vector bionomics community medicine powerpoint

MEDICAL - ENTOMOLOGY
A study of Arthropods of
medical importance

ARTHROPODS
1. Arthropods are the most numerous living things in
the environment of man. Some of them help in the
fertilization of flowers, but majority of them are
most dangerous enemies.
2. Some, which live close to man act as VECTORS or
carriers of disease.
3. The most important class of arthropoda is insecta.
4. Under this we will study about mosquito, flies, fleas.

VECTORS of Arthropod-Borne Diseases
1. Mosquito - Malaria, Filariasis, Japanese Encephalitis, Dengue, Viral
fever
2. Sand fly - Kala-Azar
3. House fly- Typhoid, Diarrhoea, Dysentery, Cholera, Poliomyelitis,
Conjuctivities, Amoebiosis, Gastroenteritis
4. Itch Mite - Scabies
5. Rat flea - Bubonic Plague
6. Ticks - Viral Encephalitis, Viral fever, Tick Typhus
7. Cyclops - Guinea-worm disease
8. Louse - Pediculosis

Transmission of Arthropod- Borne
Diseases
1. By Direct Contact : (Scabies & Pediculosis)
2. Mechanical Transmission: (Diarrhea, Dysentery,
Typhoid, Food-Poisoning by the House fly).
3. Biological Transmission: (Malaria by
Plasmodium, Filarial by Culex mosquito, Guineaworm
embryo in Cyclops).

.
By Direct contact:
Some arthropods spread disease by
direct contact.
For example, the Itch mite which
causes scabies is spread by direct
contact.

Mechanical transmission:
Some arthropods spread disease
mechanically by carrying the infection on
their bodies.
The common housefly is an outstanding
example; it spreads Diarrhoea and
Dysentery by mechanical transmission.

Biological transmission:
When the disease agent multiplies or undergoes
some developmental change in the insect host,
it is known as biological transmission.
The transmission of Malaria and Filaria by the
mosquito , and Plague by the rat flea are
examples of biological transmission.

ADULT ANOPHELES
• Main characteristic features:
• Sits at the angle of < 450
with the surface
• Spotted wings
• Long palpi equallant to proboscis in both the sexes
• Night biters (12 pm to 6 am), most active at dawn &
dusk
• Breeds in clean & slow moving water
• Flight range 3 to 12 kms.
• Female Anopheles spreads Malaria

ADULT AEDES
Main characteristic features :
• Spread Dengue & Chikunguniya, females are
highly anthropophilic
• Transluent, unspotted wings, bordered with
scales
• Dark black, Stripped body
• White rings on the legs
• Two yellow lines on the thorax
• Palpi shorter than proboscis in females
• Females bites both during the day & after dark
( mainly day biter )
• Breed in artificial collection of water
• Commonly called Tiger Mosquitoes

ADULT CULEX
Main characteristic features :
• Having unspotted wings & unstripped body
• Palpi shorter than proboscis in females &
longer than proboscis in males
• Preferably night biters (6pm to 12pm), most
active at dawn & dusk
• Bites on legs below the knees
• Breed in dirty or polluted water bodies
• Flight range up to 11 kms.
• Commonly called Nuisance mosquito
• Spread Japanese Encephalitis or Viral fever

Questions
• Q1. a. Identify the given spotter?
• Q1. b. give 2 identifying features?
• Q2. diseases transmitted?
• Q3. control measures?
• Q4. Bionomics?

Identifying the Mosquito
1: First, look at the wings. Look at the anterior border of
the wings. If u see spots at the anterior margin of the
wings. Then, the mosquito is an “ANOPHELES”.
2: If no spots are seen on the wings, then look at the
body. If there are white stripes on the body including
the legs, the mosquito is an “AEDES”.
3: If none of the above features seen, then it is a
“CULEX”.

Common Breeding sites for Mosquitoes
 For Anopheles:
Clean & slow moving water, like
 River bed pools, seepages, rice fields, cattle sheds etc.
 For Aedes:
Artificial collection of water, like
 Domestic water storage,
 Water collected for decorative plants
 Discarded food & beverage containers etc.
 For Culex:
 Dirty, polluted & stagnant water, like
Drains, Open manholes, chocked gutters etc.

Control-Measures of Mosquitoes
Anti larval Measures:
• Environmental control
• Chemical control
• Biological control
Anti adult Measures:
• Residual sprays & Space sprays
• Genetic control
• Personal-Protection equipments
• Integrated approach

Environmental - Control
• Source- reduction- filling & levelling of
ditches
• Managing stored water in coolers, vases etc.
• Avoiding artificial water- collection
• Channelization of breeding sources
• Proper covering of stored water
• Water - management (such as intermittent
irrigation & by changing the salinity of water)

Biological Control
By using Larvivorous fish such as:
• Gambusia affinis and
• Lebister reticulatus

Personal Protection Equipments
By using –
• Insecticide Treated Bed-Nets , 150 holes/sq. inch of size
0.0475 inch
• Mosquito- repellant liquids/ ointments/ coils
• Fumigation mats
• Fully covered clothing
• Screening of building with copper or bronze gauze having
16 meshes per inch. The aperture should not be larger
than 0.0475 inch.

