The life-cycle of Rhipicephalus haemaphysaloides haemaphysaloides under laboratory conditions.
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Seasonal variations related to mites were investigated by the Methylene Blue Agar (MBA) method in the houses of 157 AD patients living in Tokyo. Many mites were counted in the dust from carpets, Japanese straw mats (Tatami) and the floor under Tatami. In most places, the number of mites was found to increase in summer. In winter, however, mite levels increased in sofas and Japanese seat cushions. On the other hand, only small numbers of mites were found in mite-proof products. Based on the above data, were recommended mite elimination by various scientific techniques was recommended for 34 severe AD patients. Mite levels and clinical symptoms were again checked after one year and two years in the same seasons. In 17 of the 34 cases, mite elimination was carried out completely. In these cases, the ratio of mite decrease to less than 30% was 82%, and the ratio of improvement of clinical symptoms (remarkable improvement + improvement) was 88%. Almost complete cure was noted in 7 cases. On the other hand, in the remaining 17 cases, mite elimination was performed incompletely in 12 cases, and was hardly done at all in 5 cases. The ratio of mite decrease to less than 30% was 47%, and the ratio of improvement of clinical symptoms was 35%. Therefore, it was concluded that investigation of mite levels following mite elimination procedures is a most recommendable treatment for severe AD patients who are hypersensitive to house dust mites.
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The faeces of the dust mite are the most significant source of allergy for those allergic to the dust mite. During vacuum cleaning, faecal particles are emitted from the cleaner and into the air to form pathological concentrations. The aim of the study was to discover if these extreme concentrations could be prevented by the use of appropriate filters. As the allergen source, dust mite faeces were used. A Miele vacuum cleaner type S424i was used without filter, with S-Class filter, and with Super Air Clean Filter. In the first test 1 g, and in the second test 2 g of dust mite faecal particles were evenly spread and then vacumed up. While using each filter in turn, the expelled air was measured for faecal concentrations. The analysis was performed by counting the number of faecal particles, and determining the content of major allergen Der p I in the expelled air. Without a filter there was a massive concentration of faecal particles in the expelled air. The simple filter Type (S-class-filter) achieved a significant reduction on the emission of allergens. The more complex special filter (Super air clean filter), was able to remove all traces of allergens from the expelled air.
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Since mite antigen is an important causative agent of atopic dermatitis (AD), establishment and maintenance of a mite-reduced home environment would be an effective means to mitigate the symptoms. For establishing and maintaining a mite-reduced home environment, the structure of the residence, as well as the life style of the residents are important factors to consider. Based on a hypothesized behavior of the mite antigens a cleaning program was developed. Application of this program for establishing and maintaining a mite-reduced room in a patient's home produced a reduction in both mite population and mite antigen level, as well as a mitigation of the patient's symptoms. An air purifier was shown to have the ability to reduce, to a certain extant, specific mite antigens. The results suggest that an air purifier would be an effective contribution to the maintenance of a mite-reduced home environment.
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Two otic products not containing miticidal active ingredients were compared for the treatment of otoacariasis in 20 cats. It was concluded that treatment of feline otoacariasis can be achieved using products with an oil/wax base in conjunction with routine ear cleaning and total body parasitacide treatment.
Data are presented on the variable patterns of the seasonal dynamics of Ixodes ricinus L. ticks seen questing on the vegetation and feeding on small rodents (mice and voles) and squirrels within a British woodland focus of Lyme borreliosis. Information on tick infestation levels on pheasants is also presented. The results show a prolonged, unimodal pattern of tick activity, with ticks feeding throughout the year in this sheltered habitat. If host density is taken into account, squirrels are quantitatively more important than small mammals as hosts for larval ticks from April until July, and overwhelmingly so for nymphal ticks throughout the year. The observed inter- and intraspecific differences in tick infestation levels are related to the behaviour of both hosts and ticks. Squirrels, as competent hosts for Borrelia burgdorferi and frequent occupants of habitats closely associated with man, will contribute significantly to the risk of Lyme disease.
