Medical Arthropodology

Department of Parasitology

Xiang-Ya School of Medicine

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.

Medical arthropods (mainly medical insects) refer to those

arthropods with medical importance;

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

I Concepts

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

The most harmful pests in China are mosquito, fly and cockroach.

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.

I Concepts

Morphological characters of arthropods

II Main conmmon characters of arthropods

insecta arachnida

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

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 Classification of Arthropods

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

2 Arachnida:

Cephalothorax and abdomen;

Or head, thorax and abdomen combining into a whole;

4 pairs of legs, without antenna and wing.

1 Insecta: Separated head, thorax and abdomen;

3 pairs of legs, 1 pair of antennae.

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 pipe-shaped body segments;

1 pair of antennae,

2 pairs of legs on every segment.

diplopod

III Morphological characters

fly

mosquito

sandfly

flea

black fly

biting midge tabanid fly

2-4 mm

1.5-2 mm

louse

bed bug

Cockroach

soft tick

hard tick

itch mite

chigger mite

follicle mite

gamasid mite

dust 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.

adultpupa

larva

eggs

IV Metamorphosis1 complete metamorphosis has pupa

stage

eclosion pupation

emergence

eggnymph

adult

IV Metamorphosis2 incomplete metamorphosis doesn’t experience pupa stage

eggs

Larva (six legs)

5-7 instarblood meals

nymphadult

IV Metamorphosis3 paurometamorphosis:

Annoyance resulted from sting and

bites

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

V Harmful effects on human

1 Direct harmful effects :

Major diseases caused by direct injury of arthropods

Names of diseases

Arthropod pathogens Lesion sites Mechanisms

Allergic asthma and rhinitis

Dust mitesRespiratory system

Allergic reaction

Scabies Itch mites SkinDirect parasitism of itch mites

Demodicidosis Follicle mites Skin or visceraDirect parasitism of follicle mites

Tick paralysisSome hard tick species

Nerve system Nerve toxicity

Tungiasis Some flea species SkinDirect parasitism of fleas

MyiasisDipterous 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：

arthropods capable of transmitting pathogens are called vectors

*vector-borne diseases:

the diseases transmitted by arthropod vectors

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

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)

V Harmful effects on human

2 Disease transmision :

Major pathogens mechanically transmitted by arthropods

PathogensArthropod

vectorsDiseases

Virus

Poliovirus Flies and cockroaches Poliomyelitis

Bacterium

Bacillus anthracis Tabanidae Anthrax

Salmonella Flies, cockroaches Salmonellosis

Shigella Flies Shigellosis

Vibrio cholerae Flies Cholera

Spirochete

Treponema pertenue Flies and eye gnats Yaws

Protozoa

Entamoeba histolytica Flies and cockroaches Amebic dysentery

Toxoplasma gondii Cockroaches Toxoplasmosis

Major pathogens biologically transmitted by arthropods

PathogensArthropod

vectorsDiseases

Virus

JEV Culex, Anopheles & Aedes

Epidemic type B encephalitis

Dengue virus AedesDengue 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) IxodesXinjiang haemorrhagic fever (XHF) or Crimean-Congo hemorrhagic fever

Hantaan virus Some gamasid mites and chigger mites

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

Bacterium

Yersinia pestis Siphonaptera Plague

Spirochete

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)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

Nematode

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

Section 1

Culicidae / mosquito

Insecta

Diptera

Culicidae

Anopheles Culex Aedes

I Classification and morphology

1 Classification

Anopheles sinensis

Culex pipiens pallens

Aedes albopictus

piercing-sucking mouthpart

antennapalp

compound eye

Femur

Tibia

Tarsus

2 Morphological features

体分头胸腹，窄长翅一对

三对细长足，一根尖细喙

翅脉和翅缘，都有鳞片被

Piercing- sucking mouthparts

require water for development

females feed on blood30-300 eggs ovipositedadults

live 1-3 weeks

II Life cycle

wiggler

Anopheles Culex Aedes

a) paddy-field type :

b) slow stream type :

c) jungle type :

d) sullage type :

e) container type :

III Ecological behaviors 1 Breeding places depend upon egg-laying behaviors

a) domestic roosting mosquitoes

b) semi-domestic roosting mosquitoes

c) wild roosting mosquitoes

humid and dark areas

III Ecological behaviors

2 Habitat

human blood

domestic animal blood

female mosquitoes: blood meal male mosquitoes : feed on the nectar of flowers or other suitable sugar source

III Ecological behaviors

3 Host preference

direct harm: disturbance, succking blood

indirect harm ( biological transmission) mosquito-borne disease malaria Anopheles

filariasis Anopheles, Culex and Aedes

epidemic encephalitis B Cx.tritaeniorhynchus

Dengue fever Aedes aegypti/ albopictus

Yellow fever 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

IV Medical significance

Environment management

Physical control

Chemical control

Biological control

Genetic control

V Prevention and control

Fly

Insecta

Diptera

Cyclorrhapha

Muscidae Calliphoridae Sarcophagidae Oestridae

I Classification and morphology

1 Classification

Chrysomyia megacephala Lucilia sericata

Boettcherisca peregrina Musca domestica vicina

2 morphological feature

I Classification and morphology

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)

adult

eggpupa

Larva (maggot)

II Life cycle

pupaegg

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.

a) unable to feed themselves: Oestridae

b) sucking blood: Stomoxys

calcitrans ， 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

III Ecological behaviors 2 Feeding habit

mechanical transmission:

biological transmission:

tissue invasion and parasitism:

Myiasis

IV Medical significance

dermamyiasis