This document provides an overview of medical entomology. It defines entomology and medical entomology, and discusses the importance of studying arthropods that affect human and animal health. It covers the classification of medically important arthropods like mosquitoes, flies, ticks, mites and sand flies. The document discusses different disease transmission cycles and highlights important vector-borne diseases like malaria, dengue, Japanese encephalitis, filariasis, kala azar and diseases transmitted by the house fly. It also provides details on the biology, identification and control of major vector species like Anopheles, Aedes, Culex, sand flies and the house fly.

1. MEDICAL
ENTOMOLOGY
Vikas Gupta
1st
year postgraduate

2. Contents
• Introduction
• Definitions
• Importance of study
• Classification of arthropods
• Disease transmission
• Mosquitoes
• Other medically important vectors
• Recent outbreaks
• Research centres for medical entomology

3. Introduction
• Insects - These weird looking creatures that
have existed even before mankind. There
existence has always bemused human beings.
• Never judge them by their size. The small size
innocuous looking creature have time and
again created havoc and sometime even
challenged the supremacy of human being.

4. Introduction
• Alexander the Great, conqueror of many nations, was
vanquished by the bite of a tiny mosquito bearing malaria
parasites
• The Black Death, decimator of Europe, killer of tens of
millions worldwide was the work of a tiny flea vectoring the
bacilli that cause bubonic plague from rats to people.
• Western countries are a step ahead of asian countries that is
reflected in movies too as they think arthropods can conquer
earth over human species that’s why they have considered
them as aliens .

6. Definitions
• Entomology: It is a science that deals with the study of
arthropods in general, and incorporates sciences like zoology,
biology, parasitology and micro-biology.
• Medical entomology: Branch of entomology which deals with
arthropods which affect the health and well-being of man and
vertebrate animals.
• In other words, medical entomology is the medical science
directly concerned with vectors that affect human and animal
health.

7. Introduction
• Origin of word mosquito was from musca(latin)> Mosca
(portugese)> Mosquito (spanish).
• There are about 3000 species of mosquito, of which about 100
are vectors of human diseases
• Mosquitoes and ticks account for the majority of transmissions
of the most important vector-borne diseases, although some
close relatives of mosquitoes also get involved, including sand
flies and black flies
• Worldwide there are 380 species of Anopheles, 950 species of
Aedes and 550 species of Culex

8. Introduction
• Insects have huge impact on
health of humans & domestic
animals
– Irritation & diseases
• Relatively few species involved
but serious social & economic
consequences
– Transmit diseases (vectors)
– Inject venoms & transmit
allergens
– Cause wounds
– Create nuisance & phobias
Leishmaniasis
Myiasis

9. Why study of this is important?
• Malaria: 4-5million cases/year
• 236 million and 5 million people living in filaria and guinea
worm disease endemic areas respectively
• Scabies widespread especially in rural areas
• Prevalence of trachoma ranges from 0.5% in West Bengal to
79% in Punjab and Haryana

10. 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, Oriental sore, Sandfly fever
6 Tsetse fly Sleeping sickness
7 Louse Epidemic Typhus, Relapsing fever, Pediculosis
8 Rat flea Bubonic Plague, Chiggerosis, Endemic typhus
9 Reduvid bug Chagas disease
10 Hard tick Tick typhus, Viral encephalitis
11 Soft Tick Q fever, Relapsing fever
12 Trombiculid mite Scrub typhus, Rickettsial pox

11. Classification

13. Classification

14. Distinguishing features

15. Transmission of Arthropod
borne diseases
TransmissionsTransmissions
Direct Contact
From man to man
Scabies
pediculosis
Direct Contact
From man to man
Scabies
pediculosis
Mechanical
Diarrhea
Dysentery
Typhoid
Trachoma
Mechanical
Diarrhea
Dysentery
Typhoid
Trachoma
BiologicalBiological
Propagative
Only multiplication
No developmental
Plague bacilli in rat
flea
Propagative
Only multiplication
No developmental
Plague bacilli in rat
flea
Cyclo-propagative
Multiplication
developmental
Malaria parasites in
mosquito
Cyclo-propagative
Multiplication
developmental
Malaria parasites in
mosquito
Cyclo-developmental
No multiplication
developmental
Filaria parasite
in mosquito,
Guineaworm in cyclops
Cyclo-developmental
No multiplication
developmental
Filaria parasite
in mosquito,
Guineaworm in cyclops

