Entomology 1

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Entomology Dr. Nitin Solanki Assistant Professor Gujarat Adani Institute Of Medical Science


2 Introduction: The study of diseases caused by arthropods Entomo (gr) = ‘segmented’ logy= ‘study’ Arthron = ‘jointed’ Poda = ‘foot’ Arthropods: largest phylum in the animal kingdom B/L symmetrical segmented body, supported by exoskeleton(chitin), do not have bones, but the hard outer covering supports the muscles. The appendages are jointed . The body is formed of a number of segments .

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Phylum Arthropoda Class Crustacea - lobsters, crabs, etc. Class Chelicerata - spiders, mites, ticks scorpions, etc. Class Diplopoda - millipedes Class Chilopoda - centipedes Class Insecta - beetles, flies, moths, etc. Phylum Arthropoda has 5 classes, out of which 3 are medically important.


4 Characters: Insecta Arachnida Crustacea Body division: Head Thorax & Abdomen Cephalo-thorax & Abdomen Cephalo-thorax & Abdomen Legs: 3 pairs 4 pairs 5 pairs Antennae: 1 pair - 2 pairs Wings: 1 pair or Wingless - - Habitat: Land Land Water

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Medical Entomology:

Medical Entomology Branch of preventive Medicine A study of the arthropods of Medical importance is known as Medical Entomology.

Why study of this is important?:

Why study of this is important ? 1 Mosquito Malaria, Filaria, JE, Dengue Fever, Chikungunya 2 Housefly Typhoid, Cholera, Diarrhea & Dysentery, Poliomyelitis, Gastroenteritis, Trachoma 3 Itch Mite Scabies 4 Cyclops Guinea worm disease 5 Sand fly Kala-azar 6 Tsetse fly Sleeping sickness 7 Louse Epidemic Typhus 8 Rat flea Bubonic Plague 9 Reduvig bug Chagas disease 10 Hard tick Tick typhus, Viral encephalitis 11 Soft Tick Q fever, Relapsing fever

Transmission of Arthropod borne diseases:

Transmission of Arthropod borne diseases Transmissions Direct Contact From man to man Scabies pediculosis Mechanical Diarrhea Dysentery Typhoid Trachoma Biological Propagative Only multiplication No developmental Plague bacilli in rat flea Cyclo propagative Multiplication developmental Malaria parasites in mosquito Cyclodevelopmental No multiplication developmental Filaria parasite In mosquito

Mosquitoes :

9 Mosquitoes

General Features of Mosquito:

General Features of Mosquito 10

General features:

General features Body consist of 3 parts: Head : Semi globular in outline, bears following structure. Pair of large compound eyes , Needle like structure called proboscis , with which it bites. Palpi situated on either side of proboscis. Pair of antennae or feelers. Antennae are bushy in male, not so in female. This is the distinguishing feature. 11

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12 Anopheles female Anopheles male Culex female Culex male

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Thorax : Large & rounded in appearance. Bears pair of wings dorsally which produces buzzing noise. Three pair of legs ventrally. Abdomen : Long & narrow, composed of 10 segment, last two segments are modified to form external genitalia. 13

Life history of mosquito:

Life history of mosquito Four stages of life history Egg Larva Pupa Adult 14


Eggs Eggs are laid on the surface of water,100 -250 at time. Anopheles lays her eggs singly , boat shaped and possess lateral floats 15

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2 Aedes Cigar shaped, Laid down singly, no lateral floats 16


Eggs………. 3. Culex small clusters 4. Mansonia lays her eggs in star shaped clusters , attached to the under surface of certain aquatic plants. 17 The period that elapses from the moment of blood meal until the eggs are laid is called “ gonotrophic cycle” about 48 hours. Egg stage of mosquito lasts for 1-2 days


18 Eggs: Anopheles Aedes Culex


Larva The larva is a free swimming creature with an elongated body divisible into head, thorax & abdomen. It feeds on algae, bacteria, and vegetable matters. Passes through 4 stages of growth called Instars with moulting between each stage. 19

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Anopheles larva : Exclusively surface feeder, Floats horizontally just below the surface of water, very active with swift movement No siphon tube, but breathing apparatus consist of parallel air tube at the tail end. Culicines Larva : suspended in water with head downwards, much slower with snake like movement Has long narrow siphon tube. 20

