Exploring the Larvicidal and Repellent Potential of Taurus Cedar (Cedrus libani) Tar against the Brown Dog Tick (Rhipicephalus sanguineus sensu lato).

This study investigated the potential acaricidal and repellent effects of tar obtained from the Lebanon cedar (Cedrus libani A. Rich.) against the brown dog tick species Rhipicephalus sanguineus sensu lato Latreille (Acari: Ixodidae). The goal was to find an alternative, safe, and effective way to eliminate ticks. Tar is traditionally extracted from cedar trees in the Antalya region of Türkiye. The composition of the tar is primarily characterized by a diverse mixture of terpenes, with ß-himachalene (29.16%), α-atlantone (28.7%), ar-turmerone (8.82%), longifolene-(V4) (6.66%), α-himachalene (5.28%), and ß-turmerone (5.12%) emerging as the predominant constituents. The toxic effects of tar on tick larvae were studied through larval immersion tests (LIT), and its repellent activity was evaluated using a new larval repellent activity test (LRAT). The results revealed significant acaricidal effects, with mortality rates of 77.7% and 82.2% for the Konyaalti and Kepez strains of the brown dog tick, respectively, in response to a 1% concentration of tar. LC50 and LC90 values were determined as 0.47% and 1.52% for the Kepez strain and 0.58% and 1.63% for the Konyaalti strain, respectively. When comparing the repellent effect of tar to the widely used synthetic repellent DEET, repellency rates of up to 100% were observed. As a result, this study establishes, for the first time, the larvicidal and repellent effects of C. libani tar on ticks.

Effect of Tagetes minuta essential oil on the central nervous system of unfed Rhipicephalus sanguineus sensu lato 'tropical lineage' ticks.

Rhipicephalus sanguineus sensu lato 'tropical lineage' (Acari: Ixodidae) is considered a sanitary concern due to its role as a disease vector. Tick strains resistant to synthetic acaricides have caused difficulties in their control, besides synthetic acaricides are harmful to the environment and to the health of non-target animals. The research of plants with acaricidal and repellent properties has proved to be an efficient alternative in tick control. The genus Tagetes spp. excels for its use as traditional pest control in households and plantations and also for its potential as an acaricide against R. sanguineus under laboratory conditions. The first aim of the present study was to evaluate the effect of different doses of Tagetes minuta essential oil (TMEO) on the central nervous system (synganglion) in unfed R. sanguineus adults. The histological analysis of synganglion exposed to the different concentrations of TMEO and amitraz 12.5% (50% of the recommended dose in the package insert) showed a significant effect with signs of cell damage including volume increase, loss of shape, and vacuolization, in addition to chromatin alterations such as condensation, margination, and fragmentation. TMEO were analyzed by gas chromatography coupled with mass spectrometry showing the presence of 21 compounds that according to their chemical structure are classified as terpenoids. Among them (Z)-ß-ocimene, ocimene, (Z)-tagetone, and verbenone were found in major quantities.

Dog hair volatiles attract Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) females.

Rhipicephalus sanguineus sensu lato (s.l.) (Latreille) feeds on domestic dogs worldwide. This tick species uses dog volatiles during host-seeking behavior. In this study, we identified volatile compounds from dog hairs involved in the host location of R. sanguineus s.l. The R. sanguineus s.l. females, but not males, were attracted to hair samples and Super Q extracts from Schnauzer dogs in Y-tube olfactometer bioassays. A total of 54 compounds from dog hair extracts were identified by gas chromatography coupled to mass spectrometry, including hydrocarbons, aldehydes, alcohols, ketones, and carboxylic acids. Screening the identified compounds by the single sensillum recording technique showed that isovaleric acid, hexanal, heptanal, and sucaltone (6-methyl-5-hepten-2-one) significantly stimulated the olfactory receptor neurons of the basiconic, chaeticum, and trichodeum sensilla of female ticks. When synthetic compounds were evaluated alone, or in binary, tertiary, or quaternary mixtures, female ticks were only attracted to isovaleric acid and 1 tertiary mixture (hexanal, heptanal, and isovaleric acid). We conclude that isovaleric acid functions as an attractant for R. sanguineus s.l. These findings contribute to the understanding of the chemical ecology of ticks during host location.

