Introduction to Medical Entomology กีฏวิทยาทางการแพทย ์
รศ.ดร.ปรัชญา สมบูรณ์
Objectives
To provide basic knowledge, including prevention and control, of insects and arthropods which are medically important
Insects
Arthropods สัตว์ขาข้อ
Characteristics of Arthropods (Phylum Arthropoda)
- Segmented body and appendage - Exoskeleton (cuticle) - Haemocoel
Medically important arthropods
1. Vector of diseases - biological vector
• propagative transmission (viruses, rickettsiae, bacteria)
• cyclopropagative transmission (malaria, leishmania, trypanosomes)
• cyclodevelopment transmission (filarial worm) - mechanical vector • House fly, cockroaches carrying pathogens/parasites
• Proboscis of Aedes mosquitoes transmitting dengue virus
2. Causes of diseases or nuisance
2.1 Entomophobia
2.2 Injury of sense organs (eg. eyes, ears, noses)
2.3 Venom, toxin and allergy (eg. bees, ants,
house dust mites, mayfly, shrimps, crabs, horseshoe
crabs)
2.4 Nuisance and blood loss (eg. midges, flies)
2.5 Skin disease and dermatitis (eg. scabies, beetles)
2.6 Infestation of larvae, nymph (eg. myiasis,
pentastomiasis)
Classification of Phylum Arthropoda
1. Subphylum Trilobites
2. Subphylum Chelicerates
Class Arachnida (spiders, scorpions, ticks, mites)
Class Merostomata
Horseshoe crabs (แมงดาทะเล)
แมงดาจาน (หางเหลี่ยม) แมงดาถ้วย/เหรา (หางกลม) tetrodotoxin, saxitoxin
6 Subphyla
Arachnida
เห็บ (ticks) ตัวหิด (Scabies mite) Scrub typhus mite (chigger)
แมงมุม (spider) แมงป่อง (scorpion)
Vector of Rickettsial diseases
Tick paralysis
โรคหิด (Scabies) (Sarcoptes scabiei)
larva
eggs
3. Subphylum Myriapods Class Chilopoda (centipeds ตะขาบ) Class Diplopoda (millipeds กิ้งกือ)
Copepods (กุ้งไร) I-H of Gnathostoma spp. etc.
Crab I-H of Paragonimus spp. Poisonous/allergies
4. Subphylum Crustaceans
Shrimps/prawns Shellfish allergies
Subclass Pentastomida
Tongue worm
Visceral pentastomiasis
5. Subphylum Hexapoda Class Insecta
Order Diptera
ยุง (mosquito) แมลงวัน (flies)
เหลือบ (horse flies)
ริ้น (Biting midges)
ริ้นด า (คุ่น) (Black flies)
ริ้นฝอยทราย (Sand flies)
A victim two days after being bitten by midges (Okinawa 1999)
Myiasis
Order Siphonaptera
I-H of D. caninum Vector of Plague
Pediculosis
Pediculus humanus Phthirus pubis (โลน) Head louse, body louse
(เหา)
หมัด
Order Anoplura
Order Hemiptera
มวน
Vector of Trypanosoma cruzi
เรือด (bed bugs) Assassin bugs มวนเพชฌฆาต
Order Dictyoptera แมลงสาบ (cockroaches)
Order Coleoptera ด้วง (beetles) I-H of Acanthocephala Dermatitis
Order Lepidoptera ผีเสื้อ (butterflies, moths) caterpillar
Rove beetles
Paederus spp.
pederin
ด้วงก้นกระดก
พิษแมลงตด Blister beetle
Order Hymenoptera มด(ants), ผึ้ง (bees) ต่อ/แตน (wasps) bites stings
Order Odonata แมลงปอ (dragonflies, damselfies)
Naiad (nymph)
I-H of small intestinal flukes
Order Ephemeroptera ชีปะขาว (Mayfly)
Allergy due to molting skin
Life Cycle and Metamorphosis of Arthropods
1. Ametabolous Development e.g. silverfish Egg Adult 2. Hemimetabolous Development e.g. lice, bugs, dragonfly
cockroaches
Egg Nymphs Adult 3. Holometabolous Development e.g. mosquitoes, fleas
bees, ants, house flies
Egg Larva Pupa Adult
Egg Larva Nymph Adult
Ticks and Mites
(6 legs)
AMETABOLOUS HEMIMETABOLOUS HOLOMETABOLOUS
Important vector-borne diseases in Thailand
1. Malaria 2. Dengue Haemorrhagic fever/Chikungunya 3. Japanese Encephalitis 4. Filariasis 5. Scrub typhus 6. Leishmaniasis
Mosquitoes
Classification
Class Insecta; Order Diptera; Family Culicidae (+3,523 spp.)
