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At least 1,063 records · Page 59Linked to original sources
PubMed1995

Seasonal variation in the role of grey squirrels as hosts of Ixodes ricinus, the tick vector of the Lyme disease spirochaete, in a British woodland.

Data are presented on the variable patterns of the seasonal dynamics of Ixodes ricinus L. ticks seen questing on the vegetation and feeding on small rodents (mice and voles) and squirrels within a British woodland focus of Lyme borreliosis. Information on tick infestation levels on pheasants is also presented. The results show a prolonged, unimodal pattern of tick activity, with ticks feeding throughout the year in this sheltered habitat. If host density is taken into account, squirrels are quantitatively more important than small mammals as hosts for larval ticks from April until July, and overwhelmingly so for nymphal ticks throughout the year. The observed inter- and intraspecific differences in tick infestation levels are related to the behaviour of both hosts and ticks. Squirrels, as competent hosts for Borrelia burgdorferi and frequent occupants of habitats closely associated with man, will contribute significantly to the risk of Lyme disease.

Animals↗
PubMed1999

Towards a permanent solution for controlling cattle ticks.

Acaricides are essential in the short-term but do not offer a permanent solution to tick control. This situation will not change without a change of approach. A vaccine against Boophilus microplus confers partial long-term control but has little immediate effect on tick burdens. The effectiveness of acaricides and vaccination is greatest for breeds of high tick resistance. High host resistance is the key to effective long-term tick control with total resistance the ultimate aim. While improvements to acaricides and vaccines are continuously pursued, improvements to the most important single factor controlling ticks, host resistance, have been neglected. Resistance is as heritable as milk yield or growth and in tropical breeds can be increased to very high levels by selection. Despite this there are no current examples of sustained selection for tick resistance. Temperate breeds have low resistance but because of high production potentials are favoured for crossbreeding with tropical breeds. This perpetuates the need for reliance on acaricides. Selection to increase polygenic resistance of temperate breeds is impractical. However, a quantum increase can be achieved by introgressing major resistance genes. Such a gene occurs in the Belmont Adaptaur and in suitable genetic backgrounds confers 100% resistance. Total resistance is achievable and provides a permanent solution to ticks.

Animals↗
PubMed1996

An assessment of host resistance to ticks on cross-bred cattle in Burundi.

Groups of cattle of four different cross-breeds (Ankole x Friesian, Ankole x Brown-Swiss, Ankole x Guernsey, Ankole x Sahiwal) plus a group of pure Ankole cattle were immunized against tick-borne diseases: East Coast Fever, using a Theileria parva trivalent vaccine, and anaplasmosis, babesiosis and, subsequently, heartwater. With the exception of two small subgroups of Ankole and Ankole x Sahiwal which were treated by weekly spraying using Delnav, all the groups were exposed to natural field challenge of ticks to quantify the development of host resistance to ticks. The results indicate resistance to the most abundant species, Rhipicephalus appendiculatus, as follows: Ankole > Ankole x Sahiwal > Ankole x Brown Swiss > Ankole x Friesian > Ankole x Guernsey. In both Amblyomma variegatum and Rhipicephalus evertsi evertsi, the manifestation of different levels of resistance between breeds is inapparent. Correlations between total ticks and standard female ticks were good for R.appendiculatus (r = 0.73) and R.evertsi (r = 0.51) but poor for A.variegatum (r = 0.31). Correlations between species were reasonably consistent (r = 0.43-0.59). There was no significant correlation between tick burdens and daily liveweight gain (DLWG) over the whole period of the study. Of the cross-bred groups, Ankole x Sahiwal, which had the highest level of resistance, had the highest DLWG. In contrast, the Ankole x Guernsey which developed the lowest level of resistance had only marginally lower DLWG, the difference being only 8 g/day. During the first period of exposure to ticks, however, the untreated Ankole x Sahiwal group had markedly lower DLWG, which may indicate that the development and manifestation of resistance is at the expense of productivity.

Animals↗
PubMed2002

Effect of the association of cattle and rusa deer (Cervus timorensis russa) on populations of cattle ticks (Boophilus microplus).

