Effects of an acaricide on asthmatic children with house dust mite allergy

D'Allergen is a recently available acaricidal and allergen reducing agent. To study any beneficial effects of treating houses with this agent in asthmatic children with dust mite allergy, histamine bronchial responsiveness was measured in 18 children before and 6-8 weeks after their homes were treated with the agent. Comparisons were with nine similar asthmatics whose homes were not treated. The mean provocative concentration of histamine causing a 20% fall in forced expiratory volume in 1 s (PC20) increased from 1.02 mg/L to 2.07 mg/L in all 18 children who were studied (1.01 doubling doses). Bronchial responsiveness was relatively unchanged in a well matched control group of nine children studied over comparable time periods (PC20 pre was 1.25 mg/L, PC20 post was 0.67 mg/L). The results suggest that treating homes with D'Allergen reduces bronchial reactivity in asthmatic residents with house dust mite allergy.

[Asthma-allergy. Altitude: a study model]

Several epidemiological studies have now established the relationship between atopy and bronchial asthma. The study of the role of altitude in sensitization, bronchial reactivity, clinical symptoms and allergen exposure in asthma is a good model for understanding the disease. It is now demonstrated that in altitude there is a major decrease in the number of mites (one of the major aeroallergens) and a low mite antigenic load (measured with monoclonal antibodies). In altitude, the climatic factor which has by far the greatest effect on the development of mites is indoor relative humidity which is much lower that at sea level. These findings explain the clinical improvement of some asthmatic patients and help understand the association between the presence of indoor allergens and asthma.

Domiciliary air filtration units, symptoms and lung function in atopic asthmatics

Air infiltration units (AFUs) incorporating a high efficiency particulate air filter are theoretically able to remove almost all potential airborne allergens. This may have implications for subjects with allergic lower respiratory disease. AFUs were placed in the living room of 12 atopic asthmatics, and the internal filters were inserted and removed in a double-blind fashion. No difference in subjective symptom scoring, spirometry or bronchial reactivity was demonstrated. Peak expiratory flow rate (PEFR) variability was significantly improved from baseline readings, and there was a trend towards higher mean PEFRs when the filters were present in the AFU. Trends towards lower levels of airborne micro-organisms were also demonstrated when the filters were present, however no effect upon total airborne dust and airborne Der pI could be demonstrated.

Ectoparasites of opossums and raccoons in southeastern Georgia

Twelve species of ectoparasites (four fleas, three ticks, three chiggers, one macronyssid mite, and one atopomelid mite) were recovered from 42 opossums, Didelphis virginiana Kerr, live-trapped from September 1992 through April 1994 in southeastern Georgia. The fleas, Ctenocephalides felis (Bouché) (prevalence = 19%) and Polygenis gwyni (C. Fox) (36%); the ticks, Dermacentor variabilis (Say) (40%) and Ixodes scapularis Say (19%); and the macronyssid mite, Ornithonyssus wernecki (Fonseca) (21%), exhibited the highest infestation prevalences on opossums. The atopomelid mite, Didelphilichus serrifer Fain, and the chigger mite Leptotrombidium peromysci Vercammen-Grandjean & Langston, both ectoparasites of opossums, are reported from Georgia for the first time. Six species of ectoparasites (one chewing louse, four ticks, and one macronyssid mite) were collected from 58 raccoons, Procyon lotor (L.), examined between October 1992 and September 1993 in the same region. The chewing louse, Trichodectes octomaculatus Paine (prevalence = 24%); and the ticks, Amblyomma americanum (L.) (69%), D. variabilis (55%), and Ixodes texanus Banks (24%), exhibited the highest infestation prevalences on raccoons. Three species of ticks, A. americanum, D. variabilis, and I. scapularis, were the only ectoparasites recovered from both host species. Several of the ectoparasites collected are proven vectors of pathogenic agents that affect humans and animals.

Specific immunotherapy in asthma

There is a growing appreciation of asthma as an inflammatory disease. Immunotherapy may play a role in modulating immunologic responses including inflammatory mediator production from cells involved in asthma. Studies of pollen-sensitive asthma have demonstrated beneficial effects of specific immunotherapy for grass, birch, and ragweed pollen-induced asthma. However, risk of systemic reactions exists, especially when specific immunotherapy is administered during the specific allergen season. House dust mite immunotherapy has benefitted asthmatic children more than adults. Patients having unstable pulmonary function may be at the highest risk of having systemic reactions to such immunotherapy. Animal dander immunotherapy and immunotherapy for molds including Clasdosporium and Alternaria may improve selected asthmatic patients. Avoidance of the offending allergen is still, however, the preferred mode of treatment of allergic asthma.