2 Subfamilies
Anophelinae Culicinae (3 genera) (108 genera)
Anopheles ยุงก้นปล่อง Aedes* ยุงลาย
Culex ยุงร าคาญ Mansonia ยุงเสือ Toxorhynchites ยุงยักษ์, ยุงช้าง
*http://mosquito-taxonomic-inventory.info/
Important mosquito vectors in Thailand
Malaria - Anopheles minimus, An. dirus
Dengue
Chikungunya
Bancroftian filariasis - Aedes niveus subgroup (rural) - Culex quinquefasciatus (urban)
Brugian filariasis - Mansonia spp.
Japanese encephalitis - Culex tritaeniorhynchus
- Cx. vishnui
Aedes aegypti, Ae. albopictus
Life cycle of mosquitoes
ADULTS
Culicine Anopheline
EGGs
Aedes
Culex Anopheles Mansonia
LARVAE
PUPAE
Aedes
Culex
Anopheles
Mansonia
Mansonia
others
Antennae and palpi
Female Male
Culicine
Anopheline
palpi
palpi
antenna palpi
palpi palpi
proboscis
Pilose type Plumose type antenna
Anopheles female
scutellum round
Long palpi
spotted or dark wing
Aedes aegypti ยุงลายบ้าน Aedes albopictus ยุงลายสวน
(Stegomyia aegypti) (Stegomyia albopicta)
ยุงลาย Armigeres sp.
Culex quinquefasciatus
Mansonia females
Toxorhynchites sp.
female male
Anopheles larva
Palmate hair
Culex larva
siphon
Aedes larva
Mansonia larva
Mansonia larvae
pupa
Toxorhynchites larvae
Mosquito eggs
Anopheles Aedes
Mansonia Culex
Anopheles stream, pool, pond, rice field etc. Aedes tree hole, bamboo stump, container, small pool etc. Culex drain, pool, pond, rice field etc. with high organic substances Mansonia swamp, pond with water plants Toxorhynchitis tree hole, bamboo stump, container
Breeding sites (places)
Breeding sites of Anopheles
Breeding sites of Aedes aegypti
Breeding sites of Ae. albopictus, Ae. niveus subgr.
Breeding sites of Culex quinquefasciatus
Breeding site of Mansonia spp.
Host seeking
Prevention and control of mosquito-borne diseases
1.Reduce morbidity (sickness)
2.Reduce mortality (death)
3.Prevent infection
4.Stop transmission
Objectives
Control Targets
Vectors Agents Humans Environment
- surveillance - control
- drug - vaccine
- education - behaviour - participation - law
- policy - planning
Integrated control strategies
Vector Control
Objectives: 1.reduce vector population 2. reduce man-vector contact
Adult stage Immature stages (Breeding sites)
- chemicals - traps - biting protection
- mechanical - chemical - bioagents
1. Personal protection - bednet (mosquito net) - screening house - repellent - clothing 2. Mosquito control
Reduce man-vector contact
Bednet
Repellents and
Vapourized insecticides
Mosquito control
- Environmental methods reduction of breeding sites, - Chemical methods residual spray thermal fogging ultra-low-volume aerosol spray impregnated bednet larvicide - Biological methods - Genetic control
Adulticide Applications
1. Residual spray
Long-lasting insecticide is sprayed and deposited on a surface.
2. Thermal fogging
Insecticide mixed with a carrier (e.g. diesel) and sprayed with a combustion engine to be fog.
ULV spray
ULV spraying fills a 20-foot column with an ultra low volume of active ingredient (droplet ~20 µ)
Impregnating bednets
Larvicide temephos sand granules (1%) (ทรายอะเบต)
Biological control methods
- Predators : mosquito fish, copepods,
Toxorhynchites
-Pathogens : Bacillus thuringiensis,
B. sphaericus
-Endoparasites : mermitid nematodes
-Ectoparasite : water mite
Gambusia holbrooki 2-2.5 cm
Guppy fish 3-7 cm
The mosquito fish
Bacillus thuringiensis israeliensis (Bti)
Romanomermis culicivorax infective juvenile
Mermitid nematode
Prevention and control of mosquito-borne diseases
Dengue Breeding site reduction Personal protection Fogging or ULV
Malaria Impregnated bednet Residual spray Personal protection Chemotherapy
JE Vaccine Zooprophylaxis Personal protection
Filariasis Breeding site reduction Personal protection Chemotherapy