The wild population of rusa deer (Cervus timorensis russa) in New Caledonia (South Pacific) is nearly as large as the cattle population. The cattle tick is widespread and occurs all year round. Opinions are divided on the role of deer in the biological cycle of the tick: i) Do they maintain a sustainable tick population that is secondarily available for cattle? ii) Do they decrease the infestation of the environment by collecting larvae on the pasture, but preventing their development to the engorged female stage? or iii) Do they contribute to both situations? An experiment was conducted in three groups of pastures, each seeded with 450 000 larvae/ha and allowed to be grazed only by cattle, only by deer, and by a mixed herd of deer and cattle (deer representing 30% of the biomass), at approximately the same stocking rate (470-510 kg/ha). After 15 months of exposure, the tick burden per weight unit of host was 42 ticks/kg for the steers-only herd and 0.01/kg for the deer-only herd. The steers in the "mixed group" harbored 7 times fewer ticks (6.2/kg) than the cattle-only group, and the deer in the "mixed group," 130 times more (1.3/kg) than the deer-only group. Five emergency acaricide treatments had to be applied in the cattle-only group, but none in the other groups. The long-term sustainability of a viable tick population on deer as well as the potential benefit resulting from the association of deer and susceptible cattle in the tick control of cattle are highlighted.

Animals↗
PubMed1997

The application of moxidectin formulations for control of the cattle tick (Boophilus microplus) under Queensland field conditions.

OBJECTIVE: To assess the control of the cattle tick (Boophilus microplus) and the performance of commercial cattle treated with the macrocylic lactone endectocide, moxidectin, formulated either as an injection or as a pour-on. DESIGN: Groups of 10-12 tick infested cattle were treated with moxidectin injection, moxidectin pour-on or remained untreated (28-day trials) or were treated with deltamethrin-ethion as a dip (140-day trials). The cattle were exposed to natural tick challenge under field conditions. PROCEDURE: Tick numbers on trial cattle were recorded in each trial before the initial treatment and in the 28-day trials at 7, 14, 21 and 28 days or in the 140-day trials, at 28-day intervals before each of the treatments and at the final inspection. Body weights of the cattle were also recorded prior to the initial treatment and at the termination of each trial. Cattle were observed on the day of each treatment and at each inspection for evidence of any reactions to treatment. RESULTS: 28-day trials: Significant reductions in tick counts were recorded in both treatment groups when compared with cattle in the untreated group. Weight advantage was recorded in the moxidectin treated groups. 140-day trials: All three treatments resulted in zero or low tick counts at each inspection with the exception of the pour-on treatment at week 8 in one trial and week 9 in the other trial. Additional weight gain was recorded for both the moxidectin treated groups, relative to the deltamethrin-ethion dip groups, but was significant only for the pour-on groups. There was no evidence of any local or systemic adverse reaction in any treated cattle in any trial. CONCLUSION: Good to excellent control of the cattle tick (Boophilus microplus) was demonstrated with the moxidectin formulations in all trials, the injection being particularly effective. An improved performance was recorded in all trials in cattle treated with both moxidectin formulations when compared with the untreated cattle and with cattle treated with the deltamethrin-ethion dip. There was no evidence of any local or systemic adverse reaction to treatment with either moxidectin formulation.

Administration, Topical↗
PubMed1977

The clinical features of tick bite.

The clinical features of bites by the Australian scrub tick, Ixodes holocyclus, are reviewed. Eight cases of tick bite are summarized, including six new cases of tick paralysis in children. In almost all cases neuroparalysis became worse transiently, after the tick had been removed. One child with life-threatening respiratory and bulbar palsy received canine antitick antivenene, with rapid reversal of clinical signs. The differential diagnosis of tick bite includes all acute childhood diseases which can affect the motor units; the importance of including the possibility of tick envenomation in the differential diagnosis of acute weakness or paralysis in children is illustrated. The clinical features of neuromuscular paralysis are described, together with a review of the tick's local effects at the bite site.

Adult↗
PubMed1964

TICKS (IXODIDAE) ON MIGRATING BIRDS IN EGYPT, SPRING AND FALL 1962.

