MEDICAL
ARTHROPOD
INTRODUCTION
ARTHROPOD
Medical arthropod:
These arthropods related to human health.
Medical arthropodology:
A science that study the morphology, taxonomy,
life cycle, zoology, geographic distribution of
medical arthropoda, and the relationship of medical
arthropods with the transmission of the disease, as
well as the measures for medical arthropods control.
Features
1) Segmentation and Bilateral symmetry
2）Chitinous exoskeleton
3）Growth by molting
4）The body cavity is a hemocoele and
the circulatory system is open.
molting
Metamorphosis
Complete
metamorphosis(holom
etabola)
(including egg, larva,
pupa and adult)
Incomplete
metamorphosis(hemi
metabola)
( including egg,
larva/nymph, adult).
Classification
Insecta: mosquito, fly, sandfly, flea,
louse, cockroach, etc.
Arachnida: tick, mite, spider, etc.
Crustacea: crab, shrimp, etc.
Chilopoda: centipede.
Diplopoda: millipede.
Insecta
Arachnida
Crustacea
Diplopoda
Chilopoda
Harm for human health
Direct harms
1) Sucking blood and annoyance
(harassment )
2) Envenomization
Envenomization is the introduction of
a poison into the body of humans and
animals.
e.g. Biting from toxic spiders.
3)Allergic reaction
Child with
hypersensitivity to
mosquito bites.
Mosquito bites can
produce a severe
allergic reaction.
4)Invading tissue.
Demodex spp
Indirect harms: Disease transmission
Arbo-diseases is the disease transmitted by
arthropods
1)Mechanical transmission
Among those diseases that may be transmitted in
a mechanical manner
The bacterial enteritis. Enteric organisms may
be carried by flies that feed on fecal material to
foods destined for human consumption.
2)Biological transmission
Arthropod as a vector
Some infectious organisms require an
arthropod host for completion of their life
cycle. Most arthropod-borne diseases are
carried in this fashion
Arthropods and Arbo-diseases
Arthropod
Disease
Hard tick/Ixodidae
Forest encephalitis, Xingjing haemorrhagic fever,
Lyme disease, Q fever
Soft tick/Argasidae
Tick-borne recurrent fever, Q fever
Chigger/Trombiculid mites
Scrub typhus
Itch mite/Sarcoptidae mite
Scabies
Demodicidae mite
Folliculits etc
Dust mite/Pyroglyphidae
Asthma, Allergic rhinitis, Allergic dermatitis
Mosquito
Malaria, Filariasis, Japanese B encephalitis, Dengue
fever, Yellow fever
Fly/Musca
Dysentery, Typhoid fever, Cholera, Poliomyelitis,
Amebic dysentery, Myiasis
Sandfly
Kala-azar disease/visceral leishmaniasis
Flea
Plague, Murine typhus, Hymenolepiasis diminuta
Lice
Epidemic typhus, lice-borne relapsing fever
Determination of vector arthropods
Biological evidences
1)
It is closed relationship with human
2)
The arthropod is a common species
3)
The life span of the arthropod is long enough
Epidemiological evidences:
the seasonal fluctuation is consistent with the epidemic
trend of the suspected diseases
Laboratory evidences
Natural infection evidences
Control
Environmental management
Physical measures
Chemical measures
Biological measures
Genetic measures
Chemical measures
Insecticide:
1)
Organochlorine e.g., DDT
(dichlorodiphenyltrichlorethane)
2)
Organophosphates e.g.,
malathion, fenitrothion etc
3)
Carbamates e.g., malathion,
fenitrothion etc
4) Pyrethrum: ①allethrin( for
mosquito-repellent,incense), ②
permethrin,③deltamathrin
MOSQUITO
Morphology
Adults of mosquitoes are generally
1.6 to 12.6mm long, consists of
the head, thorax, and abdomen.
head
thorax
abdomen
Mouthparts
(proboscis)
palp
antennae
compound eyes
With mandibles
Without mandibles
The life cycle of mosquito
The complete life cycle contains eggs, larva,
pupa and adult. All mosquitoes require water
for the development of the larvae and pupae,
but the adults live in land.
Aedes
Culex
Anopheles
Some recognition features of
Anopheles, Culex and Aedes
egg
.
