Medical EntomologyMedical Entomology

Jin LiqunJin LiqunDepartment of ParasitologyDepartment of ParasitologyShantou University Medical CollegeShantou University Medical Collegelqjin@stu.edu.cnlqjin@stu.edu.cn

Medical EntomologyMedical Entomology(Medical Arthropodology )(Medical Arthropodology )

Arthropod :Arthropod : (Phylum Arthropoda(Phylum Arthropoda 节肢节肢动物门动物门 ) )

These organisms are characterized by havinThese organisms are characterized by having of jointed legs, body segments ,a hard outg of jointed legs, body segments ,a hard outer covering or er covering or exoskeletonexoskeleton made of made of chitinchitin（（几丁质）几丁质） . .

Three important Three important characteristics:characteristics:

1 bilaterally symmetric body with jointed appen1 bilaterally symmetric body with jointed appendages.dages.

2 chitinized exoskeleton .2 chitinized exoskeleton .3 hemocele: the body cavity serves as blood cavit3 hemocele: the body cavity serves as blood cavit

y simultaneously.y simultaneously.

ClassificationClassification Phylum Arthopoda contains the following Classes : Phylum Arthopoda contains the following Classes : 1 Insecta 1 Insecta (( 昆虫纲、六足纲： 昆虫纲、六足纲： insects), insects), 2 Arachnida2 Arachnida ( ( 蛛形纲，蛛形纲， spiders, mites, ticks, scorpispiders, mites, ticks, scorpi

ons, etc), ons, etc), 3 Chilopoda (centipedes 3 Chilopoda (centipedes ，唇足纲，唇足纲 ),), 4 Diplopoda (milipedes4 Diplopoda (milipedes ，倍足纲，倍足纲 ), and ), and 5 Crustacea (5 Crustacea ( 甲壳纲，甲壳纲， crabs, shrimp, lobsters, watcrabs, shrimp, lobsters, wat

er fleas, etc). er fleas, etc). * Arachnida * Arachnida （蛛形纲）（蛛形纲） * Insecta (* Insecta ( 昆虫纲、六足纲） 昆虫纲、六足纲）

The impairment of arthropods to The impairment of arthropods to humanshumans

1 Direct impairment:1 Direct impairment: 1a : harassment and blood sucking1a : harassment and blood sucking 1b: sting and inoculation of poison1b: sting and inoculation of poison 1c: allergic reaction1c: allergic reaction 1d: parasitism : such as myiasis, sca1d: parasitism : such as myiasis, sca

bies, etc. bies, etc.

Indirect impairmentIndirect impairment

1 Mechanical transmitting vector1 Mechanical transmitting vector They play the role as a passive carrier They play the role as a passive carrier

of pathogens.of pathogens. 2 Biological transmitting vector2 Biological transmitting vector The arthropod is used by pathogens The arthropod is used by pathogens

not only as a vehicle but also as an ennot only as a vehicle but also as an environment for development and/or revironment for development and/or reproduction to their infective stages.production to their infective stages.

How to judge an arthropod as a How to judge an arthropod as a

transmitting vector?transmitting vector? ( four evidences)( four evidences)

1 Biological evidence:1 Biological evidence: ( closely related with humans, dominant specie( closely related with humans, dominant specie

s, longer life span )s, longer life span ) 2 Epidemiological evidence2 Epidemiological evidence (closely related with distribution epidemic regio(closely related with distribution epidemic regio

n and season)n and season) 3 Evidence of natural infection3 Evidence of natural infection ( pathogen isolated from the vector)( pathogen isolated from the vector) Laboratory evidenceLaboratory evidence (Artificial infection) (Artificial infection)

Ticks and mitesTicks and mites

Morphology:Morphology: GnathosomaGnathosoma (( 颚体、假头 颚体、假头 )) Idiosoma (Idiosoma ( 躯躯

体体 )) 4 pairs of legs4 pairs of legs (Adult)(Adult)

Life cycleLife cycle

Egg ----- larva---- nymphEgg ----- larva---- nymph （若虫）（若虫） ---- adul---- adultt

Hard tickHard tick

Note: scutNote: scutum on itum on its backs back

Male(left)Male(left)FemaleFemale(right)(right)

Gnathosoma of hard ticks. (a) dorsal view. (b) Ventral view.Note hypostome ( 口下板 ). pedipalps

( 须肢 ). The mouthparts （口器） is composed of chelicerae( 螯肢 ) and hypostome.