Effect of Temperature on Host Preference in Two Lineages of the Brown Dog Tick, Rhipicephalus sanguineus.

Rhipicephalus sanguineus is a species complex of ticks that vector disease worldwide. Feeding primarily on dogs, members of the complex also feed incidentally on humans, potentially transmitting disease agents such as Rickettsia rickettsii, Rickettsia conorii, and Ehrlichia species. There are two genetic Rh. sanguineus lineages in North America, designated as the temperate and tropical lineages, which had occurred in discrete locations, although there is now range overlap in parts of California and Arizona. Rh. sanguineus in Europe are reportedly more aggressive toward humans during hot weather, increasing the risk of pathogen transmission to humans. The aim of this study was to assess the impact of hot weather on choice between humans and dog hosts among tropical and temperate lineage Rh. sanguineus individuals. Ticks in a two-choice olfactometer migrated toward a dog or human in trials at room (23.5°C) or high temperature (38°C). At 38°C, 2.5 times more tropical lineage adults chose humans compared with room temperature, whereas temperate lineage adults demonstrated a 66% reduction in preference for dogs and a slight increase in preference for humans. Fewer nymphs chose either host at 38°C than at room temperature in both lineages. These results demonstrate that risk of disease transmission to humans may be increased during periods of hot weather, where either lineage is present, and that hot weather events associated with climatic change may result in more frequent rickettsial disease outbreaks.

Exposure of Rhipicephalus sanguineus sensu lato Latreille, 1806 (Acari: Ixodidae) to hexane extract of Acmella oleracea (Jambu): semi-engorged and engorged ticks.

The present study analyzed the efficacy of hexane extract of Acmella oleracea against Rhipicephalus sanguineus sensu lato. After exposure of R. sanguineus s. l. female ticks to 14 different concentrations of the hexane extract of A. oleracea, the LC50 was established as 18.135 mg/mL (limits: 16.251-22.675). The effects of the extract were more significant in the ovary of the semi-engorged females, that presented damages in most oocytes. Since such changes would not be repaired, the oocytes could not advance to further stages of development (I-V), thereby causing the inhibition of ovary development, interruption of vitellogenesis, oocyte death and, consequently, infertility. The semi-engorged females also presented extensive damages in the midgut cells, which would prevent (totally or partially) these cells from functioning properly (blood intake and release of nutrients), impairing the ectoparasite nutrition and the viability of the individual. Thus, the hexane extract of A. oleracea can be considered as a promising alternative to chemical control of pests of medical and veterinary importance, due to its efficient acaricidal activity and lesser environmental impact, when used against female ticks in the middle feeding stage.

Sublethal concentrations of acetylcarvacrol affect reproduction and integument morphology in the brown dog tick Rhipicephalus sanguineus sensu lato (Acari: Ixodidae).

Rhipicephalus sanguineus sensu lato (s.l.), also known as the brown dog tick, is among the main tick species involved in the transmission of pathogens to humans and other animals and, therefore, the target of numerous control methods. However, due to the disadvantages of synthetic acaricides, the use of alternative products such as plant derivatives has been encouraged. This study aimed to evaluate the acaricidal potential of acetylcarvacrol and to determine its efficacy at sublethal doses for the control of R. sanguineus s.l. female ticks. In addition, as acetylcarvacrol was applied topically, morphological alterations in the integument were assessed. Acetylation of carvacrol was performed by reaction with acetic anhydride in a sodium hydroxide solution, being confirmed by infrared spectroscopy. The lethal concentration for 50 and 90% (LC50 and LC90) of unfed ticks and the efficacy of acetylcarvacrol in engorged females were determined after the Adult Immersion Test (AIT). For the evaluation of effects of acetylcarvacrol in the integument, routine histological techniques were employed after the AIT. The LC50 and LC90 in unfed females were 2.8 and 7.2 µL/mL, respectively. Regarding reproductive performance, after treatment with 8.0 µL/mL acetylcarvacrol 90.9% control was achieved, as ticks showed the lowest egg production index (EPI), hatching rate (HR), and fecundity rate (FR). In the integument, considerable morphological alterations were observed both in cuticle and epithelium. Thus, acetylcarvacrol affected R. sanguineus s.l. external coating and reproduction when applied at sublethal concentrations, probably contributing to a long-term control.