16. Transmission of Arthropod
borne diseases
Trans-ovarian/ Trans-stadial transmission:
•It is a type of disease transmission, whereas the causative agent
is transmitted to the immature stage (usually to the egg) from the
adult insects and / or other arthropods which carry disease
pathogens.
•e.g Ticks and sand flies
Pathogens transferred by arthropods
– Viruses (arboviruses)
– Bacteria (also rickettsias)
– Protozoan parasites
– Filarial nematode worms

17. General disease cycles
• Biologically transferred diseases
– Blood-feeding adult arthropods transmit parasites
• Animal to animal
• Human to human
• Animal to human
• Human diseases have single or secondary cycles
• Single cycle : Pathogen completes life cycle only within
vector & human host. e.g Human malaria

18. General disease cycles
• Secondary cycle : Pathogen completes life cycle within vector
& animal or human host
– Non-human vertebrates are primary hosts
• Monkeys (yellow fever); rats (plague); desert rodents
(leishmaniasis) etc
– Animal diseases that affect man = zoonoses
– Human inclusion in cycle is not essential to maintain
disease & animals act as disease reservoirs
– Outbreaks occurs when humans spread into natural ranges
of vectors & disease reservoirs

19. Mosquitoes
1-8
9-10

20. Anopheles Culex
Aedes
Mansonia

21. Life cycle
Feeding
Stage
Quiescent
transformation
stage
Reproductive
Stage
2-3 d 5-7 d 1-2 d

22. EGG Anopheles Aedes Culex Mansonia
Laying On water surface Above or near
water surface
On water surface Attached to
undersurface of
leaves (pistia)
Hatching time 2-3 days 2-3 days 2-3 days 2-3 days
Position Float Float Float Float
Number Single Single Rafts of 100 or
more eggs
Cluster
Shape Boat shaped,
paired lateral
floats, elongated
Cigar shaped - Star shaped
cluster

23. Larva Anopheles Aedes Culex Mansonia
Float Horizontally Suspended Suspended Suspended
Siphon tube - + + +, attached to
rootlets
Life 2 days 5-7 days 5-7 days 5-7 days
Pupa
Shape Comma shaped Comma shaped Comma shaped Comma shaped
Siphon tube Short and broad Long and narrow Long and narrow Long and narrow
Life 1-2 days 1-2 days 1-2 days 1-2 days
Adult
Life 4 weeks 3 weeks 4 weeks 4 weeks
Resting position Inclined 45* Hunch back Hunch back Hunch back
Wings Spotted Unspotted Unspotted Unspotted
Palpi Long in both sex Short in female Short in female Short in female
Noise - + + +

25. Behaviour
Habits Anopheles Culex Aedes Mansonia
Feed on Anthropophilic
and zoophilic
Anthropophilic Anthropophilic Anthropophilic
Biting time Evening or early
part of night
Midnight Day biters Night
Feeding place Indoor Outdoors In and around
houses
Outdoors
Resting place Indoor rester-
cattle sheds and
human dwellings
Outdoors Dark and quit
places,
bedrooms,
kitchen
Outdoors
Breeding place Clean water,
ponds, pools,
lakes,
Spring, overhead
tanks
Dirty water
collections,
stagnant drains
Cesspools
Septic tanks
Burrow pits
Artificial
accumulation of
water, tyres,
Broken glasses
Aquatic plants
Flight 0.75-1 km 11 km <100 m -

26. Anopheles

27. 27
Aedes

28. Anopheles
• Anopheles 45 species in India
• 7 are vectors of malaria
1) An. Culicifacies:
• It is most important vector in malaria transmission in India & very widely
distributed in RURAL area of North, South and Central India
2) An. Stephensi: it is normally vector for URBAN area, particularly in
coastal region.
3) An. Minimus: in N.E. states, North West Bengal
4) An. Fluviatilis: seen along Himalaya range seepage and in irrigation
channels.
5) An. Dirus: deep forest in N.E. region.
6) An. Sundaicus: Andaman and Nicobar Island
7) An. Philippinensis: is the vector for the plains of West Bengal and N.E.
region.

