House Dust Mites: Natural History, Control and Research Techniques

By Rob de Boer

House Dust Mites: Natural History, Control, and Research Techniques presents a complete synthesis of biological information on dust mites from both an ecological and evolutionary perspective. This book allows readers to consume current knowledge on house dust mite biology as well as methods and techniques to conduct personal research. Written by an expert on house dust mite biological research, this book begins with an explanation of the medical importance of understanding dust mites due to their human health repercussions, including asthma and bronchial hyperresponsiveness. It discusses various species, exposure effects, best practices for habitat reduction and preventative options.

The book then goes on to detail the house dust mite’s biology and behavior, such as food and nutrition, water intake, reproduction, colonization and preferred climates. This is an ideal resource for entomologists and acarologists, as well as medical professionals seeking knowledge on insect-borne allergens.

• Discusses house dust mites’ roles in indoor air quality and allergic asthma
• Details the lifecycle and behavior of house dust mites to understand their occurrence or continued presence
• Offers proven control methods such as lethal heat and cold treatments

• Language: English
• Publisher: Academic Press
• Release date: Mar 13, 2023
• ISBN: 9780443152245

Rob de Boer

Rob de Boer is an entomological researcher and retired professor from the University of Amsterdam. He received his PhD in Entomology from the University of Amsterdam and went on to lead research in the Hugo de Vries Laboratorium, the Laboratory of Experimental Entomology, and the Laboratory of Molecular Biology. His research expertise is in acarology (spider mites, ticks, dust mites) and bacteriology, specifically Lyme disease. He has published numerous scholarly articles on these topics.

Book preview

9780443152245_FC

House Dust Mites

Natural History, Control, and Research Techniques

First Edition

Rob de Boer

fm01-9780443191114

Table of Contents

Cover image

Title page

Copyright

Dedication

Preface

Acknowledgments

Chapter One: An introductory note on the medical significance of dust mites

Abstract

1.1: Discoveries

1.2: Identification and quantification

1.3: Exposure to mite allergens and disease

1.4: BHR, FEV, and PC-20

1.5: Secondary prevention: Yes, primary prevention: No

References

Chapter Two: Mites and the science of acarology

Abstract

2.1: Dermatophagoides as an example of a mite

2.2: Sampling houses for dust mites and setting up cultures

References

Chapter Three: House dust faunas around the world

Abstract

References

Chapter Four: Water junks

Abstract

4.1: Food and metabolic water

4.2: The critical equilibrium (air)humidity (CEH)

4.3: The speed of water vapor uptake and loss

4.4: The conservation of body water, excretion of nitrogenous waste, and water loss tolerance

4.5: Two strategies for dealing with drought spells: D. pteronyssinus vs D. farinae

References

Chapter Five: Surveys of the occurrence of dust mites and their allergens

Abstract

5.1: Associations with home characteristics

5.2: Density-dependent and density-independent factors

5.3: Are there any houses without mites?

5.4: Utility buildings and public places

References

Chapter Six: Where do mites survive the winter in a temperate climate?

Abstract

6.1: Mattresses

6.2: Carpeted floors and rugs

6.3: Lethal heat and cold treatments

6.4: Mite control through reduction of RH, air-conditioning, mechanical ventilation, dehumidifiers, electric blankets, subfloor heating

References

Chapter Seven: The life cycle of astigmatic mites and their natural habitats

Abstract

7.1: Hypopi

7.2: The natural habitats and colonization

7.3: Dispersal of domestic house dust mites

7.4: The sex ratio

7.5: Males, females, copulation, and egg production

7.6: The subadult stages of Dermatophagoides

References

Chapter Eight: Modeled population dynamics

Abstract

8.1: Population development in circumstances with constant optimum physical conditions and with unlimited access to food

8.2: A speculative appraisal of empirical findings

8.3: A density-dependent factor, namely: Food

8.4: Kill them all in winter?

References

Chapter Nine: What can dust mites eat?

Abstract

9.1: Dander

9.2: Food dynamics

9.3: Fungi and bacteria

9.4: Could humidity influence the food supply?