House dust mite allergen avoidance: a randomized controlled trial of surface chemical treatment and encasement of bedding

To test the effectiveness of a house dust mite (HDM) allergen avoidance strategy we conducted a randomized controlled trial in 35 atopic subjects with asthma, aged 13 to 60 living in Sydney - a high HDM allergen environment. After a 3 month run-in period, subjects were randomized to active allergen avoidance treatment (n = 17) or placebo (n = 18) groups and followed for 6 months. The active treatment involved placing impermeable covers over the mattress, pillows and duvet and spraying the remaining bedding, as well as the carpets and furniture, with a tannic acid/acaricidal spray. Subjects kept a daily record of symptoms and peak expiratory flow rates and had 3 monthly assessments of lung function and airway hyperresponsiveness (AHR). Dust samples were collected from the bed, the bedroom floor and the living room floor at 3 monthly intervals and 2 weeks after the treatment. Mean HDM allergen levels at baseline at these sites were, in the active group, 15.5, 9.6 and 10.2 micrograms Der p I/g of fine dust, and, in the placebo group 25.7, 11.8 and 6.3 micrograms/g. Two weeks after the allergen avoidance treatment the HDM allergen level in the beds was reduced to 29% of baseline (95% CI 16-50%, P = 0.038 compared with placebo), but was not significantly different at 3 or 6 months. There was also no significant effect of the allergen avoidance treatment on symptom scores, peak flow variability, lung function or AHR P > 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Partial inhibition of the early and late asthmatic response by a single dose of salmeterol

The long-acting beta 2-agonist salmeterol has been suggested to have other pharmacologic activities, that is, antiinflammatory capacities, in addition to its bronchodilator properties. We investigated the protective effect of 50 micrograms salmeterol in a placebo-controlled study on house dust mite-induced early- and late-phase reactions in 19 atopic asthmatic subjects. FEV1 and methacholine airway reactivity (AR) were measured. Eosinophils and their activation markers in peripheral blood were counted as indirect parameters of inflammation. Corrections were made for confounding of bronchodilator effects by salmeterol and the spontaneous diurnal variation, using saline inhalation as a control. Salmeterol completely inhibited the fall in FEV1 up to 10 h after the house dust mite challenge. Nevertheless, after correction, a biphasic response was present in the salmeterol group. Salmeterol protected against the allergen-associated increase in AR 3 h after the challenge, but no protection was observed after 24 h. Salmeterol did not inhibit the allergen-induced changes in total number of eosinophils and their activation markers in peripheral blood. These data suggest that a single dose of salmeterol modifies allergen-induced airway responses, above all by sustained bronchodilation.

Formic acid in the control of varroatosis: a practical approach

To evaluate the applicability of formic acid in the control of varroatosis, a trial on 55 hives was carried out during the second half of August. Into the moving base of the hive were inserted 60% formic-acid-soaked pads. The treatment was administered according to two different schedules: weekly treatment for 4 weeks, and treatment every 3 days for 2.5-3 weeks. With the first schedule, efficacy equal to 94.3% and 89.6% in 22 and 15 hives, respectively, was obtained; in eight hives treated using the second schedule, efficacy of 98.8% was obtained. As controls, 10 hives treated with Apistan were used. No adverse effects on bees were observed in the hives treated with formic acid.

[An attempt at an economic assessment of the damage caused by allergenic house dust mites]

Mites have been found to contribute to the etiology of some allergic diseases most common in Uzbekistan. The economic losses caused by atopic dust-borne asthma have been estimated. The losses due to damage to the national income, which are done by disability and to the direct and indirect expenses on treatment and disability allowance have been calculated and compared. Such an attempt is useful to calculate the profitability of prevention of domestic dust mite-caused diseases and of the mite control measures.