30. MALARIA

32. Vector Control
• Chemical Control
1. Use of Indoor Residual Spray (IRS) with insecticides
recommended under the programnme
2. Use of chemical larvicides like Abate in potable water
3. Aerosol space spray during day time
4. Malathion fogging during outbreaks
• Biological Control
1. Use of larvivorous fish in ornamental tanks, fountains etc.
2. Use of biocides

33.  Larvivorous Fish
Advantages
 Environmental friendly
 Easy to introduce
 Self propagating & self sustainable
 User friendly
 Helps build community participation &
intersectoral collaboration
 Cost-Effective - no recurrent costs
Limitations
• Extremes of temperatures and pollution
• Suitable for some types of breeding sources only
• Needs proper planning with mapping of breeding
sources & promotional efforts
Lebister reticulatus
Gambusia affinis
Aphanius dispar
• Biolarvicide: Bacillus thuringiensis
iserailensis (Bti)-Endotoxin : 2.5%
suspension, 1 lit/50 m2, once every 2
weeks.

34. • Personal Prophylatic Measures that
individuals/communities can take up
1. Use of mosquito repellent creams, liquids, coils, mats etc.
2. Screening of the houses with wire mesh
3. Use of bednets treated with insecticide
4. Wearing clothes that cover maximum surface area of the body
• Environmental Management & Source Reduction Methods
1. Source reduction i.e. filling of the breeding places
2. Proper covering of stored water

36. Indices
• Malarial vector indices
1. Human blood index = proportion
of freshly fed female anopheles
showing human blood in their
stomach
2. Sporozoite rate = % of female
anopheles having sporozoites in
their salivary glands
3. Mosquito density = no. of
mosquitoes/ man hour catch
4. Man biting rate = avg. incidence
of anopheles bite/ day
5. Inoculation rate = 2*4
• Larval surveys of Dengue
• House index = % of house
infected with larva/pupae
• Container index = % water
holding containers infested with
larva/pupae
• Breateau index = no. of +ve
container/100 houses inspected
• Pupae index = no. of pupae/100
houses inspected

37. Culex

38. JE

40. F
I
L
A
R
I
A
S
I
S

41. Vector control
1. Recurrent anti-larval measures at weekly intervals.
2. Environmental methods including source reduction by filling
ditches, pits, low lying areas, deweeding, etc.
3. Biological control of mosquito breeding through larvivorous
fish.

42. Mosquito-borne diseases and their
vectors (protozoa and nematode disease)
Disease Pathogen Vector species
Malaria Plasmodium vivax Anopheles sp.
P. falciparum
P.malariae
P. ovale
Filariasis Wuchereria bancrofti Culex
quinquefasciatus
Anopheles sp.
Brugia malayi Mansonia sp.
Aedes togoi
Anopheles sinensis

43. Mosquito-borne diseases and their
vectors (virus disease)
Disease Pathogen Vector species
Virus
JE JE virus Culex
tritaeniorhynchus
Culex fuscocephala
Culex gelidus
Culex vishui
Culex pseudovishui
Dengue Dengue Aedes aegypti
Dengue virus Aedes albopictus
hemorrhagic

44. AEDES

46. DENGUE

48. Vector control
1. PERSONAL PROPHYLATIC MEASURES
•Use of mosquito repellent creams, liquids, coils, mats etc.
•Wearing of full sleeve shirts and full pants with socks
•Use of bed nets for sleeping infants and young children during day
time to prevent mosquito bite
2. BIOLOGICAL CONTROL
•Use of larvivorous fishes in ornamental tanks, fountains, etc.
•Use of biocides
3. CHEMICAL CONTROL
•Use of chemical larvicides like abate in big breeding containers
•Aerosol space spray during day time

