[The tick--a disease carrier we have to learn to live with. "New" diseases require further research].
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The absence of clinical disease in cattle in communal grazing areas where farmers are changing from an intensive dipping programme to one of endemic stability to tick-borne diseases.
A two-year field study was conducted in four communal grazing areas in South Africa. Sera were collected from young cattle (6-18 months old) in these areas during the winters of 1991 to 1993. The sera were tested for antibodies to Babesia bovis, Babesia bigemina, Anaplasma marginale and Cowdria ruminantium. In two of the four areas, treatment with acaricide was erratic and dependent on the discretion of individual owners. In these areas the drought of 1992 had a major impact on tick burdens and there were changes in the seroprevalence to tick-borne diseases. In the other two areas there was a reduction in the intensity of acaricide application and this was associated with an increase in seropositivity to the tick-borne diseases. Increases in the prevalence of seropositivity and the presence of endemic instability, as calculated from inoculation rates, were not accompanied by outbreaks of clinical disease. Possible reasons for this are discussed.
Animals↗
Tick-borne diseases in Texas: a 10-year retrospective examination of cases.
The occurrence of Rocky Mountain spotted fever, human monocytotropic ehrlichiosis, tularemia, tick-borne relapsing fever, and a southern erythema migrans-like illness (Lyme/Lyme-like disease) is determined by the geographic distribution and seasonal activity of the particular vector tick(s). The flulike signs and symptoms early in the course of spotted fever rickettsiosis, ehrlichiosis, tularemia, and relapsing fever are nonspecific and do not readily suggest a particular diagnosis. Laboratory diagnosis, particularly during the acute stage of illness, often is elusive. Empiric treatment with doxycycline can be lifesaving for Rocky Mountain spotted fever and ehrlichiosis. This article provides insight into the significance of each of these tick-transmitted diseases in Texas.
Animals↗
Systemic activity of closantel for control of lone star ticks, Amblyomma americanum (L.), on cattle.
Cattle were treated once at 5 mg/kg orally or subcutaneously or daily at 0.1-5 mg/kg orally or 0.1-1 mg/kg subcutaneously with closantel, N-[5-chloro-4-[(4-chlorophenyl)cyanomethyl]-2-methylphenyl]-2-hydroxy-3, 5-diiodobenzamide, and numbers and weights of engorged females, weights of egg masses and hatch of eggs of lone star ticks, Amblyomma americanum, were recorded. Effectiveness of treatments on reproduction was determined by comparing total estimated larvae (EL) (EL = wt. egg mass X est. % hatch X 20000) of ticks from treated cattle with that of ticks from untreated cattle. With certain treatments, we also determined the effect of manure of treated cattle on survival of larvae of the horn fly, Haematobia irritans, or effect on survival and of fecundity of adult horn flies or stable flies, Stomoxys calcitrans, fed on blood from treated animals. The single oral treatment afforded essentially complete control of total EL only of ticks placed on the animal on the day of treatment, while the single subcutaneous treatment afforded greater than 92% control of total EL of ticks placed on animal on treatment day and for 6 weeks posttreatment. Daily treatments of 0.5 mg/kg or greater orally and 0.1 mg/kg or greater subcutaneously afforded essentially complete control of total EL of ticks throughout the treatment period (3-12 weeks) and for 1-7 weeks after treatment was discontinued. An estimated concentration of greater than 9 micrograms/ml of blood was calculated by probit analysis to be necessary to provide greater than 90% control of total EL of lone star ticks; that same concentration also provided greater than 90% control of hatch of eggs laid by treated females. A higher concentration (40 micrograms/ml) was necessary to prevent engorging of the females. No treatments tested were effective against larvae of the horn fly or adult horn flies or stable flies.
Animals↗
Foci of tick-borne diseases in southwest Germany.
