Spm entomology spotters (insects of public health importance)

Entomology
• study of insects of medical importance
TONY SCARIA 2010 KMC

• Vector :- is an arthtropod or any living carrier
that transport an infectious agent to
susceptible host
• Extrensic incubation period :10-14 days
malaria /filaria
• Definitive / intermediate host

MODE OF TRANSMISSION OF
DISEASES BY ARTHROPODS
• CONTACT TRANSMISSION
• MECHANICAL OR DIRECT TRANSMISSION
• BIOLOGICAL TRANSMISSION
Propagative
Cyclopropagative
Cyclodevelopmental

Biological transmission
• TRANSOVARIAN TRASMISSION:
• TRANSSTADIAL TRANSMISSION

PHYLUM ARTHROPODA
• CLASS INSECTA :
• CLASS ARACHINIDA
• CLASS CRUSTACEA -CYCLOPS

INSECT ORDERS OF MEDICAL
IMPORTANCE
• PHYLUM ARTHROPODA
• CLASS INSECTA
• ORDER DIPTERA- Includes MOSQUITOES, HOUSE
FLY,SAND FLY etc
• ORDER SIPHONAPTERA-FLEAS
• ORDER PHTHIRAPTERA-LICE

MOSQUITOES
• Tribe ANOPHILINI : Anopheles mosquitoes
• Tribe CULICINI : Culex, Aedes and Mansonia

BIONOMICS
• Study of habit and habitat of any organism
• Breeding habits, feeding habits, host preference,
resting habits, flight range if flying, longevity etc of
the vector
• If we want to control a VBD we have to know the
bionomics of the vector

BIONOMICS OF MOSQUITOES
BREEDING HABITS
• Breeding place is water
• The water may be stagnant pollutted, clear, artificial,
natural, moving, with some weeds or with shade
• In one ml of water or even in moist breeding places
the mosquitoes can breed

FEEDING HABITS
• Only FEMALE mosquitoes take blood meal
• Female mosquito needs a blood meal in every
48-72 hours for the maturation of the eggs
• Anopheles, Culex & Mansonia :nocturnal
feeders
• Aedes mosquitoes: Diurnal feeders

RESTING HABITS
• ENDOPHILISM : After a full blood meal
mosquitoes prefer to rest inside
• EXOPHILISM: After a full blood meal
mosquitoes prefer to rest outside
• Important in the disease control aspect

BIONOMICS
• According to the host preference they are
divided into
– Anthrophilic – taking blood from humans
– Zoophilic- taking blood from animals
– Ornithophilic- taking blood from birds
• This habits are important in the disease
transmission aspect

BIONOMICS
Flight RANGE
• This is the minimum distance they can fly from
the breeding places in search of food
• A female mosquito is able to fly a distance of
0.5 to 2Km
• Important in disease transmission

LIFE CYCLE OF MOSQUITOES
• Four stages: EGG, LARVA, PUPA & ADULT
• Complete metamorphosis or holometablous
• Life cycle :completed within 6 to 8 days
• The egg, larva and pupa are in water &adult is
terrestrial

LIFE CYCLE
• EGGS : Are laid in water.
• 48 to 72 hours after a full blood meal a female
mosquito will lay 100 to 150 eggs at a sitting.
• Eggs may be laid singly or in groups.
• The period between blood meal to time of egg
laying : Gonotrophic cycle.

LIFE CYCLE
LARVA
• Egg to first instar larva: 1 to 2 days
• Head, thorax and abdomen
• Thorax unsegmeted. Abdomen 10 segmented.
• Siphon tube: 8th segment (except anopheles)

LIFE CYCLE-LARVA

LIFE CYCLE -LARVA
• Four instar stages in the larval stage
• Larva undergoes 3 moultings
• Feeds on micro organisms.
• Larval stage lasts for 4 to 6 days
• 4th instar develop into pupa

LIFE CYCLE-PUPA
• Non feeding stage/resting stage
• Comma shaped
• Cephalothorax and segmented abdomen
• Two small respiratory tubes or trumpets :upper
surface of the thorax.
• Stay quiet at water surface

LIFE CYCLE - PUPA

LIFE CYCLE -PUPA
• Pupal stage :1-2 days
• From the pupa emerges out the adult
• Egg to adult : 6 to 8 days

LIFE CYCLE –EMERGENCE OF THE
ADULT

ADULT MOSQUITO
• Body : head, thorax & Abdomen
• Head : A pair of large compound eyes
(semiglobular) A probocis
A pair of palpi (4 segmented)
A pair of antennae
• Thorax : 1 pair of wings & 3 pairs of legs
• Abdomen : 10 segments
Last 2 modified to Ext. genitalia

ADULT MOSQUITO
ANTENNA
Male - bushy or Plumose
Female - scanty hairs or Pilose.

