MEDICAL ARTHROPOD

INTRODUCTION

ARTHROPOD

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.

Medical arthropod: These arthropods related to human health.

Features1) Segmentation and Bilateral symmetry

2） Chitinous exoskeleton

3 ） Growth by molting4） The body cavity is a hemocoele and the circulatory system is open.

molting

Complete metamorphosis(holometabola) (including egg, larva, pupa and adult)

Incomplete metamorphosis(hemimetabola) ( including egg, larva/nymph, adult).

Metamorphosis

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

Chilopoda

Diplopoda

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.

Child with hypersensitivity to mosquito bites. Mosquito bites can produce a severe allergic reaction.

3)Allergic reaction

4)Invading tissue.

Demodex spp

Indirect harms: Disease transmission

Arbo-diseases is the disease transmitted by art

hropods

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

1)      It is closed relationship with human

2)      The arthropod is a common species

3)      The life span of the arthropod is long enough

Biological evidences

Determination of vector arthropods

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

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), ②permethrin,③deltamathrin

Chemical measures

MOSQUITO

Morphology

Adults of mosquitoes are generally 1.6 to 12.6mm long, consists of the head, thorax, and abdomen.

head

thorax

abdomen

antennae

compound eyes

palp

Mouthparts(proboscis)

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.

Som

e recognition

features of

An

opheles, C

ulex an

d Aedes

Anopheles Culex Aedes

Anopheles

egg

Culex Aedes boat-shaped, have a pair of lateral floats, laid single and float on the water surface.

.

cylindrical or ovoid in shape and no float. They are laid stuck together in “egg’s rafts”

.

olive-shaped, no float. They are laid single on humid soil or the bottom of water (cans, contains)

The larave of anopheles

Float hair

Breathing pore

The larave of culex

呼吸管毛

Siphon tube for breathing

Hair of breathing tube

The larvae of aedes

Features Anopheles Culex Aedes

1.color

Dark-gray Brown Black

2.wings

With white and 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.sitting 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

Recognition features in the adults of Anopheles, Culex and Aedes

Anopheles Culex Aedes

Adults

Dark-gray Brown Black

Wings

Anopheles with white and black spots

Culex and Aedeswithout white and black spots

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.

“Hip”points to sky

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

Slowly flowing water type

Jungle type

Dirt water type

Container type

Paddy field type

There are five type of breeding sites

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 pallens, C.p. quinquefasciatus.

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.

Mosquito and diseases

1) Direct harm to humans

Biting by mosquitoes can cause irritation, or allergic reaction

2) Transmission of diseases

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.

Arbo-diseases Mosquito Epidemic area

1.malaria

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.FilariasisCulex pipiens pallens C.p. quinquefasciantus

As a vector of Filariasis bancrofti in North areas of Yangtse river

Anopheles sinensisA. anthropophagus

As a vector of Filariasis malayi

4.Dengue fever

Aedes aegyptiA. albopicutus

Tropical areas In China:Hainan, Guangdong etc

Malaria

Control

1) Larva control

2) Adult control

Chemical control, e.g., insecticide is placed in the water; biological control, e.g., predators, disease agents; source reduction or habitat management.

Insecticides (direct action and residual action); Personal protection.