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.