[Basic principles in protecting workers and population of the Baĭkal-Amur Railroad area from ixodid ticks and blood-sucking flies].
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Animals↗
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Relationship between ticks and Zebu cattle in southern Uganda.
Tick populations were observed on zebu (Bos indicus) cattle over a period of 2 years at Entebbe, Uganda where the climate was thought to be highly favourable for the free-living stages of ticks. collections of all instars of ticks were made from the body surfaces of the cattle at intervals of between 1 and 5 weeks. The species recorded in order of decreasing abundance were Rhipicephalus appendiculatus, Amblyomma variegatum, Boophilus decoloratus, Rhipicephalus evertsi evertsi, Rhipicephalus simus, Rhipicephalus compositus and Hyalomma marginatum rufipes. The rankings of the cattle based on burdens of any particular species of tick were always correlated with their rankings for other species; animals that carried more adult stages of a species also carried more of its immature stages. There were more adult males than females of R. appendiculatus, A. variegatum and R. e. evertsi even when the cattle had had all ticks removed 1 week previously; several possible mechanisms are suggested to explain the biased sex ratio. It is concluded that there is promise for improvement in control of 3-host ticks by increasing the resistance of herds of zebu cattle by culling or selective breeding.
Animals↗
Pathogenicity of four strains of entomopathogenic fungi against the bovine tick Boophilus microplus.
OBJECTIVE: To evaluate the pathogenicity of 4 strains of the entomopathogenic fungi Metarhizium flavoviride var flavoviride and Metarhizium anisopliae var anisopliae in vitro against the bovine tick Boophilus microplus. SAMPLE POPULATION: 300 B. microplus females were used for each series of 5 conidial suspensions of the 4 fungal strains; a control group of 60 females was treated with sterilized water. PROCEDURE: For each fungal strain, sporulating cultures were used to produce conidial suspensions containing 10(4), 10(5), 10(6), 10(7), and 10(8) conidia/ml. A bioassay was performed by immersing B. microplus females in conidial suspensions; the procedure was repeated with a new group of 60 females for each dilution (a total of 300). A control group was immersed in the same volume of sterilized distilled water. Ticks were maintained at 27 C and 80% relative humidity for 7 days, and the following variables were evaluated: weight before egging, egging weight, percentage eclosion, reproductive efficiency, and percentage control. RESULTS: A low index of eclosion was found in the treated groups, with a progressive decrease in percentage eclosion (control = 100%) with increased conidial concentration. The highest level of effectiveness of biocontrol was detected in groups treated with concentrations of 10(7) and 10(8) conidia/ml. CONCLUSIONS AND CLINICAL RELEVANCE: Strains of the entomopathogenic fungi M. anisopliae var anisopliae and M. flavoviride var flavoviride were effective as biological control agents against B. microplus, with M. flavoviride strain CG-291 being the most effective. The pathogenicity of these strains and the development of an application method for this fungus for control of ticks may result in improved animal productivity and a reduction in environmental pollution through the use of fewer chemical insecticides.
Animals↗
Boophilus microplus infection by Beauveria amorpha and Beauveria bassiana: SEM analysis and regulation of subtilisin-like proteases and chitinases.
Beauveria bassiana is a well-known broad-range arthropod pathogen which has been used in biological control of several pest insects and ticks such as Boophilus microplus. Beauveria amorpha has both endophytic and entomopathogenic characteristics, but its capacity for biological control has still not been studied. During the processes of host infection, B. bassiana and B. amorpha produce several hydrolytic extracellular enzymes, including proteases and chitinases, which probably degrade the host cuticle and are suggested to be pathogenicity determinants. To access the role of these enzymes during infection in the tick B. microplus, we analyzed their secretion during fungus growth in single and combined carbon sources, compared to complex substrates such as chitin and B. microplus cuticle. Chitin and tick cuticle-induced chitinase in both fungus and protease was induced only by tick cuticle. SEM analysis of B. amorpha and B. bassiana infecting B. microplus showed apressorium formation during penetration on cattle tick cuticle.
