Tick Attachment Research Articles

Indirect Effects of Japanese Barberry Infestations on White-Footed Mice Exposure to Borrelia burgdorferi.

Japanese barberry (Berberis thunbergii de Candolle; Ranunculales: Berberidaceae) is an exotic shrub that has invaded woodland understories in the northeastern United States. It forms dense thickets providing ideal structure and microclimate for questing blacklegged ticks (Ixodes scapularis Say; Acari: Ixodidae). While there have been studies on the favorable habitat barberry provides blacklegged ticks, little has been studied on the relationship between barberry, vectors (ticks), and reservoirs (white-footed mice; Peromyscus leucopus Rafinesque; Rodentia: Cricetidae); specifically, the influence Japanese barberry has on the abundance of blacklegged ticks and Borrelia burgdorferi infection (Johnson, Schmid, Hyde, Steigerwalt, and Brenner; Spirochaetales: Spirochaetaceae) in mice. We studied the impacts of barberry treatment over the course of 6 yr to determine influence on encounter abundance with white-footed mice, encounter abundance with B. burgdorferi-infected mice, and juvenile blacklegged ticks parasitizing mice. Results from our study suggest that while both white-footed mouse and B. burgdorferi-infected mouse encounters remained similar between barberry treatment areas, juvenile tick attachment to mice was significantly greater in intact barberry stands (X¯ = 4.4 ticks per mouse ± 0.23 SEM) compared with managed (X¯ = 2.8 ± 0.17; P < 0.001) or absent (X¯ = 2.2 ± 0.16; P < 0.001) stands. Results of this study indicated that management of barberry stands reduced contact opportunities between blacklegged ticks and white-footed mice. Continued efforts to manage Japanese barberry will not only allow for reestablishment of native plant species, but will also reduce the number of B. burgdorferi-infected blacklegged ticks on the landscape.

Detection of Borrelia in Ixodes scapularis ticks by silver stain, immunohistochemical and direct immunofluorescent methods.

Lyme disease (LD) is one of the most common tick-borne diseases caused by several Borrelia species of spirochetes. Ixodes scapularis is responsible for the transmission of LD in the northeastern United States. The rate of infection varies with the duration of tick attachment to the host; however, this information may be unknown. In skin biopsies, it is often difficult to identify spirochetes. Testing of ticks is not routinely performed. Treatment is established by clinical presentation. To test paraffin-embedded I. scapularis ticks for Borrelia by different methods. We examined 20 paraffin-embedded ticks by silver stain, immunohistochemical (IHC) and direct immunofluorescent (DIF) methods and compared the percentage of positivity with DIF results from the Connecticut Agricultural Experiment Station. The results were similar by DIF, which proved to be the most sensitive method, followed by the silver stain and IHC. We found that the identification of spirochetes in paraffin-embedded ticks was less difficult than in tissue with a comparable turnaround time to that of a routine biopsy. Timely identification of Borrelia in ticks may influence the clinical management of the patients.

Preventing tick attachment to dogs using essential oils

Preventing tick bites using repellents could make a valuable contribution to an integrated tick management programme for dogs. Here, the ability of a range of essential oils or active ingredients of commercially available repellents, to abolish the orientation and taxis of the tick Ixodes ricinus towards sebum extracted from dog hair was examined in laboratory bioassays. Substantial differences between oils were observed, but turmeric oil was both able to prevent a climbing response by ticks and had a longer residual activity than other oils. A blanket-drag field assay was then used to compare the attachment of ticks to blankets impregnated with one of: turmeric oil, DEET (positive control), orange-oil or excipient only (negative controls). In total, 899 ticks were counted, with an average of 23.3 (SD ± 21.3) ticks per blanket drag for excipient-only (n = 16), 26.9 (SD ± 28.6) for orange oil (n = 16), 2.6 (SD ± 2.0) for turmeric oil (n = 16) and 3.4 (SD ± 3.7) for DEET (n = 16). Finally, in a participatory in vivo trial, tick acquisition by 15 untreated control dogs was compared with 24 dogs sprayed with turmeric-oil and 16 dogs sprayed with orange oil (both 2.5% v/v diluted in water with a 1% coco glucoside excipient) before each walk in known tick infested areas. The percentage of dogs with ticks attached to the legs or belly of dogs sprayed with turmeric oil suspension (15% ± 19.4%) was significantly lower than that of ticks attached to the same areas of dogs sprayed with orange oil suspension (85% ± 19.4%) and unsprayed dogs (73% ± 26.2%) (P < 0.05). The data indicate that turmeric-oil may form a valuable component of a tick management programme for domestic dogs.

