its egg laying. No differences in acaricidal effects were observed between the two populations of ticks tested.

Population dynamics of the cattle tick Rhipicephalus (Boophilus) microplus in a subtropical subhumid region of Argentina for use in the design of control strategies

The population dynamics of Rhipicephalus microplus (Ixodida: Ixodidae) in northwest Argentina was analysed to support the design of strategic methods for its control. Both parasitic and non-parasitic phases were studied. The seasonal activity of R. microplus in its parasitic phase was characterized by three peaks in abundance: the first in mid-late spring; the second in summer, and the third in autumn. The non-parasitic phase of R. microplus was characterized by a long total non-parasitic period observed after exposures of females from mid-summer to early autumn, a short total non-parasitic period observed after exposures of females from late winter to late spring, a short period of larval longevity in early and mid-summer, and no hatch of the eggs produced by females exposed in mid- and late autumn and winter. Treatments of cattle administered during the period from late winter to late spring will act on small cohorts of R. microplus, preventing the emergence of larger generations in summer and autumn. A 17-week spelling period starting in late spring and early summer will be necessary to achieve optimal control of R. microplus free-living larvae. If spelling begins in mid- or late summer or in autumn, the required period will be 26-27 weeks.

Expression pattern of subA in different tissues and blood-feeding status in Haemaphysalis flava

Tick-borne-diseases (TBD) pose a huge threat to the health of both humans and animals worldwide. Tick vaccines constitute an attractive alternative for tick control, due to their cost-efficiency and environmental-friendliness. Subolesin, a protective antigen against ticks, is reported to be a promising candidate for the development of broad-spectrum vaccines. However, the entire length of its gene, subA, and its gene expression pattern in different tissues and blood-feeding status (or different levels of engorgement) have not been studied extensively. In our study, the full-length of subA in Haemaphysalis flava, Rhipicephalus haemaphysaloides, Rhipicephalus microplus, and Dermacentor sinicus was cloned by RACE-PCR. The subA expression pattern was analyzed further in H. flava in different tissues and blood-feeding status by RT-PCR. We found that the full-length of subA in H. flava, R. haemaphysaloides, R. microplus, and D. sinicus was 1318, 1498, 1316, and 1769 bp, respectively, with encoded proteins at 180, 162, 162, and 166 aa in length, respectively. The primary structure of subolesin in H. flava included three conserved regions and two hypervariable regions, with no signal peptide. SubA expression in female H. flava of different blood-feeding status was in the order of the fasted < the 1/4-engorged < the half-engorged < the fully-engorged (p < 0.01). Tissue expression of subA was in the order of salivary gland > midgut > integument (p < 0.01), but its expression in salivary glands was not statistically different from that in ovaries. We concluded that subolesin was a conserved antigen and that subA was expressed differentially in H. flava in different tissues and blood-feeding status. Those features made subolesin feasible as a potential target antigen for development of a universal vaccine for the control of tick infestations and a reduction in TBD.

Esterase mediated resistance in deltamethrin resistant reference tick colony of Rhipicephalus (Boophilus) microplus

Monitoring of acaricide resistance is considered as one of the important facets of integrated tick management. In an attempt of development of resistance monitoring indicators, in the present study two reference tick lines of Rhipicephalus (Boophilus) microplus maintained in the Entomology laboratory, Indian Veterinary Research Institute (IVRI), Izatnagar, India, were studied to determine the possible contributing factors involved in development of resistance to deltamethrin. Electrophoretic profiling of esterase enzymes detected high activities of EST-1 in reference resistant tick colony designated as IVRI-IV whereas it was not detectable in reference susceptible IVRI-I line of R. (B.) microplus. Esterases were further characterized as carboxylesterase or acetylcholinesterase based on inhibitor study using PMSF, eserine sulphate, malathion, TPP and copper sulphate. It was concluded that an acetylcholinesterase, EST-1, possibly plays an important role for development of deltamethrin resistance in IVRI-IV colony of R. (B.) microplus.