49. 4. ENVIRONMENTAL MANAGEMENT & SOURCE
REDUCTION METHODS
•Detection & elimination of mosquito breeding sources
•Management of roof tops, sunshades
•Proper covering of stored water
•Reliable water supply
•Observation of weekly dry day
5. HEALTH EDUCATION
•Impart knowledge to common people regarding the disease and vector
through various media sources like T.v., Radio,Cinema slides, etc.
6. COMMUNITY PARTICIPATION
•Sensitizing and involving the community for detection of Aedes
breeding places and their elimination

50. Sand flies
• Species
 Phlebotomous argentipes (kala
azar)
 P. papatasii (sandfly fever,
oriental fever)
 P. sergenti (oriental fever)
 Sergentomyia punjabensis
(sandfly fever)
• Transmit several pathogens
 Protozoa (leishmaniasis)
 Arboviruses (pappatassi fever)
 Bacteria (oroya fever)
Eggs Laid in Damp and
dark places
Torpedo shaped
longitudinal wavy
lines
Hatch in 7 days
Larva 2 weeks
Pupa 1 week
Adult avg life 2 weeks

51. Sand flies
•Identification
– Small cryptic flies (2-4 mm)
– Very broad & hairy wings with long
parallel veins, lanceolate shaped
– Wings held open over body
– Adults hide in cracks in walls, rat
burrows during day; enter houses at
night to feed
– Adults & larvae live near water
– Larvae live in moist soil or in cracks
& crevices where they survive on
condensed water

53. KALA AZAR
Vector control
through IRS with
DDT up to 6 feet
height from the
ground twice annually

55. House fly
• Identification
– Thorax dark longitudinal
striped
– Tenent hairs secrete sticky
substance
• Biology
– Larvae live in various types of
organic matter; manure,
garbage, rotting vegetation
– Nuisance flies
– Mechanical disease
transmitters

56. • Mode of transmission
1. Mechanical : also called as
Porters of infection
2. Vomit drop
3. Defecation
Egg laid 120 -150
Colour Pearly white,
1mm long
Hatching time 8-24 hrs,
in summer 3 hrs
Larva(maggot) White 2-7 days
Pupa Dark brown,
barrel shaped
3-6 days
Adult 15 days (summer)
25 days(winter)
Life cycle 5-6 days (summer),
8-20 days(winter)
Breeding place Human excreta,
manure of animals,
garbage
Feeding habits Sputum, feaces,
discharges from
wound, open sores
Resting habits Rest on vertical
surfaces, hanging
objects
Dispersal Upto 4 miles
– Such species mechanically
transfer bacteria & viruses
• Cholera, poliomyelitis,
leprosy, typhoid fever,
dysentery etc

57. House fly
– Non-biting species - short fleshy proboscus for mopping up
surface liquids
– Some species extract fluids from human food & faeces (e.g.
Musca domestica, M. vicinia, M. nebulo, M. sorbens)
– Others feed on wounds or run off from wounds
– Some involved in myiasis
– Vector control:
1. Environmental control
2. Residual spray
3. Baits, cords/ribbon
4. Fly papers
5. Health education

58. Black flies
– Eggs laid on submerged stones and water weeds
– Larvae attach to rocks & vegetation (via silk & hooks)
– Pupate on rocks underwater (1-3 wks)
– Adults may occur several km(100 miles) from water
– Simulium indicum in India
– In tropical Africa Simulium damnosum transmit
filarial worms that cause river blindness
(onchocerciasis) in humans
– Vector control:
– Abate as antilarval methods
Aquatic larva

59. Tsetse flies
• Found only in African continent
• Regions affected with tsetse flies
are called ‘fly belt’
– Transmit protozoans
(Trypanosomes gambiense)
• Sleeping sickness/ african
trypanosomiasis (humans)
• Riverine species
 Glossina palpalis &
 G. tachoinoides
Savannah species
 G. morsitans &
 G. pallidepes
Tsetse bite