Animals↗
Influence of annual and biennial prescribed burning during March on the abundance of Amblyomma americanum (Acari: Ixodidae) in central Georgia.
A 5-yr study to evaluate the influence of annual and biennial prescribed burning in March on the abundance of Amblyomma americanum (L.) was conducted on Oconee Wildlife Management Area in the Piedmont physiographic region of Georgia. Tick abundance on plots embedded in larger burned and unburned areas were monitored with cloth drags and CO2-baited cloth panels monthly during March through September from 1987 through 1991. Annual and biennial prescribed burning from 1988 to 1991 significantly reduced the abundance of larvae, nymphs, and adults but did not alter their seasonal trends of abundance. Annual burning more consistently suppressed all life stages than biennial burning. The magnitude of tick suppression tended to increase with successive burns, especially with the annual burning regime. The order of vulnerability to direct incineration appeared to be overwintered larvae > adults > nymphs; however, only overwintered larvae were highly vulnerable. Consistent reductions in larvae during June-September following burning were associated with reduced litter depths and presumably lowered habitat suitability. During years of fire omission, the abundance of larvae on biennially burned plots increased to levels equal to or exceeding those on unburned plots. Based on cloth drag sampling, mean percentage control during 1988-1991 for larvae, nymphs, and adults, respectively, was 80, 75, and 70% on annually burned plots and 48, 73, and 65% on biennially burned plots. Frequent late-winter prescribed burning, which is commonly used to achieve wildlife habitat management objectives, could be an effective and economical component of an integrated A. americanum control program in habitats ecologically suited to regimes of frequent fire.
Animals↗
Tick-borne encephalitis: development of a paediatric vaccine. A controlled, randomized, double-blind and multicentre study.
A total of 522 children between 18 months and 14 years and 191 adults between 18 and 60 years were vaccinated with TBE-vaccine according to an abbreviated schedule (0, 7, 21). The aim of the study was to investigate whether reducing the amount of antigen in the vaccination for children would preserve an adequate immune response and decrease the rate of side-effects. Efficacy was determined on the extent to which children, vaccinated with the low doses (0.4 microgram or 0.75 microgram), reacted by developing antibodies in the same way as adults treated with the approved dose of 1.5 micrograms (equivalence of titres). The titres obtained in the children with the two lower doses were equivalent to those in the adults obtained with the standard dose. Titres decreased in the children with increasing age. Children older than 12 years in the approved dosage group had the same median titres as adults. The frequency of side-effects in the two lower dose groups, especially raised temperature, was markedly reduced. Whereas 30.1% of the children vaccinated with the approved dose had raised temperature higher than 38 degrees C only 18.8% and 18.4%, respectively, of the children vaccinated with the lower doses developed such temperatures. This improved tolerance in terms of raised temperature was also reflected in the other general reactions such as tiredness, joint pain or headache.
Adult↗
Acquired resistance in dogs to repeated infestation with Ixodes scapularis (Acari: Ixodidae) reduces tick viability and reproductive success.
The purpose of this study was to determine whether dogs develop acquired resistance to adult Ixodes scapularis infestation in an experimental model. Five dogs were each infested with ten mating pairs of ticks every week for 7 consecutive weeks, another five dogs were each infested with ten mating pairs once every 2 weeks for 10 weeks and four dogs served as controls not exposed to ticks. All ticks were allowed to feed to repletion and were collected only after dropping from the host. Several variables were measured to determine the extent of blood feeding success. Regression analysis indicated that the engorgement success, survival and mean tick engorgement weight declined with repeated infestation in both groups of dogs (p < 0.05). Tick oviposition as well as the F1 viability declined with each successive infestation in both groups. These results suggest that repeated infestation with I. scapularis elicits a protective immune response against tick feeding and could serve as a limiting factor in the spread and transmission of Borrelia burgdorferi.
Animals↗
[The reaction of taiga ticks (Ixodes persulcatus P. SCH) to carbon dioxide and several prospects for its use in field research].