Over a number of years studies have been carried out in Egypt on the transport by migrating birds of ticks that may transmit pathogens of man and animals. In continuation of these investigations 11 036 birds migrating southwards through Egypt were examined for ticks during the fall of 1962. The 881 infested birds (comprising 24 species and sub-species represented by 10 612 individuals) yielded 1442 ticks. Tick-host relationships were similar to those of previous years except that in 1962 the prevalence of infestation was almost invariably much higher than the averages for 1959-61. Five species of birds were added to the previous list of 40 infested forms. Previously unrecorded tick species taken during 1962 were Ixodes redikorzevi (a species from Asia very occasionally found in rodent burrows in Egypt), the rare Haemaphysalis inermis, and Hyalomma a. anatolicum, H. anatolicum excavatum and H. dromedarii, which may have been carried from Asia or have attached themselves to the birds at the time of netting.During the spring of 1962, altogether 1774 birds migrating northwards through Egypt were also examined. The 56 tick-infested birds (comprising 13 species represented by 867 individuals) yielded 186 ticks. As in previous years, Hyalomma marginatum rufipes was the chief species (89.25%) parasitizing spring migrants. A single specimen of Amblyomma variegatum was taken on Anthus cervinus and 19 specimens of Ixodes?sp. nov. were collected from Sylvia c. communis and Motacilla a. alba.

Animals↗
PubMed1994

Epidemiological studies of Lyme borreliosis and tick-borne encephalitis.

The hard tick Ixodes ricinus, vector of Borrelia burgdorferi and TBE virus (TBEV), is most abundant in the southern and central parts of Sweden. About 2000 cases of Lyme borreliosis (LB) and 50-80 cases of tick-borne encephalitis (TBE) are estimated to occur in Sweden annually. Five populations, including 903 individuals living in five different areas close to Stockholm where LB and TBE are endemic, were studied with regard to the clinical manifestations and antibody prevalence of LB and TBE. The study areas involved four groups of islands in the Baltic Sea and one island in Lake Mälaren. A history of LB was reported by 1-21% of the participants and antibodies to Borrelia burgdorferi were found in 7-29% of the individuals from the various areas. An increasing seroprevalence with age was seen. A history of TBE was reported by 0-6% of the individuals and in non-immunised participants seropositivity was seen in 4-22%, depending on the area investigated. The individuals from one of the areas, where 30% of Ixodes ricinus ticks had been found to be infected with Borrelia spirochetes, were followed during a two-year period. In the first year of the study, 4.6% of the subjects (n = 303) developed LB and in the second year 3.2% (n = 277). A significant increase in the antibody titre for Borrelia burgdorferi was seen in 4.6% of the individuals in the first year and in 2.9% in the second year. In the first year of the study, 0.3% of the subjects developed TBE and in the second year 0.4%. Seroconversion for TBEV was found in 1.2% of the subjects in the first year and in 2.4% in the second year. In 362 orienteers from the county of Stockholm, a past history of LB was reported by 6% of the individuals and 9% of them were seropositive. A past history of TBE was reported by 0.3% of the orienteers and 1% of the individuals were seropositive. A total of 3141 Ixodes ricinus ticks, 2740 adults and 401 nymphs, were collected from different localities in 23 of the 25 provinces in Sweden. The ticks were examined for the presence of Borrelia spirochetes by indirect immunofluorescence. The prevalence of Borrelia-infected Ixodes ricinus ticks varied from 10-20% in the southern and central parts of Sweden to about 5% in the northern part (Norrland). Of 41 non-Ixodes ricinus ticks, none was positive to Borrelia.

Animals↗
PubMed2007

An in vitro feeding assay to test acaricides for control of hard ticks.

Animal husbandry could not be practised over large areas of the planet without acaricides. The prevention of tick bite and the transmission of diseases requires the use of pesticides, but this contributes to the development of tick resistance against acaricides. This drives the quest for new molecules that target physiological processes crucial to tick survival. In vivo trials involve multiple repetitions because of inherent variations between host animals, requiring large amounts of test products and ticks. An in vitro alternative should permit the testing of the ability of a product to restrict attachment and feeding by ticks at precise doses. In this paper an in vitro feeding system is described where the European tick Ixodes ricinus L. feeds on blood through a cellulose rayon-reinforced silicone membrane. The membrane Shore hardness is modified to imitate the elastic retraction forces of skin that ensure the closing of tick penetration sites on the membrane to prevent bleeding. Tick attachment (75-100%) is achieved by adding chemical and mechanical stimuli to the membrane. Survival curves for different doses of fipronil and ivermectin tested with the method showed highly reproducible acaricide effects within 5-7 days. Significant effects are recorded down to ppb levels in blood. Standardised tests can be made with blood from the same donor animal or culture medium under the membrane.

