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Medical Arthropodology Department of Parasitology Xiang-Ya School of Medicine


I

Concepts

ď ą Arthropod species , about a few hundred million, accounting for dynamic 87% of the total number of material types, hazard to human health is only a tiny minority. ď ą Medical arthropods (mainly medical insects) refer to those arthropods with medical importance; ď ą Parasitic arthropods are those being able to either directly impair to human health by their toxic substances or indirectly harm through spread of pathogens.


I

Concepts

ď ą Medical arthropodology or Medical entomology is to research on: morphological characters, classification, life cycle, ecology, geographical distribution, pathogenesis, regularity of disease transmission and control strategies of medical pests


I

Concepts

Medical arthropods closely related with human life include: mosquito, fly, sandfly, flea, louse, cockroach, bed bug, hard tick, soft tick, gamasid mite, itch mite, follicle mite, etc. The most harmful pests in China are mosquito, fly and cockroach.


II Main conmmon characters of arthropods

insecta

arachnida

Morphological characters of arthropods


II Main conmmon characters of arthropods

 Bilaterally symmetric;  Segmented body with appendageson each segment;  Covered by exoskeleton made out of chitin, a polysaccharide, and quinone tanned protein;

 A dorsal heart with open circulatory system (also named as hemocele) containing blood haemolymphand a nervous system on the ventral side of body;

 Molting (ecdysis ) and metamorphosis during development history


III Classification of Arthropods Insecta: mosquitoes, flies, sandflies, fleas, black flies, biting midges, tabanid flies, lice, cockroaches, bedbugs, etc;

Phylum Arthropoda

Arachnida: hard ticks, soft ticks, itch mites, chigger mites, gamasid mites, follicle mites, dust mites, etc; Crustacea: crabs, shrimps, cyclops, diaptomus, etc; Chilopoda: centipedes, etc; Diplopoda: millipedes, etc.


III Morphological characters 1 Insecta: Separated head, thorax and abdomen; 3 pairs of legs, 1 pair of antennae.

2 Arachnida: Cephalothorax and abdomen; Or head, thorax and abdomen combining into a whole; 4 pairs of legs, without antenna and wing.


III Morphological characters 3 Crustacea: Cephalothorax ; Abdomen ( 5 pairs of legs, 2 pairs of antennae ) ; Mostly live in water. shrimp, crab, cyclops


III Morphological characters 4 Chilopoda : head and long, slender, flat body segments; 1 pair of antennae, 1 pair of legs on every segment. centipede


III Morphological characters 5 Diplopoda: head and long pipeshaped body segments; 1 pair of antennae, 2 pairs of legs on every segment. diplopod


fly

mosquito


sandfly


flea


black fly

biting midge

tabanid fly


2-4 mm

louse 1.5-2 mm


Cockroach bed bug


hard tick soft tick


itch mite


chigger mite


gamasid mite

dust mite follicle mite


IV Metamorphosis: A series of changes on external morphological characters, structures, physiological functions, life habit, behaviour and instinct during the development of an insect from egg to adult.


IV Metamorphosis 1 complete metamorphosis has pupa stage

emergence

adult

pupa

eggs eclosion

pupation

larva


IV Metamorphosis 2 incomplete metamorphosis doesn’t experience pupa stage

adult

nymph

egg


IV Metamorphosis 3 paurometamorphosis: Larva (six legs) 5-7 instar blood meals

eggs

nymph adult


V Harmful effects on human 1 Direct harmful effects :

ď ą Annoyance resulted from sting and bites ď ą Envenomization and damage by toxic substance


V Harmful effects on human 1 Direct harmful effects : 

Allergic reaction : resulted from heterogeneous proteins, just as saliva, secretions , excretions , and hull, etc. from arthropods

Direct parasitism : myiasis: caused by larval flies parasiting in human body) ; tungiasis: caused by tunga ; scabies: caused by itch mites ; demodicidosis: caused by follicle mite


Major diseases caused by direct injury of arthropods Names of diseases

Arthropod pathogens

Lesion sites

Mechanisms

Allergic asthma and rhinitis

Dust mites

Respiratory system

Allergic reaction

Scabies

Itch mites

Skin

Direct parasitism of itch mites

Demodicidosis

Follicle mites

Skin or viscera

Direct parasitism of follicle mites

Tick paralysis

Some hard tick species

Nerve system

Nerve toxicity

Tungiasis

Some flea species

Skin

Direct parasitism of fleas

Myiasis

Dipterous larvae (especially fly maggots)

Skin, eyes and digestive tracts, etc.

