1. Rumala Morel
Dept. of Parasitology
Peradeniya
Y2S2
Mosquitoes of Medical
Importance in Sri Lanka
Aedes
Anopheles
Culex

2. MEDICAL ENTOMOLOGY
Study of insects and other
arthropods of medical importance
Insects: Mosquitoes, Flies, Midges,
Lice, Bugs, Fleas
Other arthropods: Ticks and Mites

3. Objectives:
 List the major mosquito borne diseases
that occur globally
 List the mosquitoes of medical importance
in Sri Lanka indicating the diseases they
transmit
 Outline the life cycle of a mosquito
 Describe the breeding & biting habits of
the medically important mosquitoes in Sri
Lanka
 Outline the strategies used for control of
these mosquito species in Sri Lanka

4. Anophelines
-Anopheles
Mosquitos – found globally in all climates
>3000 spp. only few of medical importance
 Culicines - Culex
- Aedes
- Mansonia
- Armigeres

5. Role of mosquitoes in disease transmission
2500 yrs ago Susruta suggested
transmission of malaria by mosquitoes
but no definite proof until end of 19th
C
1859- James Emerson Tennent in
‘Ceylon: An account of the island’
….retiring punctually at sunset and
sleeping under mosquito ‘curtain’ is a
valuable prophylactic against fevers…

6. Medical importance of Mosquitoes
 biting nuisance- pests/allergy
 vectors of disease
transmit disease causing organisms
Mosquitoes as biological vectors
Essential part of the life cycle takes place in
the vector- multiplication or development
or both
Specific time period necessary
before vector can infect another host

7. Mosquitoes as vectors of disease:
some important discoveries
1878 Patrick Manson- filarial
parasites
1897 Ronald Ross- malaria
1900 Reed & team- yellow fever
1902 Graham- dengue

8. Aedes aegypti Dengue Dengue viruses
Chikungunya Chikungunya virus
A.albopictus Dirofilariasis Dirofilaria repens
Mosquito borne diseases in Sri Lanka
MOSQUITO DISEASE INFECTIVE ORGANISM
Anopheles culicifacies Malaria Plasmodium spp.
Culex quinquefasciatus Bancroftian Wucheraria bancrofti
filariasis
C. gelidus Japanese Jap Encephalitis virus
C. Tritaeniorynchus encephalitis
C.pseudovishnui
Yellow fever – globally impt. mosq.borne disease
Not found in SL

9. Biological characteristics influencing
disease transmission
 only females suck blood (blood required for
egg maturation)
 breeding habits: preferred water type
 host preference – anthropophilic
- zoophilic
 blood sucking behavior- daytime/night
indoor/outdoor
 survival- 3-4 weeks (to allow development of
pathogen)
 flight range- 0.5 - 1.5 km

10. Morphology of adult mosquito

11. SEX DETERMINATION - Antenna
Classification of mosquitoes -1. SEX
"plumose" (hairy) - male
"pilose" (not very hairy)
female

12. Palps (sensory organs just lateral to the proboscis)
Classification of mosquitoes – 2. GENERA
A female mosquito
with long palps = Anopheles
A female with
short palps =
Culicine
Anopheles mosquitoes
rest and bite with their
bottoms up @ 45 degree
angle to the skin

13. Life span
1 month
150-300
laid every 48-72 h
4 stages
1-3 weeks
2-3 days
2-3 days
Mosquito
Life Cycle
Water is
essential
for breeding

14. Eggs:
laid singly
with floats
Eggs:
in clusters
Larvae:
parallel to
surface
no siphon
tube
Larvae:
siphon tube +
Adult: rests @
45º angle to
surface
Adult: rests
parallel to
surface

15. Aedes rests parallel to surface
Anopheles culicfacies also
rests parallel to surface like culex

16. Anopheles species of importance in Sri Lanka
An. culicifacies- major vector of malaria
vectors of minor importance
An. subpictus
An. annularis
An. vagus
An. tesselatus
Major vectors in other countries
An. gambiae- vector of human malaria and
Bancroftian filariasis in Africa

17. Characteristics of importance for a malarial vector
 density
 longevity
 biting habits- anthropophilic (man
biting)
- outdoor/indoor
night biting mosquitoes
Keys/charts used for species identification
Rests on walls – Indoor Residual Spraying
Effective control method

18. Anopheles culicifacies
Distribution: Sri Lanka, India, Myanmar
Pakistan, Middle East, Nepal, Thailand
Adult: small- medium
wings & female palps - banding
resting position culicine-like
Breeding: shallow, sunlit, clear fresh water
Eg. Edges of slow flowing streams/rivers;
rain water collections in ground pools and pits