Herbivore-induced volatiles: the emission of acyclic homoterpenes from leaves of Phaseolus lunatus and Zea mays can be triggered by a beta-glucosidase and jasmonic acid

The treatment of healthy, undamaged plants of the Lima bean Phaseolus lunatus with solutions of a beta-glucosidase from bitter almonds (at 5 U.ml-1) through the petiole results in an enhanced emission of volatiles to the environment. The compounds are identical with those emitted in response to infestation with the red spotted spider mite Tetranychus urticae. Dominant products are the two acyclic homoterpenes 4,8-dimethyl-1,3E,7- dimethylnonatriene (homoterpene I) and 4,8,12-trimethyl-1,3E,7E,11-tridecatetraene (homoterpene II) which are of sesquiterpenoid and diterpenoid origin. Therefore, a beta-glucosidase of the herbivore may be considered as the true elicitor for the odor induction. Homoterpene I and most other of the herbivore-induced volatiles can also be triggered by treatment of the plant with solutions of jasmonic acid (JA) at 100 nmol.ml-1 to 10 mumol.ml-1. The C16 homoterpene II is not significantly induced by JA. The time-course of the enzymatic- and the JA-triggered induction of the volatiles is identical. The dose-response to JA parallels previous reports on alkaloid induction in cell cultures. In corn plants (Zea mays) JA triggers the emission of all volatiles which are known to be emitted in response to the damage by the beet army worm Spodoptora exigua. In summary, the emission of volatiles after damage by a herbivore resembles the production of phytoalexins in response to an attacking microorganism and uses similar elicitors and internal transduction pathways.

Dermatophagoides pteronyssinus II-induced interleukin-4 and interferon-gamma expression by freshly isolated lymphocytes of atopic individuals

Cytokines are known to play a major role in mediating many of the immunological and pathological features of allergic disease. Much of our understanding of cytokine production in response to allergens has come from studying allergen-specific T cell clones following long-term in vitro culture. This has largely been due to the lack of sufficiently sensitive assays to measure allergen-induced cytokine production by freshly isolated peripheral blood mononuclear cells (PBMCs). Here we have used the polymerase chain reaction to amplify reverse transcribed interleukin-4 (IL-4) and IFN gamma mRNA expressed by allergen-stimulated PBMCs from a variety atopic individuals. Using Der p II, a major allergen of the house dust mite (HDM) Dermatophagoides pteronyssinus, we have demonstrated that cells from HDM-sensitive atopic patients (n = 12), can be induced to express either IL-4 alone (three patients), IL-4 and IFN gamma (six patients), IFN gamma alone (two patients) or neither cytokine (one patient). Cells from 13 non-atopic control individuals were also stimulated with Der p II and cytokine mRNA production was studied. None expressed IL-4, while seven of 13 transcribed IFN gamma. Our results suggest that atopic individuals have allergen-reactive T cells at various stages of differentiation, with respect to the cytokines they produce. The use of this technique will aid in the further understanding of specific cellular hypersensitivity in allergic disease.

Environmental control of allergens

Allergy therapy properly consists of three possible treatment methods that can be used singly or in combination: environmental control (avoidance), pharmacotherapy, and immunotherapy. What allergens are effectively treated by environmental control? There are several broad groups of allergens with which we are concerned: indoor allergens such as dust, animal dander, molds (indoor), and cockroach; and outdoor allergens such as trees, grasses, weeds, and molds (outdoor); and, lastly, foods. The largest body of work has been collected regarding the effectiveness of indoor allergens, especially dust mites and cat. Scientifically proven measures exist for dust mites, cats, and infant formulas. Practical advice for controlling the environment for other furred animals, cockroaches, molds, and pollens are summarized. More research on effective avoidance measures for these other allergens is needed to help our patients control their environment effectively.

Home environment and childhood asthma

The prevalence of childhood asthma has increased dramatically in the past 20 years. The reasons for the increase are unclear but many authors suggest that changes in the home environment favourable to proliferation of the house dust mite are to blame. Our study aimed to compare home environment of children with asthma and controls. A questionnaire on home environment was administered to the parents of 134 children with asthma and 118 controls. Detailed studies of home temperature, humidity and dust mite allergen (DERp1) levels were performed in 20 homes (10 from each group). The questionnaire response rate was 86%. There were no significant differences between asthma and control homes with respect to social class, type of housing, smoking habits, pets, insulation, home heating, bedding, carpeting and domestic cleaning habits. A first degree family history of atopy was obtained in 42% of asthmatic families and in 16% of controls. Temperature, humidity and dust mite allergen levels were similar in both groups. The majority gave readings exceeding recommended norms. Values for DERp1 were above thresholds by a factor of 5 in 48%. Home environment does not significantly differ in children with or without asthma. The home environment is now generally mite friendly, and large segments of the childhood population are now exposed to high levels of DERp1. This may account for the increasing prevalence as more and more children with an atopic background develop overt symptoms in response to high levels of allergen load.