Ticks on snakes: The ecological correlates of ectoparasite infection in free‐ranging snakes in tropical Australia

Parasites profoundly influence the lives of their hosts, yet the dynamics of host-parasite interactions are poorly understood - especially in reptiles. We examined the ecological correlates of parasitism by ixodid ticks in an assemblage of 10 snake species in tropical Australia. In total, we recorded 3803 ticks on 1841 individual snakes of six species (no ticks were found on the other species). Molecular analyses confirmed the tropical reptile tick (Amblyomma fimbriatum: Ixodidae) to be the most common snake tick at our study site, with inter- and intraspecific variation in tick prevalence and intensity. Tick attachment sites were random on most snake species, but both male and female ticks congregated on the heads of the colubrid snake Boiga irregularis and the python Simalia amethistina. In these same species, tick loads were higher on snakes captured in woodland than in rainforest. Females of two python species (Aspidites melanocephalus and S.amethistina) had higher tick loads than did males. In B.irregularis, individuals captured in the dry season had higher tick loads than those captured in the wet season. In most parasitized snake species, larger individuals had greater tick loads. Data from snake recaptures confirmed individual tick burdens frequently varied, with little correlation between tick loads on the same snake at successive captures (except for B.irregularis). Finally, tick intensity was not correlated with (and thus, presumably did not influence) the body condition of any snake species in our study. Use of specific types of refuge sites may strongly influence tick loads on snakes in this system.

Local immune response to larvae of Rhipicephalus microplus in Santa Gertrudis cattle.

This study investigated the local immune response at larval attachment sites in Santa Gertrudis cattle with low and high levels of tick resistance. Skin samples with tick larvae attached were collected from Santa Gertrudis cattle at the end of a period of 25 weekly infestations, when the animals manifested highly divergent tick-resistant phenotypes. There was a tendency for more CD3+ , CD4+ , CD8+ , CD25+ , γδ T cells and neutrophils to concentrate at larval tick attachment site in susceptible cattle than in resistant cattle but the differences were significant only for γδ T cells and CD4+ cells. Most of the cattle developed intra-epidermal vesicles at the larval attachment site but the predominant cell within or around the vesicles was the neutrophil in susceptible animals and eosinophil in the resistant animals. The monoclonal antibodies (mAbs) specific for CD45 and CD45 RO antigens reacted with skin leucocytes from a higher number of susceptible cattle than resistant cattle. Our data suggest that some of the cellular responses mounted at larval attachment site are not involved in tick protection. The mAbs specific for CD45 and CD45 RO directly, or a test for CD45 genotype might be developed as markers of tick susceptibility or resistance.

Experimental infection in Cavia porcellus by infected Amblyomma ovale nymphs with Rickettsia sp. (Atlantic rainforest strain).