Chemical - Control
By using larvicides like:
• Mineral oil in dirty water
• Abate/ temephos in potable water
By using adulticidal Indoor Residual Spray with:
• Malathion or Deltamethrin
• By using Indoor Space spray with Pyrethrum

Larvicidal - Measures
1. MLO (Mineral Oil)- used in dirty water
B:D:K::3:6:1 (weekly application)
Burned Oil- 3 parts
Diesel- 6 parts
Kerosene- 1 part
2. Temephos / Abate- used weekly in potable water
Formulation: (5 ml.+ 2L. Water)
• 30 ml. in overhead tanks
• 10 ml. in Desert coolers
• 500 ml. in 2 lakh L. tank
• 250 ml. in 1 lakh L. tank

Adulticidal Measures
• Pyrethrum (Indoor Space Spray)
(1 L. + 19 L. Kerosene)- Monthly application
• Malathion (Indoor Residual Spray)
(1 L. + 10 L. water)- Quarterly application
• Deltamethrin (Indoor Residual Spray)
(200 ml. + 10 L. water)- Bi-yearly application,
Less toxic, stainless & completely odourless
For Bed-Net Impregnation ( 11 ml. + 1 L. water)
( 6 Monthly application )

Integrated Approach
Combination of some or all the
control measures, like
• Environmental Control
• Biological Control
• Chemical Control
• Genetic Control etc.

Insects other than mosquitoes of
Medical- Importance
1. House fly
2. Sand fly
3. Rat flea
4. Head louse
5. Hard ticks
6. Soft ticks
7. Itch mite
8. Cyclops

Habits of House fly
• Does not bite, attracts to food by its sense of smell
• Does not eat solid food , it vomits on food, making a
solution of “vomit drop” which is a culture of disease
agents
• Vomits & defecates constantly during feeding, cleans its
body very frequently
• Has remarkable capacity to reproduce
• Cannot live more than 48 hours without water
• Disperses upto 6 kms, lives upto 1 month
• Restlessly moves from filth (sputum, feces, wound, pus)
to food. It spreads infection mechanically.
• It has a tendency to rest on vertical surfaces and hanging
objects and to fly towards light.

Diseases spread by House fly
By mechanical transmission:
• Typhoid & paratyphoid fever
• Diarrhea & Dysentery
• Cholera
• Amoebiasis
• Gastroenteritis
• Poliomyelitis
• Conjunctivitis
• Anthrax
• Trachoma
• Yaws

House fly Control Measures
Environmental control:
• Overall improvement of environmental sanitation by
eliminating breeding places
• Storing kitchen waste and garbage in bins with tight
fitting lids
• Efficient & Regular collection, removal & disposal of
refuse by burning or burying (like in a sanitary landfill)
• Hygienic disposal of human & animal excreta
• Stopping open-air defecation
• Keeping surroundings clean

 Chemical Control: (by using Insecticides)
• Adulticide
DDT- 5%
Methoxychlor- 5% Mixed with sugar & sprayed in living
Lindane- 0.5% and breeding places of flies
Sprayed at about 5 liters per 100 square meter of surface
• Residual sprays
• Baits containing Diazinon, Malathion, etc
• Space spray, e.g. with Pyrethrin
• Larvicides:
Diazinon- 2%
Dichlorovos- 2%
Dimethoate- 1%
Sprayed in breeding places of flies

Fly papers: These have an adhesive to
trap the flies.
Personal Protection:
Screening mesh having 14 holes per inch.
 Health Education:
Regarding disease transmission and fly
awareness, we require organized individuals
and community effort.

Identification features of Sandfly
• A small insect with the body divided into
head, thorax & abdomen
• Dark brown & hairy body, smaller than
mosquito, measuring 1.5 to 2.5 mm in
length
• Antennae are long, slender, hairy &
filamented
• Wings are upright and lanceolate in shape

• In the wings, the second longitudinal vein
divides or branches twice. The first branching
takes place in the middle of the wing. This is
characteristic feature of genus Phlebotomus
• Three pairs of legs are very long, slender and
out of proportion to the size of the body.
• The abdomen is intensively hairy, having 10
segments. In the female, the tip of the
abdomen is rounded; and in the male, there
are claspers.