LIFE CYCLE -ADULT

ADULT MOSQUITO

ADULT MOSQUITO
• THORAX-Pronotum, Mesonotum and Metanotum
• Mesontum having a pair of wings
• Wings having 6 veins with hairs
• A pair of rudimentary wings : Halteres
• Thorax :3 pairs of legs

ADULT MOSQUITO
ABDOMEN
• Ten segmented
• Only 8 are visible
• Last 2 are modified as external genital organs.

SPECIES IDENTIFICATION

ANOPHELES EGG
• Breeding :clear water
• Eggs: laid singly
• Boat shaped with lateral floats or air sacs
• Air sacs prevent submerging/floating

ANPOHELES EGG

EGG OF ANOPHELES

ANOPHELES MOSQUITO LARVA
• Rest Parallel to the water surface
• Palmate hairs: both sides of all abdominal segments
• A pair spiracles: 8th abdominal segment for breathing
• No siphon tube

ANOPHELES MOSQUITO LARVA

ANOPHELES LARVA

ANOPHELES MOSQUITO PUPA
• Cephalothorax :short &broad respiratory
trumpet ( siphon tube)
• Abdomen :palmate hairs

ANOPHELES PUPA

ANPOPHELES ADULT
PROBOCIS

ANOPHELES ADULT
• Head:compound eyes,proboscis ,maxillary palpi and
antennae.
• Rests at an angle to the surface
• Proboscis &maxillary palpi have equal length
• Wings spotted
• The hairs on the wing veins are arranged in a spotted
manner

ANOPHELES ADULT
• Antennae : Bushy – male
Less hairy - female
• Tip of palpi: Club shaped- male
Straight - female

ANOPHELES ADULT

ANOPHELES FEMALE HEAD

ANOPHELES ADULT
MALE

Anopheles adult male brushy palpae

Anopheles female

ANOPHELES AS VECTORS OF MALARIA
• India :70 species (10 -15 species : vectors)
• An.stephensi :Urban vector
overhead tanks
• An. Culicifacies :Rural vector
in and around paddy fields

VECTOR BIONOMICS
• Breeding habit: clean water
– Slow moving stream of water,puddles of rain water
• Biting time : early part of night
• Resting habit: mainly endophilic
• Feeding habit: females blood meal every 2-3 days
: Males never bite
• Both anthropophilc & zoophilic

ANOPHELES AS VECTORS OF MALARIA
• An. Fluviatilis & minimus: in foot-hill regions
• An.sundaicus& stephansi : coastal areas
• An.philipenensis& culicifavies: plain areas
• An.balabacensis in forest areas

CULEX MOSQUITOES
• “Nuisance mosquitoes”
• Breeding places : stagnant polluted water
• Eggs : Raft like clusters (100-250 egg)
• Egg :cigar shaped with one end pointed

CULEX EGG RAFT

Culex egg raft

CULEX LARVA
• Culex larva : hangs downwards from the water
surface
• Siphon tube : long & tubular
8th abdominal segment
• No palmate hair or spiracle

CULEX LARVA

Culex larvae

CULEX PUPA
• A large cephalothorax & narrow segmented
abdomen with a pair of paddles.
• Cephalothorax : a pair of respiratoty trumpet
long and tubular

CULEX PUPA

CULEX ADULT MOSQUITO
• Palpi & probocis : Dfferent length
• Wings uniform

HOUSEFLY WING

• Male culicine mosquitoes: maxillary palp are
longer than proboscis and some what diverted
• Female culicine:length of palpi is one third of
proboscis
• Antenna plumose in male and pilose in female

CULEX MALE HEAD

CULEX FEMALE HEAD

CULEX ADULT MALE

CULEX ADULT FEMALE

VECTOR BIONOMICS
• Breeding habit : polluted & dirty water (cess
pools ,drainage, stagnant water collections, septic
tank, burrow pits , sewage)
• Feeding : mainly antropophilic
• Biting time : midnight
• Resting habit: Endophilic

CULEX MOSQUITO AS VECTORS
• 2500 species
• Lymphatic filariasis & JE
• Culex quiquefasciatus formerly known as
C.fatigans : bancroftian Filarisis.

