**1. Introduction**

The dust mites usually refer to those species of the mite family Pyroglyphidae that are known to commonly occur widely, although sometimes regionally, in the dust of human dwellings. Dust mites sometimes called dirt mites or bed mites are microscopic creatures, measuring only about one-quarter to one-third of a millimeter (250–300 microns) in length; females weigh about 5.8 μg, while males are approximately half of this weight as 3.5 μg. Nearly 72–74% of their total weight is water and they have translucent bodies with a striated cuticle. They are not insects but arthropods like spiders and ticks having eight legs, no eyes and antennae, and bear mouthpart set in front of the body [1]. Dust mites can live in mattresses, bedding, upholstered furniture, carpets, curtains and other places in homes.

Each adult person sheds about one and a half grams of skin every day. This is enough to feed one million dust mites. Dust mites are microscopic creatures that can live in bedding and carpets, and feed on this skin. They feed on flakes of dead skin or skin cells and scales commonly called dander that are shed by people and pets. They like to live indoors, where they can get plenty of food like mold spores and dead skin cells from people and pets. They cannot survive in colder and drier places, however in a warm and humid house, dust mites can survive all the year around. Dust mites thrive in temperatures of 68–77°F (20–25°C) and they also like humidity levels of 70–80% [2].

These tiny individuals (**Figure 1**) are a big source of allergens and can worsen allergies and asthma. An allergen is a substance that causes an allergic reaction. Both the body parts and the waste of dust mites are allergens for many people. Most dust mites die in low humidity level (when the humidity falls below 50%) or extreme temperature, but they leave their dead bodies and waste behind to cause allergic reactions [3].

The house dust mite species of family Pyroglyphidae, commonly occurring in dust of human dwellings, belong to six genera, the so-called *Dermatophagoides*, *Euroglyphus*, *Hirstia*, *Malayoglyphus*, *Pyroglyphus* and *Sturnophagoides*. In total, 13 species have been found in house dust and recorded from different locations throughout the world, including the United States, Hawaii, Canada, Europe, Asia, the Middle East, parts of Australia, South America, and Africa (**Table 1**).

Related species of *Dermatophagoides* have the most worldwide occurrence and are very similar, but bear differences in some physical characteristics, for example, in male ventral posterior idiosoma and the aedeagus, and in female genital opening and bursa copulatrix [4]. Additional mites occurring in house dust are the glistening mites (family Tarsonemidae), storage mites (families Acaridae, Glycyphagidae and Chortoglyphidae) and the predatory mites (family Cheyletidae); however these groups will not be examined in depth in this chapter.

Mites of family Tarsonemidae have modified legs IV (reduced, enlarged with a single tarsal claw on male, setiform on female); body with series of overlapping plates; and gnathosoma cone-like, enclosing minute palps and chelicerae. When mites are not as mentioned above, they may be with striated cuticle (family

**273**

abdomen end [14].

**Table 1.**

*Bronswijk [18] and Colloff [5]).*

mites and their allergens in homes.

**2. Family Pyroglyphidae Cunliffe 1958 acarofauna**

*House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination*

4 *D. halterophilus* Spain, Singapore, tropical regions 5 *D. pteronyssinus* Commonly all over Europe

8 *Euroglyphus maynei* Humid geographic areas all over the world

1 *Dermatophagoides farinae* Commonly in the United States, not the United Kingdom

Pyroglyphidae), otherwise with smooth or papular cuticle, long serrated dorsal setae, and legs with long slim tarsi (family Glycyphagidae). Setae sci and sce are about the same length, and tegmen present in genus *Euroglyphus*, but setae sce considerably shorter than sci, and tegmen absent in *Dermatophagoides* of family Pyroglyphidae [5]. An accurate taxonomic documentation of house dust mites is very vital, simply not from a biological standpoint but about the significances of their corresponding allergenic properties as well. Numerous works on immunochemical have exposed variances among the two products hard to differentiate sibling species [6–13]. An introductory practical taxonomic identification for the most common and important house dust mites is presented at this stage. The main species, identified as *Dermatophagoides farinae* Hughes (American house dust mite), *Dermatophagoides microceras* Griffiths and Cunnington, *Dermatophagoides pteronyssinus* (Trouessart) (European house dust mite), *Euroglyphus maynei* (Cooreman) (Mayne's house dust mite), *Dermatophagoides evansi* Fain and *Euroglyphus longior* (Trouessart), are

*Various species of family Pyroglyphidae existing in house dust and their locations recorded (reproduced from* 

10 *Hirstia domicola* United States, Canada, Europe, Asia, Middle East, parts of

12 *M. intermedius* United States, Canada, Europe, Asia, Middle East, parts of

Australia, South Africa

Australia, South Africa

discussed here. However, three *Dermatophagoides* species, *D. pteronyssinus*,

*D. farinae* and *E. maynei*, are the most common, comprising up to 90% of the house dust mite fauna of the world. Morphologically, the most conspicuous difference in these *Dermatophagoides* species is that there are no four long train hairs on the

Many aspects on the biology of house dust mites are not understood; therefore, a greater understanding of their biology may reveal new strategies for controlling of

Pyroglyphidae belongs to the order Astigmata of the subclass Acari (also known as Acarina). The order Astigmata is differentiated from other orders of Acari by

*DOI: http://dx.doi.org/10.5772/intechopen.91891*

**S. No. Species Locations**

3 *D. microceras* Europe

6 *D. siboney* Cuba

7 *D. neotropicalis* Tropical areas

11 *Malayoglyphus carmelitus* Israel, Spain

13 *Pyroglyphus africanus* South America

14 *Sturnophagoides brasiliensis* Brazil, France, Singapore

9 *E. longior* Holarctic, Neotropic

2 *D. evansi* Europe, North America

**Figure 1.** *House dust mites.*


*House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination DOI: http://dx.doi.org/10.5772/intechopen.91891*

#### **Table 1.**

*Parasitology and Microbiology Research*

levels of 70–80% [2].

reactions [3].

dust of human dwellings. Dust mites sometimes called dirt mites or bed mites are microscopic creatures, measuring only about one-quarter to one-third of a millimeter (250–300 microns) in length; females weigh about 5.8 μg, while males are approximately half of this weight as 3.5 μg. Nearly 72–74% of their total weight is water and they have translucent bodies with a striated cuticle. They are not insects but arthropods like spiders and ticks having eight legs, no eyes and antennae, and bear mouthpart set in front of the body [1]. Dust mites can live in mattresses, bed-