The putative role of Rhipicephalus microplus salivary serpins in the tick-host relationship

Inflammation and hemostasis are part of the host's first line of defense to tick feeding. These systems are in part serine protease mediated and are tightly controlled by their endogenous inhibitors, in the serpin superfamily (serine protease inhibitors). From this perspective ticks are thought to use serpins to evade host defenses during feeding. The cattle tick Rhipicephalus microplus encodes at least 24 serpins, of which RmS-3, RmS-6, and RmS-17 were previously identified in saliva of this tick. In this study, we screened inhibitor functions of these three saliva serpins against a panel of 16 proteases across the mammalian defense pathway. Our data confirm that Pichia pastoris-expressed rRmS-3, rRmS-6, and rRmS-17 are likely inhibitors of pro-inflammatory and pro-coagulant proteases. We show that rRmS-3 inhibited chymotrypsin and cathepsin G with stoichiometry of inhibition (SI) indices of 1.8 and 2.0, and pancreatic elastase with SI higher than 10. Likewise, rRmS-6 inhibited trypsin with SI of 2.6, chymotrypsin, factor Xa, factor XIa, and plasmin with SI higher than 10, while rRmS-17 inhibited trypsin, cathepsin G, chymotrypsin, plasmin, and factor XIa with SI of 1.6, 2.6, 2.7, 3.4, and 9.0, respectively. Additionally, we observed the formation of irreversible complexes between rRmS-3 and chymotrypsin, rRmS-6/rRmS-17 and trypsin, and rRmS-3/rRmS-17 and cathepsin G, which is consistent with typical mechanism of inhibitory serpins. In blood clotting assays, rRmS-17 delayed plasma clotting by 60 s in recalcification time assay, while rRmS-3 and rRmS-6 did not have any effect. Consistent with inhibitor function profiling data, 2.0 μM rRmS-3 and rRmS-17 inhibited cathepsin G-activated platelet aggregation in a dose-responsive manner by up to 96% and 95% respectively. Of significant interest, polyclonal antibodies blocked inhibitory functions of the three serpins. Also notable, antibodies to Amblyomma americanum, Ixodes scapularis, and Rhipicephalus sanguineus tick saliva proteins cross-reacted with the three R. microplus saliva serpins, suggesting the potential of these proteins as candidates for universal anti-tick vaccines.

Ixodicide activity of Eysenhardtia polystachya against Rhipicephalus (Boophilus) microplus

The objective of this study was to evaluate the acaricidal effect of 2 compounds extracted from Eysenhardtia polystachya in vitro, namely coatlines and matlalines. Each extract was obtained by aqueous extraction in a nitrogen atmosphere. Engorged adult females of an amitraz-resistant strain of Rhipicephalus (Boophilus) microplus were used to produce larvae and to carry out the adult immersion test (AIT), while larvae were assayed using the larval packet test (LPT). After exposure to coatlines or matlalines, the mortality of larvae and engorged females, as well as the reproductive parameters of adult ticks were assessed. Coatlines were not lethal against larvae and did not decrease reproductive parameters. Conversely, matlalines showed a 90 to 100% efficacy against adults and larvae at all concentrations tested and a reduction of 76.41 to 80.64% oviposition and a 48.02 to 54.86% reduction in egg hatchability. Therefore, the acaricidal activity of matlalines was more efficient. Further studies are required to elucidate both the mode of action of matlalines as well the structure-activity relationships responsible for the observed differential efficacy between these 2 related isoflavans against the cattle tick.

RNA interference and the vaccine effect of a subolesin homolog from the tick Rhipicephalus haemaphysaloides

Subolesin is a well-characterized protective antigen in many ticks and, thus, it is potentially useful in the development of a broad-spectrum vaccine or an autocidal gene silencing strategy to control tick infestations. A subolesin homolog was cloned from the tick Rhipicephalus haemaphysaloides, which is widespread in China, by rapid amplification of complementary DNA (cDNA) ends. Its full-length cDNA was 1386 base pairs (bp), containing a 483 bp open reading frame with a predicted molecular mass of 18.7 kilodaltons and an isoelectric point of 9.26. The subolesin protein had a typical nuclear localization signal in its amino-terminus. The full-length cDNA of R. haemaphysaloides showed 52 and 80% identities to those from Ixodes scapularis and R. microplus, respectively, whereas amino acid sequence alignments showed 80 and 97% identities, respectively. Native subolesin was recognized in the unfed tick midgut by an antibody against recombinant subolesin. Transcriptional analysis showed that subolesin was expressed in the tick's four developmental stages and in all of the tissues examined, except for the synganglion. The pathogen Babesia microti induced the subolesin transcript by fourfold. Subolesin gene silencing by RNA interference significantly decreased the larval engorgement rate, the attachment rate and body weight of engorged nymphs, and the body weight and attachment and engorgement rates of adults, as well as the egg weight per female tick. Vaccinating mice and rabbits with recombinant subolesin induced a significant protective effect, resulting in a reduction of blood feeding and oviposition. These results encourage further studies of using subolesin to control tick infestations in China.