Animals↗
PubMed1996

Dynamics of Borrelia burgdorferi infection in nymphal Ixodes ricinus ticks during feeding.

We report the sequential development events of Borrelia burgdorferi in histological sections of Ixodes ricinus nymphs before, during and after feeding. During the blood meal a decrease of approximately 50% in the number of infected ticks was recorded (eight out of 76, 11%) in comparison with the infection rate of unfed ticks (12 out of 56, 21%). Spirochetes were detected in tick salivary glands only after 2 days of attachment. From day 3 until drop-off, the number of infected ticks increased to 31% (15 out of 49). A quadratic logistic regression analysis showed that the variation in the number of infected ticks was significant, but only during the blood meal. The drop in the percentage of infected ticks during the first hours following attachment to the host is explained by our observation of spirochetes in the faces of the ticks. The increase in the infection rate of replete ticks may be due to an uptake of spirochetes from the host skin at the feeding site.

Animals↗
PubMed2004

Differential expression of the msp1alpha gene of Anaplasma marginale occurs in bovine erythrocytes and tick cells.

Major surface proteins (MSP) 1a and 1b of the tick-borne pathogen Anaplasma marginale (Rickettsiales: Anaplasmataceae) are conserved on A. marginale derived from bovine erythrocytes and tick cells. MSP1a and MSP1b form the MSP1 complex and are adhesins involved in infection of host cells. While both MSP1a and MSP1b are adhesins for bovine erythrocytes, only MSP1a is an adhesin for cultured and native tick cells. These studies were initiated because antibody responses to MSP1a and MSP1b differed in cattle immunized with killed A. marginale derived from bovine erythrocytes or cultured tick cells. A strong antibody response to MSP1a was observed in cattle immunized with erythrocyte-derived A. marginale, whereas cattle immunized with tick cell culture-derived A. marginale produced antibodies preferentially to MSP1b. The molecular basis of this differential antibody response was then studied using Western blot, confocal microscopy and reverse transcriptase (RT)-PCR. Whereas expression of MSP1b by A. marginale derived from both bovine and tick host cells was similar at the protein and RNA levels, expression of MSP1a by A. marginale in these cells differed. Low levels of MSP1a were observed in cultured tick cells and tick salivary glands, but high expression of MSP1a occurred on A. marginale derived from bovine erythrocytes. The analysis of the expression of the msp1alpha gene by RT-PCR suggests that the differential expression of MSP1a is regulated at the transcriptional level and may influence the infectivity of A. marginale for host cells. Variation in the expression of MSP1a may also contribute to phenotypic and antigenic changes in the pathogen.

Anaplasma marginale↗
PubMed1999

Feeding and respiratory gas exchange in the American dog tick, Dermacentor variabilis.

This study investigated the effect of blood feeding on respiratory gas exchange in the dog tick Dermacentor variabilis. Adult male and female ticks were fed on bovine hosts from 1 to 11days. Females fed slowly for the first 6days and then rapidly engorged on blood 2-3days prior to dropping from the host. Ticks were removed at daily intervals during feeding, weighed and CO(2) emission measured at 25 degrees C using flow-through respirometry. During feeding, females (N=39) showed a 100-fold gain in mass from 5.78+/-1.05mg to 541.15+/-18.60mg while standard metabolic rate (Vdot;co(2)) increased from 0.179+/-0.030&mgr;lh(-1) in unfed ticks to 87.32+/-5.72&mgr;lh(-1) in fully engorged ticks. CO(2) release prior to feeding was highly discontinuous with discrete spiracular bursts of CO(2) emission approximately every 30min. For CO(2) emission measured in detached partially or completely fed ticks, burst frequency became more and more rapid as feeding progressed and changed to continuous sustained CO(2) output during rapid engorgement. In contrast to females, male ticks (N=20) showed little change in mass and maintained discontinuous CO(2) throughout the 11day attachment period on the host. The switch from discontinuous to continuous CO(2) release and presumed increase in respiratory water loss in female ticks is correlated to an increase in metabolic expenditure associated with blood meal digestion rather than any factor relating directly to maintenance of water balance.

