Mite Biology & Control Female Scabies Mite

Objective هدف Relate the biology of mites to appropriate control measures.

Overview مرور Characteristics and Habits Life Cycle Medical Importance Control Measures

Mites Not all mites are of medical importance. We will be concentrating on the following: Scabies Chiggers Dust Mites Rat Mites The oldest species of arthropods. They are very resilient creatures.

Mites Other mites of some Importance Forage Mites Straw Itch Mites Poultry Mites Follicle Mites Cable Mites

Biology Mites are arachnids closely related to ticks Life cycle : egg, larva, nymph and adults Nymphal stage s; protonymph, deutonymph and tritonymph (not present in all mites) Considerably smaller than ticks Three body segments Mouthparts consist of fewer segments

Biology Have varied appearances and food sources free-living predators external parasites (most) internal parasites (very few) plant feeders stored-products pests

Medical Importance Affect the health of man in three ways By causing dermatitis e.g. scabies and chiggers As vectors of diseases i.e. scrub typhus and Rickettsial pox By causing allergic reactions in man e.g house dust mite

Sarcoptic Itch Mites Sarcoptes scabiei variety hominis causes scabies in humans variety suis causes swine mange variety equi causes horse mange

Scabies (Seven-year Itch) Sarcoptes scabiei Gravid females form burrows in the skin where they lay eggs Larvae burrow out to the skin surface they mature and mating occurs here Eggs and debris are left within burrows

Scabies Transmitted through intimate contact Immunity appears to develop over time Outbreaks occur sporadically Initial effects usually not noticed for first month Scratching leads to complications

Chiggers A.k.a. called Red Bugs Numerous species called chiggers in genus Trombicula Larval mites wait on grass blades for a host to pass by Only larvae feed on man Nymphs and adults are predators Chiggers (the larvae of red mites or harvest mites) (Trombiculidae) are an important group of ectoparasites affecting humans.  

Behavior They don’t burrow into the skin Mouthparts are inserted into a pore or hair follicle Inject digestive fluid into cell, then feed on ruptured cell contents Mite feeds and then leaves host Welt and itching occur after mite is gone Contrary to popular belief, these mite larvae do not feed on blood and do not burrow into the skin. They pierce the skin near a hair follicle and feed on partially digested skin cells using enzymes in the chigger's saliva. They then drop off the host.

Behavior Once on the host the mite crawls around looking for a suitable feeding site They love elastic socks briefs bras They attach to the skin in the ankles, waistline, armpits and perianal area after the host walks through a grassy environment.

Chiggers Bites commonly cause itching in about 3 to 6 hours after feeding dermatitis develops in about 10 to 16 hours secondary infections can occur if bite wounds are scratched The host reacts to the mouth parts and saliva of the mite, however, and after a few hours an erythematous papule appears that is highly pruritic. The intensity of the eruption depends on the sensitivity of the host and may be followed by fever.

Scrub Typhus Transmitted from Leptotromidium mites infected with Rickettsia tsutsugamushi Found in South East Asia Mites and disease are associated with “fringe habits” transition line between wooded and maintained “mite islands” patches of vegetation harboring large numbers of mites

Dust Mites Dermatophagoides pteronyssinus Tiny mites that feed on shed human skin They DO NOT bite! People suffer from allergic reactions to: excreta cast skins secretions Estimates are that dust mites may be a factor in 50 to 80 percent of asthmatics, as well as in countless cases of eczema, hay fever and other allergic ailments. Common causes of allergy include house dust mites, cat dander, cockroach droppings and grass pollen. Symptoms are usually respiratory in nature (sneezing, itching, watery eyes, wheezing, etc.), usually NOT A RASH. However, there are reports of a red rash around the neck. Other allergic reactions may include headaches, fatigue and depression. The wheeze-inducing proteins are digestive juices from the mite gut which are quite potent. An exposure to the mites in the first, crucial year of life can trigger a lifelong allergy. There is no cure, only prevention. One must control house dust mite levels.