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Larva of Mansonia are attached to rootlet of aquatic plant by their siphon tube. Larval stage occupies 2 days in anopheles & 5-7 days in Culicines. 21


Pupa The pupa is comma shaped in appearance with large rounded cephalothorax and a narrow abdomen. Two small respiratory tubes or trumpets project from the upper surface of the thorax. It represents the resting phase in the life history of mosquito. Doesn’t feed & prefer to stay quite at water surface. The pupal stage lasts 1-2 days 22

Adult Mosquitoes:

Adult Mosquitoes When development is complete, pupal skin split along the back & adult mosquito emerges. It rests for a while on the pupal skin to allow its wings to expand & harden & then flies away. The life cycle from the egg to adult is complete within 7-10 days. Normally adult mosquito lives for about 2 weeks. Males are generally short lived. 23

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Anopheles Mosquito:

Anopheles Mosquito Identification features Spotted wings When at rest, inclined at an angle of 45* to the surface No buzzing sound 25 Anopheles

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Palpi long In both Anopheles male & female and short in Culicines female SPOTED WINGS 26 Anopheles 45* Antennae bushy

Palps are as long as the proboscis:

Palps are as long as the proboscis 27 Anopheles

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palps have white rings proboscis dark 28 Anopheles

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palmate hair on abdomen 29 Anopheles

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31 Siphon tube-broad & short

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Food Preference : it is both anthropophilic & zoophilic , a blood meal on the part of female Anophelines is essential for maturation of the ovum. Resting Habit : Endophilic , i.e. indoor resting habit for the purpose of digesting blood meal & for the development of the ovum. Flight: can cover long distance, about 0.75-1.5 km , it significant for practical control of mosquito vector. Life span: usually in India it lives for one month , hibernating mosquito lives longer about 6months 32 Anopheles

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Prefers clean water for breeding Breeds in Open overhead tanks, irrigation channel, river beds, Ponds, pools, lakes, spring, burrow pit, brackish water fruit & vegetable garden and even in wells. Time of biting : Evening or early part of night Feeding Habits : Only female bites, male never bites. 33 Anopheles


Culex Identification features When at rest, the body exhibits hunch back (i.e. the thorax makes an angle with the abdomen) Wings unspotted Buzzing noise produce by beating of wings, Culex. Fatigans – Vector of Bancroftian Filariasis 34 Culex

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proboscis and palps dark, palps short 36 Culex

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37 Culex

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Breeding places:

Breeding places It profusely breeds in dirty water collections contaminated with sewage. Stagnant drains Cesspools Septic tanks Burrow pits 39 Culex


40 Culex:

Time of biting:

Time of biting At night- enters the houses at dusk & reaches maximum density at midnight Peak time of biting is at midnight Site of biting – legs, below the knee 41 Culex

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Highly anthropophilic Dispersal is about 11 km , strong winged mosquito Average life span : 21 days The vector is mainly outdoo r resting and outdoor feeding. Diseases Bancroftian Filariasis ( Cu. Fatigans ) JE ( Cu. Vishnui ) West Nile fever Viral arthritis 42 Culex


Aedes Sits parallel to the surface White stripes on black body 43 Aedes

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44 Aedes

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45 Aedes

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46 Aedes

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47 Aedes

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48 Aedes

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50 Aedes Siphon tube-long & narrow


Aedes…. Because it bites vigorously and fearlessly to many persons, so it is also called as tiger mosquito Adult seek dark and quit places to rest in bedrooms, kitchen, on walls, furniture, hanging articles like clothing, ropes and closets Average survival for male is 20 days and for female 30 days. 51

Breeding places Aedes aegypti profusely breeds in Artificial accumulation of water :

Breeding places Aedes aegypti profusely breeds in Artificial accumulation of water Behind refrigetor & coolers, Storage tanks, Earthen pots and other receptacles with rain water, In flower vases, Tyres, Broken glasses, Plastic containers and tins which have been discarded. 52 Aedes


53 Aedes:

Time of biting:

Time of biting Day biters Do not fly more than 100 meter Mostly found in rainy water 54 Aedes