Soft tickSoft tick

Without scutumWithout scutum

Ticks Ticks

A female harA female hard tick’s bod tick’s body may incredy may increase many tiase many times after its mes after its blood mealblood meal

The relationships with The relationships with diseasesdiseases

Direct impairment:Direct impairment:1 sting and blood sucking1 sting and blood sucking2 tick paralysis (caused by the poison 2 tick paralysis (caused by the poison

of ticks to nervous system)of ticks to nervous system)

Indirect impairment:Indirect impairment:

1 Forest encephalitis ( viral disease)1 Forest encephalitis ( viral disease)2 Xinjiang hemorrhagic fever ( spirochaetal diseas2 Xinjiang hemorrhagic fever ( spirochaetal diseas

e)e)3 Lyme disease (spirochaetal disease)3 Lyme disease (spirochaetal disease)4 Tick-borne relapsing fever(spirochaetal disease)4 Tick-borne relapsing fever(spirochaetal disease)5 Q-fecver ( rickettsial disease)5 Q-fecver ( rickettsial disease)6 North Asia tick-borne typhus ( rickettsial disease)6 North Asia tick-borne typhus ( rickettsial disease)7 Others : bacterial diseases ( the plague, tularemia,7 Others : bacterial diseases ( the plague, tularemia,

etc.)etc.)

Scabies mite (Scabies mite (Sarcoptes scabei Sarcoptes scabei 疥螨疥螨 ))

Scabies mite is the Scabies mite is the cause of scabies cause of scabies （疥疮 ）（疥疮 ） and is distriand is distributed worldwide buted worldwide

scabiesscabies

Chiggers (Harvest mitesChiggers (Harvest mites 恙螨恙螨 ))

Only Larva stages suck blood and tra

nsmit disease . Note: larva has 3 pairs of legs.

Life cycleLife cycle

EggEggprelarvaprelarvalarva larva nymph nymph PupaPupaNymph pupa Nymph pupa adultadult

Relation to diseases Relation to diseases

1 Dermatitis (trombidiosis )1 Dermatitis (trombidiosis )* 2 Scrub typhus ( rickettsail disease)* 2 Scrub typhus ( rickettsail disease) ( Tsutsugumashi disease( Tsutsugumashi disease 恙虫病恙虫病 )) 3 hemorrhagic fever( viral disease3 hemorrhagic fever( viral disease))

Demodex ( follicle mites)Demodex ( follicle mites)

D. brevis

( in sebaceous gland)

D. folliculorum

(in hair follicle)

They are common mites found in humThey are common mites found in humans.ans.

Opportunistic pathogenic mites in foreOpportunistic pathogenic mites in forehead , nose naso-labial groove, head head , nose naso-labial groove, head skin, cheek and ear-hole etc.skin, cheek and ear-hole etc.

Folliculitis or skin lesion.Folliculitis or skin lesion.

Medical insects (Insecta)Medical insects (Insecta)

Characteristics:Characteristics:

The body: head , thorax and The body: head , thorax and abdomen abdomen

A pair of antennaeA pair of antennae

Three pairs of legs (adult)Three pairs of legs (adult)

Metamorphosis(Metamorphosis( 变态变态 ) ) of insof insectsects All changes from larva to adult is calAll changes from larva to adult is cal

led metamorphosis including morphled metamorphosis including morphology, physical functions,living habit,ology, physical functions,living habit, behavior and instinct behavior and instinct

Complete metamorphosis :Complete metamorphosis : Four stages in the life cycleFour stages in the life cycle(egg --- larva ---- pupa (egg --- larva ---- pupa 蛹蛹 --- adult)--- adult)Incomplete metamorphosis :Incomplete metamorphosis :Without pupal stage.Without pupal stage.

