1. MITES
Of Medical Importance

2. MITES (Acari) Free-living Predacious Parasitic (endo/ecto)
How can they be distinguished from ticks?

3. Effects 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.

4. General Life Cycle Egg Prelarva Hexopod larvae Nymph Adult
May or may not feed.
Nymph
Protonymph, Deutonymph, Tritonymph
Adult
May take one or several meals.

5. Acariasis Infestation with mites (or ticks)
Some possible sites of infestation:
Respiratory passages and lungs.
External, inner and middle ear
Nasal passages
On and in the skin

6. Sarcoptidae “Scabies Mites”
Sarcoptes scabiei
Also called the “itch mite” of humans
It causes the “Seven Year Itch” or “Norwegian Itch”
Not Vectors of any disease.

7. Distribution Worldwide All races and socioeconomic classes
All climates
300 million cases annually!

8. Behavior 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).

9. Life Cycle

10. Transmission Spread by ovigerous female mites through:
Personal (prolonged close) contact
Occasionally by infested sheets (rare).
Touching or shaking hands (unlikely).
Sexual activity.
Among children (outbreaks).
Mites can survive up to 24 hours off host.

11. Recognition 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.

12. Scabies Rash

13. Rash Continued First time: 4-6 weeks incubation.
Second time: 2-4 days (reinfection).
Development of severe pruritus
Scratching at night, after hot baths.
Secondary infection
Boils
Pustules
Crusted Scabies: highly contagious (rare)

14. Diagnosis Scraping of skin Ink on skin Put on tetracycline Infestation
Most 1-15 adults
Avg. 11 adults
3% have more than 50
More than 1000! (Norwegian).

15. Treatment Lindane lotion for 12 hours. Sulphur Preparations (Mitigal)
Don’t shower first!
Shower first, treat later (Norwegian)
Sulphur Preparations (Mitigal)
1 treatment 100% effective, but mild dermatitis.
Modern acaracide (insecticides)
5% permethrin cream (Elimite, Lyclear)
1% aqueous malathion.
1% Kwell lotion

16. Trombiculidae “Scrub Typhus and Chigger Mites”
Around 3000 spp. Worldwide.
20 spp. Medically important (attack people).
We will discuss 3 of the species.

17. Chigger Mites “Harvest Mites or Red Bugs”
(1) Trombicula alfreddugesi
Distribution
Continental U.S. from New England to California (not north of Nebraska)
Second growth cutover areas
Moist microenv. Within grassy, weedy or wooded areas, especially wild berry patches.
Seasonality
Active May-September

18. US distribution of chiggers - other areas also have focally high populations
The Culprit
Larval chigger mite

19. Life Cycle Egg  Larvae (parasitic stage)  2 nymph stages  Adult.
Require humidity and a vertebrate host for larval stage.
Tissue feeders.
Digestive juices secreted into host
Reaction around chigger
Non-burrowing

20. Medical Importance Stay on host a couple of days.
Itching occurs 3-6 hours after exposure.
More of a nuisance due to intense irritation.
Treatment:
Bathing
Antiseptic

21. Chigger Mites “Harvest Mites or Red Bugs”
(2) Trombicula splenden
Distribution
Same story as T. alfreddugesi, but has a more southern distribution.
Seasonality
Active May-September for sure, but most likely is active longer or all year round.

22. Chigger Protection
Stay 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.

23. Chigger Protection
Immediately 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.

24. Scrub Typhus “Japanese River Fever”
Vector species:
Leptotrombidium deliense
L. akamushi (Japan)
L. fletcheri (Malaysia)
Pathogen:
Orientia tsutsugamushi (rickettsia)

25. Scrub 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, Australia
History:
WWII ( ) incidence in troops in the Asia-Pacific area was second only to malaria.

27. Epidemiology People infected folling bite of larval mite.
Visiting or working in mite islands.
Associated with fringe habitats
Habitats separating two major vegetation zones
Areas often heavily populated with rodent host.
Risk of transmission often related to habitat diversity.
Number of areas of different types of vegetation.

28. Life Cycle

29. Signs and Treatment
Abrupt 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)

30. Control/Prevention Repellents: Insecticides Protective clothing
DEET, dibutyl phthalate, dimethyl carbamate or benzyl benzoate.
Insecticides
Protective clothing
Permethrin on clothes.
Mechanical control

31. Miscellaneous Mites (1) Ornithonyssus bacoti (Tropical rat mite).
(2) Ornithonyssus sylviarum (Northern fowl mite).
(3) Dermanyssus gallinae (Chicken mite).
(4) Liponyssoides sanguineus (House mouse mite).
(5) Pyemotes tritci (Straw itch mite).
(6) Tyrophagus putrescentiae (Grocers itch mite).
(7) Cheyletiella spp. (Cheyletiellid mites)

32. Demodicidae “Follicle Mites”
Tenth to a fourth of a mm long.
2 species:
Demodex folliculorum
Demodex brevis

33. Dermatitis 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.
Acne
Eyelashes fall out
Invade living tissue (rare).

34. Pyroglyphidae “House-Dust Mites”
2 species we are
concerned with:
Dermatophagoides pteronyssinos (European
House Dust Mite)
Dermatophagoides
farinae (American

35. Biology Dust: More abundant in older homes Humidity:
Prefer mattress dust
Find in dust samples
Find in furniture and carpets
More abundant in older homes
Humidity:
75% relative humidity is optimum.
40-50% relative humidity is minimal.
Not common in more arid parts of the country.

36. Biology Continued Females lay 1-3 eggs/day.
Eggs hatch after 6-12 days.
Egg  Larvae  Nymph (2 instars) Adult.
Life cycle takes 3-4 weeks
Adults 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.

37. Allergies 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/Control
Severe allergy: can receive a series of injections (desensitizing vaccine)
Enclose mattress and pillows with plastic
Wash bedding above temp 55C or dry-cleaning
Leave electric blanket switched on max for 6 hours or more during the day.

38. Interesting Facts
House dust mites cause 25% of all allergies and 50% of all asthmatic diseases are traceable to house dust mites.

39. Areas at highest risk for dust mite problems.