Each adult person sheds about one and a half grams of skin every day. This is enough to feed one million dust mites. Dust mites are microscopic creatures that can live in bedding and carpets, and feed on this skin. They feed on flakes of dead skin or skin cells and scales commonly called dander that are shed by people and pets. They like to live indoors, where they can get plenty of food like mold spores and dead skin cells from people and pets. They cannot survive in colder and drier places, however in a warm and humid house, dust mites can survive all the year around. Dust mites thrive in temperatures of 68–77°F (20–25°C) and they also like humidity

These tiny individuals (**Figure 1**) are a big source of allergens and can worsen allergies and asthma. An allergen is a substance that causes an allergic reaction. Both the body parts and the waste of dust mites are allergens for many people. Most dust mites die in low humidity level (when the humidity falls below 50%) or extreme temperature, but they leave their dead bodies and waste behind to cause allergic

The house dust mite species of family Pyroglyphidae, commonly occurring in dust of human dwellings, belong to six genera, the so-called *Dermatophagoides*, *Euroglyphus*, *Hirstia*, *Malayoglyphus*, *Pyroglyphus* and *Sturnophagoides*. In total, 13 species have been found in house dust and recorded from different locations throughout the world, including the United States, Hawaii, Canada, Europe, Asia,

Related species of *Dermatophagoides* have the most worldwide occurrence and are very similar, but bear differences in some physical characteristics, for example, in male ventral posterior idiosoma and the aedeagus, and in female genital opening and bursa copulatrix [4]. Additional mites occurring in house dust are the glistening mites (family Tarsonemidae), storage mites (families Acaridae, Glycyphagidae and Chortoglyphidae) and the predatory mites (family Cheyletidae); however these

Mites of family Tarsonemidae have modified legs IV (reduced, enlarged with a single tarsal claw on male, setiform on female); body with series of overlapping plates; and gnathosoma cone-like, enclosing minute palps and chelicerae. When mites are not as mentioned above, they may be with striated cuticle (family

the Middle East, parts of Australia, South America, and Africa (**Table 1**).

groups will not be examined in depth in this chapter.

ding, upholstered furniture, carpets, curtains and other places in homes.

**272**

**Figure 1.** *House dust mites.* *Various species of family Pyroglyphidae existing in house dust and their locations recorded (reproduced from Bronswijk [18] and Colloff [5]).*

Pyroglyphidae), otherwise with smooth or papular cuticle, long serrated dorsal setae, and legs with long slim tarsi (family Glycyphagidae). Setae sci and sce are about the same length, and tegmen present in genus *Euroglyphus*, but setae sce considerably shorter than sci, and tegmen absent in *Dermatophagoides* of family Pyroglyphidae [5].

An accurate taxonomic documentation of house dust mites is very vital, simply not from a biological standpoint but about the significances of their corresponding allergenic properties as well. Numerous works on immunochemical have exposed variances among the two products hard to differentiate sibling species [6–13]. An introductory practical taxonomic identification for the most common and important house dust mites is presented at this stage. The main species, identified as *Dermatophagoides farinae* Hughes (American house dust mite), *Dermatophagoides microceras* Griffiths and Cunnington, *Dermatophagoides pteronyssinus* (Trouessart) (European house dust mite), *Euroglyphus maynei* (Cooreman) (Mayne's house dust mite), *Dermatophagoides evansi* Fain and *Euroglyphus longior* (Trouessart), are discussed here. However, three *Dermatophagoides* species, *D. pteronyssinus*, *D. farinae* and *E. maynei*, are the most common, comprising up to 90% of the house dust mite fauna of the world. Morphologically, the most conspicuous difference in these *Dermatophagoides* species is that there are no four long train hairs on the abdomen end [14].

Many aspects on the biology of house dust mites are not understood; therefore, a greater understanding of their biology may reveal new strategies for controlling of mites and their allergens in homes.

#### **2. Family Pyroglyphidae Cunliffe 1958 acarofauna**

Pyroglyphidae belongs to the order Astigmata of the subclass Acari (also known as Acarina). The order Astigmata is differentiated from other orders of Acari by

the lack of stigmata on idiosoma. This order is furthermore categorized into two suborders, the Acaridia that includes free-living mites and the Psoroptidia which comprises mites parasitic in nature. The former suborder is divided into many families, including the Pyroglyphidae, to which house dust mites belong. Pyroglyphidae are minute mites (full grown adults 170–500 μm in length), cuticle excellently or crudely wrinkle, tarsi termination in a circular pulvillus and a minute claw, anus ventral in position, vestigial genital structures present in both sexual category, vulva of female reverse Y or V fashioned, oil glands existing and exposed among L2 and L3, and vertical setae lacking [15].

Pyroglyphidae is a family of nonparasitic mites, wherein a great variety of species has been observed. It includes the house dust mites that live in human dwellings, many species that live in the burrows of other animals, and some are pests of dried products stored in humid conditions. The family Pyroglyphidae contains mainly species of astigmatid mites that live in the nests of birds and mammals, where they feed on the epidermal detritus (skin, feathers) left by the host, and occurs worldwide [16].

Among the genera of the family Pyroglyphidae, the most outstanding are *Dermatophagoides* and *Euroglyphus*. Three species, *D. farinae*, *D. pteronyssinus*, and *Euroglyphus maynei*, are commonly found in homes of humans and mostly prevalent in high-use areas, where shed skin scales are collected and serve as their food. House dust mites, mostly of the genus *Dermatophagoides*, is important medically and although *D*. *pteronyssinus* and *D*. *farinae* are known as the European and American dust mites, both of these are found worldwide. Both mites *D. farinae* and *D. pteronyssinus* move steadily and slowly; however walk quickly without altering way at whatever time they are opened to an extreme light or heat. In contrary, *E. longior* and *B. evansi* express a negative phototropic response when exposed to an electric lamp of bright light [17].