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Animals↗
Influence of exposure period and management methods on the effectiveness of chickens as predators of ticks infesting cattle.
Experiments undertaken on Rusinga Island, Kenya, indicated that Rhipicephalus appendiculatus (Neumann) was the predominant tick consumed on tick-infested cattle by chickens, followed by Amblyomma variegatum (Fabricius), Boophilus decoloratus (Koch) and Rhipicephalus evertsi evertsi (Neumann). The number of ticks consumed by chickens released with cattle in a 3 h release period was not significantly different from ticks consumed in a 4 h release period. In a free management system, chickens 1-3 months of age consumed more ticks than older ones; in a confined management system however, chickens 4-6 months of age consumed more ticks than younger birds. Although the numbers of ticks consumed by local and exotic breeds of chickens were not significantly different, a period of 8-10 weeks was necessary for the exotic breeds to become behaviorally adapted to tick predation on cattle. Local chickens bred in environments where cattle were absent took a shorter period of 4-6 weeks to adapt. It was concluded that the relatively large number of ticks consumed by each chicken during the 3 or 4 h release period is an indication that a good reduction of ticks on cattle can be achieved through tick predation by chickens. The preponderance of R. appendiculatus over other tick species consumed was a reflection of its relative abundance on cattle on the island rather than a selective preference for tick species.
Animal Husbandry↗
Multiplex real-time PCR for detection of anaplasma phagocytophilum and Borrelia burgdorferi.
A multiplex real-time PCR assay was developed for the simultaneous detection of Anaplasma phagocytophilum and Borrelia burgdorferi. The assay was tested on various Anaplasma, Borrelia, Erhlichia, and Rickettsia species, as well as on Bartonella henselae and Escherichia coli, and the assay was found to be highly specific for A. phagocytophilum and the Borrelia species tested (B. burgdorferi, B. parkeri, B. andersonii, and B. bissettii). The analytical sensitivity of the assay is comparable to that of previously described nested PCR assays (A. phagocytophilum, 16S rRNA; B. burgdorferi, fla gene), amplifying the equivalent of one-eighth of an A. phagocytophilum-infected cell and 50 borrelia spirochetes. The dynamic range of the assay for both A. phagocytophilum and B. burgdorferi was >/=4 logs of magnitude. Purified DNA from A. phagocytophilum and B. burgdorferi was spiked into DNA extracted from uninfected ticks and from negative control mouse and human bloods, and these background DNAs were shown to have no significant effect on sensitivity or specificity of the assay. The assay was tested on field-collected Ixodes scapularis ticks and shown to have 100% concordance compared to previously described non-probe-based PCR assays. To our knowledge, this is the first report of a real-time multiplex PCR assay that can be used for the simultaneous and rapid screening of samples for A. phagocytophilum and Borrelia species, two of the most common tick-borne infectious agents in the United States.
Anaplasma phagocytophilum↗
Modelling the field efficacy of a genetically engineered vaccine against the cattle tick, Boophilus microplus.
The cattle tick Boophilus microplus Canestrini (Ixodidae) is an obligate parasite of bovines in the tropics. Vaccination against the tick, using concealed antigens, has previously been demonstrated to give partial protection which can vary under field conditions. In this paper computer modelling is used to evaluate the potential impact of the vaccine on populations of ticks on grazing cattle. The degree and duration of protection required to maintain tick numbers at acceptable levels is investigated. Results of the computer analyses have been used to guide the further development of the vaccine and to support an application for registration of the vaccine for control of the cattle tick in Australia. They demonstrate the contribution that modelling can make in evaluating the novel impacts that new technologies may have on the host-parasite relationship in different ecological environments.
Animals↗
Insecticides and acaricides: resistance and environmental impact.