60. Tsetse flies
• Biology
– Adults active during day
– Occupy habitats with trees
(e.g. grasslands & woodlands)
– Both sexes feed on large
mammals; humans only
attacked in absence of game
– Rarely enter houses
– Females incubate single
maggot in their bodies
• Nourished by ‘milk
gland’
• Larvae pupate in soil;
very soon after deposited
Typical tsetse habitat
Larva life Few hours
Pupa 20-40 d
Adult < 100 d

61. Tsetse flies
• Vector control
1. Insecticidal spray DDT25%
2. Clearing vegetation
3. Game destruction
4. Genetic control- sterile male technique

62. Reduvid bug
• Identification
• Large robust bugs, ambush
predators of arthropods
• Strong recurved beak for biting
Inject paralytic toxin to subdue
• Live in woodland & forest
habitats
• Colonized human dwellings
• Live in ceilings, cracks &
crevices etc.
• Attack humans at night
• Most notorious species are
Triatoma infestans & Rhodnius
prolixus

63. Reduvid bug
• Medical importance
Bites very painful to humans, may
cause intense itching, nausea, flushed
face, palpitation
Mexico , central and South American
subfamily Triatominae (kissing bugs)
feed on human & animal blood and
spread protozoans (trypanosoma
cruzi) which cause Chagas’s disease
(American trypanosomiasis)
Residual spray with lindane for
vector control
Triatoma infestans
Rhodnius prolixus

64. Lice
• Small, flattened & wingless
• Short stout legs; end in strong claws
• Permanent ectoparasites on birds & mammals
• Biology
– Entire life cycle occurs on host, Eggs (nits) are cemented
onto host’s hair or feathers
– Transmission via contact between hosts
Life cycle 3 stages
15-17 days
Egg/ nits Ovoid bodies 4-9 eggs/day
Hatch in 6-9 days
No hatching if t < 22*
Larva/ nymph 10-15 days
Adult 30-50 days

65. Lice
• Pthiridae (crab lice, pubic lice)
– Single species (Pthirus pubis)
confined to human pubic region
• Bites cause irritation &
typical rash
• Spread by close body
contact (usually sex)
• No diseases transmitted
• Pediculidae (human lice)
• Very similar but differ in
habits
• Bite severely and Annoying
pests
• Infestation is called as
pediculosis
Crab louse
Rash caused by infestation

66. Lice
• Head lice
– Suck blood from scalp & lay eggs on hair
– Common & easily spread by close contact,
sharing of combs, brushes, hats etc
• Body lice
– Suck blood from body & lay eggs on
clothing
– Uncommon & spread by bodily contact,
sharing of clothing or bedding
– Vector diseases (epidemic typhus, trench
fever, relapsing fever)
– dermatitis
• Lousiness related to sanitation
– Crowded conditions
– Long periods without bathing or changing
clothes
Nits on human hair

67. Fleas
• Small, laterally flattened,
wingless insects
• Large hind legs &
spectacular jumps
• Parasitic on birds &
mammals
– Many pest species occur
worldwide
• Human flea (Pulex
irritans)
• Oriental rat flea
(Xenopsylla cheopis)
• Tunga penetrans
(sand fleas)

68. Fleas
• Biology
– Eggs are laid in host’s nest or
habitat; eggs laid on host will drop
off
– Larvae are slender, whitish & legless
(maggot-like)
– Pupae are dormant for several
months
• Hatch in response to vibrations
from host’s movement
– Adults are very active
• Move freely on host & between
hosts
• Can survive off host for long
periods

69. Jigger or chigoe fleas
• Tunga penetrans
– Very small (<1 mm)
– Females burrow into skin of humans
& other mammals; usually on feet
• Soft areas between toes
• Under toenails
• Condition called tungiasis
– No diseases transmitted
– Present in western part of india