Airway responsiveness to allergen is increased 24 hours after exercise challenge

Although exercise is one of the most ubiquitous triggers of acute bouts of asthma, the changes in airway responsiveness before and after exercise are not well defined. Specifically, the effect of the changes in airway responsiveness induced by exercise has not been studied on subsequent allergen exposure. To test whether the reactivity to allergen is altered by preceding exercise and to define possible factors determining it, we subjected 24 children with atopic asthma to the relevant allergen challenge on two occasions: one as a control without a preceding procedure and the other 24 hours after exercise challenge. Mean postallergen maximal percent falls in forced expiratory volume in 1 second from baseline (delta FEV1) of the whole group were higher after the exercise challenge compared with those of control in both early (< 1 hour) and late (3 to 10 hours) phases. The changes of postallergen maximal delta FEV1 between the control and post-exercise allergen challenges were not related to the early bronchial response to the preceding exercise challenge. Late asthmatic responses to exercise developed in six children, and the changes in both early and late phases were significantly higher in these children, compared with those without late asthmatic responses. Furthermore, the changes were well correlated with the magnitude of the late-phase response to preceding exercise in the group as a whole. It is concluded that an increased airway responsiveness to allergen occurs 24 hours after exercise in some patients with asthma. As the changes are related to a late bronchial response to exercise, late asthmatic response to exercise, when it occurs, may be associated with increased asthmatic symptoms for as long as 24 hours after exercise.

Lack of effect of cetirizine on early and late asthmatic response after allergen challenge

BACKGROUND

Cetirizine hydrochloride has proved effective in reducing allergic symptoms and can inhibit the infiltration of eosinophils in allergic late-phase responses in the skin. Because eosinophils are likely to play an important role in allergic late-phase reactions, we studied the effect of cetirizine on early and late asthmatic reactions and on levels of eosinophil cationic protein (ECP) in the blood after allergen challenge.

METHODS

The effect of 15 mg cetirizine given twice daily was studied in 16 patients allergic to house dust mites in a double-blind, placebo-controlled study. Patients were treated for 3 weeks. Before and after treatment, bronchial challenges with house-dust mites were performed. Blood ECP levels were measured 6 hours after challenge. Methacholine provocation was performed 72 hours before and 24 hours after each challenge.

RESULTS

Early and late asthmatic response--measured as mean maximal fall in forced expiratory volume in 1 second (FEV1) and the provocative dose of allergen that causes a 15% fall in FEV1 (PD15 allergen)--were not significantly reduced after treatment with cetirizine, compared with placebo. There was also no significant effect on the concentration of methacholine, which causes a 20% fall in FEV1 (PC20 methacholine). The increase in the level of ECP in the blood after allergen challenge was reduced after cetirizine treatment, compared with placebo, but this difference was not statistically significant.

CONCLUSION

Eighteen days of treatment with cetirizine did not significantly reduce the intensity of the early and late asthmatic responses.

A population model for Dermanyssus gallinae (Acari: Dermanyssidae)

A model based on a time-varying distributed delay with attrition was developed for simulating the population dynamics of the chicken mite Dermanyssus gallinae (DeGeer, 1778). The model was parametrised according to cohort life table studies conducted under constant temperature conditions and was validated with two independent data set obtained in an experimental poultry house. The predicted mite densities and the stage-structure of the population corresponded to the values observed during experimental periods of 32, and 11 weeks, respectively. Temperature and a poultry house-specific density effect were determined to control the population development.

Optimisation of a screening procedure for house dust mite numbers in carpets and preliminary application to buildings

The relative performances of the mobility and heat escape methods for measuring house dust mite numbers in carpet has been evaluated. The optimum method was found to be the mobility method for 24 hours at ambient temperatures which exhibited a mite collection efficiency of approximately 30%. Measurements in three dwellings showed that the method should be applied to carpet at several locations in the living room and/or bedrooms as a general sampling procedure, or adjacent to loungeroom seating to determine the worst case scenario. Carpets using different types of fibre within the same dwelling should be assessed separately. For the limited number of dwellings investigated, wool carpets were found to exhibit higher mite numbers than nylon carpets, even when the former had been insect-resist treated. No house dust mites were found in the wool carpets of an office building which was mechanically ventilated and heated and achieved low indoor humidities in winter.