This study describes experimental infection of guinea pigs (Cavia porcellus) infested with naturally infected Amblyomma ovale nymphs with Rickettsia sp. (Atlantic rainforest strain), and the capacity of A. ovale nymphs to transmit this bacterium. Twenty-six guinea pigs were divided into the following groups: G1, 10 animals infested with uninfected A. ovale nymphs; G2, 10 animals infested with nymphs infected with Rickettsia sp. (Atlantic rainforest strain); and G3, 6 animals without tick infestation. Blood samples were taken 7, 14, 21, and 28days post-infestation for serological and hematological tests. For histopathological analysis and rickettsial DNA detection, fragments of the spleen, lung, brain, and liver were harvested after euthanasia. The average feeding period for nymphs was 6.6days for G1 and 6days for G2. Hemolymph and PCR assays, performed to detect the causative agent in ticks, indicated that in G1, all ticks were negative, and in G2, all nymphs were positive by PCR and 80% (8/10) was positive by hemolymph tests. The only clinical change was skin scarring at the tick attachment site. Hematological parameters indicated leukopenia and total plasma protein (TPP) increased with decreased platelets in G1. In G2, leukocytosis, neutrophilia, monocytosis, an increase in platelets, and reduced TPP were observed. Only G2 guinea pigs were seroconverted (80%; 8/10). Histopathology tests indicated mild, diffuse hemosiderosis and mild, multifocal, follicular hyperplasia in the spleen. Molecular analysis did not detect Rickettsia sp. DNA in C. porcellus tissues. We demonstrated the capacity of A. ovale nymphs to transmit Rickettsia sp. (Atlantic rainforest strain) to guinea pigs.

Tick attachment cement-reviewing the mysteries of a biological skin plug system.

ABSTRACTThe majority of ticks in the family Ixodidae secrete a substance anchoring their mouthparts to the host skin. This substance is termed cement. It has adhesive properties and seals the lesion during feeding. The particular chemical composition and the curing process of the cement are unclear. This review summarizes the literature, starting with a historical overview, briefly introducing the different hypotheses on the origin of the adhesive and how the tick salivary glands have been identified as its source. Details on the sequence of cement deposition, the curing process and detachment are provided. Other possible functions of the cement, such as protection from the host immune system and antimicrobial properties, are presented. Histochemical and ultrastructural data of the intracellular granules in the salivary gland cells, as well as the secreted cement, suggest that proteins constitute the main material, with biochemical data revealing glycine to be the dominant amino acid. Applied methods and their restrictions are discussed. Tick cement is compared with adhesives of other animals such as barnacles, mussels and sea urchins. Finally, we address the potential of tick cement for the field of biomaterial research and in particular for medical applications in future.

Efficacy trial of three pour-on acaricides on external parasites of cattle in Zaria, Nigeria

External parasites cause adverse effects on livestock production globally. In a study to determine the efficacy of three acaricides, fifteen pastoralist herds were randomly selected. Each herd had a group with eight cattle and three other groups with four. All animals were screened for external parasites pre-acaricide application. Groups 1, 2 and 3 were assigned to 1% Fipronil (Topline®), 0.5% Ivermectin and 5% Cypermethrin, respectively. Group 4 animals were untreated control. Observation of earmarked animals was twice weekly for seven weeks. Results showed that Musca domestica and Stomoxys sp died instantly and were repelled from herds for four weeks. No new tick attachment on experimental animals four weeks post application. Ticks were absent in Group 1 six weeks post application. Lice died 3 days post application in all experimental groups, while the animal with demodecocis in Group 1 had regression of lesions week 2 post application. Hair re-growth was observed in affected animals by week 4. Only a meager regression of demodecocislessions was observed in animals in other groups. The study demonstrated that the three acaricides had both therapeutic and prophylactic effects on external parasites, but Fipronil (Topline®) had longer prophylactic and better curative effects than the other two acaricides. It is, therefore, recommended that Fipronil (Topline®) should be reliably used for the control of external parasite in cattle because of its broader spectrum of activity and longer lasting effect.Keywords: Efficacy; Topline®; external parasites, Nigeria

Targeting a global health problem: Vaccine design and challenges for the control of tick-borne diseases.

It has been over twenty years since the first vaccines for the control of tick infestations became commercially available. These vaccines proved their efficacy and the potential of this approach for the control of tick-borne diseases (TBDs), which represent a growing burden for human and animal health worldwide. In all these years, research in this area has produced new tick-derived and pathogen-derived candidate protective antigens. However, the potential of vaccines for the control of TBDs has been underestimated due to major challenges to reduce tick infestations, pathogen infection, multiplication and transmission, tick attachment and feeding time and/or host pathogen infection. Nevertheless, vaccines constitute the most safe and effective intervention for the control of TBDs in humans, domestic and wild animals.