Insecticides continue to be the primary means of control for ectoparasites on livestock. Intensive use of these materials has led to resistance to organochlorines, organophosphates and pyrethroids among populations of Haematobia irritans irritans, H. irritans exigua and Lucilia cuprina. Similarly, use of acaricides has led to resistance in one-host Boophilus ticks to all currently-used organophosphate-carbamates, synthetic pyrethroids and amidines. Resistance in multi-host ticks is less widespread. New chemicals are available for the control of resistant ectoparasites, but there are concerns over resistance and residues problems, which prompt the authors to discuss new pest management strategies. Environmental concerns are raised regarding the use of pesticides on livestock.
Animals↗
Tactile sensitivity in Asperger syndrome.
People with autism and Asperger syndrome are anecdotally said to be hypersensitive to touch. In two experiments, we measured tactile thresholds and suprathreshold tactile sensitivity in a group of adults with Asperger syndrome. In the first experiment, tactile perceptual thresholds were measured. Two frequencies of vibrotactile stimulation were used: 30 and 200 Hz. The results demonstrated significantly lower tactile perceptual thresholds in the Asperger group at 200 Hz but not at 30 Hz, thus confirming tactile hypersensitivity but only for one class of stimulus. A second experiment investigated whether self-produced movement affected the perception of touch in a group of adults with Asperger syndrome. A suprathreshold tactile stimulus was produced either by the participant (self-produced condition) or by the experimenter (externally produced condition) and participants were asked to rate the perception of the tactile stimulation. The results demonstrated that, while both Asperger and control groups rated self-produced touch as less tickly than external touch, the Asperger group rated both types of tactile stimulus as significantly more tickly and intense than did the control group. This experiment confirms the finding of tactile hypersensitivity, but shows that the perceptual consequences of self-produced touch are attenuated in the normal way in people with Asperger syndrome. An abnormality in this process cannot therefore account for their tactile hypersensitivity.
Adolescent↗
Boophilus microplus: passage of bovine immunoglobulins and albumin across the gut of cattle ticks feeding on normal or vaccinated cattle.
Cattle were vaccinated with antigens from adult female Boophilus microplus and haemolymph was collected from female ticks which had engorged on these animals and on matched control cattle. Radio-immunoassay for bovine plasma proteins in haemolymph from ticks fed on control cattle showed low concentrations of IgG1 and albumin. There was a significant increase in bovine plasma proteins passing across the gut in ticks fed on vaccinated cattle, with an average of 150 times more albumin and four to five times more IgG1 in the haemolymph. Ticks with obviously damaged gut had the highest concentrations of bovine plasma proteins but apparently undamaged ticks from vaccinated cattle also had elevated protein concentrations.
Animals↗
The mitochondrial genomes of soft ticks have an arrangement of genes that has remained unchanged for over 400 million years.
There are two major groups of ticks: soft ticks and hard ticks. The hard ticks comprise the prostriate ticks and the metastriate ticks. The mitochondrial (mt) genomes of one species of prostriate tick and two species of metastriate ticks had been sequenced prior to our study. The prostriate tick has the ancestral arrangement of mt genes of arthropods, whereas the two metastriate ticks have rearrangements of eight genes and duplicate control regions. However, the arrangement of genes in the mt genomes of soft ticks had not been studied. We sequenced the mt genomes of two species of soft ticks, Carios capensis and Ornithodoros moubata, and a metastriate tick, Haemaphysalis flava. We found that the soft ticks have the ancestral arrangement of mt genes of arthropods, whereas the metastriate tick, H. flava, shares the rearrangements of mt genes and duplicate control regions with the other two metastriate ticks that have previously been studied. Our study indicates that gene rearrangements and duplicate control regions in mt genomes occurred once in the most recent common ancestor of metastriate ticks, whereas the ancestral arrangement of arthropods has remained unchanged for over 400 million years in the lineages leading to the soft ticks and the prostriate ticks.
Animals↗
Daily mean number of eggs laid by the southern cattle tick (Acari: Ixodidae) compared with mean egg mass weight.