An exploratory analysis of demography and movement patterns of dogs: New insights in the ecology of endemic Rocky Mountain-Spotted Fever in Mexicali, Mexico.

An outbreak of Rocky Mountain spotted fever (RMSF) transmitted by the brown dog tick (Rhipicephalus sanguineus sensu lato) has emerged as a major human and animal health concern in Mexicali, Mexico. Due to high rates of brown dog tick infestation, susceptibility, and association with humans, dogs serve as sentinels and have a key role in the ecology of RMSF. A cross-sectional household questionnaire study was conducted in six rural and urban locations to characterize dog ecology and demography in RMSF high-and low-risk areas of Mexicali. In addition, we tracked movement patterns of 16 dogs using a GPS data logger. Of 253 households, 73% owned dogs, and dog ownership tended to be higher in high-risk areas, with a mean dog:human ratio of 0.43, compared with 0.3 in low-risk areas. Dogs in high-risk areas had higher fecundity and roamed more, but the dog density and numbers of free-roaming dogs were comparable. There was a higher proportion of younger dogs and lower proportion of older dogs in high-risk areas. The high proportion of immunologically naïve puppies in high risk areas could result in a lack of herd immunity leading to a more vulnerable dog and human population. The marked increase of space use of free-roaming dogs in high-risk areas suggests that unrestrained dogs could play an important role in spreading ticks and pathogens. As means to limit RMSF risk, practical changes could include increased efforts for spay-neuter and policies encouraging dog restraint to limit canine roaming and spread of ticks across communities; due to dog density is less impactful such policies may be more useful than restrictions on the number of owned dogs.

Thymol: Effects on reproductive biology and Gene's organ morphology in Rhipicephalus sanguineus sensu lato engorged females (Acari: Ixodidae).

Thymol is a monoterpene with proven acaricidal activity on different tick species and life stages. The objective of this work was to evaluate the effect of thymol on the reproductive biology of engorged females of Rhipicephalus sanguineus sensu lato and the morphological changes caused in the cells of the tubular and accessory glands of Gené's organ. The females were exposed to thymol by immersion. Seven groups were established: group I (distilled water), group II (30% ethanol), group III (thymol 1.25 mg/mL), group IV (thymol 2.5 mg/mL), group V (thymol 5.0 mg/mL), group VI (thymol 10.0 mg/mL), and group VII (thymol 20.0 mg/mL), with 20 replicates for each treatment. The ticks were kept in a BOD incubator at 27 ±â€¯1 °C and RH > 80 ±â€¯10%. Ten females from each group were evaluated daily until death, and the remaining ten were kept in the incubator under the same conditions for five days and then dissected for the removal of Gené's organ to note possible damage to cell morphology by scanning electron microscopy (SEM) and hematoxylin-eosin (HE) techniques. Thymol demonstrated 63% and 98% efficacy in groups VI (10.0 mg/mL) and VII (20.0 mg/mL), respectively. In these groups, the cells of the tubular and accessory glands of Gené's organ showed signs of damage: irregular eosin staining, rupture and deformation of the cellular limit, presence of fragmented nuclei, changes in cytoplasmic homogeneity and areas with deformation (folds) in the basal region.

Innovative way to dispense pheromones for off-host control of Rhipicephalus sanguineus sensu lato ticks.

Vapour patches dispensing pheromones were evaluated as lures to increase the attractiveness of sticky tick traps for Rhipicephalus sanguineus sensu lato (s.l.). Sex pheromone (SP), assembly pheromone (AP) and a combination of SP + AP at optimal concentrations were impregnated in vapour patches. The responses of the different stages of R. sanguineus s.l. (i.e. larvae, nymphs and adults) to the pheromones were evaluated using a Petri dish bioassay. The impregnated vapour patches were retained as such for a period of two mo and their efficacy was reassessed. In a subsequent field trial, pheromone impregnated vapour patches were placed as lures in bamboo (Bambusa vulgaris) sticky traps designed for the control of ticks in dog kennels. In vitro AP impregnated vapour patches were effective in attracting the different life stages of R. sanguineus s.l. whereas SP was effective in attracting the unfed and fed male stages of R. sanguineus s.l. The field trial revealed that questing and engorged larvae, nymphs and females of R. sanguineus s.l. were attracted more towards AP impregnated vapour patches than SP and AP + SP impregnated vapour patches. Fed and unfed male ticks were lured effectively by SP alone. The combination of SP + AP revealed no potent additive or synergistic effect.