Diseases transmitted by
Sandfly
• Kala-azar
• Sandfly fever
• Oriental sore

Control Measures:
No resistance to DDT has been reported
 By Insecticides:
• Spray with DDT or Lindane is effective.
• Spraying should be done in both human
dwelling and the cattle sheds.
• DDT 1-2 gm/meter square

 By Source reduction:
• Clearing & filling of cracks & crevices in walls and
floors of houses and cattle sheds.
• Removal of shrubs and vegetation within the 50
yards of human dwellings.
• Keeping cattle and poultry outside the house.
 By Personal protection:
• Sand fly net (45 mesh/inch) impregnated with
permethrin.
• Not walking bare feet, using gumboots & by
applying repellents to the legs.

Sandflies may be distinguished from
mosquitoes by the following features
• Size: Sandflies are smaller than mosquitoes.
• Wings: The wings are upright & lanceolate in
shape; the II nd
longitudinal vein branches
twice, the first branching takes place in the
middle of the wing.
• Legs: the legs of Sandfly are longer.
• Hairs: Sandfly is a hairy insect.
• Hopping: Sandfly hops, does not fly .

3. Rat Flea (Xenopsylla Cheopsis)
Identification features:
• Dark brown in colour
• Bilaterally compressed, wingless body,
• Head is conical, attached directly to thorax (no neck)
• Exoskeleton with bristles directed backward
• Body divided into Head, Thorax & Abdomen.
• Head bears piercing mouthparts , which project
downwards
• Thorax bears 3 pairs of strong, spiny legs/ limbs.
• Foot end (claws) turned in opposite direction.

Diseases transmitted by Rat flea
• Bubonic plague is transmitted by bite of rat flea
• Chiggerosis is transmitted by the mechanical
transmission.
• Endemic typhus (or Murine typhus) is
transmitted by the contamination of skin with
the feces of fleas.
• Hymenolepsis diminuta is caused by the
accidental ingestion of the flea.

Control Measures:
Both the rat and rat flea should be destroyed together
• Insecticidal:
-10% DDT dust, where rodent moves & burrows
-2% Diazinon spray
-5% Malathion spray
• Flea repellent:
-Diethyltoluamide & Benzyl benzoate
(Flea control should be followed by rodent
control)
• Rodent control:
-by keeping poisonous bait, trapping,
-emitting hydrocyanic acid gas
-rat proofing.

Head Louse (Pediculus Capitis)
• Dark grayish in colour (colour of hair)
• 1 mm. in size, having head, thorax & abdomen
• Body is dorsoventrally flattened
• The abdomen is elongated and has 9 segments
• Three pairs of legs, no wings.
• Last abdominal segment is bilobed in female
insect and pointed in the male insect.

Habits of Head Louse:
• Ectoparasite of man, infestation is called
“pediculosis”. People in cold climates are
affected more.
• Head louse lives in hair of scalp
• Body louse lives in hair of body and seams of
clothing
• Both sexes lives on the host

Dissemination:
• Directly by contact with lousy person
• Indirectly by using clothes, brush or comb of
lousy person
• Poor personal hygiene
• Overcrowding (school, jail, hostel, closed
communities, etc.) favours the spread
• Children get easily infested at school, when
their heads come together at work or play.

Diseases transmitted by louse:
1. Epidemic typhus
2. Relapsing fever
3. Trench fever
4. Dermatitis, due to scratching and
secondary infection of the site.

Delousing or Control Measures:
• 0.5% Malathion Lotion is applied to head
after hot bath and left on for 12 hours,
followed by washing. 12-24 hour later,
second application is done.
• Improvement in personal hygiene.
• Frequent washing of hair.
• No sharing of combs or brushes.
• Use of clean towels, clothing, bedding, etc.

Preventive Measures:
• Regular bath, washing of clothes,
maintaining proper personal hygiene.
• Health education
• Improving the living standards
• Avoiding contact with the infected
person.

Hard Tick (Ixodidae) Dermacentor
• Oval body, gray white in colour
• Rectangular head at anterior end,
• Head, Thorax, Abdomen are fused or indistinct,
• Head is visible from above
• 4 pairs of legs
• No antennae & No wings
• Dorsal surface covered with chitinous dorsal
shield or “Scutum”.
• The males are generally smaller than females.

Genera of medical importance : (in India)
• Dermacentor andersoni
• Haemaphysalis spinigera
Habitats:
 The hard ticks feed both day & night and cannot
stand starvation
 Both sexes bite & transmit the disease
 Blood sucking ectoparasite , having 3 hosts
(monkey, dog and cattle), remain attached to the
host. The hard ticks are always found on their hosts.