Among several methods used to estimate the efficacy of an acaricide is the Drummond adult test, based on formulas which permit the assessment of the reproductive capacity of treated female ticks in comparison with controls. A constant value of 20,000 is normally used in these formulas, because this figure approximates the number of larvae that will hatch from 1 g of eggs. In laboratory studies conducted on large numbers of ticks, egg counting is a time-consuming and fastidious operation. Therefore, in quantitative studies, sampling techniques are more convenient. The use of the weight of egg masses laid by ixodids is adequate because eggs congregate in clusters. Experimental results have demonstrated that the analysis of the mean daily weight of egg aliquots in comparison with actual counts, from the 1st to the 20th d of oviposition, did not permit rejection of the hypothesis that 20,000 would be a representative number of eggs contained in 1 g. When aliquots were weighed only on the 20th or the 30th d of the oviposition-incubation period, and the results were analyzed in comparison with egg counts, the value of 20,000 no longer was reliable to express the number of Boophilus microplus (Canestrini) eggs contained in 1 g.
Animals↗
[A trial at using the systemic action of ivermectin for suppressing the vector capacity of ticks (Ixodidae) infected with the tick-borne encephalitis virus].
Adult Dermacentor marginatus hatched from nymphs infected with TBE virus and poisoned with ivermectin retain their vector abilities. Even small individuals with a 1.5-2 times lesser mass as against the reference mass contain the virus in the body in the same titers and the virions in salivary gland alveoli. Administration of an oil solution of ivermectin into the stomach of white mice, nymph feeders, in a dose surpassing threefold the dose recommended for intramuscular injection of this agent completely suppressed shedding of intact nymphs but did not suppress it in those infected. The nymph mass, size and mass of adult ticks hatched from them dropped under the effect of ivermectin dosage build-up in both intact and infected ticks, but these processes were slower in ticks infected with TBE virus. The authors suggest that the ticks infected with TBE virus are much more resistant to the process of gamma-aminobutyric acid depression, the mechanism of ivermectin action. They emphasize the necessity of bearing in mind the possible differences in the reactions to systemic poisons of intact and infected ticks when organizing vector control measures.
Animals↗
Identification of a target population for immunisation against East Coast fever in coastal Kenya.
Two experiments were carried out to identify the target population of cattle for immunisation against East Coast fever (ECF) using the infection-and-treatment method. Firstly, a sentinel-calf study was used to determine the age window for ECF immunisation by determining ages at clinical detection of infection with Theileria parva. Six groups of five naive cross-bred (Bos taurus/Bos indicus) male calves, introduced at intervals of 2 months at a mean age of 26 days, were exposed to natural tick challenge on a high ECF-risk, small-holder farm in the coastal lowland, coconut-cassava agro-ecological zone of coastal Kenya. Secondly, a challenge study evaluated the relationship between the presence of T. parva antibodies and immunity. Ten indigenous adult Zebu cattle and nine Zebu young stock purchased from farmers in the same zone, and eight cross-bred calves (survivors of the sentinel-calf study) were challenged with 10 times the immunising dose of T. parva Marikebuni stock. Twenty-four of these 27 cattle had high antibody titres before challenge. Two cross-bred calves, obtained from an ECF-free area and seronegative to T. parva schizont antigen, also were challenged and used as susceptible controls. Twenty-five (83%) of the 30 sentinel calves contracted ECF over an age range of 36-116 days (mean 72 days). The remaining five calves died of other causes within 2 months of arrival on the farm. Fourteen of the 25 calves survived the infection and developed antibodies to T. parva. Despite tick control, seven of these 14 calves had a second episode of ECF and two died. In total, 13 of the 25 calves that contracted ECF died. Only one of 19 indigenous Zebu animals developed clinical ECF when challenged with T. parva Marikebuni (mild clinical signs with spontaneous recovery). Of the eight cross-bred survivors from the first experiment, only one succumbed to ECF when challenged and it died. Both susceptible cross-bred calves developed severe clinical signs of ECF and one died. The experimental studies show that in the high ECF-risk areas of the coconut-cassava zone of coastal Kenya, immunisation against ECF in cross-bred (B. taurus/B. indicus) cattle should be targeted at an early age (preferably within 1-2 months of birth).
Agriculture↗