Dust Mites Higher humidity levels are more conducive to mite survival Mite populations are present year round The diet is varied with the primary food source, consisting of dander (skin scales) from humans and animals. However, needed nutrients can be provided from fish food flakes, pet food, fungi, cereals, crumbs, etc. Many mite species live in bird's nests, in barns, among stored grain, straw, etc. Beds are a prime habitat (where 1/3 of life occurs). A typical used mattress may have anywhere from 100,000 to 10 million mites inside. Ten percent of the weight of a two year old pillow can be composed of dead mites and their droppings. Mites prefer warm, moist surroundings such as the inside of a mattress when someone is on it. A favorite food is dander (both human and animal skin flakes). Humans shed about 1/5 ounce of dander (dead skin) each week. About 80 percent of the material seen floating in a sunbeam is actually skin flakes. Also, bedroom carpeting and household upholstery support high mite populations.

Rat Mites Blood feeding mites associated with rodents; several species are involved They occasionally inflict painful bites Can also transmit rickettsial pox (Liponyssoides spp. ) and possibly endemic typhus This mite will feed on humans even when rats are present, causing painful bites, intense itching and dermatitis. Barely visible, they are bright red to black with white markings and are usually noticed on walls in basements, kitchens, bathrooms and where rats are found. Mites drop from their host after each blood meal and can survive several days without feeding. For bird and rat mites, standard insect repellents such as diethyl meta-toluamide (deet), ethyl hexanediol or dimethyl phthalate will prevent bites. Locate and remove bird and rodent nests, and treat infested areas with household crawling insect sprays of malathion, diazinon or Baygon. A vacuum cleaner will collect many mites. Dispose of sweeper bag contents.

Rat Mites Most commonly found in buildings infested with rodents Eliminate the rodents and the mites will not be a problem after about two weeks

Tropical Rat Mite Vector of Epidemic Hemorragic Fever Disease is probably viral Rodent population forms reservoir Cases documented in Korea

Forage Mites Several species are involved Normally infest grains, flour and cheese Food handlers are occasionally attacked AKA Grocer’s Itch (Glycyphagus domesticus) Copra Itch (Tyrophagus castellanii) Vanillisme (Acarus siro) These mites can be found in a wide variety of stored products and food and can cause mild dermatitis known as "grocer's itch." Heavy infestations have a sweet or minty odor. A coating of "mite dust," molted skins of the mites, covers the infested grain or cheese. Sometimes the surface of infested materials appears to move due to large numbers of mites. These mites favor damp areas. They do not bite humans. For grain and mold mites, store materials moderately dry (130 degrees F and low relative humidity). Discard infested foodstuffs and clean premises. Treat storage areas with pyrethrins, malathion or resmethrin. Before using insecticides, read the label and follow directions. Infested grains and cheese in food handling institutions must be fumigated only by licensed, certified pest control applicators.

Forage Mites Allergic responses also can occur Intestinal disturbances due to consumption of infested food can also be a problem

Straw Itch Mites Pyemotes tritici A predator in agriculture crops Bean, pea & boll weevils, grain moths Workers come into contact with the mites while handling straw and other commodities Humans, particularly in grain growing areas, are bitten when handling infested straw, crops (beans, cotton, small grains) or crop residues, or similar materials harboring the mites and those who make dried plant arrangements. People who handle mite-infested materials can be attacked. Straw itch mites can travel through the air, so anyone in these areas can be at risk. When straw itch mites become separated from their insect hosts or their hosts become scarce, itch mites may bite other animals, and humans. A person who is severely infested may have thousands of bites from itch mites that cannot be detected by the naked eye. Fortunately, the mites cannot live on humans and do not remain long. There is no evidence that the bites transmit disease, nor that there is a person-to-person transmission of the mite. Bites produce a rash which includes red welts with a small white pustule (head) at the center. One to several hundred bites can occur on a person or animal. The bite is not felt and can take from two to 24 hours for resulting welts to appear. Severe cases can cause infection, fever, vomiting, and joint pain. Severe itching and possible infection can occur if bites are scratched open. Itching may last up to a week or more. Welts will normally disappear within a few weeks. The bites of straw itch mites are characteristically found on the trunk of the body and on the arms. To prevent straw itch mite bites, avoid grassy areas and shower with plenty of soap after being in grassy or weedy areas. An insect repellent containing DEET is also another way of preventing the bites. The best control strategy is to eliminate the mite's host insects. If possible, clean storage areas thoroughly and treat with a pesticide, such as cyfluthrin. If necessary, stored commodities can be fumigated to disinfest them. Fumigation should be performed by persons holding the appropriate pesticide applicator's license or certification. Mite populations should decrease or completely disappear with the onset of the first frost. Many people believe the mites infest their beds or homes, but this is not true.

