Arthropods: AcariTicks and Mites

Phylum ArthropodaSubphylum CrustaceaSubphylum UniramiaSubphylum Chelicerata

Subphylum ChelicerataLarge, diverse group of arthropods

Includes horseshoe crabs, spiders, sea spiders, scorpionsMost have 4 pairs of legs

Some mites have one to three pairsExternal segmentation reducedTwo body parts

Capitulum (gnathosoma)Contains the mouthparts

IdiosomaLegs and tail

Most are free-living, non-parasitic Ticks and mites are parasitic

Class ArachnidaeSubclass Acari

Order IxodidaOrder MesostigmataOrder ProstigmataOrder OribatidaOrder Astigmata

Order IxodidaTicks

Hard ticksSoft Ticks

Four life cycle stages: egg, larva, nymph, adultMay have one to six nymphal instars

In many species, all stages are solenophagous ectoparasitesIn some, all instars are on one animal.In others, each instar finds a new host

Increases transmission of diseaseSome are host specific, some are opportunisticCan live as long as 16 years without blood meal!Life span may be as long 21 yearsVery complex behavior

Controlled by pheromones

Family IxodidaeHard TicksCapitulum is terminal and can be seen from abovePathology

AnemiaHost animal can lose 2000 pounds of blood in a season

DermatitisInflammation, swelling, ulceration and itching around bite

Tick ParalysisTick imbeds at base of skullToxic secretions released by tick causes swelling and temporary paralysis of hostParalysis disappears when tick is removed

Infection

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Many are important vectors of diseases in humans and domestic animals

Ixodes sp.Largest genus with 200 species

40 in North America Important vector of disease

Lyme Disease – caused by spirochaete Borrelais burgdorferiTick-borne encephalitisHuman granulocytic erlichiosis – caused by Erlichia sp. bacteria

Dermacentor sp.Most important genus medically30 species with 7 in North AmericaVector for several human diseases

Tick paralysisPowassan encephalitis virusColorado Tick FeverRocky Mountain Spotted FeverTularemia

Also vectors for disease among domestic animals

Hyalomma sp.Very difficult to identify to speciesFairly large ticksVery hardy

Found in deserts with little shelterWill bite humans and domestic animalsImportant vector for disease

Can be carried to other continents by migratory birdsCrimean-Congo hemorrhagic fever spreads between Africa and EuropeCarries West Nile VirusAlso can transmit Siberian tick typhus, boutenneuse fever, Q Fever, and Ehrlichiosis

Boophilus sp.Very small ticks when not engorgedSpread with the spread of the cattle industry

Primarily use cattle as hostsWill bite humans

Important vector for Texas Cattle Fever Caused by Babesia bigemina, a Protozoan related to the malarial parasitesNow eradicated in U.S.

Important vector for Crimean-Congo hemorrhagic fever and several other viruses in humans

Family ArgasidaeSoft ticksAbout 160 species totalNot vectors for diseaseFive genera

Antricola and Northaspis found on cave-dwelling bats in North and Central America

OrnithodorosOver 100 speciesParasitize mammals, including bats and humansVector for relapsing fever in humansO. cariaceus will give nasty bite to humans

Otobius – spinous ear ticksAdults do not feed; only mate, lay eggs and die

Argas

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Mostly parasites of birds and batsSpends time in animal’s beddingWill bite humans

Order MesostigmataEasily recognized by spiracle just behind third coxa of third pair of legsFour families are parasiticFamily Laelaptidae

Large number of diverse generaUsually Ectoparasite of mammals

Some on invertebratesDo not transmit disease to humans

May cause dermatitisFamily Halarachnidae

Parasite of the respiratory system of mammalsPneumonyssus sp. are found in primates

But not in humansRaillietea auris lives on ears of cattle

Lives on dead cells and secretions of ear

Family DermanyssidaeParasites of vertebratesVery important economically and medicallyDermanyssus gallinae – Chicken mite

Common on domestic fowlChickens, turkeys, pigeons

Feed at nightHide in crevices during the day.

Can kill chickens and chicks in large infestationsWill bite humansAttracted to warm objectsMay carry western and St. Louis equine encephalitis but transmission to mammals unlikely

Liponyssus sanguineus – House Mouse MiteFeed on mice but will bite humansTransmits Rickettsial pox to humans

Not fatal but makes you sick for weeksOrnithonyssus bacoti – Tropical Rat Mite

Most common in mice and ratsCan cause severe declines in laboratory rodents

Will attack humans with painful bite Some people develop severe dermatitis

Does not transmit diseases to humansDoes transmit filarial worm to rats

Family RhinonyssidaeAll are parasites in respiratory tract of birds

Nasal mitesFeed on blood and tissueProbably very important vector of disease in wild bird populations

Order ProstigmataSpiracle is variable in positionNot as hard (schlerotized) as other mitesMany feed on plants.

