Clinical importance of Mites in Human Health

Order Acari

Order Acari

Most mites are small, less than 1mm long, but the adult length of different species ranges from 100mm to 2cm. In most mites, the cephalothorax and abdomen are fused into an unsegmented ovoid body. Respiration occurs either by means of trachea or directly through the exoskeleton. Many mites pass through several distinct stages during their life cycle. In most, an inactive eight-legged pre-larva gives rise to an active six-legged larva, which hatches from the egg and in turn produces a succession of three eight-legged stages and finally the adult males and females. Mites are very diverse, not only in their structure but also in their habits. They are found in virtually every terrestrial, freshwater, and shallow marine habitat known and feed on fungi, plants and animals; they act as predators and as internal and external parasites of both invertebrates and vertebrates. Many mites are well known to human beings because of their irritating bites and the diseases they transmit.Follicle mites (Desmodex folliculorum) live in the hair follicles and wax glands of the human forehead, nose, and chin but usually cause no symptoms. Other mites cause mange in dogs and cats, often with severe consequences. A number of species of mites can cause house-dust allergy, which is aggravating to millions of people throughout the world; they are inhaled along with dust.Sarcoptes Scabiei (itch mite).

Male (0.2mm) is smaller than female (0.4mm). Body is Oval, convex dorsally and flat ventrally. The cuticle is striated and carries several hairs. Mouthparts:

1. rudimentary hypostome without teeth

2. Chelicerae end in pincer-like structures

3. pedipalps are short and 3-segmented.Legs: of the female mite has four short pairs; anterior and posterior sides in which the anterior pairs are completed by sucker-like structures and the posterior pairs are completed with long bristles. Male mite legs are similar, but the 4th pair is ended with suckers instead of bristles. Larva has 3 pairs of legs (2 anterior and 1 posterior). Posterior pair is completed with bristles. Nymphs are usually quite similar to the adults, differing mainly in their smaller size.Life cycle

1. mating occurs on the skin, then male dies and female burrows a tunnel in the superficial layers of the skin and lays eggs.

2. Larvae hatch within one week

3. Larvae molt into nymphs (one nymph stages for males, two for females). The whole cycle takes about 2 weeks.Pathogenicity

Sarcoptes scabiei is the causative agent of scabies. Interdigital spaces, flexor surfaces of wrists and forearms, armpits, groin and genitals are preferential sites of infection. Usually head and neck are not affected in adults. Burrowing is activated by warmth, so itching is exaggerated during night. The lesions are reddish tracts with minute vesicles. Scratching spread infestation and induces secondary bacterial infection. Scabies is transmitted by close personal contact (congested population, poverty,, in slums and jails). Diagnosis is made by:1. Itching of affected surfaces at night2. Specific lesions3. findings of the parasites int he tunnels by a needle.Control is provided by1. proper treatment of infected person2. Sterilization of clothes and bedding3. Personal cleanliness.I am Funom Theophilus Makama. I advertise through writing. As a platinum expert Author, I write lots of articles and hence promote interested websites, companies, groups, organizations, and communities through publishing and distributing my articles. For more information on this interesting venture, click on the link belowhttp://funom-makama.blogspot.com/2010/07/advertising-contracts.htmlClinical importance of Mites in Human HealthBy: DChosen1

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