2MITES (Acari) Free-living Predacious Parasitic (endo/ecto) How can they be distinguished from ticks?
3Effects on Humans Dermatitis or other tissue damage. Loss of blood or other tissue fluids.Transfer of pathogenic agents.Strong allergic reactions ($10 billion each yr.)Livestock: skin damage as much as $45 million worth each year.
4General Life Cycle Egg Prelarva Hexopod larvae Nymph Adult May or may not feed.NymphProtonymph, Deutonymph, TritonymphAdultMay take one or several meals.
5Acariasis Infestation with mites (or ticks) Some possible sites of infestation:Respiratory passages and lungs.External, inner and middle earNasal passagesOn and in the skin
6Sarcoptidae “Scabies Mites” Sarcoptes scabieiAlso called the “itch mite” of humansIt causes the “Seven Year Itch” or “Norwegian Itch”Not Vectors of any disease.
7Distribution Worldwide All races and socioeconomic classes All climates300 million cases annually!
8Behavior Burrowing initially occurs in thinner skin of the body. Bend of knee and elbow.Webbing between fingers and folds of the wrist.Genitalia and buttocks.Breasts.Bony projects (Norwegian scabies).
10Transmission Spread by ovigerous female mites through: Personal (prolonged close) contactOccasionally by infested sheets (rare).Touching or shaking hands (unlikely).Sexual activity.Among children (outbreaks).Mites can survive up to 24 hours off host.
11Recognition of Scabies Females narrow twisting tunnels.Feces in tunnels may be visible through skin.Severe itching (reaction to proteins)Genital lesions.Large rashes on body.Sores on body from scratching.Patients often dirty.
13Rash Continued First time: 4-6 weeks incubation. Second time: 2-4 days (reinfection).Development of severe pruritusScratching at night, after hot baths.Secondary infectionBoilsPustulesCrusted Scabies: highly contagious (rare)
14Diagnosis Scraping of skin Ink on skin Put on tetracycline Infestation Most 1-15 adultsAvg. 11 adults3% have more than 50More than 1000! (Norwegian).
16Trombiculidae “Scrub Typhus and Chigger Mites” Around 3000 spp. Worldwide.20 spp. Medically important (attack people).We will discuss 3 of the species.
17Chigger Mites “Harvest Mites or Red Bugs” (1) Trombicula alfreddugesiDistributionContinental U.S. from New England to California (not north of Nebraska)Second growth cutover areasMoist microenv. Within grassy, weedy or wooded areas, especially wild berry patches.SeasonalityActive May-September
18US distribution of chiggers - other areas also have focally high populations The CulpritLarval chigger mite
19Life Cycle Egg Larvae (parasitic stage) 2 nymph stages Adult. Require humidity and a vertebrate host for larval stage.Tissue feeders.Digestive juices secreted into hostReaction around chiggerNon-burrowing
20Medical Importance Stay on host a couple of days. Itching occurs 3-6 hours after exposure.More of a nuisance due to intense irritation.Treatment:BathingAntiseptic
21Chigger Mites “Harvest Mites or Red Bugs” (2) Trombicula splendenDistributionSame story as T. alfreddugesi, but has a more southern distribution.SeasonalityActive May-September for sure, but most likely is active longer or all year round.
22Chigger ProtectionStay out of areas where chiggers are likely to be present including woodlots, pastures, roadside ditches or other areas with tall grasses and weeds. Chiggers are especially common in moist low-lying areas.Wear loose-fitting clothing and avoid sitting or reclining on the ground when camping, picnicking or working outdoors.Apply a repellent containing DEET (N,N-diethyl-meta-toluamide) to shoes, socks and trousers before entering chigger-infested areas.
23Chigger ProtectionImmediately after possible exposure to chiggers take a bath, thoroughly scrubbing the body with hot soapy water. This will kill or dislodge many of the chiggers.When bites begin to itch, apply rubbing alcohol, followed by one of the non-prescription local anesthetics. A baking soda paste, calamine lotion or product such as "After-Bite" also will help reduce discomfort.Avoid scratching bites since this only increases irritation and may lead to secondary infection of the bite.Where chiggers are a problem in landscapes, keep lawns and shrubbery well manicured especially in areas adjacent to dwellings. Eliminate tall grasses and weeds. Chiggers also can be reduced by spraying infested foliage with carbaryl (Sevin), chlorpyrifos (Dursban) or diazinon.
25Scrub Typhus Reservoir – mites Zoonotic: humans are accidental hosts Transovarial transmission (also co-feeding transmission).Distribution – Japan, SE Asia and islands of Indian Ocean and SW Pacific, coastal North Queensland, AustraliaHistory:WWII ( ) incidence in troops in the Asia-Pacific area was second only to malaria.
27Epidemiology People infected folling bite of larval mite. Visiting or working in mite islands.Associated with fringe habitatsHabitats separating two major vegetation zonesAreas often heavily populated with rodent host.Risk of transmission often related to habitat diversity.Number of areas of different types of vegetation.
29Signs and TreatmentAbrupt onset of high fever ( °F), severe headache, myalgia, and eschar with tender regional lymphadenopathy.Approximately 35% of patients develop a centrifugal macular rash on the trunk.A small number of patients have CNS involvement, with tremors, nervousness, slurred speech, nuchal rigidity, or deafness during, the second week of the disease.Treat with antibiotics such as Tetracycline, Doxycycline, Chloramphenicol. (14 days)
30Control/Prevention Repellents: Insecticides Protective clothing DEET, dibutyl phthalate, dimethyl carbamate or benzyl benzoate.InsecticidesProtective clothingPermethrin on clothes.Mechanical control
32Demodicidae “Follicle Mites” Tenth to a fourth of a mm long.2 species:Demodex folliculorumDemodex brevis
33Dermatitis Very common Usually on skin of face, especially the eyelash and nose.20% of individuals age years is infested.100% of the aged have them.In most cases they seem to be beneficial to us.Saprophytic mites are benign except when they invade the dermis, causing dermatitis.AcneEyelashes fall outInvade living tissue (rare).
34Pyroglyphidae “House-Dust Mites” 2 species we areconcerned with:Dermatophagoides pteronyssinos (EuropeanHouse Dust Mite)Dermatophagoidesfarinae (American
35Biology Dust: More abundant in older homes Humidity: Prefer mattress dustFind in dust samplesFind in furniture and carpetsMore abundant in older homesHumidity:75% relative humidity is optimum.40-50% relative humidity is minimal.Not common in more arid parts of the country.
36Biology Continued Females lay 1-3 eggs/day. Eggs hatch after 6-12 days.Egg Larvae Nymph (2 instars) Adult.Life cycle takes 3-4 weeksAdults live for 1-2 months.Typically 300 mites per/gram of house dust.Under ideal conditions (5000 mites/gram dust)Record (15,600 mites/gram dust)Above 100 mites/gram dust is considered a risk.
37Allergies The exoskeleton and body parts have a common antigen. People who are allergic to dust are also allergic to mites.Have been linked to respiratory disease such as asthma.Treatment/ControlSevere allergy: can receive a series of injections (desensitizing vaccine)Enclose mattress and pillows with plasticWash bedding above temp 55C or dry-cleaningLeave electric blanket switched on max for 6 hours or more during the day.
38Interesting FactsHouse dust mites cause 25% of all allergies and 50% of all asthmatic diseases are traceable to house dust mites.