The presence of house dust mites can be confirmed microscopically, which requires collecting samples from mattresses, couches, or carpets. Also, in general practice, it takes at least a 10X magnification to be able to correctly identify them. A modified Berlese funnel is commonly used for extraction of mites from stored grain and has also been successfully used for extraction of *E. longior* and *D. evansi*; however, *D. farinae* cannot be extracted from the dust in this way. A simple method to extract most house dust mites, mite fragments and debris is as follows: weigh 0.1 g of dust from the vacuum cleaner bag, filter by 0.5 and 0.125 mm mesh sieves, relocate dust on 0.125 mm sieve to a lookout glass, moist it with alcohol or ether, whirl suspension to spread out dust uniformly, let the solvent to vaporize, calculate the number of mites below a stereomicroscope, and accumulate them with a camel's hair short-bristled brush. Mites removed through these procedures can be wellmaintained in 85% alcohol for an indefinite period. Short-term mounts of mites can be done in lactic acid, glycerin, mineral oil, phenol, etc. A comparatively longlasting mounting medium is Hoyer's modified Berlese solution ringed with Canada balsam, glycerol, or glyptol. Proof of specimen identity can be done underneath a phase or interference contract microscope only [18].

Three species, *E. maynei*, *D. pteronyssinus*, and *D. farinae*, are usually observed in home environment of humans. Within homes, these mite species are at peak prevailing in high-use parts, wherever shed skin scales accumulate and assist as their diet. Hence, their highest masses are set up in carpets, nearby easy chairs and sofas, in mattresses, and in fabric-covered overstuffed furniture. But, they may also be found on clothing, in bedding, on pillows, on train and automobile seats, and from time to time in workplaces and schools. Every species is the basis of several potent allergens, which in predisposed people trigger and sensitize allergic reactions. These allergens are cause of asthma, atopic dermatitis and perennial rhinitis [19].

**275**

*House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination*

Dust mites are most closely related to spiders and ticks. These mites are about 25–30 millimeters in size and cannot be seen without magnification. The translucent body of a house dust mite is 300–400 μm in length and only visible under a microscope. They have eight hairy legs, a mouth-like appendage in front of the body, a tough shell and no eyes or antennae. The lifetime stages of the dust mites are eggs, larvae, protonymphs, deutonymphs, tritonymphs, and adult males and females. The duration of life cycle is dependent on temperature while relative humidity (RH) is beyond 60%. At 23°C, life cycle proceeds 36 and 34 days for *D. pteronyssinus* and *D. farinae*, respectively, to be completed. Females at 23°C create 2 or 3 eggs every day during the reproductive history. At 35 and 16°C, mite *D. pteronyssinus* ensues 15 and 23 days for complete development, respectively; however. *D. farinae* does not grow well at 35 and 16°C. A desiccation-resistant inactive protonymphal stage can occur which permits persistence during lengthy times (months) in dry (less relative humidity) environment. As soon as relative humidity circumstances turn out to be optimum, the dormancy is finished and growth

The female lays eggs singly or in small groups. The adult mated female can lay 40–80 eggs in its lifetime. When the egg hatches, a six-legged larva emerges. There are two nymphal stages that feed and molt before an eight-legged adult is developed. Transition from egg to adult takes about 3–4 weeks. The duration of the cycle is usually 1 month but is dependent on the climate, however 25°C and 75% relative humidity are ideal. An adult house dust mite can live for 1–3 months under favorable conditions. Normally, adult dust mites live for about a month and female dust mites live for about 8–10 weeks. It is estimated that the house dust mite can produce 20 fecal pellets/day that range from 20 to 50 μm. House dust mites are ~75% water by weight and therefore need to absorb water from the water vapor in the air, mak-

The population of *Dermatophagoides* species has been observed in hospital halls, non-carpeted patient's rooms, and carpeted patient's rooms through vacuuming of floor in winter and summer periods. As a summer control set, bedrooms in homes of workers have been checked out. Out of 141 total dust samples obtained, *D. pteronyssinus* or *D. farinae* have not been found in 60 hospital dust samples that are acquired during winter period. Even though mites have been originated in certain sites in hospital during summer dust assemblage, mite population in these localities and mean mite population for entirely samples persisted insignificant. For the period of summer dust sampling taken from bedroom carpets of altogether worker houses checked out observed positive for mites, with a number of homes having high or moderate densities (ranged 22–8340 mites/g of dirt). Prevalence of dust mite in a hospital might be retained very little even if in worker homes, mite levels are found moderate to high. The reasons accountable for little mite populations in hospital are the usage of low-pile carpets, keeping low relative humidity, and

The house dust mites *D. farinae* and *D. pteronyssinus* are cosmopolitan inhabitants of human dwellings. They are most prevalent in high-use areas in homes (e.g., beds, furniture, floors), where shed human skin scales are collected and serve as a source of food. Relative humidity is an important factor regulating the geographic prevalence and density of these mites. In humid geographic areas, most homes contain mite populations, whereas in dry (low-humidity) geographic areas, few homes contain mites. The species prevalence and density of these mites varies both geographically and between homes in the same geographic area. Although factors influencing variations in mite density between homes are not well understood, it appears that mite density is not correlated with housecleaning practices. However, carpeted floors support significantly greater mite populations than do wood or

*DOI: http://dx.doi.org/10.5772/intechopen.91891*

ing relative humidity a critical factor for survival.

upright laundering and housekeeping practices [21].

carries on [20].

#### *House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination DOI: http://dx.doi.org/10.5772/intechopen.91891*

Dust mites are most closely related to spiders and ticks. These mites are about 25–30 millimeters in size and cannot be seen without magnification. The translucent body of a house dust mite is 300–400 μm in length and only visible under a microscope. They have eight hairy legs, a mouth-like appendage in front of the body, a tough shell and no eyes or antennae. The lifetime stages of the dust mites are eggs, larvae, protonymphs, deutonymphs, tritonymphs, and adult males and females. The duration of life cycle is dependent on temperature while relative humidity (RH) is beyond 60%. At 23°C, life cycle proceeds 36 and 34 days for *D. pteronyssinus* and *D. farinae*, respectively, to be completed. Females at 23°C create 2 or 3 eggs every day during the reproductive history. At 35 and 16°C, mite *D. pteronyssinus* ensues 15 and 23 days for complete development, respectively; however. *D. farinae* does not grow well at 35 and 16°C. A desiccation-resistant inactive protonymphal stage can occur which permits persistence during lengthy times (months) in dry (less relative humidity) environment. As soon as relative humidity circumstances turn out to be optimum, the dormancy is finished and growth carries on [20].