Feeding and respiratory gas exchange of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae).

Ticks are subject to various environmental constrains, such as dehydration, desiccation and long-waiting for hosts to attach. These factors are crucial for tick survival in the environment. Ticks have developed physiological mechanisms and/or strategies that allow adaptability and survival in the environment in which they live, such as spiracle control and cyclical or discontinuous gas exchanges. However, details of gas exchange profile have been reported only in a few tick species in the past. The present study aims to identify and describe respiratory gas exchange patterns in a tropical population of the brown dog tick Rhipicephalus sanguineus sensu lato and effects of blood feeding. Adult female ticks were fed on rabbit hosts. Partially fed (4 to 6 days) and completely fed (> 9 days) ticks were collected daily during feeding, weighed and subjected to CO2 emission measurement at 25 °C using flow-through respirometry. Unfed adult females showed a well-defined periodical burst of CO2 emissions, followed by short periods of low-emission intercepts. The fed groups had drastic changes in respiratory profiles with semi-engorged females showing a high-intensity respiratory pattern alternating between continuous and discontinuous and the engorged females showing a continuous respiratory pattern with high frequency and intensity. The findings from this study contribute to a better understanding of the respiratory physiological process of a tropical population of the dog tick, which may help future investigations on other biological aspects of this ectoparasite and development of control measures.

Unbiased Assessment of Abundance of Rhipicephalus sanguineus sensu lato Ticks, Canine Exposure to Spotted Fever Group Rickettsia, and Risk Factors in Mexicali, México.

An epidemic of Rocky Mountain spotted fever (RMSF) is ongoing in Mexicali, México. We visited 100 neighborhoods with diagnosed human cases and 100 control neighborhoods to evaluate knowledge of the epidemic; obtain data on the spatial distribution of dogs, canine seroprevalence and active infection, tick infestations, and presence of rickettsial DNA in ticks; and evaluate risk factors for human cases, seropositivity, and tick infestation within an unbiased study design. The majority (80%) of residents had heard of RMSF, but only 48% used acaricides in the home or on dogs. Case neighborhoods and those with high canine seroprevalence tended to be on the city periphery or in the agricultural valley. No dogs were polymerase chain reaction (PCR) positive for Rickettsia rickettsii, and the overall seroprevalence was 65% (titers from 64 to 1,024). PCR prevalence in ticks was 0.70%, confirmed by DNA sequencing as R. rickettsii; neighborhood prevalence ranged from 0.7% to 6.1%. Twelve percent of dogs had high tick burdens, and all ticks were Rhipicephalus sanguineus. Epidemiologically significant risk factors were ground covering for a neighborhood having a human case; dogs having poor body condition and weighing < 10 kg for canine seropositivity; dogs living at the home for the number of ticks in the environment; and being near canals, having trash on the patio, and a dog being thin for tick burdens on dogs. A One Health approach is crucial to understanding RMSF and brown dog ticks.

Comparison of in-vitro bioassays for evaluation of the response of different stages of Rhipicephalus sanguineus sensu lato to calcium alginate encapsulated pheromone beads.

Tick sex pheromone (SP), assembly pheromone (AP) and their combination (SP + AP) were encapsulated in calcium alginate beads. In vitro bioassays, namely Petri dish and olfactometer assays, were employed to estimate the level of attraction of the various stages of Rhipicephalus sanguineus sensu lato, namely unfed and engorged (fed) larvae, nymphs, females, and males to the different pheromones. The study revealed that only the Petri dish assay was suitable to evaluate the response of larval stages whereas the olfactometer bioassay could also be used for evaluating the response of all other stages. Attraction to pheromone encapsulated calcium alginate beads of all tick stage was higher in the Petri dish assay than in the olfactometer assay.

