SEARCH · Search PubMed

Results for “TICKS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources

PubMed1975

Development of Theileria mutants (Aitong) in the tick Amblyomma variegatum compared to that of T. parva (Muguga) in Rhipicephalus appendiculatus.

A comparison was made between the development of Theileria mutans (Aitong) in adult Amblyomma variegatum ticks and the development of T. parva (Muguga) in adult Rhipicephalus appendiculatus ticks. Both batches of ticks dropped as engorged nymphs from cattle whose intraerythrocytic parasitemias were approximately 40%, and it was thus possible to make a direct comparison of the infection rates produced in their tick hosts in this experiment by the 2 species of Theileria. Ticks of the 2 batches were fed in ear bags on rabbits, and equal numbers of male and female ticks were removed daily for 5 days. The salivary glands were dissected out from these ticks, and from unfed ones in each batch, processed, and examined for Theileria parasites, which were categorized according to their morphological maturity. The A. variegatum ticks had a lower rate of infection with Theileria. Fewer parasites were observed in the ticks, and they took longer to mature. When the development of the 2 species of Theileria was compared, the major difference appeared to be that T. mutans had large Babesia-like infective particles.

Animals↗

PubMedDate not supplied

[The significance of the species classification of ixodid ticks and their hosts in the development of antitick immunity].

Larvae of Ixodes persulcatus and Hyalomma asiaticum were feeding permanently on hosts attacking them daily by groups of 5-20 ticks, and also fed by groups of 30-40 and 100 ticks with the interval 20 days. The factor of the host species in the case of 1-st feeding of ticks did not influence significantly on the weight of engorged ticks and also on the percent of larvae, which had finished the feeding and moulted to nymphs. In the cases of 2-nd and 3-rd feedings the significant part of ticks died before the end of feeding, and engorged ticks had less weight and lower capability to moult. The rate of anti-tick resistance of hosts depends upon the species of the host and upon the number of ticks fed up. In the case of permanent feeding of larvae during 40 days the anti-tick resistance was low or completely absent.

Animals↗

PubMed1997

Identification and characterization of anticoagulant activities in the saliva of the lone star tick, Amblyomma americanum (L.).

Anticoagulant activities against both the extrinsic and intrinsic coagulation pathways were identified in the saliva of partially fed female lone star ticks, Amblyomma americanum (L.). The activities of factor Xa and thrombin in the common pathway of the coagulation cascade were inhibited by tick saliva. The greatest anticoagulant activities were found in the saliva of ticks weighing more than 200 mg. The anticoagulant activities in tick saliva could be detected without preincubation of tick saliva with sheep plasma, but preincubation significantly increased the activities. Tick saliva anticoagulant activities were abolished by boiling for 15 min or being treated with trypsin for 1 hr. Phosphatidylcholine (3 mM) and phospholipase A2 inhibitor oleyloxyethyl phosphorylcholine (0.2 mM) did not affect the anticoagulant activities significantly, suggesting that the phospholipase A2 activity found in tick saliva does not contribute to the anticoagulant activities. Size exclusion high performance liquid chromatography revealed that the molecular weights of the anticoagulant activities were approximately 16,000 D. The anticoagulant activities in tick saliva are believed to play an important role in facilitating tick feeding by helping overcome the host hemostatic system.

Animals↗

PubMed1995

An evaluation of strategic and threshold control measures against the Karoo paralysis tick, Ixodes rubicundus (Acari: Ixodidae) in South Africa.

Paralysis caused by feeding female Ixodes rubicundus ticks is a major problem in large areas of South Africa. As the life cycle of the tick extends over a period of 2 years, it was hypothesized that strategic treatment of sheep with an acaricide over a 2 year period, timed to kill most engorging females, should markedly lower the biotic potential of the tick. Two flocks of sheep grazing in separate paddocks known to be infested with I. rubicundus were treated either strategically or on a threshold basis (i.e. only when tick challenge exceeded a predetermined critical level in terms of paralysis) for a 2 year period. The tick burdens of untreated control sheep running with the two flocks were monitored over a 4 year period and their seasonal dynamics determined. The times at which peak infestations occurred were similar for both flocks of sheep, but significant differences in mean tick burdens between the two flocks were recorded. Tick numbers on sheep in the strategically treated flock did not decrease during the third and fourth years of the trial as was expected. Possible reasons for this were low stocking densities, especially during times of peak abundance of adults and the presence of wild hosts which maintained tick populations.

