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PubMed2004

Lyme borreliosis agents and the genetics and sex of their vector, Ixodes ricinus.

The tick Ixodes ricinus is responsible for the transmission and maintenance of a wide variety of pathogenic organisms in the Northern Hemisphere, among which Lyme disease represents a major threat to humans. Despite numerous studies, the epidemiology of the different bacterial species responsible for this disease remains unclear. Recent evidence for a sex-biased genetic structure of its European vector leads us to analyse the consequences of this pattern on Borrelia transmission. Here we show that male and female ticks are not equivalently infected by Borrelia burgdorferi, that Borrelia afzelii affects tick migration capabilities, especially for the most vagile sex (i.e., male) and that Lyme borreliosis agents are consequently vectorised in a much more complex way than usually thought. Such results change the epidemiological perception of Lyme borreliosis and suggest new co-evolutionary pathways between the ticks and the borrelia.

Animals↗

PubMed2005

Investigation of the mechanisms of anti-complement activity in Ixodes ricinus ticks.

The feeding success of a tick upon a host depends on its ability to suppress host anti-tick responses which include activation of the complement system. We investigated the mechanism of inhibition of the alternative pathway of complement by salivary gland extract (SGE) of the ixodid tick species, Ixodes ricinus. SGE treatment strongly inhibited C3a generation and factor B cleavage in serum when rabbit erythrocytes were used as complement activator, but not when cobra venom factor (CVF) was used as an activator. SGE treatment strongly inhibited C3b deposition on rabbit erythrocytes, and the turnover of C3 (to C3b/iC3b) in serum. However, there was no significant effect upon the formation, stability or activity of C3 convertase (C3bBb) when formed from purified C3b, factor B and factor D. SGE treatment of isolated C3 resulted in a shift in mobility of the alpha-chain (by about 5 kDa). N-terminal sequencing of this species suggests that cleavage occurs at the C-terminus of the alpha-chain of C3. Consistent with this hypothesis, the modified alpha-chain was still a substrate for pre-formed convertase. The activity was specific for the alpha-chain of C3 but not of C3(H2O) nor the alpha'-chain of C3b. It is proposed that SGE-modified C3 does not participate in convertase formation, probably having a reduced affinity for factor B.

Animals↗

PubMed2005

A novel antimicrobial peptide from salivary glands of the hard tick, Ixodes sinensis.

A novel antimicrobial peptide named as ixosin was isolated from the salivary glands of the hard tick, Ixodes sinensis, by gel filtration, ion exchange chromatography and reverse-phase high-performance liquid chromatography (RP-HPLC). Its amino acid sequence was determined as GLHKVMREVLGYERNSYKKFFLR by Edman degradation and its molecular weight was 2870.5 analyzed by fast atom bombardment (FAB) mass spectrometry. This is the first antimicrobial peptide from ticks that lacks cysteine in its primary structure. The cDNA encoding ixosin was cloned by cDNA library screening. The predicted protein from the cDNA sequence composed of 79 amino acids including mature ixosin. Purified ixosin exerted its antimicrobial activities against bacteria and fungi. No similarity was found by BLAST search to any database entries and, thus, our findings describe a novel antimicrobial peptide.

Amino Acid Sequence↗

PubMed2005

Repelling properties of some plant materials on the tick Ixodes ricinus L.

The repellent effects on nymphal stages of Ixodes ricinus L. of some plant materials have been studied in the laboratory. The plant material consisted of an ethanolic extract from Achillea millefolium L., and volatile oils of birch and/or pine tar, citronella, cloves, eucalyptus, geranium, lavender, lily of the valley and peppermint. The most pronounced effects were observed for the oils of citronella, cloves and lily of the valley. They possessed repelling activities of the same magnitude as the reference repellent DEET (N,N-diethyl-m-toluamide). Some major constituents of these oils, e.g. citronellol and geraniol (oil of citronella and lily of the valley) and eugenol (oil of cloves) showed pronounced repelling effects. This was also the case for phenethyl alcohol, a minor component in the oil from lily of the valley.

Achillea↗

PubMed2005

The Ixodes scapularis Genome Project: an opportunity for advancing tick research.

The Ixodes scapularis Genome Project (IGP), the first to sequence a tick genome, will provide an unparalleled resource for studying tick biology and tick-host-pathogen relationships, and identifying novel targets for tick and tick-borne disease control. The IGP will be the first genomic analysis of a member of the subphylum Chelicerata and will accelerate the pace of tick research. The challenge for scientists is to translate IGP data into public health benefits.

Animals↗

PubMed2004

A symbiont of the tick Ixodes ricinus invades and consumes mitochondria in a mode similar to that of the parasitic bacterium Bdellovibrio bacteriovorus.