Tick-Borne Viruses and Biological Processes at the Tick-Host-Virus Interface.

Ticks are efficient vectors of arboviruses, although less than 10% of tick species are known to be virus vectors. Most tick-borne viruses (TBV) are RNA viruses some of which cause serious diseases in humans and animals world-wide. Several TBV impacting human or domesticated animal health have been found to emerge or re-emerge recently. In order to survive in nature, TBV must infect and replicate in both vertebrate and tick cells, representing very different physiological environments. Information on molecular mechanisms that allow TBV to switch between infecting and replicating in tick and vertebrate cells is scarce. In general, ticks succeed in completing their blood meal thanks to a plethora of biologically active molecules in their saliva that counteract and modulate different arms of the host defense responses (haemostasis, inflammation, innate and acquired immunity, and wound healing). The transmission of TBV occurs primarily during tick feeding and is a complex process, known to be promoted by tick saliva constituents. However, the underlying molecular mechanisms of TBV transmission are poorly understood. Immunomodulatory properties of tick saliva helping overcome the first line of defense to injury and early interactions at the tick-host skin interface appear to be essential in successful TBV transmission and infection of susceptible vertebrate hosts. The local host skin site of tick attachment, modulated by tick saliva, is an important focus of virus replication. Immunomodulation of the tick attachment site also promotes co-feeding transmission of viruses from infected to non-infected ticks in the absence of host viraemia (non-viraemic transmission). Future research should be aimed at identification of the key tick salivary molecules promoting virus transmission, and a molecular description of tick-host-virus interactions and of tick-mediated skin immunomodulation. Such insights will enable the rationale design of anti-tick vaccines that protect against disease caused by tick-borne viruses.

Predicting the risk of Lyme borreliosis after a tick bite, using a structural equation model.

BackgroundUnderstanding and quantification of the risk of Lyme borreliosis after a tick bite can aid development of prevention strategies against Lyme borreliosis.MethodsWe used 3,525 single tick bite reports from three large prospective studies on the transmission risk of tick-borne pathogens to humans, with 50 reports of Lyme borreliosis during the follow-up period, among 1,973 reports with known outcome. A structural equation model was applied to estimate the risk of Lyme borreliosis after a tick bite, and quantify the influence of: developmental stage of the tick, detection of Borrelia burgdorferi s.l. DNA in the tick by PCR, tick engorgement, patient-estimated duration of tick attachment, and patient age.ResultsThe overall risk of developing Lyme borreliosis after a tick bite was 2.6% (95%CI 1.4–5.1).The risk increased with:- Tick engorgement: 1.4% (95%CI 0.7%-2.3%) for low engorgement to 5.5% (95%CI 2.8%-9.2%) for substantially engorged ticks;- Rising patient-estimated tick attachment duration: 2.0% (95%CI 1.3%-2.8%) after <12 hours, to 5.2% (95%CI 3.0%-8.9%) after ≥4 days;- Detection of Borrelia burgdorferi s.l. DNA in ticks: 6.7% (95%CI 3.6%-13.5%), versus 1.4% (95%CI 0.7%-2.9%) when ticks tested negative.The highest observed risk of Lyme borreliosis was 14.4% (95%CI 6.8%-24.6%) after one tick bite of a substantially engorged tick that tested positive for Borrelia burgdorferi s.l. DNA, which corresponds to one new case of Lyme borreliosis per 7 (95%CI 4–15) of such tick bites.ConclusionsAn individual's risk of Lyme borreliosis after a tick bite can be predicted with tick engorgement, patient-estimated duration of tick attachment, and detection of Borrelia burgdorferi s.l. DNA in the tick.

Transmission of the Lyme Disease Spirochete Borrelia mayonii in Relation to Duration of Attachment by Nymphal Ixodes scapularis (Acari: Ixodidae).

