1. Protecting Yourself from Mosquito-borne Infections: West Nile Virus Dr. Richard M. Houseman Department of Entomology University of Missouri

2. “When unable to defend herself by the sword, Rome could defend herself by means of the fever.” Godfrey of Viterbo, 1167

4. Mosquito-Borne Infections FilariaFilaria –Heartworm –Elephantiasis ProtozoaProtozoa –Malaria VirusVirus –Yellow Fever –Dengue –SLE, WEE, WNV

5. West Nile Virus Encephalitis-type virus identified in Uganda (1937)Encephalitis-type virus identified in Uganda (1937) Commonly found in humans and birds throughout much of the worldCommonly found in humans and birds throughout much of the world –Historically Europe, Africa, Middle East. Has been in North America since 1999Has been in North America since 1999 –First found in New York City –Now permanently established in Western Hemisphere

10. Human WNV Reports in 2003

12. West Nile Virus Symptoms Most human infections have none or mild symptoms (West Nile Fever)Most human infections have none or mild symptoms (West Nile Fever) –Recovery in >99% of cases –No long-term effects <1% with symptoms develop encephalitis<1% with symptoms develop encephalitis –Disorientation, weakness, paralysis, coma Hospitalization for support therapyHospitalization for support therapy –Intravenous fluids, ventilator, monitoring

13. West Nile Virus Transmission Birds are primary hosts, others are incidentalBirds are primary hosts, others are incidental –Human infections are rare In temperate areas (24º-66º latitude) virus transmission is seasonalIn temperate areas (24º-66º latitude) virus transmission is seasonal –Summer to early fall –Cases appear 3-4 weeks following infection

14. 140 species Dogs, cats, bats, squirrels, skunks, chipmunks, rabbits 20 species

15. Mosquito Vectors of WNV Of the ~20 known vector species…Of the ~20 known vector species… –14 have been collected in Missouri –12 are found in all areas of the state –8 are common or abundant –7 inhabit temporary/human-created water –7 inhabit permanent water –7 bite at dawn/dusk –5 overwinter as fertilized females

16. All mosquitoes are not created equal Different habitat preferencesDifferent habitat preferences –Water conditions –Activity periods Different movement patternsDifferent movement patterns Different host preferencesDifferent host preferences –Warm-blooded –Different groups

17. ‘Urban’ Mosquitoes Breeding occurs and hosts available in human-dominated environmentsBreeding occurs and hosts available in human-dominated environments Important urban speciesImportant urban species Culex pipiens (common house) Aedes aegypti (yellow fever) Aedes albopictus (Asian tiger)

18. ‘Suburban’ Mosquitoes Breed in non-human-dominated environments and move to locate hostsBreed in non-human-dominated environments and move to locate hosts –Highly vagile adults (ie. up to 17 miles) Important urban ‘invading’ speciesImportant urban ‘invading’ species Culex tarsalis (western encephalitis) Aedes vexans (inland floodwater)

19. ‘Rural’ Mosquitoes Breed in non-human-dominated environments and feed to a lesser extent on man.Breed in non-human-dominated environments and feed to a lesser extent on man. –Less vagile (ie. <1 mile) Important rural speciesImportant rural species –Anopheles quadrimaculatus (eastern malaria)

20. Life Cycle of Mosquitoes WaterWater –Eggs, larvae, pupae LandscapeLandscape –Adults HostHost –Adults Back to WaterBack to Water –Adults egg adult pupa larva

21. In the Water Standing waterStanding water –Pollution –Decaying organic matter –Emergent vegetation (intersection line) Containers, puddles, drains, etc.Containers, puddles, drains, etc. –Small or large amounts of water –Decaying organic matter for hatching/feeding

23. In the Water Eggs (2d)Eggs (2d) –Oviposition, hatching, breathing system Larvae (10d)Larvae (10d) –Feed actively, breathing, mobility Pupae (2d)Pupae (2d) –Non-feeding, breathing, mobility