Direct parasitism of the larvae.


Symptom of patients with scabies


V Harmful effects on human 2 Indirect harmful effects - disease transmision: the major harmful effects of arthropods *vectors ďźš arthropods capable of transmitting pathogens are called vectors *vector-borne diseases: the diseases transmitted by arthropod vectors


V Harmful effects on human 2 Disease transmision : ď ą

Mechanical transmission transfer of a pathogen from an infectious source to a susceptible host by an arthropod vector, without any reproduction and development of the pathogen in the vector

ď ą

biological transmission the pathogen either reproduces or develops (or both) in the vector, include developmental biological transmission, propagative biological transmission, cyclopropagative biological transmission (both developing and multiplying in the vector) and transovarial biological transmission


V Harmful effects on human 2 Disease transmision : a) developing : developmental biological transmission: the pathogenic organisms having a period of development in the arthropod vectors (eg, when mosquitoes transmit filaria) b) multiplying : propagative biological transmission: the pathogens multiplying in the vectors (eg, when fleas transmit plague)


V Harmful effects on human 2 Disease transmision : c) developing and multiplying : cyclopropagative biological transmission with the pathogens both developing and multiplying in the vectors (eg, when mosquitoes transmit malaria) d) transmitting through eggs : transovarial biological transmission with the pathogens being transferred to the next generation of vectors through their eggs (eg, when ticks and mites transmit some viruses)


Major pathogens mechanically transmitted by arthropods Pathogens Virus Poliovirus

Arthropod vectors

Diseases

Flies and cockroaches

Poliomyelitis

Bacillus anthracis

Tabanidae

Anthrax

Salmonella

Flies, cockroaches

Salmonellosis

Shigella

Flies

Shigellosis

Vibrio cholerae

Flies

Cholera

Flies and eye gnats

Yaws

Entamoeba histolytica

Flies and cockroaches

Amebic dysentery

Toxoplasma gondii

Cockroaches

Toxoplasmosis

Bacterium

Spirochete Treponema pertenue

Protozoa


Major pathogens biologically transmitted by arthropods Pathogens Virus

Arthropod vectors

Diseases

JEV

Culex, Anopheles & Aedes

Dengue virus

Aedes

Dengue fever & dengue hemorrhagic fever

YF virus

Aedes

Yellow fever

Sand fly fever virus

Phlebotomus

Sand fly fever

Forest encephalitis virus

Ixodes

Forest encephalitis (Russian spring-summer encephalitis)

CCHF virus (XHF virus) Ixodes Hantaan virus

Some gamasid mites and chigger mites

Epidemic type B encephalitis

Xinjiang haemorrhagic fever (XHF) or Crimean-Congo hemorrhagic fever Hemorrhagic fever with renal syndrome (HFRS)


Rickettsia Rickettsia prowazekii

Pediculus humanus

Epidemic typhus

Bartonella quintana

Pediculus humanus

Trench fever

Rickettsia typhi (R. mooseri)

Siphonaptera

Endemic typhus

Rickettsia tsutsugamushi (R. orientalis)

Leptotrombidium

Tsutsugamushi disease

Siphonaptera

Plague

Borrelia recurrentis

Pediculus humanus

Epidemic relapsing fever (louse-borne relapsing fever)

Borrelia burgdorferi

Ixodes

Lyme disease

Borrelia persica, B. latyschevi & B. hermsii, etc.