References

Chapter Ten: Investigations waiting to be done

Abstract

Reference

Appendix A

The benefits of taking three samples instead of just one

Reference

Appendix B

References

Appendix C

Calculation of absolute humidity (AH) from readings of relative humidity (RH) and temperature (T)

Reference

Appendix D

Determination of the CEH

References

Appendix E

Mites and animal nests

References

Appendix F

Intrinsic rate of increase and population structure

References

Appendix G

Dynamic modeling: STELLA

Appendix H

The binomial distribution, the poisson distribution, confidence intervals, and a dreamed sampling procedure

Index

Copyright

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This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices

Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.

Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.

To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.

ISBN 978-0-443-19111-4

For information on all Academic Press publications visit our website at https://www.elsevier.com/books-and-journals

fm01-9780443191114

Publisher: Nikki P. Levy

Acquisitions Editor: Kelsey Connors

Editorial Project Manager: Anthony Marvullo

Production Project Manager: Omer Mukthar

Cover Design: Fanny de Boer and Vicky Pearson Esser

Typeset by STRAIVE, India

Dedication

For Winnie, Cuno, and Fanny

Preface

During the years 1975 until 2000, I was, with interruptions, employed by the University of Amsterdam. My workstation was the Laboratory of Experimental Entomology. The laboratory has been renamed several times, but the word acarology never formed part of the name. Yet most of the research going on there concerned mites. I worked on spider mites, ticks, and, during the years 1987 through 2000, on house dust mites. For my employment I depended on financial support from external funding organizations. Satisfying the demands of these organizations had priority of course. There was little time to go into interesting sideways or delve into underlying, more theoretical questions. Eventually lack of funds forced me to stop working on dust mites. But the fascination was still there. Through the scientific literature I had meticulously followed the ongoing research on dust mites and I felt the need to organize and summarize the overwhelming accumulation of information and to clarify topics that are not so easy to understand. Not before my retirement in 2012, I found time for an attempt to do that. It was only an attempt but, I believe, not a complete failure. In fact I was quite content with it myself.

Explaining something to someone else is often the best way to test whether you really understand it yourself. I had nobody. But an anonymous reader is a rather satisfactory alternative. So I wrote this book primarily for myself. But who else could benefit?

Dust mites are important for human health, albeit in a negative way. That is why they received much attention of acarologists. It is quite rare that so much research has been done and so much information has accumulated concerning one single animal species. Mites are tiny organisms, living without glamour, but living. Mites in general never received much attention of the general public. In fact they are quite obscure creatures for most people. Yet they have some remarkable, even unique, properties interesting for anyone with an interest in natural history. I tried to write a text that is understandable for everybody: outsiders as well as insiders. Medical professionals and the allergy patients themselves may wish to know some more about these secretive creatures that constitute a serious health hazard. Also undergraduate biology students who wish to learn more about mites could benefit. But above all, this is what I had in mind as a reader: an acarologist, either familiar or not familiar with the subject, who I try to convince of the need to perform certain investigations on house dust mites.

Acknowledgments

The Netherlands Asthma Foundation (NAF), now called Het Longfonds, supported my research financially during the years 1980–90, allowing me to extend my knowledge on house dust mite biology. All the time I highly appreciated the help, both technical and intellectual, of my friend Kees Kuller. During the years when I was writing, my wife Winnie bore the brunt of my absentmindedness, my son, Cuno, again and again helped me out when I was stuck in a software predicament and my daughter, Fanny, made invaluable contributions to many of the illustrations of the book. Scans of illustrations originating from published articles were always readily provided by staff members of the Naturalis library in Leiden.

I alone, of course, am responsible for errors, omissions, and other shortcomings.

Chapter One: An introductory note on the medical significance of dust mites

Abstract

The chronology is described of events and discoveries leading to the recognition of house dust mites as a major source of inhalant allergens in indoor air. An early written record linking asthma attacks to inhaling house dust dates back from 1662. In 1928 Hermann Dekker, a German physician, suggested a connection with mites. The reality of this connection was convincingly demonstrated by Frits Spieksma in 1967. Immunochemical identification of the allergens soon followed. Trials to demonstrate health benefits from avoiding exposure to these allergens were sometimes but not always successful.