The female lays eggs singly or in small groups. The adult mated female can lay 40–80 eggs in its lifetime. When the egg hatches, a six-legged larva emerges. There are two nymphal stages that feed and molt before an eight-legged adult is developed. Transition from egg to adult takes about 3–4 weeks. The duration of the cycle is usually 1 month but is dependent on the climate, however 25°C and 75% relative humidity are ideal. An adult house dust mite can live for 1–3 months under favorable conditions. Normally, adult dust mites live for about a month and female dust mites live for about 8–10 weeks. It is estimated that the house dust mite can produce 20 fecal pellets/day that range from 20 to 50 μm. House dust mites are ~75% water by weight and therefore need to absorb water from the water vapor in the air, making relative humidity a critical factor for survival.

The population of *Dermatophagoides* species has been observed in hospital halls, non-carpeted patient's rooms, and carpeted patient's rooms through vacuuming of floor in winter and summer periods. As a summer control set, bedrooms in homes of workers have been checked out. Out of 141 total dust samples obtained, *D. pteronyssinus* or *D. farinae* have not been found in 60 hospital dust samples that are acquired during winter period. Even though mites have been originated in certain sites in hospital during summer dust assemblage, mite population in these localities and mean mite population for entirely samples persisted insignificant. For the period of summer dust sampling taken from bedroom carpets of altogether worker houses checked out observed positive for mites, with a number of homes having high or moderate densities (ranged 22–8340 mites/g of dirt). Prevalence of dust mite in a hospital might be retained very little even if in worker homes, mite levels are found moderate to high. The reasons accountable for little mite populations in hospital are the usage of low-pile carpets, keeping low relative humidity, and upright laundering and housekeeping practices [21].

The house dust mites *D. farinae* and *D. pteronyssinus* are cosmopolitan inhabitants of human dwellings. They are most prevalent in high-use areas in homes (e.g., beds, furniture, floors), where shed human skin scales are collected and serve as a source of food. Relative humidity is an important factor regulating the geographic prevalence and density of these mites. In humid geographic areas, most homes contain mite populations, whereas in dry (low-humidity) geographic areas, few homes contain mites. The species prevalence and density of these mites varies both geographically and between homes in the same geographic area. Although factors influencing variations in mite density between homes are not well understood, it appears that mite density is not correlated with housecleaning practices. However, carpeted floors support significantly greater mite populations than do wood or

*Parasitology and Microbiology Research*

and L3, and vertical setae lacking [15].

occurs worldwide [16].

lamp of bright light [17].

phase or interference contract microscope only [18].

the lack of stigmata on idiosoma. This order is furthermore categorized into two suborders, the Acaridia that includes free-living mites and the Psoroptidia which comprises mites parasitic in nature. The former suborder is divided into many families, including the Pyroglyphidae, to which house dust mites belong. Pyroglyphidae are minute mites (full grown adults 170–500 μm in length), cuticle excellently or crudely wrinkle, tarsi termination in a circular pulvillus and a minute claw, anus ventral in position, vestigial genital structures present in both sexual category, vulva of female reverse Y or V fashioned, oil glands existing and exposed among L2

Pyroglyphidae is a family of nonparasitic mites, wherein a great variety of species has been observed. It includes the house dust mites that live in human dwellings, many species that live in the burrows of other animals, and some are pests of dried products stored in humid conditions. The family Pyroglyphidae contains mainly species of astigmatid mites that live in the nests of birds and mammals, where they feed on the epidermal detritus (skin, feathers) left by the host, and

Among the genera of the family Pyroglyphidae, the most outstanding are *Dermatophagoides* and *Euroglyphus*. Three species, *D. farinae*, *D. pteronyssinus*, and *Euroglyphus maynei*, are commonly found in homes of humans and mostly prevalent in high-use areas, where shed skin scales are collected and serve as their food. House dust mites, mostly of the genus *Dermatophagoides*, is important medically and although *D*. *pteronyssinus* and *D*. *farinae* are known as the European and American dust mites, both of these are found worldwide. Both mites *D. farinae* and *D. pteronyssinus* move steadily and slowly; however walk quickly without altering way at whatever time they are opened to an extreme light or heat. In contrary, *E. longior* and *B. evansi* express a negative phototropic response when exposed to an electric

The presence of house dust mites can be confirmed microscopically, which requires collecting samples from mattresses, couches, or carpets. Also, in general practice, it takes at least a 10X magnification to be able to correctly identify them. A modified Berlese funnel is commonly used for extraction of mites from stored grain and has also been successfully used for extraction of *E. longior* and *D. evansi*; however, *D. farinae* cannot be extracted from the dust in this way. A simple method to extract most house dust mites, mite fragments and debris is as follows: weigh 0.1 g of dust from the vacuum cleaner bag, filter by 0.5 and 0.125 mm mesh sieves, relocate dust on 0.125 mm sieve to a lookout glass, moist it with alcohol or ether, whirl suspension to spread out dust uniformly, let the solvent to vaporize, calculate the number of mites below a stereomicroscope, and accumulate them with a camel's hair short-bristled brush. Mites removed through these procedures can be wellmaintained in 85% alcohol for an indefinite period. Short-term mounts of mites can be done in lactic acid, glycerin, mineral oil, phenol, etc. A comparatively longlasting mounting medium is Hoyer's modified Berlese solution ringed with Canada balsam, glycerol, or glyptol. Proof of specimen identity can be done underneath a

Three species, *E. maynei*, *D. pteronyssinus*, and *D. farinae*, are usually observed in home environment of humans. Within homes, these mite species are at peak prevailing in high-use parts, wherever shed skin scales accumulate and assist as their diet. Hence, their highest masses are set up in carpets, nearby easy chairs and sofas, in mattresses, and in fabric-covered overstuffed furniture. But, they may also be found on clothing, in bedding, on pillows, on train and automobile seats, and from time to time in workplaces and schools. Every species is the basis of several potent allergens, which in predisposed people trigger and sensitize allergic reactions. These

allergens are cause of asthma, atopic dermatitis and perennial rhinitis [19].