Animals↗

PubMed1991

Studies on the economics of ticks in Zambia.

Two herds of experimental Sanga cattle were maintained under traditional savanna grazing management for three years in the Central Province of Zambia. One herd was kept free of ticks by regular acaricide treatment, while the other was given no tick control. Milk production, growth rate, fertility and mortality were monitored throughout the trial. The tick-free herd performed significantly better than the tick-infested herd, but the value of the additional production was much less than the cost of the acaricide used. It is concluded that there is no economic justification for intensive tick control under these conditions. However, strategic tick control would be justified if the quantity of acaricide used could be reduced by 50% without any major reduction in benefits. The results indicate that treating calves below 45 days of age reduces their performance, as does treating cows during periods of very low tick challenge. Therefore, it seems likely that economically beneficial strategic tick control policies could be developed.

Animals↗

PubMed2006

Etiology of tick-borne febrile illnesses in adult residents of North-Eastern Poland: report from a prospective clinical study.

Febrile tick-borne diseases can be caused by different pathogens. The study objective was to prospectively determine the etiology of infection among adults exposed to tick bite and to detect acute human granulocytic anaplasmosis (HGA), a recently emerging infection, in north-eastern Poland. We evaluated 68 patients (34 males and 34 females, mean age 44.2+/-15 years) who had fever within 4 weeks after a tick bite. Paired sera were tested for antibodies against tick-borne encephalitis virus, Borrelia burgdorferi and Anaplasma phagocytophilum. Microscopic examination of EDTA whole blood and nested PCR targeting A. phagocytophilum 16S rDNA gene fragment were carried out at enrolment. Tick-borne infections were diagnosed in 57 individuals (84%). Sixty-four patients were hospitalised. Tick-borne encephalitis (TBE) was revealed in 49 cases; in 39 patients as a single infection, in three patients concurrent with erythema migrans or other Lyme borreliosis symptoms, in five patients concurrent with probable or possible Lyme borreliosis, and in two patients concurrent with A. phagocytophilum infection. Diagnosis of HGA was confirmed in one patient by PCR and in another one by seroconversion. In two further individuals, A. phagocytophilum infection was confirmed by immunofluorescence (antibody titers > or = 1:128), which, however, does not fulfil the ESCAR (European Society of Clinical Microbiology and Infectious Diseases Study Group on Coxiella, Anaplasma, Rickettsia, and Bartonella) criteria for HGA case definition. Lyme borreliosis was diagnosed in 16 patients; in six of them as a single infection. Both confirmed HGA cases and seropositive individuals had A. phagocytophilum infection concurrent either with Lyme borreliosis (two cases) or with TBE (two cases). The clinical course was severe in three and moderate to mild in the remaining TBE cases, as well as in all Lyme borreliosis and HGA cases. TBE was found the most prevalent disease among adults with febrile illnesses occurring after a tick bite in north-eastern Poland. Concurrent tick-borne infections were frequent with multiple pathogens involved. Two confirmed acute HGA cases (fulfilling the European case definition criteria defined by ESCAR) were detected for the first time in a prospective manner in Poland.

Adolescent↗

PubMed1999

Tick modulation of host immunity: an important factor in pathogen transmission.

Immunological interactions at the tick host interface involve innate and specific acquired host immune defenses and immunomodulatory countermeasures by the tick. Tick feeding stimulates host immune response pathways involving antigen-presenting cells, cytokines, B-cells, T-cells, circulating and homocytotropic antibodies, granulocytes, and an array of biologically active molecules. In response to host immune defenses, tick-mediated host immunosuppressive countermeasures inhibit: host antibody responses; complement activation; T-cell proliferation; and cytokine elaboration by macrophages and Th1-lymphocytes. Immunosuppressive proteins identified in tick salivary glands and saliva have been partially characterised. Tick-induced host immunosuppression facilitates blood meal acquisition and is an important factor in the transmission/establishment of the tick-borne disease-causing agent, Borrelia burgdorferi. A novel strategy for control of tick-borne pathogens is proposed.