Keywords

Asthma; Sensitization; Bronchial hyperreactivity (BHR); Secondary prevention; Der p1; Der f1; Guanine; Acarex test

1.1: Discoveries

It has often been said that Frits Spieksma discovered the house dust mite. That is not exactly true. How could it be? Formally the European house dust mite is called Dermatophagoides pteronyssinus (Trouessart, 1897). That means that this mite was described as a distinct species in 1897 by an acarologist called Trouessart before Spieksma was born (in 1936). It had been known for a long time that asthma attacks can be triggered in susceptible people when they inhale air that is somehow contaminated with house dust, for instance during house cleaning activities. Sweeping causes choking (Kern, 1921). The Flemish physician John Baptista Van Helmont (1662) may have been the first to mention the connection between asthma attacks and exposure to dust. He described the case of a monk who fell short of breath any time a place was swept or dust was stirred up by any other means.

Skin tests (Fig. 1.1) were done at least since 1917 (Walker, 1917). Asthmatic people show a positive skin reaction to extracts of house dust far more often than nonasthmatics. Some constituent of house dust acts as an allergen in these people. In 1928, Dekker (1928), a German physician, published an article in which he suggested that mites could be the source of this allergen. Skin tests can be deployed to determine the presence of an allergen in an extract in a semiquantitative way. A higher concentration of the allergen will result in a stronger skin reaction as can be judged by the size and appearance of the weal (Fig. 1.1). Spieksma, working in Leiden, The Netherlands, set up cultures of Dermatophagoides pteronyssinus and prepared extracts of these mites. Skin tests on susceptible and nonsusceptible individuals using these extracts besides house dust extracts from various sources strongly pointed to the mites as the source of the allergen. The experiments were described in Spieksma’s dissertation (1967) and also in a book by Voorhorst et al. (1969). The book was epoch making. It spurred a host of medical studies as well as biological research on this mite—a mite species that was hardly noticed before.

Fig. 1.1

Fig. 1.1 Skin prick test. (Photo: Shutterstock.com.)

I suspect that today among medical professionals the prevailing notion is that, by now, we must know everything there is to be known about these simple creatures. The truth is that we do not fully understand why some houses have a thriving mite population, whereas quite similar dwellings in the same neighborhood are almost devoid of mites and mite allergens.

1.2: Identification and quantification

Dust mites turned out to be abundant in almost every human dwelling. Spieksma (1967) found it astonishing that this had always escaped the attention of investigators. Soon after the publication of the book by Voorhorst, Spieksma, and Varekamp a great number of epidemiological studies were initiated. These studies focused on the link between allergy symptoms and the abundance of mites in houses. Among the earliest studies were those by Jens Korsgaard, a lung physician working in Aarhus, Denmark. He found that the number of mites in dust from the houses of 25 patients with newly diagnosed asthma was much greater than in the homes of 75 randomly selected matched control subjects (Korsgaard, 1983). Besides D. pteronyssinus two or three other species of mites were very common in house dust from all over the world. In particular Dermatophagoides farinae, the so-called American house dust mite, was quite common and, despite its name, not only in America. Korsgaard took the number of mites per gram of vacuumed dust as a measure of exposure to mite allergens. The allergens themselves were not yet identified. But that was only a matter of time. Later investigators often took the concentration of Der p 1 + Der f 1 per gram of dust as a measure of exposure. Der p 1 and Der f 1 are proteins in the feces of D. pteronyssinus and D. farinae, respectively, and regarded as major house dust mite allergens (Table 1.1). These proteins are digestion enzymes. Actually it is surprising that these proteins emerged as inhalation allergens because the fecal pellets of dust mites are relatively large, much larger than, for instance, the particles carrying the allergens of cats and dogs. Vigorous disturbance of dust collectors like carpets, rugs, stuffed furniture, and mattresses is necessary to render the mite feces airborne in the first place and then the fecal pellets will rather quickly fall back to the ground. This was confirmed by studies in which airborne sampling was done (for instance, Swanson and Agarwa, 1985; Swanson et al., 1989, Custovic et al., 1995). Thus the exposure to dust mite allergens probably occurs erratically, in brief episodes with high concentrations in the inhaled air.