Ornithodoros (soft tick)

Bacterium Yersinia pestis

Spirochete

Endemic relapsing fever (Tick-borne relapsing fever)


Protozoa Plasmodium (P. vivax, P. falciparum, P. malariae & P. ovale)

Anopheles

Malaria

Trypanosoma

Glossina

Trypanosomiasis (sleeping sickness)

Leishmania

Phlebotomus

Leishmaniais

Wuchereria brancrofti

Culex, Anopheles & Aedes

Bancroftian filariasis

Brugia malayi

Anopheles & Aedes

Brugian filariasis

Onchocerca volvulus

Simulium

Onchocerciasis

Loa loa

Chrysops

Loiasis

Dipetalonema perstans, D. streptocerca & Mansonella ozzardi

Culicoides

Three types of filariasis

Thelazia callipaeda

House flies

Thelaziasis

Nematode


Section 1 Culicidae / mosquito


I Classification and morphology 1 Classification Insecta Diptera Culicidae

Anopheles

Culex

Aedes


Anopheles sinensis

Culex pipiens pallens Aedes albopictus


2 Morphological features piercing-sucking mouthpart palp antenna compound eye

Femur

体分头胸腹,窄长翅一 对

Tibia

Tarsus

三对细长足,一根尖细 喙 翅脉和翅缘,都有鳞片


Piercing- sucking mouthparts


II Life cycle females feed on blood

30-300 eggs oviposited

adults live 1-3 weeks

wiggler

require water for development


Anopheles

Culex

Aedes


III Ecological behaviors 1 Breeding places depend upon egg-laying behaviors a) paddy-field type : b) slow stream type : c) jungle type : d) sullage type : e) container type :


III Ecological behaviors 2 Habitat humid and dark areas a) domestic roosting mosquitoes b) semi-domestic roosting mosquitoes c) wild roosting mosquitoes


III Ecological behaviors 3 Host preference female mosquitoes: blood meal male mosquitoes : feed on the nectar of flowers or other suitable sugar source human blood domestic animal blood


IV Medical significance

ď ś direct harm: disturbance, succking blood

ď śindirect harm ( biological transmission) mosquito-borne disease malaria

Anopheles

filariasis epidemic encephalitis B Dengue fever Yellow fever

Anopheles, Culex and Aedes Cx.tritaeniorhynchus Aedes aegypti/ albopictus Aedes aegypti


IV Medical significance Malaria is transmitted by Anopheles Filariasis is transmitted by Anopheles, Culex and Aedes Epidemic encephalitis B transmitted by Gulex Dengue fever transmitted by Aedes


V Prevention and control Environment management Physical control Chemical control Biological control Genetic control


Fly


I Classification and morphology 1 Classification Insecta Diptera Cyclorrhapha

Muscidae

Calliphoridae

Sarcophagidae

Oestridae


Chrysomyia megacephala

Boettcherisca peregrina

Lucilia sericata

Musca domestica vicina


I Classification and morphology 2 morphological feature a) 2 large compound eyes separated to wider spacing in female ,narrower spacing in male; 3 ocelli b) 2 antennae with each has a special structure called arista c) lapping mouthpart d) most developed mesothorax , 2 wide and well developed wings e) 3 pairs of legs, and each leg has a claw pad with lots of tiny thin hairs


lapping mouthparts


claw pad (pulvillus)


II Life cycle adult

pupa

egg

Larva (maggot)


egg

pupa


Larva of Chrysomyia megacephala spiracles of Chrysomyia megacephala


III Ecological behaviors 1 Breeding place The larvae of most flies feed on organic substance, and usually select the following sites as their breeding places : feces, garbage, putrid plants and decaying flesh , etc.


III Ecological behaviors 2 Feeding habit a)

unable to feed themselves: Oestridae

b)

sucking blood: Stomoxys calcitrans ďźŒ tsetsefly

c)

omnivorous: most flies with lapping mouthparts are feeding on a variety of food, including feces, decaying animals or plants, excretory substance and humans’ food, etc.

vomit / excrete while eating


IV Medical significance mechanical transmission: biological transmission: tissue invasion and parasitism:

Myiasis


dermamyiasis


11 arthropods  
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