Animals↗

PubMed2003

Factors related to cattle infestation level and resistance to acaricides in Boophilus microplus tick populations in New Caledonia.

Boophilus microplus, even in the absence of babesiosis, is a major disease of the cattle in New Caledonia where the particular farming system associates continental European breeds and a tropical climate tempered by the Pacific Ocean. In order to have a better understanding of the factors involved in cattle tick infestation, to decrease the possible wastage and use of chemicals and to increase the lifetime of the acaricides, the veterinary authorities investigated the conditions of the chemical treatments. A survey among 148 cattle farms of the whole of New Caledonia was carried out and factors that explain the development of tick resistance and cattle infestation have been determined. From this survey, three typologies for the main characteristics of the farms have been set up, the technical practices of the farmers and the tick control measures applied by the farmers, respectively. Some variables are significantly associated with the tick resistance to deltamethrin but their contribution to the explanation model is always moderate: farms in the south, with a positive resistance gradient from east to west, absence of bush fire and membership to a cattle farmers organization. The more the farmers have intensified their breeding-male castration, weaning, heifer separation, drenching, etc.-and pasture-high stock rate, mowing, extra feeding of the cows, many paddocks, etc.-techniques, the higher was the probability for the ticks in their farm to be resistant to deltamethrin. The technical details of the acaricide treatment had a low contribution to the explanation model. However, the use of a spray generated more resistance than a dip. Furthermore, there is a negative resistance gradient when the farmers increased the treatment interval average. Considering infestation, none of the variables from the three typologies were associated with the two infestation variables (1: semi-engorged tick females and 2: other ticks) at the herd level. However, the seven studied variables-the three typologies, breed, age, body condition score and breeding status-affected significantly the two infestation variables at the cow level, but their predictive ability remained very low (R(2)<3.5%). This result-individual effect more important than herd effect on the infestation-is confirmed by the importance of the variance of the intra-farm factors (99%) when compared with inter-farm factors (1%). Cows of Charolais breed, in poor body condition, old, pregnant or lactating, and those of the farms with irrational and high pressure control of ticks are the most infested.

Agriculture↗

PubMed1998

Natural prevalence of infection with Ehrlichia (Cytoecetes) phagocytophila of Ixodes ricinus ticks in Scotland.

Ixodes ricinus nymphs and adults were collected from vegetation and from sheep at four sites in Scotland typical of areas endemic for tick-borne fever in sheep caused by infection with Ehrlichia (Cytoecetes) phagocytophila (Rickettsiales). The great majority of ticks examined was from woodland sites adjacent to sheep farms where there was a high probability of them feeding on roe deer (Capreolus capreolus) in a non-domestic focus of infestation and infection. Ticks were examined for infection by five methods. Batches of ticks were examined either by feeding on susceptible sheep or by feeding on rabbits and then prepared as stabilate which was inoculated into susceptible sheep. The sheep were monitored for clinical signs of tick borne fever. Batches of ticks were examined by polymerase chain reaction for Ehrlichia phagocytophila. Salivary glands were dissected out and stained by the Feulgen method to detect Ehrlichia masses, and were examined by indirect fluorescent antibody test. Each of the methods detected infection in ticks and the prevalence of infection in nymphs with the various methods ranged from >0.25% to 2.0%. Small samples of adults examined by Feulgen staining of salivary glands indicated infection prevalences of 2.1% in males and 1.6% in females. It is considered that these low infection prevalences may be typical of natural foci of infection where deer could be a major host of ticks and E. phagocytophila.

Animals↗

PubMed1998

Attitudes and practices of Queensland dairy farmers to the control of the cattle tick, Boophilus microplus.

OBJECTIVE: To determine practices for the control of cattle ticks on dairy farms in Queensland, the attitudes of farmers to tick infestations and to identify opportunities for and barriers against the introduction of non-chemical methods of tick control. DESIGN: A survey of 199 dairy farmers from tick-infested parts of Queensland was undertaken by 20 dairy advisers and stock inspectors from October 1996 to June 1997. The sample was a proportional, random selection of dairy farms from four regions. A personal interview was conducted with each farmer and answers to 134 questions were obtained. RESULTS AND CONCLUSIONS: Most farmers were not concerned by cattle ticks on their own farms, although they believed that ticks are important to the dairy industry. They were most concerned about the development of chemical resistance by cattle ticks. Inadequate facilities and lack of motivation appeared to be the factors most limiting to improving the methods of control. Most farmers claimed to have only small numbers of ticks at worst. Although a control program recommended by the Queensland Dairyfarmers' Organisation was well regarded by farmers, few had adopted it. Many farmers saw no need to implement a strategic control program.

