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PubMed1983

Babesia bovis: computer simulation of the relationship between the tick vector, parasite, and bovine host.

Components contributing to the survival of Babesia bovis in its tick vector (Boophilus microplus) and bovine host were identified and their relationship simulated with an interactive BASIC computer program. Estimates for major independent variables (host-finding success, feeding success, filial infection rate, recovery rate) were derived from published laboratory and field data. Values for dependent variables (tick burden, inoculation rate, tick and bovine infection rates) were calculated during successive tick generations until equilibrium conditions were reached. The simulation was used to predict the effects of alternate disease control strategies. Babesiosis outbreaks were associated with simulated daily infestations of approximately two to eight engorged ticks. Below this range, B. bovis parasites disappeared, while above it all cattle were infected during the period of calfhood resistance (through 9 months of age). The babesial inoculation rate was most unstable over the above range due to instability in tick populations and tick infection rates. The risk of babesiosis outbreaks among older, less resistant cattle was also greatest over this range. The optimum daily infestation was eight to nine engorged ticks. This level would maintain herd immunity to babesiosis without causing significant physiologic stress to the bovine host. The difficulty in maintaining ecological and immunological stability at low infestation rates discourages "strategic dipping" as a means of maintaining herd immunity to babesiosis. Introduction of tick-resistant cattle provided a more effective means of reducing the risk of babesiosis outbreaks. The economic implications of computer-simulated babesiosis control alternatives should be analyzed. The validity of simulation parameters should be confirmed by field studies on the relationship between tick burdens and the babesial inoculation rate. These studies would be greatly facilitated by development of an assay system for the detection of babesiae in field-collected ticks.

Aging↗
PubMed1995

[Natural epidemiology of Lyme borreliosis with reference to clustered incidence of illnesses in the suburbs of a North Baden community].

Human infection with Borrelia burgdorferi, the causative agent of Lyme disease, is unusually common in the "Scheelkopf" area of the town Bruchsal in north Baden (Germany), a situation which has led to considerable publicity and public concern. This study was carried out in order to clarify this situation by determining the prevalence of B. burgdorferi in both the free-living tick populations (Ixodes ricinus) and the rodent population from the "Scheelkopf" as well as from surrounding control areas. The polymerase chain reaction (PCR) was used to determine the presence of infection in whole tick preparations and in mouse bladders. The prevalence of B. burgdorferi in freeland ticks ranged from 19% to 44% and in mice from 6% to 29% depending on the area studied. The "Scheelkopf", with prevalences for ticks and mice of 33% and 10% respectively, was not significantly different from the control areas. Our results indicate that there is a high risk of human infection throughout the study area. This is probably related to the intensive use of the area for gardens and the related recreational behaviour of the human population in conjunction with the high rate of infection prevailing in I. ricinus.

Animals↗
PubMed1993

Removal of attached nymphs and adults of Ixodes ricinus (Acari: Ixodidae).

Chemical and mechanical methods of removing Ixodes ricinus (L.) attached to the skin of pigs and sheep were tested experimentally. Three frequently advocated chemical treatments (gasoline, fingernail polish, and methylated spirit) failed to induce self-detachment of the ticks within 30 min. Also, the success of the subsequent mechanical removal was not influenced by chemical treatment. Two methods of mechanical removal of the ticks also were compared: (1) pulling straight out with a blunt forceps and (2) rotation of the tick around its body axis, using a "Tick Solution" forceps (Instruments of Sweden, Stamford, CT). Pulling frequently resulted in the complete removal of the tick, but fragments of the mouthparts that remained in the skin were often quite large. In contrast, if the tick was removed by rotation without pulling, the tip of the hypostome usually broke off and remained in the skin, but this portion was generally quite small.

Animals↗
PubMed1996

Efficacy of antibiotic prophylaxis for prevention of Lyme disease.

OBJECTIVE: To determine if antibiotic prophylaxis following a dear tick bite is effective in reducing the risk of developing Lyme disease. DESIGN: Meta-analysis of published trials. DATA IDENTIFICATION: Clinical trials were identified by a computerised literature search of MEDLINE and by an assessment of the bibliographies of published studies. STUDY SELECTION: Trials were included in the analysis if their patients were randomly allocated to a treatment or control group, enrolled within 72 hours following an Ixodes tick bite, and had no clinical evidence of Lyme disease at enrollment. Three trials were selected for review after inclusion criteria were applied. DATA EXTRACTION: Data were extracted for details of study design, patient characteristics, interventions, duration of therapy, and number of adverse events in each arm of therapy. RESULTS OF DATA SYNTHESIS: Among the 600 patients with Ixodes tick bites, the rate of infection in the placebo group was 1.4%. In contrast, patients who received antibiotic prophylaxis had a 0% infection rate. The pooled odds ratio, comparing prophylaxis to placebo, was 0.0 (95% confidence interval 0.0, 1.5) (p = .12). CONCLUSIONS: The available evidence to date suggests that the routine use of antibiotic prophylaxis for the prevention of Lyme disease remains uncertain. Meta-analysis of the controlled trials failed to establish definitive treatment efficacy owing to the small sample size of the combined trials and the low rates of infection following a deer tick bite. A larger randomized trial is needed to demonstrate definitively that prophylaxis is more effective than placebo in reducing the risk of early Lyme disease in endemic areas.

