October 31, 2014

Parastitic Mites of Humans

Mites are very small arthropods which are closely related to ticks. Mite larvae have six legs whereas the nymphal and adult stages have eight. Most species of mites are pests of agricultural crops. However, certain types of mites are parasitic on humans.

 

Chiggers

chiggerChiggers are the larvae of a family of mites that are sometimes called red bugs. The adults are large, red mites often seen running over pavement and lawns. Chiggers are extremely small (0.5 mm) and are difficult to see without magnification. The six-legged larvae are hairy and yellow-orange or light red. They are usually encountered outdoors in low, damp places where vegetation is rank and grass and weeds are overgrown. Some species also infest drier areas, however, making it difficult to predict where an infestation will occur.

 

Chiggers overwinter as adults in the soil, becoming active in the spring. Eggs are laid on the soil. After hatching, the larvae crawl about until they locate and attach to a suitable host. The larvae do not burrow into the skin, but inject a salivary fluid which produces a hardened, raised area around them. Body fluids from the host are withdrawn through a feeding tube. Larvae feed for about 4 days and then drop off and molt to nonparasitic nymphs and adults. Chiggers feed on a variety of wild and domestic animals, as well as humans. The life cycle (from egg to egg) is completed in about 50 days.

 

Most people react to chigger bites by developing reddish welts within 24 hours. Intense itching accompanies the welts, which may persist for a week or longer if not treated. Bites commonly occur around the ankles, waistline, armpits, or other areas where clothing fits tightly against the skin. Besides causing intense itching, chigger bites that are scratched may result in infection and sometimes fever. Chiggers in North America are not known to transmit disease.

 

Persons walking in chigger-infested areas can be protected by treating clothing (cuffs, socks, waistline, sleeves) or exposed skin with tick repellents. Some repellents should only be used on clothing; and it is important to follow label directions. People who suspect they may have been attacked by chiggers should take a soapy bath immediately and apply antiseptic to any welts. A local anesthetic will provide temporary relief from itching.

 

Regular mowing and removal of weeds and brush make areas less suitable for chiggers and their wild hosts. Mowing also enhances penetration and performance of miticides, should they be required. Chigger populations can be further reduced by treating infested areas with residual miticides. Applications should be thorough but restricted to areas frequented and suspected of being infested.

 

Human Scabies

scabies miteThe sarcoptic itch mites, Sarcoptes scabei, infest the skin of a variety of animals including humans. The types of Sarcoptes inhabiting the skin of mammals are all considered forms of Sarcoptes scabei and can exchange hosts to some degree. (For example, Canine scabies can be temporarily transferred from dogs to humans, causing itching and lesions on the waist, chest and forearms.)

 

Human scabies mites are very small and are rarely seen. They commonly attack the thin skin between the fingers, the bend of the elbow and knee, the penis, breasts, and the shoulder blades. The mites burrow into the skin, making tunnels up to 3 mm (0.1 inch) long. When they first burrow into the skin, the mites cause little irritation, but after about a month, sensitization begins. A rash appears in the area of the burrows and intense itching is experienced.

 

Scabies mites are transmitted by close personal contact, usually from sleeping in the same bed. Bedridden individuals in institutions (e.g., nursing homes) may also pass the mites from caregiver to patient. The adult fertilized female mite is usually the infective life stage. She adheres to the skin using suckers on her legs and burrows into the skin where she lays her oval eggs. In 3 to 5 days these eggs hatch into larvae and move freely over the skin. Soon they transform into nymphs and reach maturity 10 to 14 days after hatching.

 

A scabies infestation should be handled as a medical problem and is readily diagnosed and treated by most physicians. (Confirmation requires isolating the mites in a skin scraping.) The first step to control a scabies infestation usually involves softening the skin with soap and water to make sure the pesticide treatments can penetrate well. An evening bath followed by overnight treatment works best. A total body (neck- down) application of topical pesticide medication should remain for 8-12 hours before showering in the morning. Commonly used products include lindane (Kwell ™), permethrin (Elimite ™) and crotamiton (Eurax ™). Follow directions on the product package carefully.

 

Because the symptoms of scabies mite infestations are delayed by about a month, other members of the household besides those showing symptoms may be harboring the mites. It is important that everyone in the infected family or living group go through the treatment regime. A second treatment may be necessary to eliminate an infestation of scabies mites, but patients should avoid overzealous pesticide treatment since itching may persist for a week or more after treatment and does not necessarily indicate treatment failure.