**274**

tile floors. A home may contain only one species or multiple species can coexist. Most homes are coinhabited by more than one species. In coinhabited homes, one species generally constitutes the greatest percentage of the total population, but the dominant species varies between homes within a geographic area. Knowledge of the mite species prevalence and density in a patient's home is important in evaluating the role of mites as allergens, and in selecting and assessing effective immunotherapy for individual cases. Many species of mites besides *D. farinae* and *D. pteronyssinus* may occur in homes, at times in significant numbers. Therefore, one must be careful when conducting mite surveys to differentiate between not only the primary allergy-causing species but other species as well if species, and density determinations are to be accurate and meaningful. House dust mites live in a microenvironment in which no liquid water is present. However, their bodies are 70–80% water by weight, which must be maintained above a critical lower limit in order to survive for them. Active life stages are able to survive at ambient humidity as low as 60% relative humidity because they extract sufficient water directly from unsaturated air by means of a special adaptation to compensate for water losses. A desiccation-resistant protonymph can survive prolonged periods at low relative humidity, and this stage probably serves as a source of mites for breeding during optimal conditions [22, 23].

An understanding of the life cycle of house dust mites, as well as environmental factors influencing mite populations, can be exploited in mite control. Experiments have been carried out to observe the influences of specific relative humidity maintained at 20°C on population dynamics of mixed and single species of *E. maynei*, *D. pteronyssinus*, and *D. farina*, with indefinite diet. The population density of mixed and single species (*D. pteronyssinus* and *D. farinae*) exponentially increased when reared at 65, 70, and 75% RH. The average population growth amounts are 32.5 ± 4.7 and 17.3 ± 4.4 per week for *D. pteronyssinus* and *D. farina*, respectively. Average populations doubling up periods are 4.2 ± 1.3 and 2.2 ± 0.3 weeks for *D. farinae* and *D. pteronyssinus*, respectively. Diversified cultures of species, initiated with identical numbers of *D. pteronyssinus* and *D. farina*, caused greater percentages of *D. pteronyssinus* and *D. farina.* In cultures taking place with 25% of one species and 75% of the other, the more frequent species throughout the experiment continued prevailing and in similar ratios. Population densities of *D. pteronyssinus* and *D. farina* both kept at 85% RH dropped over a period of 12-week culturing owing to growth of mold. At 65, 70, 75 and 85% RH, mite *E. maynei* is not capable to stay alive which indicates that its requirements of climate are dissimilar from those of *D. pteronyssinus* and *D. farina.* When held at 21–22°C and relative humidity of ≤50%, population densities of *D. pteronyssinus* and *D. farina* cultures dropped; on the other hand, noteworthy amounts of populations lasted for 10 weeks at 50% RH. At 45% RH, half-life for dryness of *D. pteronyssinus* and *D. farina* is 11.5 and 1.2 weeks, respectively, however, 4.0 and 86.3 weeks, respectively, at 50% RH. The information indicates that a ≤50% RH would have to be retained for longer times to decrease *D. pteronyssinus* and *D. farina* both through drying processes. The outcomes of this work express that *D. pteronyssinus* and *D. farina* have great population growth and reproductive potential rates, which designate that mite decline processes must be thoroughgoing otherwise densities of mite will reappear to great points rapidly following remediation if suitable diet and appropriate microclimatic situations occur [24, 25].

Mites are complex organisms, which produce thousands of different proteins and other macromolecules. Allergens from dust mites are connected to body secretions (chitinase), fecal material (enzymes) and body anatomy (muscle tropomyosin). Twenty diverse sets of mite allergens have been categorized. The incidence of reactivity to the majority of these allergens between patients sensitive to dust mites is beyond 50%. Sensitivity to allergens differs equally within and between persons.

**277**

of characters.

*House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination*

are allergic to multiple allergens of a species and to multiple mite species.

middle of 10 and 240 minutes later after eating of contaminated foods [26].

House dust mites primarily feed on organic detritus such as flakes of shed skin. Other nutrients are provided by animal dander, pollen, bacteria and mold. House dust mites reproduce and survive the greatest in soft stuffs (like carpets with lengthy pile, bedclothes and plush toys) that contain a big source of their diet source. The unchanging environmental circumstances are best provided inside homes. Internal domestic humidity is very vital, when moisture is less than 50%; house dust mites are incapable to sustain their water balance and become more vulnerable to desiccation. The house dust mites select diet which has been pre-decomposed by fungi that decrease fat content of skin cells. The fungi in turn usage house dust mite skin cells and feces as nitrogen source, which form a minute

The maximum vital limiting cause for house dust mite population densities is air humidity. House dust mite osmoregulation is through cuticle and for that purpose, they need a great ambient air humidity to avoid extreme water loss. Additionally, supracoxal glands take up ambient water vapor actively and protonymph stage in the life cycle is desiccation resistant. Greater house dust mite population densities are created when indoor absolute air humidity is beyond 7 g/kg (45% relative humidity at 20°C). As a result, aeration by air-conditioning structures is being established as a resource of mite control. In an integrated approach, a number of other features of home atmosphere are likewise being operated to render the habitation less fit for mites. The prospective occurs for evolving models of house dust mite populations,

environmental features and influences of several tactics to control [28].

Pyroglyphidae is divided into subfamily Pyroglyphinae wherein anterior extremity of the body is prolonged by a pointed or forked tegmen, which covers the base of the gnathosoma in both male and female, while tegmen absent in the second

Males in *Dermatophagoides* Bogdanov are with hairs sce much longer and thicker than sci and tarsus III without spines. Perianal ring is simple (not denticulate) and with a hysteronotal shield. Females have hairs sce much longer and thicker than sci. Legs III and IV are equal or subequal in length, and hysteronotal shield is absent. However, *Malayoglyphus*, *Hirstia* and *Sturnophagoides* do not have this combination

Generally, the prevalence of sensitivity to house dust mites is about 27.5% in the few populations. Allergens from one species may be species specific, or they may crossreact with allergens from another mite species. Most patients with mite sensitivities

Allergies to dust mites are associated with allergic rhinitis and asthma. Systemic anaphylaxis may take place after eating of unheated or heated mite-polluted diets. This problem can be more widespread in subtropical and tropical states than earlier documented. The greatly common signs resulting after the consumption of mite-polluted flour are breathlessness, wheezing, angioedema and rhinorrhea, and these start in the

*DOI: http://dx.doi.org/10.5772/intechopen.91891*

**3. Dust mite habitat**

ecosystem in their environment [27].

