The term house dust mite (HDM) is generalized to all species of mites which have a worldwide distribution (1). Like Spiders, HDMs belong to the class Arachnida. Of the at least 50 species of HDMs that have been found in domestic house dust, two of the family pyroglyphidae, namely D. pteronyssinus and D. farinae, are the most important in temperate climates, both in terms of numbers and of clinical relevance. Clinically, these HDMs are of relevance because most asthma symptoms in children and young adults are associated with both an immediate hypersensitivity to their inhaled allergens, and a familial tendency towards atopy (2). D. pteronyssinus predominates over most HDM species worldwide and is the most frequent species in tropical and subtropical areas. D. farinae is the most common species in dry, continental climates and is rare in costal climates (3). The tropical rat mite, Ornithonyssus bacoti, is one of the most common houses invading species; it is an obligate, blood feeding ecto-parasite with worldwide distribution (4). Natural host of Ornithonyssus bacoti include several species of rat and mice, hamsters, gerbils, voles, and other wild rodents (5). Although none of these species of mite are truly parasitic on human or pets, they bite people readily, often producing dermatitis and itching. Rat mite infestations occur in structures where rat nests are located, infestation are sometimes first noticed following examination or after the natural host have died or left the structure and may also occur where heavy mite infestations have developed around a rodent nest. If a rat has a nest in an attic or other site inside the home and it dies or vacates the nest these mites will leaves the nest and body in search of a host and can attack humans. The bite of these ecto-parasite cause irritation and sometimes a painful dermatitis leaving red spots on the infested skin (6).
Although dust mites were observed in dust by a scientist in 1694, it was not until the 1960’s that they were associated with allergies and have become recognized in the past 30 years as the most important sources of allergens in human habitation (7). Over the years dust mites have become a target of extensive research for their relation to allergies and development of asthma (8). Free- living mites have long been recognised as one of the most important sources of allergen of house dust responsible for the origin of atopic and bronchial asthma, rhinitis and dermatitis , eczema, hay fever, sinusitis, and middle ear infection (9). As a very ancient organism, the mites is enormous diversified and adapted to a wide variety of environments including plants, animals, human, soil, fresh and salty water, organic rabbles, houses, mattresses and old books. They thrive in their thousands in warm, moist places feeding on dead skin scales; they live in soft furnishing such as beds, bedding, carpets, and soft toys. A great number of factors play a role in exposure to mites, the prevalence of different categories of mites vary considerably among geographical locations. Different socioeconomic conditions influence the prevalence of domestic mites. Environmental factors are likely to play an important role in the control of house dust mites (HDM). Thus, understanding environmental factors influencing mite population can be expelled in mite control. Sinai is the veritable gateway to Egypt from the east. It is triangular in shape, and stretches for 400 Km from north to south and 200 Km from east to west. It is generally hot during the summer, stormy and exposed to cold air currents during the winter. Average daily maximum temperature, range from 29oC to 17oC, and minimum, from 21oC to 9oC in the summer and winter respectively. Also daily relative humidity fluctuates between 65% in daytime and 85% at night in the summer and between 60% and 80% respectively in winter.
Material and Methods
Study areas:
El Arish is the capital and largest city, with 114,900 inhabitants (2002), of the North Sinai governorate. It lies on the Mediterranean coast of the Sinai Peninsula, 214 miles northeast of Cairo. El Arish is by a big Wadi called the Wadi El -Arish which receives flash flood water from much of north and central Sinai.
Study design
A descriptive, cross- sectional study was designed to investigate the mite fauna in homes of El Arish, north of Sinai. In this study El Arish city was divided into 10 areas in each area 5 homes were selected randomly. The occupants agreed to participate in the study.
1. Criteria of house selection
A short characteristic of each house and of one of the examined places is presented:
a. A wooden new houses, a bed about 35 years old, it is used only at weekends more frequently in summer-time, the room is not heated, and temperature and RH depends on changes of the environmental RH and temperature fluctuations.
b. An apartment on the end of the block house, the room is cold and damp in winter and sunny and warm in summer. Abed 12 years old is used every night.
c. A stone house heated with gas and stove, rather damp room on the first floor. A 5 years old bed is sometimes used for sleeping
d. A warm apartment on the first floor of the block has average air temperature about 20oC, RH 60% in summer time, and 68%. An old cotton mattress is used every night for about 20 years.
- A new stone with hermetic windows. An old (about 40 years) coach is used in living room.
- A low income homes included single family detached houses.
- An apartments in a free standing building with three or fewer units, and apartments in complexes with three or more units.
2. Criteria of patients and control
Patients with history suggestive of asthma together with healthy individuals as control were lived in the houses studied. All patient and control completed a questionnaire to take a psychosocial history including question about age, gender, educational level, employment, family history of asthma, information relevant to asthma risk factors, including: socioeconomic status, home life, school, the age of the mattress, signs of humidity in the bedroom, number of occupants, symptoms, severity of symptoms, asthma treatment and understanding of treatment.
People were subjected to skin prick (Allergy prick test [Scratch test] Zhengzhou Concern Medical supplies Co., Ltd), by placing a small amount of the (allergen) on the skin (the forearm), and then scratching or pricking the skin so that the allergen is introduced under th