Ticks are economically important ectoparasites of domestic and wild animals and are considered to be second worldwide to mosquitoes as vectors of human pathogens. Current control methods for ticks, based primarily on the use of acaricides, have had limited efficacy in the reduction of tick infestations and the use of acaricides is often accompanied by serious drawbacks, including selection of acaricide-resistant ticks and environmental contamination. Development of improved vaccines against tick infestations offers a cost-effective and environmentally sound control method. Commercial vaccines currently marketed for control of cattle ticks have been effective in field studies when used in concert with integrated control strategies. However, new antigens are needed to increase the efficacy of tick vaccines. Although a limited number of protective antigens against tick infestations have been identified and characterized, discovery of new antigens remains the limiting step for improving the efficacy of tick vaccines. Recent technologies developed for gene discovery, including expression library immunization and evaluation of expressed sequence tags, show promise for rapid, systematic and global antigen screening and should provide a comprehensive approach to selection of candidate vaccine antigens. Design of future tick vaccines should target multiple tick species, as well as interfere with the transmission of pathogens.
The tick Boophilus microplus causes economic impact to cattle producers and has a great capacity to develop resistance to chemical acaricides. It is very important the development of new techniques to complement the control of this parasitosis. Biological control is a promising option to maintain acceptable levels of tick populations in cattle. Therefore, the present study evaluated the association of deltamethrin and the entomopathogenic fungus Metarhizium anisopliae against B. microplus larvae resistant to pyrethroid. The synthetic pyrethroid, deltamethrin, was used at concentrations of 0.39, 0.78, 1.56, 3.12 and 6.12 ppm, M. anisopliae was used at concentrations of 10(5), 10(6), 10(7) and 10(8) conidia ml(-1). Their associations were also evaluated in in vitro tests. The assays showed that the tick strain is resistant to deltamethrin, but high mortality rates were observed when deltamethrin was associated with the entomopathogen. The larvae's mortality rates ranged from 7 to 36.5% for the different concentrations of deltamethrin, however, for the different concentrations of M. anisopliae, the mortality rates ranged from 10 to 96.9%. Mortality rates were proportional to the concentrations used for both deltamethrin and the fungus. Predominantly, the association of pyrethroid and fungus resulted in higher larvae mortalility rates than those obtained with the respective non-associated concentrations. Thus, the present study indicates that this association can be used as a tool for integrated control of the tick B. microplus.
Controlled repeated infestation of Bos taurus and Bos indicus cattle resulted in a decline in the recovery of all R. appendiculatus instars. Resistance to infestation varied between individuals although all individuals manifested severe hypersensitivity at the attachment site, which was reflected in the grooming reflex.
Tick- and tsetse-borne diseases cost Africa approximately US$4-5 billion per year in livestock production-associated losses. The use of pyrethroid-treated cattle to control ticks and tsetse promises to be an increasingly important tool to counter this loss. However, uncontrolled use of this technology might lead to environmental damage, acaricide resistance in tick populations and a possible exacerbation of tick-borne diseases. Recent research to identify, quantify and to develop strategies to avoid these effects are highlighted.
The rapid population growth in subsaharan Africa necessitates a great increase in animal production in the more humid zones. Vector-borne diseases occurring in these zones will assume more importance, but are difficult to control. They include theileriosis and heartwater. Recent developments in research on these diseases are presented. Indigenous animal populations in endemic areas, subjected to natural selection, are far less susceptible than exotic stock. Heartwater, caused by the rickettsia Cowdria ruminantium, transmitted by Amblyomma ticks, causes high mortality in exotic ruminants. It has received much attention in recent years, partly because the disease has been introduced from Africa into the Caribbean and threatens the American mainland. Since the recent success of in vitro culture, much progress in research has been made, but so far prevention still relies mainly on acaricidal tick control; an infection and treatment method is used on a limited scale. Antigenic diversity is a complication for immunization procedures. Theileria parva (East Coast fever, Corridor disease and January disease) and T.annulata (Mediterranean or tropical theileriosis) are the most pathogenic of the 6 species of this protozoan genus that infect cattle. Great progress has been made in recent years in knowledge on the immunology, the epidemiology, the taxonomy and the chemotherapy of theileriosis. Intensive acaricidal tick control can now be supplemented by an attenuated schizont vaccine against T.annulata, while immunization against East Coast fever is carried out on a limited scale using virulent sporozoite infection and treatment. Research on recombinant vaccines is promising. Antigenic diversity in T.parva is a serious complication.