Amoxicillin↗
PubMed1995

Live vaccines against hemoparasitic diseases in livestock.

Live vaccines against hemoparasitic diseases in livestock are based on parasites derived from culture (Theileria annulata), from blood of infected animals (Babesia bovis, Babesia bigemina, Anaplasma centrale, (attenuated) Anaplasma marginale and Cowdria ruminantium), and from ticks (Theileria parva). The T. annulata attenuated cultured schizont vaccine is safe for all varieties of cattle. Blood derived vaccines are recommended mainly for young cattle, the age limit varying with the different vaccines and breeds of cattle. In older animals, monitoring of the individual response is needed. Immunization against T. parva requires simultaneous or postinoculation chemotherapy. The potential for accidental transmission of disease agents exists with all blood derived vaccines. Various degrees of resistance to field infection have been reported in animals immunized with live vaccines. Nevertheless, all of them engender a level of protection against natural challenge that justifies their use in field vaccination. Chemotherapy or chemoprophylaxis may prevent establishment of infection with the vaccinal parasites, and thus may interfere with elaboration of immunity. Outbreaks of disease in vaccinated herds, caused by antigenic variants among the tick-transmitted parasites, have been observed mainly in Babesia infections. In recent years, the main efforts towards improvement of live vaccines have been in the direction of replacing blood- and tick-derived parasites by those cultured in vitro under controlled standardized conditions.

Anaplasma↗
PubMed1983

Tick (Ixodes holocyclus) paralysis in the dog--induction of immunity by injection of toxin.

Three beagle dogs were immunised against the paralysing effects of holocyclotoxin, using toxic extracts derived from salivary glands of the Australian paralysis tick, Ixodes holocyclus. Upon subsequent challenge with four ED50's of toxin the animals were completely immune, whereas during the early stages 2 of 3 dogs became paralysed after injection with 0.5 ED50. Three immunised beagles, on which 15 I. holocyclus ticks had fed, showed no symptoms but a control beagle became paralysed after 4 I. holocyclus females fed on it. Treatment was instituted immediately upon the onset of clinical signs and the dog recovered uneventfully.

Animals↗
PubMed1978

The efficacy of showers for control of ectoparasites of sheep.

Ectoparasites of sheep in Britain include the tick Ixodes ricinus, the blowfly, Lucilia sericata, the ked, Melophagus ovinus and the lice, Damalinia ovis and Linognathus ovillus. The most important ectoparasite, however, is the mite Psoroptes communis ovis which causes sheep scab. This notifiable disease was eradicated from Britain in 1952 but was reported again in 1973. The control of ectoparasites depends largely on the efficient application of insecticide to the fleece and skin. Plunge dipping in a bath is generally regarded as the most efficient method and is compulsory for the control of sheep scab but it is not always the most convenient. After the eradication of sheep scab in 1952 plunge dipping was no longer compulsory and jetting, spraying and showering techniques were then employed for the other ectoparasites.

Animals↗
PubMed2006

Cluster of tick paralysis cases--Colorado, 2006.

Tick paralysis is a rare disease characterized by acute, ascending, flaccid paralysis that is often confused with other acute neurologic disorders or diseases (e.g., Guillain-Barré syndrome or botulism). Tick paralysis is thought to be caused by a toxin in tick saliva; the paralysis usually resolves within 24 hours after tick removal. During May 26-31, 2006, the Colorado Department of Public Health and Environment received reports of four recent cases of tick paralysis. The four patients lived (or had visited someone) within 20 miles of each other in the mountains of north central Colorado. This report summarizes the four cases and emphasizes the need to increase awareness of tick paralysis among health-care providers and persons in tick-infested areas.

Aged↗
PubMed1990

Induction of host resistance to Rhipicephalus appendiculatus in rabbits: effects of immunizing with detergent-solubilized tick tissue proteins.