CULEX MOSQUITO AS VECTORS
• JE: C. tritaenorhynchus, C. vishnui and
C. pseudovishnui (vishnui complex)
• Breeding places : in and around paddy fields.

Culex female

Culex female head

Culex male

Culex male head

Wing of culex

AEDES MOSQUITO (STEGOMYIA)
• Eggs : laid singly
• Egg :torpedo shaped
• Withstand drying upto one year.
• In 1 ml of water or even in moist places it can
lay eggs.

AEDES MOQUITO EGG

AEDES MOSQUITO LARVA
• larva :worm like with head, thorax and
abdomen.
• Suspended in water at an angle to water surface
• Siphon tube : broad & short
- 8th abdominal segment
- barrel shaped and brown in colour with a hair tuft
on it

AEDES MOSQUITO LARVA

Aedes larvae

AEDES MOSQUITO PUPA
• Comma shaped with cephalothorax and
segmented abdomen.
• The breathing trumpets are short and stumpy

AEDES MOSQUITO PUPA

AEDES ADULT
• White stripes on black body
• Legs also have banded apperance ( tiger)
• Wings uniform

AEDES ADULT
• Antennae : Bushy – male
Less hairy – female
• Smaller than other mosquito species
• Rest of features (palpi & probocis) similar to
culex

AEDES ADULT MOSQUITO

Aedes adult male

Aedes adult female

AEDES MOSQUITO AS VECTORS
• Aedes aegypti and Aedes albopictus
• Dengue fever, Chikungunya, Yellow fever
• A.aegypti - clear water & Ae.albopictus - tree holes.

VECTOR BIONOMICS
• Breeding : container breeders
• Feeding habit: mainly anthropophilic
• Biting time : “fearless day biters”
• Flight range : less than 100m

AEDES MOSQUITO INDICES
1. Aedes aegypti index or house index.
Ratio expressed as percentage
Number of houses showing actual breeding
sites of A. Aegypti to the total number of
houses examined in a limited well defined
area multiplied by 100.

AEDES MOSQUITO INDICES
2 BRETEAU INDEX : This is total number of positive
containers for Aedes breeding divided by total
number of houses examined multiplied by 100
3 CONTAINER INDEX: This is the total number of
positive containers divided by total number of
containers examined multiplied by 100.
4 PUPAL INDEX: Number of containers having
pupa divided by total containers examined
multiplied by 100

MANSONIA MOSQUITOES
• Eggs : groups & the under surface of the
leaves of these water plants
• Egg : spindle shaped
• Each egg group : flower like or star shaped
cluster

MANSONIA MOSQUIT EGG

Mansonia egg

MANSONIA MOSQUITO LARVA
• Suspended at an angle to water surface
• Siphon tube : triangular with chitinous tip
• If detached from water plants it die due to
suffocation.

MANSONIA MOSQUITO LARVA

Mansonia larvae

MANSONIA PUPA
• Large cephalothorax & segmented abdomen
• Cephalothorax: siphon tube
long & narrow with chitinous tip
• Like larva it also attaches to the water plants
and get oxygen.

MANSONIA PUPA

MANSONIA ADULT MOSQUITO
• Speckled wings and legs
• Antennae : bushy – male
Less hairy – female
• Head :same as that of culex mosquito.

VECTOR BIONOMICS
• Biting time: night
• Feeding habit : both antropophilic & zoophilic
• Resting habits : outdoors

MANSONIA ADULT MOSQUITO

MANSONIA AS VECTORS OF DISEASE
• Brugia malayi type of filariasis: M.Annulifera,
M.Uniformis, M.Indiana and M. Longipalpis
• Breeding :water with aquatic vegetations such
as pistia, salvinia and eichornia.
• Above species are seen in the coastal areas of
kollam, alappuzha, ernakulam etc.

