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MOSQUITOES

MOSQUITOES. 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. HISTORY. Ancient Rome Scotland Middle ages and Henry II

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MOSQUITOES

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  1. MOSQUITOES 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

  2. HISTORY • Ancient Rome • Scotland • Middle ages and Henry II • Ancient India and Mesopotamia • Ancient China • Egypt • Alexander the Great 323 B.C. • Genghis Khan and Western Europe

  3. Alexander TheGreat • General, King, Ruler • Babylon 323 B.C. • Malaria? • WNV? • Typhoid?

  4. European Exploration • European exploration of new lands. • Defensive and Offensive diseases. • Offensive germs in the New World. • Indigenous destruction • Slave trade • 1890’s and beyond…

  5. The Family Culicidae - Mosquitoes • Worldwide distribution • > 3450 species and subspecies (38 genera) • Great habitat diversity • Approximately 40 million years older than humans (fossils from Eocene, 38-54 mya) • Anophelinae (subfamily) - Anopheles (genus) • Culicinae (subfamily) - Aedes, Culex, Haemagogus, Mansonia, Ochlerotatus and all other genera

  6. Mosquito Characteristics • Conspicuous proboscis - forward projecting • Scales on thorax, abdomen, legs & wing veins • A fringe of scales along the posterior margin of the wings

  7. Mosquito Characteristics (note conspicuous forward projecting proboscis) Non-biting Gnat (note proboscis curved under head) Mosquito Gnat

  8. Bloodfeeding - only females take blood Males and females feed on plant sugars Gonotrophic cycle - feed, egg development, oviposition (half-gravid, gravid) Egg biology - oviposition location, type of egg, desiccation resistance, diapause Larval biology - aquatic, spiracle for breathing, filter-feeders, some cannibalistic, variable habitats Mosquito Characteristics

  9. (1) Eggs – 3 strategies • Singly on water surface • Anopheles • Singly in a pile, on moist substrates • Aedes/Ochlerotatus • Form of a raft, on water surface • Culex • Culiseta

  10. Mosquito eggs: Culex egg raft Anopheles egg with ‘floats’ Aedes egg Patterns on the external egg surface are species specific

  11. Egg stage comparison

  12. CULEX Egg Raft

  13. (2) Embryonation – 2 options • Eggs hatch immediately (not all) • OR • Diapause required • Triggered by decreasing day length. • **Egg stage over wintering stage** • Aedes/Ochlerotatus

  14. (3) Larval Stage – Growth Stage • Larval instars (4) • Aquatic, Filter feeders • Respiration Anopheles

  15. (4) Pupa – Lighter than water • Non-feeding • Respiration Pupal Stage Comparison Anopheline Culicine

  16. Mosquito Pupa and Larvae

  17. Anopheles Pupa and Larvae

  18. Mosquito Emerging from Pupal Exuvia

  19. (5) Adults • Emergence • Mating • Feeding Adult Stage Comparison Anopheline Culicine

  20. females Comparison of male and female Anophelines vs. Culicines Culicine Anopheline males

  21. Behavior • Activity • Host Specificity • Zoophilous • Anthropophilous • Ornithophilous

  22. HABITAT

  23. Medical Importance • Biting Nuisance (annoyance) • Arboviruses • Numerous (Yellow Fever, Dengue Fever, WNV, JE, SLE, EEE, WEE, VEE). • Filariasis • Bancroftian and Brugian filariasis. • Malaria • 4 plasmodium species

  24. Malaria History • Ronald Ross (1897) • Malaria Eradication? • Between 350 and 500 million clinical episodes of malaria occur every year. • 1-2 million deaths occur every year. • About 60% of the cases of malaria worldwide and more than 80% of the malaria deaths worldwide occur in Africa south of the Sahara.

  25. HUMAN MALARIA • Parasite – Plasmodium spp. • P. falciparum, P. vivax, P. malaria, P. ovale • Vector – Anopheles spp. • Host • Reservoir • Distribution

  26. Anopheles gambiae WHO/TDR/HOLT Studios, 1992

  27. Global Distribution

  28. Distribution • Distribution Model

  29. Distribution • Endemic / Epidemic Risk Areas

  30. Distribution • Duration of Malaria Transmission Season.

  31. Distribution Start / End of Transmission Season

  32. Distribution • Population Distribution

  33. Filariasis History • Patrick Manson (1877) • Worked in Taiwan • Autopsies in China • Threadlike worms • “Nothing walks with aimless feet.:”

  34. Mosquito-Borne Human Filariasis • 250 million infections each year • 2-3 million cases of obstructive filariasis • 20% of pop in Calcutta infected • 2 diseases that affect humans • Urban Disease • Rural Disease

  35. Urban and Rural Disease • Urban Disease (Bancroftian filariasis) • Parasite – • An anthroponosis • Bancroftia • Rural Disease (Brugian filariasis) • Parasite – • An anthroponosis or zoonosis • Brugian

  36. Transmission • (1) Microfilariae in blood. • (2) • (3) Microfil. Penetrate midgut  thoracic muscles. • (4) • (5) Enter new host.

  37. Periodicity • (1) Periodic Infection • (2) Subperiodic Infection

  38. VECTORS • (1) Bancroftian Filariasis • Cx. pipiens quinquefasciatis • Cx. pipiens pipiens • Anopheles spp. • Aedes spp. • (2) Brugian Filariasis • Anopheles spp. • Aedes spp. • Mansonia (genus)

  39. DISTRIBUTION • Tropics and subtropics • Wuchereria bancrofti is encountered in _________________. • Brugia malayi is limited to _____. • Dog Heartworm (Dirofilaria immitis, D. repens)

  40. Mosquito Arboviruses • Intrinsic incubation period of a virus in humans is a few days. • Host becomes viraemic. • Viraemia lasts typically 3 days then disappears from the peripheral blood. • An arthropod must bite a viraemic host if it is to become infected.

  41. Yellow Fever History

  42. Yellow Fever • Brought to U.S. via slave trade. • Aedes aegypti • Originally in New World Monkey populations • Jungle Yellow fever (3-factor disease in monkeys) • New World people bring to town • Old World mooting monkeys bring to town. • Does occasionally occur in U.S. • 1964 Eradication program (U.S. Public Health)

  43. YELLOW FEVER • Is a _______ • Prevented the building of the Panama Canal. • Pathogen: • Vector: Aedes aegypti, Aedes spp., Haemagogus • Host:

  44. Reservoir • Human-mosquito in urban cycle, • Monkey-mosquito in forest cycle; • Deforestation may force infected monkeys into areas where human-mosquito transmission can occur.

  45. African Yellow Fever Transmission Cycle Vectors: • Ae. Africanus (sylvatic) • Ae. Bromeliae (rural) • Ae. Aegypti (urban) • Transovarial Transmission

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