Ticks and associated pathogens from dogs in northern Vietnam.

The medical and veterinary significance of ticks and tick-borne pathogens (TBPs) in tropical and subtropical zones is well recognized. Although ticks and TBPs are known to occur in Southeast Asia, limited data is available in the international literature for some countries, such as Vietnam. The aim of this study was to investigate the species of ticks and TBPs associated with dogs in northern Vietnam. Out of 359 dogs enrolled in this study, 26.2% (n = 94) were infested by 466 ticks (i.e., 287 males, 139 females, 30 nymphs, and 10 larvae). All ticks were morphologically identified as Rhipicephalus sanguineus sensu lato, and some of them genetically characterized as belonging to the tropical lineage. A total of 302 ticks were molecularly screened for the detection of selected TBPs. Three ticks were positive for Hepatozoon canis, one for Ehrlichia canis, and one for Babesia vogeli, representing the first molecular characterization of these pathogens in Vietnam. In conclusion, the tropical lineage of R. sanguineus s.l. is the dominant tick taxon infesting dogs from northern Vietnam, where different TBPs are circulating.

Records of ticks on humans in Rio Grande do Sul state, Brazil.

More than seventy tick species have been reported in Brazil. Despite the emergence of tick-borne diseases in Neotropical region, there are still limited data available on tick species parasitizing humans in Brazil. Rio Grande do Sul is the southernmost state of Brazil, comprising the only part of Brazilian territory inside the Pampa biome, as well as the transition between subtropical and temperate zones. Here, we report on human parasitism by ticks in Rio Grande do Sul state between 2004 and 2017. Seventy cases of human parasitism by ticks were recorded, with a total of 81 tick specimens collected. These included 11 tick species belonging to three genera of Ixodidae (hard-ticks), Amblyomma, Haemaphysalis and Rhipicephalus; and one genus of Argasidae, Ornithodoros. The most prevalent tick species associated to cases of human parasitism were Amblyomma parkeri (24%), Rhipicephalus sanguineus sensu lato (22%), Amblyomma aureolatum (15%) and Amblyomma ovale (12%). A spatial analysis showed two major hot spots of human parasitism by ticks in Rio Grande do Sul state. The findings of this study highlight the need for permanent monitoring of human parasitism by ticks in order to provide a better understanding of tick and tick-borne disease eco-epidemiology, and the early identification of potential cases of tick-borne diseases, particularly in spotted fever endemic regions.

Infestation of Rhipicephalus sanguineus sensu lato on cats in Malta.

Studies on cats as hosts of Rhipicephalus sanguineus sensu lato (s.l.) are scarce. Cats are regarded as infrequent hosts of this species complex, and usually only when dogs are also present. In order to compare the occurrence of developmental stages and mitochondrial DNA haplotypes of R. sanguineus s.l. on cats and other domestic or synanthropic mammalian species, 540 ticks were collected from cats, dogs, hedgehogs and one goat. Collections were made from April to September in 2016 and 2017, from 20 locations in Malta in southern Europe. The sampling sites included six cat colonies, where no dogs were present. Compared to adults, significantly more immatures of R. sanguineus s.l. were found on cats (123 larvae and nymphs versus 10 adults) than on dogs (190 larvae and nymphs versus 173 adults). Furthermore, compared to nymphs, significantly more larvae of R. sanguineus s.l. were found on cats (50 larvae versus 73 nymphs) than on dogs (11 larvae versus 179 nymphs). Adult ticks predominated on male dogs (42 adults versus 28 larvae or nymphs), whereas immatures were significantly more abundant compared to adult ticks on female dogs (142 larvae or nymphs versus 80 adults). Similarly, immature as compared with adult ticks were significantly more likely to occur on female cats (72 immature ticks versus 1 adult) in comparison with male cats (46 immature ticks versus 8 adults). Moreover, R. sanguineus s.l. larvae were found significantly more frequently as compared with nymphs on female cats (38 larvae versus 34 nymphs) than on male cats (12 larvae versus 34 nymphs). To confirm morphological identification and to compare mitochondrial markers (cytochrome c oxidase subunit 1 [cox1] and 16S rRNA genes) of ticks across hosts, 57 ticks were analysed. The amplified parts of the cox1 and 16S rRNA genes of R. sanguineus s.l. collected from various hosts showed 100% sequence identity with each other and with those in GenBank from the middle to western Mediterranean Basin. In conclusion, the present study highlights that cats can be important hosts of the immature life stages of R. sanguineus s.l., even in the absence of dogs. This finding has veterinary-medical significance, because stray cats and free-roaming cats may transport immature stages of R. sanguineus s.l. into gardens, i.e. near dogs and humans.