Table 1.1

From Stewart, G.A., Thompson, P.J., 1996. The biochemistry of common aeroallergens. Clin. Exp. Allergy 26, 1020–1044.

From a medical point of view, airborne sampling provides the most relevant measure of allergen exposure, i.e. the amount of allergen that is inhaled by the inhabitants of a house during the day and during the night. But sampling air for an extended period is tedious. A more practical sampling method would be highly desirable. Therefore the amount of allergen per gram of vacuumed dust has been chosen as the preferred measure of allergen exposure. There must be a correlation between the concentration of allergen in house dust and the amount of allergen in the air following a disturbance of settled dust. Of course this is a compromise between the most desirable and the most practical of sampling procedures. Imagine, for instance, that the inhabitants of a house come home from a visit to the beach and bring in sand on their clothes which mixes with the floor dust. The concentration of allergen per gram of vacuumed material will then be drastically changed by the presence of the heavy sand grains. But these grains will not have any effect on the amount of allergen in the air. Nevertheless, it is assumed that, in general, the concentration of allergen in settled dust provides a reasonably good indication of the burden of allergen exposure.

Mite feces also contain a lot of guanine, a metabolic waste product. As expected, there is a strong correlation between the concentration of guanine and the concentration of mite allergens. A semiquantitative test for guanine content of house dust, the Acarex test, can be used, even by lay people, to obtain an indication of the allergen burden in their homes (see Fig. 1.3).

1.3: Exposure to mite allergens and disease

The abovementioned study by Korsgaard already showed a connection between the number of mites in house dust and allergy symptoms. As soon as immunoassays for the detection and quantification mite allergens had been developed, investigators no longer determined the number of mites. Instead the concentration of the mite allergens Der p 1 or the sum of Der p 1 + Der f 1 was taken as a measure of allergen exposure. Examples are the study by Sporik et al. (1990) in southern England and the study by Vervloet et al. (1991) in southern France. Vervloet and his cooperators studied 49 asthmatic subjects attending an outpatient clinic in Marseille in 1987/1988. These were subdivided into three groups on the basis of their medication requirements, which of course reflects the severity of their symptoms. It was found that patients with the severest symptoms generally had the highest concentration of house dust mite allergens in the dust from their mattresses (Fig. 1.4). Sporik et al. (1990) studied some 70 newborn children of which one parent had either asthma or hay fever and therefore had an increased chance of becoming atopic also. The children were followed until age 11. One of the findings was that asthma symptoms started at an earlier age when the child lived in a home where allergen levels were high (P < .015). Also, in a tropical country like Zambia, asthma is very common and asthmatics were found to be sensitized for house dust mite allergens much more often than healthy control subjects (Buchanan and Jones, 1972).

In the temperate climatic regions, dust mites and their allergens rise to a peak in the autumn and then fall again during the winter. And indeed an aggravation of respiratory symptoms is observed during the autumn (Heide et al., 1997). Circumstantial evidence indicates that this worsening of symptoms is directly caused by the increased exposure to allergens and not to some other environmental change that is associated with the season.

Findings such as those outlined before suggest that it is desirable and useful to take measures aiming to avoid exposure to mite allergens. Zero exposure is not realistic. All places where people go are contaminated to some degree. Allergens are transported on the clothes of people and spread all over. Even brand new carpets and mattresses have been found to contain measurable quantities of mite allergen (van der Hoeven et al., 1992; de Boer, 2002). The question is: What is the highest concentration of allergens in house dust that can be regarded as harmless? Or can even the lowest concentration do some harm? In order to address this and other questions, several international expert meetings were organized during the years 1970–80. At one of these meetings (Platts-Mills et al., 1991, 1992) the consensus was reached that:

(1)the threshold level for sensitization is:

2 μg Der p 1 + Der f 1 per gram of dust or 100 mites per gram of dust.

and

(2)the threshold level for acute asthma attacks is:

10 μg Der p 1 + Der f 1 per gram of dust or 500 mites per gram of dust.

However, indications have been found that even levels below 2 μg/g of dust can be sufficient to induce sensitization (Peat et al., 1993; Munir et al., 1993).

1.4: BHR, FEV, and PC-20

Inhaling