 

Scabies mites cannot live off of a human host for more than 24 hours. Therefore, insecticide treatment of premises is not warranted. It is recommended, however, that coincident with treatment, the clothing and bedding from infested individuals be washed in hot water or dry cleaned.

 

 

Dust mites

(Dermatophagoides farinae) are often called spider mites. These very small arachnids are off white in color, shaped like a globe and can have an average life span of a month and known to live up to 3 months!

Because dust mites are so small the human eye alone can not detect them; To see a dust mites, you’ll need a basic microscope. Females dust mites are larger than their male counterpart and can lay anywhere from 1 to three eggs per day.

* According to controversial article by William F. Lyon written for the Extension Service at Ohio State University, a typical used mattress may have anywhere from 100,000 to 10 million mites inside!

It goes on to state that 10% of the weight in a pillow that is two years old can be composed of dead mites and their waste. One more disturbing finding was that when you open your shades and see that beam of light with a ton of floating objects, eighty percent of it are flakes from your skin!

In as little as a month, a dust mite can reach adulthood and thrive best in damp material, such as towels, clothes or a mattress.
Dust Mite
Dust mites love dead skin and some of the best repositories of dead skin are bed covers, blankets, anything made of cloth, dust and more.

Higher then normal humidity levels can also contribute to dust mites.

Dust mites are commonly thought of as causing dermatitis, asthma and rhinitis. Small children are also said to run the risk of asthma if exposed to the feces of dust mites. For example, if you sleep on a mattress containing a large amount of dust mites, you’ll notice red itchy bumps. These bumps are a result of your skin reacting to the allergen of the dust mite.

Controlling Dust Mites

Dust mites can cause a variety of health problems and while there is no way to completely eliminate the dust mites, controlling them can reduce a person’s risk of suffering from the health problems associated with an infestation of dust mites. This article is an overview of measures you can take to control the dust mite population in your home.

While you sleep, dust mites are hiding in your bedding. There are several things that can be done to reduce the dust mites in your bedding. The simplest solution is to wash bedding such as bed covers, blankets and sheets once per week in hot water.

For pillows, it is recommended that you replace feather and down pillows with ones that are have synthetic materials as a filling. Alternatively, you can your regular pillow covers with dust-proof zippered ones.

 

Eyelash Mite

Demodex folliculorum, or the demodicid, is a tiny mite, less than 0.4 mm long, that lives in your pores and hair follicles, usually on the nose, forehead, cheek, and chin, and often in the roots of your eyelashes.
(A follicle is the pore from which a hair grows). Demodicids have a wormlike appearance, with legs that are mere stumps. People with oily skin, or those who use cosmetics heavily and don’t wash thoroughly, have the heaviest infestations … but most adults carry a few demodicids. Inflammation and infection often result when large numbers of these mites congregate in a single follicle.

eyelash Mite



The mites live head-down in a follicle, feeding on secretions and dead skin debris. At the left, you can see three demodicids buried in the follicle of a hair, and you can also see the hair’s shaft. If too many mites have buried into the same follicle, it may cause the eyelash to fall out easily.
An individual female may lay up to 25 eggs in a single follicle, and as the mites grow, they become tightly packed. When mature, the mites leave the follicle, mate, and find a new follicle in which to lay their eggs. The whole cycle takes between 14 to 18 days.
Sometimes demodex is called the ‘face mite’, since it is often associated with blackheads, acne and other skin disorders (although it is not the cause of these). Demodex are harmless and don’t transmit diseases, but large numbers of demodex mites may cause itching and skin disorders, referred to as Demodicosis.

Eyelash Mites



The mites have tiny claws, and needlelike mouthparts for eating skin cells. Their bodies are layered with scales, which help them anchor themselves in the follicle. The mite’s digestive system results in so little waste that the mite doesn’t even have an excretory opening. So although there may be mites in your eyelashes, there isn’t any mite poop! Thank goodness!
However … did you know that you go to sleep at night on a pillow that is home to many thousands of dust mites …which help keep our homes clean by consuming the tens of millions of skin cells we shed each day? Just pretend they’re not there!

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