**4. House dust mite fauna of prominence**

**4.1 Subfamily Dermatophagoidinae Fain, 1963**

subfamily Dermatophagoidinae.

*House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination DOI: http://dx.doi.org/10.5772/intechopen.91891*

Generally, the prevalence of sensitivity to house dust mites is about 27.5% in the few populations. Allergens from one species may be species specific, or they may crossreact with allergens from another mite species. Most patients with mite sensitivities are allergic to multiple allergens of a species and to multiple mite species.

Allergies to dust mites are associated with allergic rhinitis and asthma. Systemic anaphylaxis may take place after eating of unheated or heated mite-polluted diets. This problem can be more widespread in subtropical and tropical states than earlier documented. The greatly common signs resulting after the consumption of mite-polluted flour are breathlessness, wheezing, angioedema and rhinorrhea, and these start in the middle of 10 and 240 minutes later after eating of contaminated foods [26].

### **3. Dust mite habitat**

*Parasitology and Microbiology Research*

optimal conditions [22, 23].

tile floors. A home may contain only one species or multiple species can coexist. Most homes are coinhabited by more than one species. In coinhabited homes, one species generally constitutes the greatest percentage of the total population, but the dominant species varies between homes within a geographic area. Knowledge of the mite species prevalence and density in a patient's home is important in evaluating the role of mites as allergens, and in selecting and assessing effective immunotherapy for individual cases. Many species of mites besides *D. farinae* and *D. pteronyssinus* may occur in homes, at times in significant numbers. Therefore, one must be careful when conducting mite surveys to differentiate between not only the primary allergy-causing species but other species as well if species, and density determinations are to be accurate and meaningful. House dust mites live in a microenvironment in which no liquid water is present. However, their bodies are 70–80% water by weight, which must be maintained above a critical lower limit in order to survive for them. Active life stages are able to survive at ambient humidity as low as 60% relative humidity because they extract sufficient water directly from unsaturated air by means of a special adaptation to compensate for water losses. A desiccation-resistant protonymph can survive prolonged periods at low relative humidity, and this stage probably serves as a source of mites for breeding during

An understanding of the life cycle of house dust mites, as well as environmental factors influencing mite populations, can be exploited in mite control. Experiments have been carried out to observe the influences of specific relative humidity maintained at 20°C on population dynamics of mixed and single species of *E. maynei*, *D. pteronyssinus*, and *D. farina*, with indefinite diet. The population density of mixed and single species (*D. pteronyssinus* and *D. farinae*) exponentially increased when reared at 65, 70, and 75% RH. The average population growth amounts are 32.5 ± 4.7 and 17.3 ± 4.4 per week for *D. pteronyssinus* and *D. farina*, respectively. Average populations doubling up periods are 4.2 ± 1.3 and 2.2 ± 0.3 weeks for *D. farinae* and *D. pteronyssinus*, respectively. Diversified cultures of species, initiated with identical numbers of *D. pteronyssinus* and *D. farina*, caused greater percentages of *D. pteronyssinus* and *D. farina.* In cultures taking place with 25% of one species and 75% of the other, the more frequent species throughout the experiment continued prevailing and in similar ratios. Population densities of *D. pteronyssinus* and *D. farina* both kept at 85% RH dropped over a period of 12-week culturing owing to growth of mold. At 65, 70, 75 and 85% RH, mite *E. maynei* is not capable to stay alive which indicates that its requirements of climate are dissimilar from those of *D. pteronyssinus* and *D. farina.* When held at 21–22°C and relative humidity of ≤50%, population densities of *D. pteronyssinus* and *D. farina* cultures dropped; on the other hand, noteworthy amounts of populations lasted for 10 weeks at 50% RH. At 45% RH, half-life for dryness of *D. pteronyssinus* and *D. farina* is 11.5 and 1.2 weeks, respectively, however, 4.0 and 86.3 weeks, respectively, at 50% RH. The information indicates that a ≤50% RH would have to be retained for longer times to decrease *D. pteronyssinus* and *D. farina* both through drying processes. The outcomes of this work express that *D. pteronyssinus* and *D. farina* have great population growth and reproductive potential rates, which designate that mite decline processes must be thoroughgoing otherwise densities of mite will reappear to great points rapidly following remedia-

tion if suitable diet and appropriate microclimatic situations occur [24, 25].

Mites are complex organisms, which produce thousands of different proteins and other macromolecules. Allergens from dust mites are connected to body secretions (chitinase), fecal material (enzymes) and body anatomy (muscle tropomyosin). Twenty diverse sets of mite allergens have been categorized. The incidence of reactivity to the majority of these allergens between patients sensitive to dust mites is beyond 50%. Sensitivity to allergens differs equally within and between persons.

**276**

House dust mites primarily feed on organic detritus such as flakes of shed skin. Other nutrients are provided by animal dander, pollen, bacteria and mold. House dust mites reproduce and survive the greatest in soft stuffs (like carpets with lengthy pile, bedclothes and plush toys) that contain a big source of their diet source. The unchanging environmental circumstances are best provided inside homes. Internal domestic humidity is very vital, when moisture is less than 50%; house dust mites are incapable to sustain their water balance and become more vulnerable to desiccation. The house dust mites select diet which has been pre-decomposed by fungi that decrease fat content of skin cells. The fungi in turn usage house dust mite skin cells and feces as nitrogen source, which form a minute ecosystem in their environment [27].

The maximum vital limiting cause for house dust mite population densities is air humidity. House dust mite osmoregulation is through cuticle and for that purpose, they need a great ambient air humidity to avoid extreme water loss. Additionally, supracoxal glands take up ambient water vapor actively and protonymph stage in the life cycle is desiccation resistant. Greater house dust mite population densities are created when indoor absolute air humidity is beyond 7 g/kg (45% relative humidity at 20°C). As a result, aeration by air-conditioning structures is being established as a resource of mite control. In an integrated approach, a number of other features of home atmosphere are likewise being operated to render the habitation less fit for mites. The prospective occurs for evolving models of house dust mite populations, environmental features and influences of several tactics to control [28].

#### **4. House dust mite fauna of prominence**

Pyroglyphidae is divided into subfamily Pyroglyphinae wherein anterior extremity of the body is prolonged by a pointed or forked tegmen, which covers the base of the gnathosoma in both male and female, while tegmen absent in the second subfamily Dermatophagoidinae.