The recently recognized Lyme disease spirochete, Borrelia mayonii, has been detected in host-seeking Ixodes scapularis Say ticks and is associated with human disease in the Upper Midwest. Although experimentally shown to be vector competent, studies have been lacking to determine the duration of time from attachment of a single B. mayonii-infected I. scapularis nymph to transmission of spirochetes to a host. If B. mayonii spirochetes were found to be transmitted within the first 24 h after tick attachment, in contrast to Borrelia burgdorferi spirochetes (>24 h), then current recommendations for tick checks and prompt tick removal as a way to prevent transmission of Lyme disease spirochetes would need to be amended. We therefore conducted a study to determine the probability of transmission of B. mayonii spirochetes from single infected nymphal I. scapularis ticks to susceptible experimental mouse hosts at three time points postattachment (24, 48, and 72 h) and for a complete feed (>72-96 h). No evidence of infection with or exposure to B. mayonii occurred in mice that were fed upon by a single infected nymph for 24 or 48 h. The probability of transmission by a single infected nymphal tick was 31% after 72 h of attachment and 57% for a complete feed. In addition, due to unintended simultaneous feeding upon some mice by two B. mayonii-infected nymphs, we recorded a single occasion in which feeding for 48 h by two infected nymphs resulted in transmission and viable infection in the mouse. We conclude that the duration of attachment of a single infected nymphal I. scapularis tick required for transmission of B. mayonii appears to be similar to that for B. burgdorferi: transmission is minimal for the first 24 h of attachment, rare up to 48 h, but then increases distinctly by 72 h postattachment.

Serologic responses to peptides of Anaplasma phagocytophilum and Borrelia burgdorferi in dogs infested with wild-caught Ixodes scapularis

Anaplasma phagocytophilum and Borrelia burgdorferi are both transmitted by Ixodes spp. and are associated with clinical illness in some infected dogs. This study evaluated canine antibody responses to the A. phagocytophilum p44 peptides APH-1 and APH-4 as well as the B. burgdorferi C6 peptide before and after doxycycline treatment. A total of eight dogs were infested with wild-caught I. scapularis for 1 week. Blood was collected prior to tick attachment and from Days 3–77 to 218–302 with doxycycline treatment beginning on Day 218. Blood was assayed for A. phagocytophilum DNA by PCR assay. Sera was assessed for antibodies by immunofluorescent antibody (IFA) test and ELISA. Anaplasma phagocytophilum DNA was amplified from blood of all dogs by Day 7. Antibodies to APH-4 were detected in serum as early as 14days after tick exposure and six dogs had APH-4 antibodies detected 3–7 days before antibodies against APH-1. All dogs were seropositive for A. phagocytophilum from Days 218 to 302. Antibodies to B. burgdorferi were detected in 6/8 dogs beginning 21days after I. scapularis infestation. Among the five dogs that remained seropositive at Day 218, C6 antibody levels declined on average 81% within 84days of initiating treatment. The results suggest that the APH-4 peptide may be more useful than APH-1 for detecting antibodies earlier in the course of an A. phagocytophilum infection. After doxycycline administration, C6 antibody levels but not APH-1 or APH-4 antibody levels decreased, suggesting a treatment effect on C6 antibody production.

Epidemiological study of tick infestation in buffalo of various regions of district Khairpur, Pakistan

Aim::The aim of this study was to determine the epidemiological infestation and identification of Ixodidae and Argasidae ticks species in buffalo of different parts of district Khairpur, Pakistan.Materials and Methods::A total of 720 Water buffaloes from three tehsils (subdivisions) were selected randomly and examined from organized and unorganized dairy farms for tick infestation in district Khairpur, Pakistan. This epidemiological survey was conducted during April to September 2015.Results::The overall mean population and preferred site of tick attachment to infested animals, in Gambat, Sobhodero, and Kot Diji tehsils, were observed on different body parts. The primary body area of infestation by ticks (head, thorax, abdomen, udder, and tail) ranged from highest in tail and udder part compared to lowest in the abdomen, head, and thorax. In all study areas, the infestation was higher (p<0.05) in tail and udder than other parts of the body. In all the study areas, the overall highest population was found in the month of July. In addition, we first time identify four new species of ticks (Hyalomma anatolicum, H. anatolicum excavatum, Hyalomma Ixodes excavatum, and Ixodes ricinus) in district Khairpur, Pakistan.Conclusion::Results of this study provide additional information of epidemiological tick infestation, and will be helpful for evolving effective control policy for the management of tick infestation in study district.