Journal Article↗
PubMedDate not supplied

[Knowledge and prevention of tick-bite borreliosis: survey of the population in Alsace, an endemic area].

INTRODUCTION: European borreliosis, known to the general public as 'Lyme disease' in analogy with the American form, which it differs from in many points, is endemic in the area of Alsace and is a public health problem. The level of knowledge and prevention of the population with regard to the disease has never been assessed in France. MATERIAL AND METHODS: A survey was conducted in all the national health examination centers in Alsace using a self-applied questionnaire. The data collected concerned the socio-demographical characteristics, knowledge on the disease, history of tick bites, fear the disease creates, frequency of visits to the forest, prevention habits when visiting the forest and the attitude adopted in the case of a tick bite. RESULTS: Out of the 600 persons included, 99 (16.5 p.cent) had been bitten by ticks once or more over the past year. The existence of Lyme's disease was known to 74 p.cent of the consultants, 63 p.cent claimed they were worried by the disease and 43 p.cent knew that the first manifestation is redness spreading over the skin. Twenty-seven percent wore trousers and long sleeves when visiting the forest and 19 p.cent inspected their body carefully on their return. The persons least well informed were also those who did little to protect themselves against tick bites. They often were under 30 years old, lived in urban settings and had few diplomas. Those who had frequent spare time in forest and those who had a history of tick bites were the best informed and protected themselves better. The fear of the disease was associated with better knowledge and more appropriate behaviour. DISCUSSION: This study shows that a large percent of the population in Alsace is exposed to tick bites. Tick bite borreliosis is relatively well known, but protection remains insufficient. Better knowledge of the disease is related to better prevention. Information and teaching campaigns for the general public could specifically target the young people, urban dwellers and those with few diplomas. Specific messages of prevention could be delivered to the most exposed at-risk subjects (i.e. those bitten by ticks or having leisure in forest) at the places of their leisure or medical consultations.

Adult↗
PubMed1997

Tick-host immunology: Significant advances and challenging opportunities.

Immunological interactions at the tick-host interface involve innate and acquired host defenses against infestation and immunomodulatory countermeasures by the tick. The cellular and molecular immunological bases of these host-parasite relationships are being defined. Acquired resistance to tick infestation involves humoral and cellular immunoregulatory and effector pathways. Ticks respond by suppressing antibody production, complement, and cytokine elaboration by both antigen-presenting cells and specific T-cell subsets. Tick-borne disease-causing agents probably exploit tick suppression of host defenses during transmission and initiation of infection. Because of the public health importance of ticks and Pick-borne diseases, it is crucial that we understand these interactions and exploit them in novel immunological control strategies. Here, Stephen Wikel and Douglas Bergman discuss recent advances in understanding tick-host immunology and propose future studies.

Journal Article↗
PubMed2005

Manipulation of host cytokine network by ticks: a potential gateway for pathogen transmission.

Ticks are obligatory blood-feeding arthropods that secrete various immunomodulatory molecules to antagonize host inflammatory and immune responses. Cytokines play an important role in regulating these responses. We investigated the extent to which ticks interact with the sophisticated cytokine network by comparing the effect of salivary gland extracts (SGE) of 3 ixodid tick species, Dermacentor reticulatus, Amblyomma variegatum and Ixodes ricinus, all of which are important vectors of tick-borne pathogens. Using specific ELISAs, anti-cytokine activity was demonstrated with 7 cytokines: IL-8, MCP-1, MIP-1alpha, RANTES, eotaxin, IL-2 and IL-4. The results varied between species, and between adult males and females of the same species. Relatively high activity levels were detected in saliva of female D. reticulatus, confirming that the observed anti-cytokine activities are an integral part of tick saliva secreted into the host. Results with fractionated SGE indicated that from 2 to 6 putative cytokine binding molecules are produced, depending on species and sex. Binding ability of SGE molecules was verified by cross-linking with radio-isotope labelled MIP-1alpha. By targeting different cytokines, ixodid ticks can manipulate the cytokine network, which will greatly facilitate blood-feeding and provide a gateway for tick-borne pathogens that helps explain why ticks are such efficient and effective disease vectors.