We have recently performed molecular characterisation of an intracellular alpha-proteobacterium, named IricES1, which resides in the ovarian tissue of female Ixodes ricinus ticks from Italy. A unique characteristic of this bacterium is its ability to invade the mitochondria of the cells in which it resides. Although some ultrastructural studies have been performed on close relatives of this bacterium from I. ricinus in England and Switzerland, a number of questions remain about its movement within ovarian tissues and mitochondria. We have performed the first detailed ultrastructural examination of IricES1 in engorged female adult I. ricinus. Among our findings was that the bacterium enters mitochondria in a similar way to that employed by the 'predatory' bacterium Bdellovibro bacteriovorus, that is, between the inner and outer membranes. It then appears to multiply, with the new 'colony' consuming the mitochondrial matrix. Despite having many of their mitochondria consumed, oocytes appear to develop normally, and the bacteria are likely to be vertically transferred to all eggs.

Animals↗

PubMed2004

Cardiovascular effects of the toxin(s) of the Australian paralysis tick, Ixodes holocyclus, in the rat.

An extract of toxin(s) from the Australian paralysis tick, Ixodes holocyclus, produced positive inotropic responses in rat left ventricular papillary muscles and positive contractile responses in rat thoracic aortic rings. There was no measurable chronotropic response in rat right atria, but positive inotropic concentrations in papillary muscles produced arrhythmias in right atria. Positive inotropic responses were attenuated by verapamil, but unaffected by metoprolol, cimetidine, pyrilamine, tetrodotoxin and pinacidil. Microelectrode studies on isolated left ventricular papillary muscles demonstrated that the extract prolonged action potential duration at 20, 50 and 90% of repolarisation and delayed ventricular papillary muscle relaxation. Cardiovascular tissues isolated from rats with experimentally induced tick paralysis showed no myocardial damage as identified by histological and ultrastructural examination. The basal rate and force of contraction of isolated cardiac tissues were lower from tick-paralysed than normal rats. Concentration-response curves to dobutamine and calcium chloride were similar between tissues from tick-paralysed and normal rats. Thus, the Australian paralysis tick, I. holocyclus, produces one or more toxins with direct cardiovascular effects which mimic the effects produced by direct blockade of cardiac and vascular K+ channels.

Action Potentials↗

PubMed2005

Vaccination with recombinant tick antigens for the control of Ixodes scapularis adult infestations.

Antigens protective against Ixodes scapularis infestations were identified by cDNA expression library immunization (ELI) and analysis of expressed sequenced tags (EST). Three cDNAs protective against larval tick infestations, 4F8, with homology to a nucleotidase, and 4D8 and 4E6 of unknown function, were characterized and obtained as recombinant proteins for immunization studies. Vaccination trials with recombinant proteins demonstrated an effect of these antigens against I. scapularis larvae in a mouse model. Herein, we evaluated the effect of recombinant antigens on I. scapularis adult infestations on immunized sheep. Vaccination with recombinant 4D8, 4F8, 4E6 and the combination of all three antigens reduced adult tick infestations by 58, 12, 20, and 16%, respectively, when compared to the control group but was statistically significant for 4D8 and 4F8 only. Oviposition was reduced by 22-49% in all groups immunized with recombinant tick antigens (P<0.05). The overall efficacy of vaccine formulations considering the effect on tick infestations and oviposition averaged 33-71%. These antigens, and especially 4D8, appear to be good candidates for continued development of a vaccine for control of tick infestations.

Animals↗

PubMed2005

Spatial distribution of Dermacentor reticulatus and Ixodes ricinus in Hungary: evidence for change?

A survey was conducted to investigate the spatial distribution of Ixodes ricinus and Dermacentor reticulatus in Hungary and to compare these data with the results of a previous large-scale survey. In the survey conducted in the 1950s, D. reticulatus adults were detected in two isolated areas of two counties, and the presence of these ticks in the collection was explained by accidental introduction. In the present survey, D. reticulatus became the second most common species occurring in all 16 counties involved in the monitoring and showed high prevalence. The change in the spatial distribution of this tick species, the increase of incidence of Babesia canis infection in Hungary, and the increasing number of canine babesiosis case reports from other Central and Central Eastern European countries since the 1970s suggest an expansion of the geographic range of D. reticulatus and intensification of the transmission rate of B. canis and probably other D. reticulatus-borne diseases (e.g. tularemia and tick-borne lymphadenopathy) in the region. The spatial distribution of I. ricinus was roughly in line with the results of the earlier survey. I. ricinus was the most common tick species being present in all 16 counties with the highest prevalence. Nevertheless, the comparison of the data of the previous and current survey cannot be used for fine-scale analysis; thus, it cannot be dismissed that the spatial distribution of I. ricinus also changed during the past decades. The spatial distribution patterns of tick-borne encephalitis in Hungary and other Central Eastern European countries may indicate such a change.