Do Tick Attachment Times Vary between Different Tick-Pathogen Systems?

Improvements to risk assessments are needed to enhance our understanding of tick-borne disease epidemiology. We review tick vectors and duration of tick attachment required for pathogen transmission for the following pathogens/toxins and diseases: (1) Anaplasma phagocytophilum (anaplasmosis); (2) Babesia microti (babesiosis); (3) Borrelia burgdorferi (Lyme disease); (4) Southern tick-associated rash illness; (5) Borrelia hermsii (tick-borne relapsing fever); (6) Borrelia parkeri (tick-borne relapsing fever); (7) Borrelia turicatae (tick-borne relapsing fever); (8) Borrelia mayonii; (9) Borrelia miyamotoi; (10) Coxiella burnetii (Query fever); (11) Ehrlichia chaffeensis (ehrlichiosis); (12) Ehrlichia ewingii (ehrlichiosis); (13) Ehrlichia muris; (14) Francisella tularensis (tularemia); (15) Rickettsia 364D; (16) Rickettsia montanensis; (17) Rickettsia parkeri (American boutonneuse fever, American tick bite fever); (18) Rickettsia ricketsii (Rocky Mountain spotted fever); (19) Colorado tick fever virus (Colorado tick fever); (20) Heartland virus; (21) Powassan virus (Powassan disease); (22) tick paralysis neurotoxin; and (23) Galactose-α-1,3-galactose (Mammalian Meat Allergy-alpha-gal syndrome). Published studies for 12 of the 23 pathogens/diseases showed tick attachment times. Reported tick attachment times varied (&lt;1 h to seven days) between pathogen/toxin type and tick vector. Not all studies were designed to detect the duration of attachment required for transmission. Knowledge of this important aspect of vector competence is lacking and impairs risk assessment for some tick-borne pathogens.

Transmission of Borrelia miyamotoi sensu lato relapsing fever group spirochetes in relation to duration of attachment by Ixodes scapularis nymphs

Borrelia miyamotoi sensu lato relapsing fever group spirochetes are emerging as causative agents of human illness (Borrelia miyamotoi disease) in the United States. Host-seeking Ixodes scapularis ticks are naturally infected with these spirochetes in the eastern United States and experimentally capable of transmitting B. miyamotoi. However, the duration of time required from tick attachment to spirochete transmission has yet to be determined. We therefore conducted a study to assess spirochete transmission by single transovarially infected I. scapularis nymphs to outbred white mice at three time points post-attachment (24, 48, and 72h) and for a complete feed (>72–96h). Based on detection of B. miyamotoi DNA from the blood of mice fed on by an infected nymph, the probability of spirochete transmission increased from 10% by 24h of attachment (evidence of infection in 3/30 mice) to 31% by 48h (11/35 mice), 63% by 72h (22/35 mice), and 73% for a complete feed (22/30 mice). We conclude that (i) single I. scapularis nymphs effectively transmit B. miyamotoi relapsing fever group spirochetes while feeding, (ii) transmission can occur within the first 24h of nymphal attachment, and (iii) the probability of transmission increases with the duration of nymphal attachment.