Diseases transmitted by hard ticks:
• Tick typhus
• Viral encephalitis
• Viral haemorrhagic fever
(In India, this viral haemorrhagic fever is
Kyasanur Forest Disease KFD)
• Tick paralysis
• Tularemia
• Human babesiosis

Chemical Control:
 By using Insecticides like :
1. Malathion
2. Lindane
3. DDT
Personal Protection:
 Repellents: Diethyl toluamide, Benzyl Benzoate
 Periodic examination of body & removal of tick
by persons, visiting the tick infected area.

Soft Tick (Argasidae)
Ornithodorus Moubata
• Oval shaped, sufficiently big body
• Head lies ventrally, not visible from above
• No clear distinction of the body into head, thorax
and abdomen
• No antennae & No wings
• 4 pairs of legs
• Dorsal Shield or Scutum is absent, no chitinous
covering.

Genus of soft tick of medical importance ( in India:)
Ornithodorus Moubata
Habits:
• Ectoparasite having multiple host
• Intermittently sucks the blood of mammals
• Soft tick lives in cracks, crevices, bedding,
cattle sheds, human dwellings, etc.
• Soft tick feeds only at night. They can
withstand starvation for long time.
• It transmits relapsing fever.

Comparison of hard & soft ticks
Hard tick
• Scutum present
• Head situated at
anterior end, seen
from above
• Cannot withstands
starvation, feeds day &
night
Soft tick
• Scutum absent
Head lies ventrally,
not seen from above
• Can withstands with
starvation for
year or more, only
feeds at night

Diseases transmitted:
• Q-fever & Relapsing fever
• Kyasanur Forest Disease (KFD)- rarely
• Both sexes transmits the disease.
Control Measures:
• Environmental control :
 Filling up the cracks and crevices.
• Chemical control :
 Insecticide : Lindane, Malathion, DDT,
Pyrethrum dusting on infested animal.

Chemical Control
• By using Insecticide repellent like:
–Diethyltolumide (DEET)
–Benzyl benzoate
Personal Protection by:
• Examination of body frequently
• Wearing full clothing

Itch Mite (Sarcoptes Scabiei)
• Dirty white coloured , extremely small, globular,
tortoise shaped insect
• Round above, flat below
• Body surface has folds (wrinkled) and covered with
short bristles
• No demarcation of body segments
• 4 pairs of short legs:
– 2 pairs in front of the body & bear tubular ends
(suckers)
– 2 pairs behind and these end in the long bristles

Public health importance of Itch mite:
• It causes “Scabies ” which is the first disease of
mankind with a known cause.
• Scabies leads to dermatitis due to secondary
bacterial infection.
Body parts that are commonly affected
by Scabies:
1. Hands & Wrist (63 %) 4. Feet
2. Buttocks 5. Ankles
3. Lower Abdomen 6. Elbows (11 %)

Steps of control of Scabies:
• All the members of the affected household must be treated
simultaneously.
• Before the application of a sarcepticide, a thorough scrub
should be given with soap and hot water.
• One of the following sarcepticides is applied on the body:
1. Benzyl benzoate (25%)
2. Gamma – HCH in coconut or vegetable oil (0.5-1%)
3. Tetmosol solution (5%)
4. Sulphur ointment (2.5-10%)
• Application is repeated after 12 hour.
• 12 hour after the second application, bath is given.
• All infested & close contacts are treated simultaneously.

Cyclops (Water Flea)
• Pear-shaped, semitransparent body, divided
into cephalothorax and abdomen
• Forked tail
• One small pigmented eye (single)
• 1 mm. size – just visible to naked eye
• 2 pairs of antennae & 5 pairs of legs
• In the female, there are bag-like ovisacs on
both sides at the junction of cephalothorax
and the abdomen

Habits:
• Lives in freshwater and acts as an intermediate host
Public health importance:
• It transmits Guinea- worm disease , now eradicated
in India. WHO declared India as free of guinea
worm disease in the year 2000.
• It is the intermediate host for the parasite.
Diseases transmitted are:
• Guinea worm disease
• Fish tape worm (Diphyllobothrium karvei) infestation

Control Measures:
1. Physical measures:
– Straining the drinking water through fine muslin cloth/ nylon cloth
or strainer.
– Boiling the water before drinking.
2. Chemical measures:
Chlorination upto strength of 5 ppm followed by de chlorination.
– Lime - 4 g per gallon of water.
– Abate – 1 mg per liter of water.
3. Biological measures:
– Fish which feed on Cyclops such as Gambusia affinis and Lebister
reticulatus.
4. Permanent or Legislative measures:
– Abolishing / conversion of step wells.
– Providing safe drinking water and health education.

1. Write the type of given insecticide
2. What is the mechanism of its action?

vector bionomics community medicine powerpoint

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