Only a few are parasitic on animalsAlso free-living forms in terrestrial and aquatic habitats

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Family CheyletidaeMost are yellow or reddish and round

Except mites on feathers which are elongatedCheyletiella yasguri – common on dogsC. blakei – common on catsBoth can cause mange dermatitis Rarely bite humans

Family PyemotidaeParasitize insects that feed on grainBite humans when they harvest grain or sleep on straw mats

Pyemotes tritici – straw itch miteFemales reach 1 mm in length

Males smallerNormal host is grain beetle but will bite people

Family PsorergatidaeSmall to medium size mitesCreate intense itchingPsorergates ovis – itch mite of sheepP. simplex – itch mite of miceP. bos – itch mite of cattle.

Family DemodicidaeFollicle mitesCigar-shaped, very small mites100-400 um long with stumpy legsHumans host two species

Demodex folliculusLive on hair follicles

Demodex brevisLive in sebaceous glands

Live mainly on face, particularly around nose and eye Little pathologyIncidence increases with age

Demodex canisSerious pathogen on dogsCauses Red Mange, with the help of bacterium Staphylococcus pyogenesCan be fatal in young dogs

Demodex canisSerious pathogen on dogsCauses Red Mange, with the help of bacterium Staphylococcus pyogenesCan be fatal in young dogs Dogs that recover may be permanently hairless!

Family TrombiculidaeChiggers1200 species

Most described from larvaAdults and nymphs are unknown for many species

Only larval stage are parasiticNymphs and adults feed on terrestrial invertebratesCause chigger dermatitisVector for disease

Adults are very large, covered in velvet-like setae and are red or yellow

Chigger Dermatitis

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Trombicula sp. in U.S,Leptotrombidium outside U.S.

Larvae do not burrow into skinMouthparts penetrate dermis and it injects salivary secretions

Particularly proteolytic enzymesDigests the cells

Secretions cause cells of host to harden into tubeLarvae sucks juices of digested cells until engorged and drop off

Bites are concentrated where clothes restrict chigger movementSome people are sensitive to the salivary secretions

Creates severe reaction around biteIntense itchingCan lead to secondary bacterial infections

Scrub TyphusCaused by Rickettsia tsutsugamushi, a bacteriumCarried by Leptotrombidium sp.Transmitted from adult female to larvae in eggWild rodents are reservoirFound in Southeast Asia, islands of the Indian and Pacific Ocean, and AustraliaSymptoms

Lesion forms around chigger biteEnlarges slowly to 8-12 mm with necrotic centerRash appears and spreads to extremitiesDelirium and other nervous disturbances followsMortality ranges from 6% to 60% without antibiotics

Order AstigmataLack tracheal system

Absorb oxygen through skinVery smallLittle hardening of exoskeleton

Soft bodiedVery important medically and economically

Frequently cause various types of mange in domestic animals

Family PsoroptidaeDo not burrow into skin

Pierce skin at base of hairsCauses inflamation that can be severe

Choroptic mangeCaused by Chorioptes bovis

Formerly divided into many species based on host it was on Most common feet and hind legsCan cause seminal degeneration in sheep

Family PsoroptidaeOtodectes sp.

Fairly common in dogs, cats, and other mammals.Live in the ears

Cause intense itchingPsoroptic mange

Caused by Psoroptes sp.Pierces skin and sucks exudateForms a scab that covers miteMites then thrive and reproduce into millions in a few daysCan greatly affect wool production

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Most common in wooly areaVery common in domestic animals and wild animals

Family SarcoptidaeSarcoptes scabiei

Has been divided into many species but probably all the same speciesCauses sarcoptic mange in mammals

Causes Scabies in humansWhen human comes in contact with mangy animal

Adults mate on host skinThen females burrow into skin

Males and nymphs stay on surfaceTunnels through the upper layer of skin, laying eggs and feedingLarvae crawl back out onto surface

Causes intense itching along burrowsCan result in secondary bacterial infection

Family PyroglyphidaeMost are free-livingMany cause house dust mite allergies

Live in the house, feeding on debrisMite parts, excrement are inhaled, resulting in allergic reaction

Dermatophagoides scheremetewskiCauses severe dermatitis on scalp, face, and ears of humansNormal host is probably sparrows, bats or other animals

Feather MitesFeed on feathers and lipids used to waterproof feathersWide variety of genera from many different orders of mitesCause very little damage and rarely carry diseaseVery important for taxonomy

Transferred from parent to offspringSpeciation occurs faster in mites than birds

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