Animal Husbandry↗

PubMed1994

Ticks and control methods.

Ticks are the most important ectoparasites of livestock in tropical and sub-tropical areas, and are responsible for severe economic losses both through the direct effects of blood sucking and indirectly as vectors of pathogens and toxins. Feeding by large numbers of ticks causes reduction in live weight gain and anaemia among domestic animals, while tick bites also reduce the quality of hides. However, the major losses caused by ticks are due to the ability to transmit protozoan, rickettsial and viral diseases of livestock, which are of great economic importance world-wide. The authors review general aspects of tick biology, the taxonomy, pathogenic effects and vector role of these species, and methods for the control of ticks. The distribution of ticks is continuously changing, as illustrated by the spread of the African tick Amblyomma variegatum in the Caribbean, where a large-scale eradication campaign is now under way.

Animals↗

PubMed2006

Assessment of the efficacy of parasiticides for the control of tick infection in dogs under field conditions: what's new?

For their biological and ecological characteristics, ticks are vectors of the widest variety of pathogens causing tick-borne diseases (TBDs). Little information is available about the ways in which time spent by ticks to feed on hosts, transmission times and TBD prevention are related and it is exclusively limited to laboratory reports on adult stages. In particular, the time required by immature stages to transmit pathogens has not been determined for most TBDs. Considering their importance for animal and human health, effective control of immature ticks is advisable to reduce the damage ticks cause. Recently, the efficacy of a combination of imidacloprid 10%/permethrin 50% was compared with that of fipronil 10%/S-methoprene 9% against ticks when administered to naturally infected dogs. A semi-quantitative method was used to assess the methodological parameters to calculate drug efficacy on immature stages. On adult ticks, the efficacy of both products was high and overall very similar, whereas for the immature stages the combination of imidacloprid 10% and permethrin 50% had a higher efficacy than fipronil 10% and methoprene 9% throughout the observation period (statistically significant difference on day + 28 only). The semi-quantitative method proposed for the evaluation of immature stages can be considered a useful tool for calculating the efficacy of a drug in the field. Due the important role of immatures in the spread of TBDs, the immature tick load should be calculated to assess the efficacy of acaricidal products both under laboratory and field conditions.

Animals↗

PubMed1996

The efficacy of amitraz against cattle ticks in Tanzania.

The efficacy of amitraz on cattle ticks was assessed by susceptibility tests, spraying and dipping trials. Tests on the susceptibility of three tick species, Rhipicephalus appendiculatus, Amblyomma variegatum and Boophilus decoloratus to amitraz (technical grade-purity 98.6% w/w) showed all 15 tick strains tested to be highly susceptible, with LC50 ranging between 0.001% and 0.03%, and LC99, between 0.01% and 0.07%. Spraying trials were carried out on calves infested with R. appendiculatus, A. variegatum and B. decoloratus. Amitraz wettable powder [as Taktic total replacement (TR)] was tested against B. decoloratus, and amitraz emulsifiable concentrate (as Taktic EC) against the other two species. Both formulations showed instant action, with ticks detaching from the calves between 30 min and 8 h after spraying. More than 50% of the detached engorged females failed to lay eggs. The remainder laid few eggs, and these had a low hatching rate of 0-2%, compared with 90-98% in the controls. The detached nymphs failed to moult, and the males and non-engorged females also detached, were immobilized and finally died. In the dipping trials, cattle heavily infested with ticks (mean tick counts of about 800) were dipped once weekly in amitraz (Taktic TR). Weekly tick counts showed that the reinfestation rate was reduced to zero after the ninth dipping. The results of the three trials complement each other, showing that amitraz is at present effective in the control of African tick species on cattle in Tanzania.

Animals↗

PubMed2003

Antibodies to Anaplasma marginale major surface proteins 1a and 1b inhibit infectivity for cultured tick cells.