#### **4.1 Subfamily Dermatophagoidinae Fain, 1963**

Males in *Dermatophagoides* Bogdanov are with hairs sce much longer and thicker than sci and tarsus III without spines. Perianal ring is simple (not denticulate) and with a hysteronotal shield. Females have hairs sce much longer and thicker than sci. Legs III and IV are equal or subequal in length, and hysteronotal shield is absent. However, *Malayoglyphus*, *Hirstia* and *Sturnophagoides* do not have this combination of characters.

#### *4.1.1* Dermatophagoides farinae *Hughes (American house dust mite)*

American house dust mite *D. farinae* (**Figure 2**) is found in flour, poultry and pig feeds, safflower seed meal, and albumin tannate in the drugstore. Differential diagnosis in females are the following: idiosoma is 395–435 μm in length; propodonotal shield about 1.4 times as lengthy as broad; vestibule of bursa sclerotized well and designed similar to a calabash pipe; bursa is not extended further than this vestibule; generally tarsus I with well-built curled progression (ongle); and epigynum crescent fashioned. In males, idiosoma is 285–345 μm long; males either homeomorphic with epimera I free (and normal first legs) or heteromorphic with epimera I fused to form a V or Y (and enlarged I legs).

Females of *D. farinae* tarsi I and II are with prominent, pointed apical spine (s); bursa copulatrix broad and strongly sclerotized in region adjacent to external opening (arrow); and sclerotized section pointed. Females: tarsus I with short, straight, blunted spine (s); and tarsus II lacking spine. Bursa copulatrix is narrow and weakly sclerotized in region adjacent to external opening anteriorly. Female is with central area of dorsum among hairs d2-d2-d3-d3 with crosswise striations in the frontal half and with oblique or convex striations in the latter half. Bursa copulatrix proximal portion is without sclerifications and distal portion widened into a minute, sclerified, and triangular sack*.* Male hysteronotal shield is short (broader than long) and not reaching the base of hairs d2. Epimera I either free or fused to form a sternum and legs I generally swollen. Male tarsus I is with small apical protuberance (process S) and curved apical spine (f), and tarsus II with process S and no spine.

Duration of the life cycle at 16, 23, 30 and 35°C, and fecundity at 23°C and 75% RH have been determined for *D. farinae*. Durations of the life cycles at 30 and 23o C are 17.5 ± 1.2 and 35.6 ± 4.4 days, respectively. At 16 and 35o C, only a small number of eggs finalized growth to the adult stage. At 75% RH and 23°C, following development of female from tritonymph, the preoviposition period is 3.7 ± 1.1 days. The mean reproductive duration is 34.0 ± 10.7 days with an average of total 65.5 ± 17.4 eggs laid per female. Longevity of female is 63.3 ± 64.6 days after termination of egg production. The females weigh approximately 5.8 ± 0.2 μg (fresh weight), while males are approximately half of this weight 3.5 ± 0.2 μg [29].

Studies of the life cycle of cultured *D. farinae* found that after initial mating, *D. farinae* females lived for 63.3 days after their egg production period ended. The long period after cessation of egg production for *D. farinae* suggested that *D. farinae* females could mate multiple times and produce eggs continuously for a longer period. This study revealed that *D. farinae* females are capable of more than one successful mating that results in an increased egg production than that of a single mating. Females actively attract males during the reproductive period, but not

**279**

**Figure 3.**

Dermatophagoides pteronyssinus.

*House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination*

afterward even though it continues to live a long time. These females have 11 days longer reproductive period and produced 30.7% more eggs than in females that only mated one time after they emerged from the tritonymphal stage. However, the

Adopting the separate culturing technique, under a continuous temperature at 25°C, the effects of relative humidities of 86, 76, 61 and 36% on the life cycle of *D. farinae* and *D. pteronyssinus* have been detected. At 76% RH, the development of eggs to adults takes place in the shortest period of 39.6 ± 6.6 (29–60) days, for egg 8.1 ± 0.1 days, for larva 8.2 ± 0.3 days, for protonymph 17.0 ± 5.7 days and for tritonymph 6.6 ± 0.4 days. The number of eggs laid is generally 1 or 2 per day by a female, but, certain females in a day sometimes laid 5 or 6 eggs. The biggest total number of eggs (80.6 ± 8.2) laid per female is observed at 86% RH, while nu-mated female at 76% RH showed longest longevity of 188.8 ± 60.9 days ranging from 92 to 378 days. The longevity of the female is usually longer than that of the

*4.1.2* Dermatophagoides pteronyssinus *(Trouessart) (European house dust mite)*

when viewed from above and ductus bursae of uniform thickness.

This particular species of mite has been found in all dust samples from many different countries in varying numbers. Hysteronotal shield of *D. pteronyssinus* (**Figure 3**), in males, is lengthy (lengthier than wide), and spreading further frontward than hairs d2, epimera I diverging or parallel and legs I are usual. Females are only with central area of dorsum among hairs d2-d2-d3-d3 having longitudinal patterns. Bursa copulatrix has proximal portion with a sclerite in the form of a daisy and distal portion expanded very slightly. Base of receptaculum seminis are U-shaped in cross section, broader apically than basally, circular with 10–13 lobes

The life cycle of *D. pteronyssinus* has been studied at 25°C and 80% relative humidity. Observations made on freshly laid eggs until they develop into adults and periods between different stages are recorded. The life cycle of *D. pteronyssinus* consists of five stages: egg, larva, protonymph, tritonymph and adult. Adult females lay up to 40–80 eggs singly or in small groups of 3–5. After eggs hatch, a six-legged larva emerges and after two nymphal stages occur, an eight-legged nymph appears. The life cycle from egg to adult is about 1 month with the adult living an additional 1–3 months. The average life cycle for a house dust mite is 65–100 days. A mated female house dust mite can last up to 70 days, laying 60–100 eggs in the last 5 weeks of her life. The eggs required an average of 11.26 days to develop into adults.

*DOI: http://dx.doi.org/10.5772/intechopen.91891*

male [31].

post-reproductive period is still long (58.6 days) [30].

**Figure 2.** Dermatophagoides farinae.

#### *House Dust Mites: Ecology, Biology, Prevalence, Epidemiology and Elimination DOI: http://dx.doi.org/10.5772/intechopen.91891*

afterward even though it continues to live a long time. These females have 11 days longer reproductive period and produced 30.7% more eggs than in females that only mated one time after they emerged from the tritonymphal stage. However, the post-reproductive period is still long (58.6 days) [30].