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Species A. aegypti and A. sentellaris : breeds in peri- domestic artificial collection of water. A. Albopictus : breeds in natural rather than artificial water collections. A. vittatus : seen outside India, not domestic mosquito. Diseases Dengue DHF Chikungunya fever Yellow fever 55 Aedes


Mansonia They breed on aquatic plants ( Pistia straitiotes ) for the supply of oxygen. Two species of the vector Mansoniodes uniformis and M. annulifera transmit Brugia malayi infection of Filariasis in India 56 mansonia


57 Mansonia:

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58 mansonia

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59 mansonia

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palps not more than 1/3 as long as proboscis, ‘club-like ’ 60 mansonia

Mosquito breeding places:

Mosquito breeding places anopheles 61

Mosquito breeding places:

Mosquito breeding places Mansonia 62

Mosquito breeding places:

Mosquito breeding places Mansonia 63

Mosquito breeding places.:

Mosquito breeding places. Aedes mosquito 64

Mosquito borne disease:

65 Mosquito borne disease Anopheles: Malaria Filaria Culex: Filaria JE West nile fever Viral arthrities Aedes: Yellow fever Dengue Chickungunya fever Rift vally fever filaria Mansonia: Filaria Chickungunya fever

Control measures::

66 Control measures: Antilarval measures: Environmental control: “source reduction” Chemical control: Mineral oils: MLO, fuel oil, kerosene. Peris green Synthetic pyrethroids: abate, malathion, fenthion, chlorpyrifos. Biolarvicide: Bacillus thuringiensis iserailensis (Bti)-Endotoxin Biological control: Larvivorous fish Gambusia affinis Lebister reticulatus

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67 Anti-adult measures: Residual spray: malathion, propoxur Space spray: pyrethrum, ULV spray of fenithrothion & malathion Genetic control

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68 Protection against mosquito-bite: Mosquito net: ITBN treated with Deltamethrin Screening: of windows, not >0.0475 inch in any diameter. Repellants : DEET, indalone , diethyl benzamide , dimethyl phathalate .

Insecticide Treated Bed Nets:

Insecticide Treated Bed Nets Specific Objectives Reduce human contact with the vector mosquitoes. Reduce morbidity due to malaria in the selected(vulnerable) population. Prevent deaths due to malaria. Promote concept of community participation in malaria control through NGOs, CBOs etc. Modalities through social marketing by public private partnership.

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Requirement State Programme officer- who make assessment by rapid surveys, size of nets & number of nets according to size Synthetic pyrethroids -(1) Deltamethrin (2.5%) at a dose of 25mg/ mt square (2) cyfluthrin (5%) at 50mg/ mt square Other may be used are pyrethrin 10%, Etofenprox 10% & alpha- cypermethrin

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The optimal effectiveness of insectides range 6-12 months, but 6 months is accepted for retreatment. This activity has been introduced by the government (NVBDCP 2007). Insecticide treatment procedure Step-1 –surface area of net determined by following formula surface area=2( a+b )+c, a=length*height, b=height*width, c=length*width

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Step-2 - The amount of formulation of insecticide for target dose of 25mg/ mt square of deltamethrin is calculated as: weight required(gm)=surface area in mt square* 0.025 Step-3- The volume of formulation required is determined by: volume required = weight(gm)*100 ml % formulation of insecticide

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For example to treat a mosquito net of 10 mt square using 2.5% formulation the volume of formulation required would be (10* 0.025)* 100 =10 ml 2.5 Step-4- Cold water must used always for this. The absorption capacity of net may be determine : It is done by immersing a net in a given quantity of water & allowing the net to absorb water. The left over water should be measured. This amount should be minus with the total amount will give the absorption capacity of water of the net.

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Step-5 – Use the tray for mixing the water & insecticide & wear the gloves for mixing & handling. Step-6 – Always dry the net in shades. Drying should never be done under the sun. Step-7 – Never throw the left over insecticide in any water body or drinking water source. It should be poured into a specially dug hole in dry ground where it would be absorbed quickly. It can be discharged into sewage drain or latrine. Synthetic nets are better than cotton as cost effective & effect of insecticide is last longer

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