Rhipicephalus rossicus, a neglected tick at the margin of Europe: a review of its distribution, ecology and medical importance

Rhipicephalus rossicus (Ixodida: Ixodidae) is a three-host tick with a broad host spectrum that includes wild animals, pets, livestock and humans. Despite its local abundance in certain areas, most of the available information on R. rossicus was published decades ago, mainly by former soviet authors. Its distribution largely overlaps the Eurasian steppe. However, its range may be more extensive than is currently known because this species may have been misidentified as Rhipicephalus sanguineus, principally in areas where the latter species is present. Although R. rossicus has been occasionally reported to feed on people, little attention has been given to its medical importance. It has been shown to have a vectorial role in the transmission of Francisella tularensis, Crimean-Congo haemorrhagic fever virus and West Nile virus. However, the vectorial importance of R. rossicus may be significantly greater, mainly as the closely related species R. sanguineus s.l. is known to transmit a very wide spectrum of pathogens. The probably underestimated vectorial role of R. rossicus may represent a hidden public health threat.

Use of Ivermectin as Endoparasiticide in Tropical Cattle Herds Generates Resistance in Gastrointestinal Nematodes and the Tick Rhipicephalus microplus (Acari: Ixodidae)

The objective of the present study was to determine simultaneously the status of resistance against ivermectin (IVM) in gastrointestinal nematodes (GIN) and Rhipicephalus microplus (Canestrini, 1888) ticks in 12 cattle farms where IVM was used for the control of GIN in the Mexican tropics. Six farms had frequent use of IVM (≥ 4 times per year) and six farms had low frequency of IVM use (1-2 times per year). The fecal egg count reduction test and the larval immersion test were used to determine the resistant status of GIN and R. microplus against IVM, respectively. The results indicated that 100% of the surveyed farms had IVM-resistant GIN (reduction % from 0 to 67%). The genera involved were Haemonchus, Cooperia, Ostertagia, Trichostrongylus, and Oesophagostomum. Although the IVM was never used for the control of ticks, 50% of the surveyed farms presented GIN and R. microplus simultaneously resistant to IVM. Furthermore, two R. microplus populations showed high resistance ratio (RR) to IVM (farm TAT: RR50% = 7 and RR99% = 40.1; and farm SLS: RR50% = 2.4; RR99% = 11.0). A high frequency of IVM use (≥ 4 times per year) seemed to promote IVM resistance amongst R. microplus ticks compared with the farms with low frequency of IVM use (1-2 times per year; 66.6 vs. 25.0%, respectively). However, the number of surveyed farms was insufficient to show clear statistical inferences (odds ratio = 6.00; 95% CI = 0.341-105.5). The use of IVM for the control of GIN promoted simultaneously the development of IVM resistance in the GIN and R. microplus populations of the cattle herds surveyed.

Rhipicephalus microplus and Ixodes ovatus cystatins in tick blood digestion and evasion of host immune response

BACKGROUND

Cystatins are a group of cysteine protease inhibitors responsible for physiological proteolysis regulation and present in a wide range of organisms. Studies about this class of inhibitors in parasites have contributed to clarify their roles in important physiological processes, like blood digestion and modulation of host immune response during blood feeding. Thus, cystatins are a subject of research on the development of new parasite control methods. Additionally, the characterization of proteins shared by different parasite species represents a valuable strategy to find potential targets in multi-species control methods. However, cystatin functions in ticks remain undetermined, especially in Rhipicephalus microplus and Ixodes ovatus, two species that affect livestock and human health, respectively.

METHODS

Here we report the inhibitory profile of two R. microplus (BrBmcys2b and BrBmcys2c) and one I. ovatus (JpIocys2a) cystatins to commercial cathepsins B, C, and L. The presence of native cystatins in R. microplus tissues was analyzed using sera against recombinant BrBmcys2b and BrBmcys2c. Also, a peptide from JpIocys2a was synthesized for rabbit immunization, and this serum was used to analyze the cross antigenicity between R. microplus and I. ovatus cystatins.

RESULTS

Enzymatic inhibition profile of tick cystatins shows a distinct modulation for cathepsins related to tick blood digestion and evasion of host immune response. Furthermore, BrBmcys2b was detected in saliva and different tissues along tick stages, while BrBmcys2c was detected mainly in gut from partially engorged R. microplus females, demonstrating a distinct pattern of cystatin expression, secretion and traffic between tick tissues. Moreover, phylogenetic analysis suggests that JpIocys2a belongs to the group of tick gut secreted cystatins. Finally, cross-antigenicity assays revealed that antibodies against the JpIocys2a peptide recognize native and recombinant R. microplus cystatins.

