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  1. 1. Rumala MorelDept. of ParasitologyPeradeniyaY2S2Mosquitoes of MedicalImportance in Sri LankaAedesAnophelesCulex
  2. 2. MEDICAL ENTOMOLOGYStudy of insects and otherarthropods of medical importanceInsects: Mosquitoes, Flies, Midges,Lice, Bugs, FleasOther arthropods: Ticks and Mites
  3. 3. Objectives: List the major mosquito borne diseasesthat occur globally List the mosquitoes of medical importancein Sri Lanka indicating the diseases theytransmit Outline the life cycle of a mosquito Describe the breeding & biting habits ofthe medically important mosquitoes in SriLanka Outline the strategies used for control ofthese mosquito species in Sri Lanka
  4. 4. Anophelines-AnophelesMosquitos – found globally in all climates>3000 spp. only few of medical importance Culicines - Culex- Aedes- Mansonia- Armigeres
  5. 5. Role of mosquitoes in disease transmission2500 yrs ago Susruta suggestedtransmission of malaria by mosquitoesbut no definite proof until end of 19thC1859- James Emerson Tennent in‘Ceylon: An account of the island’….retiring punctually at sunset andsleeping under mosquito ‘curtain’ is avaluable prophylactic against fevers…
  6. 6. Medical importance of Mosquitoes biting nuisance- pests/allergy vectors of diseasetransmit disease causing organismsMosquitoes as biological vectorsEssential part of the life cycle takes place inthe vector- multiplication or developmentor bothSpecific time period necessarybefore vector can infect another host
  7. 7. Mosquitoes as vectors of disease:some important discoveries1878 Patrick Manson- filarialparasites1897 Ronald Ross- malaria1900 Reed & team- yellow fever1902 Graham- dengue
  8. 8. Aedes aegypti Dengue Dengue virusesChikungunya Chikungunya virusA.albopictus Dirofilariasis Dirofilaria repensMosquito borne diseases in Sri LankaMOSQUITO DISEASE INFECTIVE ORGANISMAnopheles culicifacies Malaria Plasmodium spp.Culex quinquefasciatus Bancroftian Wucheraria bancroftifilariasisC. gelidus Japanese Jap Encephalitis virusC. Tritaeniorynchus encephalitisC.pseudovishnuiYellow fever – globally impt. mosq.borne diseaseNot found in SL
  9. 9. Biological characteristics influencingdisease transmission only females suck blood (blood required foregg maturation) breeding habits: preferred water type host preference – anthropophilic- zoophilic blood sucking behavior- daytime/nightindoor/outdoor survival- 3-4 weeks (to allow development ofpathogen) flight range- 0.5 - 1.5 km
  10. 10. Morphology of adult mosquito
  11. 11. SEX DETERMINATION - AntennaClassification of mosquitoes -1. SEX"plumose" (hairy) - male"pilose" (not very hairy)female
  12. 12. Palps (sensory organs just lateral to the proboscis)Classification of mosquitoes – 2. GENERAA female mosquitowith long palps = AnophelesA female withshort palps =CulicineAnopheles mosquitoesrest and bite with theirbottoms up @ 45 degreeangle to the skin
  13. 13. Life span1 month150-300laid every 48-72 h4 stages1-3 weeks2-3 days2-3 daysMosquitoLife CycleWater isessentialfor breeding
  14. 14. Eggs:laid singlywith floatsEggs:in clustersLarvae:parallel tosurfaceno siphontubeLarvae:siphon tube +Adult: rests @45º angle tosurfaceAdult: restsparallel tosurface
  15. 15. Aedes rests parallel to surfaceAnopheles culicfacies alsorests parallel to surface like culex
  16. 16. Anopheles species of importance in Sri LankaAn. culicifacies- major vector of malariavectors of minor importanceAn. subpictusAn. annularisAn. vagusAn. tesselatusMajor vectors in other countriesAn. gambiae- vector of human malaria andBancroftian filariasis in Africa
  17. 17. Characteristics of importance for a malarial vector density longevity biting habits- anthropophilic (manbiting)- outdoor/indoornight biting mosquitoesKeys/charts used for species identificationRests on walls – Indoor Residual SprayingEffective control method
  18. 18. Anopheles culicifaciesDistribution: Sri Lanka, India, MyanmarPakistan, Middle East, Nepal, ThailandAdult: small- mediumwings & female palps - bandingresting position culicine-likeBreeding: shallow, sunlit, clear fresh waterEg. Edges of slow flowing streams/rivers;rain water collections in ground pools and pits
  19. 19. Dry zone: endemic speciespresent throughout year but highdensities with rains (NE monsoon Oct-Jan)Intermediate zone: seasonal breedingWet zone: not normally found but breedingoccur with failure of monsoons due topooling in river bedsFound up to 900 m heightDistribution in Sri LankaAnopheles culicifacies
  20. 20. Rain water collections in pits,construction sites, hoof printsin dry zoneStream/river bed pools;seepage pools atmargins of lakes,reservoirs;open irrigation canalmargins
  21. 21. Malaria vector breedingin quarry pitsKurunegala (NWP) andAnuradhapura (NCP)
  22. 22. Malaria vector breeding in Agro wellsMatale, Anuradhapura district
  23. 23. Wet zone-rock/sand river bed pools during droughtspooling below dams/barragesKotmal oya- below dam
  24. 24. malaria vector breeding downstream of dams-An. culicifacies
  25. 25. Below dam at Nilambe oyaIlagolla- malaria outbreakdue to mosquito vectorbreeding in rock pools
  26. 26. Culicines- 20 generaIn Sri Lanka > 115 species Culex Aedes Mansonia Armigeres
  27. 27. Culex quinquefasciatusVery common urban domestic mosquito throughoutSouth/SE Asia- vector of bancroftian filariasisSmall, brown, absence of markingsBreeding: eggs in rafts (75-100 eggs)highly polluted (organic matter) stagnant watereg. blocked drains, cess pits, waste water pitsHabits: night biter, outdoor/indoorbites man, cats/dogsRests in shade eg. indoors in dark cornersclothes, under furniture etc.
