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Mite Biology & Control

Female Scabies Mite

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Relate the biology of mites to appropriate control measures.

Objectiveهدف

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Overview مرور

Characteristics and Habits

Life Cycle

Medical Importance

Control Measures

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Mites

Not all mites are of medical importance. We will be concentrating on the following:

Scabies

Chiggers

Dust Mites

Rat Mites

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Mites

Other mites of some Importance

Forage Mites

Straw Itch Mites

Poultry Mites

Follicle Mites

Cable Mites

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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

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Biology

Have varied appearances and food sources

free-living predators

external parasites (most)

internal parasites (very few)

plant feeders

stored-products pests

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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

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Sarcoptes scabiei

variety hominis causes scabies in humans

variety suis causes swine mange

variety equi causes horse mange

Sarcoptic Itch Mites

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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 (Seven-year Itch)

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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

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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

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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

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Behavior

Once on the host the mite crawls around looking for a suitable feeding site

They love elastic

socks

briefs

bras

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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

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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

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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

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Dust Mites

Higher humidity levels are more conducive to mite survival

Mite populations are

present year round

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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

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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

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Tropical Rat Mite

Vector of Epidemic Hemorragic FeverDisease is probably viralRodent population forms reservoirCases documented in Korea

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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)

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Forage Mites

Allergic responses also can occur

Intestinal disturbances due to consumption of infested food can also be a problem

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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

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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

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Poultry Mites

Commonly associated with:

English sparrows

starlings

pigeons

Look for bird nests close to buildings

chimney

windows

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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

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Cable Mites

Cause static to occur in TV broadcasts

Infest coaxial cable resulting in a degradation of the cable line

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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

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Surveillance for Mites

Very difficult to do

Doctors can do skin scrapings from patients

Black plate method

Look for hosts (rats and birds)

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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)

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Summary

Characteristics and Habits

Life Cycle

Medical Importance

Control Measures

Prevent Disease, Disability and Premature Death

Questions?

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