Presently known tick-borne diseases in Germany include Lyme borreliosis, tick-borne encephalitis (TBE-virus, western subtype), Q-fever, babesiosis and presumably ehrlichiosis. Blood samples of 4,368 forestry workers in the State of Baden-Wuerttemberg (B-W), southwestern Germany, were tested for the presence of antibodies against Borrelia burgdorferi sensu lato, TBE-virus and Ehrlichia spp. (genogroup E. phagocytophila). Furthermore 12,327 ticks (Ixodes ricinus) collected in various areas of B-W were analysed by PCR and genotyping for the prevalence of pathogen RNA and DNA. The human seroprevalence rates of antibodies to B. burgdorferi sensu lato ranged from 18% to 52%, for TBE-virus from 0% to 43% and for Ehrlichia spp. from 5% to 16% in various counties of the State. The foci of B. burgdorferi and TBE-virus as indicated by antibody prevalence in humans are only partly overlapping with each other. The highest rates of TBE-virus antibodies are in concordance with available clinical data. However antibody prevalence up to 27% in areas with no reports of clinical cases was found, suggesting that TBE occurs throughout the State of B-W. The prevalence of Ehrlichia spp. antibodies suggests that ehrlichiosis plays a role as a tick-borne disease in Germany, but as long as no clinical data are available, this will remain unclear. Investigations of ticks for TBE-virus (n = 9,189) by nested PCR showed prevalence rates from 0% to 2.3% and for Ehrlichia spp. (n = 1,963) from 2.6% to 3.1%. Examination of ticks (n = 3,138) for the presence of B. burgdorferi sensu lato DNA was performed by PCR and revealed prevalence rates from 13.9% up to 24%. Furthermore 1,106 samples positive for B. burgdorferi sensu lato were used for genotyping. B. afzelii DNA was found in 407 ticks (36.8%), followed by B. garinii (21.9%), B. valaisiana (13.7%), and B. burgdorferi sensu stricto (9.9%). Double infection was found in 6.4% and triple infection in 0.8% of the ticks. 10.5% of the positive samples could not be classified. Prevention of tick-borne diseases has to focus on behavioural intervention to reduce individual tick exposure by proper behaviour in the environment, as a large-scale control of the tick population seems impossible and thus reduction of Lyme borreliosis and TBE through tick control is unlikely. Vaccination against TBE-virus should not only be recommended for high endemic areas but also for persons with a high individual risk.
Animals↗
World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of parasiticides for the treatment, prevention and control of flea and tick infestation on dogs and cats.
These guidelines are intended to assist the planning and conduct of laboratory and clinical studies to assess the efficacy of ectoparasiticides applied to dogs or cats for the purpose of treating, preventing and controlling flea and tick infestations. The term ectoparasiticide includes insecticidal and acaricidal compounds, as well as insect growth regulators. The range of biological activities accruing from animal treatment that are considered include: repellency and anti-feeding effects, knockdown, speed of kill, immediate and persistent lethal effects, and interference with egg fertility and subsequent development of off-host life cycle stages. Information is provided on the selection of animals, dose determination, dose confirmation and field studies, record keeping, interpretation of results and animal welfare. These guidelines are also intended to assist registration authorities involved in the approval and registration of new parasiticides, and to facilitate the worldwide adoption of harmonized procedures.
Animals↗
Control of Karoo paralysis ticks through vegetation management.
Karoo paralysis, caused by feeding Ixodes rubicundus females, is a major disease of small stock in South Africa. Control methods currently practised are almost exclusively chemical based. To limit overdependance on chemicals, vegetation management was investigated as a possible method for control, to be incorporated in an integrated tick management system. Laboratory and field experiments were conducted to determine, firstly, the extent of vertical migration and survival of ticks on long and short copper rods which simulated grasses as questing substrates; secondly, the infestation burdens of sheep exposed to similar tick challenges in pens with long and short grass; and thirdly, the effect of trimming the lower crown line of wild olive trees, simulating the browsing effect of goats, on tick density in the immediate environment of the trees. When ticks were exposed to optimal ( > 45 cm) and sub-optimal ( < 10 cm) length rods on which to quest, the extent of vertical migration over extended periods of time (up to 87 days) was significantly higher (P < 0.001) for the ticks exposed to long rods. Also, almost 3 times as many ticks exposed to long rods survived compared to those exposed to short rods. Sheep exposed to long grass were infested by twice as many ticks compared to those exposed to short grass. Tick density at modified wild olive trees (Olea europaea africana) (0.027 ticks/m2) differed significantly (P < 0.05) from that at control trees (0.088 ticks/m2). It is recommended that coarse grazers such as cattle and horses should be used to graze down long grasses before sheep are introduced into camps known to be infested with I. rubicundus. Similarly, domestic goats can, through their browsing effect on shrubs and trees, modify the vegetation and as such play an important role in an integrated tick management system.
Animals↗
Laboratory testing of insecticides for control of the winter tick.
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Animals↗
A survey of cattle producers in the Boophilus microplus endemic area of Queensland to determine attitudes to the control of and vaccination against tick fever.