Poultry Mites Blood feeding mites of chickens and other birds; several species are involved (Dermanyssus gallinae, Ornithonyssus sylviarum) Occasionally feed on people; AKA poultryman’s itch

Poultry Mites Commonly associated with: English sparrows starlings pigeons Look for bird nests close to buildings chimney windows

Follicle Mites Demodex folliculorum Most humans are infested Occur in hair follicles around the eyes and nose Cause no discomfort to the host Similar mites cause demodectic mange in dogs Habitat: This mite lives in human hair follicles, the small sacs that surround the root of each hair. The mite might be found anywhere on the body but prefers the follicles of the face, the roots of eyelashes, and the oil glands of the forehead, nose, and chin. Diet: The hair follicle mite eats human skin cells. Behavior and reproduction: Follicle mites are common parasites and spend their entire lives on their human hosts. They live in hair follicles and eyelashes, burrowing head first into the root. They move onto the skin at night at rate of 0.4 inches (1 centimeter) per hour. Females may lay up to twenty-five oval eggs on one hair follicle. Young mites resemble adults. First-stage larvae (LAR-vee), or young mites, are legless, but later stages, before the mite becomes an adult, have six legs. Follicles may become tightly packed as the mite larvae grow. Adult mites leave follicles to mate and then find new follicles in which to lay eggs. The entire life cycle of the mite, from egg to adult, takes about fourteen to eighteen days. Hair follicle mites live in hair follicles and eyelashes, burrowing head first into the root. (©Andrew Syred/Photo Researchers, Inc. Reproduced by permission.) Hair follicle mites and people: Mites are basically harmless, and humans who harbor them often show no signs of infestation. Follicle mites are not known to transmit diseases, but large numbers in a single follicle may cause itching and other skin disorders, especially in the elderly.

Cable Mites Cause static to occur in TV broadcasts Infest coaxial cable resulting in a degradation of the cable line

Cable Mites (the real story) Not an actual species Some people think they are infested with mites or other insects Can be static electricity Allergic responses to chemicals or medication Delusory parasitosis "Paper Mites" and Other Unidentified Bites Complaints about bites and rashes for which a specific cause cannot be found are often attributed to so-called (and non-existent) "paper mites" or to one of the other mites mentioned above, particularly scabies and bird mites. Other biting/stinging pest such as fleas and bed bugs are easily seen and produce very noticeable and characteristic bites and other evidence of their feeding. Although mites are extremely small, they are usually detectable with the unaided eye (as in the case of bird mites) or by skin scrapings or other samples collected and examined by a physician. In the case of scabies and straw itch mites, the rash or bites that these mites leave aid in identifying them as the cause of the problem. Very often we unconciously and repeatedly scratch irritated areas of the skin (particularly at night while sleeping) and this will only worsen the condition. "Cable mites" and "paper mites" are often used as reasons to justify pesticide treatments in homes and offices. Pesticide applications made without first identifying a specific pest problem (and target application site) are usually ineffective and should not be used. More importantly, repeated and widespread pesticide applications are potentially hazardous to you and others around you. This includes constant (and multiple) applications of insect repellents and other insecticides to your skin (which can cause rashes and irritation) and to your clothing and/or bedding. You need to identify the cause of a problem before you resort to spraying any pesticides in your home. Here are some tips for collecting specimens for identification. Use mouse glueboards, or cockroach sticky traps (available at most hardware stores) as monitors. Keep track of where and when you place each one. Such information may be critical if mites or insects are found. Never use adhesive ("Scotch") tape to “trap” specimens on your skin. Key features that are important for pest identification can easily be damaged or obscured. Repeated scraping or gouging into your skin with razors, knives or other items in order to collect samples or "relieve" the symptoms can only worsen the problem and even result in an infection. Specimens containing bodily fluids, skin tissue, etc. should be collected and examined by a medical professional. Make sure that the vial/bottle is sealed tightly so that the contents do not leak. Use a fine artist paint brush to pick up the specimens. Place them carefully into a small prescription vial or bottle filled with alcohol (rubbing alcohol should work). Label the vial as to where you collected the specimen. Brush/knock suspected specimens from your clothing or skin onto a light-colored piece of paper or cardboard. If no insects or mites can be found, then you need to consider other possible causes for your symptoms. A previously unidentified (or recently developed) allergy or sensitivity may a mimic biting sensation and bite-like marks or rashes. These allergies can include: certain foods, chemicals (including laundry detergents), dust, pollen, as well as medications and health supplements. Even changes in your indoor environment (e.g., changes in humidity) and stressful situations can trigger skin reactions and sensitivities. For that reason, you should consult your family physician or a specialist such as a dermatologist or allergist.