Animals↗
PubMed2006

Vector seasonality, host infection dynamics and fitness of pathogens transmitted by the tick Ixodes scapularis.

Fitness of tick-borne pathogens may be determined by the degree to which their infection dynamics in vertebrate hosts permits transmission cycles if infective and uninfected tick stages are active at different times of the year. To investigate this hypothesis we developed a simulation model that integrates the transmission pattern imposed by seasonally asynchronous nymphal and larval Ixodes scapularis ticks in northeastern North America, with a model of infection in white-footed mice (Peromyscus leucopus) reservoir hosts, using the bacteria Borrelia burgdorferi and Anaplasma phagocytophilum as examples. In simulations, survival of microparasites, their sensitivity to reduced rodent and tick abundance, and to 'dilution' by a reservoir-incompetent host depended on traits that allowed (i) highly efficient transmission from acutely-infected hosts, (ii) long-lived acute or 'carrier' host infections, and/or (iii) transmission amongst co-feeding ticks. Minimum values for transmission efficiency to ticks, and duration of host infectivity, necessary for microparasite persistence, were always higher when nymphal and larval ticks were seasonally asynchronous than when these instars were synchronous. Thus, traits influencing duration of host infectivity, transmission efficiency to ticks and co-feeding transmission are likely to be dominant determinants of fitness in I. scapularis-borne microparasites in northeastern North America due to abiotic forcings influencing I. scapularis seasonality.

Anaplasma phagocytophilum↗
PubMed1998

Transmission risk of Borrelia burgdorferi sensu lato from Ixodes ricinus ticks to humans in southwest Germany.

The risk of Borrelia burgdorferi infection and the value of antibiotic prophylaxis after tick bite are controversial. In this study, performed in two areas of southwestern Germany, ticks were collected from 730 patients and examined by the polymerase chain reaction (PCR) for B. burgdorferi. To assess whether transmission of B. burgdorferi occurred, the patients were clinically and serologically examined after tick removal and during follow-up examinations. Data from all tick bites gave a total transmission rate of 2.6% (19 patients). Eighty-four ticks (11.3%) were PCR positive. Transmission occurred to 16 (26.7%) of 60 patients who were initially seronegative and could be followed up after the bite of an infected tick. These results indicate that the transmission rate from infected ticks in Europe is higher than previously assumed. Examination of ticks and antibiotic prophylaxis in the case of positivity appears to be indicated.

Adolescent↗
PubMed1998

Optimal sampling and spatial distribution of Ixodes pacificus, Dermacentor occidentalis and Dermacentor variabilis ticks (Acari: Ixodidae).

A common method for sampling tick populations is flagging, which is a method of dragging a white cloth over a plant substrate for a fixed distance along a transect. Flagging over rough physical surfaces or using long subtransect lengths could lead to the underestimation of tick densities. Using estimates of the drop-off rates of adult Ixodes pacificus in flag sampling, optimal sampling schemes (the length and number of subtransects) were examined using the relationships between the tick drop-off rates (c), the tick density and distribution patterns and the roughness of the sampled plant substrate. It was found that the optimal number of subtransects and Lmax, the longest subtransect length which did not significantly underestimate the tick density from c, were affected by the tick density, substrate roughness and tick distribution pattern. This study also showed that the density and distribution of I. pacificus and Dermacentor occidentalis varied greatly over time in the populations sampled, while the Dermacentor variabilis densities were low and showed no significant changes over time. Both I. pacificus and D. occidentalis had clumped distributions along trails and these clumps were aggregated. However, the clump sizes (or individual clump areas) changed significantly over time because of density fluctuation or the movement of ticks. Finally, a positive association between the number of I. pacificus and D. occidentalis adults was observed from 2 m subtransect flag collections in March 1995; no relationship was found in 1994.

Animals↗