The immunomodulatory protein RH36 is relating to blood-feeding success and oviposition in hard ticks

An immunomodulatory protein designated RH36 was identified in the tick Rhipicephalus haemaphysaloides. The cDNA sequence of RH36 has 844bp and encodes a deduced protein with a predicted molecular weight of 24kDa. Bioinformatics analysis indicated that RH36 presented a degree of similarity of 34.36% with the immunomodulatory protein p36 from the tick Dermacentor andersoni. The recombinant RH36 (rRH36) expressed in Sf9 insect cells suppressed the T-lymphocyte mitogen-driven in vitro proliferation of splenocytes and the expression of several cytokines such as IL-2, IL-12, and TNF-α. Furthermore, the proliferation of splenocytes isolated from rRH36-inoculated mice was significantly lower than that in control mice, suggesting that rRH36 could directly suppress immune responses in vivo. In addition, microarray analysis of splenocytes indicated that the expression of several immunomodulatory genes was downregulated by rRH36. The silencing of the RH36 gene by RNAi led to a 37.5% decrease in the tick attachment rate 24h after placement into the rabbit ears, whereas vaccination with RH36 caused a 53.06% decrease in the tick engorgement rate. Unexpectedly, RNAi induced a significant decrease in the oviposition rate, ovary weight at day 12 after engorgement, and egg-hatching rate. The effects of RH36 on blood feeding and oviposition were further confirmed by vaccination tests using the recombinant protein. These results indicate that RH36 is a novel member of immunosuppressant proteins and affects tick blood feeding and oviposition.

Characterization of the early local immune response to Ixodes ricinus tick bites in human skin.

Little is known about the immunomodulation by tick saliva during a natural tick bite in human skin, the site of the tick-host interaction. We examined the expression of chemokines, cytokines and leucocyte markers on the mRNA levels and histopathologic changes in human skin biopsies of tick bites (n=37) compared to unaffected skin (n=9). Early tick-bite skin lesions (<24hours of tick attachment) were characterized by a predominance of macrophages and dendritic cells, elevated mRNA levels of macrophage chemoattractants (CCL2, CCL3, CCL4) and neutrophil chemoattractants (CXCL1, CXCL8), of the pro-inflammatory cytokine, IL-1β, and the anti-inflammatory cytokine, IL-5. In contrast, the numbers of lymphocytes and mRNA levels of lymphocyte cell markers (CD4, CD8, CD19), lymphocyte chemoattractants (CXCL9, CXCL10, CXCL11, CXCL13, CCL1, CCL22), dendritic cell chemoattractants (CCL20), and other pro- (IL-6, IL-12p40, IFN-γ, TNF-α) and anti-inflammatory cytokines (IL-4, IL-10, TGF-β) did not differ from normal skin. With longer tick attachment (>24hours), the numbers of innate immune cells and mediators (not significantly) declined, whereas the numbers of lymphocytes (not significantly) increased. Natural tick bites by Ixodes ricinus ticks initially elicit a strong local innate immune response in human skin. Beyond 24hours of tick attachment, this response usually becomes less, perhaps because of immunomodulation by tick saliva.

A Novel Ex Vivo Bioassay Suggests DEET is an Effective Repellent of Rhipicephalus Sanguineus1

Ticks are vectors that pose a threat to public health. N,N-diethyl-3-methylbenzamide (DEET) is commonly applied as a repellent to prevent attachment of ticks to humans and animals. Typical commercially available repellents contain between 5–100% DEET. Lower concentrations of DEET may be necessary to minimize potential health risks associated with DEET. To characterize the repellency of low concentrations of DEET, we performed an in vitro vertical bioassay, and developed a novel ex vivo vertical bioassay using porcine skin for use with the adult brown dog tick, Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae). DEET applied at concentrations of 0.19% in vitro and 12.5% ex vivo immediately after application, and at 0.38% in vitro and 40% ex vivo at 4 h after application, repelled over 90% of ticks. In both in vitro and ex vivo assessments, and at both 0 and 4 h post application, the repellency against female ticks was similar to that against male ticks. This study demonstrates that concentrations of DEET lower than those in commercial repellents may provide sufficient repellency when potential tick exposure occurs shortly after application. Additionally, the development of a porcine ex vivo bioassay provides an alternative assessment tool for future repellency studies.

Tick attachment sites in humans living in the Tokat province of Turkey

Tick attachment sites in humans living in the Tokat province of Turkey