AEDES EGG

AEDES MOSQUITO

AEDES LARVA

CULEX ADULT
FEMALE

CULEX MALE
HEAD

ANOPHELES FEMALE
HEAD

ANOPHELES ADULT FEMALE

House fly
Important species are
• Musca domestica
• Musca vicinia
• Musca nebulo
• Musca sorbens

House fly
• Mouse grey in colour
• 6-7 mm long, hairy
• Three body segments
• Head, thorax and abdomen
• Six legs
• A pair of wings
• Wings-transparent

House fly - Head
• A pair of compound eyes
• Eyes are closer in males and
far apart in females
• A pair of antenna - small
• Retractile proboscis

• Thorax- 2-4 dark longitudinal stripes
• A pair of wings, 3 pairs of legs
• Legs- pads : help the fly to walk on polished surface
• Tenent hairs - Short & stiff hairs are present in the
body and legs - secrete a sticky substance

House fly- life cycle
• Egg- 120-150 eggs/sitting, 1mmlong, pearly white and
they hatch out in 8-24 hours
• Larva (maggots) – 1-2 mm length, segmented, worm
like, no eyes / appendages, a narrow anterior and
broader posterior end, (2-7 days)
• Pupa- white in early stages, later it becomes dark,
barrel shaped, 3-6 days

8-24h
•2-7 d
•2-6 d
Adult - 8-20/ 5-6 days
•Lives- 15 / 25days

Egg of housefly

Pupae of house fly

Larvae of house fly

Housefly mouth parts

Wing of housefly

Habits
• Breeding Animal and human excreta, garbage,
decaying fruits and vegetables
• Feeding Does not bite, Can not eat solid food.
• Resting Rest on vertical surfaces and hanging
objects
• Dispersal 4 miles
• Vomit drop & defecation

Transmission
• Mechanical :Ova & cyst etc mechanically and called
porters of infection.
• Vomit drop It is a rich bacterial culture
• Defecation

Mechanical transmission of diseases
• Viruses : Hepatitis, poliomyelitis.
• Bacterial : Enteric fever, bacillary dysentery, cholera, wound
infection & trachoma.
• Parasitic : Mechanical transmission of
Eggs: Ascaris, Trichuris, Hymenolpis nana
Cysts: Entameba histolytica, Giardia

Fly control
1. Environmental control
clean house with clean surroundings
2. Insecticidal control
DDT (5%), lindane(0.5%), fenthion (2.5%), malathion(5%), diazinon
(1-2%), dimethoate etc as residual sprays/ space spray/ Baits/
cords & ribbons, larvicides
3. Fly papers –resin 2lbs & castor oil 1 pint
4. Protection against flies-screening (14mesh/inch)
5. Health education

Phlebotominae
• Like a mosquito, lb- db colour
• Tiny insects (1-3 mm)
• Smaller than mosquitoes
• Hairs on body and wings
• Wings rest over body like
“angel’s” wings
• Only females suck blood

• Phlebotomus argentipes
• P. papatassi
• P. serpenti
• Sergentomyia punjabensis

Sand flies Phlebotomus spp
• Wing kept erect while resting.
• Breed in crack of soil and wall, rubbish heaps
• Move in hops rather than fly (50 yards)
• Nocturnal, during day time rest in cool damp places

Sand fly
• A pair of long, slender hairy antenna, palpi & proboscis
• 1 pair of wings & 3 pairs of legs
• Whole body is covered with hairs
• Abdomen – 10 segments

Sandfly
• In males 2 claspers are seen in
the 10th abdominal segment
• In females ,10th abdominal
segment has 2 small cerci
• Eggs – damp dark places

Male sand fly

Female sandfly

Sand fly
Leishmaniasis
– Visceral leishmaniasis (Kala azar) – P argentipes
– Cutaneous leishmaniasis (oriental sore) P papatasii, sergenti
– Mucocutenous.leishmaniasis
Transmission cyclopropagative
– Sand fly fever viral disease P papatassi, Sergentomyia
punjabensis
Mild fever like influenza propagative

Control measures
• Insecticides DDT 1-2g/m² or Lindane 0.25g/m²
DDT The residual effect is up to 1-2 years
Lindane for 3 months
• Sanitation Removal of shrubs and vegetations, Filling
up of cracks and crevices in the wall and floors,
location of cattle sheds & poultry houses

Others
• Tsetse fly/ Glossinae - Blood sucking fly, only found in Africa,
(fly belt) - Trypanosomiasis
• Black fly/ Simulum- Blood sucking fly
Vectors of Onchocerciasis
The larvae are aquatic
Control is by adding abate to river water.