A survey by mail was used to determine the views of beef producers in the Boophilus microplus endemic area of Queensland on the control of and vaccination against tick fever. Data from 448 questionnaires were analysed, representing 2.7% of beef producers in the survey area. Producers considered buffalo fly (Haematobia irritans exigua) infestation as the most important problem whereas tick fever ranked sixth overall. Private veterinarians were regarded as the most important source of information on vaccines for cattle followed by a weekly rural newspaper. From the survey we estimate that about 33% of producers used the tick fever vaccine produced by the Tick Fever Research Centre of Queensland Department of Primary Industries but there were significant (P < 0.05) variations between regions and herds. Large herds (> or = 400 head) in south-east Queensland were the most likely to be vaccinated against tick fever. Of the producers who did not use the vaccine, over 70% replied that there was no need to vaccinate because of the low risk of the disease in their herds. In 52% of unvaccinated herds the treatment of animals with acaricide was considered the most important means of tick fever control and 61% of these herds comprised Bos indicus x Bos taurus or Bos indicus cattle.
Anaplasma↗
Exploring tick saliva: from biochemistry to 'sialomes' and functional genomics.
Tick saliva, a fluid once believed to be only relevant for lubrication of mouthparts and water balance, is now well known to be a cocktail of potent anti-haemostatic, anti-inflammatory and immunomodulatory molecules that helps these arthropods obtain a blood meal from their vertebrate hosts. The repertoire of pharmacologically active components in this cocktail is impressive as well as the number of targets they specifically affect. These salivary components change the physiology of the host at the bite site and, consequently, some pathogens transmitted by ticks take advantage of this change and become more infective. Tick salivary proteins have therefore become an attractive target to control tick-borne diseases. Recent advances in molecular biology, protein chemistry and computational biology are accelerating the isolation, sequencing and analysis of a large number of transcripts and proteins from the saliva of different ticks. Many of these newly isolated genes code for proteins with homologies to known proteins allowing identification or prediction of their function. However, most of these genes code for proteins with unknown functions therefore opening the road to functional genomic approaches to identify their biological activities and roles in blood feeding and hence, vaccine development to control tick-borne diseases.
Animals↗
Interview with Daniel E. Sonenshine, Ph.D. Interview by Vicki Glaser.
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Animals↗
Tick-borne diseases of sheep and goats and their related vectors in Iran.
Haemoparasitic diseases have long been considered as a major problem to efficient sheep and goats production in Iran. Theileriosis due to Theileria hirci and babesiosis due to Babesia ovis and B. motasi are the most pathogenic protozoa. B. crassa, Anaplasma ovis and Eperythrozoon ovis are usually non-pathogenic and do not cause any apparent problem. The major tick genera found on sheep and goats are Hyalomma, Rhipicephalus, Haemaphysalis, Ixodes and rarely Dermacentor distributed in all part of Iran. Our studies indicate that only Hyalomma ticks transmit Theileria species but the others transmit Babesia, Anaplasma and Eperythrozoon. The two latter ones can also be transmitted through some biting flies and mechanical means. Control methods presently available in Iran rely almost entirely on: (i) vaccination of sheep and goats with cell culture vaccine for theileriosis; (ii) chemotherapeutic treatment for babesiosis and anaplasmosis; (iii) acaricides for control of tick vectors.
Anaplasmosis↗
The potential of some synthetic pyrethroids for control of the cattle tick (Boophilus microplus).
As part of a continuing programme to aid in the development of new acaricides, the potentials of three synthetic pyrethroids, permethrin, cypermethrin and decamethrin, were assessed against a range of resistant strains of the cattle tick (Boophilus microplus). The compounds were shown to be acaricidal, with decamethrin the most effective, giving efficient control of susceptible and organo-phosphorus resistant strains of the cattle tick at concentrations as low as one fifth of those previously used for any commercial acaricide. However higher concentrations were required for satisfactory control of the DDT-resistant strain. Permethrin-selection of a field strain containing a low percentage of DDT-resistant ticks led to rapid development of resistance to a level equivalent to that of the DDT-resistant strain. Further selection increased resistance to permethrin to a higher level than that shown in the DDT-resistant strain. This increased resistance to permethrin appears to be restricted mainly to this compound and is not associated with a marked increase in resistance to cypermethrin, decamethrin or DDT. The potential of organo-phosphorus compounds to potentiate the pyrethroids when the two classes of compounds are used as mixtures against the pyrethroid-resistant and susceptible strains was confirmed.