[The action of insect developmental regulators on the housedust mites Dermatophagoides pteronyssinus (Trouessart, 1897) and D. farinae Hughes, 1961 (Acari: Pyroglyphidae)]

Whether insect growth regulators, such as methoprene, telflubenzuron and flufenoxuron, can be used to suppress the populations of the house dust mites D. pteronyssinus and D. farinae has been studied in the laboratory setting. The most potent agent has been found to be methoprene used in concentrations of 0.05 = 0.1%, in particular. Flufenoxuron at a concentration of < 0.1% has been shown to stimulate the reproduction of house dust mites.

Bronchial responsiveness is not always increased after allergen challenge

Increased bronchial responsiveness has been reported at various time points following allergen challenge (AC), and may be related to the magnitude of the late response (LAR). We have studied 20 mild asthmatics, who were known to develop a late asthmatic response to inhalation of house dust mite extract (fall of > 15% from post-diluent baseline FEV1 from 2 to 7h after AC). The provocation concentration of methacholine causing a 20% fall in FEV1 (PC20 FEV1) was measured before and 24 h after challenge with house dust mite extract (HDM). The mean (SEM) change in log(PC20) was 0.08 (0.09) mg ml-1, and was not significant (P = 0.38; paired t-test). The change in PC20 for each subject was not significantly correlated with the size of LAR (r = -0.33; P > 0.05), but was significantly correlated with the absolute change from baseline FEV1 at 24 h (r = 0.67; P < 0.01). Our subjects had a high baseline responsiveness, when compared with previous studies. We suggest they may have been approaching a maximally responsive state prior to study, and allergen challenge may have had little effect in further increasing responsiveness. Exposure to allergen in late responders is not necessarily followed by an increase in non-specific bronchial responsiveness.

Effective allergen avoidance at high altitude reduces allergen-induced bronchial hyperresponsiveness

We studied the effects of reduced allergen exposure on bronchial hypereactivity (BHR) in two groups of asthmatic children allergic to house dust mites (HDM) living at high altitude for 9 continuous mo. In the first group the serum levels of total and HDM-specific IgE showed significant decreases after 3 mo (p < 0.001 and p < 0.02, respectively) and after 9 mo (p < 0.001). Three months after returning home the total IgE levels had increased significantly (p < 0.001). The mean percentage fall in peak expiratory flow after exercise testing improved after 3 and 9 mo (p < 0.05), but it had deteriorated after 3 mo at home (p < 0.01). The methacholine PD20-FEV1 increased after 3 mo (p = 0.001) and further after 9 mo (p < 0.001), with a decrease after the 3-mo period at sea level (p = 0.01). In the second cohort there was a significant increase in HDM PD20-FEV1 after 6 and 9 mo (p < 0.001), with a slight decrease of magnitude of the allergen-induced late reaction. Histamine PD20-FEV1 significantly increased after 6 and 9 mo at high altitude, particularly in the challenges performed after the HDM bronchial provocation (p < 0.01). Our data demonstrate that allergen avoidance in asthmatic children not only decreases nonspecific BHR but also decreases allergen sensitivity, late allergen-induced bronchial reactions, and enhancement of BHR by allergen challenge.

Humidity regulation in the management of asthma patients sensitized to house dust mites

Substances in the faeces of house dust mites are well-recognized as common allergens in the pathogenesis of asthma. There have been many trials of interventions aimed at reducing mite populations in the home, but most have been uncontrolled, too small, or too short to determine with confidence any beneficial effects. Of those which succeeded, very few used methods which reduced mite populations on a permanent basis. House dust mites are sensitive to humidity. Their geographical distribution is closely correlated to the availability of moisture. Very little work has been done on the effects of reducing humidity in the home environment in the long term, with a view to controlling dust mite populations. Two different methods which might reduce humidities to levels which could successfully reduce dust mite numbers are dehumidifiers, and mechanical ventilation with heat recovery (MVHR). To date there has been no work assessing the effectiveness of dehumidifiers and very little (although promising) work on MVHR. We discuss the potential of humidity control as an adjunct to the clinical treatment of asthma.