Human lice

Lice
• Small wingless insects, ectoparasites
• Three species that solely live on humans
– Pediculus humanus occurs in two subspecies
• the head louse (P. h. capitis) and
• the body louse (P. h. corporis)
• The body louse lives mostly in the clothing and
attaches its eggs to its fibers
• The third species of human lice is Phthirus pubis/
crab or pubic louse.

Head louse- Pediculus humanus capitis
• The head louse lives in the hair and attaches eggs (nits) to
the hair
• Body - dorso-ventrally flattened, has head, thorax &
abdomen
• Head-pointed, bears a pair of 5 segmented antennae,
Simple eyes
• Sucking & piercing type
• Thorax has 3 pairs of appendages
• Last segment of appendages ends with claws

Head louse
• In females last abdominal
segment is bifid
• In males last abdominal
segment is pointed not bifid.
• Males posses a U shaped organ
called aedeagus
• Aedeagus is species specific
and region specific

Pthirus pubis - Pubic
Louse
• Resembles a crab, about 2mm
• Attached to pubic hair & eye lashes
• Head, thorax, abdomen
• Thorax has 3 pairs of legs & first pair
is slender
• Last segment of appendages ends
with claws
• Abdomen has lateral projections
called lateral papillae
• Females last abd.segment is bifid
• In males last segment is not bifid.

Lice -PH importance
Disease transmission:
• Lice act as a vector for
Epidemic typhus – R prowazeki
Relapsing fever – B recurrentis
Trench fever – R quintana
• Pediculosis, dermatitis, irritation and pruritus.

Control of lice
Insecticides
• Lotion with 0.5% malathion, applied and kept on for 12-24
hrs.
• Dust - carbaryl
• DDT, HCH & malathion
• Mass delousing – 50g/ person
Personal hygiene

Fleas of medical importance
• Small, bilaterally compressed, wingless insects and
got a exoskeleton and backwardly directed bristles
• Fleas found on one particular kind of animal host
will not usually seek the blood of another species

Types of fleas
• Rat flea— Xenopsylla cheopis
Xenopsylla astia
Xenopsylla braziliensis
• Human fleas- Pulex irritans
• Dog and cat - Ctenocephalus canis
Ctenocephalus felis
• Sand flea – Tunga penetrans

Morphology
• Body is bilaterally compressed with head, thorax and
abdomen
• No definite demarcation
• Head
- Conical, attached to thorax without a neck
- Bears piercing and sucking mouth parts which project
downwards

• Thorax
3 segments & 3 pairs of legs
• Abdomen
- consists of 10 segments
- In males , the 7th abdominal segment dorsally has a sensory
organ - pygedium
- Anterior to this anti pygedial bristles arise directly from the
body
- Females have dark curved structure in the posterior part,
spermatheca which is used for storing sperms

Life cycle
• Metamorphosis is complete
• Eggs-larva-pupa-adult
• Adult flea seen on body of the host
• Immature stages seen on premises of host
• Takes 3 weeks to complete life cycle

x.braziliensis

X.Braziliens male BRUSH LIKE
projections

X.Cheopsis female
Cshaped

Ctenocephalides
• Ecto- parasites of dog and cat
• Characterized by black teeth like structure on head
known genal comb and another set on first thoracic
segment-pronotal comb
• If an infected flea is swallowed by man, he gets
infected

Dog flea, cat flea
Trop. rat flea
dog flea cat flea

Ctenocephalides canis

Ctenocephalides male

X. cheopes • Main vector for plague
• Females have “C”shaped
spermatheca with uniform thickness
which is used for storing sperms
• In males spermatheca is absent, the
7th abdominal segment dorsally has a
sensory organ-pygedium
• Anterior to this is anti pygedial
bristles arise directly from the body
• 9th sternite is club shaped