CONCLUSION

The presence of these proteins in different tissues and their ability to differentially inhibit cathepsins suggest distinct roles for JpIocys2a, BrBmcys2b, and BrBmcys2c in blood digestion, egg and larvae development, and modulation of host immune response in tick physiology. The cross-antigenicity between native and recombinant cystatins supports further experiments using JpIocys2a, BrBmcys2b, and BrBmcys2c as vaccine antigens.

A comparison of three different methodologies for evaluating Rhipicephalus (Boophilus) microplus susceptibility to topical spray compounds

This study aimed to compare three different methodologies (Adult Immersion Tests, field trials with naturally infected animals, and a Stall Test using artificially infested cattle) to evaluate the efficacy of two topical formulations that we administered as whole body sprays (15% Cypermethrin+30% Chlorpyriphos+15% Fenthion-Colosso(®) FC 30, Ouro Fino Agronegócios; and 60% Dichlorvos+20% Chlorpyriphos-Ectofós(®), Vallée Saúde Animal Ltd.), against a susceptible strain of Rhipicephalus (Boophilus) microplus. To achieve this objective, two natural infestation trials were conducted, as well as two artificial infestation trials (Stall Tests) and two Adult Immersion Tests (AIT). The AIT results showed that both spray formulations achieved 100% efficacy against R. (B.) microplus fully engorged females. However, when observing results obtained by field trials (natural infestations) and Stall Tests, none of these topically applied compounds reached 100% efficacy or affected the reproductive capacity of the fully engorged female ticks. Additional studies must be conducted to compare these in vivo methodologies with different in vitro techniques, such as the Larval Packet Test. However, based on results obtained here, we can conclude that depending on the spray formulations used, the AIT can overestimate acaricidal efficacy and values of reproductive efficiency of such compounds against R (B.) microplus. Specifically, when dealing with spray formulations in the Stall Tests, the period of residual action can increase because these animals are sheltered from contact with environmental factors that might interfere with the efficacy of the products tested. It may be necessary to take in vivo trial results into consideration (such as field trials with naturally infested animals or Stall Tests) to standardize a specific in vitro assay, such as the Adult Immersion Test.

Influence of tea tree oil (Melaleuca alternifolia) on the cattle tick Rhipicephalus microplus

The aim of this study was to verify the influence of tea tree oil (TTO) (Melaleuca alternifolia) tested in its pure and nanostructured (TTO nanoparticles) forms on the reproduction of female Rhipicephalus microplus. For our purpose, female ticks were collected from naturally infected animals and treated in vitro with TTO (1, 5, and 10 %) and TTO nanoparticles (0.075, 0.375, and 0.75 %). In order to validate the tests, they were performed in triplicate using positive (amitraz) and negative (untreated) controls. It was possible to observe that pure TTO (5 and 10 %) and TTO nanoparticles (0.375 and 0.75 %) showed 100 % reproductive inhibition on female ticks. Additionally, pure TTO (1 %) also showed an acaricide effect (70 %), similarly to the positive control (78.3 %). This is the first study demonstrating the activity of pure TTO and TTO nanoparticles on female ticks. Therefore, based on these results, we were able to show that both forms and all concentrations of M. alternifolia affected tick reproduction by inhibiting egg laying and hatching. We were also able to show that TTO nanoparticles potentiated the inhibitor effect of pure TTO on the reproduction of R. microplus.

Displacement of Rhipicephalus decoloratus by Rhipicephalus microplus (Acari: Ixodidae) in the Eastern Cape Province, South Africa

The objective of the study was to establish to what extent the native tick species Rhipicephalus decoloratus has been displaced by the invasive introduced tick, Rhipicephalus microplus at two communally grazed areas in the Eastern Cape Province, South Africa. To this end ticks were collected monthly from five cattle over a period of 2 years and from 10 drag-samples of the vegetation over a period of 1 year at each locality. Whereas 10 years previously only R. decoloratus and no R. microplus had been recorded in the vicinity of the two sites, R. microplus now comprised the bulk of collections at both. Furthermore, significantly more R. microplus were collected from cattle at both localities during the 2nd year of the survey than during the 1st. In addition to 83 instances of intraspecific coupling, there were 17 instances of R. microplus males coupled with R. decoloratus females. Collections made from cattle and goats on two farms close to the study sites revealed that R. microplus was present on both host species and that it significantly outnumbered R. decoloratus on one of the farms. Rhipicephalus decoloratus and R. microplus larvae as well as larvae exhibiting characteristics of both species were collected from the vegetation.

