Medical Entomology Jin Liqun Department of Parasitology Shantou University Medical College

Medical Entomology (Medical Arthropodology )

Arthropod : (Phylum Arthropoda 节肢 动物门 ) These organisms are characterized by having of jointed legs, body segments,a hard outer covering or exoskeleton made of chitin （几丁质）.

Three important characteristics: 1 bilaterally symmetric body with jointed appendages. 2 chitinized exoskeleton. 3 hemocele: the body cavity serves as blood cavity simultaneously.

Classification Phylum Arthopoda contains the following Classes : Phylum Arthopoda contains the following Classes : 1 Insecta ( 昆虫纲、六足纲： insects), 1 Insecta ( 昆虫纲、六足纲： insects), 2 Arachnida ( 蛛形纲， spiders, mites, ticks, scorpions, etc), 2 Arachnida ( 蛛形纲， spiders, mites, ticks, scorpions, etc), 3 Chilopoda (centipedes ，唇足纲 ), 3 Chilopoda (centipedes ，唇足纲 ), 4 Diplopoda (milipedes ，倍足纲 ), and 4 Diplopoda (milipedes ，倍足纲 ), and 5 Crustacea ( 甲壳纲， crabs, shrimp, lobsters, water fleas, etc). 5 Crustacea ( 甲壳纲， crabs, shrimp, lobsters, water fleas, etc). * Arachnida （蛛形纲） * Arachnida （蛛形纲） * Insecta ( 昆虫纲、六足纲） * Insecta ( 昆虫纲、六足纲）

The impairment of arthropods to humans 1 Direct impairment: 1 Direct impairment: 1a : harassment and blood sucking 1a : harassment and blood sucking 1b: sting and inoculation of poison 1b: sting and inoculation of poison 1c: allergic reaction 1c: allergic reaction 1d: parasitism : such as myiasis, scabies, etc. 1d: parasitism : such as myiasis, scabies, etc.

Indirect impairment 1 Mechanical transmitting vector 1 Mechanical transmitting vector They play the role as a passive carrier of pathogens. They play the role as a passive carrier of pathogens. 2 Biological transmitting vector 2 Biological transmitting vector The arthropod is used by pathogens not only as a vehicle but also as an environment for development and/or reproduction to their infective stages. The arthropod is used by pathogens not only as a vehicle but also as an environment for development and/or reproduction to their infective stages.

How to judge an arthropod as a transmitting vector? ( four evidences) How to judge an arthropod as a transmitting vector? ( four evidences) 1 Biological evidence: 1 Biological evidence: ( closely related with humans, dominant species, longer life span ) ( closely related with humans, dominant species, longer life span ) 2 Epidemiological evidence 2 Epidemiological evidence (closely related with distribution epidemic region and season) (closely related with distribution epidemic region and season) 3 Evidence of natural infection 3 Evidence of natural infection ( pathogen isolated from the vector) ( pathogen isolated from the vector) Laboratory evidence Laboratory evidence (Artificial infection) (Artificial infection)

Ticks and mites Morphology: Morphology: Gnathosoma Gnathosoma ( 颚体、假头 ) ( 颚体、假头 ) Idiosoma ( 躯体 ) Idiosoma ( 躯体 ) 4 pairs of legs 4 pairs of legs (Adult) (Adult)

Life cycle Egg larva---- nymph （若虫） ---- adult Egg larva---- nymph （若虫） ---- adult

Hard tick Note: scutum on its back Male(left)Female(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 tick Without scutum

Ticks A female hard tick ’ s body may increase many times after its blood meal A female hard tick ’ s body may increase many times after its blood meal

The relationships with diseases Direct impairment: 1 sting and blood sucking 2 tick paralysis (caused by the poison of ticks to nervous system)

Indirect impairment: 1 Forest encephalitis ( viral disease) 2 Xinjiang hemorrhagic fever ( spirochaetal disease) 3 Lyme disease (spirochaetal disease) 4 Tick-borne relapsing fever(spirochaetal disease) 5 Q-fecver ( rickettsial disease) 6 North Asia tick-borne typhus ( rickettsial disease) 7 Others : bacterial diseases ( the plague, tularemia,etc.)

Scabies mite ( Sarcoptes scabei 疥螨 ) Scabies mite is the cause of scabies （疥疮 ） and is distributed worldwide Scabies mite is the cause of scabies （疥疮 ） and is distributed worldwide

scabies

Chiggers (Harvest mites 恙螨 ) Only Larva stages suck blood and transmit disease. Note: larva has 3 pairs of legs.