Anopheles
boat-shaped,
have a pair of
lateral floats,
laid single and
float on the
water surface.
Culex
cylindrical or
ovoid in shape
and no float.
They are laid
stuck together in
“egg’s rafts”
Aedes
olive-shaped, no
float. They are laid
single on humid soil
or the bottom of
water (cans,
contains)
Breathing pore
Float hair
The larave of
anopheles
Siphon tube for breathing
呼吸管毛
The larave of culex
Hair of breathing tube
The larvae of aedes
Recognition features in the adults of
Anopheles, Culex and Aedes
Features
Anopheles
Culex
Aedes
1.
color
Dark-gray
Brown
Black
2.
wings
With
white
black spots
Without white and black
spots
Without white and black
spots
3.
legs
With or without
white rings
Without white rings
With white rings
4.sitti
ng
posture
There is a angle
between the body
and the resting
surface
There
is
a
parallel
between the body and the
resting surface
There is a parallel
between the body and
the resting surface
and
Adults
Anopheles
Dark-gray
Culex
Brown
Aedes
Black
Wings
Anopheles
with white and black
spots
Culex and Aedes
without white and
black spots
“Hip”points to sky
Anopheline mosquito resting on a net. The resting
position of the adult Anopheles is typical in that the head,
thorax and abdomen are kept in almost a straight line. The
long axis of the body forms an angle of about 45。 to the
surface.
Culicine mosquito taking a blood meal. Unlike Anopheline,
these mosquitoes sit with a hunch. During the act of feeding
the labium curls backwards allowing the biting fascicle to
penetrate the tissues.
Ecology
1) Breeding habits
Breeding sites: the place where the females lay
eggs and breed larvae
There are five type of breeding sites
Paddy field type
Slowly flowing water type
Jungle type
Dirt water type
Container type
Paddy field type
of breeding- sites
includes rice fields, marsh and pond, in
which water is large, water clean and
still. The breeding sites is suitable for
Anopheles sinensis, anopheles
anthrophagus, and culex triaeniorhynchus
etc.
Slowly flowing water type
includes stream and irrigation raceway
with clean and slowly flow water, which
is the breeding site of Anopheles minimus
commonly.
Jungle
type
includes mountain
stream, stone cave and spring pond,
in which Anipheles dirus is found
usually.
Dirt water type
includes dirt water pit, sewer, fecal
pit, which are the breeding sites of
Culex
pipiens
quinquefasciatus.
pallens,
C.p.
Container type
includes water vats, jars, bamboo
container, tree-hole etc, which are
the breeding sites of Aedes
albopictus and A. aegypti.
2) The behaviors of sucking blood
3) Resting sites of the adults
4) Flying and activity
5) hibernation
In the winter, mosquitoes don’t suck blood and hide in
warn place such as inside of house; the ovary don’t
develop . The average month temperature is over
10℃, there is no hibernation for mosquitoes.
6) Seasonal fluctuation
The phenomenon that population density of the mosquito
varies with season is called seasonal fluctuation.
7) Longevity
In tropical areas, the adult mosquitoes may live on average
about two to 3 weeks; in temperature areas, the adult may
live on four to five weeks or longer; the males have a shorter
lifespan than the females.
Mosquito and diseases
1) Direct harm to humans
Biting by mosquitoes can cause
irritation, or allergic reaction
2) Transmission of diseases
Mosquito
Epidemic area
An.sinensis
Plain areas
An.anthropophagus
Mountain or hilly areas
in South China
An.minimus
Mountain or hilly areas
in South China
An.dirus
Jungle areas of Hainan island
2. Japanese B
encephalitis
Culex
tritaeniorhynchus
Paddy field
3.Filariasis
Culex pipiens
pallens C.p.
quinquefasciantus
As a vector of Filariasis
bancrofti in North areas of
Yangtse river
Anopheles sinensis
A. anthropophagus
As a vector of
Filariasis malayi
Aedes aegypti
A. albopicutus
Tropical areas
In China:Hainan, Guangdong
Arbo-diseases
1.malaria
4.Dengue fever
etc
Malaria
Control
1) Larva control
Chemical control, e.g., insecticide is placed in
the water; biological control, e.g., predators,
disease agents; source reduction or habitat
management.
2) Adult control
Insecticides (direct action and residual action);
Personal protection.