  28. 28. Culex quinquefasciatus Biological vectorLymphatic filariasis:Microfilaria ingested with the blood meal develop intoInfective larvae L3 in 10-12 days and emerge fromproboscis during the biteONLY development NO multiplication
  29. 29. Breeding sites of Culex quinquefasciatusStagnant,polluted water(sewage)
  30. 30. Culex quinquefasciatus breeding sitesDirty water in blocked drains, cess pits etc.
  31. 31. Culex tritaeniorhynchusCx. gelidusCx. pseudovishnuiBreeding: paddy fields, marshes,husk-soakage pitsHabits: night, outdoor/indoorbites animals; pigs/cattle(zoophilic)Vectors of Japanese encephalitis
  32. 32. Japanese encephalitis:Epidemiological cyclePigs important amplifier hostsMosquito vectors:Cx. tritaeniorhyncus;Cx.pseudovishnui- paddyfield breedersCx. gelidus- muddy poolshusk pits
  33. 33. Japanese EncephalitisCulex gelidus
  34. 34. Vectors of Japanese encephalitis breed in paddy field
  35. 35. Aedes spp.Ae. aegypti Ae. albopictusSmall, delicate, black & white banding on legs.wings clearVectors of-Dengue fever, Chikungunya, Dirofilaria repensYellow fever (not in Sri Lanka)Breeding: eggs laid singly (no floats)damp surfaces that get submergedrain water collections in containers
  36. 36. Vectors ofDengue & ChickungunyaAedes aegyptiAe albopictusContainer breeders, clean waterartificial- tyres, tin cans, plastic wasteIndoors- flower vases etc.Natural- cut bamboo stumps, leaf axils
  37. 37. SL: dengue endemic since 1989Transovarian transmission of arbovirusesAedes breeding sites
  38. 38. Aedes breeding in householdsindoorsoutdoors
  39. 39. AedesBreedingoutdoors
  40. 40. Vector of Brugian filariasis& DirorfilariasisWater plants:PistiaEichorniaSalviniaMansonia spp.M uniformisM annuliferaBrown, speckled wings (light/dark scales)Breeding: aquatic plantseggs laid in clusters on undersurfaceleaves of water plantsLarvae/pupae attached to plant roots
  41. 41. Armigeres subalbatusVery common dusk/night biterPest & vector of Dirofilaria repensBreeding: polluted waterDirofilariasisDirofilaria repens: commonparasite of dogstransmittedby Aedes,Armigeres,MansoniaCauses subcutaneousnodules in humans
  42. 42. Reduce mosquito densityPathogen control in humansPrevent man-mosquito contactControl of mosquito borne diseases
  43. 43. Reduce vector density 1Adult control – Malaria control(1) Insecticide impregnatedbed nets – treat every 6/12(2) Indoor Residual Spraying
  44. 44. Reduce vector density 2Eliminate breeding sitesDestroy larvaeAedes spp.• Properly dispose of old tires, cans, bottles,water-collecting rubbish, and otherunused/unwanted containers.• Eliminate breeding in standing pools of waterEg. air conditioners, refrigerators – add surfaceoil layer• Clean birdbaths, vases, plant pots, rainbarrels, kiddie pools etc. ONCE A WEEK
  45. 45. SummaryMosquitoes ofMedical ImportanceAedesAnopheles culicfaciesCulex