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[THE USE OF A GRANULATED TYPE DDT PREPARATION IN THE CONTROL OF THE VECTORS OF TICK-BORNE ENCEPHALITIS].
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Animals↗
Nitric oxide metabolites in naturally occurring canine babesiosis.
Babesiosis, caused by the virulent haemoprotozoan parasite Babesia canis rossi, is an important disease of dogs in South Africa. The nitric oxide metabolites, nitrate and nitrite (collectively termed reactive nitrogen intermediates or RNIs) were measured in admission sera from dogs in a babesiosis-endemic area. Five groups were prospectively studied: mild uncomplicated (n=9), severe uncomplicated (severe anaemia) (n=10) and complicated babesiosis (n=11); and two groups of healthy aparasitaemic dogs: endemic controls from the study area (n=10) and experimental dogs kept in tick-free conditions (n=10). Four measures of RNI production were studied: (i) serum RNI; (ii) serum RNI/creatinine ratio; (iii) fractional clearance of RNI (FC(RNI)); (iv) fractional excretion of RNI (FE(RNI)). Marked elevations of serum RNI occurred in only two dogs, both in the severe uncomplicated group. The highest concentration (log value 5.29 micromol/l) was in a dog that died, but concentrations in the other four dogs that died were unremarkable (0, 0.34, 1.66 and 2.64 micromol/l). Age, appetite and free serum haemoglobin were significant covariates for measures of RNI production. There were no significant differences among the babesiosis groups for serum RNI. Adjustment for creatinine had minor effects on the results. All babesiosis groups had significantly higher serum RNI and RNI/creatinine than the tick-free control group, but did not differ from the endemic controls except for the severe uncomplicated group, which had higher RNI/creatinine. The complicated group had significantly lower FC(RNI) and FE(RNI) than all other groups, except for the tick-free control group, which had similar FE(RNI). The results indicate that, in an endemic area, measures of RNI production are unlikely to be useful indicators of severity or outcome in canine babesiosis.
Animals↗
Development of a novel self-medicating applicator for control of internal and external parasites of wild and domestic animals.
Four trials, three in the United States and one in South Africa, were conducted to evaluate the potential value of a novel self-medicating applicator in the passive control of gastrointestinal nematodes in cattle and deer, and of files and ticks on cattle using oil-based treatments. The results of the trials demonstrated that this applicator is an effective and practical device for the passive treatment of both deer and cattle for trichostrongyle infections using the endectocide, moxidectin (Cydectin. Fort Dodge Animal Health, USA), of cattle for hom fly (Haemotobia irritans) infestations using the insecticide, cyfluthrin (CyLence, Bayer AG, Germany) and of cattle for tick infestations (in particular Amblyomma hebraeum and Rhipicephalus appendiculatus) using the acaricides deltamethrin and amitraz (Delete All, Intervet, South Africa).
Administration, Topical↗
[Ear tags--a prospective method for the long-term protection of livestock from ectoparasites].
Ear tags are a most effective method for protecting animals from ectoparasites for a long time with minimum expenditures and without polluting the environment. The method is based on a long evaporation of highly toxic insecticides, mainly pyrethroids, homogeneously spread in the substance of the filler which by penetrating into the animal's hair provide its constant protection. Ear tags were successfully used for control of population of bloodsucking Diptera, mites and myiasis flies.
Animals↗
Use of a mathematical model to study the control measures of the cattle tick Boophilus microplus population in New Caledonia.
Boophilus microplus is a common cattle tick of great economic importance in various tropical and subtropical countries like New Caledonia. The proposed model describes the population dynamics of female Boophilus microplus in the absence of resistant ticks. It is a system of six difference equations which can be mathematically analyzed. The analysis of the system shows the great importance of the eigenvalue denoted by lambda1. The population of ticks increases if lambda1 < 1 and decreases if lambda1 > 1. The lambda1 eigenvalue depends, in particular, on the parasitic surviving rate and encounter rate between the larvae and the cows. The treatments decrease the parasitic surviving rate as the agronomic measures decrease the encounter rate. This model permits to quantify the conditions of treatments (or of the efficacy of a vaccine) and of agronomic measures by which the populations are controlled. It shows that the different treatment rhythms and the presence or not of the wild or domestic refuges plays a major role on the dynamics of tick population.
Animal Husbandry↗