19. Dry zone: endemic species
present throughout year but high
densities with rains (NE monsoon Oct-Jan)
Intermediate zone: seasonal breeding
Wet zone: not normally found but breeding
occur with failure of monsoons due to
pooling in river beds
Found up to 900 m height
Distribution in Sri Lanka
Anopheles culicifacies

20. Rain water collections in pits,
construction sites, hoof prints
in dry zone
Stream/river bed pools;
seepage pools at
margins of lakes,
reservoirs;
open irrigation canal
margins

21. Malaria vector breeding
in quarry pits
Kurunegala (NWP) and
Anuradhapura (NCP)

22. Malaria vector breeding in Agro wells
Matale, Anuradhapura district

23. Wet zone-
rock/sand river bed pools during droughts
pooling below dams/barrages
Kotmal oya- below dam

24. malaria vector breeding downstream of dams
-An. culicifacies

25. Below dam at Nilambe oya
Ilagolla- malaria outbreak
due to mosquito vector
breeding in rock pools

26. Culicines- 20 genera
In Sri Lanka > 115 species
 Culex
 Aedes
 Mansonia
 Armigeres

27. Culex quinquefasciatus
Very common urban domestic mosquito throughout
South/SE Asia- vector of bancroftian filariasis
Small, brown, absence of markings
Breeding: eggs in rafts (75-100 eggs)
highly polluted (organic matter) stagnant water
eg. blocked drains, cess pits, waste water pits
Habits: night biter, outdoor/indoor
bites man, cats/dogs
Rests in shade eg. indoors in dark corners
clothes, under furniture etc.

28. Culex quinquefasciatus Biological vector
Lymphatic filariasis:
Microfilaria ingested with the blood meal develop into
Infective larvae L3 in 10-12 days and emerge from
proboscis during the bite
ONLY development NO multiplication

29. Breeding sites of Culex quinquefasciatus
Stagnant,
polluted water
(sewage)

30. Culex quinquefasciatus breeding sites
Dirty water in blocked drains, cess pits etc.

31. Culex tritaeniorhynchus
Cx. gelidus
Cx. pseudovishnui
Breeding: paddy fields, marshes,
husk-soakage pits
Habits: night, outdoor/indoor
bites animals; pigs/cattle
(zoophilic)
Vectors of Japanese encephalitis

32. Japanese encephalitis:
Epidemiological cycle
Pigs important amplifier hosts
Mosquito vectors:
Cx. tritaeniorhyncus;
Cx.pseudovishnui- paddy
field breeders
Cx. gelidus- muddy pools
husk pits

33. Japanese Encephalitis
Culex gelidus

34. Vectors of Japanese encephalitis breed in paddy field

35. Aedes spp.
Ae. aegypti Ae. albopictus
Small, delicate, black & white banding on legs.
wings clear
Vectors of-
Dengue fever, Chikungunya, Dirofilaria repens
Yellow fever (not in Sri Lanka)
Breeding: eggs laid singly (no floats)
damp surfaces that get submerged
rain water collections in containers

36. Vectors of
Dengue & Chickungunya
Aedes aegypti
Ae albopictus
Container breeders, clean water
artificial- tyres, tin cans, plastic waste
Indoors- flower vases etc.
Natural- cut bamboo stumps, leaf axils

37. SL: dengue endemic since 1989
Transovarian transmission of arboviruses
Aedes breeding sites

38. Aedes breeding in households
indoors
outdoors

39. Aedes
Breeding
outdoors

40. Vector of Brugian filariasis
& Dirorfilariasis
Water plants:
Pistia
Eichornia
Salvinia
Mansonia spp.
M uniformis
M annulifera
Brown, speckled wings (light/dark scales)
Breeding: aquatic plants
eggs laid in clusters on undersurface
leaves of water plants
Larvae/pupae attached to plant roots

41. Armigeres subalbatus
Very common dusk/night biter
Pest & vector of Dirofilaria repens
Breeding: polluted water
Dirofilariasis
Dirofilaria repens: common
parasite of dogs
transmitted
by Aedes,
Armigeres,
Mansonia
Causes subcutaneous
nodules in humans

42. Reduce mosquito density
Pathogen control in humans
Prevent man-mosquito contact
Control of mosquito borne diseases

43. Reduce vector density 1
Adult control – Malaria control
(1) Insecticide impregnated
bed nets – treat every 6/12
(2) Indoor Residual Spraying

44. Reduce vector density 2
Eliminate breeding sites
Destroy larvae
Aedes spp.
• Properly dispose of old tires, cans, bottles,
water-collecting rubbish, and other
unused/unwanted containers.
• Eliminate breeding in standing pools of water
Eg. air conditioners, refrigerators – add surface
oil layer
• Clean birdbaths, vases, plant pots, rain
barrels, kiddie pools etc. ONCE A WEEK

45. Summary
Mosquitoes of
Medical Importance
Aedes
Anopheles culicfacies
Culex