Animals↗

PubMed2005

Acaricidal properties of the essential oil of Melaleuca alternifolia Cheel (tea tree oil) against nymphs of Ixodes ricinus.

The aim of the study was to examine the acaricidal effect of essential oil of Melaleuca alternifolia (tea tree oil, TTO) at different doses (4, 6, 8 and 10 microl) and for different exposure times (30, 60, 90 and 120 min) on nymphs of Ixodes ricinus. A dose of 8 microl TTO was lethal for more than 70% of ticks when inhaled and this effect was enhanced when the dose was increased to 10 microl (> 80%). The effect was correlated with the duration of exposure of ticks to TTO, with a significant effect being observed after 90 min exposure. The findings show that TTO has acaricidal properties and could be extremely useful in controlling ticks that are efficient vectors of pathogens.

Animals↗

PubMed2005

Experimental inoculation of beagle dogs with Ehrlichia species detected from Ixodes ovatus.

Three beagle dogs were inoculated with mice spleen/liver homogenate infected with Ehrlichia species detected from Ixodes ovatus (EIO) and one dog was used as a control. All three infected dogs did not show clinical signs of disease except for mild pyrexia throughout the 41-day study period. Splenomegaly was observed from Day 7 post-inoculation (p.i.) in two of the dogs. Hematological and biochemical abnormalities included mild thrombocytopenia, hypoproteinaemia, hypoalbuminaemia and increased C-reactive protein values. One of the dogs' splenic aspirate sample was PCR-positive for Ehrlichia Day 7 p.i. and another dogs' blood and bone marrow aspirate sample was PCR-positive Day 41 p.i. Sequence analysis of the PCR products showed 100% homology with the 16SrRNA partial gene sequence of Ehrlichia sp. HF565. Antibody titers to EIO were observed in all three experimentally infected dogs starting from the first week p.i. and cross-reactivity with Ehrlichia canis was detectable in one of the dogs starting Day 7 p.i. These data suggest that infection of dogs with EIO is possible, though is probably of low pathogenic importance. Cross-reactivity of EIO infected dog serum with E. canis raises the likelihood of false E. canis seropositive dogs.

Animals↗

PubMed2006

Temporal distribution of Ixodes ricinus, Dermacentor reticulatus and Haemaphysalis concinna in Hungary.

A survey was carried out over a 4-year period to describe the temporal distribution of three 'anthropophilic' tick species, Ixodes ricinus, Dermacentor reticulatus and Haemaphysalis concinna in Hungary. Altogether 4658 adult ticks belonging to the three species were collected from 1931 red foxes (Vulpes vulpes) killed in an area of about 70,000 km(2) representing all major climatic areas of the country. The seasonal activity of the three species was different. I. ricinus ticks were most active between April and June with an activity peak in May. A less marked increase of activity was also observed in September and October. The highest activity of D. reticulatus ticks was seen between September and November with an activity peak in October, nevertheless, a marked increase of activity could also be observed in April. Small number of I. ricinus and D. reticulatus were collected in all other months. H. concinna ticks were active from May to July with an activity peak in June and completely disappeared between October and March. The temporal distribution of the three tick species might be used for predictions on the seasonality of tick-borne diseases in Hungary.

Animals↗

PubMed2003

Cloning of a salivary gland metalloprotease and characterization of gelatinase and fibrin(ogen)lytic activities in the saliva of the Lyme disease tick vector Ixodes scapularis.

The full-length sequence of tick salivary gland cDNA coding for a protein similar to metalloproteases (MP) of the reprolysin family is reported. The Ixodes scapularis MP is a 488 amino acid (aa) protein containing pre- and pro-enzyme domains, the zinc-binding motif HExxHxxGxxH common to metalloproteases, and a cysteine-rich region. In addition, the predicted amino-terminal sequences of I. scapularis MPs were found by Edman degradation of PVDF-transferred SDS/PAGE-separated tick saliva proteins, indicating that these putative enzymes are secreted. Furthermore, saliva has a metal-dependent proteolytic activity towards gelatin, fibrin(ogen), and fibronectin, but not collagen or laminin. Accordingly, I. scapularis saliva has a rather specific metalloprotease similar to the hemorrhagic proteases of snake venoms. This is the first description of such activity in tick saliva and its role in tick feeding and Borrelia transmission is discussed.

Amino Acid Sequence↗

PubMed2001

Life cycle of the tick Ixodes uriae in penguin colonies: relationships with host breeding activity.