Major surface protein 1 (MSP1) of the cattle pathogen Anaplasma marginale (Rickettsiales: Anaplasmataceae) is a complex of two proteins, MSP1a and MSP1b. Previous studies demonstrated that MSP1a and MSP1b are adhesins for bovine erythrocytes, while only MSP1a proved to be an adhesin for tick cells. In this study, a tick cell culture system for propagation of A. marginale was used to develop an infection inhibition assay for testing the ability of antisera to block infection of A. marginale for cultured tick cells. A. marginale derived from cell culture was incubated with various antisera prior to inoculation onto cell monolayers. The monolayers were harvested 7 days post-inoculation and A. marginale in the cultures was quantified using an antigen detection ELISA. Antisera tested in the infection inhibition assay were derived from persistently infected cattle, from cattle immunized with A. marginale purified from bovine erythrocytes, and from rabbits and cattle that were immunized with the recombinant MSP1a, MSP1b and MSP1 complex. Antibodies from cattle persistently infected with A. marginale, cattle immunized with A. marginale from bovine erythrocytes or cattle immunized with the recombinant MSP1 complex did not inhibit the infectivity of A. marginale for tick cells. Antiserum from rabbits immunized with MSP1a and MSP1b (individually or combined) reduced infection of both the Virginia and Oklahoma isolates of A. marginale for tick cells by 25-70%. Likewise, antisera from cattle immunized with recombinant MSP1a or MSP1b inhibited infection of tick cells by 26-37%. These results further confirm the role of MSP1 complex proteins in infection of tick cells. Lack of inhibition of infection by antisera from naturally infected cattle or cattle immunized with whole organisms suggests that the bovine immune response is not directed toward blocking infection of A. marginale for tick cells and may contribute to the continued infectivity of the pathogen for ticks.

Anaplasma↗

PubMed1998

Risk of infection with Borrelia burgdorferi sensu lato for a host in relation to the duration of nymphal Ixodes ricinus feeding and the method of tick removal.

The objectives of the present study were to investigate the risk of B. burgdorferi s.1. (Bb)-transmission by I. ricinus-nymphs to a host (i) after different periods of feeding, and (ii) with regard to the particular method of tick removal. On each of 72 Mongolian gerbils 3 tick nymphs taken from a highly infected batch were allowed to feed in a small capsule. Feeding ticks were removed 16.7, 28.9, 47.0, and 65.2 hrs post-attachment. In each of these 4 groups 3 sub-groups with 6 gerbils each were deticked by (a) pulling ticks out with forceps without any pretreatment, (b) pulling ticks out after 3 min of intensive squeezing, and (c) applying nail polish to ticks 1.1 hrs before removal. The infection status in each gerbil was subsequently determined by larval xenodiagnosis. All gerbils with ticks removed > or = 47 hrs post-attachment were found to be infected. After 16.7 hrs as well as after 28.9 hrs of tick feeding, approximately 50% of the gerbils had acquired a transmissible infection, thus Bb-transmission to a host may even occur in the early phases of I. ricinus feeding. There is no evidence from this study that the tick removal method used has any significant influence on a host's Bb-infection risk.

Animals↗

PubMed2003

The American dog tick, Dermacentor variabilis, encodes a functional histamine release factor homolog.

We have identified a functional Dermacentor variabilis histamine release factor (DVHRF) homolog and shown that it is a secreted tick saliva protein. The 945 base pair (bp) full-length DVHRF cDNA has a 522 bp open reading frame that encodes a 20 kDa (173 amino acid) polypeptide. Sequence analysis showed that the two HRF signature amino acid sequences were conserved in DVHRF, indicating close structural similarity between DVHRF and other characterized HRF homologs. Northern and Western blotting analyses of partially fed and unfed ticks indicates that neither DVHRF transcriptional nor translational regulation were influenced by tick feeding activity. Like its counterparts from the mammalian system, tick DVHRF is expressed in various tissues, as assessed by both Northern and Western blotting analyses. Furthermore, an Escherichia coli-expressed recombinant DVHRF induced histamine secretion from a rat basophilic leukemic cell line in a dose-dependent manner. Extensive experimental evidence has shown that high levels of histamine at tick attachment sites impede the biological success of feeding ticks and, in response, ticks secrete histamine-binding proteins to minimize the adverse effects of histamine. Our results suggest the existence of a tick-derived multifaceted control mechanism for levels of histamine at tick feeding sites.