Adopting the separate culturing technique, under a continuous temperature at 25°C, the effects of relative humidities of 86, 76, 61 and 36% on the life cycle of *D. farinae* and *D. pteronyssinus* have been detected. At 76% RH, the development of eggs to adults takes place in the shortest period of 39.6 ± 6.6 (29–60) days, for egg 8.1 ± 0.1 days, for larva 8.2 ± 0.3 days, for protonymph 17.0 ± 5.7 days and for tritonymph 6.6 ± 0.4 days. The number of eggs laid is generally 1 or 2 per day by a female, but, certain females in a day sometimes laid 5 or 6 eggs. The biggest total number of eggs (80.6 ± 8.2) laid per female is observed at 86% RH, while nu-mated female at 76% RH showed longest longevity of 188.8 ± 60.9 days ranging from 92 to 378 days. The longevity of the female is usually longer than that of the male [31].

### *4.1.2* Dermatophagoides pteronyssinus *(Trouessart) (European house dust mite)*

This particular species of mite has been found in all dust samples from many different countries in varying numbers. Hysteronotal shield of *D. pteronyssinus* (**Figure 3**), in males, is lengthy (lengthier than wide), and spreading further frontward than hairs d2, epimera I diverging or parallel and legs I are usual. Females are only with central area of dorsum among hairs d2-d2-d3-d3 having longitudinal patterns. Bursa copulatrix has proximal portion with a sclerite in the form of a daisy and distal portion expanded very slightly. Base of receptaculum seminis are U-shaped in cross section, broader apically than basally, circular with 10–13 lobes when viewed from above and ductus bursae of uniform thickness.

The life cycle of *D. pteronyssinus* has been studied at 25°C and 80% relative humidity. Observations made on freshly laid eggs until they develop into adults and periods between different stages are recorded. The life cycle of *D. pteronyssinus* consists of five stages: egg, larva, protonymph, tritonymph and adult. Adult females lay up to 40–80 eggs singly or in small groups of 3–5. After eggs hatch, a six-legged larva emerges and after two nymphal stages occur, an eight-legged nymph appears. The life cycle from egg to adult is about 1 month with the adult living an additional 1–3 months. The average life cycle for a house dust mite is 65–100 days. A mated female house dust mite can last up to 70 days, laying 60–100 eggs in the last 5 weeks of her life. The eggs required an average of 11.26 days to develop into adults.

**Figure 3.** Dermatophagoides pteronyssinus.

*Parasitology and Microbiology Research*

process S and no spine.

*4.1.1* Dermatophagoides farinae *Hughes (American house dust mite)*

with epimera I fused to form a V or Y (and enlarged I legs).

are 17.5 ± 1.2 and 35.6 ± 4.4 days, respectively. At 16 and 35o

males are approximately half of this weight 3.5 ± 0.2 μg [29].

diagnosis in females are the following: idiosoma is 395–435 μm in length;

American house dust mite *D. farinae* (**Figure 2**) is found in flour, poultry and pig feeds, safflower seed meal, and albumin tannate in the drugstore. Differential

propodonotal shield about 1.4 times as lengthy as broad; vestibule of bursa sclerotized well and designed similar to a calabash pipe; bursa is not extended further than this vestibule; generally tarsus I with well-built curled progression (ongle); and epigynum crescent fashioned. In males, idiosoma is 285–345 μm long; males either homeomorphic with epimera I free (and normal first legs) or heteromorphic

Females of *D. farinae* tarsi I and II are with prominent, pointed apical spine (s); bursa copulatrix broad and strongly sclerotized in region adjacent to external opening (arrow); and sclerotized section pointed. Females: tarsus I with short, straight, blunted spine (s); and tarsus II lacking spine. Bursa copulatrix is narrow and weakly sclerotized in region adjacent to external opening anteriorly. Female is with central area of dorsum among hairs d2-d2-d3-d3 with crosswise striations in the frontal half and with oblique or convex striations in the latter half. Bursa copulatrix proximal portion is without sclerifications and distal portion widened into a minute, sclerified, and triangular sack*.* Male hysteronotal shield is short (broader than long) and not reaching the base of hairs d2. Epimera I either free or fused to form a sternum and legs I generally swollen. Male tarsus I is with small apical protuberance (process S) and curved apical spine (f), and tarsus II with

Duration of the life cycle at 16, 23, 30 and 35°C, and fecundity at 23°C and 75% RH have been determined for *D. farinae*. Durations of the life cycles at 30 and 23o

of eggs finalized growth to the adult stage. At 75% RH and 23°C, following development of female from tritonymph, the preoviposition period is 3.7 ± 1.1 days. The mean reproductive duration is 34.0 ± 10.7 days with an average of total 65.5 ± 17.4 eggs laid per female. Longevity of female is 63.3 ± 64.6 days after termination of egg production. The females weigh approximately 5.8 ± 0.2 μg (fresh weight), while

Studies of the life cycle of cultured *D. farinae* found that after initial mating, *D. farinae* females lived for 63.3 days after their egg production period ended. The long period after cessation of egg production for *D. farinae* suggested that *D. farinae* females could mate multiple times and produce eggs continuously for a longer period. This study revealed that *D. farinae* females are capable of more than one successful mating that results in an increased egg production than that of a single mating. Females actively attract males during the reproductive period, but not

C

C, only a small number

**278**

**Figure 2.**

Dermatophagoides farinae.

The ranges of life longevity of mated males and females are 18–64 and 20–54 days, respectively. At 76% RH, mite *D. pteronyssinus* exhibited the shortest duration of development. It took a total duration of 37.1 ± 2.5 days with a range from 30 to 54 days, for egg 6.2 ± 0.3 days, for larva 10.7 ± 0.3 days, for protonymph 8.6 ± 1.0 days and for tritonymph 11.4 ± 2.2 days. The largest total number of eggs, 76.2+22.2, is laid by a female of *D. pteronyssinus.* In a 10-week life span, a house dust mite will produce approximately 2000 fecal particles and an even larger number of partially digested enzyme-covered dust particles. The conditions used in the rearing experiments may be considered optimal for maintaining culture of *D. pteronyssinus* [32].