A survey of the temporal pattern of population structure and feeding activity of the seabird tick Ixodes uriae was conducted for the first time in two host species colonies: King penguin (Aptenodytes patagonicus halli) and Macaroni penguin (Eudyptes chrysolophus chrysolophus). The life cycle of the tick was investigated over 3 years in a King penguin colony and 2 years in a Macaroni penguin colony at Possession Island (Crozet Archipelago). There was a marked seasonal feeding activity pattern of ticks in both host species, connected with the presence of birds during the breeding season. Although the King penguin colonies were occupied throughout the year by birds, the favourable period for engorgement was limited to 3.5-4.5 months, and almost all the ticks overwintered in the unengorged state. Consequently, I. uriae probably completed its life cycle over 3 years in King penguin colonies. In contrast, this life cycle could be shortened to 2 years in Macaroni penguin colonies, as a result of a different timetable of the presence of birds for breeding and moulting. The relationships between such plasticity and the host behaviour and subantarctic climatic conditions are discussed.

Animals↗

PubMed2002

An empirical quantitative framework for the seasonal population dynamics of the tick Ixodes ricinus.

The wide geographic and climatic range of the tick Ixodes ricinus, and the consequent marked variation in its seasonal population dynamics, have a direct impact on the transmission dynamics of the many pathogens vectored by this tick species. We use long-term observations on the seasonal abundance and fat contents (a marker of physiological ageing) of ticks, and contemporaneous microclimate at three field sites in the UK, to establish a simple quantitative framework for the phenology (i.e. seasonal cycle of development) of I. ricinus as a foundation for a generic population model. An hour-degree tick inter-stadial development model, driven by soil temperature and including diapause, predicts the recruitment (i.e. emergence from the previous stage) of a single cohort of each stage of ticks each year in the autumn. The timing of predicted emergence coincides exactly with the new appearance of high-fat nymphs and adults in the autumn. Thereafter, fat contents declined steadily until unfed ticks with very low energy reserves disappeared from the questing population within about 1 year from their recruitment. Very few newly emerged ticks were counted on the vegetation in the autumn, but they appeared in increasing numbers through the following spring. Larger ticks became active and subsequently left the questing population before smaller ones. Questing tick population dynamics are determined by seasonal patterns of tick behaviour, host-contact rates and mortality rates, superimposed on a basal phenology that is much less complex than has hitherto been portrayed.

Animals↗

PubMed1999

Increased mortality of black-browed albatross chicks at a colony heavily-infested with the tick Ixodes uriae.

At Bird Island, South Georgia, we studied the effects of the tick Ixodes uriae on survival of chicks at two colonies of the black-browed albatross Diomedea melanophrys, one where most chicks were infested with ticks, the other where most chicks were tick-free. When the two colonies were compared, it was found that the colony heavily-infested with ticks had significantly greater chick mortality than the colony lightly-infested with ticks. However, within each of the two colonies, there was no significant difference in survival between chicks with ticks and those without ticks.

Animals↗

PubMed2003

Identification of protective antigens for the control of Ixodes scapularis infestations using cDNA expression library immunization.

Identification of antigens that induce an immune response against tick infestations is required for the development of vaccines against these economically important ectoparasites. In order to identify protective antigens, we constructed a cDNA expression library from a continuous Ixodes scapularis cell line (IDE8) that was initially derived from tick embryos. cDNA clones were subjected to several rounds of screening in which mice were immunized with individual pools and then challenge-exposed by allowing I. scapularis larvae to feed on the immunized and control mice. Immunity against tick infestation was determined by the reduction in the ability of the larvae to feed to repletion and molt to the nymphal stage. Individual clones in pools that induced immunity to larval infestations were partially sequenced and grouped according to their putative protein function by comparison with sequence databases. The screening identified several individual antigens that induced a protective immune response against I. scapularis infestations. Our studies demonstrated for the first time that cDNA expression library immunization (ELI) combined with sequence analysis is a powerful and efficient tool for identification of candidate antigens for use in vaccines against ticks.

Animals↗

PubMed1997

Immunization with a polyvalent OspA vaccine protects mice against Ixodes ricinus tick bites infected by Borrelia burgdorferi ss, Borrelia garinii and Borrelia afzelii.

Sequence variability of the outer surface protein (Osp) A among Borrelia burgdorferi sl species suggests that a monovalent OspA vaccine may not protect against the various Borrelia present in Eurasia. Here, we confirmed that a monovalent recombinant OspA (rOspA) vaccine does not protect mice against Ixodes ricinus mediated infection with B. burgdorferi ss, Borrelia garinii and Borrelia afzelii. However, when mice were vaccinated with a cocktail of various rOspA from these three species, they were protected, and all challenge ticks that fed on them were cleared of their spirochetes. These results showed that a multiple OspA antigens vaccine, compatible with human use, was very efficient at protecting mice against B. burgdorferi ss, B. garinii, and B. afzelii.

Animals↗