Experience has demonstrated that the exclusive use of acaricides as a control method against cattle ticks causes several problems, and is not totally effective. Other methods need to be added in order to achieve better and more profitable control of these parasites. Groups of 12 to 15 engorged ticks, bred on bovines, were individually incubated at six temperatures (T = 24, 26, 28, 30, 32, and 34 degrees C) and four relatives humidities (RH = 100, 80, 75.5, and 70%), creating 24 variants. The onset of oviposition and eclosion (emergence of larvae from eggs) was observed in all ticks, and preeclosion times (PET) were determined. A linear regression equation for the velocity of development with temperature as a function of the inverse of PET was calculated for each RH value. For each RH the minimum thermal threshold (MTT) was obtained by extrapolation and the effective temperature summation (ETS) calculated from the equation (incubation temperature--MTT) x PET. The four MTT values obtained were not significantly different; the mean value of MTT was 15.25 degrees C. The thermal constants did not prove to be not statistically different over the range of RH values employed in the experiments, the mean being 354.04 degrees C-day.
As part of a series of studies associated with the development of improved vaccines for heartwater (a tick-borne disease of ruminant livestock caused by Cowdria ruminantium), field surveys were carried out to assess losses associated with the disease and the costs associated with controlling it in the two main agro-ecological zones of Zimbabwe (lowveld and highveld) where heartwater is believed to be endemic and epidemic, respectively. In each zone, a cross-sectional study was performed in the main farming systems (smallholder (SH) and large-scale commercial (LSC) beef and dairy), followed by longitudinal studies in the same sectors to improve data accuracy for some parameters. Suspected heartwater-specific mortality in cattle was similar in all LSC sectors (p = 0.72) accounting for a median 1% mortality risk. Heartwater-specific mortality in SH areas was not assessed due to poor diagnostic ability of the farmers. Few LSC farms and SH households kept sheep; suspected heartwater-specific mortality in LSC sheep was 0.8% in the lowveld and 2.4% in the highveld. Goats were a major enterprise in SH areas but not on LSC farms. Suspected heartwater mortality in LSC goats was 0.8% at one site in the highveld and 17.5% on a farm in the lowveld. Application of acaricides was the major control method for heartwater and other tick-borne diseases on both SH and LSC farms. On LSC farms, plunge dipping was used most frequently and the number of acaricide applications ranged widely between 3 and 52 per year. The total cost of acaricides per head per annum was higher in highveld dairies than in highveld and lowveld beef enterprises (p = 0.03). In SH areas, cattle plunge dipping was conducted by the government with an average frequency of 8 +/- 2 (sd) immersions per annum in both the lowveld and highveld. The type of tick control on sheep and goats in all production systems was highly variable (ranging from none to hand removal or intensive acaricide treatment). Suspected heartwater cases on LSC farms were treated with tetracyclines; treatment was not reported in SH areas. Reported treatment costs were high (median Z$ 120) and highly variable (range Z$-833). Vaccination against heartwater with the live, blood-based vaccine was reported on only one LSC farm. LSC farms applying acaricide 30 or more times per year reported higher morbidity (p < 0.0001) and mortality (p < 0.0001) than farms applying acaricides less than 30 times a year. This finding supports the use of reduced tick control in the management of heartwater in Zimbabwe.