Resistance to the hard tick, Rhipicephalus appendiculatus, was induced in rabbits by immunizing them with tick tissue proteins extracted with a detergent, Triton X-100. There was 25% mortality in female ticks fed on immunized rabbits as compared with those fed on controls. Similarly, there was a 40% and 60% reduction in the engorged weight and the weight of egg batches, respectively, of ticks fed on immunized rabbits. Western blot analysis of detergent-solubilized tick tissue proteins, carried out using immune sera, recognized a complex pattern of proteins. A strong reaction was observed with proteins with apparent molecular weights of 94,000 and 40,000 daltons.

Animals↗
PubMed2001

Assessing the association between the geographic distribution of deer ticks and seropositivity rates to various tick-transmitted disease organisms in dogs.

OBJECTIVE: To determine whether the geographic distribution of deer ticks (Ixodes scapularis) was associated with the distribution of dogs seropositive for various tick-transmitted disease organisms (ie, Borrelia burgdorferi, Rickettsia rickettsii, the human granulocytic ehrlichiosis [HGE] agent, Ehrlichia canis, and Bartonella vinsonii subsp berkhoffii). DESIGN: Serologic survey. SAMPLE POPULATION: Serum samples from 277 dogs in animal shelters and veterinary hospitals in Rhode Island. RESULTS: Overall, 143 (52%) dogs were seropositive for B burgdorferi, 59 (21.3%) were seropositive for R rickettsii, 40 (14.4%) were seropositive for the HGE agent, 8 (2.9%) were seropositive for E canis, and 6 (2.2%) were seropositive for B vinsonii. Regression analysis indicated that the natural logarithm of nymphal deer tick abundance was correlated with rate of seropositivity to the HGE agent and to B burgdorferi but not to rate of seropositivity to R rickettsii, E canis, or B vinsonii. Percentages of samples seropositive for B burgdorferi, R rickettsii, the HGE agent, and E canis were significantly higher for samples from the southwestern part of the state where ticks in general and deer ticks in particular are abundant than for samples from the northern and eastern portions of the state, where ticks are relatively rare. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that all 5 disease agents are in Rhode Island and pose a risk to dogs and humans. Knowledge concerning tick distributions may be useful in predicting the pattern of disease associated with particular tick species and may aid diagnostic, prevention, and control efforts.

Animals↗
PubMed1997

Evolution of repellent tolerances in representative arthropods.

Eight commercial insect repellents were tested against Ornithodoros parkeri (Acari: Argasidae), Dermacentor variabilis (Acari: Ixodidae), Aedes aegypti (Diptera: Culicidae), and Xenopsylla cheopis (Siphonaptera: Pulicidae). Patterns of tolerance to the test materials were distinctive for each test species. Levels of tolerance were coded as character state 0 (sensitive), 1 (intermediate), or 2 (tolerant) and mapped on a cladogram reflecting the accepted classification of the test species. Character state 0 was regarded as primitive, as indicated by the ontology of repellent tolerances in ticks. Aedes aegypti was least evolved and X. cheopis was most evolved in tolerance to repellents. Multiple parallelism of the arachnid and X. cheopis lines occurred in the evolution of the observed tolerances.

Aedes↗
PubMed2003

Climate change decreases habitat suitability for some tick species (Acari: Ixodidae) in South Africa.

Models predicting current habitat availability for four prominent tick species in Africa (Boophilus decoloratus, Amblyomma hebraeum, Rhipicephalus appendiculatus and Hyalomma truncatum) were constructed using remotely sensed information about abiotic variables and a point-to-point similarity metric. Year-to-year variations in the forecasted habitat suitability over the period 1983-2000 show a clear decrease in habitat availability, which is attributed primarily to increasing temperature in the region over this period. Climate variables were projected to the year 2015 using Fourier series analysis of the decadal abiotic data. The simulations show a trend toward the destruction of the habitats of the four tick species. In addition, a sensitivity analysis was developed to probe the changes in the habitat suitability in response to variations in temperature, vegetation availability and water vapour deficit. Four basic scenarios were studied: increasing or decreasing the temperature 1 or 2 degrees C together with correlated variations in the other abiotic variables. A decrease in temperature was predicted to promote habitat gain for every species except H. truncatum, while an increase of 1 degrees C was forecast to sustain a small but positive response in A. hebraeum and B. decoloratus. Increasing the temperature by 2 degrees C was forecast to have damaging effects on the habitat structure of all four species. The effect of climate warming on the habitat range of these ticks is considered in the light of economically sound control measures over an ecological background.

Animals↗
PubMed1999

The novel mitochondrial gene arrangement of the cattle tick, Boophilus microplus: fivefold tandem repetition of a coding region.