Amino Acid Sequence↗

PubMed2004

Lyme borreliosis spirochetes in questing ticks from mainland Portugal.

In Portugal, Ixodes ricinus ticks have been shown to contain DNA of several spirochetes belonging to the Borrelia burgdorferi sensu lato complex, with major differences in the genetic diversity between ecozones. Some isolates have been obtained since 1999, confirming the circulation of pathogenic strains in these ticks. Ixodes ricinus is considered to be a widespread species, however, in Portugal it is found only in a few habitats. Here we present preliminary results from a nationwide survey of questing I. ricinus (n = 4,001) and other Ixodidae (n = 1,534) in Portugal, initiated in 2001. The sampling points (so far 41) were selected using a Geographic Information System, according to the type of vegetation, accessibility and prevalence of human cases. The spatial and temporal of tick abundance and the infection of B. burgdorferi sensu lato in ticks were determined in selected areas. Ticks were examined for the presence of B. burgdorferi sensu lato by culturing (719 out of 4,001 I. ricinus), and direct PCR amplification of the 5S-23S intergenic spacer region (1,870 out of 5,535) followed by RFLP analysis, the reverse line blot assay and nucleotide sequencing of PCR amplicons. The most abundant tick genus was Rhipicephalus (53%), followed by Dermacentor (34%), I. ricinus and Hyalomma (7%, each). The Mafra and Grândola sites, where a more intensive study was carried out, were excellent habitats for I. ricinus. However, a clear difference of the prevalence of Borrelia infection and the genetic diversity of circulating spirochetes was observed in these two sites. Genotyping of all I. ricinus isolates revealed 5 B. garinii, 8 B. lusitaniae and 1 B. valaisiana strains, which were obtained for the first time in these regions along with a considerable percentage of tick-derived PCR amplicons. Two hard-tick species other than I. ricinus in Grândola were also B. lusitaniae positive, thus seeming to take part in the transmission cycle of Borrelia. The seasonal dynamics of I. ricinus in Mafra was bimodal, more pronounced in nymphs than in adults. The present findings indicate that B. burgdorferi sensu lato agents are differentially maintained in nature in local tick populations in different geographic areas across Portugal and that the risk of acquiring Lyme borreliosis in certain areas of Portugal is higher than previously assumed.

Animals↗

PubMed2001

Studies on the critical water mass and the rehydration potential of unfed adult Dermacentor marginatus and D. reticulatus ticks (Acari: Ixodidae).

In unfed adult Dermacentor marginatus and D. reticulatus ticks survival and capability to restore water balance after loss of high percentages of exchangeable body water were investigated. Furthermore, it was examined how frequently dehydrated ticks of these species were able to rehydrate by uptake of atmospheric water vapour. The critical water mass, defined as the water mass remaining in a tick at the nonambulatory state, differed between light and heavy weight groups and averaged 62.4 and 55.8%, respectively, of the total body water of fully hydrated ticks in females, and 54.4 and 51.1%, respectively, in males of D. marginatus. In D. reticulatus, the corresponding figures were 55.9 and 54.7% in females and 52.1 and 52.7% in males. All ticks survived dehydration to 50, 75 or 100% of the critical water mass, and 96.7% of the D. marginatus ticks and 95.8% of the D. reticulatus ticks compensated water losses during subsequent incubation at 95% relative humidity (r.h.) and 20 degrees C. Unfed females and males of both Dermacentor spp. were capable to balance water loss very frequently over a period of several months. When ticks were repeatedly dehydrated at 0% r.h. for 7 days and rehydrated at 95% r.h. and 20 degrees C, females and males of D. marginatus reached the 50% mortality after 22 and 29 cycles of de- and rehydration, respectively, during 211 and 285 days, respectively. In D. reticulatus, 50% of females and males survived 23 and 17 cycles, respectively, during 248 and 186 days, respectively. Rehydration weights were as high or even higher as those of ticks kept at permanent 95% r.h.

Animals↗