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

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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

Water mites

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