Possible Northward Introgression of a Tropical Lineage of Rhipicephalus sanguineus Ticks at a Site of Emerging Rocky Mountain Spotted Fever.

Increasing rates of Rocky Mountain spotted fever (RMSF) in the southwestern United States and northern Mexico underscore the importance of studying the ecology of the brown dog tick, Rhipicephalus sanguineus, the vector in that region. This species is reported to comprise distinct tropical and temperate lineages that may differ in vectorial capacity for RMSF and are hypothesized to be limited in their geographical range by climatic conditions. In this study, lineage was determined for ticks from 9 locations in California, Arizona, and Mexico by DNA sequencing of 12S, 16S, and D-loop ribosomal RNA. As expected, sites in northern California and eastern Arizona had temperate-lineage ticks, and phylogenetic analysis revealed considerable genetic variability among these temperate-lineage ticks. However, tropical-lineage ticks extended north from Oaxaca, Mexico were well established along the entire border from San Diego, California to western Arizona, and were found as far north as Lytle Creek near Los Angeles, California (a site where both lineages were detected). Far less genetic variability in the tropical lineage despite the large geographical distances is supportive of a hypothesis of rapid northward expansion. Discovery of the tropical lineage north of the identified climatic limitations suggests that more work is needed to characterize this tick's ecology, vectorial capacity, expansion, possible evolution, and response to climate change.

A Molecular Survey of Rickettsias in Shelter Dogs and Distribution of Rhipicephalus sanguineus (Acari: Ixodidae) sensu lato in Southeast Turkey.

Canine tick-borne pathogens are the source of emerging diseases and have important zoonotic relevance. Dogs play a major role in the transmission of several zoonotic tick-borne pathogens, as reservoirs and/or sentinels. To simultaneously detect Anaplasma and Ehrlichia species, a reverse line blot assay was conducted on 219 blood samples collected from autochthonous asymptomatic shelter dogs. One hundred and three (47.0%, CI 40.3-53.9) dogs were positive for one or both rickettsial pathogens. Seventy-one (32.4%, CI 26.3-39.0) dogs were infected with Anaplasma platys and 23 (10.5%, CI 6.8-15.3) with Ehrlichia canis. Concurrent infection with A. platys and E. canis was detected in nine (4.1%, CI 1.9-7.6) dogs. Partial sequences of the 16S ribosomal RNA gene shared 100% identity with the corresponding published sequences for A. platys and E. canis. Infection with Anaplasma phagocytophilum was not detected in the examined dogs. In total, 1018 (range 1-70, mean intensity 13.1, mean abundance 4.6) Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) sensu lato ticks (45.7% nymphs, 54.3% adults) were collected from the dogs. There was no significant association between Anaplasma/Ehrlichia infection and dog sex or age, but a significant correlation was found between rickettsia infection and presence of R. sanguineus. Improved tick control strategies to reduce the risk of these pathogens spreading among dogs and humans are needed in the region.

Water immersion of dogs close to the time of topical fluralaner treatment does not reduce efficacy against a subsequent experimental challenge with Rhipicephalus sanguineus (sensu lato).