MorphologyMorphology

Head: Head: A pair of antennae ( olfactory and tactile sensation)A pair of antennae ( olfactory and tactile sensation) A pair of compound eyes, some with single eyes( ocelli )A pair of compound eyes, some with single eyes( ocelli ) Three types of moutnpartsThree types of moutnparts （口器）（口器） :: 1 chewing mouthparts (1 chewing mouthparts ( 咀嚼式，咀嚼式， cockroach)cockroach) 2 lapping mouthparts (2 lapping mouthparts ( 舐吸式，舐吸式， housefly)housefly) 3 piercing-sucking mouthparts (3 piercing-sucking mouthparts ( 刺吸式刺吸式 mosquito)mosquito)

ThoraxThorax::

Prothorax Mesothorax and MetathoraxProthorax Mesothorax and MetathoraxThree pairs of legsThree pairs of legsa pair of wingsa pair of wingsAbdomen: Abdomen: segmented segmented Genitalia is important for identificationGenitalia is important for identification

MosquitoesMosquitoes

Three imporThree important Genus:tant Genus:

AnophelesAnopheles AedesAedes CulexCulex

MorphologyMorphology

AnophelesAnopheles

AedesAedes

CulexCulex

Life cycleLife cycle

Complete metamorphosis:Complete metamorphosis:

Egg --- larva Egg --- larva (( 孑孓孑孓 )) ---- pupa ---- adult ---- pupa ---- adult

Larvae and pupaLarvae and pupa

An. Cx. Ae.An. Cx. Ae. Egg boat-like conical fusiform Egg boat-like conical fusiform with float in raft singlewith float in raft single ( surface ) ( surface ) ( bottom )( surface ) ( surface ) ( bottom ) Larva 2 spiracles siphon siphonLarva 2 spiracles siphon siphon Palmate hairPalmate hair (float hairs)(float hairs)

Adult scales Adult scales (resting body forms body is parallel (resting body forms body is parallel position) an angle to resting placeposition) an angle to resting place to resting placeto resting place

Relationships to Relationships to diseasesdiseases

MalariaMalariaFilariasisFilariasisJapanese B encephalitisJapanese B encephalitisDengue fever ( viral disease)Dengue fever ( viral disease)Others: Yellow fever, West Nile, etc.Others: Yellow fever, West Nile, etc.

FliesFlies

Mainly as mechanMainly as mechanical transmitting ical transmitting vectors.vectors.

Complete metamComplete metamorphosis.orphosis.

Life cycleLife cycleEgg Egg

larva( maggotlarva( maggot 蛆蛆 ) )

pupa pupa

adultadult

Feeding habit:Feeding habit:Omnivorous(most)Omnivorous(most)Blood sucking (a few)Blood sucking (a few)Eating frequentlyEating frequentlyVomiting and excreting simultaneouslyVomiting and excreting simultaneously

Relationships to Relationships to diseases diseases *Mechanical tr*Mechanical tr

ansmitting vansmitting vector:ector:

Bacterial, Bacterial, viral, protozoviral, protozo

al diseases,al diseases, And helminthAnd helminth

iasis.iasis.

Biological transmitting vector:Biological transmitting vector:Tsetse fly in Africa ( protozoon)Tsetse fly in Africa ( protozoon)

* Myiasis : some flies’ larvae parasite * Myiasis : some flies’ larvae parasite in human tissues or organs.in human tissues or organs.

Lice Lice

Body louse Body louse

Head louse Head louse

Crab louse Crab louse

Head louseHead louse

* The body louse is similar to the head louse except that it is found on the body and clothes.

Crab louseCrab louse

Life cycleLife cycle

Egg (nit) --- nymph --- adult Egg (nit) --- nymph --- adult

Diseases:Diseases:1 Epidemic typhus1 Epidemic typhus

（（流行性斑疹伤寒）流行性斑疹伤寒） Rickettsial disease Rickettsial disease

2 Trench fever2 Trench fever ( Quintan fever , ( Quintan fever , 战壕热战壕热） ） Rickettsial disease Rickettsial disease

3 Relapsing fever3 Relapsing fever (( 回归热回归热 ) ) Spirochaetal diseaseSpirochaetal disease

FleasFleas

Life cycleLife cycle

FleasFleas

1 The plague ( black death)1 The plague ( black death) Yersiinia pestis(Yersiinia pestis( 鼠疫杆菌鼠疫杆菌 , , 耶尔森氏耶尔森氏

菌菌 ))2 Endemic typhus (rickettsial diseas2 Endemic typhus (rickettsial diseas

e) e) 3 As intermediate host of some tape3 As intermediate host of some tape

wormsworms

Sand flySand fly

Two notorious spiders poisonous for humans.

A: Black widow spider. Note “hourglass” on abdomenB: Brown spider . Note “violin” on cephalothorax

Blackflies(Blackflies( 蚋蚋 ) are important transmitting vector) are important transmitting vectors of onchocerciasis (river blindness) in Africa.s of onchocerciasis (river blindness) in Africa.