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.

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

Complete metamorphosis(holom etabola) (including egg, larva, pupa and adult) Incomplete metamorphosis(hemi metabola) ( 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 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 ArthropodDisease Hard tick/IxodidaeForest encephalitis, Xingjing haemorrhagic fever, Lyme disease, Q fever Soft tick/ArgasidaeTick-borne recurrent fever, Q fever Chigger/Trombiculid mitesScrub typhus Itch mite/Sarcoptidae miteScabies Demodicidae miteFolliculits etc Dust mite/PyroglyphidaeAsthma, Allergic rhinitis, Allergic dermatitis MosquitoMalaria, Filariasis, Japanese B encephalitis, Dengue fever, Yellow fever Fly/MuscaDysentery, Typhoid fever, Cholera, Poliomyelitis, Amebic dysentery, Myiasis SandflyKala-azar disease/visceral leishmaniasis FleaPlague, Murine typhus, Hymenolepiasis diminuta LiceEpidemic 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: ① allethrin( for mosquito-repellent,incense), ② permethrin, ③ deltamathrin 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 mandiblesWithout 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.

Some recognition features ofAnopheles, Culex and Aedes AnophelesCulexAedes

Anopheles egg CulexAedes 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 AnophelesCulexAedes 1. color Dark-grayBrownBlack 2. wings With white and black spots Without white and black spots 3. legs With or without white rings Without white ringsWith 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 Recognition features in the adults of Anopheles, Culex and Aedes

AnophelesCulex Aedes Adults Dark-gray Brown Black

Wings Anopheles with white and black spots Culex and Aedes without 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 MosquitoEpidemic area 1.malaria An.sinensisPlain areas An.anthropophagu s Mountain or hilly areas in South China An.minimusMountain 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 4.Dengue fever Aedes aegypti A. 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.