Effects of wildlife and cattle on tick abundance in central Kenya

In African savannas, large mammals, both wild and domestic, support an abundant and diverse population of tick ectoparasites. Because of the density of ticks and the many pathogens that they vector, cattle in East Africa are often treated with acaricides. While acaricides are known to be effective at reducing tick burdens on cattle, their effects on the overall abundance and community composition of ticks in savanna ecosystems are less well understood. It is also not known how well tick populations can be maintained in the absence of large mammals. We evaluated the effects of wildlife and of acaricide-treated cattle on host-seeking tick populations in a long-term, exclusion experiment in central Kenya. Over seven years, we sampled larval, nymphal, and adult ticks monthly on replicated treatment plots that controlled for the presence of cattle and for the presence of two guilds of large wild mammals: megaherbivores (giraffes and elephants) and all other large wild herbivores (> 15 kg). Two species of ticks were found in this habitat; across all surveys, 93% were Rhipicephalus pulchellus and 7% were R. praetextatus. The presence of acaricide-treated cattle dramatically reduced the abundance of host-seeking nymphal and adult ticks but did not affect the abundance of host-seeking larval ticks. The abundance of larval ticks was determined by the presence of large wild mammals, which appear to import gravid female ticks into the experimental plots. On plots with no large mammals, either wild or domestic, larval and nymphal ticks were rare. Adult R. pulchellus were most abundant in plots that allowed wildlife but excluded cattle. Adult R. praetextatus were relatively abundant in plots without any large mammals. These differences suggest that these ticks utilize different members of the host community. The reduction in ticks that results from the presence of acaricide-treated cattle has potential health benefits for humans and wildlife, but these benefits must be weighed against potential costs, including reduced availability of food for birds such as oxpeckers that feed on ticks.

Red deer (Cervus elaphus) as a host for the cattle tick Rhipicephalus microplus (Acari: Ixodidae) in Yucatan, Mexico

Rhipicephalus microplus is the most economically important cattle tick in the Mexican tropics. Wild ungulate species, including red deer (Cervus elaphus), are gaining popularity in diversified livestock ranching operations in Mexico. However, there is no information available on the susceptibility of red deer to infestation with the cattle tick, R. microplus, under hot, subhumid tropical conditions in Mexico. Biological data on R. microplus as an ectoparasite of cattle and red deer in a farm in the Mexican tropics are presented here. Ticks collected from red deer were identified as R. microplus (97 %) and Amblyomma cajennense (3 %), and tick species infesting cattle included R. microplus (95 %) and A. cajennense (5 %). Standard counts of R. microplus engorged females on red deer were 11 times higher than on cattle (428 ± 43 vs. 40 ± 18; p < 0.001). The reproductive efficiency index and larval hatching of R. microplus collected from cattle and red deer were similar (p > 0.05). Hemolymph samples of R. microplus collected from cattle were positive for Babesia spp. (10 %, 2/50) and all the samples from ticks infesting red deer were negative. Seventeen and ten percent of the blood samples from cattle and red deer were positive for Anaplasma marginale, respectively. The role of red deer as a host of R. microplus in Yucatan, Mexico and the importance of this host-parasite relationship relative to the epidemiology of R. microplus-borne diseases are discussed.

Acaricidal properties of Ricinus communis leaf extracts against organophosphate and pyrethroids resistant Rhipicephalus (Boophilus) microplus

Indian cattle ticks have developed resistance to commonly used acaricides and an attempt has been made to formulate an ecofriendly herbal preparation for the control of acaricide resistant ticks. A 95% ethanolic extract of Ricinus communis was used to test the efficacy against reference acaricide resistant lines by in vitro assay. In in vitro assay, the extract significantly affects the mortality rate of ticks in dose-dependent manner ranging from 35.0 ± 5.0 to 95.0 ± 5.0% with an additional effect on reproductive physiology of ticks by inhibiting 36.4-63.1% of oviposition. The leaf extract was found effective in killing 48.0, 56.7 and 60.0% diazinon, deltamethrin and multi-acaricide resistant ticks, respectively. However, the cidal and oviposition limiting properties of the extract were separated when the extract was fractionated with hexane, chloroform, n-butanol and water. The HPTLC finger printing profile of R. communis leaf extract under λ(max.) - 254 showed presence of quercetin, gallic acid, flavone and kaempferol which seemed to have synergistic acaricidal action. In vivo experiment resulted in 59.9% efficacy on Ist challenge, however, following 2nd challenge the efficacy was reduced to 48.5%. The results indicated that the 95% ethanolic leaf extract of R. communis can be used effectively in integrated format for the control of acaricide resistant ticks.