Surveillance for Mites Very difficult to do Doctors can do skin scrapings from patients Black plate method Look for hosts (rats and birds) Detection The presence of house dust mites can be confirmed microscopically which requires collecting samples from mattresses, couches or carpets. Also, it requires the use of a microscope with sufficient magnification and the technical ability to recognize house dust mites under the microscope. This is a "dipstick-type" test similar to those sold in drugstores for glucose, etc. The test actually detects the presence of house dust mite feces. One must collect dust samples and mix a portion of the sample with reagents packed with the test. One then places the dipstick into the mixture, removes it, and compares the color change to a chart packed with the test. It will give an indication of the level of infestation. Keep test kits refrigerated. Contact drugstores and specialty shops dealing with water and air purification systems and related environmental control for the diagnostic kit.

Control Personal hygiene Chemical (permethrin, lindane, crotamiton, gamma-BHC) Chemical control presents problems due to dosage restrictions and development of resistance Personal protection (deet, permethrin) Sanitation Recommendations focus on "dust control." One must reduce the concentration of dust borne allergens in the living environment by controlling both allergen production and the dust which serves to transport it. For the bedroom environment: Replace feather and down pillows with those having synthetic fillings. Enclose the mattress top and sides with a plastic cover, thoroughly vacuuming mattress pillows and the base of the bed. Daily damp dust the plastic mattress cover. Weekly change and wash pillowcases, sheets, and under blankets, and vacuum the bed base and around the covered mattress. Replace woolen blankets with nylon or cotton cellulose ones. Frequently wash all bedding (blankets, mattress pads and comforters) in hot water (130 degrees F weekly). Also wash curtains. Remove carpet and replace with wood, tile, linoleum, or vinyl floor covering. (If you have carpet, vacuum every day.) Mattresses covered with "fitted sheets" help prevent the accumulation of human skin scales on the surface (an alternate to encasing mattresses and box springs in non-allergenic, impermeable, plastic covers). The application of frequent vacuuming as a dust control measure is more likely to aggravate allergic asthmatic conditions because conventional vacuums are very "inefficient." Dust collection by conventional vacuums results in a significant increase in air borne dust concentrations. Vacuuming is best accomplished by cleaners that entrain dust into a "liquid medium" such as water (rather than a dust bag), which reduces the suspension and dissemination of allergenic dust particles in the air. Some pest control firms sell air purifiers to eliminate the food source of house dust mites. Air purifiers emit a low level of ozone (activated oxygen). Ozone attaches to fungus, mold, and bacteria on skin flakes. Machines sell for around $625 and last up to 15 years. About the size of a bread box, an area up to 2,500 square feet is protected. There is no maintenance required other than a thorough cleaning once every three to four months. The air purifier is placed near a return for air conditioning or heating system or centrally located within the home. Various types of air purifiers can be attached to the central air return to decrease irritants. Most filters remove 50 to 70 percent of material. HEPA filters will remove up to 99 percent of the material. Indoor air quality is very important. (One needs to bring in fresh outside air rather than recirculating dirty air.) Some filters need to be changed monthly. Some feel it is important to focus on decreasing indoor humidity, especially during the winter period to reduce dust mite populations. One might forsake humidifier use during winter periods, use of dehumidifiers during high-humidity periods, or use of central air conditioning. Effective control of mites would require the maintenance of relative humidities below 50 percent (mites thrive in humid conditions). Homes that have their air conditioners on constantly have lower mite counts than non-air conditioned homes. Chemical Control No pesticides are currently labeled for house dust mites.

Summary Characteristics and Habits Life Cycle Medical Importance Control Measures

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