25. In the Water Feeding on microbes and small nematodesFeeding on microbes and small nematodes High mortality ratesHigh mortality rates –No fish in temporary and/or filthy water –Cannibalistic mosquitoes (Toxorhynchites)(Toxorhynchites) –Predaceous insects (Gyrinidae, Dytiscidae, Gerridae, Notonectidae)(Gyrinidae, Dytiscidae, Gerridae, Notonectidae)

26. In the Landscape Protected locations that minimize dryingProtected locations that minimize drying Vertical surfaces used frequentlyVertical surfaces used frequently LandmarksLandmarks –Near water –Often used by multiple generations, year after year

28. In the Landscape Development continues (2d)Development continues (2d) –Cuticle hardening, sexual development FeedingFeeding –plant nectars and honeydew –Blood Resting and digestingResting and digesting

29. In the Landscape MatingMating –Swarming and copulation Avoiding predatorsAvoiding predators –dragonflies, ants, lizards, and bats

30. On the Host Mostly warm-blooded vertebratesMostly warm-blooded vertebrates –Host preferences vary Carbon dioxide, lactic acid, body heat signalsCarbon dioxide, lactic acid, body heat signals Activity/biting period variesActivity/biting period varies –Sleeping or active host

32. On the Host Locating a hostLocating a host –movement, chemical/temperature stimuli FeedingFeeding –Probing for arterioles, venules –Salivating and sucking Getting awayGetting away

33. Back to the Water Resting and DigestingResting and Digesting –Humid, protected locations –Predator avoidance ExcretionExcretion –Peritrophic membrane surrounds meal –Elimination of liquid portion of blood

34. Back to the Water Survival to reproduction almost a miracleSurvival to reproduction almost a miracle Locating oviposition sitesLocating oviposition sites –Visual and olfactory –Fermenting stimuli of nutrient-rich water One clutch of eggs most commonOne clutch of eggs most common –Two, or even three rarely Death from various causesDeath from various causes

35. “If you would see all of nature gathered up at one point, in all her loveliness, and her skill, and her deadliness, and her sex, where would you find a more exquisite symbol than the mosquito?” Havelock Ellis, 1920

36. Missouri WNV Update 2002 Reports2002 Reports –169 human cases in 29 counties Age ranged from 4-92 yearsAge ranged from 4-92 years Attack rate of 3 per 100,000 (0. 003%)Attack rate of 3 per 100,000 (0. 003%) –5 human fatalities Age ranged from 61-88 yearsAge ranged from 61-88 years –819 horses in 103 counties –277 birds in 82 counties 2003 Reports –61 human cases in 25 counties Age ranged from 6-85 years Attack rate of ~1 per 100,000 (0. 001%) –6 human fatalities Age ranged from 69-83 years –130 horses in 53 counties –144 birds in 54 counties

37. Human WNV in Missouri

40. ILMO AR TN KY NE IA KS OK

41. Avian WNV in U.S. 20022003

42. Minimizing the Risk of WNV Avoid mosquito bitesAvoid mosquito bites –Reduce mosquito populations –Personal Protective measures

43. Minimizing the Risk of WNV Reducing Mosquito PopulationsReducing Mosquito Populations –Eliminate temporary mosquito breeding habitats Regular surveillanceRegular surveillance Empty containers and clutterEmpty containers and clutter –Monitor permanent breeding habitats ‘dip’ counts‘dip’ counts rising and receding waterrising and receding water Insecticide or oil application when presentInsecticide or oil application when present

44. Minimizing the Risk of WNV Personal Protective MeasuresPersonal Protective Measures –Limit outdoor activity during peak bite times Dawn, duskDawn, dusk Prevent mosquitoes from coming indoorsPrevent mosquitoes from coming indoors –Wear long-sleeved shirts, long pants Permethrin or DEET may be appliedPermethrin or DEET may be applied –Apply insect repellent containing DEET –Possible vaccine

45. MU Extension Resources