Life cycle EggprelarvalarvanymphPupa Nymph pupa adult

Relation to diseases 1 Dermatitis (trombidiosis ) 1 Dermatitis (trombidiosis ) * 2 Scrub typhus ( rickettsail disease) ( Tsutsugumashi disease 恙虫病 ) ( Tsutsugumashi disease 恙虫病 ) 3 hemorrhagic fever( viral disease ) 3 hemorrhagic fever( viral disease )

Demodex ( follicle mites) D. brevis ( in sebaceous gland) D. folliculorum (in hair follicle)

They are common mites found in humans. Opportunistic pathogenic mites in forehead, nose naso-labial groove, head skin, cheek and ear-hole etc. Folliculitis or skin lesion.

Medical insects (Insecta) Characteristics: The body: head, thorax and abdomen A pair of antennae Three pairs of legs (adult)

Metamorphosis( 变态 ) of insects All changes from larva to adult is called metamorphosis including morphology, physical functions,living habit, behavior and instinct All changes from larva to adult is called metamorphosis including morphology, physical functions,living habit, behavior and instinct

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

Morphology 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 moutnparts （口器） : Three types of moutnparts （口器） : 1 chewing mouthparts ( 咀嚼式， cockroach) 1 chewing mouthparts ( 咀嚼式， cockroach) 2 lapping mouthparts ( 舐吸式， housefly) 2 lapping mouthparts ( 舐吸式， housefly) 3 piercing-sucking mouthparts ( 刺吸式 mosquito) 3 piercing-sucking mouthparts ( 刺吸式 mosquito)

Thorax: Prothorax Mesothorax and Metathorax Three pairs of legs a pair of wings Abdomen: segmented Genitalia is important for identification Genitalia is important for identification

Mosquitoes Three important Genus: Anopheles Anopheles Aedes Aedes Culex Culex

Morphology

Anopheles

Aedes

Culex

Life cycle Complete metamorphosis: Egg --- larva ( 孑孓 ) ---- pupa ---- adult Egg --- larva ( 孑孓 ) ---- pupa ---- adult

Larvae and pupa

An. Cx. Ae. An. Cx. Ae. Egg boat-like conical fusiform Egg boat-like conical fusiform with float in raft single with float in raft single ( surface ) ( surface ) ( bottom ) ( surface ) ( surface ) ( bottom ) Larva 2 spiracles siphon siphon Larva 2 spiracles siphon siphon Palmate hair Palmate 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 place position) an angle to resting place to resting place to resting place

Relationships to diseases MalariaFilariasis Japanese B encephalitis Dengue fever ( viral disease) Others: Yellow fever, West Nile, etc.

Flies Mainly as mechanical transmitting vectors. Mainly as mechanical transmitting vectors. Complete metamorphosis. Complete metamorphosis.

Life cycle Egg larva( maggot 蛆 ) pupaadult

Feeding habit: Omnivorous(most) Blood sucking (a few) Eating frequently Vomiting and excreting simultaneously

Relationships to diseases *Mechanical transmitting vector: Bacterial, Bacterial, viral, protozoal diseases, viral, protozoal diseases, And helminthiasis. And helminthiasis.

Biological transmitting vector: Tsetse fly in Africa ( protozoon) * Myiasis : some flies ’ larvae parasite in human tissues or organs.

Lice Body louse Head louse Crab louse

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

Crab louse

Life cycle Egg (nit) --- nymph --- adult

Diseases: 1 Epidemic typhus （流行性斑疹伤寒） Rickettsial disease Rickettsial disease 2 Trench fever ( Quintan fever, 战壕热） ( Quintan fever, 战壕热） Rickettsial disease Rickettsial disease 3 Relapsing fever ( 回归热 ) ( 回归热 ) Spirochaetal disease Spirochaetal disease

Fleas Life cycle

Fleas Fleas 1 The plague ( black death) Yersiinia pestis( 鼠疫杆菌, 耶尔森氏菌 ) Yersiinia pestis( 鼠疫杆菌, 耶尔森氏菌 ) 2 Endemic typhus (rickettsial disease) 3 As intermediate host of some tapeworms

Sand fly

Two notorious spiders poisonous for humans. A: Black widow spider. Note “ hourglass ” on abdomen B: Brown spider. Note “ violin ” on cephalothorax

Blackflies( 蚋 ) are important transmitting vectors of onchocerciasis (river blindness) in Africa.