BACKGROUND: Fluralaner is a novel systemic ectoparasiticide for dogs and cats providing immediate and persistent flea- and tick-control after a single topical dose. Prescribing directions recommend waiting 72 h following topical administration before immersing dogs in water. The objective of this study was to determine whether water immersion immediately prior to treatment or earlier than 72 h post-treatment reduced subsequent treatment efficacy. METHODS: Forty (n = 40) dogs were blocked on tick carrying capacity into 5 experimental groups and all but one of the groups (untreated control) were treated topically with fluralaner (Bravecto® Spot-On Solution, Merck Animal Health, Madison, NJ, USA) at the commercial dose. Three of the four remaining groups were immersed in 38-40 °C water for a 5 min bath - either 1 h before treatment; 12 h after treatment; or 24 h after treatment. Seven days after treatment all dogs were challenged with 50 Rhipicephalus sanguineus (sensu lato) ticks and after 24 h attached ticks were counted and removed. RESULTS: Efficacies (compared to the untreated control group) were: 99.3% for no water immersion; 99.6% for immersion 1 h before treatment; 99.3% for immersion 12 h after treatment; and, 100% for immersion 24 h after treatment. CONCLUSIONS: Water immersion of dogs around the time of topical fluralaner administration did not reduce subsequent systemic acaricidal efficacy.

Interaction between saliva's adenosine and tick parasitism: effects on feeding and reproduction.

BACKGROUND: It has recently been demonstrated that saliva from Rhipicephalus sanguineus ticks contains adenosine (ADO) and prostaglandin E2 (PGE2), two non-protein molecules that have significant immunomodulatory properties. These molecules can inhibit cytokine production by dendritic cells (DCs), while also reducing the expression of CD40 in these cells. However, more studies are needed for a better understanding of their participation in the feeding of ticks in vivo. This work, therefore, evaluated the importance of ADO during tick infestations. Mice were infested with adult ticks (3 couples/mouse), and their skin was collected at the tick-infested site (3rd and 7th day), and mRNA for receptors of ADO was quantified by real-time PCR. RESULTS: Tick infestation increased by four and two times the expression of the A2b and A3v1 receptors on day 3, respectively, while expression of other ADO receptors was unaltered. In addition, we treated mice (n = 10/group) daily with 8-(p-Sulfophenyl)theophylline, 8-pSPT, 20 mg/kg, i.p.), a non-selective antagonist of ADO receptors, and evaluated the performance of ticks during infestations. Female ticks fed on 8-pSPT-treated mice presented a reduction in their engorgement, weight and hatching rates of egg masses, and survival times of larvae compared to the same parameters presented by ticks in the control group. To investigate if these 8-pSPT-treated mice presented altered immune responses, we performed three tick infestations and collected their lymph node cells to determine the percentages and activation state of DCs and cytokine production by lymphocytes by flow cytometry (Cytometric Bead Array technique, CBA). Our data showed that 8-pSPT-treated mice presented an increase in the percentage of DCs as well as of their stimulatory and co-stimulatory molecules (CD40, CD80 and MHCII). Regarding production of T cell cytokines, we observed a significant increase in the levels of IL-2 and a significant decrease in IL-10, IL-17, TNF-α and IFN-γ cytokines. CONCLUSIONS: These results suggest that ADO produced by ticks helps them feed and reproduce and that this effect may be due to modulation of host DCs and T cells.

The effects of neem oil (Azadirachta indica A. JUSS) enriched with different concentrations of azadirachtin on the integument of semi-engorged Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) females.

Several studies searching for methods to control Rhipicephalus sanguineus s.l., (dog tick) infestations have been developed aiming to minimize the damages caused by these ectoparasites to the hosts and the environment, which is harmed by the indiscriminate use of toxic acaricide products. In this scenario, neem oil has been used as a natural alternative against ticks, once this chemical has repellent properties and interferes in the growth regulation of these ectoparasites, inhibiting ecdysis. The present study evaluated the effects of azadirachtin-enriched neem oil on the integument of semi-engorged R.sanguineus s.l., females through morphohistological techniques. The results showed the occurrence of significant morphological and histochemical alterations, mainly in the females exposed to higher concentrations, which demonstrates the dose-dependent action of the chemical. A decrease in the cuticle thickness was observed, as well as a modification in the distribution of the epithelial cells, which displayed pyknotic and fragmented nuclei, and intensely vacuolated cytoplasm, indicating that these cells would be undergoing death processes. These morphological alterations observed in the integument of the females exposed to the azadirachtin-enriched neem oil encourage the use of this chemical as a strategy to control these ectoparasites.