X. astia
• In female-spermatheca is bulbus at the middle –a shaped
• In male- anti pygedial bristles arise directly from the
body
• 9th sternite is ribbon shaped

X. brazeliensis
• In female-spermatheca is bulbus at one end –b shaped
• In male- anti pygedial bristles arise from a conical
base
• 9th sternite is absent

Diseases transmitted
• Plague (bubonic)
• Endemic or murine typhus
• Chiggerosis
• Hymenolepis diminuta
• Modeof transmission
– Biting-blocked flea
– Mechanical transmission
– Faeces

Flea Indices
• General flea index
It is the average number of fleas of all species per rodent
• Specific flea index
It is the average number of fleas of each species found per
rodent
If one or more than one ,chance of plague outbreak
• Rodent infestation rate
Percentage of rodents infested with fleas

Control of fleas
• Insecticides
– DDT(5-10%),γHCH, dieldrin, diazinon(2%)
– Applied in floors & walls up to 1ft
– Applied in rat burrows
• Repellents
– Diethyl toluamide
• Rodent control

Rodent control
• Environmental sanitation
• Rodenticides
(1)Single dose - Ba carbonate and Zn phosphide
Rat killed in 8-24 hrs
(2) Multiple dose – Anticoagulants(warfarin, coumafuryl)
Rat killed in 4-10 days

• Fumigation of rat burrows using Ca cyanide, methyl bromide
etc.
30 gm of powder sprayed inside rat burrow after closing all
openings
Final opening sealed with wet mud
When powder form comes in contact with moisture it emits
cyanide gas and kills rats and fleas

Ticks
• Wingless insects
• Ectoparasites of vertebrate animals
• They all suck blood
• Body is oval in shape ,and has two parts- head or
Capitulum & Abdomen
• Head is at anterior end
• Has 4 pairs of appendages, no antennae
• Hard ticks are covered on their dorsal surface by
a chitinous shield called scutum

Hard ticks • Males are smaller than
females
• In males body is
completely covered by
scutum
• In females anterior 1/3rd is
covered by scutum
• Vertical transmission from
mother to egg

Hard tick
Male
Female

Hard tick
FemaleMale

Hard tick male

Hard tick female

Female hard

Soft tick
• Abdominal wall is smooth
• Dorsal surface has small
dot like mamillary
tubrercles
•Small, soft and leathery cuticula,
•Mouthparts invisible from dorsal aspect
•The scutum/dorsal shield is `absent

Soft tick

Soft and hard ticks
(Agasidae/Ixodidae)

• Hard tickhard cuticle
- Babesiosis, Tularaemia
- Colorado tick fever,
- Rocky mountain spotted fever,
- Tick paralysis ,KFD
• Soft ticksoft cuticle
- Relapsing fever Borrelia duttoni
- Q fever
- KFD

Mites –sarcoptes scabei
• Tiny (0.1-0.3 mm) endo-parasitic mite
• Lives in epidermal layer of skin
• Body - Capitulum & Abdomen
• Eyes antennae & wings are absent
• 2 pairs of legs in front 2 pairs behind.
• Front legs end in long tubular process-
suckers
• Hind legs end in long filamentous bristles

sarcoptes scabei
FemaleMale

Sarcoptes scabiei- Public health importance
• Causes human scabies
• Scabies is characterized by an intensely
pruritic, erythematous, papular eruption
caused by burrowing of adult female mites in
upper layers of the epidermis, creating
serpiginous burrows. Itching is most intense at
night
• Sites of lesion – hands & wrist (63%),extensor
aspect of wrist (11%),

Preferred sites interdigital, popliteal fold and groin

Cyclops • Class-crustacea
• Pear shaped semi transparent
body, forked tail, 2pairs of
antennae
• Large cephalothorax &
slender segmented abdomen
• Single small pigmented eye
• In females 1st abd. segment
has apair of ovisac

Cyclops
Female
Male

Cyclops (water flea)
• Vector for:
Dracunculus medinensis

Cyclops male

Helminthic egg

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