70. Jigger or chigoe fleas
• Tungiasis
– After mating, females become permanently
imbedded in skin
• Breathe, defecate & expel eggs through
small opening at back end
• Abdomen becomes greatly distended as
eggs develop (swells to size of small
pea)
– Host tissue becomes inflamed & swells to
form boil-like sore
• Cause intense itching & bacterial
infection
• Sores may develop into bad lesions
• Can cause loss of digits, septicaemia &
lameness
• Tetanus and gas gangrene because of
2* infection

71. Rat fleas
• Rat fleas (oriental)- murine typhus/ bubonic plague
 Xenopsylla cheopis
 X. astia
 X. braziliensis
• Rat fleas(temperate)
 Nosopsylla fasciatus

72. Rat fleas
• Mode of transmission
 Biting( mainly in plague) blocked flea bites due to multiplication of plague
bacteria in proventricularis and blocking it
 Mechanical
 Feaces
• Flea index
 General flea index= avg no. of all species/ rodent
 Specific flea index= avg no. of each species/rodent
 Percentage incidence of flea species= % of fleas of each species/ rodent
 Rodent infestation rate= % of rodents infested with various flea species
Vector control
1. 10% DDT dusting
2. Residual spray upto 1 ft height
3. Repellents
4. Rodent control

73. Ticks
A. Soft Ticks (Ornithodorus/ argasidae)
Soft Ticks are vectors for serious disease including :
1. Tick borne relapsing fever (Borrelia duttoni)
2. Rickettsial disease (Coxiella burneti), and some arboviruses
B. Hard Ticks (Ixodes, Amblyomma, Rhipicephalus,Dermacentor)
1. Dermacentor and Amblyomma- Rocky Mountain Spotted
Fever (Rickettsia rickettsia)
2. Dermacentor - heamorrhagic fevers.
3. D. variabilis Tularaemia, Mediterranean Spotted Fever, African
Tick Typhus
4. Ixodes : Borrelia burgdorferi = Lyme disease, Babesia =

75. Mites
• Genus: Dematophagoides, Leptotrombidium, Sarcoptes
• Dematophagoides, is a common dust mite, inhabit beds,
mattresses, carpets and house dust causes asthma, conjunctivitis
and dermatitis.
• Trombiculid mites
• Spider like
1. Leptotrombidium deliense
2. L. akamushi
• larval stage is the only parasitic stage of the mite's life cycle
• Causes scrub typhus
• O. tsutsugamushi pathogen
• characteristic black eschar

76. Itch mite(scabies)
• In 1687 first disease of man with known cause
• Animal scabies can not flourish on human skin
• Female burrows into epidermis
• Body tortoise shaped
• Site of lesions
1. Hands and wrist 63%, Extensors of elbow 10.9%
2. Axillae, buttocks, lower abdomen, feet and ankles, palms in children
most common site
3. Breasts and genitals

77. Itch mite(scabies)
1. Permethrin lotion is the treatment of choice, Ivermectin has
been recommended for Norwegian scabies
2. Malathion liquid can also be used, benzyl benzoate is also
active
3. Normal laundering of bed linen and clothes is recommended
4. Household and sexual contacts should also be treated

78. Cyclops/ water flea
• Fresh water
• Pear shaped
semi transparent
body
• Avg life 3 months
• Diseases: acts as
intermediate host for:
1. Guinea worm disease
(dracontiasis)
2. Fish tape worm
(diphyllobothrium latum)

79. Recent outbreaks

80. Research centres for medical
entomology
1. Centre for Medical Entomology and Vector Management. NCDC, Delhi
2. Centre for Research in Medical Entomology, Madurai
3. Vector Control Research Centre, Puducherry
4. National Institute of Malaria Research, Dwarka, Delhi
5. Central Drug Research Institute, Delhi
6. International centre for Genetic Engineering and Biotechnology, Delhi
7. Malaria research centre, Delhi
8. National Institute of Communicable Diseases, Delhi
9. Regional Medical Research Centre, Assam
10. Centre of Advanced Studies, Bangalore
11. Jamnalal Bajaj Tropical Disease Research Centre, Sevargam
12. Rajendra Memorial Research Institute of Medical Sciences, Bihar