We sequenced across all of the gene boundaries in the mitochondrial genome of the cattle tick, Boophilus microplus, to determine the arrangement of its genes. The mtDNA of B. microplus has a coding region, composed of tRNA(Glu) and 60 bp of the 3' end of ND1, that is repeated five times. Boophilus microplus is the first coelomate animal known to have more than two copies of a coding sequence. The mitochondrial genome of B. microplus has other unusual features, including (1) reduced T arms in tRNAs, (2) an AT bias in codon use, (3) two control regions that have evolved in concert, (4) three gene rearrangements, and (5) a stem-loop between tRNA(Gln) and tRNA(Phe). The short T arms and small control regions (CRs) of B. microplus and other ticks suggest strong selection for small genomes. Imprecise termination of replication beyond its origin, which can account for the evolution of tandem repeats of coding regions in other mitochondrial genomes, cannot explain the evolution of the fivefold repeated sequence in the mitochondrial genome of B. microplus. Instead, slipped-strand mispairing or recombination are the most plausible explanations for the evolution of these tandem repeats.

Amino Acid Sequence↗
PubMed1996

Tick paralysis--Washington, 1995.

Tick paralysis (tick toxicosis)--one of the eight most common tickborne diseases in the United States (1)--is an acute, ascending, flaccid motor paralysis that can be confused with Guillain-Barre syndrome, botulism, and myasthenia gravis. This report summarizes the results of the investigation of a case of tick paralysis in Washington.

Animals↗
PubMed2001

Outbreak of Powassan encephalitis--Maine and Vermont, 1999-2001.

Powassan (POW) virus, a North American tickborne flavivirus related to the Eastern Hemisphere's tickborne encephalitis viruses, was first isolated from a patient with encephalitis in 1958. During 1958-1998, 27 human POW encephalitis cases were reported from Canada and the northeastern United States. During September 1999-July 2001, four Maine and Vermont residents with encephalitis were found to be infected with POW virus. These persons were tested for other arbovirus infections found in the northeast after testing for West Nile virus (WNV) infection was negative. This report describes these four cases, summarizes the results of ecologic investigations, and discusses a potential association between ticks that infest medium-sized mammals and the risk for human exposure to POW virus. The findings underscore the need for personal protective measures to prevent tick bites and continued encephalitis surveillance.

Aged↗
PubMed2006

Transcriptome analysis of the salivary glands of Dermacentor andersoni Stiles (Acari: Ixodidae).

Amongst blood-feeding arthropods, ticks of the family Ixodidae (hard ticks) are vectors and reservoirs of a greater variety of infectious agents than any other ectoparasite. Salivary glands of ixodid ticks secrete a large number of pharmacologically active molecules that not only facilitate feeding but also promote establishment of infectious agents. Genomic, proteomic and immunologic characterization of bioactive salivary gland molecules are, therefore, important as they offer new insights into molecular events occurring at the tick-host interface and they have implications for development of novel control strategies. The present work uses complementary DNA (cDNA) sequence analysis to identify salivary gland transcripts expressed by the Rocky Mountain wood tick, Dermacentor andersoni, a vector of the human pathogens causing Rocky Mountain spotted fever, Colorado tick fever, tularemia, and Powassan encephalitis as well as the veterinary pathogen Anaplasma marginale. Dermacentor andersoni is also capable of inducing tick paralysis. Automated single-pass DNA sequencing was conducted on 1440 randomly selected cDNA clones from the salivary glands of adult female D. andersoni collected during the early stages of feeding (18-24h). Analysis of the expressed sequence tags (ESTs) resulted in 544 singletons and 218 clusters with more than one quality read and attempts were made to assign putative functions to tick genes based on amino acid identity to published protein databases. Approximately 25.6% (195) of the sequences showed limited or no homology to previously identified gene products. A number of novel sequences were identified which presented significant sequence similarity to mammalian genes normally associated with extracellular matrix (ECM), regulation of immune responses, tumor suppression, and wound healing. Several coding sequences possessed various degrees of homology to previously described proteins from other tick species. Preliminary nucleotide variation analysis of these and other tick sequences suggests extensive nucleotide diversity, which has implications for evolution of tick feeding. Intra-species diversity studies can be a promising tool for identifying sequence variations potentially associated with phenotypic traits affecting vector-host-pathogen interactions.

Amino Acid Sequence↗
PubMed1984

Rickettsia conorii isolated from Rhipicephalus sanguineus introduced into Switzerland on a pet dog.

A tick/rickettsial survey in a household near Geneva, Switzerland, revealed that 30 (40%) of 75 nymphs and adults of the brown dog tick, Rhipicephalus sanguineus, were infected with a rickettsial agent biologically and antigenically indistinguishable from R. conorii, the causative agent of boutonneuse fever. Introduced in 1979 from either southern France or Italy by the family's pet dog, the tick infestation had steadily increased until 1981 when control measures were initiated. During 1980 and 1981, four persons associated with the household's pet dog contracted a febrile illness diagnosed as boutonneuse fever.

Agglutination Tests↗